Dr.-Ing. Christoph Held

Thermodynamics
TU Dortmund University

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  • ePC-SAFT advanced - Part I: Physical meaning of including a concentration-dependent dielectric constant in the born term and in the Debye-Hückel theory
    Bülow, M. and Ascani, M. and Held, C.
    Fluid Phase Equilibria 535 (2021)
    The transition from aqueous electrolyte systems to non-aqueous electrolyte systems is highly demanded in industrial applications and especially challenging for physics-based thermodynamic models. Electrolyte thermodynamics is a complex matter, and still not all physico-chemical effects are accounted for in state-of-the-art equations of state. The dielectric constant of non-aqueous electrolyte systems changes drastically compared to aqueous systems. One main consequence is that ions are very differently solvated in non-aqueous medium compared to aqueous medium. The Born term represents a methodology to account for the influence of solvation energies of ions, which is based on influences of solvent and salt on the dielectric constant. Utilizing the Born term in electrolyte models is extensively debated, and it is often reasonably neglected in predominantly aqueous systems. Yet, it has a significant influence on transferability from aqueous to non-aqueous media i.e., systems with a large difference in polarity or permittivity compared to aqueous systems. In this work, a modified Born term was combined with electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) by introducing additionally a salt concentration-dependent dielectric constant, henceforth called altered Born contribution. The new methodology was validated against infinite dilution properties for ion-solvent interactions: Gibbs energy of hydration and Gibbs energy of transfer of alkali halides from water to alcoholic solvents. Further, mean ionic activity coefficients (MIACs) of alkali halides in alcoholic solvents were quantitatively correct predicted with the advanced ePC-SAFT approach. Original ePC-SAFT parameters were applied for all predictions, and no further binary parameters were adjusted. Based on the success of the model predictions, the transferability of pure-ion ePC-SAFT parameters to organic solvents was verified and the incorporation of concentration-dependent dielectric constant into the altered Born contribution and Debye-Hückel theory was proven to be meaningful methods for the transfer of electrolyte thermodynamic models from aqueous to non-aqueous systems. © 2021 Elsevier B.V.
    view abstract10.1016/j.fluid.2021.112967
  • ePC-SAFT advanced – Part II: Application to Salt Solubility in Ionic and Organic Solvents and the Impact of Ion Pairing
    Bülow, M. and Ascani, M. and Held, C.
    Fluid Phase Equilibria 537 (2021)
    The applications of electrolyte thermodynamic models to non-aqueous systems is of great value to reduce experimental effort and gain inside into molecular interactions. A large-scale application is for example the design of advanced battery electrolytes. For non-aqueous electrolyte systems, the Born term was found to be important, as it accounts for the transfer of ions from water into non-aqueous medium. In part one of this study [Bülow et al., Fluid Phase Equilibria 2021, 112967] the Born term was combined with a concentration-dependent dielectric constant within the ePC-SAFT framework (electrolyte Perturbed-Chain Statistical Associating Fluid Theory). In the present work, the Bjerrum treatment for ion pairing was included in the Debye-Hückel framework within ePC-SAFT. The approach was validated by experimental data for the dissociation of salts in organic solvents derived from conductivity measurements. Further, solubility was modeled of alkali halides in organic solvents and in ionic liquids. Modeling solubility required access to the solubility product KSP, which does not depend on the solvent. The approach within this work was to first determine KSP using experimental solubility data in water and the respective ePC-SAFT predicted activity coefficients prior to predict activity coefficients in non-aqueous medium, finally yielding solubility. The so-determined solubility values were found to be in reasonable agreement with the experimental data without fitting model parameters to any data of the non-aqueous solutions. The solubility product requires the solid form of the precipitating salt to be equal for all solvents; as alkali salts precipitate from aqueous solutions as hydrates, the method cannot be applied. Therefore, a methodology is presented to extrapolate the high-temperature KSP of anhydrates to lower temperature. Using the so-extrapolated KSP allowed predicting solubility of non-solvates in other solvents. © 2021 Elsevier B.V.
    view abstract10.1016/j.fluid.2021.112989
  • Extremely Low Vapor-Pressure Data as Access to PC-SAFT Parameter Estimation for Ionic Liquids and Modeling of Precursor Solubility in Ionic Liquids
    Bülow, M. and Greive, M. and Zaitsau, D.H. and Verevkin, S.P. and Held, C.
    ChemistryOpen (2021)
    Precursor solubility is a crucial factor in industrial applications, dominating the outcome of reactions and purification steps. The outcome and success of thermodynamic modelling of this industrially important property with equations of states, such as Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), vastly depends on the quality of the pure-component parameters. The pure-component parameters for low-volatile compounds such as ionic liquids (ILs) have been commonly estimated using mixture properties, e. g. the osmotic pressure of aqueous solutions. This leads to parameters that depend on the solvent, and transferability to other mixtures often causes poor modeling results. Mixture-independent experimental properties would be a more suitable basis for the parameter estimation offering a way to universal parameter sets. Model parameters for ILs are available in the literature [10.1016/j.fluid.2012.05.029], but they were estimated using pure-IL density data. The present work focuses on a step towards a more universal estimation strategy that includes new experimental vapor-pressure data of the pure IL. ILs exhibit an almost negligible vapor pressure in magnitude of usually 10−5 Pa even at elevated temperatures. In this work, such vapor-pressure data of a series of 1-ethyl-3-methyl-imidazolium-based [C2mim]-ILs with various IL-anions (e. g. tetrafluoroborate [BF4]−, hexafluorophosphate [PF6]−, bis(trifluoromethylsulfonyl)imide [NTf2]−) were experimentally determined and subsequently used for PC-SAFT parameter estimation. The so-determined parameters were used to predict experimental molecular precursor solubility in ILs and infinitely diluted activity coefficients of various solvents in ILs. The parameters were further compared to modeling results using classical parametrization methods (use of liquid-density data only for the molecular PC-SAFT and the ion-based electrolyte PC-SAFT). As a result, the modeled precursor solubilities using the new approach are much more precise than using the classical parametrization methods, and required binary parameters were found to be much smaller (if needed). In sum, including the pure-component vapor-pressure data of ILs opens the door towards parameter estimation that is not biased by mixture data. This procedure might be suitable also for polymers and for all kind of ionic species but needs extension to ion-specific parametrization in the long term. © 2021 The Authors. Published by Wiley-VCH GmbH
    view abstract10.1002/open.202000258
  • From volatility to solubility: Thermodynamics of imidazolium-based ionic liquids containing chloride and bromide anions
    Zaitsau, D.H. and Siewert, R. and Pimerzin, A.A. and Bülow, M. and Held, C. and Loor, M. and Schulz, S. and Verevkin, S.P.
    Journal of Molecular Liquids 323 (2021)
    Ionic liquids (ILs) are effectively used for tuning the composition and the morphology of nanoparticles or stabilizing agents for nanoparticles for catalytic dehydrogenation. Thermodynamic properties of ionic liquids, e.g. vapor pressures and vaporization enthalpies help optimise these processes. Vapor pressures and vaporization enthalpies of the series of 1-alkyl-3-methylimidazolium ionic liquids with chloride and bromide anions have been measured by using quartz-crystal microbalance (QCM). Possible thermal decomposition pathways of [C2C1Im][Br] during vaporization were analyzed by using high-level quantum-chemical methods. These theoretical results explained and supported the absence of decomposition in QCM experimental conditions. According to the measured vapor pressures the [CnC1Im][Cl] and [CnC1Im][Br] series are very suitable for catalytic applications, taking also into account their sufficient thermal stability at the level of 523–543 K. Solubility parameters of ILs and practically relevant solutes were assessed with help of experimental vaporization enthalpies. © 2020 Elsevier B.V.
    view abstract10.1016/j.molliq.2020.114998
  • Measurement and modelling solubility of amino acids and peptides in aqueous 2-propanol solutions
    Do, H.T. and Franke, P. and Volpert, S. and Klinksiek, M. and Thome, M. and Held, C.
    Physical Chemistry Chemical Physics 23 (2021)
    Amino acids and peptides are essential components in the biochemical industry. The final products are employed in a wide range of applications and are often synthesized by fermentation and purified in a complex downstream process. One possible separation step is using an additional solvent to lower the solubility of the desired product and, thus, promote the crystallization of the particular component. Therefore, it is crucial to have accurate knowledge of the solubility of these components. In this work, the solubilities of 20 proteinogenic amino acids and 21 peptides in aqueous 2-propanol solutions were gravimetrically determined. Additionally, the pH values of the saturated liquid phases were measured and the crystal structures of solid crystals were analysed using X-ray diffraction. The anti-solvent 2-propanol caused a decrease in the solubilities of the amino acids and peptides upon increasing its mass fraction. Exceptions were found for amino acids with aromatic substituents, l-phenylalanine and l-tyrosine. The solubility of 15 amino acids and 18 peptides was successfully modelled using the equation of state PC-SAFT that used recently determined melting properties of the amino acids and peptides as input data. This journal is © the Owner Societies.
    view abstract10.1039/d1cp00005e
  • Measurement and PC-SAFT Modeling of the Solubility of Gallic Acid in Aqueous Mixtures of Deep Eutectic Solvents
    Sepúlveda-Orellana, B. and Gajardo-Parra, N.F. and Do, H.T. and Pérez-Correa, J.R. and Held, C. and Sadowski, G. and Canales, R.I.
    Journal of Chemical and Engineering Data (2021)
    Deep eutectic solvents have appeared as potential solvents for improving the extraction of polyphenols from vegetable or fruit matrixes. Since gallic acid is abundant in these sources, it is considered as a typical standard for quantifying their total polyphenol content after extraction with solvents. However, there are no extensive studies on the solubility behavior of gallic acid in different solvents or deep eutectic solvents. Thus, in this work, the solubility of gallic acid is measured in pure water; aqueous solutions of different hydrogen bond donors such as ethylene glycol, levulinic acid, and glycerol; and aqueous mixtures of deep eutectic solvents using choline chloride as the hydrogen bond acceptor and ethylene glycol, levulinic acid, and glycerol as the hydrogen bond donors. All of the measurements were performed at 293.15, 303.15, and 313.15 K and at 101.3 kPa and were validated by comparing the solubility of gallic acid in water from the literature. Results suggest that a 50 wt % aqueous solution of deep eutectic solvent based on ethylene glycol or glycerol improves the gallic acid solubility compared with a 50 wt % aqueous solution of its corresponding hydrogen bond donor. The deep eutectic solvent containing levulinic acid acts as the best aqueous mixture for gallic acid dissolution. Nondissolved gallic acid was measured after equilibrium using powder X-ray diffraction, showing that its structure does not change upon mixing with all of the liquid mixtures. All of the solid-liquid equilibrium results were accurately modeled with perturbed-chain statistical associating fluid theory (PC-SAFT). © 2021 American Chemical Society.
    view abstract10.1021/acs.jced.0c00784
  • Melting Properties of Peptides and Their Solubility in Water. Part 2: Di- And Tripeptides Based on Glycine, Alanine, Leucine, Proline, and Serine
    Do, H.T. and Chua, Y.Z. and Habicht, J. and Klinksiek, M. and Volpert, S. and Hallermann, M. and Thome, M. and Pabsch, D. and Zaitsau, D. and Schick, C. and Held, C.
    Industrial and Engineering Chemistry Research 60 (2021)
    In downstream processes for peptides, crystallization is still used as the state-of-the-art separation step for which the knowledge about the solubility of each single compound is mandatory. Since the determination of experimental temperature-dependent solubility data is time-consuming and expensive, modeling solubility based on physical properties such as melting properties is highly desired. Unfortunately, the direct determination of melting properties for biomolecules using conventional differential scanning calorimetry is not possible due to the decomposition of the peptides before their melting. In this work, fast scanning calorimetry (FSC) with heating rates up to 20,000 K s-1 was applied to measure the melting properties of 22 peptides with focus on isomeric dipeptides and tripeptides based on glycine, l-alanine, l-leucine, l-proline, and l-serine. The experimental determination of the aqueous solubility of these peptides was performed using the photometric method (UV/Vis spectrometer) and the gravimetric method of supersaturated solutions. Additionally, the pH value and the crystal structure of peptides were determined in order to ensure the neutral species in solution and to exclude crystal structure changes in the solid phase. The experimental FSC-measured melting properties were used as input data in the thermodynamic modeling framework PC-SAFT to model the peptide solubility in water. The PC-SAFT pure-component parameters of the peptides were determined following a weighted joint-parameter method introduced in this work. This approach allows determining the pure-component parameters of a peptide by joining the pure-component parameters of the parent amino acids. The binary interactions parameter between peptide and water was fitted to solubility-independent properties such as osmotic coefficients and mixture densities of aqueous peptide solutions. The modeled peptide solubility was in good agreement with the experimental solubility. © 2021 American Chemical Society. All rights reserved.
    view abstract10.1021/acs.iecr.0c05652
  • Modeling interfacial properties of ionic liquids with ePC-SAFT combined with density gradient theory
    Sun, Y. and Zuo, Z. and Shen, G. and Held, C. and Lu, X. and Ji, X.
    Fluid Phase Equilibria 536 (2021)
    In this work, ePC-SAFT-DGT (i.e., the coupling of ePC-SAFT with the density gradient theory (DGT)) was further developed by modifying the expression for estimating the chemical potential of IL ion-pair and extended to study the interfacial properties of 82 ionic liquids (ILs) containing one of the IL-cations ([Cnmim]+, [Cnpy]+, [Cnmpy]+, [Cnmpyr]+, and [THTDP]+) and one of the IL-anions ([Tf2N]−, [PF6]−, [BF4]−, [tfo]−, [DCA]−, [SCN]−, [C1SO4]−, [C2SO4]−, [eFAP]−, Cl−, [Ac]−, and Br−). The available experimental surface tensions for these 82 ILs from the literature have been surveyed and evaluated for adjusting the model parameters before the investigation. It shows that the modification results in more reasonable magnitude of influence parameters and ePC-SAFT-DGT can be used to represent the surface tension of ILs reliably compared with the experimental data. Furthermore, using the anion-specific influence parameters that are linearized with the molecular weight of the IL-cations for a homologous series of ILs allows semi-predicting (i.e., parameters obtained by interpolation and extrapolation) the surface tension for the ILs in the same homologous series. ePC-SAFT-DGT can be further used to predict other interfacial properties, for example, the density profile and interfacial thickness in the vapor-liquid interface. © 2021
    view abstract10.1016/j.fluid.2021.112984
  • Modeling solubility of amino acids and peptides in water and in water+2-propanol mixtures: PC-SAFT vs. gE models
    Do, H.T. and Chakrabarty, S. and Held, C.
    Fluid Phase Equilibria 542-543 (2021)
    Amino acids and peptides are essential components for many industrial branches. Knowledge on the solubility behavior is required in purification processes, which often involve crystallization as main unit operation. Since the determination of experimental solubility data is expensive, thermodynamic modeling is meaningful towards reducing the experimental effort. Modeling is usually based on a solid-liquid equilibrium condition that requires the melting properties of the solids. For amino acids and peptides such data is now available, and three gE models (Wilson, NRTL, UNIQUAC) were applied in this work to model solubility in water as well as in water + 2-propanol. The new melting properties were used as input data and binary parameters for each model were fitted to experimental solubility data of the amino acids and peptides in water. Modeling solubility in water + 2-propanol required additional parameters. Binary parameters between water and 2-propanol were fitted to vapor-liquid-equilibrium data, and binary parameters between amino acid and 2-propanol as well as between peptide and 2-propanol were fitted to solubility data in water + 2-propanol mixtures. In general, the gE models allowed describing the solubility in water, while some inaccuracies were observed for the temperature dependence of the modeled solubility. Further, the decrease of solubility upon 2-propanol addition was modeled qualitatively correct using the gE models. The Wilson model was less accurate than NRTL and UNIQUAC, where the latter yielded similar results. The results were finally compared to PC-SAFT, which shows a dramatically improved modeling accuracy while using less binary parameters. © 2021
    view abstract10.1016/j.fluid.2021.113087
  • New thermodynamic activity-based approach allows predicting the feasibility of glycolysis
    Greinert, T. and Vogel, K. and Maskow, T. and Held, C.
    Scientific Reports 11 (2021)
    Thermodynamic feasibility analyses help evaluating the feasibility of metabolic pathways. This is an important information used to develop new biotechnological processes and to understand metabolic processes in cells. However, literature standard data are uncertain for most biochemical reactions yielding wrong statements concerning their feasibility. In this article we present activity-based equilibrium constants for all the ten glycolytic reactions, accompanied by the standard reaction data (standard Gibbs energy of reaction and standard enthalpy of reaction). We further developed a thermodynamic activity-based approach that allows to correctly determine the feasibility of glycolysis under different chosen conditions. The results show for the first time that the feasibility of glycolysis can be explained by thermodynamics only if (1) correct standard data are used and if (2) the conditions in the cell at non-equilibrium states are accounted for in the analyses. The results here will help to determine the feasibility of other metabolisms and to understand metabolic processes in cells in the future. © 2021, The Author(s).
    view abstract10.1038/s41598-021-85594-8
  • Perspective: Increasing blue carbon around Antarctica is an ecosystem service of considerable societal and economic value worth protecting
    Bax, N. and Sands, C.J. and Gogarty, B. and Downey, R.V. and Moreau, C.V.E. and Moreno, B. and Held, C. and Paulsen, M.L. and McGee, J. and Haward, M. and Barnes, D.K.A.
    Global Change Biology 27 (2021)
    Precautionary conservation and cooperative global governance are needed to protect Antarctic blue carbon: the world's largest increasing natural form of carbon storage with high sequestration potential. As patterns of ice loss around Antarctica become more uniform, there is an underlying increase in carbon capture-to-storage-to-sequestration on the seafloor. The amount of carbon captured per unit area is increasing and the area available to blue carbon is also increasing. Carbon sequestration could further increase under moderate (+1°C) ocean warming, contrary to decreasing global blue carbon stocks elsewhere. For example, in warmer waters, mangroves and seagrasses are in decline and benthic organisms are close to their physiological limits, so a 1°C increase in water temperature could push them above their thermal tolerance (e.g. bleaching of coral reefs). In contrast, on the basis of past change and current research, we expect that Antarctic blue carbon could increase by orders of magnitude. The Antarctic seafloor is biophysically unique and the site of carbon sequestration, the benthos, faces less anthropogenic disturbance than any other ocean continental shelf environment. This isolation imparts both vulnerability to change, and an avenue to conserve one of the world's last biodiversity refuges. In economic terms, the value of Antarctic blue carbon is estimated at between £0.65 and £1.76 billion (~2.27 billion USD) for sequestered carbon in the benthos around the continental shelf. To balance biodiversity protection against society's economic objectives, this paper builds on a proposal incentivising protection by building a ‘non-market framework’ via the 2015 Paris Agreement to the United Nations Framework Convention on Climate Change. This could be connected and coordinated through the Antarctic Treaty System to promote and motivate member states to value Antarctic blue carbon and maintain scientific integrity and conservation for the positive societal values ingrained in the Antarctic Treaty System. © 2020 John Wiley & Sons Ltd
    view abstract10.1111/gcb.15392
  • Predicting vapor−liquid equilibria for sour-gas absorption in aqueous mixtures of chemical and physical solvents or ionic liquids with EPC-SAFT
    Bülow, M. and Ince, N.G. and Hirohama, S. and Sadowski, G. and Held, C.
    Industrial and Engineering Chemistry Research 60 (2021)
    Sour-gas absorption is the main unit operation used in refineries and petrochemical and natural gas processing plants for the effective reduction of climate-wrecking gases, mainly CO2 and H2S. Absorption is typically accomplished in an aqueous solvent mixture. The solvent mixture is vastly dependent on the application range; it might contain chemical solvents (amines), activators, and physical solvents. In this work, the vapor−liquid equilibria for absorption of the sour gases CO2 and H2S was investigated in systems containing the chemical solvent methyl diethanolamine (MDEA) and the physical solvents tetrahydrothiophene-1,1-dioxide (sulfolane) or the ionic liquid 1-butyl-3-methylimidazolium acetate. The solubilities of CO2 and H2S were predicted and validated using experimental literature data in a broad range of temperature (313−373 K), sour-gas loading (up to 2 moles gas per moles of MDEA), and pressure (up to 180 bar) at constant MDEA weight fraction (20.9 wt %) and sulfolane weight fraction (30.5 wt %). The equation-of-state electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) was utilized in this work for the predictions combined with the Born term to physically correctly describe the Gibbs energy of solvation of ions in the aqueous mixture of chemical and physical solvents; this was introduced in a recent work [Bülow, M. et al. Fluid Phase Equilib. 2021, 535, 112967]. Using this approach allowed reducing the total number of binary interaction parameters in these systems of maximum 11 species to a minimum; these parameters were fitted exclusively to data of binary mixtures. The ePC-SAFT predictions of the gas solubility were most accurate at low sour-gas loadings and high temperatures. This work provides a thermodynamic framework for the solvent selection for sour-gas absorption in a broad range of conditions. This enables a realistic decrease in experimental effort for solvent selection in sour-gas absorption. © 2021 American Chemical Society
    view abstract10.1021/acs.iecr.1c00176
  • Prediction of salting-out in liquid-liquid two-phase systems with ePC-SAFT: Effect of the Born term and of a concentration-dependent dielectric constant
    Ascani, M. and Held, C.
    Zeitschrift fur Anorganische und Allgemeine Chemie 647 (2021)
    Knowledge on phase equilibria is of crucial importance in designing industrial processes. However, modeling phase equilibria in liquid-liquid two-phase systems (LLTPS) containing electrolytes is still a challenge for electrolyte thermodynamic models and modeling still requires a lot of experimental input data. Further, modeling electrolyte solutions requires accounting for different physical effects in the electrolyte theory, especially the change of the dielectric properties of the medium at different compositions and the related change of solvation free energy of the dissolved ions. In a previous work, the Born term was altered by combining it with a concentration-dependent dielectric constant within the framework of electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT), and hence called ‘ePC-SAFT advanced’. In the present work, ePC-SAFT advanced was validated against liquid-liquid equilibria (LLE) of LLTPS water+organic solvents+alkali halides as well as aqueous two-phase systems containing the phase formers poly (propylene glycol) and an ionic liquid. All the ePC-SAFT parameters were used as published in the literature, and each binary interaction parameter between ion-solvent was set to zero. ePC-SAFT advanced allowed quantitatively predicting the salt effect on LLTPS without adjusting binary interaction parameters, while classical ePC-SAFT or meaningless mixing rules for the dielectric constant term failed in predicting the phase behavior of the LLTPS. © 2021 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH
    view abstract10.1002/zaac.202100032
  • Solubility of DNP-amino acids and their partitioning in biodegradable ATPS: Experimental and ePC-SAFT modeling
    Wysoczanska, K. and Nierhauve, B. and Sadowski, G. and Macedo, E.A. and Held, C.
    Fluid Phase Equilibria 527 (2021)
    Predicting the behavior of dinitrophenylated amino acids (DNP-AA) in aqueous solutions requires an understanding and accurate description of interactions that can occur in such systems. In this work, some properties of DNP-AA (DNP-glycine, DNP-alanine, DNP-valine, DNP-leucine) have been determined experimentally. These were liquid densities obtained at T=298.15 – 318.15 K, p=1 bar, and pH-dependent solubility data measured at T=298.15 K, p=1 bar. It was observed that the solubility order for DNP-AA does not follow the same sequence as for aliphatic amino acids. The thermodynamic model ePC-SAFT has been applied to predict the properties density and solubility, and additionally to estimate partition coefficients of DNP-AA in PEG (PEG 4000, PEG 6000, PEG 8000) - organic salt (sodium citrate, potassium citrate, potassium sodium tartrate) aqueous two-phase systems (ATPS). ePC-SAFT pure-component and binary interaction parameters for neutral DNP-AA were acquired using the joinzt joint-parameter method, namely by combining the parameters for dinitrobenzene with parameters for amino acids (glycine, L-alanine, L-valine, L-leucine) from literature. The pure-component parameters for charged DNP-AA- were inherited from their parent neutral DNP-AA. This work shows that ePC-SAFT allows predicting liquid densities and solubilities of neutral DNP-AA with good agreement to experimental results. Moreover, adjusting in sum six binary parameters between charged DNP-AA- and phase-forming species allowed modeling partition coefficients of four DNP-AA in nine different PEG – organic salt ATPS, each at four different ATPS compositions. This can be considered an excellent modeling result and proofs the suitability of ePC-SAFT for such systems. © 2020 Elsevier B.V.
    view abstract10.1016/j.fluid.2020.112830
  • Solvent effect on the kinetics of the hydrogenation of n-butyl levulinate to γ-valerolactone
    Capecci, S. and Wang, Y. and Casson Moreno, V. and Held, C. and Leveneur, S.
    Chemical Engineering Science 231 (2021)
    The use of lignocellulosic biomass in the chemical industry can significantly contribute to respect the various international agreements on climate change. One of the most promising platform molecules issued from the lignocellulosic biomass hydrolysis is γ-valerolactone (GVL). GVL can be upgraded to valuable chemicals and produced by the hydrogenation of alkyl levulinates. Although these reactions are widely studied, seldom research focused on the solvent effect. To fill this gap, the effect of three different reaction mixtures with an excess of butyl levulinate (BL), of butanol and GVL was studied on the kinetics of BL hydrogenation to GVL over Ru/C. PC-SAFT (Perturbed-Chain Statistical Associating Fluid Theory) shows that the solubility of hydrogen is not constant during the reaction progress, and it was taken into account. To allow a fair comparison, kinetic models were developed using Bayesian statistics for each reaction mixture. The best performances were obtained when the reaction mixture has an excess of GVL. © 2020 Elsevier Ltd
    view abstract10.1016/j.ces.2020.116315
  • Unravelling the nature of citric acid:l-arginine:water mixtures: The bifunctional role of water
    Roda, A. and Santos, F. and Chua, Y.Z. and Kumar, A. and Do, H.T. and Paiva, A. and Duarte, A.R.C. and Held, C.
    Physical Chemistry Chemical Physics 23 (2021)
    The use of water as a component of deep eutectic systems (DES) has raised some questions regarding its influence on the nature of the mixture. Does it form a DES or an aqueous solution and what is the role of water? In this work, the nature of citric acid:l-arginine:water mixtures was explored through phase equilibria studies and spectroscopic analysis. In a first step, PC-SAFT was validated as a predictive tool to model the water influence on the solid liquid equilibria (SLE) of the DES reline using the individual-component approach. Hence, activity coefficients in the ternary systems citric acid:l-arginine:water and respective binary combinations were studied and compared using ePC-SAFT. It was observed that the water-free mixtures citric acid:l-arginine showed positive deviation from Raoult's law, while upon addition of water strong negative deviation from Raoult's law was found, yielding melting depressions around 100 K. Besides these strong interactions, pH was found to become acidic (pH = 3.5) upon water addition, which yields the formation of charged species ([H2Cit]- and [l-arg]+). Thus, the increased interactions between the molecules upon water addition might be caused by several mechanisms such as hydrogen bonding or ionic forces, both being induced by water. For further investigation, the liquid mixtures citric acid:l-arginine:water were studied by FTIR and NMR spectroscopy. FTIR spectra disproved a possible solubility enhancement caused by salt formation between citric acid and l-arginine, while NMR spectra supported the formation of a hydrogen bonding network different from the binary systems citric acid:water and l-arginine:water. Either being a DES or other type of non-ideal solution, the liquefaction of the studied systems is certainly caused by a water-mediator effect based on the formation of charged species and cross interactions between the mixture constituents. This journal is © the Owner Societies.
    view abstract10.1039/d0cp04992a
  • 5-Hydroxymethylfurfural Synthesis in Nonaqueous Two-Phase Systems (NTPS)-PC-SAFT Predictions and Validation
    Knierbein, M. and Voges, M. and Held, C.
    Organic Process Research and Development 24 (2020)
    The condensation reaction of fructose to 5-hydroxymethylfurfural (HMF) is acid-catalyzed, and it suffers from thermodynamic limitation of the conversion, poor kinetics, and consecutive reactions such as formation of humins from HMF. Different approaches exist to overcome these limitations. In this work, the combination of a nonaqueous solvent and a suitable extraction system is presented that ensures high reaction selectivity at full conversion, fast kinetics, and high partition selectivity of the product HMF over reactant fructose, keeping the temperature as low as 70 °C. In the first step of this work, the equation of state PC-SAFT was used to predict solvent effects on the reaction equilibrium of homogenous reaction systems. It was found that the two hydrophilic ionic liquids (ILs) [BMIM]Cl and [MIM]Cl shifted the reaction equilibrium to the product side by factors of 230 and 40, respectively, compared to the reaction in water. The predictions were verified by experimental data, which showed full conversion of fructose to HMF within less than 20 (60) min for the reaction in [MIM]Cl ([BMIM]Cl) with a high selectivity of up to 80%. Even more, the reaction in the [MIM]Cl solvent did not require adding a catalyst due to the acidic character of this IL. In the second step of this work, an in situ extraction of HMF was performed using a nonaqueous two-phase reaction system NTPS that was designed with PC-SAFT. The NTPS contains the reaction phase (either [BMIM]Cl or [MIM]Cl) and the extraction agent, i.e., one of the ketones MEK, MIBK, or ethyl acetate. These IL + organic solvent NTPSs were analyzed and evaluated toward fructose conversion and partitioning of fructose and of HMF. PC-SAFT predicted that, among all systems studied in this work, the NTPS IL + MEK was the most promising for the reaction of fructose to HMF and the in situ removal of HMF from fructose. Experimental results could validate the PC-SAFT predictions, that is, IL + MEK NTPSs allowed efficient conversion of fructose to HMF and a partition selectivity of HMF over fructose of about 100%. This new NTPS does not require an additional catalyst due to the acidity of [MIM]Cl; it allows a high reaction selectivity of 87% at 20 min and 93% conversion, and it moreover provides high separation efficiency. In sum, these results open the door for further developments of in situ extraction systems in the future for efficient and fast fructose conversion and HMF separation from the reacting phase, keeping the temperature as low as possible. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acs.oprd.0c00072
  • Ancient globetrotters - Connectivity and putative native ranges of two cosmopolitan biofouling amphipods
    Beermann, J. and Hall-Mullen, A.K. and Havermans, C. and Coolen, J.W.P. and Crooijmans, R.P.M.A. and Dibbits, B. and Held, C. and Desiderato, A.
    PeerJ 8 (2020)
    The geographic distributions of some coastal marine species have appeared as cosmopolitan ever since they were first scientifically documented. In particular, for many benthic species that are associated with anthropogenic substrata, there is much speculation as to whether or not their broad distributions can be explained by natural mechanisms of dispersal. Here, we focused on two congeneric coastal crustaceans with cosmopolitan distributions - the tube-dwelling amphipods Jassa marmorata and Jassa slatteryi. Both species are common elements of marine biofouling on nearly all kinds of artificial hard substrata in temperate to warm seas. We hypothesized that the two species' modern occurrences across the oceans are the result of human shipping activities that started centuries ago. Mitochondrial DNA sequences of the CO1 fragment of specimens from distinct marine regions around the world were analysed, evaluating genetic structure and migration models and making inferences on putative native ranges of the two Jassa species. Populations of both species exhibited considerable genetic diversity with differing levels of geographic structure. For both species, at least two dominant haplotypes were shared among several geographic populations. Rapid demographic expansion and high migration rates between geographically distant regions support a scenario of ongoing dispersal all over the world. Our findings indicate that the likely former native range of J. marmorata is the Northwest Atlantic, whereas the likely former native range of J. slatteryi is the Northern Pacific region. As corroborated by the genetic connectivity between populations, shipping still appears to be the more successful vector of the two species' dispersal when compared to natural mechanisms. Historical invasion events that likely started centuries ago, along with current ongoing dispersal, confirm these species' identities as true "neocosmopolitans". © Copyright 2020 Beermann et al.
    view abstract10.7717/peerj.9613
  • Hidden diversity in Antarctica: Molecular and morphological evidence of two different species within one of the most conspicuous ascidian species
    Ruiz, M.B. and Taverna, A. and Servetto, N. and Sahade, R. and Held, C.
    Ecology and Evolution 10 (2020)
    The Southern Ocean is one of the most isolated marine ecosystems, characterized by high levels of endemism, diversity, and biomass. Ascidians are among the dominant groups in Antarctic benthic assemblages; thus, recording the evolutionary patterns of this group is crucial to improve our current understanding of the assembly of this polar ocean. We studied the genetic variation within Cnemidocarpa verrucosa sensu lato, one of the most widely distributed abundant and studied ascidian species in Antarctica. Using a mitochondrial and a nuclear gene (COI and 18S), the phylogeography of fifteen populations distributed along the West Antarctic Peninsula and Burdwood Bank/MPA Namuncurá (South American shelf) was characterized, where the distribution of the genetic distance suggested the existence of, at least, two species within nominal C. verrucosa. When reevaluating morphological traits to distinguish between genetically defined species, the presence of a basal disk in one of the genotypes could be a diagnostic morphological trait to differentiate the species. These results are surprising due to the large research that has been carried out with the conspicuous C. verrucosa with no differentiation between species. Furthermore, it provides important tools to distinguish species in the field and laboratory. But also, these results give new insights into patterns of differentiation between closely related species that are distributed in sympatry, where the permeability of species boundaries still needs to be well understood. © 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
    view abstract10.1002/ece3.6504
  • High-Pressure-Mediated Thiourea-Organocatalyzed Asymmetric Michael Addition to (Hetero)aromatic Nitroolefins: Prediction of Reaction Parameters by PCP-SAFT Modelling
    Weinbender, T. and Knierbein, M. and Bittorf, L. and Held, C. and Siewert, R. and Verevkin, S.P. and Sadowski, G. and Reiser, O.
    ChemPlusChem 85 (2020)
    Thiourea-organocatalyzed Michael additions of diethyl malonate to various heteroaromatic nitroolefins (13 examples) have been studied under high-pressure (up to 800 MPa) and ambient pressure conditions. High pressure was conducive to enhanced product yields by a factor of 2–12 at a given reaction time, high reaction rates (reaction times were decreased from 72–24 h down to 4–24 h) and high enantioselectivity. Elucidating the effects of solvents for maximizing reaction rates and yields has been carried out using the Perturbed-Chain Polar Statistical Associating Fluid Theory (PCP-SAFT), allowing for the first time a prediction of the kinetic profiles under high-hydrostatic-pressure conditions. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/cplu.202000364
  • Influence of cytosolic conditions on the reaction equilibrium and the reaction enthalpy of the enolase reaction accessed by calorimetry and van ‘t HOFF
    Vogel, K. and Greinert, T. and Harms, H. and Sadowski, G. and Held, C. and Maskow, T.
    Biochimica et Biophysica Acta - General Subjects 1864 (2020)
    Background: Thermodynamic methods are finding more and more applications in systems biology, which attempts to understand cell functions mechanistically. Unfortunately, the state variables used (reaction enthalpy and Gibbs energy) do not take sufficient account of the conditions inside of cells, especially the crowding with macromolecules. Methods: For this reason, the influence of crowding agents and various other parameters such as salt concentrations, pH and temperature on equilibrium position and reaction enthalpy of the glycolytic example reaction 9 (2-Phospoglycerate - > Phosphoenolpyruvate + H2O) was investigated. The conditions were chosen to be as close as possible to the cytosolic conditions. Poly(ethylene glycol) MW = 20,000 g mol−1 (PEG 20,000) was used to analyze the influence of crowding with macromolecules. The equation of state electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was applied to consider the influence of crowding agents on the reaction equilibria. Results and conclusions: For the reaction enthalpies and for the equilibria, it was found that the influence of salts and temperature is not pronounced while that of pH and PEG 20,000 concentration is considerable. Furthermore, it could be shown that under identical measurement conditions there are no differences between the van ‘t Hoff and the calorimetrically determined reaction enthalpy. General significance: The results show how important it is to consider the special cytosolic conditions when applying thermodynamic data in systems biology. © 2020 Elsevier B.V.
    view abstract10.1016/j.bbagen.2020.129675
  • Melting properties of amino acids and their solubility in water
    Do, H.T. and Chua, Y.Z. and Kumar, A. and Pabsch, D. and Hallermann, M. and Zaitsau, D. and Schick, C. and Held, C.
    RSC Advances 10 (2020)
    The state-of-the-art unit operation for separation and purification of amino acids is still crystallization, which requires solubility data and melting properties of pure compounds. Since measuring solubility is time-consuming, prediction tools are desired. Further, melting properties are not yet available due to decomposition of amino acids upon slow heating. In this work, melting properties of twenty amino acids (except Met) were measured by Fast Scanning Calorimetry (FSC) with heating rates up to 20 000 K s-1. PC-SAFT was used to predict interactions in amino acid + water systems. Additionally, solubility, pH, and PXRD was measured. By combining FSC and PC-SAFT, the solubility of 15 amino acids was successfully predicted in a wide temperature range in good agreement with the experimental data. Thus, this work provides melting properties of amino acids for the first time and highlights the usefulness of such data to predict material properties such as aqueous solubility of amino acids. © 2020 The Royal Society of Chemistry.
    view abstract10.1039/d0ra08947h
  • Modeling the CO2Solubility in Aqueous Electrolyte Solutions Using ePC-SAFT
    Pabsch, D. and Held, C. and Sadowski, G.
    Journal of Chemical and Engineering Data 65 (2020)
    Carbon dioxide (CO2) solubility in aqueous electrolyte solutions is of special interest for carbon capture and storage and for biochemical processes, particularly at moderate to high temperatures, pressures, and electrolyte concentrations. Unfortunately, experimental determination at such conditions is rather laborious. Therefore, the ion-based model ePC-SAFT was used in this work to model the CO2solubility in such systems over a broad range of conditions. The mixtures under investigation were the basis system CO2+ water and higher systems containing either NaCl, KCl, MgCl2, CaCl2, NaNO3, KNO3, Mg(NO3)2, or NaHCO3. In the pH range considered in this work (pH < 7), CO2dissociation reactions were found to be negligible; thus, only physical interactions were considered. Assuming induced association for CO2, binary interaction parameters between CO2-water and CO2-ion species were determined by fitting to literature data. For this purpose, different literature data sets were compared, and only the most reliable data were used to estimate the binary parameters. ePC-SAFT was found to be able to accurately model the CO2solubility in water as well as in aqueous systems containing electrolytes over a broad range of temperatures, pressures, and salt concentrations. © 2020 American Chemical Society. All rights reserved.
    view abstract10.1021/acs.jced.0c00704
  • Molecular aspects of lipid metabolism in the midgut gland of the brown shrimp Crangon crangon
    Martínez-Alarcón, D. and Hagen, W. and Held, C. and Saborowski, R.
    Comparative Biochemistry and Physiology Part - B: Biochemistry and Molecular Biology 248-249 (2020)
    The brown shrimp, Crangon crangon, is well adapted to the variable environmental conditions in the southern North Sea. It is very abundant, has high reproduction rates, and holds a key position in coastal ecosystems. This species has very low lipid deposits in the midgut gland, suggesting that the main function of the midgut gland is metabolic turnover rather than energy storage. Based on seasonal gene expression studies and established transcriptome data, we investigated key components of lipid metabolic pathways. Gene expression of triacylglycerol lipase, phospholipase, and fatty acid desaturase were analyzed and compared with that of other digestive enzymes involved in lipid, carbohydrate, and protein catabolism. Our results suggest that gene expression of digestive enzymes involved in lipid metabolism is modulated by the lipid content in the midgut gland and is related to food availability. Brown shrimp seem to be capable of using cellular phospholipids during periods of food paucity but high energetic (lipid) requirements. Two of three isoforms of fatty acid binding proteins (FABPs) from the midgut gland involved in fatty acid transport showed specific mutations of the binding site. We hypothesize that the mutations in FABPs and deficiencies in anabolic pathways limit lipid storage capacities in the midgut gland of C. crangon. In turn, food utilization, including lipid catabolism, has to be efficient to fulfill the energetic requirements of brown shrimp. © 2020 The Authors
    view abstract10.1016/j.cbpb.2020.110465
  • Odd-even effect for efficient bioreactions of chiral alcohols and boosted stability of the enzyme
    Bülow, M. and Schmitz, A. and Mahmoudi, T. and Schmidt, D. and Junglas, F. and Janiak, C. and Held, C.
    RSC Advances 10 (2020)
    We describe a holistic approach for achieving a nearly quantitative conversion for an enzymatic reaction while simultaneously increasing the long-term stability of the enzyme. The approach provided chemical control of bioreactions by utilizing newly synthesized tetrahydrothiophene-based ionic liquids (THT ILs). We showcased its power by using THT-ILs as additives at a low concentration (only 10 mmol L-1) in the alcohol dehydrogenase (ADH)-catalyzed synthesis of methylated 1-phenylethanol (Me-PE). We discovered an "odd-even"effect of the IL-cation chain length: Me-PE displayed beneficial interactions with THT ILs having odd-numbered chain lengths and deleterious interactions with those having even-numbered chain lengths. An intermolecular thermodynamic simulation of the bulk phase and critical micelle concentration investigations of the local surroundings of the THT-ILs proved the occurrence of these interactions, and these two methods confirmed the odd-even effect from different perspectives. Additionally, storing the ADH enzyme in pure THT IL at room temperature allowed for a boosted long-term stability of the enzyme (500 times greater than that in aqueous buffer) without the need for freezing. This journal is © The Royal Society of Chemistry.
    view abstract10.1039/d0ra05406b
  • Partitioning of water-soluble vitamins in biodegradable aqueous two-phase systems: Electrolyte perturbed-chain statistical associating fluid theory predictions and experimental validation
    Wysoczanska, K. and Do, H.T. and Sadowski, G. and Macedo, E.A. and Held, C.
    AIChE Journal 66 (2020)
    Partition coefficients (K) of vitamins (riboflavin, nicotinic acid, nicotinamide, folic acid, cyanocobalamin) in aqueous two-phase systems (ATPS) composed by polyethylene glycol (PEG 4000, PEG 6000) and organic salt (sodium citrate and sodium tartrate) at T = 298.15 K and p = 1 bar have been studied. Data on liquid–liquid equilibria of the ATPS considered in this study have been taken from the literature (PEG-Na3Citrate) or measured in this work (PEG-Na2Tartrate) for PEG 4000 and PEG 6000 at T = 298.15 K and p = 1 bar. The experimental K values were validated by electrolyte perturbed-chain-statistical associating fluid theory predictions. The neutral cyanocobalamin has the highest K values among all studied vitamins at any ATPS studied in this work. This finding contrasted with expectations based on literature data which let assume that charged species have typically the highest K values in the considered ATPS. Thus, besides the typically strong charge–charge interactions especially specific forces (e.g., hydrogen bonding) explains the strong PEG-cyanocobalamin interaction resulting in the high K values. © 2020 The Authors. AIChE Journal published by Wiley Periodicals LLC on behalf of American Institute of Chemical Engineers.
    view abstract10.1002/aic.16984
  • Paving the way to solubility through volatility: Thermodynamics of imidazolium-based ionic liquids of the type [CnC1Im][I]
    Zaitsau, D.H. and Siewert, R. and Pimerzin, A.A. and Bülow, M. and Held, C. and Loor, M. and Schulz, S. and Verevkin, S.P.
    Fluid Phase Equilibria 522 (2020)
    Ionic liquids are effectively used for manufacturing of nanoparticles for thermoelectric generators and in the field of hydrogen storage. Development and optimization of these processes require knowledge of the thermodynamic properties of ionic liquids. Thermochemical study of the series of 1-alkyl-3-methylimidazolium iodides is presented in this work. Vapor pressures and vaporization enthalpies have been measured by using quartz-crystal microbalance. Solution enthalpies were measured by using solution calorimetry. Thermodynamics of aqueous solutions, solubility parameters and miscibility of ILs in eleven organic solvents were derived and discussed. The absence of thermal decomposition of [C4C1Im][I] under vaporization conditions has been demonstrated experimentally and theoretically. It has been shown that vaporization enthalpies are linearly dependent on the chain length of the alkyl substituent and linearly dependent on the surface tension. Aqueous-phase enthalpies of formation of alkyl imidazolium cations have been derived with help of solution calorimetry. © 2020 Elsevier B.V.
    view abstract10.1016/j.fluid.2020.112767
  • Phylogenetic relationship within cumacea (Crustacea: Peracarida) and genetic variability of two antarctic species of the family leuconidae [Relación filogenética de los cumacea (Crustacea: peracarida) y variabilidad genética de dos especies antárticas de la familia leuconidae]
    Rehm, P. and Thatje, S. and Leese, F. and Held, C.
    Scientia Marina 84 (2020)
    Phylogenetic hypotheses for the peracarid order Cumacea are scarce and have not provided a solution to the full extent. In the present study, a fragment of the mitochondrial 16S rDNA was used to erect a phylogenetic hypothesis for three cumacean families, Diastylidae, Bodotriidae and Leuconidae, along with intra-family relationships of the latter. The Cumacea resolved monophyletic with tanaids and isopods as outgroup taxa. The Diastylidae were the only family with good support for monophyly. The genus Leucon resolved paraphyletic, whereas the subgenus Crymoleucon was monophyletic. Furthermore, the genetic structure was analysed for two leuconid species, Leucon antarcticus Zimmer, 1907 and L. intermedius Mühlenhardt-Siegel, 1996, from the Weddell Sea and the Ross Sea. The two species showed different patterns of intraspecific genetic variability. In contrast to L. intermedius, a bimodal distribution of pairwise genetic distances was observed for L. antarcticus, which is correlated with geographical and depth distributions between the Ross Sea and the Weddell Sea. Although a clear evaluation of cryptic speciation in these species requires additional work on more specimens from more geographic regions and broader depth ranges, differences shown in the sequences of 16S rDNA can only be explained by genetic separation of populations between the Weddell Sea and the Ross Sea for an extended period of time. © 2020 CSIC.
    view abstract10.3989/scimar.05053.17A
  • Promising Thiolanium Ionic Liquid for Extraction of Aromatics from Aliphatics: Experiments and Modeling
    Lubben, M.J. and Canales, R.I. and Lyu, Y. and Held, C. and Gonzalez-Miquel, M. and Stadtherr, M.A. and Brennecke, J.F.
    Industrial and Engineering Chemistry Research 59 (2020)
    Four ionic liquids (ILs) consisting of the bis(trifluoromethylsulfonyl)imide anion paired with a phosphonium, pyridinium, imidazolium, or thiolanium cation were investigated as potential solvents to separate aromatic from aliphatic compounds in a liquid-liquid extraction process. The thiolanium IL was chosen due to its structural similarity to sulfolane, which is the most widely used organic solvent for aromatic/aliphatic separation in the industry. Interestingly, ternary liquid-liquid equilibrium data shows that 1-n-butylthiolanium bis(trifluoromethylsulfonyl)imide performs as well as the equivalent imidazolium IL despite the fact that it is not aromatic and cannot use π-πinteractions (which are available to imidazolium ILs) to enhance aromatic solubility and selectivity. Moreover, we provide quantification of the IL solubility in the organic-rich phase, which is on the order of 10-4 mole fraction. This quantity is important because it would represent IL loss and product contamination in a real extraction process; however, it is commonly reported to be nondetectable. The nonrandom two-liquid (NRTL), perturbed-chain statistical associating fluid theory (PC-SAFT), COSMO-RS, and COSMO-SAC models are appropriate for the mixtures explored, and each model's strengths and weaknesses are discussed. Copyright © 2020 American Chemical Society.
    view abstract10.1021/acs.iecr.0c02292
  • Protecting Antarctic blue carbon: as marine ice retreats can the law fill the gap?
    Gogarty, B. and McGee, J. and Barnes, D.K.A. and Sands, C.J. and Bax, N. and Haward, M. and Downey, R. and Moreau, C. and Moreno, B. and Held, C. and Paulsen, M.L.
    Climate Policy 20 (2020)
    As marine-ice around Antarctica retracts, a vast ‘blue carbon’ sink, in the form of living biomass, is emerging. Properly protected and promoted Antarctic blue carbon will form the world’s largest natural negative feedback on climate change. However, fulfilling this promise may be challenging, given the uniqueness of the region and the legal systems that govern it. In this interdisciplinary study, we explain: the global significance of Antarctic blue carbon to international carbon mitigation efforts; the urgent need for international legal protections for areas where it is emerging; and the hurdles that need to be overcome to realize those goals. In order to progress conservation efforts past political blockages we recommend the development of an inter-instrument governance framework that quantifies the sequestration value of Antarctic blue carbon for attribution to states’ climate mitigation commitments under the 2015 Paris Agreement. Key policy insights Blue-carbon emergence around Antarctica’s coastlines will potentially store up to 160,000,000 tonnes of carbon annually. Blue-carbon will emerge in areas of rich biomass that will make it vulnerable to harvesting and other human activities; it is essential to incentivise conserving, rather than commercial exploitation of newly ice-free areas of the Southern Ocean. Antarctic blue carbon is a practical and prime candidate to build a cooperative, inter-instrument, non-market mitigation around; this should be considered at the ‘blue COP’ UN Climate change discussions in Spain. Allowing Antarctic fishing states to account for the carbon storage value of blue carbon zones through a non-market approach under the Paris Agreement could provide a vital incentive to their protection under the Antarctic Treaty System. The Scientific Committee on Antarctic Research would be the ideal body to facilitate the necessary connections between the relevant climate and Antarctic governance regimes. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/14693062.2019.1694482
  • Standard Gibbs energy of metabolic reactions: IV. Triosephosphate isomerase reaction
    Greinert, T. and Baumhove, K. and Sadowski, G. and Held, C.
    Biophysical Chemistry 258 (2020)
    The glycolytic pathway is present in most organisms and represents a central part of the energy production mechanism in a cell. For a general understanding of glycolysis, the investigation from a thermodynamic point of view is essential and allows realising thermodynamic feasibility analyses under in vivo conditions. However, available literature standard Gibbs energies of reaction, ΔRg′0, are calculated using equilibrium-molality ratios Km′, which might lead to a misinterpretation of the glycolytic pathway. It was the aim of this work to thermodynamically investigate the triosephosphate isomerase (TPI) reaction to provide new activity-based reaction data. In vitro equilibrium experiments were performed, and activity coefficients were predicted with the equation of state electrolyte PC-SAFT (ePC-SAFT). The combination of experimental concentrations and predicted activity coefficients yielded the thermodynamic equilibrium constant Ka and a new value for ΔRg′0(298.15 K, pH 7) = 7.1 ± 0.3 kJ mol‑1. The availability of the new ΔRg′0 value allowed predicting influences of the reaction medium on the reaction equilibrium of the TPI reaction. In this work, influences of the initial substrate concentration, pH and Mg2+ concentration on the reaction equilibrium were investigated and a method is presented to predict these influences. The higher the substrate concentration and the higher the temperature, the stronger the reaction equilibrium is shifted on the product side. While the pH did not have a significant influence on the reaction equilibrium, Mg2+ yielded a shift of the reaction equilibrium to the substrate side. All these effects were predicted correctly with ePC-SAFT. Based on the ePC-SAFT predictions we concluded that a charge-reduction of the product by complexation of the product with Mg2+ was responsible for the strong influence of Mg2+ on the reaction equilibrium. Finally, the standard enthalpy of reaction of ΔRh′0(pH 7) = 18 ± 7 kJ mol‑1 was determined with the equilibrium constants Ka at 298.15 K, 304.15 K and 310.15 K using the van ‘t Hoff equation. © 2020 Elsevier B.V.
    view abstract10.1016/j.bpc.2020.106330
  • Standard Gibbs energy of metabolic reactions: V. Enolase reaction
    Greinert, T. and Vogel, K. and Seifert, A.I. and Siewert, R. and Andreeva, I.V. and Verevkin, S.P. and Maskow, T. and Sadowski, G. and Held, C.
    Biochimica et Biophysica Acta - Proteins and Proteomics 1868 (2020)
    The glycolytic pathway is one of the most important pathways for living organisms, due to its role in energy production and as supplier of precursors for biosynthesis in living cells. This work focuses on determination of the standard Gibbs energy of reaction ΔRg′0 of the enolase reaction, the ninth reaction in the glycolysis pathway. Exact ΔRg′0 values are required to predict the thermodynamic feasibility of single metabolic reactions or even of metabolic reaction sequences under cytosolic conditions. So-called “apparent” standard data from literature are only valid at specific conditions. Nevertheless, such data are often used in pathway analyses, which might lead to misinterpretation of the results. In this work, equilibrium measurements were combined with activity coefficients in order to obtain new standard values ΔRg′0 for the enolase reaction that are independent of the cytosolic conditions. Reaction equilibria were measured at different initial substrate concentrations and temperatures of 298.15 K, 305.15 K and 310.15 K at pH 7. The activity coefficients were predicted using the equation of state electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT). The ePC-SAFT parameters were taken from literature or fitted to new experimentally determined osmotic coefficients and densities. At 298.15 K and pH 7, a ΔRg′0(298.15 K, pH 7) value of −2.8 ± 0.2 kJ mol− 1 was obtained. This value differs by up to 5 kJ mol− 1 from literature data. Reasons are the poorly defined “standard” conditions and partly undefined reaction conditions of literature works. Finally, using temperature-dependent equilibrium constants and the van ‘t Hoff equation, the standard enthalpy of reaction of ΔRh′0(298.15 K, pH 7) = 27 ± 10 kJ mol− 1 was determined, and a similar value was found by quantum-chemistry calculations. © 2020 Elsevier B.V.
    view abstract10.1016/j.bbapap.2020.140365
  • Standard Gibbs energy of metabolic reactions: VI. Glyceraldehyde 3-phosphate dehydrogenase reaction
    Greinert, T. and Vogel, K. and Mühlenweg, J.-K. and Sadowski, G. and Maskow, T. and Held, C.
    Fluid Phase Equilibria 517 (2020)
    Glycolysis is a very central metabolic pathway for many organisms because it represents a key component in their energy production. For this reason, it has always been an extensively studied pathway. The glyceraldehyde 3-phosphate dehydrogenase (GDH) reaction is an important reaction of glycolysis yielding nicotinamide adenine dinucleotide (NADH). The aim of this work is to investigate the thermodynamics of the GDH reaction and determine the standard Gibbs energy of reaction ΔRg'0 and standard enthalpy of reaction ΔRh'0. Currently, so-called ‘standard’ data exist in the literature that depend on the conditions they were measured at. In this work, ΔRg'0 and ΔRh'0 values were determined that are independent from reaction conditions by accounting for the activity coefficients of the reacting substances. Therefore, the equation of state electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was used. The required ePC-SAFT parameters were taken from literature or fitted to new experimental osmotic coefficients. A value of ΔRg'0 = 51.5 ± 0.4 kJ mol−1 was determined at 298.15 K. This value deviates by up to 10 kJ mol−1 from existing literature values, caused by activity coefficients in the reaction medium. It can be used to determine the Gibbs energy of reaction ΔRg', which will allow statements concerning the feasibility of the GDH reaction. Further, a method is presented to predict influences of pH, initial substrate concentration and Mg2+ concentration on the reaction equilibrium. Finally, we measured the standard reaction enthalpy for the GDH reaction ΔRh'0 by titration calorimetric measurements (ΔRh'0 = 4.6 ± 0.1 kJ mol−1). This value was within van ’t Hoff evaluated ΔRh'0 (9 ± 16 kJ mol−1) using temperature-dependent equilibrium constants from equilibrium measurements corrected by ePC-SAFT predicted activity coefficients. © 2020 Elsevier B.V.
    view abstract10.1016/j.fluid.2020.112597
  • Tetrahydrothiophene-Based Ionic Liquids: Synthesis and Thermodynamic Characterizations
    Schmitz, A. and Bülow, M. and Schmidt, D. and Zaitsau, D.H. and Junglas, F. and Knedel, T.-O. and Verevkin, S.P. and Held, C. and Janiak, C.
    ChemistryOpen (2020)
    S-alkyltetrahydrothiophenium, [CnTHT]+ bis(trifluorosulfonyl)imide, [NTf2]− room temperature ionic liquids (ILs) and tetraphenylborate, [BPh4]− salts with alkyl chain lengths from C4 to C10 have been prepared. The ILs and salts were characterized and their purity verified by 1H- and 13C-nuclear magnetic resonance, elemental analysis, ion chromatography, Karl-Fischer titration, single crystal X-ray diffraction as well as thermogravimetric analysis. The experimentally determined density and viscosity decrease with increasing temperature. The experimental solubility of the [CnTHT][NTf2]-ILs in water (75 to 2.2 mg/L for C4 to C10) was modelled with very good agreement by Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT), based on the extremely low vapor pressures for the [CnTHT][NTf2]-ILs measured in this work (4.15 to 0.037 ⋅ 10−7×psat for C4 to C10). PC-SAFT is able to predict and correlate different thermodynamic properties by estimating the Helmholtz residual energy. © 2020 The Authors. Published by Wiley-VCH GmbH
    view abstract10.1002/open.202000228
  • The role of molecular interactions on Michaelis constants of α-chymotrypsin catalyzed peptide hydrolyses
    Knierbein, M. and Held, C. and Sadowski, G.
    Journal of Chemical Thermodynamics 148 (2020)
    In this work, the effects of co-solvent and pressure on Michaelis constants at ambient temperature were analyzed for the enzymatic peptide hydrolyses of L-phenylalanine-p-nitroanilide (HPNA) and of N-succinyl-L-phenylalanine-p-nitroanilide (SPNA). These two substrates resemble each other in their molecular structure. That is, at the position of SPNA's succinyl-group (S), HPNA possesses a hydrogen atom (H). Two co-solvents were considered: trimethylamine N-oxide and dimethyl sulfoxide. The thermodynamic model Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to predict the activity of HPNA and SPNA under different reaction conditions regarding solvent composition and pressure. The PC-SAFT parameters (pure-component parameters and one binary parameter between substrate and solvent) were fitted to solubility data of HPNA in different solvents (water, ethanol, ethyl acetate, dimethyl sulfoxide), which were measured in this work at 30 °C and 1 bar. The resulting PC-SAFT predicted Michaelis constants were validated by experimental literature data. Results show that pressure decreased the Michaelis constants of both reactions, HPNA hydrolysis and SPNA hydrolysis. In spite of that, co-solvent effects on the Michaelis constants were predicted to be contrary for the two hydrolysis reactions. For the hydrolysis of HPNA, the co-solvents under investigation decreased the Michaelis constant while the co-solvents increased the Michaelis constant for the hydrolysis of SPNA. These PC-SAFT predictions were in qualitative agreement with the experimental literature data. This shows that molecular interactions are the key to understand the effects of co-solvents on Michaelis constants for the considered reactions. Applying the thermodynamic model PC-SAFT allowed predicting the observed combined effects of co-solvent and pressure on enzymatic reaction kinetics, which opens the door for solvent design of enzymatic reactions in the future. © 2020 Elsevier Ltd
    view abstract10.1016/j.jct.2020.106142
  • Thermodynamic gEModels and Equations of State for Electrolytes in a Water-Poor Medium: A Review
    Held, C.
    Journal of Chemical and Engineering Data 65 (2020)
    Research on the thermodynamics of electrolytes is timeless, and modeling an electrolyte solution might be considered to be a golden oldie, which was, is, and will be important in the design of processes and new materials in the future. The reason is that electrolytes play important roles in different scientific disciplines, such as material development, technical processes (chemical industry, biotechnology, and pharma and food industries), and most recently the energy sector. Closely connected is the further development of advanced thermodynamic models. The age of digitalization requires robust physical models as the basis for static and dynamic process modeling, and that will provide the basis for surrogate approaches in future machine learning developments. This all brings thermodynamic modeling to a consideration of its most important feature. There are many thermodynamic approaches which have been developed to correlate, model, and predict the properties and phase behavior of electrolytes. Usually, this has been very successful for aqueous electrolyte solutions. However, for solutions with poor water content, electrolyte modeling is challenging. This mini-review summarizes the recent advance of thermodynamic models for electrolyte solutions in a water-poor medium and suggests the required theoretical framework. © 2020 American Chemical Society.
    view abstract10.1021/acs.jced.0c00812
  • Thermodynamics and kinetics of glycolytic reactions. Part i: Kinetic modeling based on irreversible thermodynamics and validation by calorimetry
    Vogel, K. and Greinert, T. and Reichard, M. and Held, C. and Harms, H. and Maskow, T.
    International Journal of Molecular Sciences 21 (2020)
    In systems biology, material balances, kinetic models, and thermodynamic boundary conditions are increasingly used for metabolic network analysis. It is remarkable that the reversibility of enzyme‐catalyzed reactions and the influence of cytosolic conditions are often neglected in kinetic models. In fact, enzyme‐catalyzed reactions in numerous metabolic pathways such as in glycolysis are often reversible, i.e., they only proceed until an equilibrium state is reached and not until the substrate is completely consumed. Here, we propose the use of irreversible thermodynamics to describe the kinetic approximation to the equilibrium state in a consistent way with very few adjustable parameters. Using a flux‐force approach allowed describing the influence of cytosolic conditions on the kinetics by only one single parameter. The approach was applied to reaction steps 2 and 9 of glycolysis (i.e., the phosphoglucose isomerase reaction from glucose 6‐ phosphate to fructose 6‐phosphate and the enolase‐catalyzed reaction from 2‐phosphoglycerate to phosphoenolpyruvate and water). The temperature dependence of the kinetic parameter fulfills the Arrhenius relation and the derived activation energies are plausible. All the data obtained in this work were measured efficiently and accurately by means of isothermal titration calorimetry (ITC). The combination of calorimetric monitoring with simple flux‐force relations has the potential for adequate consideration of cytosolic conditions in a simple manner. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstract10.3390/ijms21218341
  • Thermodynamics and kinetics of glycolytic reactions. Part II: Influence of cytosolic conditions on thermodynamic state variables and kinetic parameters
    Vogel, K. and Greinert, T. and Reichard, M. and Held, C. and Harms, H. and Maskow, T.
    International Journal of Molecular Sciences 21 (2020)
    For systems biology, it is important to describe the kinetic and thermodynamic properties of enzyme-catalyzed reactions and reaction cascades quantitatively under conditions prevailing in the cytoplasm. While in part I kinetic models based on irreversible thermodynamics were tested, here in part II, the influence of the presumably most important cytosolic factors was investigated using two glycolytic reactions (i.e., the phosphoglucose isomerase reaction (PGI) with a uni-uni-mechanism and the enolase reaction with an uni-bi-mechanism) as examples. Crowding by macromolecules was simulated using polyethylene glycol (PEG) and bovine serum albumin (BSA). The reactions were monitored calorimetrically and the equilibrium concentrations were evaluated using the equation of state ePC-SAFT. The pH and the crowding agents had the greatest influence on the reaction enthalpy change. Two kinetic models based on irreversible thermodynamics (i.e., single parameter flux-force and two-parameter Noor model) were applied to investigate the influence of cytosolic conditions. The flux-force model describes the influence of cytosolic conditions on reaction kinetics best. Concentrations of magnesium ions and crowding agents had the greatest influence, while temperature and pH-value had a medium influence on the kinetic parameters. With this contribution, we show that the interplay of thermodynamic modeling and calorimetric process monitoring allows a fast and reliable quantification of the influence of cytosolic conditions on kinetic and thermodynamic parameters. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
    view abstract10.3390/ijms21217921
  • Vapor Pressure Assessment of Sulfolane-Based Eutectic Solvents: Experimental, PC-SAFT, and Molecular Dynamics
    Lima, F. and Dietz, C.H.J.T. and Silvestre, A.J.D. and Branco, L.C. and Canongia Lopes, J. and Gallucci, F. and Shimizu, K. and Held, C. and Marrucho, I.M.
    Journal of Physical Chemistry B 124 (2020)
    Since their discovery, deep eutectic solvents (DES) have been explored in multiple applications. However, the complete physicochemical characterization is still nonexistent for many of the proposed and used DES. In particular, vapor pressure, which is a crucial property for the application of DES as solvents, is very rarely available. In this work, the measurement of the total and partial pressures of two sulfolane-based DES, tetrabutylammonium bromide:sulfolane and tetrabutylphosphonium bromide:sulfolane, in several proportions, from 40 to 100 °C and atmospheric pressure, was performed using headspace gas chromatography mass spectrometry, HS-GC-MS. A large decrease on the total pressure was recorded which, together with the finding that total pressures showed negative deviations from Raoult's law, is indicative of the favorable, strong interactions between the two components within the DES. Additionally, the study of vapor pressure change with DES molar composition was carried out, and surprisingly, the existence of inflection points in the pressure curve was observed. Experimental results were modeled using the PC-SAFT equation of state, and in addition, MD simulations were performed to provide a molecular understanding of the pressure data. Considering the different results and insights obtained from the used strategies, it can be concluded that both DES systems have especially strong interactions between salt and sulfolane, at high sulfolane content, due to the different structural rearrangement of the liquid state. © 2020 American Chemical Society.
    view abstract10.1021/acs.jpcb.0c04837
  • 110th Anniversary: Distribution Coefficients of Furfural and 5-Hydroxymethylfurfural in Hydrophobic Deep Eutectic Solvent + Water Systems: Experiments and Perturbed-Chain Statistical Associating Fluid Theory Predictions
    Dietz, C.H.J.T. and Gallucci, F. and Van Sint Annaland, M. and Held, C. and Kroon, M.C.
    Industrial and Engineering Chemistry Research 58 (2019)
    Furfural (FF) and 5-hydroxymethylfurfural (HMF) are intermediates for many products, such as monomers for bioplastics, and can be obtained from various renewable resources. The isolation of these sugar-derived molecules from aqueous solutions is one of the main challenges in biorefinery processes. In the work described in this paper, the separation of FF and HMF from aqueous phases is carried out with hydrophobic deep eutectic solvents (DESs) as new extracting agents. Distribution coefficients of FF and HMF in 10 different hydrophobic DES + water systems have been measured and compared to that of the benchmark extracting agent (toluene). The dependence of the distribution coefficients on the presence of sugars in the system has also been investigated. The hydrophobic DESs were found to selectively extract FF and HMF from aqueous solutions without any co-extraction or precipitation of sugars. Finally, the distribution coefficients have been successfully predicted with PC-SAFT (perturbed-chain statistical associating fluid theory) without the need to fit any parameter to the measured distribution coefficients. © 2019 American Chemical Society.
    view abstract10.1021/acs.iecr.8b06234
  • Aggregation control of Ru and Ir nanoparticles by tunable aryl alkyl imidazolium ionic liquids
    Schmolke, L. and Lerch, S. and Bülow, M. and Siebels, M. and Schmitz, A. and Thomas, J. and Dehm, G. and Held, C. and Strassner, T. and Janiak, C.
    Nanoscale 11 (2019)
    Metal-nanoparticles (M-NPs) were synthesized in a wet-chemical synthesis route in tunable aryl alkyl ionic liquids (TAAILs) based on the 1-aryl-3-alkyl-substituted imidazolium motif from Ru3(CO)12 and Ir4(CO)12 by microwave-heating induced thermal decomposition. The size and size dispersion of the NPs were determined by transmission electron microscopy (TEM) to an average diameter of 2.2(±0.1) to 3.9(±0.3) nm for Ru-NPs and to an average diameter of 1.4(±0.1) to 2.4(±0.1) nm for Ir-NPs. The TAAILs used contain the same bis(trifluoromethylsulfonyl)imide anion but differ in the substituents on the 1-aryl ring, e.g. 2-methyl-, 4-methoxy- and 2,4-dimethyl groups and in the 3-alkyl chain lengths (C4H9, C5H11, C8H17, C9H19, C11H23). All used TAAILs are suitable for the stabilization of Ru- and Ir-NPs over months in the IL dispersion. Different from all other investigations on M-NP/IL systems which we are aware of the particle separation properties of the TAAILs vary strongly as a function of the aryl substituent. Good NP separation can be achieved with the 4-methoxyphenyl- and 2,4-dimethylphenyl-substituted ILs, irrespective of the 3-alkyl chain lengths. Significant aggregation can be observed for 2-methylphenyl-substituted ILs. The good NP separation can be correlated with a negative electrostatic potential at the 4-methoxyphenyl or 4-methylphenyl substituent that is in the para-position of the aryl ring, whereas the 2-(ortho-)methylphenyl group assumes no negative potential. ϵ-ePC-SAFT calculations were used to validate that the interactions between ILs and the washing agents (required for TEM analyses) do not cause the observed aggregation/separation behaviour of the M-NPs. Ru-NPs were investigated as catalysts for the solvent-free hydrogenation of benzene to cyclohexane under mild conditions (70 °C, 10 bar) with activities up to 760 (mol cyclohexane) (mol Ru)-1 h-1 and over 95% conversion in ten consecutive runs for Ru-NPs. No significant loss of catalytic activity could be observed. This journal is © The Royal Society of Chemistry.
    view abstract10.1039/c8nr10286d
  • Catalytic Low-Temperature Dehydration of Fructose to 5-Hydroxymethylfurfural Using Acidic Deep Eutectic Solvents and Polyoxometalate Catalysts
    Körner, S. and Albert, J. and Held, C.
    Frontiers in Chemistry 7 (2019)
    HMF synthesis typically requires high temperature and is carried out in aqueous solutions. In this work, the low-temperature dehydration of fructose to HMF in different deep eutectic solvents (DES) was investigated. We found a very active and selective reaction system consisting of the DES tetraethyl ammonium chloride as hydrogen bond acceptor (HBA) and levulinic acid as hydrogen bond donor (HBD) in a molar ratio of 1:2 leading to a maximum HMF yield of 68% after 120 h at 323 K. The DES still contained a low amount of water at the initial reaction, and water was also produced during the reaction. Considering the DES properties, neither the molar ratio in the DES nor the reaction temperature had a significant influence on the overall performance of the reaction system. However, the nature of the HBA as well as the acidity of the HBD play an important role for the maximum achievable HMF yield. This was validated by measured yields in a DES with different combinations of HBD (levulinic acid and lactic acid) and HBA (choline chloride and tetra-n-alkyl ammonium chlorides). Moreover, addition of vanadium containing catalysts, especially the polyoxometalate HPA-5 (H8PV5Mo7O40) leads to drastically increased reaction kinetics. Using HPA-5 and the DES tetraethyl ammonium chloride—levulinic acid we could reach a maximum HMF yield of 57% after only 5 h reaction time without decreasing the very high product selectivity. © Copyright © 2019 Körner, Albert and Held.
    view abstract10.3389/fchem.2019.00661
  • Combined co-solvent and pressure effect on kinetics of a peptide hydrolysis: An activity-based approach
    Knierbein, M. and Wangler, A. and Luong, T.Q. and Winter, R. and Held, C. and Sadowski, G.
    Physical Chemistry Chemical Physics 21 (2019)
    The application of co-solvents and high pressure has been reported to be an efficient means to tune the kinetics of enzyme-catalyzed reactions. Co-solvents and pressure can lead to increased reaction rates without sacrificing enzyme stability, while temperature and pH operation windows are generally very narrow. Quantitative prediction of co-solvent and pressure effects on enzymatic reactions has not been successfully addressed in the literature. Herein, we are introducing a thermodynamic approach that is based on molecular interactions in the form of activity coefficients of substrate and of enzyme in the multi-component solution. This allowed us to quantitatively predict the combined effect of co-solvent and pressure on the kinetic constants, i.e.The Michaelis constant KM and the catalytic constant kcat, of an α-CT-catalyzed peptide hydrolysis reaction. The reaction was studied in the presence of different types of co-solvents and at pressures up to 2 kbar, and quantitative predictions could be obtained for KM, kcat, and finally even primary Michaelis-Menten plots using activity coefficients provided by the thermodynamic model PC-SAFT. This journal is © the Owner Societies.
    view abstract10.1039/c9cp03868j
  • Cosolvent and pressure effects on enzyme-catalysed hydrolysis reactions
    Held, C. and Stolzke, T. and Knierbein, M. and Jaworek, M.W. and Luong, T.Q. and Winter, R. and Sadowski, G.
    Biophysical Chemistry 252 (2019)
    Thermodynamics and kinetics of biochemical reactions depend not only on temperature, but also on pressure and on the presence of cosolvents in the reaction medium. Understanding their effects on biochemical processes is a crucial step towards the design and optimization of industrially relevant enzymatic reactions. Such reactions typically do not take place in pure water. Cosolvents might be present as they are either required as stabilizer, as solubilizer, or in their function to overcome thermodynamic or kinetic limitations. Further, a vast number of enzymes has been found to be piezophilic or at least pressure-tolerant, meaning that nature has adapted them to high-pressure conditions. In this manuscript, we review existing data and we additionally present some new data on the combined cosolvent and pressure influence on the kinetics of biochemical reactions. In particular, we focus on cosolvent and pressure effects on Michaelis constants and catalytic constants of α-CT-catalysed peptide hydrolysis reactions. Two different substrates were considered in this work, N-succinyl-L-phenylalanine-p-nitroanilide and H-phenylalanine-p-nitroanilide. Urea, trimethyl-N-amine oxide, and dimethyl sulfoxide have been under investigation as these cosolvents are often applied in technical as well as in demonstrator systems. Pressure effects have been studied from ambient pressure up to 2 kbar. The existing literature data and the new data show that pressure and cosolvents must not be treated as independent effects. Non-additive interactions on a molecular level lead to a partially compensatory effect of cosolvents and pressure on the kinetic parameters of the hydrolysis reactions considered. © 2019
    view abstract10.1016/j.bpc.2019.106209
  • Density variations of TMAO solutions in the kilobar range: Experiments, PC-SAFT predictions, and molecular dynamics simulations
    Knierbein, M. and Held, C. and Hölzl, C. and Horinek, D. and Paulus, M. and Sadowski, G. and Sternemann, C. and Nase, J.
    Biophysical Chemistry 253 (2019)
    We present measurements, molecular dynamics (MD) simulations, and predictions using Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) of the density of aqueous solutions in a pressure range from 1 bar to 5000 bar, a pressure regime that is highly relevant for both biochemical applications and the fundamental understanding of solvation. The accurate determination of density data of pressurized solutions remains challenging. We determined relative density changes from the variations in X-ray absorption through the sample and developed a new water parameter set for PC-SAFT modeling that is appropriate for high pressure conditions in the kilobar regime. As a showcase, we studied trimethylamine N-oxide (TMAO) solutions and demonstrated that their compressibility decreases with the TMAO content. This result is linked to the stabilizing effect of TMAO on the local H-bond network of water. Experiments and calculations, which represent two independent methods, are in very good agreement and are in accordance with results of force field molecular dynamics simulations of the same systems. © 2019 Elsevier B.V.
    view abstract10.1016/j.bpc.2019.106222
  • Determination of the Total Vapor Pressure of Hydrophobic Deep Eutectic Solvents: Experiments and Perturbed-Chain Statistical Associating Fluid Theory Modeling
    Dietz, C.H.J.T. and Creemers, J.T. and Meuleman, M.A. and Held, C. and Sadowski, G. and Van Sint Annaland, M. and Gallucci, F. and Kroon, M.C.
    ACS Sustainable Chemistry and Engineering 7 (2019)
    Head-space gas chromatography mass spectrometry (HS-GC-MS) was used for the first time to measure the total vapor pressure of hydrophobic deep eutectic solvents (DESs). The new method was developed as a valid alternative for thermogravimetric analysis (TGA), as TGA did not allow obtaining reliable total vapor pressure data for the hydrophobic DESs studied in this work. The main advantage of HS-GC-MS is that the partial pressure of each DES constituent and the contribution of each DES constituent to the total vapor pressure of the mixture can be measured. The results give a clear indication of the interactions occurring between the DES constituents. Also, activity coefficients, enthalpies of evaporation, and activation energies for fluid displacement were obtained and correlated to the measured vapor pressure data. It was confirmed that the total vapor pressures of the hydrophobic DESs are very low in comparison to vapor pressures of commonly used volatile organic solvents like toluene. The total vapor pressures of the hydrophobic DESs were successfully predicted with perturbed-chain statistical associating fluid theory (PC-SAFT) when using PC-SAFT parameters for the individual DES constituents. © 2019 American Chemical Society.
    view abstract10.1021/acssuschemeng.8b05449
  • Guanidinium Cation Effect on the Water Activity of Ternary (S)Aminopentanedioic Acid Sodium Salt Solutions at 298.15 and 310.15 K
    Tsurko, E.N. and Neueder, R. and Held, C. and Kunz, W.
    Journal of Chemical and Engineering Data 64 (2019)
    Vapor pressure measurements were applied to the systems guanidinium hydrochloride (methanamidine hydrochloride) + sodium l-glutamate (S-aminopenthanedioic acid sodium salt) + water at varying concentrations of GndmCl and Na-l-Glu (m(NaGlu) = 0.1-1.6 mol/kg; m (GndmCl) = 0.104 mol/kg, 0.301 mol/kg, 0.684 mol/kg) for two temperatures, T = 298.15 and 310.15 K. From the experimental results, activities of water, activity coefficients of water, and the corresponding osmotic coefficients of the mixtures Na-l-Glu + GndmCl + water have been calculated, both being directly related to the chemical potentials of the different components and therefore to their Gibbs energy. The modeling of the components' chemical potentials in ternary GndmCl + Na-l-Glu + water solutions was done with the equation of state ePC-SAFT. Osmotic coefficients, fugacity coefficients, and activity coefficients of the mixture components were modeled. Experimental osmotic coefficient values demonstrate nonlinear concentration dependences with several extremums at different NaGlu molalities. The theoretical ePC-SAFT approach correctly describes the experimental data. Negative values of binary interaction parameters between the guanidinium ion and the amino acid salt were required in order to model osmotic coefficients of ternary systems salt + amino acid salt + water in good agreement with the experimental data, which shows that the non-Coulomb short-range interactions between ion and amino acid salt are very strong. © 2019 American Chemical Society.
    view abstract10.1021/acs.jced.8b01142
  • Incorporating a concentration-dependent dielectric constant into ePC-SAFT. An application to binary mixtures containing ionic liquids
    Bülow, M. and Ji, X. and Held, C.
    Fluid Phase Equilibria 492 (2019)
    Primitive thermodynamic models for electrolyte solutions require the dielectric constant ε. This property strongly depends on the concentration of the electrolytes in the mixture. Neglecting this dependency might be reasonable for modeling solutions at low electrolyte concentrations. However, in solutions containing ionic liquids (ILs) and especially for the calculation of liquid-liquid equilibria (LLE) of systems with ILs, liquid phases often contain high IL concentrations. At such conditions, neglecting the influence of concentration on ε is an oversimplification. In this work, an approach to account for the concentration-dependent dielectric constant within the Debye-Hückel theory was implemented into electrolyte Perturbed-Chain Statistical Associating Fluid Theory (original ePC-SAFT). This new approach was then applied to model LLE of binary mixtures containing water and commonly used hydrophobic ILs. These common ILs are comprised of the IL-cations [C n mim] + , [C n py] + , [C n mpy] + , [C n mpyr] + , [C 4 m 4 py] + and the IL-anions [BF 4 ] - , [NTf 2 ] - , [PF 6 ] - , [TFO] - . The LLE of binary mixtures water + IL were modeled at ambient pressure and different temperatures with the new ePC-SAFT and with the original ePC-SAFT [Ji et al. DOI: 10.1016/j.fluid.2012.05.029] without the concentration-dependent ε. Overall, the new approach within ePC-SAFT shows superior modeling as well as correlation capability compared to original ePC-SAFT, which was concluded by comparing both models with LLE data from literature. © 2019 Elsevier B.V.
    view abstract10.1016/j.fluid.2019.03.010
  • Liquid-Liquid Equilibria for Separation of Alcohols from Esters Using Deep Eutectic Solvents Based on Choline Chloride: Experimental Study and Thermodynamic Modeling
    Samarov, A. and Prikhodko, I. and Shner, N. and Sadowski, G. and Held, C. and Toikka, A.
    Journal of Chemical and Engineering Data 64 (2019)
    Deep eutectic solvent (DES) formed by choline chloride and glutaric acid was tested for the separation of azeotropic mixtures of ethanol-ethyl acetate, n-propanol-n-propyl acetate, n-butanol-n-butyl acetate, ethanol-ethyl propionate, n-propanol-n-propyl propionate, and n-butanol-n-butyl propionate. For this aim, the experimental data of liquid-liquid equilibria (LLE) were obtained at a temperature of 313.15 K and atmospheric pressure. Liquid-liquid tie-lines were determined and analyzed. The extraction performance of DES was characterized with distribution coefficients and values of selectivity with respect to alcohol. The NRTL model for LLE data correlation was used. Perturbed-chain statistical associating fluid theory had also been applied for modeling LLE using a "pseudo-component" approach for the DES. Both models were shown to give reasonable estimates for the selectivity values. Copyright © 2019 American Chemical Society.
    view abstract10.1021/acs.jced.9b00884
  • Measurement and Modeling of Lactose Solubility in Aqueous Electrolyte Solutions
    Choscz, C. and Held, C. and Eder, C. and Sadowski, G. and Briesen, H.
    Industrial and Engineering Chemistry Research 58 (2019)
    Lactose solubility has a significant influence on lactose crystallization. Changes in lactose solubility have an immediate impact on saturation concentration and hence supersaturation, which is used to control the crystallization process. The possibility to model and predict changes in solubility, which are caused by electrolytes, provides a chance to optimize the crystallization processes accordingly. This study explores the influence of different whey salts and salt mixtures on lactose solubility in aqueous solutions. Temperatures from 20 to 50 °C in combination with different salt concentrations are studied. Furthermore, a semipredictive modeling approach using the ePC-SAFT model is presented based on the experimental results. This approach requires pure-component parameters for lactose, dissociated ions, and water, as well as binary interaction parameters for lactose-water, water-ion, and lactose-ion, the latter of which were fitted to lactose solubility data in ternary water-lactose-salt solutions. These parameters have then been applied to successfully predict lactose solubility in multicomponent salt solutions. Until now, a modeling approach for the systems under investigation has not existed in the literature. Copyright © 2019 American Chemical Society.
    view abstract10.1021/acs.iecr.9b04031
  • Melting properties of peptides and their solubility in water. Part 1: Dipeptides based on glycine or alanine
    Do, H.T. and Chua, Y.Z. and Habicht, J. and Klinksiek, M. and Hallermann, M. and Zaitsau, D. and Schick, C. and Held, C.
    RSC Advances 9 (2019)
    Melting properties (melting temperature, melting enthalpy and heat capacity difference between liquid and solid phase) of biomolecules are indispensable for natural and engineering sciences. The direct determination of these melting properties by using conventional calorimeters for biological compounds is often not possible due to decomposition during slow heating. In the current study this drawback is overcome by using fast scanning calorimetry (FSC) to directly measure the melting properties of five dipeptides (glycyl-glycine, glycyl-l-alanine, l-alanyl-glycine, l-alanyl-l-alanine and cyclo(l-alanyl-glycine)). The experimental melting properties were used as inputs into a thermodynamic solid-liquid equilibrium relation to predict solubility of the dipeptides in water. The required activity coefficients were predicted with PC-SAFT using solubility-independent model parameters. PC-SAFT predicted different solubility profiles (solubility vs. temperature) of isomers. The predictions were validated by new experimental solubility data, and the crystal structure of the dipeptides in saturated solution was verified by X-ray diffraction. The different water solubility profiles of isomers (glycyl-l-alanine and l-alanyl-glycine) were found to be caused by the big difference in the melting enthalpy of the two dipeptides. To conclude, combining the PC-SAFT and FSC methods allows for accurate prediction of dipeptide solubility in water in a wide temperature range without the need to fit any model parameters to experimental solubility data. This journal is © The Royal Society of Chemistry.
    view abstract10.1039/c9ra05730g
  • Modeling Thermodynamic Derivative Properties and Gas Solubility of Ionic Liquids with ePC-SAFT
    Sun, Y. and Schemann, A. and Held, C. and Lu, X. and Shen, G. and Ji, X.
    Industrial and Engineering Chemistry Research 58 (2019)
    In this work, the ion-specific electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) was extended to predict the second-order thermodynamic derivative properties and gas solubility of the ionic liquids (ILs) containing one of the IL cations ([C n mim] + , [C n py] + , [C n mpy] + , [C n mpyr] + , and [THTDP] + ) and one of the IL anions ([Tf 2 N] - , [PF 6 ] - , [BF 4 ] - , [tfo] - , [DCA] - , [SCN] - , [C 1 SO 4 ] - , [C 2 SO 4 ] - , [eFAP] - , Cl - , [Ac] - , and Br - ). The ideal-gas isobaric heat capacities of ILs were estimated by the group contribution method for obtaining the heat capacity. The model prediction results were compared with the available experimental data, and the comparison shows that the ePC-SAFT prediction is reliable for most ILs. Furthermore, one adjustable ion-specific binary interaction parameter between the IL ion and CO 2 can be used to further improve the model prediction performance for the CO 2 solubility in ILs. © 2019 American Chemical Society.
    view abstract10.1021/acs.iecr.9b00254
  • Predicting the high concentration co-solvent influence on the reaction equilibria of the ADH-catalyzed reduction of acetophenone
    Wangler, A. and Loll, R. and Greinert, T. and Sadowski, G. and Held, C.
    Journal of Chemical Thermodynamics 128 (2019)
    The use of co-solvents for the enhancement of the reaction parameters reaction rate, yield and enantioselectivity is an established optimization strategy in biotechnology. To determine the influence of co-solvents on even one of these reaction parameters requires a great amount of experimental data. Thus, predictive and physically sound models are desired to decrease the amount of experimental effort. This work aims at providing such a framework, which was applied to the ADH (alcohol dehydrogenase)-catalyzed reduction of acetophenone at 303.15 K and 1 bar in water (neat) and under the influence of up to 20 wt-% of polyethylene glycol (PEG) and 15 wt-% trisodium citrate (Na3Cit). In a first step, the equilibrium composition was measured at constant pH. It was then shown that high concentration of PEG or Na3Cit changed the equilibrium position significantly (up to a factor of 13) compared to neat reaction mixtures. To be able to predict this strong co-solvent influence on the reaction equilibrium, the experimentally determined equilibrium compositions of the neat reaction were converted into a thermodynamic equilibrium constant Kth using the activity coefficients γi of the reacting agents. The latter were predicted by electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC–SAFT). These finally allowed quantitatively predicting the high concentration co-solvent influence on the equilibrium position. © 2018 Elsevier Ltd
    view abstract10.1016/j.jct.2018.08.021
  • Simultaneous Prediction of Cosolvent Influence on Reaction Equilibrium and Michaelis Constants of Enzyme-Catalyzed Ketone Reductions
    Wangler, A. and Hüser, A. and Sadowski, G. and Held, C.
    ACS Omega 4 (2019)
    Understanding and quantification of cosolvent influences on enzyme-catalyzed reactions are driven by a twofold interest. On the one hand, cosolvents can simulate the cellular environment for deeper understanding of in cellulo reaction conditions. On the other hand, cosolvents are applied in biotechnology to tune yield and kinetics of reactions. Further, cosolvents are even present inherently, for example, for reactions with cofactor regeneration or for enzymes that need cosolvents in a function of a stabilizer. As the experimental determination of yield and kinetics is costly and time consuming, this work aims at providing a thermodynamic predictive approach that might allow screening cosolvent influences on yield and Michaelis constants. Reactions investigated in this work are the reduction of butanone and 2-pentanone under the influence of 17 wt % of the cosolvent polyethylene glycol 6000, which is also often used as a crowder to simulate cellular environments. The considered reactions were catalyzed by a genetically modified alcohol dehydrogenase (ADH 270). Predictions of cosolvent influences are based on accounting for a cosolvent-induced change of molecular interactions among the reacting agents as well as between the reacting agents and the solvent. Such interactions were characterized by activity coefficients of the reacting agents that were predicted by means of electrolyte perturbed-chain statistical associating fluid theory. This allowed simultaneously predicting the cosolvent effects on yield and Michaelis constants for two-substrate reactions for the first time. © 2019 American Chemical Society.
    view abstract10.1021/acsomega.8b03159
  • Solubility Enhancement of Vitamins in Water in the Presence of Covitamins: Measurements and ePC-SAFT Predictions
    Wysoczanska, K. and MacEdo, E.A. and Sadowski, G. and Held, C.
    Industrial and Engineering Chemistry Research 58 (2019)
    Scarce knowledge on the behavior of vitamins in aqueous solutions in the presence of additives is often a limiting factor for industrial applications such as process design and optimization. Knowing the pH-solubility profiles of vitamins is fundamental for understanding and controlling their behavior in aqueous solutions. In the present work, pH-dependent solubilities of the vitamins ascorbic acid (VC), riboflavin (VB2), nicotinic acid (VB3acid), folic acid (VB9), and cyanocobalamin (VB12) were measured at T = 298.15 K and p = 1 bar. These results were compared to the pH-solubility profiles obtained with modified Henderson-Hasselbalch equations using pKa values from the literature. Further, the solubilities of poorly soluble VB2, VB9, and VB12 were increased by the addition of covitamins VC, VB3acid, and nicotinamide (VB3amide). As observed, VB3amide increases the vitamin solubility much stronger than VC and VB3acid. These covitamins are called "hydrotropes" in several works in the literature, and they increase the solubility of other vitamins by manipulating the pH of the saturated solutions and by molecular cross-interactions. The interplay between both pH and cross-interactions depends strongly on the kind and concentration of covitamin. At low concentrations, VC and VB3amide (<0.2 m) increased solubility by pH change. At higher concentrations of VC and VB3amide added, mainly cross-interactions between vitamin and covitamin determine the strength of solubility increase. To separate these effects and to further reduce experimental effort, electrolyte perturbed-chain statistical association fluid theory was used to predict vitamin solubility. The pH-solubility profiles and the solubilities of vitamins in water at T = 298.15 K and p = 1 bar upon addition of covitamins were predicted with reasonable accuracy. This success resulted from accounting for different charged and neutral vitamin species according to the pH and from considering explicitly the vitamin-water and vitamin-covitamin interactions. It could be shown that "hydrotropic solubilization" of a vitamin is the increase of vitamin solubility caused by pH shift and by cross-interactions between the saturated species of a vitamin and the added covitamin. Copyright © 2019 American Chemical Society.
    view abstract10.1021/acs.iecr.9b04302
  • Structure and thermodynamics of aqueous urea solutions from ambient to kilobar pressures: From thermodynamic modeling, experiments, and first principles simulations to an accurate force field description
    Hölzl, C. and Kibies, P. and Imoto, S. and Noetzel, J. and Knierbein, M. and Salmen, P. and Paulus, M. and Nase, J. and Held, C. and Sadowski, G. and Marx, D. and Kast, S.M. and Horinek, D.
    Biophysical Chemistry 254 (2019)
    Molecular simulations based on classical force fields are a powerful method for shedding light on the complex behavior of biomolecules in solution. When cosolutes are present in addition to water and biomolecules, subtle balances of weak intermolecular forces have to be accounted for. This imposes high demands on the quality of the underlying force fields, and therefore force field development for small cosolutes is still an active field. Here, we present the development of a new urea force field from studies of urea solutions at ambient and elevated hydrostatic pressures based on a combination of experimental and theoretical approaches. Experimental densities and solvation shell properties from ab initio molecular dynamics simulations at ambient conditions served as the target properties for the force field optimization. Since urea is present in many marine life forms, elevated hydrostatic pressure was rigorously addressed: densities at high pressure were measured by vibrating tube densitometry up to 500 bar and by X-ray absorption up to 5 kbar. Densities were determined by the perturbed-chain statistical associating fluid theory equation of state. Solvation properties were determined by embedded cluster integral equation theory and ab initio molecular dynamics. Our new force field is able to capture the properties of urea solutions at high pressures without further high-pressure adaption, unlike trimethylamine-N-oxide, for which a high-pressure adaption is necessary. © 2019
    view abstract10.1016/j.bpc.2019.106260
  • Thermodynamic Activity-Based Solvent Design for Bioreactions
    Wangler, A. and Held, C. and Sadowski, G.
    Trends in Biotechnology 37 (2019)
    To improve the kinetics of enzyme-catalyzed reactions, cosolvents are commonly added to reaction mixtures. The search for a good cosolvent is still empirical and experimentally based. We discuss a thermodynamic activity-based approach that improves biocatalytic processes by predicting cosolvent influences on Michaelis constants, ultimately reducing time and cost. © 2019 Elsevier Ltd
    view abstract10.1016/j.tibtech.2019.04.015
  • Thermodynamic properties of aqueous osmolyte solutions at high-pressure conditions
    Knierbein, M. and Venhuis, M. and Held, C. and Sadowski, G.
    Biophysical Chemistry 253 (2019)
    Living organisms can be encountered in nature under extreme conditions. At the seabed, pressure may reach 1000 bar. Yet microorganisms can be found that still function under these conditions. On the one hand, it is known that high pressure even has a positive effect on piezophile enzymes increasing their activity. On the other hand, such microorganisms might contain up to very high concentrations of osmolytes that counteract osmotic stress. To better understand high-pressure influences on biochemical systems, fundamental knowledge about pressure effects on thermodynamic properties of such osmolytes is important. However, literature data is scarce and experiments at high-pressure conditions are challenging. Hence, new high-pressure density data of aqueous osmolyte solutions were measured in this work at temperatures between 298.15 K and 318.15 K and at osmolyte concentrations up to 3 mol/kg water. Further, the thermodynamic model PC-SAFT has been applied recently to successfully model vapor pressures of water and density of water up to 10 kbar [M. Knierbein et al., Density variations of TMAO solutions in the kilobar range: experiments, PC-SAFT predictions, and molecular dynamics simulations, Biophysical chemistry, (2019)]. This allowed accurately predicting effects of temperature and osmolyte concentration on thermodynamic properties (especially mixture densities) up to very high pressures. Common osmolytes (trimethylamine-N-oxide, urea, ectoine, glycerol, glycine) as well as the dipeptides acetyl-N-methylglycine amide, acetyl-N-methylalanine amide, and acetyl-N-methylleucine amide were under investigation. © 2019
    view abstract10.1016/j.bpc.2019.106211
  • Thermodynamic properties of hydrophobic deep eutectic solvents and solubility of water and HMF in them: Measurements and PC-SAFT modeling
    Dietz, C.H.J.T. and Erve, A. and Kroon, M.C. and van Sint Annaland, M. and Gallucci, F. and Held, C.
    Fluid Phase Equilibria 489 (2019)
    Recently, hydrophobic deep eutectic solvents (DESs) were proposed as interesting solvents for biorefinery processes, such as the production of 5-hydroxymethylfurfural (HMF) from glucose in an aqueous environment. Physicochemical property data of hydrophobic DES + water/HMF systems are of utmost importance for process design. In this work, density and vapor pressure of eight different hydrophobic DESs, as well as water solubility and HMF solubility in these DESs were experimentally determined. The solubility was modeled using the pseudo-pure component approach within the framework of Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). New pure-component parameters for the eight hydrophobic DESs were obtained by fitting to measured density and vapor-pressure data, instead of to density data only. Based on these new pure-component parameters for the DESs, the solubilities of water and of HMF in the hydrophobic DESs were modeled in good agreement with the experimental data at 298 K and atmospheric pressure. © 2019 Elsevier B.V.
    view abstract10.1016/j.fluid.2019.02.010
  • Thermodynamic Properties of Systems Comprising Esters: Experimental Data and Modeling with PC-SAFT and SAFT-γMie
    Haarmann, N. and Siewert, R. and Samarov, A.A. and Verevkin, S.P. and Held, C. and Sadowski, G.
    Industrial and Engineering Chemistry Research 58 (2019)
    In this work, new experimental vapor-pressure data of 14 esters were obtained using the transpiration method. Besides dimethyl fumarate, dimethyl maleate, diethyl maleate, benzyl ethanoate, benzyl propanoate, and benzyl butanoate, eight representatives of the homologous series of ethyl alkanoates were investigated. The pure-component vapor pressures and liquid densities were modeled by means of Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) and SAFT-γMie. Satisfying modeling results could be achieved with both equations of state. Furthermore, the molar excess enthalpies of 12 binary mixtures benzyl ethanoate + n-alkane were modeled. Only one binary interaction parameter was fitted for PC-SAFT to quantitatively predict the molar excess enthalpies of all binary mixtures under study, while SAFT-γMie predicts these properties in qualitative agreement with the experimental data. Finally, the liquid-liquid equilibria of three binary mixtures ester (benzyl ethanoate, dimethyl maleate, and diethyl maleate) + water were investigated. These systems show a very low and almost temperature-independent solubility of the ester in the aqueous phase, whereas the moderate solubility of water in the organic phase is temperature-dependent. Promisingly, both PC-SAFT and SAFT-γMie predicted broad and unsymmetrical miscibility gaps for these mixtures, which is in qualitative agreement with the experimental data. © 2019 American Chemical Society.
    view abstract10.1021/acs.iecr.9b00714
  • Thermophysical properties of glyceline-water mixtures investigated by molecular modelling
    Baz, J. and Held, C. and Pleiss, J. and Hansen, N.
    Physical Chemistry Chemical Physics 21 (2019)
    The effect of water content on the static and dynamic properties of the deep eutectic solvent glyceline is studied using molecular dynamics (MD) simulations. Static properties are additionally calculated using the PC-SAFT equation of state. Force fields calibrated on water-free glyceline show predictive power for density and water activity over the entire composition range. In contrast, the PC-SAFT approach using pseudo one-component or two-component modelling strategies performed better for the density or the water activity, respectively. The MD simulations show that at low water content, the hydrogen-bond network between glycerol molecules as well as between glycerol and the cholinium cation is hardly affected by the water molecules while at higher water content, glycerol-glycerol hydrogen bonds are replaced by glycerol-water hydrogen bonds indicating the formation of an aqueous solution accompanied by a strong decrease of the shear viscosity. At the same time, the thermodynamic activity of water increases such that the MD simulations are able to guide the optimal composition with respect to requirements in biocatalytic applications such as low viscosity and low water activity. The combined application of PC-SAFT to efficiently predict static properties and molecular dynamics simulations to predict static and dynamic properties offers a powerful framework in solvent design applications. © 2019 the Owner Societies.
    view abstract10.1039/c9cp00036d
  • Toward Thermodynamic Predictions of Aqueous Vitamin Solubility: An Activity Coefficient-Based Approach
    Wysoczanska, K. and Sadowski, G. and Macedo, E.A. and Held, C.
    Industrial and Engineering Chemistry Research 58 (2019)
    Research on water-soluble vitamins is still required, especially due to the diversity of their structures that influence strongly physicochemical properties of water-vitamin mixtures. Such influences are still underexplored. Further, solubility of vitamins in aqueous environment is of crucial importance for life sciences and process design, but still experimental data of vitamin solubility is rather limited in literature. In this work, solubilities of the vitamins ascorbic acid, riboflavin, nicotinic acid, folic acid, and cyanocobalamin were predicted with Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). PC-SAFT parameters for vitamins were estimated by fitting them to solubility-independent data, namely experimental liquid-density data and osmotic-coefficient data of aqueous vitamin solutions measured in this work. PC-SAFT predicted solubilities were validated by new experimental solubility data at T = 298.15 K and p = 1 bar. PC-SAFT predictions were in quantitative agreement to experimental vitamin solubility in water. Further, PC-SAFT allowed predicting the temperature influence on the solubility of vitamins in water with reasonable accuracy. © 2019 American Chemical Society.
    view abstract10.1021/acs.iecr.9b00742
  • Co-solvent effects on reaction rate and reaction equilibrium of an enzymatic peptide hydrolysis
    Wangler, A. and Canales, R. and Held, C. and Luong, T.Q. and Winter, R. and Zaitsau, D.H. and Verevkin, S.P. and Sadowski, G.
    Physical Chemistry Chemical Physics 20 (2018)
    This work presents an approach that expresses the Michaelis constant KaM and the equilibrium constant Kth of an enzymatic peptide hydrolysis based on thermodynamic activities instead of concentrations. This provides KaM and Kth values that are independent of any co-solvent. To this end, the hydrolysis reaction of N-succinyl-l-phenylalanine-p-nitroanilide catalysed by the enzyme α-chymotrypsin was studied in pure buffer and in the presence of the co-solvents dimethyl sulfoxide, trimethylamine-N-oxide, urea, and two salts. A strong influence of the co-solvents on the measured Michaelis constant (KM) and equilibrium constant (Kx) was observed, which was found to be caused by molecular interactions expressed as activity coefficients. Substrate and product activity coefficients were used to calculate the activity-based values KaM and Kth for the co-solvent free reaction. Based on these constants, the co-solvent effect on KM and Kx was predicted in almost quantitative agreement with the experimental data. The approach presented here does not only reveal the importance of understanding the thermodynamic non-ideality of reactions taking place in biological solutions and in many technological applications, it also provides a framework for interpreting and quantifying the multifaceted co-solvent effects on enzyme-catalysed reactions that are known and have been observed experimentally for a long time. © the Owner Societies.
    view abstract10.1039/c7cp07346a
  • Effect of different organic salts on amino acids partition behaviour in PEG-salt ATPS
    Wysoczanska, K. and Do, H.T. and Held, C. and Sadowski, G. and Macedo, E.A.
    Fluid Phase Equilibria 456 (2018)
    The phase diagrams of six different polyethylene glycol (PEG)–salt aqueous two-phase systems (ATPS) were measured at T = 298.15 K and p = 1 bar. PEG of different molecular weight (4000, 6000 and 8000) and organic salts (potassium citrate, potassium sodium tartrate) were used to form the biphasic systems. The results were compared with data for PEG–sodium citrate ATPS, reported in the literature (PEG 4000, PEG 6000) and measured in this work (PEG 8000). The partition of four dinitrophenyl-amino acids was measured in these ATPS for different tie-line lengths. Based on these data, cation and anion effects were evaluated in terms of the relative hydrophobicity of the phases using ΔG*(CH2) calculations. The distribution coefficients have been obtained spectrophotometrically. Studies on the partitioning indicate the advantage of citrate salts over tartrate salts as well as sodium-based salts over potassium-based salts. This consistently results from the (liquid-liquid) phase behaviour of these systems. © 2017 Elsevier B.V.
    view abstract10.1016/j.fluid.2017.10.007
  • Light-scattering data of protein and polymer solutions: A new approach for model validation and parameter estimation
    Voges, M. and Herhut, M. and Held, C. and Brandenbusch, C.
    Fluid Phase Equilibria 465 (2018)
    The development of separation processes for polymers or proteins from aqueous solutions requires a high amount of experimental effort, including phase-equilibrium data such as solid-liquid, liquid-liquid or vapor-liquid equilibria. This effort can be reduced by means of thermodynamic models. This work presents a new method for parameter estimation and validation of thermodynamic models by means of static-light-scattering (SLS) measurements. In this work the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to predict directly the SLS data (Rayleigh ratio) of macromolecular solutions. In a first step, SLS data were measured for binary water/polyethylene glycol (PEG molecular weight ranging from 2000 to 12000 g/mol) mixtures and for binary water/lysozyme mixtures. Applying pure-component PC-SAFT parameters from literature, the SLS data of these binary mixtures were successfully predicted with PC-SAFT. In a second step, one binary interaction parameter between lysozyme and PEG was adjusted to new experimental SLS data of buffered PEG/lysozyme/water solutions with PEG6000 concentration of 20 g/L. Finally, SLS data for buffered ternary PEG/lysozyme/water solutions with PEG of different molecular weights (2000–12000 g/mol) and different concentrations (1–50 g/L) were accurately predicted with PC-SAFT. Thus, (1) the proposed approach allows predicting SLS data, and (2) the method provides an access to the estimation of model parameters by means of experimental SLS data, which are accessible with much less effort than experimental phase-equilibrium data. © 2018 Elsevier B.V.
    view abstract10.1016/j.fluid.2018.02.022
  • Measuring and modeling thermodynamic properties of aqueous lysozyme and BSA solutions
    Hübner, M. and Lodziak, C. and Do, H.T.J. and Held, C.
    Fluid Phase Equilibria 472 (2018)
    A novel approach towards modeling proteins in aqueous solutions by applying perturbed-chain statistical associating fluid theory (PC-SAFT) is proposed in this work. Lysozyme and bovine serum albumin (BSA) were chosen as model proteins due to a vast database available in literature. However, the huge majority of these literature data had been measured at certain ionic strengths, which is disadvantageous in order to derive pure-component parameters for proteins. Thus, in a first step within this work osmotic coefficients of dialyzed lysozyme and of dialyzed BSA in pure water were measured at 298.15 K. The data were very different for dialyzed and non-dialyzed solutions and further showed a strong dependence on pH and ionic strength. In a second step, the pure-component parameters of lysozyme and BSA were adjusted to the measured osmotic coefficients and to solution densities of dialyzed lysozyme or dialyzed BSA. PC-SAFT explicitly takes into account the complex association behavior between protein and water as well as among the proteins. Therefore, the number of protein association sites of one protein was determined from the sum of association sites of the single amino-acid constituents of a protein available from previous work (Ind. Eng. Chem. Res 50 (2011) 141–151). Similarly, the two PC-SAFT parameters “segment number” and “segment diameter” of a protein were summed or averaged from the single amino-acid constituents. This approach allowed modeling densities and osmotic coefficients of protein solutions with reasonable accuracy compared to experimental data. © 2018 Elsevier B.V.
    view abstract10.1016/j.fluid.2018.04.027
  • Modeling Viscosity of Ionic Liquids with Electrolyte Perturbed-Chain Statistical Associating Fluid Theory and Free Volume Theory
    Sun, Y. and Shen, G. and Held, C. and Feng, X. and Lu, X. and Ji, X.
    Industrial and Engineering Chemistry Research 57 (2018)
    Viscosity is one of the most important physical properties when developing ionic liquids (ILs) for industrial applications such as CO2 separation. The viscosities of ILs have been measured experimentally, while the modeling work is still limited. In this work, the electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) was combined with the free volume theory (FVT) to model the viscosities of pure ILs and IL mixtures up to high pressures and temperatures, in which the ePC-SAFT was used to calculate the density as inputs for modeling the viscosity of ILs with FVT. The ILs under consideration contain one of the IL cations [Cnmim]+, [Cnpy]+, [Cnmpy]+, [Cnmpyr]+, or [THTDP]+ and one of the IL anions [Tf2N]-, [PF6]-, [BF4]-, [tfo]-, [DCA]-, [SCN]-, [C1SO4]-, [C2SO4]-, [eFAP]-, Cl-, [Ac]-, or Br-. In total, 89 ILs were considered combined with a thorough literature survey of the available experimental viscosity data and evaluation. The comparison with the available experimental viscosities shows that the model can provide reliable representation and prediction for most of the pure ILs in a wide temperature and pressure range, and it can be further used to predict and describe the viscosity of IL mixtures reliably. Copyright © 2018 American Chemical Society.
    view abstract10.1021/acs.iecr.8b00328
  • Mutual Influence of Furfural and Furancarboxylic Acids on Their Solubility in Aqueous Solutions: Experiments and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) Predictions
    Rose, H.B. and Greinert, T. and Held, C. and Sadowski, G. and Bommarius, A.S.
    Journal of Chemical and Engineering Data 63 (2018)
    Furan compounds are of mounting global interest due to their biorenewable nature and their potential to replace petroleum-based compounds as feedstocks in manufacturing. In this work the solubilities of furfural and the furancarboxylic acids 2-furoic acid (FA), 5-formyl-2-furancarboxylic acid (FFA), and 2,5-furandicarboxylic acid (FDCA) in aqueous solutions and organic solvents were investigated experimentally and by modeling with perturbed-chain statistical associating fluid theory (PC-SAFT). The PC-SAFT pure-component parameters of the solutes FA, FFA, and FDCA and one binary parameter between each solute and each solvent were adjusted to fit experimentally determined solubilities of each solute in each organic solvent or in water. Pure-component parameters of furfural were fitted to experimental density data and vapor-pressure data, and a binary interaction parameter was fitted to capture the solubility behavior of furfural in water. Modeling of pH effects enhanced predictions of the mutual influences of the acids on their solubilities in ternary aqueous systems. Mutual solubility influences of furfural and the furancarboxylic acids were accurately modeled with one constant binary parameter for the acid-furfural mixtures. All PC-SAFT modeling results were validated with new experimental solubility data at 35 °C, which were measured by HPLC analysis of equilibrated saturated solutions. © 2018 American Chemical Society.
    view abstract10.1021/acs.jced.7b01039
  • New experimental melting properties as access for predicting amino-acid solubility
    Chua, Y.Z. and Do, H.T. and Schick, C. and Zaitsau, D. and Held, C.
    RSC Advances 8 (2018)
    The properties of melting are required for the prediction of solubility of solid compounds. Unfortunately, direct determination of the enthalpy of fusion and melting temperature by using conventional DSC or adiabatic calorimetry is often not possible for biological compounds due to decomposition during the measurement. To overcome this, fast scanning calorimetry (FSC) with scanning rates up to 2 × 104 K s-1 was used in this work to measure the melting parameters for l-alanine and glycine. The enthalpy of fusion and melting temperature (extrapolated to zero heating rate) were ΔfusH = (22 ± 5) kJ mol-1 and Tfus = (608 ± 9) K for l-alanine, and ΔfusH = (21 ± 4) kJ mol-1 and Tfus = (569 ± 7) K for glycine. These melting properties were used in the modeling framework PC-SAFT to predict amino-acid solubility in water. The pure-component PC-SAFT parameters and one binary parameter were taken from literature, in which these parameters were fitted to solubility-independent thermodynamic properties such as osmotic coefficients or mixture densities. It was shown that this allowed accurately predicting amino-acid solubility in water over a broad temperature range. The combined methodology of PC-SAFT and FSC proposed in this work opens the door for predicting solubility of molecules that decompose before melting. © The Royal Society of Chemistry 2018.
    view abstract10.1039/c8ra00334c
  • Oil desulfurization using deep eutectic solvents as sustainable and economical extractants via liquid-liquid extraction: Experimental and PC-SAFT predictions
    Warrag, S.E.E. and Pototzki, C. and Rodriguez, N.R. and van Sint Annaland, M. and Kroon, M.C. and Held, C. and Sadowski, G. and Peters, C.J.
    Fluid Phase Equilibria 467 (2018)
    The reduction of the sulfur content in crude oil is of utmost importance in order to meet the stringent environmental regulations. Thiophene and its derivatives are considered key substances to be separated from the crude oil. In previous works, six deep eutectic solvents (DESs) based on tetraethylammonium chloride, tetrahexylammonium bromide and methyltriphenylphosphonium bromide as hydrogen bond acceptors (HBAs) and polyols (ethylene glycol and glycerol) as hydrogen bond donors (HBDs) were successfully applied for the extraction of thiophene from {n-alkane + thiophene} mixtures via liquid-liquid extraction. One of the objectives of this work was to study the effect of the aliphatic hydrocarbon type/length (e.g. n-hexane vs n-octane) on the extraction performance of the same DESs. Extraction performance was evaluated by the selectivity and the thiophene distribution coefficient. Based on new experimental data, higher selectivities and lower thiophene distribution coefficients were obtained when thiophene was extracted from n-octane instead of n-hexane. Another objective was to predict the phase behavior of the ternary systems {n-alkane + thiophene + DES} using Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). The PC-SAFT “pseudo-pure component” approach was applied, in which a DES was considered as a pseudo-pure compound (not a mixture). The pure-component parameters of the DESs were obtained by fitting to liquid density data, which were measured at temperatures between 298.2 K and 323.2 K. Binary interaction parameters were fitted to experimental binary LLE data for the systems {n-alkane + DES} and {thiophene + DES} at 298.2 K and atmospheric pressure, while the LLE data of the ternary systems {n-alkane + thiophene + DES} were fully predicted. It was found that the distribution coefficients and selectivity of the ternary systems containing DESs could be qualitatively well predicted using this model. © 2018 Elsevier B.V.
    view abstract10.1016/j.fluid.2018.03.018
  • Prediction and Experimental Validation of Co-Solvent Influence on Michaelis Constants: A Thermodynamic Activity-Based Approach
    Wangler, A. and Böttcher, D. and Hüser, A. and Sadowski, G. and Held, C.
    Chemistry - A European Journal 24 (2018)
    Co-solvents are known to influence the Michaelis constant KM of enzyme-catalyzed reactions. In the literature, co-solvent effects on KM are usually explained by interactions between enzyme and co-solvent. Very recent works replaced substrate concentrations with thermodynamic activities to separate enzyme–co-solvent from substrate–co-solvent interactions This yields the thermodynamic-activity-based Michalis constant Ka M. In this work, this approach was extended to alcohol dehydrogenase (ADH)-catalyzed reduction of acetophenone (ACP), a two-substrate reaction. It was experimentally found that polyethylene glycol (PEG) 6000 increased KM of ACP and decreased KM of nicotinamide adenine dinucleotide (NADH). To predict Ka M values, non-covalent interactions between substrates and reaction media were taken into account by electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) modelling. In contrast to experimental KM values, their activity-based pendants Ka M were independent of co-solvent. To further verify the approach, the reduction of 2-pentanone catalyzed by the same ADH was investigated. Interestingly, the addition of PEG caused a decrease of both KM of 2-pentanone and KM of NADH. Based on Ka M values obtained from in co-solvent-free conditions and activity coefficients from ePC-SAFT, the influence of the co-solvent on KM was quantitatively predicted. Thus, the approach known for pseudo one-substrate reactions was successfully transferred to two-substrate reactions. Furthermore, the advantage of thermodynamic activities over concentrations in the field of enzyme kinetics is highlighted. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/chem.201803573
  • Prediction of CO2 and H2S solubility and enthalpy of absorption in reacting N-methyldiethanolamine /water systems with ePC-SAFT
    Wangler, A. and Sieder, G. and Ingram, T. and Heilig, M. and Held, C.
    Fluid Phase Equilibria 461 (2018)
    The major goal of this work was the prediction of the solubility of CO2 and H2S in aqueous methyldiethanolamine (MDEA) reacting systems using the electrolyte equation of state ePC-SAFT with focus on MDEA weight fractions wMDEA> 0.3 (related to the binary water/MDEA system). Predictions in this work mean that no parameters were adjusted to the experimental gas solubility data in aqueous MDEA solutions. In order to obtain improved prediction results compared to state-of-the-art literature models, binary interaction parameters kij between water-MDEAH+, water-HCO3 −, and water-HS− were introduced; these kij values were fitted to osmotic-coefficient data measured in this work and from literature. This new possibility to access these kij parameters allowed improved predictions of CO2 solubility, and the predictions were validated by new experimental data at wMDEA = 0.6. Even more, the influence of the inert gas CH4 on CO2 solubility was predicted reasonably correct. Further, the solubility of H2S in aqueous MDEA solutions was accurately predicted in the temperature range 298 K < T < 393 K at wMDEA = 0.32 and 0.48. In the final part of this work enthalpy of absorption was predicted for 353 K < T < 393 K at wMDEA = 0.3 for varying gas loadings. In summary, prediction results were satisfying considering the fact that ePC-SAFT parameters were fitted only to experimental data of pure fluids or binary systems. © 2018 Elsevier B.V.
    view abstract10.1016/j.fluid.2017.12.033
  • Renewable platform chemicals: Thermochemical study of levulinic acid esters
    Emel'yanenko, V.N. and Altuntepe, E. and Held, C. and Pimerzin, A.A. and Verevkin, S.P.
    Thermochimica Acta 659 (2018)
    Equilibrium of the levulinic acid esterification with methanol, ethanol, and 1-butanol was studied in a broad temperature range (323 K–473 K) for reactions catalyzed by the enzyme Novozym 435 as well as for uncatalysed reaction systems. Thermodynamic equilibrium constants were derived with help of activity coefficients of reaction participants, which were predicted with the equation of state PC-SAFT. The liquid phase standard molar enthalpies of formation of methyl-, ethyl-, and n-butyl-esters of levulinic acid were measured by using the high-precision combustion calorimetry. Vapor pressures of these esters were measured by using the transpiration method. The standard molar enthalpies of vaporization of alkyl levulinates at 298.15 K were derived from vapor pressure temperature dependencies. Thermochemical data of alkyl levulinates were collected, evaluated, and tested for internal consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas phase enthalpies of formation of studied esters. Thermodynamic analysis of the levulinic acid esterification has been performed. Using the levulinic acid esterification with alcohols as the model reaction for an industrial processing of biomass conversion to fuels and useful platform chemicals, we have shown that qualitatively correct agreement between results from equilibrium study, from thermochemical data (combustion and transpiration), and from G4 calculations was observed. Reasonable combination of the quantum-chemical methods and of PC-SAFT modelling with empirical methods could serve to reduce experimental efforts for assessment of feasibility of the chemical processes of utilization of renewable feedstocks. © 2017 Elsevier B.V.
    view abstract10.1016/j.tca.2017.12.006
  • Solubility predictions of acetanilide derivatives in water: Combining thermochemistry and thermodynamic modeling
    Held, C. and Brinkmann, J. and Schröder, A.-D. and Yagofarov, M.I. and Verevkin, S.P.
    Fluid Phase Equilibria 455 (2018)
    Knowledge about solubility in water is required for crystallization processes, for the development of structure-property relationships, for the establishment of solubility scales, assessing environmental contamination, and for validating thermodynamic models. Approaches are desired that allow predicting solubility without the use of any experimental solubility data. Most methods that have been proposed to predict aqueous solubility of organic compounds face low prediction reliability and the lack of model interpretability. This work proposes the use of a thermodynamic approach for the prediction of solubility of acetanilide and its derivatives in water. This approach requires fusion enthalpy and fusion temperature as well as the activity coefficient of the respective acetanilide derivative. The latter was obtained by the equation of state PC-SAFT, which uses thermochemistry data as input for model parametrization. The thermochemical data on acetanilide and its derivatives (vapor and sublimation pressures, sublimation and fusion enthalpies) were collected from the literature and evaluated for internal consistency. In order to validate the final solubility prediction model, aqueous solubility of acetanilide and 17 derivatives were predicted and compared to experimental solubility data from literature at 298.15 K as well as to an ideal solubility model, which assumes ideal mixture behavior. The results showed that mixtures of acetanilides + water are highly non-ideal, and the average deviations between solubility data and ideal solubility model could be reduced by two orders of magnitude by using PC-SAFT for the solubility predictions. More promising, PC-SAFT was found to allow predicting the temperature dependence of the aqueous solubility accurately, while ideal solubility model failed to quantitatively describe temperature-dependent solubility. © 2017 Elsevier B.V.
    view abstract10.1016/j.fluid.2017.09.023
  • Standard Gibbs Energy of Metabolic Reactions: III the 3-Phosphoglycerate Kinase Reaction
    Wangler, A. and Schmidt, C. and Sadowski, G. and Held, C.
    ACS Omega 3 (2018)
    The glycolytic pathway is one of the most studied metabolic pathways to date. This work focuses on determining the standard Gibbs energy of reaction (δRg0) of the first adenosine triphosphate-yielding reaction step of glycolysis, namely, the 3-phosphoglycerate kinase (PGK) reaction. Trustworthy values of δRg0 are required for thermodynamic approaches to determine single reaction conversions or even fluxes of metabolic reactions. In literature, the observed δRg0,obs values are usually determined directly from the experimental equilibrium composition data without accounting for the nonideality of the reaction mixture. That is the reason why the observed δRg0,obs values do not present consistent standard data as they are a function of the concentration, pH, and pMg. In this work, a combination of experimentally determined equilibrium composition data and activity coefficients of the reacting agents was used to determine δRg0 values for the temperatures 303, 313, and 323 K at pH 7. The activity coefficients were predicted with the thermodynamic model electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT). The ePC-SAFT parameters were taken from literature or fitted to new experimental osmotic coefficients. At 313.15 K, a value for δRg0 of -16.2 ± 0.2 kJ/mol was obtained. This value is about 4 kJ/mol less negative than what is usually considered as an accepted standard value. The reason behind this discrepancy was found to be the activity coefficients of the reacting agents, which dramatically influence the equilibrium position of the PGK reaction. On the basis of the temperature-dependent δRg0 values, the standard enthalpy of reaction was determined and found to be δRh0 = â49 ± 9 kJ/mol. © 2018 American Chemical Society.
    view abstract10.1021/acsomega.7b01704
  • The Role of Polyfunctionality in the Formation of [Ch]Cl-Carboxylic Acid-Based Deep Eutectic Solvents
    Crespo, E.A. and Silva, L.P. and Martins, M.A.R. and Bülow, M. and Ferreira, O. and Sadowski, G. and Held, C. and Pinho, S.P. and Coutinho, J.A.P.
    Industrial and Engineering Chemistry Research 57 (2018)
    Aiming at providing an extensive characterization of the solid-liquid equilibria (SLE) of deep eutectic solvents (DESs), the phase diagrams of nine eutectic mixtures composed of choline chloride ([Ch]Cl) and (poly)carboxylic acids, commonly reported in the literature as DESs, were measured experimentally. Contrarily to the behavior reported for eutectic mixtures composed of [Ch]Cl (hydrogen-bond acceptor, HBA) and monofunctional hydrogen-bond donors (HBD) such as fatty acids and fatty alcohols, which have recently been shown to be almost ideal mixtures, a significant decrease of the melting temperature, at the eutectic point, was observed for most of the systems studied. This melting temperature depression was attributed to a pronounced nonideality of the liquid phase induced by the strong hydrogen-bond interactions between the two mixture components. Perturbed-chain statistical associating fluid theory (PC-SAFT) was used to describe these interactions physically. PC-SAFT allowed accurately modeling the experimental phase diagrams over the entire concentration and temperature ranges. Depending on the kind of mixture, up to two temperature-independent binary interaction parameters between HBA and HBD were applied. The PC-SAFT approach was used to provide trustworthy information on the nonideality of the liquid phase (expressed as the activity coefficients of HBA and HBD) as well as to estimate the eutectic points coordinates. The experimental data along with the modeling results allowed us to infer about the importance of the HBD's chemical structure on the formation of [Ch]Cl-based DESs. © 2018 American Chemical Society.
    view abstract10.1021/acs.iecr.8b01249
  • Thermodynamic properties of selenoether-functionalized ionic liquids and their use for the synthesis of zinc selenide nanoparticles
    Klauke, K. and Zaitsau, D.H. and Bülow, M. and He, L. and Klopotowski, M. and Knedel, T.-O. and Barthel, J. and Held, C. and Verevkin, S.P. and Janiak, C.
    Dalton Transactions 47 (2018)
    Three selenoether-functionalized ionic liquids (ILs) of N-[(phenylseleno)methylene]pyridinium (1), N-(methyl)- (2) and N-(butyl)-N'-[(phenylseleno)methylene]imidazolium (3) with bis(trifluoromethanesulfonyl)imide anions ([NTf2]) were prepared from pyridine, N-methylimidazole and N-butylimidazole with in situ obtained phenylselenomethyl chloride, followed by ion exchange to give the desired compounds. The crystal structures of the bromide and tetraphenylborate salts of the above cations (1-Br, 2-BPh4 and 3-BPh4) confirm the formation of the desired cations and indicate a multitude of different supramolecular interactions besides the dominating Coulomb interactions between the cations and anions. The vaporization enthalpies of the synthesized [NTf2]-containing ILs were determined by means of a quartz-crystal microbalance method (QCM) and their densities were measured with an oscillating U-tube. These thermodynamic data have been used to develop a method for assessment of miscibility of conventional solvents in the selenium-containing ILs by using Hildebrandt solubility parameters, as well as for modeling with the electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) method. Furthermore, structure-property relations between selenoether-functionalized and similarly shaped corresponding aryl-substituted imidazolium- and pyridinium-based ILs were analyzed and showed that the contribution of the selenium moiety to the enthalpy of vaporization of an IL is equal to the contribution of a methylene (CH2) group. An incremental approach to predict vaporization enthalpies of ILs by a group contribution method has been developed. The reaction of these ILs with zinc acetate dihydrate under microwave irradiation led to ZnSe nanoparticles of an average diameter between 4 and 10 nm, depending on the reaction conditions. © The Royal Society of Chemistry 2018.
    view abstract10.1039/c8dt00233a
  • Tunable Hydrophobic Eutectic Solvents Based on Terpenes and Monocarboxylic Acids
    Martins, M.A.R. and Crespo, E.A. and Pontes, P.V.A. and Silva, L.P. and Bülow, M. and Maximo, G.J. and Batista, E.A.C. and Held, C. and Pinho, S.P. and Coutinho, J.A.P.
    ACS Sustainable Chemistry and Engineering 6 (2018)
    Recently, some works claim that hydrophobic deep eutectic solvents could be prepared based on menthol and monocarboxylic acids. Despite of some promising potential applications, these systems were poorly understood, and this work addresses this issue. Here, the characterization of eutectic solvents composed of the terpenes thymol or l(-)-menthol and monocarboxylic acids is studied aiming the design of these solvents. Their solid-liquid phase diagrams were measured by differential scanning calorimetry in the whole composition range, showing that a broader composition range, and not only fixed stoichiometric proportions, can be used as solvents at low temperatures. Additionally, solvent densities and viscosities close to the eutectic compositions were measured, showing low viscosity and lower density than water. The solvatochromic parameters at the eutectic composition were also investigated aiming at better understanding their polarity. The high acidity is mainly provided by the presence of thymol in the mixture, while l(-)-menthol plays the major role on the hydrogen-bond basicity. The measured mutual solubilities with water attest to the hydrophobic character of the mixtures investigated. The experimental solid-liquid phase diagrams were described using the PC-SAFT equation of state that is shown to accurately describe the experimental data and quantify the small deviations from ideality. © 2018 American Chemical Society.
    view abstract10.1021/acssuschemeng.8b01203
  • Characterization and Modeling of the Liquid Phase of Deep Eutectic Solvents Based on Fatty Acids/Alcohols and Choline Chloride
    Crespo, E.A. and Silva, L.P. and Martins, M.A.R. and Fernandez, L. and Ortega, J. and Ferreira, O. and Sadowski, G. and Held, C. and Pinho, S.P. and Coutinho, J.A.P.
    Industrial and Engineering Chemistry Research 56 (2017)
    The solid-liquid equilibria phase diagrams of eight eutectic systems formed by choline chloride and fatty acids, or fatty alcohols, were measured to characterize the nonideality of the liquid phase of these systems, commonly reported in the literature as examples of type III deep eutectic solvents (DESs), and to evaluate the best modeling approaches to their description. Most of these systems are shown to present only slight deviations from ideal behavior, resulting from a fine balance of the hydrogen bonding between the hydroxyl/carboxylic groups with the chloride anion and the interactions present in the pure compounds. The phase diagrams measured were modeled with an associative equation of state (EoS) and a gE model. As an EoS, the perturbed-chain statistical associating fluid theory (PC-SAFT) was used, and this model was able to accurately describe the experimental data and to provide reliable estimates of the eutectic points using just a single binary temperature-dependent interaction parameter that often correlates with the acid/alcohol chain length. The performance of PC-SAFT was further compared with the gE model, a non-random two-liquid model (NRTL), and was found to provide a better description of the experimental data, especially for the more nonideal systems. Ultimately, the data gathered, and the molecular modeling, allowed the discussion of the behavior of fatty acids or fatty alcohols as hydrogen bond donors in choline chloride-based DESs. © 2017 American Chemical Society.
    view abstract10.1021/acs.iecr.7b02382
  • Crowders and Cosolvents—Major Contributors to the Cellular Milieu and Efficient Means to Counteract Environmental Stresses
    Gao, M. and Held, C. and Patra, S. and Arns, L. and Sadowski, G. and Winter, R.
    ChemPhysChem 18 (2017)
    The free energy and conformational landscape of biomolecular systems as well as biochemical reactions depend not only on temperature and pressure, but also on the particular solution conditions. Such conditions include the effects of cosolvents (for example osmolytes) and macromolecular crowding, which are crucial components to understand the energetics and kinetics of biological processes in living system. Such conditions are also important for the understanding of many debilitating diseases, such as those where misfolding and amyloid formation of proteins are involved. Moreover, understanding their effects on biomolecular processes is prerequisite for designing industrially relevant enzymatic reactions, which seldom take place under neat conditions. Here, we review and discuss experimental and theoretical studies on the characterization of cosolvent and crowding induced effects in biologically relevant systems, approaching even the complexity of living organisms. In particular, we focus on cosolvent and crowding effects on the conformational equilibrium and folding kinetics of proteins and nucleic acids as well as on enzymatic reactions, including their effects on the temperature and pressure dependence of these processes. By presenting a few representative examples, we show how such effects are unveiled and described in thermodynamic and kinetic terms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/cphc.201700762
  • Influence of Natural Solutes and Ionic Liquids on the Yield of Enzyme-Catalyzed Reactions: Measurements and Predictions
    Voges, M. and Fischer, C. and Wolff, D. and Held, C.
    Organic Process Research and Development 21 (2017)
    The maximum yield of enzyme-catalyzed reactions is often limited by thermodynamic equilibrium. The knowledge of influencing factors on limitations of reactions is essential for process optimization to increase yields and to reduce solvent and energy consumption. In this work the effect of solvents/cosolvents [e.g., ionic liquid (IL)] and natural solutes on thermodynamic yield limitations of two enzyme-catalyzed model reactions were investigated, namely, an alcohol dehydrogenase (ADH) reaction (acetophenone + 2-propanol ⇌ 1-phenylethanol + acetone) and an alanine aminotransferase reaction (l-alanine + 2-oxoglutarate ⇌ pyruvate + l-glutamate). Experimental results showed that the equilibrium position and the equilibrium product yield of both reactions in aqueous single-phase systems strongly depend on the type and molality of the present natural solute/IL that were present as additives in the reaction mixture. In addition, the ADH reaction was investigated in pure IL and in an IL/buffer two-phase system. Compared to the aqueous reaction mixtures, the reactant solubility could be increased significantly, but at the cost of a lower product yield. Finally, thermodynamic modeling by means of ePC-SAFT was used to predict the equilibrium product yield of both reactions at different reaction conditions (natural solute/IL type and molality) in the aqueous mixtures as well as in the IL. Experimental and predicted results were in good agreement, showing that ePC-SAFT is a promising tool for predicting yield limitations in different reaction media. © 2017 American Chemical Society.
    view abstract10.1021/acs.oprd.7b00178
  • Influence of pH Value and Ionic Liquids on the Solubility of L-Alanine and L-Glutamic Acid in Aqueous Solutions at 30 °C
    Voges, M. and Prikhodko, I. V. and Prill, S. and Hubner, M. and Sadowski, G. and Held, C.
    Journal of Chemical and Engineering Data 62 (2017)
    The solubility of the amino acids L-alanine and L-glutamic acid and its sodium salt (sodium L-glutamate monohydrate) in aqueous solutions at 30 degrees C and atmospheric pressure was investigated in the pH range between 3 and 9 and in the presence of the ionic liquids (ILs) 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]) and choline dihydrogencitrate ([ch] [dhcit]) at pH 7. The solubility of L-alanine and L-glutamic acid in the solutions without IL was measured by UV spectroscopy and with a gravimetrical method. In the presence of an IL HPLC-analysis was applied. The solid phases were characterized using Raman spectroscopy and powder X-ray diffraction to distinguish the amino acids from their salts. While the solubility of L-alanine did not depend on pH within the considered pH range, the solubility of L-glutamic acid strongly increased with increasing pH. Below pH 6.2 the solid phase was characterized to be L-glutamic acid, while sodium L-glutamate monohydrate was found to be the solid at pH higher than 6.2. It could be observed that the solubility of sodium L-glutamate monohydrate was comparatively high, and increased with increasing pH. Upon addition of the ILs under investigation ([bmim][OTf]) and [ch] [dhcit]) the solubility of L-alanine and L-glutamic acid was decreased. Original PC-SAFT was applied to predict the solubility of L-alanine and L-glutamic acid (and its sodium salt) in water, with and without the ILs under consideration, at the experimental conditions with quantitative agreement to the experimental data.
    view abstract10.1021/acs.jced.6b00367
  • Measurement and PC-SAFT modeling of solid-liquid equilibrium of deep eutectic solvents of quaternary ammonium chlorides and carboxylic acids
    Pontes, P.V.A. and Crespo, E.A. and Martins, M.A.R. and Silva, L.P. and Neves, C.M.S.S. and Máximo, G.J. and Hubinger, M.D. and Batista, E.A.C. and Pinho, S.P. and Coutinho, J.A.P. and Sadowski, G. and Held, C.
    Fluid Phase Equilibria (2017)
    In this study the solid-liquid equilibria (SLE) of 15 binary mixtures composed of one of three different symmetrical quaternary ammonium chlorides and one of five different fatty acids were measured. The experimental data obtained showed extreme negative deviations to ideality causing large melting-temperature depressions (up to 300 K) that are characteristic for deep eutectic systems. The experimental data revealed that cross-interactions between quaternary ammonium salt and fatty acid increase with increasing alkyl chain length of the quaternary ammonium chloride and with increasing chain length of the carboxylic acid. The pronounced decrease of melting temperatures in these deep eutectic systems is mainly caused by strong hydrogen-bonding interactions, and thermodynamic modeling required an approach that takes hydrogen bonding into account. Thus, the measured phase diagrams were modeled with perturbed-chain statistical associating fluid theory based on the classical molecular homonuclear approach. The model showed very good agreement with the experimental data using a semi-predictive modeling approach, in which binary interaction parameters between quaternary ammonium chloride and carboxylic acid correlated with chain length of the components. This supports the experimental findings on the phase behavior and interactions present in these systems and it allows estimating eutectic points of such highly non-ideal mixtures. © 2017 Elsevier B.V.
    view abstract10.1016/j.fluid.2017.04.007
  • Measuring and Predicting Thermodynamic Limitation of an Alcohol Dehydrogenase Reaction
    Voges, M. and Fischer, F. and Neuhaus, M. and Sadowski, G. and Held, C.
    Industrial and Engineering Chemistry Research 56 (2017)
    The knowledge of thermodynamic limitations on enzymatic reactions and of influencing factors thereon is essential for process optimization to increase space-time yields and to reduce the amount of solvent or energy consumption. In this work, the alcohol dehydrogenase (ADH) catalyzed reaction from acetophenone and 2-propanol to 1-phenylethanol and acetone in aqueous solution was investigated in a temperature range of 293.15-303.15 K at pH 7. It serves as a model reaction to demonstrate the use of biothermodynamics in order to investigate and predict limitations of enzymatic reactions. Experimental molalities of the reacting agents at equilibrium were measured yielding the position of reaction equilibrium (Km) at different reaction conditions (temperature, initial reactant molalities). The maximum initial acetophenone molality under investigation was 0.02 mol·kg-1 due to solubility limitations with a 1- to 50-fold excess of 2-propanol. It was shown that Km strongly depends on the initial reactant molalities as well as on reaction temperature. Experimental Km values were in the range of 0.20 to 0.49. Thermodynamic key properties (thermodynamic equilibrium constant, standard Gibbs energy and standard enthalpy of reaction) were determined by measured Km values and activity coefficients of the reacting agents predicted with the thermodynamic model ePC-SAFT. In addition, ePC-SAFT was used to predict Km at different initial molalities. Experimental and predicted results were in quantitative agreement (root-mean-square error of experimental versus predicted Km was 0.053), showing that ePC-SAFT is a promising tool to identify process conditions that might increase/decrease Km values and, thus, shift the position of reactions for industrial applications. © 2017 American Chemical Society.
    view abstract10.1021/acs.iecr.7b01228
  • PC-SAFT modeling of CO2 solubilities in hydrophobic deep eutectic solvents
    Dietz, C.H.J.T. and van Osch, D.J.G.P. and Kroon, M.C. and Sadowski, G. and van Sint Annaland, M. and Gallucci, F. and Zubeir, L.F. and Held, C.
    Fluid Phase Equilibria (2017)
    The PC-SAFT 'pseudo-pure' approach was used for the modeling of CO2 solubilities in various hydrophobic deep eutectic solvents (DESs) for the first time. Only liquid density data were used to obtain the segment number, the temperature-independent segment diameter and the dispersion-energy parameter, as water activities cannot be obtained for hydrophobic substances. VLE data were successfully predicted without the need for any adjustable binary interaction k ij. Thus, solubilities of CO2 in hydrophobic DESs could be approximated with the PC-SAFT model using parameters fitted to liquid densities only. © 2017 Elsevier B.V.
    view abstract10.1016/j.fluid.2017.03.028
  • Phase Behavior of Binary Mixtures Containing Succinic Acid or Its Esters
    Altuntepe, E. and Reinhardt, A. and Brinkmann, J. and Briesemann, T. and Sadowski, G. and Held, C.
    Journal of Chemical and Engineering Data 62 (2017)
    This work provides experimental data and thermodynamic modeling on phase equilibria of binary mixtures that are relevant for esterification reactions. The components under investigation include water, succinic acid (SA), ethanol (EtOH), 1-butanol (1-BuOH), and the diesters of SA, namely, diethyl succinate (DES) and dibutyl succinate (DBS), respectively, as well as the organic solvents acetonitrile (ACN) and tetrahydrofuran (THF). Liquid-liquid equilibria (LLE) of water/DBS were measured at ambient pressure for temperatures between 313 and 353 K. Isobaric vapor-liquid equilibria (VLE) were measured for the binary systems ACN/DES, ACN/DBS, 1-BuOH/DBS, and THF/DBS at pressures of 10 or 20 or 30 kPa. Temperature ranges for the isobaric VLE varied between 300 and 500 K. The measured data and phase equilibria reported in literature were accurately modeled using perturbed-chain statistical associating fluid theory (PC-SAFT). For this purpose, pure-component PC-SAFT parameters, which were not already reported in the literature, were adjusted to experimental literature pure-component data. Applying binary interaction parameters allowed precise phase-equilibrium modeling results of the binary systems under investigation. Two different association schemes for water were used ("2B" and "4C"). Both schemes appeared to be suitable to describe phase equilibria of aqueous mixtures; however, a binary parameter for the Wolbach-Sandler mixing rule was required for aqueous mixtures modeled with the 4C scheme. For LLE modeling the 2B scheme was found to give better modeling results. In general, the 4C association scheme for water yields better results for mixtures with two self-associating components while the 2B association scheme for water should be preferred if mixtures are considered with water and a non-self-associating component. Further, the modeling concept of "induced association" has been investigated and discussed. Especially for mixtures with esters, which are of main importance for esterification mixtures, the induced-association approach turned out to be a more accurate modeling strategy compared to the nonassociative approach. © 2017 American Chemical Society.
    view abstract10.1021/acs.jced.7b00005
  • Predicting the Solubility of CO2 in Toluene + Ionic Liquid Mixtures with PC-SAFT
    Canales, R.I. and Held, C. and Lubben, M.J. and Brennecke, J.F. and Sadowski, G.
    Industrial and Engineering Chemistry Research 56 (2017)
    Perturbed-chain statistical associating fluid theory (PC-SAFT) was applied for modeling the vapor-liquid equilibrium of CO2 + toluene + ionic liquid (IL) mixtures and the molar volume of their liquid phases at temperatures between 298.15 K and 333.15 K and at pressures up to 80 bar. ILs used for this study contain the bis(trifluoromethylsulfonylimide) anion ([Tf2N]-) and imidazolium, pyridinium, thiolanium, and phosphonium cations. The pure-IL PC-SAFT parameters were fit to pure-IL liquid density data. Temperature-dependent binary interaction parameters were fit to binary liquid-liquid equilibrium data (i.e., toluene + IL) obtained from the literature and some points measured for this work. Temperature independent binary interaction parameters were fit to vapor-liquid equilibrium data (CO2 + IL, CO2 + toluene) from the literature. The availability of the pure-IL parameters and binary interaction parameters allowed prediction of CO2 solubility in toluene + IL mixtures with an absolute average relative deviation (AARD) of 6.8%, as well as molar volumes of CO2 + toluene + IL mixtures with an AARD of 5.0%, for the four ternary systems under investigation. © 2017 American Chemical Society.
    view abstract10.1021/acs.iecr.7b01497
  • Reaction Equilibrium of the ω-Transamination of (S)-Phenylethylamine: Experiments and ePC-SAFT Modeling
    Voges, M. and Abu, R. and Gundersen, M.T. and Held, C. and Woodley, J.M. and Sadowski, G.
    Organic Process Research and Development 21 (2017)
    This work focuses on the thermodynamic equilibrium of the ω-transaminase-catalyzed reaction of (S)-phenylethylamine with cyclohexanone to acetophenone and cyclohexylamine in aqueous solution. For this purpose, the equilibrium concentrations of the reaction were experimentally investigated under varying reaction conditions. It was observed that the temperature (30 and 37 °C), the pH (between pH 7 and pH 9), as well as the initial reactant concentrations (between 5 and 50 mmol·kg-1) influenced the equilibrium position of the reaction. The position of the reaction equilibrium was moderately shifted toward the product side by either decreasing temperature or decreasing pH. In contrast, the initial ratio of the reactants showed only a marginal influence on the equilibrium position. Further experiments showed that increasing the initial reactant concentrations significantly shifted the equilibrium position to the reactant side. In order to explain these effects, the activity coefficients of the reacting agents were calculated and the activity-based thermodynamic equilibrium constant Kth of the reaction was determined. For this purpose, the activity coefficients of the reacting agents were modeled at their respective experimental equilibrium concentrations using the equation of state electrolyte PC-SAFT (ePC-SAFT). The combination of the concentrations of the reacting agents at equilibrium and their respective activity coefficients provided the thermodynamically consistent equilibrium constant Kth. Unexpectedly, the experimental Km values deviated by a factor of up to four from the thermodynamic equilibrium constant Kth. The observed concentration dependency of the experimental Km values could be explained by the influence of concentration on activity coefficients. Further, these activity coefficients were found to be strongly temperature dependent, which is important for the determination of standard enthalpy of reactions, which in this work was found to be +7.7 ± 2.8 kJ·mol-1. Using the so-determined Kth and activity coefficients of the reacting agents (ePC-SAFT), the equilibrium concentrations of the reaction were predicted for varying initial reactant concentrations, which were found to be in good agreement with the experimental behavior. These results showed a non-negligible influence of the activity coefficients of the reacting agents on the equilibrium position and, thus, on the product yield. Experiments and ePC-SAFT predictions showed that the equilibrium position can only be described accurately by taking activity coefficients into account. © 2017 American Chemical Society.
    view abstract10.1021/acs.oprd.7b00078
  • Standard Gibbs energy of metabolic reactions: II. Glucose-6-phosphatase reaction and ATP hydrolysis
    Meurer, F. and Do, H. T. and Sadowski, G. and Held, C.
    Biophysical Chemistry 223 (2017)
    ATP (adenosine triphosphate) is a key reaction for metabolism. Tools from systems biology require standard reaction data in order to predict metabolic pathways accurately. However, literature values for standard Gibbs energy of ATP hydrolysis are highly uncertain and differ strongly from each other. Further, such data usually neglect the activity coefficients of reacting agents, and published data like this is apparent (condition-dependent) data instead of activity-based standard data. In this work a consistent value for the standard Gibbs energy of ATP hydrolysis was determined. The activity coefficients of reacting agents were modeled with electrolyte Perturbed Chain Statistical Associating Fluid Theory (ePC-SAFT). The Gibbs energy of ATP hydrolysis was calculated by combining the standard Gibbs energies of hexokinase reaction and of glucose-6-phosphate hydrolysis. While the standard Gibbs energy of hexokinase reaction was taken from previous work, standard Gibbs energy of glucose-6-phosphate hydrolysis reaction was determined in this work. For this purpose, reaction equilibrium molalities of reacting agents were measured at pH 7 and pH 8 at 298.15 K at varying initial reacting agent molalities. The corresponding activity coefficients at experimental equilibrium molalities were predicted with ePC-SAFT yielding the Gibbs energy of glucose-6-phosphate hydrolysis of -13.72 +/- 0.75 kJ. mol(-1). Combined with the value for hexokinase, the standard Gibbs energy of ATP hydrolysis was finally found to be - 31.55 +/- 127 kJ. mol(-1). For both, ATP hydrolysis and glucose-6-phosphate hydrolysis, a good agreement with own and literature values were obtained when influences of pH, temperature, and activity coefficients were explicitly taken into account in order to calculate standard Gibbs energy at pH 7, 298.15 K and standard state. (C) 2017 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.bpc.2017.02.005
  • Thermodynamics of enzyme-catalyzed esterifications: I. Succinic acid esterification with ethanol
    Altuntepe, E. and Greinert, T. and Hartmann, F. and Reinhardt, A. and Sadowski, G. and Held, C.
    Applied Microbiology and Biotechnology 101 (2017)
    Succinic acid (SA) was esterified with ethanol using Candida antarctica lipase B immobilized on acrylic resin at 40 and 50 °C. Enzyme activity in the reaction medium was assured prior to reaction experiments. Reaction-equilibrium experiments were performed for varying initial molalities of SA and water in the reaction mixtures. This allowed calculating the molality-based apparent equilibrium constant Km as function of concentration and temperature. Km was shown to depend strongly on the molality of water and SA as well as on temperature. It could be concluded that increasing the molality of SA shifted the reaction equilibrium towards the products. Water had a strong effect on the activity of the enzyme and on Km. The concentration dependence of Km values was explained by the activity coefficients of the reacting agents. These were predicted with the thermodynamic models Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), NRTL, and Universal Quasichemical Functional Group Activity Coefficients (UNIFAC), yielding the ratio of activity coefficients of products and reactants Kγ. All model parameters were taken from literature. The models yielded Kγ values between 25 and 115. Thus, activity coefficients have a huge impact on the consistent determination of the thermodynamic equilibrium constants Kth. Combining Km and PC-SAFT-predicted Kγ allowed determining Kth and the standard Gibbs energy of reaction as function of temperature. This value was shown to be in very good agreement with results obtained from group contribution methods for Gibbs energy of formation. In contrast, inconsistencies were observed for Kth using Kγ values from the classical gE-models UNIFAC and NRTL. The importance of activity coefficients opens the door for an optimized reaction setup for enzymatic esterifications. © 2017, Springer-Verlag Berlin Heidelberg.
    view abstract10.1007/s00253-017-8287-4
  • Thermodynamics of enzyme-catalyzed esterifications: II. Levulinic acid esterification with short-chain alcohols
    Altuntepe, E. and Emel’yanenko, V.N. and Forster-Rotgers, M. and Sadowski, G. and Verevkin, S.P. and Held, C.
    Applied Microbiology and Biotechnology 101 (2017)
    Levulinic acid was esterified with methanol, ethanol, and 1-butanol with the final goal to predict the maximum yield of these equilibrium-limited reactions as function of medium composition. In a first step, standard reaction data (standard Gibbs energy of reaction ΔRg0) were determined from experimental formation properties. Unexpectedly, these ΔRg0 values strongly deviated from data obtained with classical group contribution methods that are typically used if experimental standard data is not available. In a second step, reaction equilibrium concentrations obtained from esterification catalyzed by Novozym 435 at 323.15 K were measured, and the corresponding activity coefficients of the reacting agents were predicted with perturbed-chain statistical associating fluid theory (PC-SAFT). The so-obtained thermodynamic activities were used to determine ΔRg0 at 323.15 K. These results could be used to cross-validate ΔRg0 from experimental formation data. In a third step, reaction-equilibrium experiments showed that equilibrium position of the reactions under consideration depends strongly on the concentration of water and on the ratio of levulinic acid: alcohol in the initial reaction mixtures. The maximum yield of the esters was calculated using ΔRg0 data from this work and activity coefficients of the reacting agents predicted with PC-SAFT for varying feed composition of the reaction mixtures. The use of the new ΔRg0 data combined with PC-SAFT allowed good agreement to the measured yields, while predictions based on ΔRg0 values obtained with group contribution methods showed high deviations to experimental yields. © 2017, Springer-Verlag GmbH Germany.
    view abstract10.1007/s00253-017-8481-4
  • Benzoic Acid and Chlorobenzoic Acids: Thermodynamic Study of the Pure Compounds and Binary Mixtures with Water
    Reschke, T. and Zherikova, K.V. and Verevkin, S.P. and Held, C.
    Journal of Pharmaceutical Sciences 105 (2016)
    Benzoic acid is a model compound for drug substances in pharmaceutical research. Process design requires information about thermodynamic phase behavior of benzoic acid and its mixtures with water and organic solvents. This work addresses phase equilibria that determine stability and solubility. In this work, Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to model the phase behavior of aqueous and organic solutions containing benzoic acid and chlorobenzoic acids. Absolute vapor pressures of benzoic acid and 2-, 3-, and 4-chlorobenzoic acid from literature and from our own measurements were used to determine pure-component PC-SAFT parameters. Two binary interaction parameters between water and/or benzoic acid were used to model vapor-liquid and liquid-liquid equilibria of water and/or benzoic acid between 280 and 413 K. The PC-SAFT parameters and 1 binary interaction parameter were used to model aqueous solubility of the chlorobenzoic acids. Additionally, solubility of benzoic acid in organic solvents was predicted without using binary parameters. All results showed that pure-component parameters for benzoic acid and for the chlorobenzoic acids allowed for satisfying modeling phase equilibria. The modeling approach established in this work is a further step to screen solubility and to predict the whole phase region of mixtures containing pharmaceuticals. © 2016 American Pharmacists Association®.
    view abstract10.1016/j.xphs.2015.12.020
  • Cation Effect on the Water Activity of Ternary (S)-Aminobutanedioic Acid Magnesium Salt Solutions at 298.15 and 310.15 K
    Held, C. and Tsurko, E.N. and Neueder, R. and Sadowski, G. and Kunz, W.
    Journal of Chemical and Engineering Data 61 (2016)
    Vapor pressure osmometry was applied to the system aminomethanamidine hydrochloride (guanidinium hydrochloride, GndmCl) + (S)-aminobutanedioic acid hemimagnesium salt (magnesium l-aspartate, Mg-(l-Asp)2) + water for varying molalities of GndmCl and Mg-(l-Asp)2 (mMg-(Asp)2 = 0.1, 0.2, and 0.3 mol/kg and mGndmCl = 0.1-1.2 mol/kg) at T = 298.15 and 310.15 K. From vapor pressure osmometry, activities of water, activity coefficients of water, and the corresponding osmotic coefficients of the mixtures Mg-(l-Asp)2 + water and Mg-(l-Asp)2 + GndmCl + water have been calculated, both being directly related to the chemical potentials of the different species and therefore to their Gibbs energy. Electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) accounting for Coulomb and short-range (hard chain, dispersion, association) interactions was used to model the own experimental data of binary Mg-(l-Asp)2 + water and ternary GndmCl + Mg-(l-Asp)2 + water solutions. ePC-SAFT was further applied to model osmotic coefficients of NaGlu + KCl + water, NaGlu + NaCl + water, NaAsp + NaCl + water, NaAsp + KCl + water, aminoethanoic acid + NaNO3 + water, and aminoethanoic acid + NaSCN + water as well as thermodynamic properties of these solutions such as fugacity coefficients and activity coefficients of the mixture components. Without fitting any parameters to data of the ternary salt + aminoethanoic acid + water system, osmotic coefficients, φ, and activity coefficients of water, γ1, and aminoethanoic acid have been predicted, and φ and γ1 were in good agreement with the experimental data. In contrast, a negative binary interaction parameter kij had to be introduced to model φ of ternary systems salt + amino acid salt + water in accurate agreement with the experimental data. © 2016 American Chemical Society.
    view abstract10.1021/acs.jced.6b00295
  • Compatible solutes: Thermodynamic properties relevant for effective protection against osmotic stress
    Held, C. and Sadowski, G.
    Fluid Phase Equilibria 407 (2016)
    Organisms developed very different strategies to protect themselves against osmotic stress. To sustain high salt concentrations of their surrounding some organisms accumulate so-called compatible solutes (CSs), which increase the internal osmotic pressure without disturbing the organism's metabolism. At constant temperature, osmotic pressure is mainly determined by the concentration of the compatible solute and the osmotic coefficient of the aqueous solution, and to a minor extent also by solution densities. Thus, osmotic coefficients and densities were measured for aqueous CS solutions in a broad range of concentration and at three temperatures (273. K, 310. K, 323. K) at atmospheric pressure. Further, the solubility of CSs in water was measured as function of temperature to determine the maximum CS concentration that can be applied in aqueous solutions. CSs under investigation were trimethylamine N-oxide (TMAO), trehalose, citrulline, N,. N-dimethylglycine, DMSO, glycerol, methylglycine, and ectoine. The data was used to calculate real osmotic pressures induced by these CSs. PC-SAFT was applied to model thermodynamic properties and phase equilibria of aqueous CS solutions in quantitative agreement to experimental data. Among the CSs investigated in this work, TMAO induced the highest osmotic pressure and thus can be considered the best protector against osmotic stress. The data was finally analyzed concerning the influence of CSs molecular size, charge, and hydrophobicity on osmotic pressure. This included also the comparison to incompatible solutes (urea, glycine). © 2015 Elsevier B.V.
    view abstract10.1016/j.fluid.2015.07.004
  • Erweiterung der Prozessfenster enzymkatalysierter Reaktionen
    Held, C.
    Chemie-Ingenieur-Technik 88 (2016)
    view abstract10.1002/cite.201650420
  • Influence of electrolytes on liquid-liquid equilibria of water/1-butanol and on the partitioning of 5-hydroxymethylfurfural in water/1-butanol
    Mohammad, S. and Grundl, G. and Müller, R. and Kunz, W. and Sadowski, G. and Held, C.
    Fluid Phase Equilibria 428 (2016)
    The influence of electrolytes on liquid-liquid equilibria (LLE) of water/1-butanol and on the partitioning of 5-hydroxymethylfurfural (HMF) between water-rich and 1-butanol-rich phases was investigated in this study. For that purpose, the LLE of the ternary systems water/1-butanol/HMF, water/1-butanol/salt, and the LLE of the quaternary system water/1-butanol/HMF/salt were measured at 298.15 K under atmospheric pressure. The investigated salts were composed of one of the anions Cl−, CH3COO−, NO3 − and SO4 2− and either Li+ or Na+. By investigating the LLE of the system water/1-butanol/salt it was found that 1-butanol was salted-out from the aqueous phase by all salts, and the strength of the salting-out increased in the following order NO3 − <  CH3COO− ≈ Cl− <  SO4 2−, independently of the cation. Based on the LLE data, the partition coefficient KHMF w of HMF between 1-butanol and aqueous phase was determined. Li2SO4 caused a pronounced salting-out of HMF from the aqueous phase, whereas only a moderate influence was observed for NaCl and CH3COONa. LiCl even caused a salting-in at LiCl molalities above 6 mol/kgH2O. electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was successfully used to model the influence of salts on the LLE water/1-butanol. Without fitting parameters to LLE data of the quaternary system water/1-butanol/HMF/salt, ePC-SAFT allowed predicting the salt influence on the partitioning of HMF in these systems in good agreement with the experimental data. © 2016 Elsevier B.V.
    view abstract10.1016/j.fluid.2016.05.001
  • Influence of Salts on the Partitioning of 5-Hydroxymethylfurfural in Water/MIBK
    Mohammad, S. and Held, C. and Altuntepe, E. and Köse, T. and Sadowski, G.
    Journal of Physical Chemistry B 120 (2016)
    This study investigates the influence of electrolytes on the performance of extracting 5-hydroxymethylfurfural (HMF) from aqueous media using methyl isobutyl ketone (MIBK). For that purpose, liquid-liquid phase equilibria (LLE) of quaternary systems containing HMF, water, MIBK and salts were measured at atmospheric pressure and 298.15 K. The salts under investigation were composed of one of the anions NO3-, SO4 2-, Cl-, or CH3COO- and of one of the alkali cations Li+, Na+, or K+. On the basis of these LLE data, the partition coefficient of HMF between the aqueous and the MIBK phase KHMF was determined. It could be shown that KHMF significantly depends on the kind and concentration of the added salt. Weak electrolytes (e.g., sulfates, acetates) caused salting-out, whereas nitrates caused salting-in of HMF to the aqueous phase. Unexpectedly, LiCl caused salting-out at low LiCl concentrations and salting-in at LiCl concentrations higher than 3 mol/kg H2O. The model electrolyte perturbed-chain SAFT (ePC-SAFT) was used to predict the salt influence on the LLE in the quaternary systems water/MIBK/HMF/salt in good agreement with the experimental data. On the basis of ePC-SAFT, it could be concluded that the different salting-out/salting-in behavior of the various salts is mainly caused by their different tendency to form ion pairs in aqueous solutions. © 2016 American Chemical Society.
    view abstract10.1021/acs.jpcb.5b11588
  • Modeling the density of ionic liquids with ePC-SAFT
    Ji, X. and Held, C.
    Fluid Phase Equilibria 410 (2016)
    ePC-SAFT was used to model the densities of ionic liquids (ILs) up to high pressures and temperatures. The ILs under consideration contained one of the IL-cations [Cnmim]+, [Cnpy]+, [Cnmpy]+, [Cnmpyr]+ or [THTDP]+, and one of the IL-anions [Tf2N]-, [PF6]-, [BF4]-, [tfo]-, [DCA]-, [SCN]-, [C1SO4]-, [C2SO4]-, [eFAP]-, Cl-, [Ac]- or Br-, respectively. Within the ePC-SAFT framework, IL-ion specific parameters were applied that are valid independent of the IL they are part of. Each IL-ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. The ePC-SAFT parameters for [Cnmim]+ (n = 2, 4, 6 and 8), [Tf2N]-, [PF6]-, and [BF4]- were taken from our previous work (Fluid Phase Equilibria 2012 (335) 64-73). Based on these parameters, all parameters of the other IL-ions were fitted to experimental density of pure ILs up to high pressures in a broad temperature range. Being provided with ion-specific and linearly molecular-weight-dependent parameters, ePC-SAFT allows reliably representing/predicting pure-IL and mixed-IL density up to high pressures. © 2015 Elsevier B.V.
    view abstract10.1016/j.fluid.2015.11.014
  • Modelling interfacial properties of ionic liquids with ePC-SAFT combined with density gradient theory
    Shen, G. and Held, C. and Lu, X. and Ji, X.
    Molecular Physics 114 (2016)
    Highlights: Combination of ePC-SAFT with density gradient theory Calculation of interfacial properties of pure ILs in broad temperature range Quantitative predictions of surface tensions for ILs not used in κ parameter fitting © 2016 Informa UK Limited, trading as Taylor & Francis Group.
    view abstract10.1080/00268976.2016.1171408
  • PC-SAFT Modeling of CO2 Solubilities in Deep Eutectic Solvents
    Zubeir, L.F. and Held, C. and Sadowski, G. and Kroon, M.C.
    Journal of Physical Chemistry B 120 (2016)
    Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), a physically based model that accounts for different molecular interactions explicitly, was applied to describe for the first time the phase behavior of deep eutectic solvents (DESs) with CO2 at temperatures from 298.15 to 318.15 K and pressures up to 2 MPa. DESs are mixtures of two solid compounds, a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA), which form liquids upon mixing with melting points far below that of the individual compounds. In this work, the HBD is lactic acid and the HBAs are tetramethylammonium chloride, tetraethylammonium chloride, and tetrabutylammonium chloride. Two different modeling strategies were considered for the PC-SAFT modeling. In the first strategy, the so-called pseudo-pure component approach, a DES was considered as a pseudo-pure compound, and its pure-component parameters were obtained by fitting to pure DES density data. In the second strategy, the so-called individual-component approach, a DES was considered to consist of two individual components (HBA and HBD), and the pure-component parameters of the HBA and HBD were obtained by fitting to the density of aqueous solutions containing only the individual compounds of the DES. In order to model vapor-liquid equilibria (VLE) of DES + CO2 systems, binary interaction parameters were adjusted to experimental data from the literature and to new data measured in this work. It was concluded that the individual-component strategy allows quantitative prediction of the phase behavior of DES + CO2 systems containing those HBD:HBA molar ratios that were not used for kij fitting. In contrast, applying the pseudo-pure component strategy required DES-composition specific kij parameters. © 2016 American Chemical Society.
    view abstract10.1021/acs.jpcb.5b07888
  • Salt influence on MIBK/water liquid-liquid equilibrium: Measuring and modeling with ePC-SAFT and COSMO-RS
    Mohammad, S. and Held, C. and Altuntepe, E. and Köse, T. and Gerlach, T. and Smirnova, I. and Sadowski, G.
    Fluid Phase Equilibria 416 (2016)
    In biotechnological processes, salts might be present during reaction steps and in downstream processes. Salts are known to have a strong impact on phase equilibria of aqueous systems.In this work, the liquid-liquid equilibria (LLE) of ternary salt/MIBK/water mixtures were measured at 298.15 K and 1 bar up to the salt solubility limit. The salts studied in this work were NaCl, LiCl, KCl, NaNO3, LiNO3, Na2SO4, CH3COONa, and CH3COOLi. From these LLE measurements it was found that a high amount of salt is dissolved in the aqueous phase whereas only a very small amount of salt was detected in the MIBK phase. Further, the salting-out behavior of MIBK from the aqueous phase upon addition of different salts was investigated to study ion-specific effects.Two ion-specific models, ePC-SAFT and an extended version of COSMO-RS for electrolytes were used for modeling the binary system MIBK/water and ternary salt/MIBK/water systems. In case of the COSMO-RS based approach, the modeling results were fully predictive. In contrast, ion-specific binary interaction parameters between MIBK and ions were fitted to experimental LLE data of the ternary systems salt/MIBK/water when using ePC-SAFT. The results show that the COSMO-RS based approach allows for predicting the salt influence on LLE with acceptable accuracy, whereas ePC-SAFT allows for almost quantitative correlations of experimental data. © 2015 Elsevier B.V.
    view abstract10.1016/j.fluid.2015.11.018
  • Standard Gibbs Energy of Metabolic Reactions: I. Hexokinase Reaction
    Meurer, F. and Bobrownik, M. and Sadowski, G. and Held, C.
    Biochemistry 55 (2016)
    The standard Gibbs energy of reaction enables calculation of the driving force of a (bio)chemical reaction. Gibbs energies of reaction are required in thermodynamic approaches to determine fluxes as well as single reaction conversions of metabolic bioreactions. The hexokinase reaction (phosphorylation of glucose) is the entrance step of glycolysis, and thus its standard Gibbs energy of reaction (ΔRg°) is of great impact. ΔRg° is accessible from equilibrium measurements, and the very small concentrations of the reacting agents cause usually high error bars in data reduction steps. Even worse, works from literature do not account for the nonideal behavior of the reacting agents (activity coefficients were assumed to be unity); thus published ΔRg° values are not standard data. Consistent treatment of activity coefficients of reacting agents is crucial for the accurate determination of standard Gibbs energy from equilibrium measurements. In this work, equilibrium molalities of hexokinase reaction were measured with an enzyme kit. These results were combined with reacting agents' activity coefficients obtained with the thermodynamic model ePC-SAFT. Pure-component parameters for adenosine triphosphate (ATP) and adenosine diphosphate (ADP) were fitted to experimental osmotic coefficients (water + Na2ATP, water + NaADP). ΔRg° of the hexokinase reaction at 298.15 K and pH 7 was found to be -17.83 ± 0.52 kJ·mol-1. This value was compared with experimental literature data; very good agreement between the different ΔRg° values was obtained by accounting for pH, pMg, and the activity coefficients of the reacting agents. © 2016 American Chemical Society.
    view abstract10.1021/acs.biochem.6b00471
  • Thermochemistry of halogenobenzoic acids as an access to PC-SAFT solubility modeling
    Zherikova, K.V. and Svetlov, A.A. and Varfolomeev, M.A. and Verevkin, S.P. and Held, C.
    Fluid Phase Equilibria 409 (2016)
    Absolute vapor pressures and molar sublimation enthalpies of 2-, 3-, and 4-monohalogenobenzoic acids (halogen = fluorine and iodine) were derived from transpiration measurements. Molar enthalpies of fusion were measured by DSC. Thermochemical data available in the literature were collected, evaluated, and combined with own experimental results in order to recommend sets of sublimation and fusion enthalpies. Further, the recommended data were used to estimate PC-SAFT pure-component parameters. These parameters were applied to predict the solubility of the monohalogenobenzoic acids in water at 298.15 K, yielding satisfying prediction results. This approach proved the capability of PC-SAFT to predict solid-liquid phase equilibria if precise data on sublimation pressures and fusion properties is available. © 2015 Elsevier B.V.
    view abstract10.1016/j.fluid.2015.10.001
  • Thermodynamics of a model biological reaction: A comprehensive combined experimental and theoretical study
    Emel'yanenko, V.N. and Yermalayeu, A.V. and Voges, M. and Held, C. and Sadowski, G. and Verevkin, S.P.
    Fluid Phase Equilibria 422 (2016)
    In this work we applied experimental and theoretical thermodynamics to methyl ferulate hydrolysis, a model biological reaction, in order to calculate the equilibrium constant and reaction enthalpy. In the first step, reaction data was collected. Temperature-dependent equilibrium concentrations of methyl ferulate hydrolysis have been measured. These were combined with activity coefficients predicted with electrolyte PC-SAFT in order to derive thermodynamic equilibriums constants K a as a function of temperature.In a second step, thermochemical properties of the highly pure reaction participants methyl ferulate and ferulic acid were measured by complementary thermochemical methods including combustion and differential scanning calorimetry. Vapor pressures and sublimation enthalpies of these compounds were measured by transpiration and TGA methods over a broad temperature range. Thermodynamic data on methyl ferulate and ferulic acid available in the literature were evaluated and combined with our own experimental results. Further, the standard molar enthalpy of methyl ferulate hydrolysis reaction calculated according to the Hess's Law applied to the reaction participants was found to be in agreement with the experimental reaction enthalpy from the equilibrium study.In a final step, the gas-phase equilibrium constant of methyl ferulate hydrolysis at 298.15 K was calculated with the G3MP2 method. This value was adjusted to the liquid phase using the experimental vapor pressures of the reaction participants. As a result, the liquid phase K a value calculated by quantum chemistry with additional data on the pure reaction participants was in good agreement with the experimental K a reported in the literature for the aqueous phase. The thermodynamic procedure based on the quantum-chemical calculations is found to be a valuable option for assessment of thermodynamic properties of biologically relevant chemical reactions. © 2016 Elsevier B.V.
    view abstract10.1016/j.fluid.2016.01.035
  • Thermodynamics of Bioreactions
    Held, C. and Sadowski, G.
    Annual Review of Chemical and Biomolecular Engineering 7 (2016)
    Thermodynamic principles have been applied to enzyme-catalyzed reactions since the beginning of the 1930s in an attempt to understand metabolic pathways. Currently, thermodynamics is also applied to the design and analysis of biotechnological processes. The key thermodynamic quantity is the Gibbs energy of reaction, which must be negative for a reaction to occur spontaneously. However, the application of thermodynamic feasibility studies sometimes yields positive Gibbs energies of reaction even for reactions that are known to occur spontaneously, such as glycolysis. This article reviews the application of thermodynamics in enzyme-catalyzed reactions. It summarizes the basic thermodynamic relationships used for describing the Gibbs energy of reaction and also refers to the nonuniform application of these relationships in the literature. The review summarizes state-of-the-art approaches that describe the influence of temperature, pH, electrolytes, solvents, and concentrations of reacting agents on the Gibbs energy of reaction and, therefore, on the feasibility and yield of biological reactions. Copyright © 2016 by Annual Reviews. All rights reserved.
    view abstract10.1146/annurev-chembioeng-080615-034704
  • Thermodynamics of the alanine aminotransferase reaction
    Voges, M. and Schmidt, F. and Wolff, D. and Sadowski, G. and Held, C.
    Fluid Phase Equilibria 422 (2016)
    The thermodynamic equilibrium of the aminotransferase reaction from l-alanine and 2-oxoglutarate to l-glutamate and pyruvate in aqueous solution was investigated in a temperature range between 25 and 37 °C and pH between at 5 and 9.Prior to considering the reaction equilibria, measurements were carried out to ensure the enzyme activity in the aqueous reaction media. After that, equilibrium concentrations of reacting agents were measured by HPLC-analysis. At constant temperature and pH, reaction equilibrium was shown to depend on the absolute molalities (0.005-0.130 mol kg-1) as well as on the ratio of initial molalities of the reactants. It could be concluded that reaction equilibrium was shifted towards the product site upon increasing reactant molalities, increasing temperature, and increasing pH. Further, yields of pyruvate were increased upon excess initial molality of l-alanine compared to 2-oxoglutarate.The thermodynamic equilibrium constant Ka* was determined by extrapolating the ratio of product equilibrium molalites and reactant equilibrium molalites to infinite dilution of all reacting agents. The activity-coefficient ratio of products and reactants in the reaction media was predicted with ePC-SAFT. Combining Ka* and the activity-coefficient ratio allowed quantitatively predicting the influence of temperature, pH, and reacting-agent molalities on the reaction equilibrium. © 2016 Elsevier B.V.
    view abstract10.1016/j.fluid.2016.01.023
  • Activity coefficients at infinite dilution for different alcohols and ketones in [EMpy][ESO4]: Experimental data and modeling with PC-SAFT
    Domínguez, I. and Gonzalez, B. and Orge, B. and Held, C. and Voges, M. and Macedo, E.A.
    Fluid Phase Equilibria 424 (2015)
    Experimental activity coefficients of different alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol) and ketones (acetone, 2-butanone, 2-pentanone, 3-methyl-2-butanone and 4-methyl-2-pentanone) at infinite dilution in 1-Ethyl 3-Methylpyridinium Ethyl Sulfate ionic liquid ([EMpy][ESO4]) were measured at temperatures from 323 to 373 K, using the inverse gas chromatography technique. The experimental results show that infinite dilution activity coefficients of both alcohols and ketones only marginally depend on temperature between 323 and 373 K. Further, it could be observed that infinite dilution activity coefficients of methanol, ethanol, and 1-propanol are lower than unity, whereas 1-butanol and 1-pentanol activity coefficients at infinite dilution were higher than unity. In contrast, the activity coefficients at infinite dilution of all ketones were found to be greater than unity. Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to model the obtained experimental data. Firstly, the pure-component parameters for [EMpy][ESO4] were determined by fitting experimental pure-IL densities and activity coefficients of 1-propanol. Based on this, activity coefficients in binary [EMpy][ESO4]/alcohol and [EMpy][ESO4]/ketone mixtures were modeled with good agreement to experimental data. Binary interaction parameters between [EMpy][ESO4]/alcohol and [EMpy][ESO4]/ketone were used. They were found to depend logarithmically on the chain length of any alcohol or ketone, respectively. © 2015 Elsevier B.V.
    view abstract10.1016/j.fluid.2015.09.003
  • Benchmark Thermochemistry for Biologically Relevant Adenine and Cytosine. A Combined Experimental and Theoretical Study
    Emel'yanenko, V.N. and Zaitsau, D.H. and Shoifet, E. and Meurer, F. and Verevkin, S.P. and Schick, C. and Held, C.
    Journal of Physical Chemistry A 119 (2015)
    The thermochemical properties available in the literature for adenine and cytosine are in disarray. A new condensed phase standard (p° = 0.1 MPa) molar enthalpy of formation at T = 298.15 K was measured by using combustion calorimetry. New molar enthalpies of sublimation were derived from the temperature dependence of vapor pressure measured by transpiration and by the quarz-crystal microbalance technique. The heat capacities of crystalline adenine and cytosine were measured by temperature-modulated DSC. Thermodynamic data on adenine and cytosine available in the literature were collected, evaluated, and combined with our experimental results. Thus, the evaluated collection of data together with the new experimental results reported here has helped to resolve contradictions in the available enthalpies of formation. A set of reliable thermochemical data is recommended for adenine and cytosine for further thermochemical calculations. Quantum-chemical calculations of the gas phase molar enthalpies of formation of adenine and cytosine have been performed by using the G4 method and results were in excellent agreement with the recommended experimental data. The standard molar entropies of formation and the standard molar Gibbs functions of formation in crystal and gas state have been calculated. Experimental vapor-pressure data measured in this work were used to estimate pure-component PC-SAFT parameters. This allowed modeling solubility of adenine and cytosine in water over the temperature interval 278-310 K. © 2015 American Chemical Society.
    view abstract10.1021/acs.jpca.5b04753
  • Effect of salts on the solubility of ionic liquids in water: Experimental and electrolyte Perturbed-Chain Statistical Associating Fluid Theory
    Neves, C.M.S.S. and Held, C. and Mohammad, S. and Schleinitz, M. and Coutinho, J.A.P. and Freire, M.G.
    Physical Chemistry Chemical Physics 17 (2015)
    Due to scarce available experimental data, as well as due to the absence of predictive models, the influence of salts on the solubility of ionic liquids (ILs) in water is still poorly understood. To this end, this work addresses the solubility of the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4C1im][NTf2]), at 298.15 K and 0.1 MPa, in aqueous salt solutions (from 0.1 to 1.5 mol kg-1). At salt molalities higher than 0.2 mol kg-1, all salts caused salting-out of [C4C1im][NTf2] from aqueous solution with their strength decreasing in the following order: Al2(SO4)3 &gt; ZnSO4 &gt; K3C6H5O7 &gt; KNaC4H4O6 &gt; K3PO4 &gt; Mg(CH3CO2)2 &gt; K2HPO4 &gt; MgSO4 &gt; KH2PO4 &gt; KCH3CO2. Some of these salts lead however to the salting-in of [C4C1im][NTf2] in aqueous medium at salt molalities lower than 0.2 mol kg-1. To attempt the development of a model able to describe the salt effects, comprising both the salting-in and salting-out phenomena observed, the electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was applied using ion-specific parameters. The gathered experimental data was modelled using ePC-SAFT parameters complemented by fitting a single binary parameter between K+ and the IL-ions to the IL solubility in K3PO4 aqueous solutions. Based on this approach, the description of anion-specific salting-out effects of the remaining potassium salts was found to be in good agreement with experimental data. Remarkably, ePC-SAFT is even able to predict the salting-in effect induced by K2HPO4, based on the single K+/IL-ions binary parameter which was fitted to an exclusively salting-out effect promoted by K3PO4. Finally, ePC-SAFT was applied to predict the influence of other sodium salts on the [C4C1im][NTf2] solubility in water, with experimental data taken from literature, leading to an excellent description of the liquid-liquid phase behaviour. © the Owner Societies 2015.
    view abstract10.1039/c5cp06166k
  • Measurement and PC-SAFT modelling of three-phase behaviour
    Rodríguez-Palmeiro, I. and Rodríguez, O. and Soto, A. and Held, C.
    Physical Chemistry Chemical Physics 17 (2015)
    Modelling of multi-component systems with complex interactions is an ongoing challenge in thermodynamics due to their great relevance in industry and academia. Systems that build three liquid phases are found in many interesting applications (separation processes, triphasic catalysis. . .). Among them, the surfactant flooding method for enhanced oil recovery is noticeable. In this method, a stable solution of water, surfactants, co-surfactants, salts and other components is injected into the reservoir. The optimal formulation of this surfactant system is associated with a three-phase behaviour in which the interfacial tension becomes significantly low. In this work, the PC-SAFT equation of state was used for the first time to predict the equilibrium involved in triphasic systems using solely pure-component parameters. The model without any fitting parameter was able to predict the three-phase behaviour. A great agreement between experimental and predicted compositions for (water + [C10mim][NTf2] + n-dodecane) and (water + [C12mim][NTf2] + n-dodecane) ternary systems at 298.15 K and atmospheric pressure was found. At 348.15 K slightly higher deviations were found, which can be compensated by the introduction of just one binary interaction parameter. The success of this achievement could mean an important advancement in upstream oil operations, enabling a faster and cheaper method to carry out an initial screening of potential surfactants. © the Owner Societies 2015.
    view abstract10.1039/c4cp04336g
  • Modeling thermodynamic derivative properties of ionic liquids with ePC-SAFT
    Shen, G. and Held, C. and Lu, X. and Ji, X.
    Fluid Phase Equilibria 405 (2015)
    In this work, ePC-SAFT was extended to predict the second order thermodynamic derivative properties of pure ionic liquids (ILs), such as isothermal and isentropic compressibility coefficients, thermal pressure coefficient, heat capacities, speed of sound, thermal expansion coefficient and internal pressure. ePC-SAFT predictions were compared with available experimental data of imidazolium-based ILs. The pure-component ePC-SAFT parameters for the IL-cations [C<inf>2</inf>mim]+, [C<inf>4</inf>mim]+, [C<inf>6</inf>mim]+ and [C<inf>8</inf>mim]+, and IL-anions [BF<inf>4</inf>]-, [PF<inf>6</inf>]- and [Tf<inf>2</inf>N]- were taken from literature in order to predict the thermodynamic derivative properties. The pure-component ePC-SAFT parameters for the IL-cations [C<inf>3</inf>mim]+, [C<inf>5</inf>mim]+, [C<inf>7</inf>mim]+ and [C<inf>10</inf>mim]+ were predicted based on linear molecular-weight-dependent relations. These estimated ePC-SAFT parameters were verified by comparing so-predicted pure-IL density as well as predicted CO<inf>2</inf> solubility in ILs with respective experimental data. Further, these parameters were used to predict the second order thermodynamic derivative properties. The comparison of model prediction with experimental data showed that ePC-SAFT predictions were reliable in a wide temperature and pressure range. © 2015 Elsevier B.V..
    view abstract10.1016/j.fluid.2015.07.018
  • Predicting CO2 solubility in aqueous N-methyldiethanolamine solutions with ePC-SAFT
    Uyan, M. and Sieder, G. and Ingram, T. and Held, C.
    Fluid Phase Equilibria 393 (2015)
    In this work, electrolyte PC-SAFT equation of state developed in 2005 with the parameters from Held et al. [Chem. Eng. Res. Des. 92 (2014) 2884-2897] has been applied to predict the solubility of CO2 in aqueous N-methyldiethanolamine (MDEA) solutions. The considered temperature range was 313-413K, MDEA weight fractions up to 0.32 (related to the binary water/MDEA system) and loadings of up to 1.32 (mole CO2/mole MDEA).In order to predict CO2 solubilities, the reaction equilibria and phase equilibria were solved simultaneously by explicitly accounting for the electrolyte species being present in the system: H+, OH-, HCO3-, CO32- and MDEAH+. The pure-component parameters for the molecular components (H2O, CO2, MDEA) and for all ions except MDEAH+ were already available in the literature. MDEAH+ pure-component parameters were inherited from MDEA, and the charge was explicitly accounted for in ePC-SAFT. Binary parameters were applied only for the pairs H2O/CO2, H2O/ions, and H2O/MDEA. The deviations between experimental and ePC-SAFT modeled CO2 solubility in aqueous MDEA solutions was 19.82% for a temperature range of 313-413K, a MDEA weight fractions of 0.19, and CO2 loadings of up to 1.3 (mole CO2/mole MDEA). As binary parameters have not been adjusted to experimental CO2 solubility data in aqueous MDEA solutions, these results can be considered as predictive. © 2015.
    view abstract10.1016/j.fluid.2015.02.026
  • Separation performance of BioRenewable deep eutectic solvents
    Verevkin, S.P. and Sazonova, A.Y. and Frolkova, A.K. and Zaitsau, D.H. and Prikhodko, I.V. and Held, C.
    Industrial and Engineering Chemistry Research 54 (2015)
    Deep eutectic solvents (DESs) have been regarded as promising cost-effective and environmentally benign alternatives to conventional volatile organic solvents. The screening and selection of the suitable solvent for separation is an important part of the process design. Limiting activity coefficients provide a useful tool for the optimal choice of the selective solvent. For the first time, activity coefficients at infinite dilution have been measured in DESs as a solvent for 23 solutes (aliphatic and aromatic hydrocarbons, alcohols, ketones, ethers, and esters). The DESs were constituted from choline chloride and glycerol in molar ratios of 1:1 and 1:2. The measurements were carried out with the help of gas-liquid chromatography in the temperature range 298-358 K. Using experimental results, selectivity of different separation cases was assessed. To verify the separation performance of DESs the perturbed-chain statistical associating fluid theory (PC-SAFT) was employed for the first time. This method appears to be powerful tool for screening of suitable precursors and evaluation of separation performance at temperatures relevant for practical applications. It has turned out that the separation performances of DESs are comparable to those of ionic liquids, but DESs are cheaper, because they are constituted from natural and renewable nontoxic bioresources. © 2015 American Chemical Society.
    view abstract10.1021/acs.iecr.5b00357
  • A thermodynamic investigation of the glucose-6-phosphate isomerization
    Hoffmann, P. and Held, C. and Maskow, T. and Sadowski, G.
    Biophysical Chemistry 195 (2014)
    In this work, ΔRg+ values for the enzymatic G6P isomerization were determined as a function of the G6P equilibrium molality between 25 °C and 37 °C. The reaction mixtures were buffered at pH = 8.5. In contrast to standard literature work, ΔRg+ values were determined from activity-based equilibrium constants instead of molality-based apparent values. This yielded a ΔRg+ value of 2.55 ± 0.05 kJ mol- 1 at 37 °C, independent of the solution pH between 7.5 and 8.5. Furthermore, ΔRh + was measured at pH = 8.5 and 25 °C yielding 12.05 ± 0.2 kJ mol- 1. Accounting for activity coefficients turned out to influence ΔRg+ up to 30% upon increasing the G6P molality. This result was confirmed by predictions using the thermodynamic model ePC-SAFT. Finally, the influence of the buffer and of potassium glutamate as an additive on the reaction equilibrium was measured and predicted with ePC-SAFT in good agreement. © 2014 Elsevier B.V.
    view abstract10.1016/j.bpc.2014.08.002
  • Density of Mixtures Containing Sugars and Ionic Liquids: Experimental Data and PC-SAFT Modeling
    Carneiro, A.P. and Rodríguez, O. and Held, C. and Sadowski, G. and A. Macedo, E.
    Journal of Chemical and Engineering Data 59 (2014)
    The potential use of ionic liquids (ILs) for biomass and carbohydrate processing has been discovered in the past decade. Many advantages have been pointed out in their application for biorefining purposes. The phase equilibria and volumetric properties of mixtures containing ILs and biomass-derived compounds such as sugars or sugar alcohols are relevant for process design. In this work, the density, at atmospheric pressure, of binary mixtures containing sugars (glucose and fructose) or sugar alcohols (xylitol and sorbitol) and ionic liquids (1-ethyl-3-methylimidazolium ethylsulfate and Aliquat336) is presented within large temperature (278 K to 343 K) and composition ranges (up to sugar or sugar alcohol mass fraction of 0.30). The density data followed a bilinear trend with respect to temperature and composition. The data were therefore represented using planar regression with a very good accuracy, average relative deviation (ARD) < 0.1 % in most of the cases. The perturbed-chain statistical association fluid theory (PC-SAFT) equation of state was applied to model solutions containing ILs. The pure-component parameters for Aliquat336 were fitted to pure-IL density data. Applying temperature-dependent kij parameters, PC-SAFT allowed satisfactory modeling of the measured density data and literature solubility data of sugars and sugar alcohols in Aliquat336. © 2014 American Chemical Society.
    view abstract10.1021/je500079y
  • EPC-SAFT revised
    Held, C. and Reschke, T. and Mohammad, S. and Luza, A. and Sadowski, G.
    Chemical Engineering Research and Design 92 (2014)
    So far, the electrolyte PC-SAFT equation of state developed in Cameretti et al. (2005) has been applied to model solution densities, vapor-liquid equilibria (VLE), liquid-liquid equilibria (LLE), and solid-liquid equilibria (SLE) of solutions containing electrolytes. For that purpose, two ion-specific parameters were used to characterize any ion: the diameter of the solvated ion and the dispersion-energy parameter between ion and solvent. Dispersion was only considered between ions and solvents. Considering the small number of adjustable parameters, this approach yielded acceptable results especially for low and moderate electrolyte concentrations. However, for high salt concentrations, a distinct deviation between modeled and experimental data was observed. In this work a new modeling approach is suggested that accounts explicitly also for dispersion interactions between anions and cations. This yields a much more precise description of electrolyte solutions at higher concentrations compared to original ePC-SAFT. With this new approach it is also possible to directly model weak electrolyte solutions without using an additional approach that accounts for ion-pair formation. The new approach for applying ePC-SAFT is now able to model phase equilibria (VLE, LLE, SLE) of ternary electrolyte solutions containing water, organic solvents, salts, and amino acids even at high salt concentrations in good agreement with experimental data. © 2014 The Institution of Chemical Engineers.
    view abstract10.1016/j.cherd.2014.05.017
  • Measuring and modeling aqueous electrolyte/amino-acid solutions with ePC-SAFT
    Held, C. and Reschke, T. and Müller, R. and Kunz, W. and Sadowski, G.
    Journal of Chemical Thermodynamics 68 (2014)
    In this work thermodynamic properties of electrolyte/amino acid/water solutions were measured and modeled. Osmotic coefficients at 298.15 K were measured by means of vapor-pressure osmometry. Amino-acid solubility at 298.15 K was determined gravimetrically. Considered aqueous systems contained one of the four amino acids: glycine, L-/DL-alanine, L-/DL-valine, and L-proline up to the respective amino-acid solubility limit and one of 13 salts composed of the ions Li+, Na+, K+, NH4 +, Cl-, Br-, I-, NO3 -, and SO4 2- at salt molalities of 0.5, 1.0, and 3.0 mol · kg-1, respectively. The data show that the salt influence is more pronounced on osmotic coefficients than on amino-acid solubility. The electrolyte Perturbed-Chain Statistical Association Theory (ePC-SAFT) was applied to model thermodynamic properties in aqueous electrolyte/amino-acid solutions. In previous works, this model had been applied to binary salt/water and binary amino acid/water systems. Without fitting any additional parameters, osmotic coefficients and amino-acid solubility in the ternary electrolyte/amino acid/water systems could be predicted with overall deviations of 3.7% and 9.3%, respectively, compared to the experimental data. © 2013 Elsevier Ltd. All rights reserved.
    view abstract10.1016/j.jct.2013.08.018
  • Modeling imidazolium-based ionic liquids with ePC-SAFT. Part II. Application to H2S and synthesis-gas components
    Ji, X. and Held, C. and Sadowski, G.
    Fluid Phase Equilibria 363 (2014)
    ePC-SAFT was used to model the gas solubility in ionic liquids (ILs). The gases under consideration were CO, H2, H2S and O2, and the imidazolium-based ILs studied were [Cnmim][Tf2N], [Cnmim][PF6] and [Cnmim][BF4] (n=2, 4, 6 and 8). For the ePC-SAFT modeling, each IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. CO, H2 and O2 were modeled as non-spherical molecules exerting repulsive and dispersive forces, and H2S was modeled as a non-spherical, associating molecule. ePC-SAFT reasonably predicts the gas solubility in the considered gas/IL mixtures. In order to describe the experimental gas solubilities quantitatively in a broad temperature and pressure range, one ion-specific binary interaction parameter between the IL-anion and the gas was applied, which was allowed to depend linearly on temperature. © 2013.
    view abstract10.1016/j.fluid.2013.11.019
  • Modeling the viscosity of ionic liquids with the electrolyte perturbed-chain statistical association fluid theory
    Shen, G. and Held, C. and Mikkola, J.-P. and Lu, X. and Ji, X.
    Industrial and Engineering Chemistry Research 53 (2014)
    In this work, the friction theory (FT) and free volume theory (FVT) were combined with the electrolyte perturbed-chain statistical association fluid theory (ePC-SAFT) in order to model the viscosity of pure ionic liquids (ILs) and IL/CO2 mixtures in a wide temperature and pressure (up to 3000 bar) range and with viscosities up to 4000 mPa·s. The ePC-SAFT pure-component parameters for the considered imidazolium-based ILs were adopted from our previous work. These parameters were used to calculate the density and residual pressure of the pure ILs. The density and pressure were then used as inputs for pure-IL viscosity modeling using FVT or FT, respectively. The viscosity-model parameters of FT and FVT were obtained by fitting to experimental viscosity data of imidazolium-based ILs and linearized with the molecular weight of the IL-cation. As a result, the FT viscosity model can more accurately describe the experimental viscosity data of pure ILs than the FVT model, at the cost of an increased number of parameters used in the FT viscosity model. Finally, FT and FVT were applied to model the viscosities of IL/CO2 mixtures in good agreement to experimental data by adjusting one binary viscosity-model parameter between the IL-anion and CO2. The application of FT required fitting the viscosity model parameters of pure ILs to experimental viscosity data of pure ILs and of IL/CO2 mixtures. In contrast, the FVT viscosity model parameters were adjusted to the experimental viscosity data of pure ILs only. © 2014 American Chemical Society.
    view abstract10.1021/ie503485h
  • Thermodynamic properties of aqueous glucose-urea-salt systems
    Sadeghi, M. and Held, C. and Ghotbi, C. and Abdekhodaie, M.J. and Sadowski, G.
    Journal of Solution Chemistry 43 (2014)
    In this work, the thermodynamic behavior of aqueous solutions containing the solutes NaCl, glucose, and/or urea is investigated. These substances are vital components for living bodies and further they are main components of blood serum. Osmotic coefficients were determined by cryoscopic measurements in single-solute and multi-solute aqueous solutions containing salts (NaCl, KCl, CaCl2), glucose, and/or urea. The results show that NaCl determines the osmotic coefficients in the urea/glucose/NaCl/water system. Investigation of the effect of different salts on osmotic coefficients revealed ion-specific effects. At physiologically important solute concentrations in typical blood serum solutions, the osmotic coefficients were found to be in the range of 0.90-0.93. In a second step, the state of water in different glucose/salt/water and urea/salt/water systems was investigated. Depending on the kind of salt, the chemical potential of water in urea/salt/water is either higher or lower than in glucose/salt/water systems at equal nonelectrolyte concentrations. This result was found to be independent of the salt molality. Finally, the investigated systems were modeled with the Pitzer model and the ePC-SAFT equation of state, which allowed predicting of the properties of these multi-solute aqueous solutions. © 2014 Springer Science+Business Media New York.
    view abstract10.1007/s10953-014-0192-1
  • Vapor-liquid equilibria of water + alkylimidazolium-based ionic liquids: Measurements and perturbed-chain statistical associating fluid theory modeling
    Passos, H. and Khan, I. and Mutelet, F. and Oliveira, M.B. and Carvalho, P.J. and Santos, L.M.N.B.F. and Held, C. and Sadowski, G. and Freire, M.G. and Coutinho, J.A.P.
    Industrial and Engineering Chemistry Research 53 (2014)
    The industrial application of ionic liquids (ILs) requires the knowledge of their physical properties and phase behavior. This work addresses the experimental determination of the vapor-liquid equilibria (VLE) of binary systems composed of water + imidazolium-based ILs. The ILs under consideration are 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3- methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium methanesulfonate, and 1-butyl-3-methylimidazolium acetate, which allows the evaluation of the influence of the IL anion through the phase behavior. Isobaric VLE data were measured at 0.05, 0.07, and 0.1 MPa for IL mole fractions ranging between 0 and 0.7. The observed increase in the boiling temperatures of the mixtures is related with the strength of the interaction between the IL anion and water. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was further used to describe the obtained experimental data. The ILs were treated as molecular associating species with two association sites per IL. The model parameters for the pure fluids and the binary interaction parameter k ij between water and ILs were determined by a simultaneous fitting to pure-IL densities, water activity coefficients at 298.15 K and VLE data at 0.1 MPa. Pure-IL densities, water activity coefficients, and VLE data were well described by PC-SAFT in broad temperature, pressure, and composition ranges. The PC-SAFT parameters were applied to predict the water activity coefficients at infinite dilution in ILs, and a satisfactory prediction of experimental data was observed. © 2014 American Chemical Society.
    view abstract10.1021/ie4041093
  • Liquid-liquid equilibria of 1-butanol/water/IL systems
    Nann, A. and Held, C. and Sadowski, G.
    Industrial and Engineering Chemistry Research 52 (2013)
    The liquid-liquid equilibria (LLE) of ternary 1-butanol/water/ionic liquid (IL) mixtures were measured and predicted. The LLE data were measured for ternary mixtures containing 1-butanol, water, and one of the following ILs: 1-decyl-3-methylimidazolium tetracyanoborate ([Im10.1] +[tcb]-), 4-decyl-4-methylmorpholinium tetracyanoborate ([Mo10.1]+[tcb]-), 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Im10.1]+[ntf 2]-), and 4-decyl-4-methylmorpholinium bis(trifluoromethylsulfonyl)imide ([Mo10.1]+[ntf 2]-). The LLE data were determined at atmospheric pressure for two different temperatures (308.15 and 323.15 K). To evaluate the application of the ILs studied to the extraction of 1-butanol from aqueous solutions, the 1-butanol distribution coefficients and selectivities were determined from the data. The perturbed-chain statistical associating fluid theory (PC-SAFT) was used for modeling. Previously published pure-component PC-SAFT parameters for the ILs [ J. Phys. Chem. B 2013, 117 (11), 3173-3185 ] were used for this purpose. The binary interaction parameters for 1-butanol/IL pairs were set to zero. The binary interaction parameters for 1-butanol/water and water/IL pairs were determined by fitting to the respective binary LLE data at various temperatures. Without introducing any additional parameters or refitting existing PC-SAFT parameters, the liquid-liquid equilibria of the ternary 1-butanol/water/IL mixtures were predicted and exhibited good agreement with the experimental data. Moreover, the very sensitive property distribution coefficient and the selectivity of 1-butanol were accurately predicted. © 2013 American Chemical Society.
    view abstract10.1021/ie403246e
  • Modeling thermodynamic properties of aqueous single-solute and multi-solute sugar solutions with PC-SAFT
    Held, C. and Sadowski, G. and Carneiro, A. and Rodríguez, O. and Macedo, E.A.
    AIChE Journal 59 (2013)
    The Perturbed-Chain Statistical Association Fluid Theory is applied to simultaneously describe various thermodynamic properties (solution density, osmotic coefficient, solubility) of aqueous solutions containing a monosaccharide or a disaccharide. The 13 sugars considered within this work are: glucose, fructose, fucose, xylose, maltose, mannitol, mannose, sorbitol, xylitol, galactose, lactose, trehalose, and sucrose. Four adjustable parameters (three pure-sugar parameters and a kij between sugar and water that was allowed to depend linearly on temperature) were obtained from solution densities and osmotic coefficients of binary sugar/water solutions at 298.15 K available in literature. Using these parameters, the sugar solubility in water and in ethanol could be predicted satisfactorily. Further, osmotic coefficients and solubility in aqueous solutions containing two solutes (sugar/sugar, sugar/salt) were predicted (no additional kij parameters between the two solutes) reasonably. The model was also applied to predict the solubility of a sugar in a solvent mixture (e.g., water/ethanol) without additional fitting parameters. © 2013 American Institute of Chemical Engineers.
    view abstract10.1002/aic.14212
  • Molecular interactions in 1-butanol + IL solutions by measuring and modeling activity coefficients
    Nann, A. and Mündges, J. and Held, C. and Verevkin, S.P. and Sadowski, G.
    Journal of Physical Chemistry B 117 (2013)
    Molecular interactions in 1-butanol + ionic liquid (IL) solutions have been investigated by measuring and modeling activity-coefficient data. The activity coefficients in binary solutions containing 1-butanol and an IL were determined experimentally: the ILs studied were 1-decyl-3-methyl-imidazolium tetracyanoborate ([Im10.1]+[tcb]-), 4-decyl-4-methyl-morpholinium tetracyanoborate ([Mo10.1] +[tcb]-), 1-decyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([Im10.1]+[ntf 2]-), and 4-decyl-4-methyl-morpholinium bis(trifluoromethylsulfonyl)imide ([Mo10.1]+[ntf 2]-). The methods used to determine the activity coefficients included vapor-pressure osmometry, headspace-gas chromatography, and gas-liquid chromatography. The results from all of these techniques were combined to obtain activity-coefficient data over the entire IL concentration range, and the ion-specific interactions of the ILs investigated were identified with 1-butanol. The highest (1-butanol)-IL interactions of the ILs considered in this work were found for [Im10.1]+[tcb]-; thus, [Im10.1]+[tcb]-showed the highest affinity for 1-butanol in a binary mixture. The experimental data were modeled with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). PC-SAFT was able to accurately describe the pure IL and (1-butanol)-IL data. Moreover, the model was shown to be predictive and extrapolative with respect to concentration and temperature. © 2013 American Chemical Society.
    view abstract10.1021/jp307276y
  • Solubility of sugars and sugar alcohols in ionic liquids: Measurement and PC-SAFT modeling
    Carneiro, A.P. and Held, C. and Rodríguez, O. and Sadowski, G. and Macedo, E.A.
    Journal of Physical Chemistry B 117 (2013)
    Biorefining processes using ionic liquids (ILs) require proper solubility data of biomass-based compounds in ILs, as well as an appropriate thermodynamic approach for the modeling of such data. Carbohydrates and their derivatives such as sugar alcohols represent a class of compounds that could play an important role in biorefining. Thus, in this work, the pure IL density and solubility of xylitol and sorbitol in five different ILs were measured between 288 and 339 K. The ILs under consideration were 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]), Aliquat dicyanamide, trihexyltetradecylphosphonium dicyanamide, and 1-ethyl-3-methylimidazolium trifluoroacetate. Comparison with the literature data was performed, showing good agreement. With the exception of [bmim][DCA], the solubility of these sugar alcohols in the other ILs is presented for the first time. The measured data as well as previously published solubility data of glucose and fructose in these ILs were modeled by means of PC-SAFT using a molecular-based associative approach for ILs. PC-SAFT was used in this work as it has shown to be applicable to model the solubility of xylitol and sorbitol in ILs (Paduszyński;et al. J. Phys. Chem. B 2013, 117, 7034-7046). For this purpose, three pure IL parameters were fitted to pure IL densities, activity coefficients of 1-propanol at infinite dilution in ILs, and/or xylitol solubility in ILs. This approach allows accurate modeling of the pure IL data and the mixture data with only one binary interaction parameter kij between sugar and the IL or sugar alcohol and the IL. In cases where only the pure IL density and activity coefficients of 1-propanol at infinite dilution in ILs were used for the IL parameter estimation, the solubility of the sugars and sugar alcohols in the ILs could be predicted (kij = 0 between sugar and the IL or sugar alcohol and the IL) with reasonable accuracy. © 2013 American Chemical Society.
    view abstract10.1021/jp404864c
  • The role of activity coefficients in bioreaction equilibria: Thermodynamics of methyl ferulate hydrolysis
    Hoffmann, P. and Voges, M. and Held, C. and Sadowski, G.
    Biophysical Chemistry 173-174 (2013)
    The Gibbs energy of reaction (ΔRg) is the key quantity in the thermodynamic characterization of biological reactions. Its calculation requires precise standard Gibbs energy of reaction (ΔRg +) values. The value of ΔRg+ is usually determined by measuring the apparent (concentration-dependent) equilibrium constants K, e.g., the molality-based Km. However, the thermodynamically consistent determination of ΔRg+ requires the thermodynamic (activity-based) equilibrium constant Ka. These values (Km and Ka) are equal only if the ratio of the activity coefficients of the reactants to the activity coefficients of the products (Kγ) is equal to unity. In this work, the impact of Kγ on the estimation of Ka for biological reactions was investigated using methyl ferulate (MF) hydrolysis as a model reaction. The value of Kγ was experimentally determined from Km values that were measured at different reactant concentrations. Moreover, K γ was independently predicted using the thermodynamic model ePC-SAFT. Both the experimentally determined and the predicted K γ values indicate that this value cannot be assumed to be unity in the considered reaction. In fact, in the reaction conditions considered in this work, Kγ was shown to be in the range of 3 < K γ < 6 for different reactant molalities (2 < mmol MF kg- 1 < 10). The inclusion of Kγ and thus the use of the thermodynamically correct Ka value instead of Km lead to remarkable differences (almost 40%) in the determination of ΔRg+. Moreover, the new value for ΔRg+ increases the concentration window at which the reaction can thermodynamically occur. The influence of additives was also investigated both experimentally and theoretically. Both procedures consistently indicated that the addition of NaCl (0 to 1 mol kg- 1 water) moderately decreased the value of Kγ, which means that the values of Km increase and that a higher amount of products is obtained as a result of the addition of salt. Additionally, Km was found to strongly depend on pH. A ten-fold increase in the Km values was observed in the pH range of 6 to 7; this increase corresponds to a change of more than 100% in the value of ΔRg+. © 2013 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.bpc.2012.12.006
  • Measuring and modeling alcohol/salt systems
    Held, C. and Prinz, A. and Wallmeyer, V. and Sadowski, G.
    Chemical Engineering Science 68 (2012)
    Liquid densities, osmotic coefficients, and mean ionic activity coefficients (MIAC) at 25. °C of single-salt alcohol (methanol and ethanol) solutions containing univalent ions were measured and modeled with the ePC-SAFT equation of state. In accordance with our previous work [Held, C., Cameretti, L.F., Sadowski, G., Fluid Phase Equlilib. 270 (2008) 87-96], only two solvent-specific ion parameters were adjusted to experimental solution densities and osmotic coefficients: the solvated ion diameter and the dispersion-energy parameter. ePC-SAFT was able to reproduce experimental data of the respective alcohol/salt systems with reasonable accuracy. Based on the solvent-specific ion-parameter sets, it is possible to predict densities and MIACs in ternary and quaternary water/alcohol(s)/salt solutions by introducing appropriate mixing rules that do not contain any additional fitting parameters. © 2011 Elsevier Ltd.
    view abstract10.1016/j.ces.2011.09.040
  • Thermodynamic properties of aqueous salt containing urea solutions
    Sadeghi, M. and Held, C. and Samieenasab, A. and Ghotbi, C. and Abdekhodaie, M.J. and Taghikhani, V. and Sadowski, G.
    Fluid Phase Equilibria 325 (2012)
    Urea and inorganic ions are present in some of the physiological systems, e.g. urine. Understanding the interactions in urea/salt/water is a preliminary step to shed light on more complicated behavior of multi-component physiological systems. State-of-the-art models as well as thermophysical properties can be applied to understand the interactions in these systems. In order to determine such interactions densities, mean ionic activity coefficients (MIACs), osmotic coefficients, and solubility were measured in aqueous solutions of urea and different salts. Densities were determined at temperatures 293.15, 303.15, and 313.15K for urea concentrations up to 3molal and up to 1molal for NaCl. Osmotic coefficients and MIACs were obtained at 310.15K by using the vapor-pressure osmometry and potentiometry methods, respectively. Ternary aqueous urea solutions containing NaCl, KCl, NaBr, KBr, LiBr, NaNO 3, and LiNO 3 at two different concentrations of urea (0.3 and 1molal) as well as at three salt concentrations (0.25, 0.5, and 0.75molal) were considered. Moreover, urea solubility was also measured at 310.15K in 3 and 5molal NaCl solutions in the present work. Experimental data obtained in this work showed that the salt primarily dictates the volumetric properties and the MIAC while the solute with higher concentration determines the behavior of osmotic coefficients in these solutions. The ePC-SAFT model (without any adjustable mixture parameter) was used to accurately predict the experimental densities, activity and osmotic coefficients, and solubilities of the studied mixtures. © 2012 Elsevier B.V.
    view abstract10.1016/j.fluid.2012.04.003
  • Measuring and modeling activity coefficients in aqueous amino-acid solutions
    Held, C. and Cameretti, L.F. and Sadowski, G.
    Industrial and Engineering Chemistry Research 50 (2011)
    The perturbed-chain statistical association theory (PC-SAFT) is applied to simultaneously describe various thermodynamic properties (density, vapor-pressure depression, activity coefficient, solubility) of aqueous solutions containing an amino acid or an oligopeptide. The 28 organic compounds considered within this work are glycine, alanine, serine, proline, hydroxyproline, valine, leucine, arginine, lysine, threonine, asparagine, tyrosine, histidine, cysteine, methionine, aspartic acid, glutamic acid, β-ABA, β-isoABA, α-ABA, γ-ABA, β-AVA, γ-AVA, diglycine, triglycine, dialanine, Gly-Ala, and Ala-Gly. If not yet available in literature, amino-acid solubility data and activity coefficients were determined experimentally. To prove the predictivity of PC-SAFT, osmotic coefficients in aqueous solutions containing two amino acids (glycine/valine and alanine/valine) were measured and predicted without applying any additional model parameters. © 2010 American Chemical Society.
    view abstract10.1021/ie100088c
  • Modeling pH and solubilities in aqueous multisolute amino acid solutions
    Grosse Daldrup, J.-B. and Held, C. and Sadowski, G. and Schembecker, G.
    Industrial and Engineering Chemistry Research 50 (2011)
    The solubility of amino acids is highly depending on the prevailing pH value. However, this dependency is neglected in the state-of-the-art modeling of solubilities in multisolute solutions. In order to describe the pH-dependency of the solubilities, the PC-SAFT model is applied to aqueous solutions containing two amino acids accounting for their dissociation/association equilibria. This approach is applied to four ternary mixtures with pronounced pH-dependent solubility behavior allowing for a good description of experimental amino acid solubilities depending on temperature, cosolute concentration, and pH value. The systems considered within this work each contain two amino acids which show big differences in pI, i.e., l-glutamic acid or l/dl-aspartic acid on the one hand and glycine or l-serine on the other hand, respectively. © 2011 American Chemical Society.
    view abstract10.1021/ie1010367
  • Compatible solutes: Thermodynamic properties and biological impact of ectoines and prolines
    Held, C. and Neuhaus, T. and Sadowski, G.
    Biophysical Chemistry 152 (2010)
    Compatible solutes like ectoine and its derivatives are deployed by halophile organisms as osmolytes to sustain the high salt concentration in the environment. This work investigates the relation of the thermodynamic properties of compatible solutes and their impact as osmolytes. The ectoines considered in this work are ectoine, hydroxyectoine, and homoectoine. Besides solution densities (15-45. °C) and solubilities in water (3-80. °C), component activity coefficients in the aqueous solutions were determined in the temperature range between 0 and 50. °C. The latter is important for adjusting a certain water activity and therewith a respective osmotic pressure within a cell. The characteristic effect of ectoines is compared to that of prolines, as well as to that of incompatible solutes as salts and urea. The experimental results show that the influence on the activity (coefficient) of water is quite different for compatible and incompatible solutes: whereas compatible solutes cause decreasing water activity coefficients, incompatible solutes lead to an increase in water activity coefficients. Based on this quantity, the paper discusses the impact of various osmolytes on biological systems and contributes to the explanation why some osmolytes are more often and at other temperatures used than others. Moreover, it was found that the anti-stress effect of an osmolyte is weakened in the presence of a salt.Finally, it is shown that the thermodynamic properties of compatible solutes can be modeled and even predicted using the thermodynamic model PC-SAFT (Perturbed-Chain Statistical Associating Fluid Theory). © 2010 Elsevier B.V.
    view abstract10.1016/j.bpc.2010.07.003
  • Measurement and modeling solubility of aqueous multisolute amino-acid solutions
    Daldrup, J.-B.G. and Held, C. and Ruether, F. and Schembecker, G. and Sadowski, G.
    Industrial and Engineering Chemistry Research 49 (2010)
    The solubilities of the ternary mixtures L-alanine/L-leucine, L-alanine/L-valine, and L-leucine/L-valine in water were measured at 303 and 323 K. The solubilities of seven binary, eight ternary, and one quaternary aminoacid systems were modeled using the PC-SAFT equation of state. For this purpose, new parameters for L-aspartic acid, L-glutamic acid, L-leucine, and L-tyrosine are presented. The model excellently reproduces binary solubility data with a linear temperature-dependent binary interaction parameter for the solute-solvent interaction. PCSAFT allows for a very good prediction of the solubility behavior of ternary mixtures over a wide range of temperature and concentration. The aqueous mixture with three amino acids is then predicted without any further adjustment with an average relative deviation of 3.34%. © 2010 American Chemical Society.
    view abstract10.1021/ie900913c
  • activity coefficients

  • electrolytes

  • phase equilibria

  • solvation

  • thermodynamics

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