At present, nitrogen production from air by pressure swing adsorption (PSA) is simulated almost exclusively at low product purity levels (< 99% N2). However, with increasing global demand for highly purified gases provided by energy-efficient separation processes the requirement for either extensive experimental research in the high-purity range or predictive computer simulations arises. This paper presents a mathematical model of a twin-bed PSA plant equipped with a carbon molecular sieve (Shirasagi MSC CT-350) for the generation of high-purity nitrogen (99.9–99.999% N2). The model is implemented in the process simulator Aspen Adsorption™. The influence of operating conditions as well as the cycle organisation on the process performance is validated, especially the influence of pressure, temperature, half-cycle time, purge flow rate, and cutting time. The precision of the performance prediction by numerical simulations is critically discussed. Based on the new insights efficiency improvement strategies with a focus on reduced energy consumption are introduced and discussed by means of radar charts. © 2021, The Author(s).

In addition to the adsorption mechanism, the heat released during exothermic adsorption influences the chemical reactions that follow during heterogeneous catalysis. Both steps depend on the structure and surface chemistry of the catalyst. An example of a typical catalyst is the faujasite zeolite. For faujasite zeolites, the influence of the Si/Al ratio and the number of Na+ and Ca2+ cations on the heat of adsorption was therefore investigated in a systematic study. A comparison between a NaX (Sodium type X faujasite) and a NaY (Sodium type Y faujasite) zeolite reveals that a higher Si/Al ratio and therefore a smaller number of the cations in faujasite zeolites leads to lower loadings and heats. The exchange of Na+ cations for Ca2+ cations also has an influence on the adsorption process. Loadings and heats first decrease slightly at a low degree of exchange and increase significantly with higher calcium contents. If stronger interactions are required for heterogeneous catalysis, then the CaNaX zeolites must have a degree of exchange above 53%. The energetic contributions show that the highest‐quality adsorption sites III and III’ make a contribution to the load‐dependent heat of adsorption, which is about 1.4 times (site III) and about 1.8 times (site III’) larger than that of adsorption site II. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

In this work, the influence of water on the adsorption of mercury is systematically investigated on basic and washed activated carbons. Breakthrough curves were measured and temperature-programmed desorption (TPD) experiments were performed with mercury and water. Both physisorptive and chemisorptive interactions are relevant in the adsorption of mercury. The experiments show that the presence of water in the pores promotes chemisorption of mercury on washed activated carbons while there is little influence on chemisorption on basic materials. Washing exposes or forms oxygen functional groups that are chemisorptive sites for mercury. Obviously, effective chemisorption of mercury requires both the presence of water and of oxygen functional groups. As mercury chemisorption is preceded by a physisorptive step, higher physisorptive mercury loading at lower temperature (30 °C) enhances chemisorption though the reaction rate constant is smaller than at higher temperature (100 °C). Sequential adsorption and partial desorption of water at lower temperature changes the surface chemistry without inhibiting mercury physisorption. Here, the highest chemisorption rates were found. The number of desorption peaks in the TPD experiments corresponds to the number of adsorption and desorption mechanisms with different oxygen functional groups in the presence of water. The results of the TPD experiments were simulated using a transport model extended by an approach for chemisorption. The simulation results provide reaction parameters (activation energy, frequency factor, and reaction order) of each mechanism. As in many heterogeneously catalyzed reactions, the activation energy and the frequency factor are independent of mercury loading and increase with increasing temperature. © 2021 The Authors. Published by American Chemical Society.

Hydrogen sulfide is removed from natural gas via adsorption on zeolites. The process operates very effectively, but there is still potential for improvement. Therefore, in this article, the adsorption of hydrogen sulfide was investigated on eight LTA zeolites with different cation compositions. Starting with the zeolite NaA (4 A), which contains only Na+ cations, the Ca2+ cation content was gradually increased by ion exchange. Equilibrium isotherms from cumulative breakthrough curve experiments in a fixed-bed adsorber at 25°C and 85°C at 1.3 bar (abs.) were determined in the trace range up to a concentration of 2000 ppmmol. From a comparison of the isotherms of the different materials, a mechanistic proposal for the adsorption is developed, taking into account the specific positions of the cations in the zeolite lattice when the degree of exchange is increased. The shape of the isotherms indicates two energetically different types of adsorption sites. It is assumed that two mechanisms are superimposed: a chemisorptive mechanism with dissociation of hydrogen sulfide and covalent bonding of the proton and the hydrogen sulfide ion to the zeolite lattice and a physisorptive mechanism by electrostatic interaction with the cations in the lattice. As the degree of exchange increases, the proportion of chemisorption sites seems to decrease. Above an exchange degree of 50%, only evidence of physisorption can be found. It is shown that this finding points to the involvement of weakly bound sodium cations at cation position III in the chemisorption of hydrogen sulfide. © 2021 Annika Starke et al.

With increasing nitrogen purity, PSA plants require an over-proportional air demand with the consequence that high-purity PSA systems engender a distinct interest in energy-saving measures. This paper presents process intensification strategies with the focus on a reduced energy consumption. Therefore, the influence of PSA configuration and cycle organisation on process performance was investigated. Results are presented at two product purity levels (10 ppm/1000 ppm O2) and two operating temperatures (25 °C/45 °C) in a lab-scale twin bed PSA (2 × 2 L). It is shown that dedicated strategies are available to intensify the PSA process; however, their effects are dependent on ambient conditions and product purity levels. © 2021, The Author(s).

In technical processes, fixed-bed adsorbers with impregnated activated carbon are used for chemisorptive mercury separation. In the case of discontinuous waste gas streams with strongly varying mercury concentrations (e.g., in crematories or metal-recycling plants), mercury may quickly break through the impregnated activated carbon layer due to the slow kinetics of chemisorptive adsorption. Under these conditions a promising purification concept is a multilayer adsorber. In the first layer, strongly fluctuating mercury concentrations should first be smoothed by physical adsorption and desorption on nonimpregnated activated carbon before the mercury is completely separated in the second layer of impregnated activated carbon by chemisorption. In this paper, experimentally validated dynamic simulations are used to show that, under suitable operating conditions and design parameters, effective smoothing of fluctuating mercury concentrations is possible in the first layer of a multilayer adsorber with nonimpregnated activated carbons. © 2021 The Authors. Published by American Chemical Society.

To establish a standardized method for specifying mercury in solid samples, a database of relevant mercury species is created via thermo-desorption. By measuring Hg(t) and Hg(0), different evaporation characteristics of mercury halides, sulfide, oxides, nitrates, and sulfates were recorded. It was possible to create a baseline for analyzing solid samples with unknown mercury content. All mercury species without a halide compound evaporate over 200 °C and as elemental mercury. All mercury halides evaporate mainly as oxidized species. From this fact it can be concluded that mercury halides desublimate when heated and have a vapor pressure as a solid. This unique characteristic was only seen by mercury halides. All other species seem to decompose into their single components when heated. © 2021 Wiley-VCH GmbH

In a systematic experimental work, the adsorption of linear, branched and cyclic C5 and C6 hydrocarbons on the zeolites 13X-APG and HiSiv 3000 and the activated carbon Norit R1 Extra is studied. By simultaneous measurement of adsorption capacities and load-dependent enthalpies of adsorption using a self-developed sensor gas calorimeter a deep knowledge about the energetic strength of interactions in adsorption is gained. A special focus is laid on the discussion of the influence of pore geometry and surface chemistry of the adsorbents as well as the molecular structure and binding types of the adsorptives used. Depending on the pore geometry and the surface chemistry of the adsorbents, the load-dependent enthalpies of adsorption show different shapes. While the enthalpies of adsorption on the Faujasite zeolite increase with loading, they are independent of loading on the ZSM-5 zeolite and decrease on the activated carbon. On both zeolites the cyclic and branched adsorptive molecules show lower enthalpies of adsorption compared to the linear molecules due to a less favorable arrangement on the surface. On activated carbon, the enthalpies of adsorption of linear and cyclic hydrocarbons are comparable and significantly higher than those of branched hydrocarbons. For molecules with C=C double bonds only 13X-APG showed higher enthalpies of adsorption and thus stronger interactions. © 2020 Elsevier Inc.

The separation of short-chained alkanes and alkenes is challenging because of their chemical similarity and thus being costly in energy. The implementation of a cryogenic adsorption process may overcome this problem, but systematic studies on light hydrocarbon adsorption at low temperatures are virtually lacking. Therefore, as a first step, in this paper, we present single-component adsorption isotherms of ethane, ethylene, propane, and propylene on activated carbon (AC) and zeolite 13X for temperatures of-80 to +20 °C and partial pressures of 5-1250 Pa. Based on these experimental data, the interactions of the adsorptives with the chemically different surfaces and their temperature dependence are discussed. Results show a strong increase in capacity with decreasing temperature for both AC and zeolite 13X. Cryogenic adsorption increases the overall (calculated) selectivity of alkane-alkene separation, especially for the zeolite 13X. Copyright © 2020 American Chemical Society.

An anthracite-based material of low porosity was activated in a nitrogen stream enriched with water vapor to produce four activated carbons, which differ systematically in their structural and chemical properties. Characterization of the structural properties of the base and the activated materials was carried out by volumetric measurements and mercury porosimetry. A general classification of chemical composition was done by ultimate analysis. The surface chemistry was analyzed by Boehm titration. The adsorption performance was investigated by measuring excess isotherms and load-dependent adsorption enthalpies of selected probe molecules: acetone (polar), n-heptane (non-polar) and toluene (aromatic). Assuming distribution rules for selective adsorption, the molar ratios of the surface groups were estimated from the excess isotherms. The combination of these methods enables the observation and differentiation of structural and surface chemical changes of the carbons during activation. For example, it could be shown that the broader pore width distribution with an increasing proportion of mesopores occurring in the course of activation leads to a more pronounced energetic heterogeneity. It was also found that an increase in surface area with increasing activation time is accompanied by an increase in aromatic surface groups and a reduction of polar and non-polar surface groups. Especially the adsorption of the polar probe molecule acetone revealed the heterogeneity of the surface chemistry, which together with the heterogeneous structural composition resulted in a distinct decrease of the adsorption enthalpy with increasing loading. © 2020 Elsevier Inc.

Both physisorptive and chemisorptive mechanisms play a role in the adsorption of mercury. The present publication investigates the influence of oxygen on the adsorption of Hg0 by breakthrough curve measurements and temperature-programmed desorption (TPD) experiments. The presence of O2 in the gas phase promotes chemisorption. Because of slow adsorption mechanisms, no equilibrium capacities of mercury chemisorption can be determined. For further investigations, coupled adsorption and desorption experiments with concentration swing adsorption and TPD experiments are performed. The results of TPD experiments are simulated and quantitatively evaluated by means of an extended transport model. From the number of desorption peaks, we obtain the number of different adsorption and desorption mechanisms. A detailed simulation of the peaks yields the reaction order, the frequency factor, and the activation energy of the desorption steps. The kinetic reaction parameters allow a mechanistic interpretation of the adsorption and desorption processes. Here, we suppose the formation of a complex between the carbon surface, mercury, and oxygen. Copyright © 2020 American Chemical Society.

The global demand on highly purified gases provided by energy-efficient separation processes grows steadily since decades. An example of particular industrial relevance is nitrogen generated by pressure swing adsorption from compressed air. A kinetically based separation of oxygen from nitrogen is possible by means of carbon molecular sieves (CMS) since oxygen adsorbs remarkably faster in CMS than nitrogen. Even high product purities (5–1000 ppm O2) are easily achievable in commercial generators. However, only a few studies present experimental findings in this purity range. That comes as no surprise, since experimental conditions are not standardised and the determination of N2-PSA performance indicators still creates an experimental challenge. Moreover, the design of the set-up remarkably influences the experimental results. Thus it is the motivation of this study to develop a multi-step strategy, comprising the definition of a reference process, the derivation of explicit and implicit performance indicators based on either flow meter readings or macroscopic material balances, a verification strategy for experimentally obtained data, and an error consideration, which advices accuracy requirements for analysers and flow meters. The effect of cycle time and operating temperature on the performance indicators is exemplarily studied at high purities by means of the proposed strategy. © 2020, The Author(s).

In comparison to the adsorption of hydrocarbons, the adsorption of mercury on activated carbons reveals many unexpected results. Both physisorptive and chemisorptive mechanisms play a role even in the adsorption on nonimpregnated activated carbons. In this work, the adsorption of Hg 0 from a N 2 carrier gas stream is studied on three commercial adsorbents. Single and cumulative breakthrough curves are measured in a fixed bed at temperatures of 25-100 °C and mercury concentrations of 50-1000 μg m -3 . Isosteric heats of adsorption are calculated from the measured adsorption isotherms. Here, adsorption enthalpies in the range of 50% of the vaporization enthalpy are determined. In addition, desorption experiments are conducted to distinguish the contributions of physisorption and chemisorption. A dynamic simulation of experimental breakthrough curves yields diffusion coefficients, which are discussed with respect to the concentration and temperature dependence of diffusion mechanisms in mercury physisorption. © 2019 American Chemical Society.

For environmental and occupational safety reasons, the inhalation anesthetic isoflurane must be removed from indoor air in hospitals. The present work investigated experimentally the coadsorption of isoflurane and water on four different commercial adsorbents: two activated carbons and two zeolites. Adsorption isotherms from dry and humid atmosphere are shown and discussed, i.e., mixture data are compared with those of the pure substances. For all four adsorbents the dominant parameter regarding structural properties is the pore size distribution. In the case of the zeolites, the surface chemistry, especially the aluminum content, plays a role, too. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Activated carbons are widely used as commercial adsorbents. Thermal or chemical activation creates a pore system and functional groups on the inner surface which may significantly change adsorption properties. Therefore, in addition to knowledge of the structural properties, a sound understanding of surface chemistry is indispensable. This paper summarizes the state of art as well as new developments in both fields. Standardized methods for characterizing structural properties are volumetric measurements and mercury porosimetry. To get a more detailed insight into the region of micropores, a probe molecule method was developed. For characterization of surface chemistry, methods such as IR spectroscopy, temperature-programmed desorption, and Boehm titration are subject of research. Novel methods were developed such as measuring of excess isotherms and calorimetric measurement of heat of adsorption, which are presented and discussed in greater detail in this paper. As each single method can only provide limited information, a better description of surface chemistry requires combination and careful interpretation of complementary information from different methods. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In mercury adsorption on activated carbons both physisorptive and chemisorptive mechanisms play a role. The systematic investigation of Hg0 chemisorption is difficult because equilibrium capacities cannot be determined due to slow adsorption mechanisms. Therefore, the present publication suggests a three-step approach: 1) Breakthrough curves are used to assess the dynamics of Hg0 adsorption. 2) The contributions of physisorption and chemisorption can be distinguished by coupled adsorption and desorption experiments. 3) Temperature programmed desorption (TPD) experiments are performed to get information about specific chemisorptive binding sites on the surface. This approach was tested on four characteristic examples of impregnated and non-impregnated activated carbons. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In conventional reverse osmosis processes for seawater desalination, a disinfection of the process stream with chlorine compounds is carried out for antifouling. After disinfection the reduction agent Na2S2O5 is used for the removal of residual chlorine in a strongly overstoichiometric way in order to protect the membranes from oxidational damages. To save chemicals a controlled dosing of Na2S2O5 based on a reliable concentration measurement is desirable. Therefore, a measuring method for the determination of the sulfur(IV) components bisulfite and sulfite in seawater is developed based on the combination of UV spectroscopy and a PLS regression method. Experimental results as well as the development of the regression model for sulfur species in ultrapure and seawater is described. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

To enable the technical use of natural gas, efficient gas processing is essential. Various components such as water, sulphur compounds, carbon dioxide, nitrogen, and heavy hydrocarbons must be removed. Temperature swing adsorption (TSA) is a commonly used way of removing some of these components. This paper describes where TSA is used in the natural gas treatment process and outlines the application of commercial adsorbents in TSA plants. The state of research on adsorbents and process control in TSA plants in natural gas processing is discussed. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

During the adsorptive separation of light hydrocarbons in the trace range, significant coadsorption of the carrier gas may occur due to low temperatures and much higher concentrations of the carrier gas compared to the adsorptive. This results in a reduction of the adsorbent's capacity, which leads to problems in industrial adsorber design and an incorrect interpretation of adsorption mechanisms. So far, there are only few studies on the carrier gas influence, and no data exist for low temperatures. In this work, we present experimental adsorption isotherms of methane and ethane from nitrogen and helium at temperatures between-80 and +20 °C on activated carbon and zeolite 13X. A comparison of the adsorption isotherms and the isosteric adsorption enthalpy reveals that coadsorption increases strongly with low temperatures, low partial pressures, and weak interactions between adsorptive and adsorbent. Finally, coadsorption is shown to be stronger on activated carbon than on zeolite 13X. © 2019 American Chemical Society.

The removal of light hydrocarbons from exhaust air and process gas is important for a variety of applications, e.g., in natural-gas treatment. However, particularly at lower concentrations, the removal of C1 and C2 hydrocarbons is either very expensive or unfeasible with standard technology. Adsorption processes at temperatures below 0 °C may provide a technical solution, but until today, no systematic study on the dynamics of trace adsorption at low temperatures is available. Therefore, in this work, we present breakthrough curve experiments of ethane, propane, and n-butane over a temperature range from +20 to -80 °C and a concentration range from 5 to 1000 Pa on microporous activated carbon. Equilibrium loadings are calculated and modeled with the temperature-dependent Toth equation. From dynamic simulations of the experimental breakthrough curves, kinetic parameters are determined. The lowering of temperature results in the slowdown of kinetics, which, however, is overcompensated by a simultaneous capacity gain. © 2018 American Chemical Society.

In natural gas processing, adsorptive units remove higher hydrocarbons from the crude gas, for example to avoid freezing in consecutive cryogenic units. This article describes a detailed investigation on the adsorption of C6 hydrocarbons (benzene, cyclohexane, n-hexane) at low concentrations up to 5000 ppmmol in a N2 carrier gas on two industrial produced silica alumina gels. Adsorption isotherms were derived from cumulative breakthrough experiments in a fixed-bed adsorber between 25 °C and 75 °C and 1.3 bar (abs.). The isosteric heat of adsorption was determined from the temperature-dependent isotherms. Furthermore an adsorption potential model was developed to describe the temperature dependency of equilibrium capacity and heat of adsorption. The paper discusses the experimental data with respect to molecular structure of the adsorptives as well as surface chemistry and pore structure of the adsorbents. In comparison to the other adsorptives, the aromatic benzene exhibits the highest loadings and the highest heat of adsorption. In addition it shows the strongest load- and temperature-dependency of the heat of adsorption. © 2018 Elsevier Inc.

To ensure the technical use of natural gas, heavy hydrocarbons and other components must be separated. Therefore, in this work the adsorption of C6-C8 hydrocarbons n-hexane, n-heptane, n-octane, benzene, toluene, and cyclohexane on a commercial silica-alumina gel (Sorbead H) was investigated in experiments and dynamic simulations. Single and binary mixture equilibrium isotherms were determined from cumulative breakthrough curve experiments on a fixed bed adsorber at 25-75 °C and 1.3 bar (abs) in the trace range up to approximately 5000 ppmmol. The adsorption behavior is interpreted on the basis of the molecular structure of the adsorptive, the surface chemistry, and the pore structure of the adsorbents. Binary mixture isotherms were calculated using the theory of the ideal adsorbed solution (IAST). The results were in good agreement with experimental data. The adsorption dynamics was investigated by breakthrough curve experiments and simulated dynamically using an isothermal model based on mass balances and a linear driving force (LDF) model for adsorption kinetics. © 2018 American Chemical Society.

To ensure the technical use of natural gas it is necessary to remove heavy (cyclic) hydrocarbons from the crude gas. In this article the adsorption of two cyclic hydrocarbons in a N2-carrier gas is investigated on two commercial silica alumina gels. Adsorption isotherms are determined from cumulative breakthrough experiments in a fixed-bed adsorber. The isosteric heat of adsorption is calculated from the temperature-dependent isotherms. The experimental data is discussed regarding the molecular structure of the adsorptive agents as well as surface chemistry and pore structure of the adsorbents. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

This paper presents adsorption isotherms and desorption data of halogenated ethers (desflurane, isoflurane, and sevoflurane), which are used as inhalation anesthetics, and aliphatic ethers (diethyl ether and methyl propyl ether) from a nitrogen carrier gas stream. The isotherms were measured at 25 °C and 1 bar. Desorption was analyzed at temperatures between 25 and 250 °C. Zeolites with different structure and aluminum content as well as activated carbons with different pore size distributions were used as adsorbents. The analysis of the adsorption isotherms and the desorption data focuses on the interactions between adsorptive molecules and adsorbents' surfaces. We discuss the specific influence of the molecular structure and polarity of the adsorptives as well as of the pore structure and surface chemistry of the adsorbents. © 2017 American Chemical Society.

An industrially widely used technology for the removal of condensable components like water and mercaptans from natural gas is cyclic temperature swing adsorption. Optimized design of these coupled adsorption-desorption processes requires detailed knowledge of desorption properties of the used adsorbents. Therefore, the desorption behavior of water, methyl mercaptan, and ethyl mercaptan was investigated on a commercial silica alumina gel. In dynamic experiments, a preloaded fixed bed was regenerated with hot purge gas (300 degrees C), and time-dependent concentration and temperature profiles were measured and discussed by means of equilibrium theory. Characteristic plateau temperatures were found between 43 and 63 degrees C, rising with the adsorption affinity. Experiments with competitive adsorption of water and mercaptans show that process dynamics are mainly controlled by water. The results are evaluated with regard to technical relevance.

To investigate the load-dependent heat of adsorption a sensor gas calorimeter was developed which allows the simultaneous measurement of adsorption capacity and heat of adsorption in porous materials. A commercially available volumetric measurement device was extended by a newly developed calorimetric measuring cell. Using this apparatus, the load-dependent heat of adsorption of alkanes and alkenes on the zeolites 13X-APG and HiSiv 3000 as well as on the activated carbon Norit R1 Extra was investigated. On all three adsorbents the heat of adsorption increases with chain length of the hydrocarbons. On HiSiv 3000 and Norit R1 Extra both load and heat of adsorption for all investigated alkanes and alkenes of the same chain length are very similar due to similar interactions with the adsorbent surface. Presumably dispersion interactions dominate adsorption in these systems. Contrary to these findings on 13X-APG higher loads and enthalpies of adsorption for alkenes than for alkanes occur. These higher heats of adsorption can be attributed to the energetically more attractive quadrupole-cation interactions between the double bond of alkenes and the cations of the zeolite. � 2017 Elsevier Inc.

After presenting the most promising continuous adsorption cooling topology for air-conditioning of a passenger cabin, a transient, 3D model is proposed, based on a modified linear driving force approach, to simulate an adsorption process in a SAPO-34-coated open-celled aluminum foam. The simulation is executed in ANSYS CFX 15.0 and the additional model equations are implemented through the CFX expression language. As a result the influence of the pore diameter onto the system simulation and the mass transport limitation is shown and the sensitivity concerning the pressure in the gas phase adsorption is confirmed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Removing of trace-leveled light hydrocarbons from exhaust air or gas streams becomes an increasingly important issue in the field of process and environmental technology, e.g., storage and transport of liquefied natural gas. Adsorption processes at temperatures below 0°C have great potential to meet process specifications or environmental regulatory limits. Designing of such adsorption processes requires a profound insight into the thermodynamics of adsorption at low temperatures, which is not available yet. Therefore, this work provides adsorption isotherms of ethane, propane, and n-butane on microporous activated carbon and zeolite 13X in a temperature range from -40 to +60°C and at partial pressures from 5 to 1000 Pa. The influence of temperature on the adsorbed amount on activated carbon and zeolite 13X is discussed for each adsorptive considering isosteric heats of adsorption and specific interactions between the adsorptive and the adsorbent surface. (Graph Presented). © 2017 American Chemical Society.

This paper presents adsorption isotherms and desorption data of isoflurane from a carrier gas (nitrogen) on different adsorbents at 25°C and 1 bar. As adsorbents activated carbons, newly developed carbon adsorbents and dealuminated zeolites were used. The adsorption of isoflurane was studied in trace level concentrations up to 1200 ppmV. Common isotherm equations were fitted to the measured data. The adsorption isotherms show distinctly different capacities depending on the polarity and the pore structure of the adsorbent. The investigation of desorption reveals weak physical interactions between isoflurane and the surface of most adsorbents. © 2015 American Chemical Society.

Activated carbons are one of the most common industrial adsorbents in liquid-phase applications. It is known that the surface groups of the activated carbon can have a significant influence on the adsorption process from the liquid phase. Therefore, it is desirable to measure surface groups on activated carbons. This opens up the possibility to use group-contribution methods to model and predict adsorption isotherms. An idea is presented to characterize the inner surface of activated carbons by three types of surface groups: aromatic, polar, and nonpolar surface groups. The amounts of these surface groups were calculated from excess adsorption isotherms of probe molecules on ten activated carbons. This lays the groundwork for further simulation studies of liquid-phase adsorption using group-contribution methods. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

In this publication the authors present an aluminium alloy tank for hydrogen storage using 1921 g of Na3AlH6 doped with 4 mol% of TiCl3 and 8 mol% of activated carbon. The tank and the heat exchangers are manufactured by extrusion moulding of Al-Mg-Si based alloys. EN AW 6082 T6 alloy is used for the tank and a specifically developed alloy with a composition similar to EN AW 6060 T6 is used for the heat exchangers. The three heat exchangers have a corrugated profile to enhance the surface area for heat transfer. The doped complex hydride Na3AlH6 is densified to a powder density of 0.62 g cm−3. The hydrogenation experiments are carried out at 2.5 MPa. During one of the dehydrogenation experiments approximately 38 g of hydrogen is released, accounting for gravimetric hydrogen density of 2.0 mass-%. With this tank 15 hydrogenation and 16 dehydrogenation tests are carried out. © 2016 Elsevier B.V.

A new measuring device for the simultaneous measurement of heat of adsorption and load has been developed. A volumetric adsorption measurement device is extended by a calorimetric unit which measures the pressure difference between two identical sensor gas volumes surrounding a sample cell and a reference cell. Due to the exothermic adsorption a pressure rise in the gas volume around the sample cell is induced. After calibration the heat of adsorption can be calculated from the pressure difference curve. First results of the measurement of the adsorption enthalpy of CO2 on 13X zeolite are shown. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The reduction of NO2 in air at ambient temperatures with activated carbons can be increased by the infiltration of metal oxide nanoparticles into the sorbents. The NO2 is first adsorbed to the activated carbon and subsequently catalytically reduced to physiologically neutral substances by the metal oxides. The catalytic reduction at ambient temperatures is rather slow. In a former study concerning the application in cabin air filters, it was shown that the modification of activated carbon with 5 wt% CuO/ZnO leads to reduced breakthrough of NO2 and that the adsorbent was able to regenerate between repeated NO2 adsorption cycles. Here we show that the efficiency of the sorbent can be more than doubled by increasing the metal oxide infiltration to 20 wt% whereas a further increase in loading yields no additional improvement, due to a partial transformation of the oxidic compounds. © 2016, © The Author(s) 2016.

Besides absorption and membrane processes, temperature swing adsorption (TSA) processes allow for the removal of impurities from gas streams and the recovery of the adsorbed component with high purity. However, especially in the case of large quantities of impurities (e.g., CO2 in flue gas) the TSA processes suffer from their high energetic demand. To reduce this energy demand tube bundle adsorbers with indirectly heated and cooled adsorbent bed were developed. The influence of several parameters on the performance of these adsorbers in a capturing process for CO2 from a dry flue gas is investigated. A detailed 2D model is derived and several parameter sweeps are conducted. It is observed that the inner thermal resistance plays a dominant role on the performance of the process. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new spectroscopic method was developed to measure in situ the concentrations of dissolved sulfur (IV) species from SO2 absorption in electrolyte systems like seawater and desalination brine. In a recent paper we described UV spectroscopic measurements to fit a thermodynamic model yielding a considerably improved description of the absorption equilibrium. Now, combining this model with a comprehensive spectroscopic calibration, the molar absorptivities of the sulfur (IV) species (SO2(aq), HSO- 3, SO2- 3 und SO2Cl-) were determined for a wavelength range from 200 to 350 nm. With the molar absorptivities the concentrations of the sulfur species can be determined straight from a UV spectrum. The validity of the values was cross-checked in different electrolyte systems comparing calculated and measured spectra. The new method yields a very good representation of the species concentrations in SO2 absorption solutions. © 2016 Elsevier B.V.

Adsorption is one of the key technologies for the removal of sulfur compounds in trace levels from natural gas prior to a technical utilization. To improve the design of these coupled adsorption-desorption processes a profound insight into the thermodynamics of adsorption is necessary. Therefore, this article provides adsorption isotherms of ethyl mercaptan, methyl mercaptan, hydrogen sulfide, water, and carbon dioxide on a commercial silica-alumina gel used in natural gas purification. The experimental data spans a temperature range between 25 and 300 °C at concentrations between 0 and 2000 mol-ppm at total pressure of 1.3 bar. Equilibrium capacities and isosteric heats of adsorption are compared and discussed based on an analysis of specific interactions between the adsorptives and the adsorbent's chemical surface functionality. © 2016 American Chemical Society.

Abstract Activated carbons are widely applicable in industrial adsorption processes. However, characterization of their surface properties is problematic due to the number of different source materials and variations in production processes. Here, a model of the carbon surface derived that is based on the knowledge of fundamental molecular interactions on carbon surfaces. Adsorption isotherms of selected probe molecules are measured on different activated carbons and discussed how the model can be applied in the characterization of the surface properties of activated carbons. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A systematic study of the SO<inf>2</inf> solubility of binary systems (SO<inf>2</inf>+water+1 electrolyte) and of the complex mixtures seawater and brine was performed. The experimental setup allowed a comprehensive description of the equilibrium state by a UV spectroscopic measurement of the partial pressure of SO<inf>2</inf> in the gas phase and the concentration of sulfur compounds in the liquid phase. The influence of main ions present in the brine (e.g., Na+, Cl-, K+, Mg2+, Ca2+, HCO<inf>3</inf>-) was studied at 298 and 323K. The experiments revealed considerable deviations of already existing models from experimental data mainly at higher temperatures. A thermodynamic model based on caloric data and a Pitzer and a Sechenov approach for the calculation of activity coefficients was fitted to experimental data. This work demonstrates that fitting selected Pitzer parameters improves the model performance very much. The new model provides a reliable prediction of SO<inf>2</inf> solubility over the entire investigated range of temperature and concentrations. © 2015 Published by Elsevier B.V.

In this paper systematic investigations on the adsorptive drying of primary alcohols from methanol to 1-hexanol on 3A and 4A zeolites are presented. The focus of the work is laid on the superdrying of these polar solvents in the ppmw-region. In addition to equilibrium data gained in shaker bottle experiments information regarding the dynamic drying behavior was obtained by breakthrough experiments. The water content in these experiments was monitored online by a transmission photometer. Based on the experimental data a physical model was developed in order to predict the dynamic drying behavior in a fixed bed adsorber. Most of the investigated systems could be well described by this model. Furthermore pore diffusivities of water could be obtained by fitting the model to the experimental data. The results of this study reveal a clear dependency of the dynamic drying behavior of primary alcohols from the solvent to be dried and the type of zeolite. Small alcohol molecules show significantly faster drying rates than long-chain alcohols and the drying kinetics on a 3A zeolite is much faster than on a 4A zeolite. The experimental results were correlated to the molecular dimensions of adsorptives and the size of the pore openings of the zeolites as well as to the interactions between adsorptive, solvent and adsorbent. © 2015 Elsevier B.V.

The preparation of silica adsorbances from chemical vapor infiltration of activated carbon with tetramethylsilane (TMS) is shown. The method bases on a two step process. In a first step, activated carbons are infiltrated at 943 K in a nitrogen-TMS-vapor atmosphere of 200 mbar. At these conditions, the carbon skeleton is covered with silicon. The resulting material is highly porous and well adapting the surface structure of the carbon templates. It is already partly oxidized at room temperature when coming into contact with air. In a second step, the infiltrated carbons are completely oxidized in air at 853 K. At these conditions, the supporting carbon skeleton is completely burned and the silicon becomes silicon oxide. The resulting materials are highly porous with extremely large surface areas around 835 m2/g. Overall, the novel material seems to well adapt the original macro- and microstructure of the activated carbon used. © 2015 The Authors. Published by Elsevier Inc.

Adsorption processes are frequently applied to separate traces of hazardous and toxic substances from gas streams. Hence, knowledge of sorption characteristics of these substances on standard adsorbents is essential. Sorption of hexanal and acetaldehyde from a nitrogen gas stream in trace concentrations on activated carbon and ordered mesoporous carbon-based adsorbents (CMK) is studied. A magnetic suspension balance and an attached gaschromatograph-mass spectrometer were used to analyze the sorption process both gravimetrically and spectrometrically. Both types of adsorbents show a higher capacity for hexanal than acetaldehyde. The activated carbon exhibits considerable differences in regard to desorption of hexanal compared to the mesoporous CMK. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In industrial practice the iodine number is often used to characterize the adsorptive properties of activated carbons in liquid phase applications. Manufacturers of activated carbons determine the iodine number according to different standards (e.g., CEFIC 2.3 and ASTMD4607). This leads to different experimental protocols being applied to measure the same number. Therefore, activated carbons made by different manufacturers are difficult to compare. This work presents a systematic comparison and a critical assessment of experimental protocols used to determine the iodine number. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Here we present the development of an aluminium alloy based hydrogen storage tank, charged with Ti-doped sodium aluminium hexahydride Na3AlH6. This hydride has a theoretical hydrogen storage capacity of 3 mass-% and can be operated at lower pressure compared to sodium alanate NaAlH4. The tank was made of aluminium alloy EN AW 6082 T6. The heat transfer was realised through an oil flow in a bayonet heat exchanger, manufactured by extrusion moulding from aluminium alloy EN AW 6060 T6. Na3AlH6 is prepared from 4 mol-% TiCl3 doped sodium aluminium tetrahydride NaAlH4 by addition of two moles of sodium hydride NaH in ball milling process. The hydrogen storage tank was filled with 213 g of doped Na3AlH6 in dehydrogenated state. Maximum of 3.6 g (1.7 mass-% of the hydride mass) of hydrogen was released from the hydride at approximately 450 K and the same hydrogen mass was consumed at 2.5 MPa hydrogenation pressure. 45 cycle tests (rehydrogenation and dehydrogenation) were carried out without any failure of the tank or its components. Operation of the tank under real conditions indicated the possibility for applications with stationary HT-PEM fuel cell systems. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Accurate knowledge of an adsorbent's porosity is fundamental for scientific and industrial applications of adsorption technology. Over the last decades many approaches have been established to assess porosity of adsorbent materials by analyzing their nitrogen uptake at 77 K with volumetric measurement devices. Despite using highly sophisticated physical models, all approaches make assumptions on pore shape as well as on the interactions between adsorbent and adsorptive molecules. Subsequently, significant differences in pore size distributions are observed depending on which modeling parameters were used. The molecular probe method presented in this paper therefore restrains to a minimum of approximations by measuring isotherms of chemically similar substances of increasing molecular size. Differences in pore volume can be reduced to sterical limitations in micropores below the size of adsorptive, leading to a high-resolution pore size distribution below 0.7 nm where only few comparable methods exist. The analytical procedure was customized to take account of the amorphous and heterogeneous pore structure of activated carbon. By measuring adsorption isotherms of N2, n-hexane, iso-octane and cyclohexane on various activated carbons, it is shown that differences in pore accessibility of tested adsorptives are specific for each adsorbent. Using molecular probe molecules hence appears to be a promising method for a complementary porosity analysis of activated carbons. © 2014 Elsevier Ltd. All rights reserved.

Chemical vapor infiltration of activated carbon with tetramethylsilane (TMS) at 200 hPa total pressure and a gas phase concentration of 15 (mol-)% TMS in nitrogen is studied. The influence of temperature on the infiltration process is discussed in detail. Up to 873 K, the infiltration is performed in the kinetically controlled regime resulting in high loadings up to around 42 (wt.-)%. The modified materials show high values for BET-surface and pore volume indicating a sufficient adoption of the infiltrated silicon layer to the surface morphology of the carbon substrates. Low oxidation resistance of the infiltrated material and EDX measurements give rise to the assumption that the infiltrated material is silicon. At higher infiltration temperatures above 873 K, particles are formed which have the shape of cylindrical nanostructures. EDX measurements reveal that silicon carbide is produced at these temperatures. © 2014 Elsevier Ltd. All rights reserved.

Accurate knowledge of an adsorbent's porosity is of fundamental importance for scientific and industrial application. Despite using highly sophisticated physical models, all current approaches make assumptions resulting in significant differences in pore size distributions depending on the modeling parameters used. The molecular probe method presented in this paper applies a minimum of approximations. Differences in pore volume can be reduced to sterical limitations in micropores below the size of adsorptive, leading to a high-resolution pore size distribution below 0.7nm where only few comparable methods exist. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Currently no measurement technique is able to provide continuous monitoring of humidity for a wide range of polar solvents. Therefore a feasibility study on humidity measurements in vaporized hydrocarbons using tunable diode laser absorption spectroscopy (TDLAS) is done. In systematic measurements polar and unpolar solvents were vaporized into a hot nitrogen flow and subsequently analyzed in a TDLAS monitor. The experiments show reproducible results for humidity measurements in unpolar liquids like n-hexane, but several problems are occurring in polar primary alcohols. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The processing of iron oxide nanoparticles derived from spray flame synthesis for specific adsorption applications is described. After the as-prepared particles proved the ability for H2S removal in pure gas treatment, two different nanoparticle- based composite materials were prepared. While impregnation of activated carbon with the as-prepared nanoparticles showed the expected increase in H2S adsorption capacities, a significant enhancement in desulfurization performance was observed for a novel iron oxide nanoparticle composite material. H2S adsorption was tested in fixed-bed breakthrough curve measurements. The H2S removal efficiency of the novel material under ambient conditions indicates highly promising properties for potential use in industrial and air pollution control applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption cycles using a shell and tube heat exchanger type adsorber, in which heat integration between the different vessels (hot adsorber and cold adsorber) is considered, are simulated in COMSOL Multiphysics. This heat integration makes this process energetically competitive with an amine wash as a reference process. The feasibility of this process is studied as an alternative for carbon capture. The preliminary results are encouraging making this process an alternative for carbon capture. However, there are still some parameters that require further optimization.

This work focuses on the influence of process parameters on the dynamics of adsorptive water removal from polar organic solvents in a fixed bed adsorber. As a model solvent isopropanol with water concentrations between 5 and 4000 ppmw was used. In a first step equilibrium loadings on 3A and 4A zeolites were determined by shaker bottle experiments. The results were fitted to the Langmuir equation. In a second step fixed bed experiments were carried out in order to characterize the dynamic behavior of the adsorption process. In these experiments 3A zeolite shows a better drying performance than 4A zeolite. The breakthrough curves (BTC) could be well described by dynamic simulations using a set of differential equations for the mass balances and a linear driving force approach (LDF) for the kinetics. Pore diffusivities in the order of 10-12 m2/s were obtained by the simulation, indicating that surface diffusion in the pores of the zeolites is the predominant mechanism of mass transfer. © 2014 Elsevier B.V. All rights reserved.

New periodic mesoporous organosilicas were synthesized using [bis(triethoxysilyl)vinyl]aniline (BTEVA) and [bis(triethoxysilyl)vinyl]benzene (BTEVB) as precursors and by functionalizing the BTEVA PMO with aminopropyl groups. All PMO materials showed a high degree of hexagonal order in the respective P-XRDs as well as high surface areas with narrow pore size distributions. The PMOs together with activated carbon were investigated with regards to their hexanal adsorption capacity in a gravimetric apparatus with an attached GC-MS. For the amine PMOs two different regions during adsorption were found. In the first region loadings in the range of 30 wt% were reached by a fast adsorption process. In the second region the loading reached 50 wt% but with slower kinetics. In desorption experiments up to 150 °C the loading decreased from 50 wt% to 30 wt%, where an equilibrium state was observed. With GC-MS and NMR the first region could be assigned to a chemisorption process, where the hexanal forms an imine group with the amine function in a Schiff base reaction. The subsequent second region can be assigned to weaker and thus reversible physisorption. The total capacity (first and second region) is substantially higher for the amine PMOs than for the activated carbon. Due to the chemical bonding in the chemisorption process, the desorption behavior is completely different: compared to the activated carbon the bonding of hexanal is much stronger for the amine PMOs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prior to the technical use of natural gas, toxic and corrosive components need to be removed. This work provides results from dynamic fixed-bed experiments for the adsorption of sulfurous compounds, CO2 and H 2O from carrier gas (CH4 or N2) on two adsorbents (zeolite 5A, silica-alumina-gel) used in industrial applications. The breakthrough curves were measured at ambient conditions (298 K, 1.3 bar) in a trace level concentration range up to 2000 mol-ppm. Adsorption isotherms were derived using mass balances and a simple linear driving force model was fitted to the curves. Good agreement of experimental data and model calculation was obtained. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A personal sampler that thermophoretically samples particles between a few nanometers and approximately 300 nm has been designed and first prototypes built. The thermal precipitator (TP) is designed to take samples in the breathing zone of a worker in order to determine the personal exposure to airborne nanomaterials. In the sampler, particles are deposited onto silicon substrates that can be used for consecutive electron microscopic (EM) analysis of the particle size distribution and chemical composition of the sampled particles. Due to very homogeneous size-independent particle deposition on a large portion of the substrate, representative samples can be taken for offline analysis. The experimental evaluation revealed a good general agreement with numerical simulations concerning homogeneity of the deposit and a very high correlation (R^2 = 0.98) of the deposition rate per unit area with number concentrations simultaneously measured with an SMPS for particle sizes between 14 and 305 nm. The samplers' small size of only 45 x 32 × 97 mm3 and low weight of only 140 g make it perfectly suitable as a personal sampler. The power consumption for temperature control and pump is around 1.5 W and can be easily provided by batteries. © 2013 Springer Science+Business Media Dordrecht.

This paper presents breakthrough curves and isotherms of the adsorption of sulfur compounds, carbon dioxide, and water from a carrier gas (methane) on a fixed solid bed at 298 K and 1.3 bar. For the investigation two industrial adsorbents (silica-alumina gel, zeolite 5A) were used. The adsorptives were prepared in trace level concentrations up to 2000 mol-ppm. Common isotherm equations were fitted to the adsorption capacities which were obtained from breakthrough curves by mass balances. Binary systems (one adsorptive in methane) and ternary systems (two adsorptives in methane) are included. Methane is used to duplicate conditions of industrial scale natural gas treatment as far as possible. Though methane is a very weak adsorptive on oxidic adsorbents the reported adsorptive capacities might be slightly lower than pure component loadings accessible from a volumetric or gravimetric method. The adsorption isotherms of the binary systems show distinctly different capacities depending on the polarity of the adsorptive and the structure of the adsorbent. The investigation of the ternary systems reveals significant coadsorption and displacement as well as kinetic effects due to the presence of competing adsorptives. © 2013 American Chemical Society.

Activated carbons are important adsorbents covering a broad range of applications from gas to air purification. In order to improve their mechanical stability and their resistance against oxidation they are infiltrated here with an inert material, SiC or SiO2. For this process the chemical vapor infiltration technique with tetramethylsilane as precursor is used. The process is designed for the infiltration of larger quantities (up to 50 g) which allows further analysis of the materials produced: in comparison to the uncoated activated carbon the novel adsorbent have an increased breaking strength and the BET-surface areas and pore volumes are on high levels. The possibility of using the novel material for solvent adsorption is demonstrated for acetone. © 2013 The Authors.

Liquid phase adsorption is an important process for the removal of trace compounds from liquid matrices. Until today, research on liquid phase adsorption is less substantial than work on other thermal separation processes. The description of relevant mechanisms and interactions is difficult mainly because of lacking experimental data. This paper presents extensive isotherm measurements for the adsorption of organic trace compounds from organic solvents on activated carbons. A systematic variation of molecular structure of adsorptives and solvents enabled the identification of main structural factors dominating adsorption in these systems. The factors are polarity, extension and density of π electrons and sterical complexity. An analysis of the measured isotherms revealed incremental effects of functional groups and structural elements being characteristic for the adsorption capacities on activated carbons. Three consecutive empirical prediction models of adsorption equilibria are developed and compared. The empirical Freundlich equation appeared to be best suited for fitting the experimental data. The models apply an incremental concept permitting the calculation of adsorption isotherms on the basis of the structural increments of solvent and adsorptive molecules. The three models have a different extent of underlying data, a different number of parameters and a different range of application. The experimental data are predicted with satisfying accuracy for many engineering applications. The most sophisticated model has the most extensive range of application and manages on the smallest number of parameters. © 2012 Springer Science+Business Media, LLC.

Dry organic solvents are important for many industrial sectors. Adsorptive water removal is one technique to obtain highly pure solvents. However, in-depth knowledge of the parameters influencing adsorption behavior is still fragmentary. This paper presents a systematic investigation of water adsorption from alcohols (C1 to C6) and acetic acid esters (methyl acetate to n-butyl acetate) of different chain lengths. Zeolites of types 3A and 4A are used as adsorbents. The impact of size exclusion on adsorption properties is analyzed. The water adsorption isotherms on zeolite 3A from solvents with a large critical molecular diameter are similar to the water vapor isotherm as expected from literature data. In case of smaller solvent molecules (methanol, ethanol, 1-propanol) a significantly lower water adsorption capacity is found on zeolite 3A. In case of all solvents on zeolite 4A water adsorption is lower than water vapor adsorption even if the estimated molecular diameter is larger than the reported window aperture of the zeolite cage. It is discussed to what extent water and solvent are capable to coadsorb and compete for adsorption sites. © 2012 American Chemical Society.

Highly pure organic solvents gain more and more importance in optical, electronical, pharmaceutical and chemical industry. In this context the removal of water in the lower ppm- and ppb-range is a major challenge since water is always present, e. g., air humidity, and leads to catalyst poisoning and undesired side reactions. One technique to remove water is by adsorption on zeolites, silica gels or aluminas. Despite single technical solutions already existing, systematic measurements of influencing parameters are still missing. The research project adresses the adsorption of water from different organic solvents. In the following experiments with linear primary alcohols and acetic acid esters are discussed as these solvents are often used in industry in low water content qualities. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Results of investigations on inline solvent analytics by Raman spectroscopy during gas scrubbing of CO2 from power plant flue gases are presented. Superior aim is the optimisation of the gas treating process concerning CO2 capture rate and energy demand. © 2011 Published by Elsevier Ltd.

Membrane contactors are discussed as alternative for mass transfer in chemical absorption processes. Their benefits compared to structured packings were investigated in a pilot plant gas scrubber for CO2 absorption. The results of the tests are presented. © 2011 Published by Elsevier Ltd.

A hydrogen storage tank based on the metal hydride sodium alanate is coupled with a high temperature PEM fuel cell (HT-PEM). The waste heat of the fuel cell is used for desorbing hydrogen from the storage tank that in return feeds the fuel cell. ZBT has developed the HT-PEM fuel cell, Max-Planck-Institut für Kohlenforschung the sodium alanate, and IUTA the hydrogen storage tank. During the experiments of the system the fuel cell was operated by load cycling from 165 up to 240 W. Approximately 60 g of hydrogen were delivered from the tank, which was charged with 2676.8 g of sodium alanate doped with 4 mol.% of TiCl 3. This amount of hydrogen was desorbed in 3 h and generated a cumulated electrical energy of 660 Wh. In the first cycle 81.5 g of hydrogen were supplied during 3.69 h to the HT-PEM fuel cell, which was operated nearly constant at 260 W. In the latter case the cumulated electrical energy was 941 Wh. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultra pure chemicals are most notably used in electronics, optics, pharmaceutics and analytics. For the production of ultra pure liquids adsorptive removal of trace compounds and moisture is the preferred treatment. Adsorption experiments with the model system activated carbon/alkoxyphenol in ketones and esters as solvent are presented. Points of interest are the investigation of adsorption mechanisms as well as the measurement and modelling of adsorption isotherms. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.