The relatively low hydrothermal stability of Al-rich Cu-SSZ-13 catalysts hinders their practical application in ammonia selective catalytic reduction (NH 3 -SCR) reaction. Rare-earth ions were introduced into the Al-rich SSZ-13 zeolite using an organotemplate-free synthesis prior to the exchange of Cu 2+ ions. Among the rare-earth ions tested (Ce, La, Sm, Y, Yb), Y shows significant enhancement of the hydrothermal stability and NH 3 -SCR activities after severe hydrothermal aging at 800 °C for 16 h when compared with Cu-SSZ-13 without Y. Cu-Y-SSZ-13 catalysts with various amounts of Y were prepared, and it is found that with increasing Y content, the low temperature NO conversions can be improved even after hydrothermal aging. SEM-EDX analysis together with two-dimensional multiple quantum magic-angle-spinning nuclear magnetic resonance ( 23 Na MQ MAS NMR) confirms that the Y ions are successfully incorporated into the ion-exchange sites of the SSZ-13 zeolite. Results from 27 Al MAS, 29 Si MAS NMR, temperature-programmed desorption of ammonia (NH 3 -TPD) and quantitative 1 H MAS NMR indicate that Y can stabilize the framework Al and also preserve the Brønsted acid sites in the Al-rich SSZ-13 zeolite. The hydrogen temperature programmed reduction (H 2 -TPR), ultraviolet-visible-near infrared spectroscopy (UV-vis-NIR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of nitric oxide (NO) or NH 3 adsorption demonstrate that introduction of Y ions causes Cu 2+ ions to preferentially occupy the 6-MR, which has high hydrothermal stability. However, too much of Y may lead to activity loss at both low and high temperatures. The optimized Al-rich Cu-Y-SSZ-13 with 2.8 wt% of copper (Cu) and 1.3 wt% of Y displays almost the same deNO x activities as the conventional organotemplated high silica Cu-SSZ-13 catalyst in a wide reaction temperature window of 150-650 °C after severe hydrothermal treatment. Rare-earth ions could be an effective additive for Cu-SSZ-13 catalysts to further improve their hydrothermal stability for practical applications. © 2019 The Royal Society of Chemistry.

Metal-exchanged zeolites with small pore sizes have attracted much attention in recent years due to their application in the selective catalytic reduction (SCR) of NOx in diesel engines. Typically, copper-chabazite (e.g. Cu-SSZ-13) has been gradually used as an SCR catalyst in heavy-duty diesel vehicles over the last decade due to its relatively excellent catalytic performance and stability. However, most SSZ-13 zeolites are still prepared via the traditional hydrothermal process in the presence of organic templates, requiring consecutive solid separation and thermal treatment steps to achieve the final zeolite products. In recent years, several strategies for the environmentally friendly preparation of zeolites have been reported, which are also applicable for the synthesis of zeolites for emission control applications. These concepts include copper-amine templating, organotemplate-free synthesis, and solvent-free synthesis. In this review, we briefly summarize the potential advantages of the environmentally friendly synthesis of zeolites for SCR. © The Royal Society of Chemistry 2019.

The relatively low activity at lower temperatures and high cost of SSZ-13 zeolite from organotemplate synthesis are two of major problems of presently commercialized Cu-SSZ-13 catalysts for NH3-SCR reaction. Cu-exchanged Al-rich SSZ-13 catalysts with Si/Al = 4 from organotemplate-free synthesis have been prepared, and show superior NH3-SCR performance with NO conversions above 85% at wide-temperature window ranging from 150 to 650 °C. Cu-Na-SSZ-13 catalysts with varied amount of residual Na+ were prepared by partial ion-exchange of as-prepared Al-rich Na-SSZ-13, and it's found that Cu-Na-SSZ-13 catalyst with moderate Na+ content can improve both the low-temperature activity and its hydrothermal stability. 27Al and 1H MAS NMR spectra indicate that residual Na+ can stabilize the framework Al in Al-rich SSZ-13 zeolite. UV-Vis-NIR and H2-TPR spectra demonstrate that Na+ co-cations enhance the reducibility of Cu2+, whereas too much amount of Na+ may result in the formation of CuOx during the hydrothermal treatment, and further decrease the hydrothermal stability of Cu-Na-SSZ-13 catalyst. The optimized organotemplate-free Cu-Na-SSZ-13 with 2.7 wt% Cu and 1.7 wt% Na exhibits almost the same NO conversions as the commercial high-silica Cu-SSZ-13 catalyst at 150–550 °C after 750 and 800 °C hydrothermal aging, and shows promising practical applications. © 2017 Elsevier B.V.

SAPO-11 nanosheets with partially filled micropores (N-SAPO-11) and a thickness of 10-20 nm were synthesized using polyhexamethylene biguanide hydrochloride (PHMB) as a mesoporogen and di-n-propylamine (DPA) as a microporous template. After Pt loading (0.5 wt%), the Pt/N-SAPO-11 catalyst exhibits higher selectivity for the isomers and lower selectivity for cracking products than conventional Pt/SAPO-11 catalysts in the hydroisomerization of n-dodecane. © 2017 The Royal Society of Chemistry.

High silica CHA zeolite plays an important role in selective catalytic reduction of NOx with NH3 (NH3-SCR), but its synthesis is not highly efficient due to the use of a relatively high-cost structural directing agent (SDA) N,N,N-trimethyl-adamantammonium hydroxide (TMAdaOH) and relatively long crystallization time under hydrothermal conditions. Herein, we report an efficient and rapid synthesis of a high silica CHA zeolite possessing good crystallinity and uniform crystals (CHA-ST). The method includes interzeolite transformation of high silica FAU zeolite in the absence of water but the presence of zeolite seeds and a bromide form of the SDA. The absence of water in the synthesis significantly improves the zeolite yield by avoiding dissolution of aluminosilicate species in aqueous media, while the addition of zeolite seeds remarkably enhances the crystallization rate under solvent-free conditions. In addition, this route allows the use of a low-cost bromide form of the SDA. Catalytic tests in the NH3-SCR show that copper-exchanged CHA-ST (Cu-CHA-ST) exhibits comparable catalytic properties to those of Cu-SSZ-13 obtained from the conventional hydrothermal route. © 2017 The Royal Society of Chemistry.

Many synthesis parameters can influence zeolite crystallization, which include the molar ratio of reagents, water content, temperature, the selection of extraframework cations (organic or inorganic template) and so on. In this paper, two new materials, BUCT-1 with cuboid morphology and BUCT-2 with plate-like morphology were obtained based on the synthesis conditions of ITQ-17 by adjusting the GeO2/SiO2 ratio, H2O/TO2 ratio and temperature. The influence of the three factors on crystal size, crystallinity and phase selection and transformation was carefully discussed. Therein, phase selection and transformation is determined by their synergistic effects; while the influence on crystal size and crystallinity is different for different materials, which is caused by the differences in their structure, or in other words, the building unit, and chemical composition. In addition, the structure of BUCT-2 has already been solved as the stacking of sti layers, and it was identified as pure germanate molecular sieves. Meanwhile, through the characterization of XRD, ICP-AES, IR and STA, some topological information on BUCT-1, such as unit cell parameters, pore size and connectivity, was predicted and the work to present its final structure is still going on. © The Royal Society of Chemistry.

Pure silica ITQ-7 zeolite of topology ISV synthesized in fluoride media possesses a 3D 12-membered-rings pore system. Originally the structure of ITQ-7 zeolite was solved and refined from a calcined sample in the highest possible space group symmetry P42/mmc. This space group leads to only 5 independent silicon T sites for this structure. However, this high symmetry was not supported by solid state 29Si MAS NMR spectroscopy. In this short communication, we show from a revised 29Si solid state MAS NMR and Rietveld analyses, that lowering of the space group symmetry from P42/mmc to P42 consolidates structure model and experimental data, in particular, the number of non equivalent crystallographic T sites passing from 5 to 16, is in agreement with 29Si solid state NMR spectroscopy. © 2015 Elsevier Inc.

Zeolites synthesized without any organic structure-directing agent (OSDA) have several advantages over conventional zeolites synthesized with OSDAs. Their Al-rich compositions, however, are sometimes not suitable for applications as catalysts. In the present study, post-synthetic modification was performed using an Al-rich Beta zeolite synthesized without any OSDAs (designated as "Beta(OF)") to obtain high-silica Beta zeolites. We have successfully developed a facile post-synthetic method for tuning the Al content of Beta(OF) with the ∗BEA-type structure retained by calcination at >750 °C followed by acid treatment. Solid-state 29Si and 27Al MAS NMR analyses revealed that during calcination, framework Al atoms were isomorphously substituted with Si atoms to form high-silica frameworks and concomitant extra-framework Al species. The stability of the obtained frameworks against acid treatment was evaluated in terms of the framework Al content, finding that the framework with the Si/Al ratio higher than 12 is well stabilized enough for acid treatment. Thus, dealuminated Beta(OF) zeolites with high-silica compositions were found to be effective catalysts for the methanol-to-olefin (MTO) reaction; particularly, the Beta zeolite with the Si/Al ratio of 112 maintained the conversion of methanol over 90% with selectivity to C2-C4 olefins over 70% even at 40 hours on stream at WHSV = 3.2 h-1. © The Royal Society of Chemistry 2016.

Two types of Beta zeolites, one from organotemplate-free synthesis with a Si/Al ratio of 9 and the other from a commercial one with a Si/Al ratio of 19, were employed here to dope Fe for NH3-SCR of NOx. Fe-Beta (Si/Al = 9) exhibits much higher activity than Fe-Beta (Si/Al = 19), especially at low-temperature regions (< 250 °C). In addition, it also exhibits better hydrothermal stability as compared with Fe-Beta (Si/Al = 19), which demonstrates that it is a promising SCR catalyst with good activity as well as hydrothermal stability. The correlation between the quantitative calculation of the content of isolated Fe3+ in Beta zeolites and the NO conversion rate at 150 °C shows a linear relationship, suggesting that the isolated Fe3+ species affect the SCR activity directly. The higher activity of the Fe-Beta-9 catalyst is supposed to be related not only to the isolated Fe3+ but also to the acidity. Furthermore, the template-free synthesized Beta zeolite shows less dealumination during hydrothermal aging and therefore better hydrothermal stability during the SCR reaction. © 2016 The Royal Society of Chemistry.

Copper and iron bimetal modified Al-rich Beta zeolites from template-free synthesis were prepared for selective catalytic reduction (SCR) of NOx with NH3 in exhaust gas streams. Comparing to the Cu-based and Fe-based mono-component Beta catalysts, Cu(3.0)-Fe(1.3)-Beta bi-component catalyst shows better low-temperature activity and wider reaction-temperature window. Over 80% of NO conversion can be achieved at the temperature region of 125–500 °C. Due to the synergistic effect of copper and iron evidenced by XRD, UV–Vis–NIR, EPR and XPS measurements, the dispersion state of active components as well as the ratio of Cu2+/Cu+ and Fe3+/Fe2+ were improved over Cu(3.0)-Fe(1.3)-Beta. Isolated Cu2+ and Fe3+ ions which located at the exchange sites could be the active species at the low-temperature region, while FeOx cluster species may be more important to the high-temperature activity. During the test of sulfur resistance, Fe-containing samples including Cu(3.0)-Fe(1.3)-Beta and Fe(2.7)-Beta-4 present better performance compared to Cu(4.1)-Beta-4. Deactivation of Cu-based catalyst is attributed to the easier deposition of sulfates over the surface according to the results of TGA coupled with TPD experiments. © 2016 Elsevier Inc.

Interlayer expansion using silylating agents to connect layer silicates to 3D framework structures has shown to be a versatile synthesis route to new crystalline, microporous frameworks. We demonstrate here that also Me cations can be introduced on the linker sites applying the same synthesis procedure. An acidic aqueous Fe-chloride solution was used in a hydrothermal reaction to convert the layered hydrous silicate precursor RUB-36 into an interlayer expanded zeolite, containing Fe at the linker sites, Fe-IEZ-RUB-36, Si19.14Fe0.86O38(OH)4. Structure analysis from powder X-ray data using the Rietveld technique confirmed that the porous framework is stable upon calcination and contains Fe on T-sites at the linker position. SEM-EDX analysis is in agreement with the analysis of the electron density maps showing that almost every other linker T-position is occupied by Fe-ions. The material crystallizes in the monoclinic space group Pm with a = 12.200(9) Å, b = 13.981(8) Å, c = 7.369(2) Å, and β = 106.9(1)°. Applying a similar synthesis procedure, the Sn-analog, Sn-IEZ-RUB-36, Si38.6Sn1.4O76(OH)8, has been obtained and structurally characterized. Despite its limited crystallinity, Rietveld analysis of the PXRD data set confirmed the materials framework topology and chemical composition (a = 23.856(14) Å, b = 14.103(7) Å, c = 7.412(7) Å, in SG Pnm21). We conclude, that the synthesis procedure is flexible and, meanwhile, has been extended to other metal cations such as Ti, Zn, Eu and Al leading to microporous materials with potentially active metal cations on well defined sites of the silicate framework. © 2015 Published by Elsevier Inc.

A new silicogermanate (PKU-20) was hydrothermally synthesized using triethylisopropylammonium cation as the structure directing agent in the presence of fluoride. Its structure was determined from a combination of synchrotron single crystal X-ray diffraction and powder X-ray diffraction data. PKU-20 crystallizes in the monoclinic space group C2/m, with the lattice parameters of a = 18.5901(6) Å, b = 13.9118 (4) Å, c = 22.2614 (7) Å and β = 100.1514 (12)°. The framework of PKU-20 is constructed from an alternate stacking of sti and asv layers. The sti layer is exactly the same as that in the STI framework,while the asv layer is a new layer sliced off from the ASV framework parallel to the (112) plane. The take-out scheme of the layer is discussed on the basis of a composite building unit "D4R-lau-D4R". PKU-20 possesses a two-dimensional channel system, where the 10-ring channels parallel to the [010] direction are intercrossed by 12-ring pockets along the [101] direction. © 2016 Elsevier Inc. All rights reserved.

ITQ-8 is a new hydrous layer silicate (HLS) with a chemical composition of [C4H8(C7H13N)2]8 [Si64O128(OH)16]·48H2O per unit cell. The synthesis of ITQ-8 was first described in 2002 by Díaz-Cabañas et al., the structure of this material, however, remained unsolved at that time. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and FTIR spectroscopy confirmed that ITQ-8 is a layer silicate. The XRD powder pattern was indexed in the monoclinic system with lattice parameters of a0 = 35.5168(5) Å, b0 = 13.3989(2) Å, c0 = 16.0351(2) Å, β = 106.74(2)°. The crystal structure was solved by simulated annealing. Rietveld refinement of the structure in space group C2/c converged to residual values of RBragg = 0.023, RF = 0.022 and chi2 = 2.3 confirming the structure model. The structure of ITQ-8 contains silicate layers with a topology that resembles a (11-1) section of the framework of zeolite levyne. So far, this layer topology is unique among layer silicates. The layer can be regarded as made up of 4-, 6-, double-six and 8-rings which are interconnected to form cup-like "half-cages". Unlike other HLSs, which possess impermeable silicate layers, ITQ-8 contains 8-rings pores with a free diameter of 3.5 Å × 3.4 Å and can be regarded as a "small-pore layer silicate". In the crystal structure, the organic cations, 1,4-diquiniclidiniumbutane, used as structure directing agents during synthesis are intercalated between the silicate layers. Clusters (bands) of water molecules which are hydrogen bonded to each other and to the terminal Si-OH/Si-O- groups are located between the organic cations and interconnect the silicate layers. ITQ-8 is a very interesting material as precursor for the synthesis of microporous framework silicates by topotactic condensation or interlayer expansion reactions leading to 3D micro-pore systems which may be useful in applications as e.g. catalysts, catalyst supports and adsorbents of for separation. © The Royal Society of Chemistry 2016.

This paper reports on the successful crystallization of monodisperse, highly crystalline, nanosized zeolite Silicalite-1 crystals in fluoride media by using an active silica gel as silica source and tetrapropylammonium fluoride as structure directing agent. The synthesis procedure is hydrothermal dynamic crystallization. The silica/water ratio and synthesis temperature were reduced to optimize the number of crystal nuclei and control the rate of crystallization for obtaining nanosized zeolite crystals. Meanwhile, F- ions were used to partly replace OH- ions in the synthesis system to obtain zeolite products with high crystallinity. Analytical results of XRD-, SEM-, Dynamic Light Scanning- (DLS) IR-, Simultaneous Thermal Analysis- (STA) and N2 adsorption and desorption experiments show that the average particle size of zeolite Silicalite-1 product is about 45 nm and shows high crystallinity. The F- containing Silicalite-1 zeolite sample was compared with an industrial ZSM-5 zeolite sample and it shows obvious advantages in both reduced particle size and enhanced crystallinity. © 2015 Elsevier Inc. All rights reserved.

The layered silicate COK-5 has been used for an interlayer expansion reaction with dichlorodimethylsilane (DCDMS) at 180 °C to interconnect neighboring layers, yielding a new and crystalline microporous framework. The samples containing the methyl functional groups in the as-made form and having OH groups in the calcined form were designed as COE-5 and calcined COE-5. These samples were characterized with X-ray diffraction (XRD), N<inf>2</inf> sorption isotherms, inductively coupled plasma optical emission spectrometry (ICP-OES), infrared spectroscopy (IR), high-resolution transmission electron micrograph (HRTEM), thermogravimetry-differential thermal analysis (TG-DTA), and 29Si and 13C solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR), as well as the contact angle techniques. XRD patterns and HRTEM images suggest that the sample interlayer spacing has been expanded by nearly 0.5 Å. The N<inf>2</inf> sorption isotherms of the materials show the BET surface areas are 165 m2/g for COE-5 and 340 m2/g for calcined COE-5. 29Si and 13C MAS NMR as well as IR spectroscopy confirm the insertion of the linker group -Si(CH<inf>3</inf>)<inf>2</inf>- connecting neighboring layers. Interestingly, calcined COE-5 shows enhanced catalytic performance in the acetalisation of glycerol with acetone to produce solketal, compared with COK-5. © 2015 Elsevier Inc.

Silica-supported catalysts for the conversion of ethanol to 1,3-butadiene were investigated. The combination of Hf(IV) and Zn(II) resulted in a stable, active, and selective catalyst in which the Zn(II) effectively suppressed the dehydration activity of Hf(IV); the catalyst preparation method plays a crucial role. Using the crystalline Zn-silicate hemimorphite as an alternative Zn(II) source proved to be even more successful in suppressing ethanol dehydration. © 2015 American Chemical Society.

Synthesis experiments in the simple system TMAOH/SiO2/H2O led at 160°C to the crystallization of two new tetramethylammonium (TMA) silicates, RUB-20 and RUB-22. The common feature of the two silicates is the presence of ordered defects within the silicate network, necessary to compensate the charge of the occluded TMA cation. RUB-20, [(CH3)4N]1.7[Si18O35(OH)4], is a layered material with a0 =10.493(2) A, b0=13.988(2) A, c0=7.411(1) A, β=97.80(2)° and space group P21/m. It consists of ferrierite type (fer) silicate layers which possess a significant amount of defects. These defects apply only to one particular Si-O-Si bridge which is hydrolyzed to about 50% to form two additional Si-OH/Si-O- groups which point to the interlayer region of the structure. These silanol groups together with the regular terminal silanol groups of neighbouring fer layers form a system of hydrogen bonds which binds the layers together. In addition, weak ionic bonds exist between the negatively charged silicate layers and the intercalated TMA cations. RUB-22 is a zeolite-like silicate possessing a microporous framework with doublecages, housing the TMA cations. The Rietveld structure analysis revealed a pseudo monoclinic unit cell with a0 =13.6626(2) A, b0=13.2400(2) A, c0 =12.3009(2) A, α=90.003(3)°, β=112.700(1)°, γ=90.005(3) and space group C1. RUB-22, [(CH3)4N]4[Si32O60(OH)12], possesses an interrupted silica framework of the same topology as RUB-10, [(CH3)4N]4[Si32B4O72] (zeolite framework type RUT), however, with the difference that defects replace the [BO4]- tetrahedra. The defects can be regarded as "hydroxyl nests" surrounding a vacancy □(OH-Si)3(-O-Si) instead of B(-O-Si)4 groups. Heating the as made materials at 600°C led in the case of RUB-20 to a highly disordered zeolite of the CDO type and in the case of RUB-22 to a distorted and defective RUT-type material.

The interpenetrating 3-dimensional channel system of silica MCM-48 has been selected for the deposition of ZnO nanoparticles. The post-synthetic organometallic route was employed to load the mesoporous silica with ZnO-precursor molecule. Calcination of the composite transformed the organometallic sorbate to the corresponding metal oxide. X-ray powder diffraction, N2-Adsorption and TEM measurement have supported the efficient loading and growth of ZnO particles in the channels of mesoporous silica matrix. EXAFS analysis (ZnK-edges) also complemented the metal uptake. Presence of nano-dispersed and nanosized ZnO particles confined by the mesoporous pore system was established by TEM and EXAFS analysis. © 2015 VBRI Press.

The layered zeolite precursor RUB-36, consisting of ferrierite-type layers, can be transformed into a three-dimensional framework through various methods such as topotactic condensation into the CDO topology, or interlayer expansion either in the presence or absence of a silylating agent. However, the plate-like morphology of the micrometer sized crystals hampers the accessibility of the 2D micropore system, in which the channels run parallel to the plates. With the aim of introducing mesoporosity, alkaline treatments were performed on different RUB-36 derived expanded materials, and on RUB-36 itself. The effect on the physicochemical properties was examined using N2 physisorption, powder X-ray diffraction, scanning electron microscopy and 27Al MAS NMR whereas the influence on the catalytic activity was evaluated using esterification and alkylation reactions. After calcination, the purely inorganic, interlayer expanded material could be transformed into a mesopore containing FER-type material by selective removal of the interlayer T atom followed by the recombination of the layers. In the precalcination state, organic moieties, originating from the silylating agent or from the organic structure directing agent (OSDA), increase the hydrophobicity of the interlayer expanded structure and its stability against the alkaline treatment. In RUB-36, the high OSDA content limited the amount of mesopore formation through alkaline treatment. However, using the appropriate conditions, the subsequent interlayer expansion of alkaline treated RUB-36 also resulted in a mesopore containing interlayer expanded structure. © 2014 American Chemical Society.

Density functional theory (DFT) has been performed to characterize the structural stability and Lewis acidic properties of the T-COE-4 zeolites, in which the linked site between the layers is isomorphously substituted by the tetravalent Ti-, Sn-, or Zr- heteroatom. The effects of substitution energy and equilibrium geometry parameters on the stability of T-COE-4 are investigated. The computed Fukui function values and the adsorption of ammonia, pyridine, water and trimethylphosphine oxide molecules have been employed to predict the Lewis acid strength of the T-COE-4 zeolites. It is found that the smaller the O1-T-O2 bond angle is, the more difficult is to form the regular tetrahedral unit. The substitution energies at the linker position increase in the following sequence: Ti-COE-4 < Sn-COE-4 < Zr-COE-4. The incorporation of Ti-, Sn-, or Zr-heteroatom enhances the Lewis acidity of COE-4 zeolite. It is predicted that the Lewis acid strength increases in the order of Ti-COE-4 < Zr-COE-4 & Sn-COE-4 by the adsorption of different base molecules. Six O-T-O bond angles are divided into different extent to form the analogous trigonal bipyramid structures in the optimized ligand adsorbed complexes. These findings could be beneficial for the structural design and catalytic function modification of the interlayer-expanded zeolites. © 2015 Elsevier Inc. All rights reserved.

Interlayer expanded zeolites are derived from layered zeolite precursors by inserting a tetrahedrally coordinated atom (T-atom) in between the precursor layers. To achieve this expansion, a Si source like dichlorodimethylsilane or diethoxydimethylsilane is typically used. In the interlayer expansion of the layered zeolite precursor RUB-36, an Fe salt instead of a silylating agent was used to fill up the linking sites in between the layers. The obtained material showed a shift of the first XRD reflection similar to that of RUB-36 interlayer expanded with dichlorodimethylsilane, indicating an increase in interlayer distance. Diffuse reflectance UV-vis spectra and EPR characterization proved the incorporation of isolated Fe sites. Using FTIR spectroscopy with pyridine and acetonitrile as probe molecules, it was found that the incorporation of Fe results in an increase in Lewis acidity. The material was successfully used as a catalyst in the acylation of anisole with acetic anhydride and in the alkylation of toluene with benzyl chloride. The Fe incorporation proved to be remarkably stable. In spite of the HCl production during the alkylation reaction, no leaching was observed and the catalyst could be reused after regeneration. This journal is © the Partner Organisations 2014.

Layered solids often form thin plate-like crystals that are too small to be studied by single-crystal X-ray diffraction. Although powder X-ray diffraction (PXRD) is the conventional method for studying such solids, it has limitations because of peak broadening and peak overlapping. We have recently developed a software-based rotation electron diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Here we demonstrate the ab initio structure determination of two interlayer expanded zeolites, the microporous silicates COE-3 and COE-4 (COE-n stands for International Network of Centers of Excellence-n), from submicron-sized crystals by the RED method. COE-3 and COE-4 are built of ferrierite-type layers pillared by (-O-Si(CH 3)2-O-) and (-O-Si(OH)2-O-) linker groups, respectively. The structures contain 2D intersecting 10-ring channels running parallel to the ferrierite layers. Because both COE-3 and COE-4 are electron-beam sensitive, a combination of RED datasets from 2 to 3 different crystals was needed for the structure solution and subsequent structure refinement. The structures were further refined by Rietveld refinement against the PXRD data. The structure models obtained from RED and PXRD were compared. This journal is © the Partner Organisations 2014.

A series of Cu-exchanged Al-rich Beta zeolites from organotemplate-free synthesis was prepared and investigated for selective catalytic reduction (SCR) of NO<inf>x</inf> with NH<inf>3</inf> in exhaust gas streams. In comparison to conventional Cu-Beta zeolite with Si/Al ratio of 19, Cu-Beta zeolite with Si/Al ratio of 4 is a superior low-temperature NH<inf>3</inf>-SCR catalyst. Very high NO conversion (>95%) can be achieved at temperatures as low as 150 to ∼400 °C. XRD, UV-Vis-NIR and NH<inf>3</inf>-TPD measurements show that more isolated Cu2+ ions are present at the exchange sites of Al-rich Beta zeolite. The combination of CO-FTIR and H<inf>2</inf>-TPR analysis demonstrates that Cu2+ ions could be reduced more readily on the Al-rich Beta than on the conventional Beta probably due to the proximity of the isolated Cu2+ ions. These can be correlated to the enhancement of NO conversion at lower temperatures over Cu-exchanged Al-rich Beta zeolite. © 2014 Elsevier Inc.

The petrographic analysis and crystallographic analysis of concretionary carbonate cements ("coal balls") from Carboniferous paralic swamp deposits reveal the presence of (length fast) radiaxial fibrous dolomite (RFD), a fabric not previously reported from the Phanerozoic. This finding is of significance as earlier reports of Phanerozoic radiaxial fibrous carbonates are exclusively of calcite mineralogy. Dolomite concretions described here formed beneath marine transgressive intervals within palustrine coal seams. This is of significance as seawater was arguably the main source of Mg2+ ions for dolomite formation. Here, data from optical microscopy, cathodoluminescence, electron backscattered diffraction, X-ray diffraction and geochemical analyses are presented to characterize three paragenetic dolomite phases and one calcite phase in these concretions. The main focus is on the earliest diagenetic, non-stoichiometric (degree of order: 0.41-0.46) phase I, characterized by botryoidal dolomite constructed of fibres up to 110μm wide with a systematic undulatory extinction and converging crystal axes. Petrographic and crystallographic evidence clearly qualifies phase I dolomite as radiaxial fibrous. Conversely, fascicular optical fabrics were not found. Carbon-isotope ratios (δ13C) are depleted (between -11.8 and -22.1‰) as expected for carbonate precipitation from marine pore-fluids in organic-matter-rich, paralic sediment. Oxygen isotope (δ18O) ratios range between -1.3 and -6.0‰. The earliest diagenetic nature of these cements is documented by the presence of ubiquitous, non-compacted fossil plant remains encased in phase I dolomite as well as by the complex zoned luminescence patterns in the crystals and is supported by crystallographic and thermodynamic considerations. It is argued that organic matter, and specifically carboxyl groups, reduced thermodynamic barriers for dolomite formation and facilitated Mg/CaCO3 precipitation. The data shown here reveal a hitherto unknown level of complexity with respect to radiaxial fibrous carbonates and are of importance for those concerned with dolomite and carbonate petrography in general. © 2014 Elsevier B.V.

COE-4 zeolites possess a unique two-dimensional ten-ring pore structure with the Si(OH)2 hydroxyl groups attached to the linker position between the ferrierite-type layers, which has been demonstrated through the interlayer-expansion approach in our previous work (H. Gies et al. Chem. Mater. 2012, 24, 1536). Herein, density functional theory is used to study the framework stability and Brønsted acidity of the zeolite T-COE-4, in which the tetravalent Si is isomorphously substituted by a trivalent Fe, B, Ga, or Al heteroatom at the linker position. The influences of substitution energy and equilibrium geometry parameters on the stability of T-COE-4 are investigated in detail. The relative acid strength of the linker position is revealed by the proton affinity, charge analysis, and NH3 adsorption. It is found that the range of the 〈T-O-Si〉 angles is widened to maintain the stability of isomorphously substituted T-COE-4 zeolites. The smaller the 〈O1-T-O2〉 bond angle is, the more difficult is to form the regular tetrahedral unit. Thus, the substitution energies at the linker positions increase in the following sequence: Al-COE-4 < Ga-COE-4 < Fe-COE-4 < B-COE-4. The adsorption of NH3 as a probe molecule indicates that the acidity can affect the hydrogen-bonding interaction between (N-H⋯O2) and (N⋯H-O2). The relative Brønsted-acid strength of the interlayer-expanded T-COE-4 zeolite decreases in the order of Al-COE-4 &gt; Ga-COE-4 &gt; Fe-COE-4 &gt; B-COE-4. These findings may be helpful for the structural design and functional modification of interlayer-expanded zeolites. Calculating exchange: Density functional theory is employed to survey the differences in the structure, stability, and Brønsted-acidic properties at the linker-T active site, in which the tetrahedral silicon is isomorphously substituted by a Fe, B, Ga, or Al atom in the interlayer-expanded zeolite, COE-4. Substitution energy and geometric parameters of T-COE-4 zeolites are discussed in detail, and their relative acid strengths are predicted. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An open-framework fluorinated aluminium phosphite-phosphate, H 3.2Mn3.4[C6N2H11] 2{Al12(HPO3)15.0(HPO 4)3.0F12}·14H2O (DNL-2), was ionothermally synthesized by employing the in situ released Mn2+ cations as structure-directing agent. © 2014 The Royal Society of Chemistry.

Interlayer expansion of layered zeolite precursors is achieved via the insertion of an additional T-atom in between the layers, typically by means of a silylating agent as source of the T-atom. (3-Mercaptopropyl) methyldimethoxysilane was used as Si-source in the interlayer expansion of the layered zeolite precursors RUB-36 and RUB-39. The structure expansion was confirmed with PXRD. The incorporation of the silylating agent was followed with 29Si MAS NMR, 13C CP MAS NMR and thermogravimetric analysis. The incorporated thiol groups were oxidized with H2O 2 to obtain sulfonic acid groups in between the layers. 13C CP MAS NMR was used to characterize the organic species and monitor the conversion of thiol to propylsulfonic groups. The shape-selective properties of the obtained materials were investigated in acid-catalyzed tetrahydropyranylation reactions. © 2014 Elsevier B.V.

Five different hydrous layer silicates (HLSs) containing fer layers (ferrierite-type layers) were obtained by hydrothermal syntheses from mixtures of silicic acid, water and tetraalkylammonium/tetraalkylphosphonium hydroxides. The organic cations had been added as structure directing agents (SDA). A characteristic feature of the structures is the presence of strong to medium strong hydrogen bonds between the terminal silanol/siloxy groups of neighbouring layers. The five-layered silicates differ chemically only with respect to the organic cations. Structurally, they differ with respect to the arrangement of the fer layers relative to each other, which is distinct for every SDA-fer-layer system. RUB-20 (containing tetramethylammonium) and RUB-40 (tetramethylphosphonium) are monoclinic with stacking sequence AAA and shift vectors between successive layers 1a0 + 0b0 + 0.19c 0 and 1a0 + 0b0 + 0.24c0, respectively. RUB-36 (diethyldimethylammonium), RUB-38 (methyltriethylammonium) and RUB-48 (trimethylisopropylammonium) are orthorhombic with stacking sequence ABAB and shift vectors 0.5a0 + 0b0 ± 0.36c 0, 0.5a0 + 0b0 + 0.5c0 and 0.5a 0 + 0b0 ± 0.39c0, respectively. Unprecedented among the HLSs, two monoclinic materials are made up of fer layers which possess a significant amount of ordered defects within the layer. The ordered defects involve one particular Si-O-Si bridge which is, to a fraction of ca. 50%, hydrolyzed to form nests of two Si-OH groups. When heated to 500-600 °C in air, the HLSs condense to form framework silicates. Although all layered precursors were moderately to well ordered, the resulting framework structures were of quite different crystallinity. The orthorhombic materials RUB-36, -38 and -48, general formula SDA4Si36O 72(OH)4, which possess very strong hydrogen bonds (d[O⋯O] ≈ 2.4 Å), transform into a fairly or well ordered CDO-type silica zeolite RUB-37. The monoclinic materials RUB-20 and -40, general formula SDA2Si18O36(OH)2OH, possessing medium strong hydrogen bonds (d[O⋯O] ≈ 2.65 Å) are transformed into poorly ordered framework silicates. Some rules of thumb can be established concerning the successful zeolite synthesis via a topotactic condensation of layered precursors. Favourably, the precursor (i) possesses already a well ordered structure without defects, (ii) contains strong inter-layer hydrogen bonds and does not contain strong intra-layer hydrogen bonds and (iii) contains a suitable cation. The nature of the organic cation (size, geometry, flexibility, thermal stability) plays a key role in the formation of a microporous tectosilicate with well ordered structure. RUB-36 which meets these criteria yields a well ordered condensation product (RUB-37). This journal is © the Partner Organisations 2014.

Structural analysis and catalytic testing revealed that zeolite Beta from template-free synthesis introduces new possibilities in catalysis, as a result of its unprecedentedly high density of active sites with exceptional stability and distinctively ordered nature. Highly active and selective catalysts were obtained either by using it in the Al-rich form (e.g. alkylation) or after post-synthesis treatments (e.g. acylation). Such versatility made possible by this novel synthesis route constitutes a new toolbox for catalysis. © 2013 The Royal Society of Chemistry.

Magnetite (Fe3O4) is an important biomineral, e.g., used by magnetotactic bacteria. The connection between the inorganic magnetite-(111)-surface and the organic parts of the bacteria is the magnetosome membrane. The membrane is built by different magnetosome membrane proteins (MMPs), which are dominated by the four amino acids glycine (Gly), aspartic acid (Asp), leucine (Leu) and glutamic acid (Glu). Force field simulations of the interaction of the magnetite-(111)-surface and the main amino acid compounds offer the possibility to investigate if and how the membrane proteins could interact with the mineral surface thus providing an atomistic view on the respective binding sites. In a force field simulation the four amino acids were docked on the Fe-terminated magnetite-(111)-surface. The results show that it is energetically favorable for the amino acids to adsorb on the surface with Fe-O-distances between 2.6 Å and 4.1 Å. The involved O-atoms belong to the carboxyl-group (Asp and Glu) or to the carboxylate-group (Gly, Leu and Glu). Electrostatic interactions dominate the physisorption of the amino acids. During the simulations, according to the frequency of the best results, the global minimum for the docking interaction could be attained for all amino acids analyzed. © 2012 Springer-Verlag Berlin Heidelberg.

Beta zeolite obtained from seeded synthesis without the use of organic structure directing agents (OSDAs) has been used as a catalyst in different types of reactions. The large number of strong acid sites resulted in a high activity for the alkylation of benzene with ethene and a high cracking activity in the hydroconversion of n-decane. However, the high framework polarity resulted in fast deactivation in the acylation of aromatic ethers. Dealumination treatments resulted in improved stability in alkylation reactions with the more reactive olefins like propene. In acylation reactions, the activity was significantly increased, and in hydroconversion, a better balance between the hydrogenation/dehydrogenation and the acid sites was obtained. © 2013 Elsevier Inc. All rights reserved.

Experimental water intrusion-extrusion isotherms were recorded at room temperature on pure silica ISV-type zeolite (ITQ-7 zeosil) possessing a 3D channel system. The water intrusion is obtained by applying a high hydraulic pressure corresponding to the intrusion step. When the pressure is released, the water extrusion occurs but at a lower pressure to that of the intrusion one. The ITQ-7 zeosil-water system behaves like a shock-absorber, but the phenomenon is nonreproducible. Several characterizations have been realized before and after water intrusion-extrusion experiments in order to reveal the presence or the absence of defects after such experiments. Structural modifications at the long-range order can be observed by XRD analysis after intrusion. At the short-range order, solid-state NMR spectroscopy shows evidence of the presence of Q2 ((HO-)2Si(-OSi)2) and Q3 ((HO-Si(-OSi)3) or (Si(-OSi)3O-)) groups revealing the breaking of some siloxane bridges after the intrusion step. The amount of defects increases (< 2% before and 15% after intrusion step). However, after a regeneration step (calcination of the intruded-extruded sample), the ITQ-7 zeosil-water system displays again a shock-absorber behavior with a similar intrusion pressure. © 2013 American Chemical Society.

Layered RUB-36 and PREFER (lamellar precursor of ferrierite) are the precursors of CDO and FER-type zeolites, respectively. Both are composed of the same ferrierite (FER) layer building blocks. Topotactic conversion from RUB-36 to pure silica zeolite ZSM-35 has been demonstrated in the presence of a surfactant cetyltrimethylammonium hydroxide (CTAOH). The transformation mechanism of this process was revealed, for the first time, by the detailed investigations of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis, and one-and two-dimensional (2-D) solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) as well as theoretical simulations. During swelling at room temperature, cetyltrimethylammonium cations (CTA+) replacing the original template were intercalated into FER layers to expand the interlayer distance remarkably and consequently to destroy the strong hydrogen-bonding interactions between the layers. 2-D 1H-29Si heteronuclear correlation (HETCOR) NMR indicates that the surfactant polar heads approximate the FER layers in swollen RUB-36. After deswelling, only a small amount of CTA+ cations with long tails lay in the void space between the FER layers. The Monte Carlo simulations on the deswollen RUB-36 further elucidate the occlusion of CTA+ cations in the pre-10 member ring of the layered ferrierite precursor, which may act as the structure-directing agent for the formation of FER-structured zeolite. The FER layer reassembly from the alteration of CTA+ conformation at the interlayers is of key importance to the topotactic transformation of RUB-36 to FER-type zeolite by the dehydration-condensation reaction. This may open up more applications in the lamellar zeolite system by the layer restacking approach. © 2013 American Chemical Society.

An overview of work with model systems designed to study metal-support interactions in heterogeneous catalysts is given. In these models, metal and support are both miniaturized by introduction as guests into a mesoporous host. The use of such models is demonstrated with Au-TiO2 clusters encaged in MCM-48, and Cu-ZnO clusters encapsulated in siliceous mesopore systems and in carbon nanotubes. The models promise a better opportunity to track changes in the support component during catalyst activation and catalysis, including the action of poisons that may at first be trapped on the support surface. Challenges to be met are the stabilization of the mesoporous matrix during synthesis and catalysis, possible reactivity of the matrix surface towards any of the catalyst components, as well as clustering and segregation of the latter from the matrix. The challenges were encountered as pore damage during preparation of Au-TiO2/MCM-48 catalysts, as deactivating interactions of siliceous walls with zinc ions during deposition of zinc species from aqueous media, and as clustering of the Cu component during calcination and reduction. Among the conclusions drawn from the studies are the irrelevance of order at the Au-TiO2 interface (and, hence, of epitaxy and of crystal strain in gold) for high activity of Au/TiO2 catalysts in CO oxidation. In the models for Cu-ZnO methanol synthesis catalysts, two different types of Cu-Zn interaction could be observed: a direct contact between Zn2+ and Cu(0) under strong reducing conditions, and the formation of alloy nanoparticles (nano-brass). A discussion of the relevance of these interactions for the methanol synthesis reaction is given. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Beta zeolite as efficient catalyst has been widely used in industrial processes, and its synthesis is normally performed in the presence of tetraethylammonium hydroxide as organic template. Recent works show successful organotemplate-free and seed-directed synthesis of Beta zeolite (Beta-SDS) in the presence of Beta seeds at 140 C, providing a novel route for synthesizing low-cost zeolite catalysts. Notably, in the case for synthesizing Beta-SDS at 140 C (Beta-SDS140), the use of seeds is still very high (8-10% in silica source) and impurity of MOR zeolite easily appears due to the fast crystallization rate. We demonstrate here a rational synthesis of Beta-SDS at 120 C (Beta-SDS120) with pure BEA structure and improved zeolite quality in the presence of a very small amount of Beta seeds (as low as 1.4%) by decreasing zeolite crystallization rate. X-ray diffraction patterns show that calcination at 550 C for 4 h results in the loss of crystallinity at 8.0% and 15.8% for Beta-SDS120 and Beta-SDS140, respectively, suggesting that Beta-SDS120 has higher thermal stability than Beta-SDS140. N2 adsorption isotherms show that Beta-SDS120 has much higher surface area (655 m2/g) and micropore volume (0.25 cm3/g) than Beta-SDS140 (450 m 2/g, 0.18 cm3/g). These phenomena are reasonably assigned to that Beta-SDS120 samples have much less framework defects such as terminal Si-OH groups than Beta-SDS140. The Beta-SDS120 samples with good crystallinity, high thermal stability, large surface area and pore volume offer a good opportunity for their industrial applications as efficient and low-cost catalytic and adsorptive materials.© 2013 Elsevier Inc. All rights reserved.

For the first time, the co-templating ionothermal methodology was used in the preparation of layered aluminophosphate materials. With the addition of either 1,2-ethylenediamine or 1,6-hexanediamine to the ionic liquid 1-ethyl-3-methyl imidazolium chloride, two new 2D layered aluminophosphates RUB-A1 [Al 3P 4O 16][NH 3CH 2CH 2NH 3] 0.5[C 6N 2H 11] 2 and RUB-A2 [Al 3P 4O 16][NH 3(CH 2) 6NH 3][NH 3(CH 2) 6NH 2] 0.5[C 6N 2H 11] 0.5[H 2O] have been synthesized ionothermally by co-templating. The structure of RUB-A1 has been determined from single-crystal X-ray diffraction data using direct methods, while the structure of RUB-A2 has been solved ab initio from powder X-ray diffraction data with limited resolution using direct-space methods. Both of these two compounds have a 2D layered structure consisting of macroanionic sheets of composition [Al 3P 4O 16] 3- stacked in an AAAA sequence. The inorganic layers are built up from alternatively vertex-sharing [AlO 4]- and [PO 3(O)]-tetrahedral units forming a 4.6.8 and a 4.6.12 network for RUB-A1 and RUB-A2, respectively. The layer topology of RUB-A1 is closely related to the previously known 4.6.8-layer topology but with a different sequence of phosphoryl group orientation. Combining the results of structure analysis with the NMR, chemical analysis and TG-DTA experiments, we show that both the ionic liquid cation and the protonated diamines are located in the interlayer space and together direct the formation of these two structures. © 2012 The Royal Society of Chemistry.

In the search for new synthesis routes of zeolites, the topotactic condensation of hydrous layer silicates shows promising results in generating novel zeolite materials with distinct framework types which might have new, interesting properties as, e.g., molecular sieves or form-selective catalysts. In order to manipulate and optimise the condensation process detailed knowledge of the crystal structures is essential. The layer silicates considered here are of a special type and can be designated as high-silica hydrous layer silicates, HLSs. The structures consist of a tetrahedral layer of interconnected [SiO 4]-units containing equal numbers of terminal silanol/siloxy groups on either side of the layer and of an inter-layer region where cations of low charge density (predominantly organic cations) and water molecules are located. A topotactic condensation of the layers performed at temperatures of around 500°C with simultaneous expulsion of the inter-layer constituents is able to form fully condensed, uninterrupted framework silicates. The topotactic conversion has so far been described rarely in comparison to the classical hydrothermal synthesis of zeolites. Nevertheless, several hydrous layer silicates with different layer topologies were successfully converted into zeolites of different framework types using this synthesis route: CAS (type material: EU-20, EU-20b), CDO (type material: CDS-1), FER (type material: siliceous ferrierite), MWW (type material: MCM-22), NSI (type material: NU-6(2)), RRO (type material: RUB-41), RWR (type material: RUB-24), SOD (type material: guest-free silica sodalite). Thereby, four new zeolite framework types were obtained which have not been synthesized, so far, by direct hydrothermal synthesis (CDO, NSI, RRO, RWR). This review gives an overview on the hydrous layer silicates being structurally characterized in detail, on the condensation process and on some properties of the resulting zeolite materials. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung.

The hydrous layer silicate RUB-36, (C 6H 16N) 4 [H 4Si 36O 76], has been used for an interlayer expansion reaction with dichlorodimethylsilane to interconnect neighboring ferrierite-type layers to a three-dimensional framework silicate. The linker group (-O-Si(CH 3) 2-O-) still has the two methyl groups in the as-synthesized form (material name COE-3 [Si 20O 38(CH 3) 4] for the silicate framework) rendering hydrophobic properties. The interlayer expanded zeolite, IEZ, is thermally stable and can be calcined at 550 °C to yield a hydrophilic material COE-4 [Si 20O 38(OH) 4]. 29Si solid state MAS NMR experiments confirm the insertion of the linker group and the methyl and hydroxyl substitution in the as-made and calcined form, respectively. The BET surface area is 238 m 2/g for COE-3 and 350 m 2/g for COE-4. COE-3 and COE-4 crystallize in space group Pm with a = 12.2503(3) Å b = 13.9752(2) Å c = 7.3850(1) Å and β = 107.33(1)° and a = 12.16985(4) Å, b = 13.95066(3) Å c = 7.37058(2) Å, and β = 107.30(1)°, respectively. Rietveld crystal structure refinement of the PXRD pattern of COE-3 and COE-4 reveal the expanded, two-dimensional 10-ring pore system including the linker group as homogeneous structural property of the materials. © 2012 American Chemical Society.

Condensation of layered silicate precursors leads to new, all silica zeolite frameworks. In order to introduce catalytic functionality, boron has been substituted into the silicate layer of RUB-39 in a single step synthesis process. Condensation of the silicate layer to the zeolite framework of RUB-41, RRO framework structure type, preserved B as constituent of the material. Analysis of structural details obtained from Rietveld analysis of powder diffraction data, 11B and 29Si NMR experiments of the as synthesized precursor as well as of the zeolite condensation product, and crystal chemical reasoning indicates segregation of B on one specific T-site. This T-site is buried in the silicate anionic layer of the precursor shielding the additional negative charge introduced by the trivalent T-atom. © 2011 Elsevier Inc. All rights reserved.

A ferrierite-type layered aluminosilicate, Al-RUB-36, was prepared for the first time and its interlayer expansion resulted in new zeolite catalysts denoted Al-COE-3 and Al-COE-4. Decane hydroconversion tests demonstrated the highly active and shape-selective nature of the new Al-COE-4 catalyst with an unprecedented isomerization yield, highlighting the potential of this material as a hydroisomerization catalyst. This is the first report on achieving shape-selectivity via interlayer expansion. © The Royal Society of Chemistry 2012.

Ordered mesoporous materials (OMMs) of 1-dimensional hexagonal and 3-dimensional cubic symmetry of the pore systems were synthesized via well-established soft templating routes starting from precursor solutions of MFI-type zeolites (Silicalite-1, TS-1). The products were characterized by XRD, nitrogen and argon physisorption, DTG/DTA, IR, UV-vis spectroscopy, XANES, TEM, 119Xe NMR, and determination of the pair distribution function (PDF) in order to elucidate their structure, in particular to prove the presence of microporosity in arrays smaller than the coherence lengths of XRD, i.e. in the pore walls. The mesoporosity of the OMMs was well supported by physisorption studies and by TEM while the regularity of the structure was documented by XRD, which also served to exclude the presence of microporous crystalline grains. Instead, microporosity was detected by adsorption/desorption of water on tetrahedrally coordinated Ti-sites (XANES), by 119Xe NMR, by the comparison of the PDF with those of amorphous and of MFI-type solids, and by sequential decomposition of the structure directing agents for meso and micropore systems. From comparison of XRD and physisorption data and from the TEM micrographs, the thickness of the microporous mesopore walls was concluded to be ≈1.5 nm. Therefore, the failure of Ar physisorption to detect pores of sizes typical of MFI structures was attributed to the small micropore volume and the very short pore extension. The structural integrity of OMMs with 1-dimensional hexagonal pore system could be improved by a hydrothermal post-treatment despite the microporous nature of their pore walls, which resulted in more narrow mesopore size distributions peaking at somewhat larger pore sizes. © 2012 Elsevier Inc. All rights reserved.

The new hydrous layer silicate, RUB-55, was synthesized at 160 °C by hydrothermal synthesis from a reaction mixture of SiO 2/ tetramethylammonium hydroxide/ H 2O. The idealized chemical composition of as-made RUB-55 is [(CH 3) 4N] 2[Si 10O 18(OH) 6] · 16H 2O. The XRD powder pattern was indexed in tetragonal symmetry with lattice parameters of a 0 = 8.8Å and c 0 = 14.6Å. Physicochemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and DRIFT spectroscopy confirmed that RUB-55 is a hydrous layer silicate (HLS). The crystal structure was solved from model building. Rietveld structure refinement of the average structure in space group P42 1m converged to residual values of R Bragg = 0.029 and R F = 0.032 confirming the structure model. The structure of RUB-55 contains silicate layers with a topology that resembles the (001)-section of the sodalite framework as well as a (001)-section of the octadecasil framework. The layer can be regarded as made up by interconnected open, cup-like cavities. These "half-cages" are occupied by tetramethylammonium (TMA) ions which were used as a structure directing agent (SDA) during synthesis. A sheet of hydrogen bonded water molecules is intercalated between the silicate layers. The structure analysis also clearly revealed the presence of very strong hydrogen bonds between the terminal O atoms (silanol/siloxy groups) confirmed by 1H MAS NMR and DRIFT spectroscopy. RUB-55 is structurally and chemically related to the layer silicates RUB-15, HUS-1 and β-helix- layered-silicate. © by Oldenbourg Wissenschaftsverlag, München.

A new zeolite catalyst, Al-RUB-41, was synthesized for the first time. It was tested as a catalyst in methanol amination, and showed a shape-selective performance that results in a highly favorable product distribution. The shape-selective nature was also evidenced by using Pt-Al-RUB-41 as a bifunctional catalyst for decane hydroconversion. With its unique pore architecture and remarkable shape-selective character, Al-RUB-41 presents a significant commercial potential in industrial catalysis. © 2011 The Royal Society of Chemistry.

The activation of Au/TiO2 clusters encapsulated in MCM-48 and related poisoning phenomena were studied. With these catalysts, which contain extremely disperse Au particles (average size below 1 nm still after exposure to 473 K according to EXAFS), light-off temperatures of 250-280 K were obtained upon activation by precursor reduction in a net oxidizing CO/O2 feed, which is well comparable with state of the art Au/TiO2 catalysts. This activation was, however, found to be superimposed by parallel poisoning. In an operando XAFS study with catalyst batches containing Au(III) precursor species of different reducibility for unknown reasons, it was observed that the final activity was strongly influenced by the precursor reduction. Apparently, high activities were achieved by Au particles formed at low temperatures making contact with the clean support surface. Delayed Au(III) reduction produced particles of similar size but much lower activity, probably due to predominant contact with poisoned support species. The catalysts were most active right after an initial incomplete reduction of the Au(III) precursor and deactivated at higher temperature despite further Au(0) formation. However, as complete reduction of Au ions did not cause breakdown of CO oxidation activity, Au ions do not seem to be a part of the active site. The poisoning could be effectively removed by an inert gas treatment at temperatures up to 673 K, which resulted in light-off temperatures down to 225 K. Turnover frequencies derived for this state agree with data published recently for sub-nanometer bilayered Au particles, which supports the importance of sub-nanometer particles for CO oxidation over Au catalysts. From the absence of significant contributions from support oxygen in the Au LIII EXAFS spectra and of Au-derived signals in Ti K EXAFS spectra of reduced catalysts, it was concluded that there was no ordered relation between metal clusters and support surface, which appears therefore to be irrelevant for CO oxidation. © 2010 Elsevier B.V.

The layered silicate RUB-39 can be transformed by topotactic condensation into RUB-41 (RRO), a zeolite with 8- and 10- ring pores. If the layered RUB-39 is first silylated with dichlorodimethylsilane (DCDMS) or hexamethyldisiloxane (HMDS), an interlayer expanded structure is created after calcination. The DCDMS expanded material contains 10- and 12-ring pores instead of 8- and 10-ring pores. Detailed physicochemical characterization showed that the Al content is not significantly changed during the expansion. In the hydroconversion of decane, the expanded materials have a significantly increased activity, as demonstrated by the lower temperatures at which isomerization and cracking occur. Detailed comparison of the product selectivities obtained with RUB-41 or with its expanded analogs shows that the void structure of the expanded materials is significantly less constrained, as reflected in the distribution of methylnonane isomers, of the ethyloctane vs. methylnonane isomers, and in the ratio of monobranched vs. dibranched isomers. © 2011 Elsevier Inc. All rights reserved.

The energetic performance of two microporous siliceous materials, RUB-41 (RRO structure type) and S-SOD (SOD structure type) possessing medium-sized and very small pore openings, respectively, were studied using high-pressure water intrusion-extrusion experiments at room temperature. The pressure-volume diagrams of the RUB-41 material indicate a partly reversible phenomenon showing a slight hysteresis at the extrusion stage, which reveals that the water- RUB-41 system displays a shock-absorber behavior. Moreover, a shift toward the low pressure range was detected between the first cycle of water intrusion and the second one, indicating the creation of new defect sites in the inorganic framework after the intrusion process. Several investigations, mainly by 29Si solid-state NMR spectroscopy, confirm this observation. For the S-SOD material, no water intrusion was observed after three water intrusion-extrusion cycles. The highly hydrophobic character of the S-SOD material with its small pore opening or the value of the capillary pressure, which exceeds that tolerated by the instrument, are probably the two reasons for this result. © 2010 American Chemical Society.

Interlayer expansion reaction leads to a new family of microporous framework silicates using hydrous layer silicates as precursors. Using silylating agents such as dichlor-dimethylsilane (DCDMS), neighboring layers connect. In addition to the topotactic condensation of hydrous silicates, this leads to expanded silicate frameworks, with the number of pore openings increased by two Si-units. The hydrous layer silicate RUB-39 has been subjected to interlayer expansion reaction, using DCDMS at 180-C, yielding new, crystalline microporous frameworks (COE-1 and COE-2), varying in their methyl function carrying as-made and oxidized calcined forms, respectively. An intersecting two-dimensional (2D) channel system with 10- and 12-membered rings is accessible for probemolecules, leading to a surface area of 540m2/g and a pore volume of 0.169 cm3/g. The powder diagram was indexed in space group P2 with a = 15.609(3) Å, b = 11.163(1) Å, c = 7.301(1) Å, and β = 91.2(1)° for COE-1 and a = 15.594(4) Å, b = 11.039(2) Å, c = 7.276(1) Å, and β = 91.2(1)- for calcined COE-2. Rietveld refinement of the powder X-ray diffractometry (PXRD) diagram confirmed the framework topology for COE-1 and COE-2 (?2 = 8.0 and 9.9, respectively) and showed that the silicate framework suffers from stacking disorder after interlayer expansion reaction. DIFFaX simulations allowed for the modeling of the stacking disorder, showing that RRO- and HEU-type stacking occurs. © 2011 American Chemical Society.

Simple as that: A novel crystalline microporous titanosilicate (Ti-COE-4) with functionalized hydroxyl groups and medium micropore size (0.55nm) is successfully synthesized through dimethylsilylation and calcination. The synergism of hydroxyl groups with active Ti sites in Ti-COE-4 significantly improves its catalytic activities in oxidation reactions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Marine radiaxial-fibrous and fascicular-optic calcites are very common but poorly understood pore-filling cements in Paleozoic and Mesozoic marine neritic and upper bathyal limestones. The main diagnostic feature of these cements is their converging or diverging crystal c-axis, respectively. The reasons for this anomalous texture are at present unknown. Another controversy is due to the relative lack of occurrences in Cenozoic strata and their apparent absence in Quaternary marine limestones. Despite these uncertainties, marine fibrous cements are thought by some to be amongst the best proxies for the geochemistry of ancient oceans because of the absence of metabolic effects during their precipitation. Applying electron backscatter diffraction analysis, we here for the first time document radiaxial-fibrous and subordinate fascicular-optic fibrous biominerals from well-preserved Jurassic and Cretaceous low-Mg calcite belemnite rostra. The finding of fibrous biogenic calcites in combination with the recent description of Holocene and modern fibrous calcites in stalagmites represents-in the view of the authors-a significant advance in carbonate research. Here, these findings are placed in their wider, processes-oriented context and the significance of biogenic and speloan fibrous calcite for their marine counterparts is assessed. Comparing the physico-chemical and organomineralic properties of different precipitation sites indicates that the diagnostic variations in the crystal c-axis orientation are not related to a specific nucleation environment or substratum. In contrast, preliminary crystallographic analyses suggest that kinetic factors during nucleation or subtle gradients in the statistical replacements of Ca2+ by Mg2+ in the crystal structure may lead to local strain resulting in converging or diverging crystal c-axes. © 2011 Elsevier B.V.

Aluminum was incorporated into the layered silicate RUB-39, which is transformed by calcination into RUB-41. This new zeolite with RRO topology contains 8- and 10-ring pores, and the acid sites in the aluminated material catalyze the synthesis of methylamines, in particular mono- and dimethylamine, by amination of methanol. Owing to the shape-selective catalytic properties of (H)Al-RUB-41, low selectivity to the thermodynamically favored trimethylamine product is obtained in comparison with results on RUB-39 or non-shape-selective materials. Both activity and selectivity are highest for RUB-41 catalysts with a high Si to Al ratio. Silylation reduces the number of unselective sites and results in a further suppression of trimethylamine formation. The introduction of acidity in the intact RUB-41 structure is supported by Al-MAS NMR and NH 3-TPD data. Additional characterization by XRD and SEM is provided. © 2010 Elsevier Inc. All rights reserved.

CO oxidation was studied with a model catalyst containing Au and TiO x nanoaggregates confined in a siliceous MCM-48 host. With this material, which has a particular small ratio between the TiO x and Au components, activities well comparable to those of unconfined Au/TiO 2 catalysts were obtained in particular when a thermal activation in inert gas at temperatures between 523 and 673 K was applied. When the subsequent catalytic tests were performed in a feed containing ca. 20 ppm H 2O, strong deactivation phenomena were observed which could be reverted by repeated thermal treatment and are most likely caused by carbonate deposition. This deactivation was strongly attenuated when the water content of the feed was decreased to ca. 6 ppm, which suggests that water plays an important role in the formation of the poisoning species. With unconfined Au/TiO 2 catalysts, a promoting role of water on the formation of catalyst poison was observed as well, but to a much lower extent. The effect may therefore have escaped undetected so far as a contribution to the well-known catalyst deactivation by carbonate species. © 2011 Springer Science+Business Media, LLC.

Hexagonal mesoporous solids were synthesized from solutions containing TS-1 seeds. The products were characterized by XRD, nitrogen and argon physisorption, TEM, TG/DTA of template decomposition (also after extraction of the mesopore template), UV-Vis and IR spectroscopy, and XANES at the TiK edge. Their catalytic activities were assessed for cyclohexene epoxidation in hydrophilic and hydrophobic environment (CH3OH/water, with H2O2 oxidant, and decane, with tert-butyl hydro-peroxide oxidant, respectively) and for n-hexene epoxidation in hydrophilic environment. The mesopore system was clearly documented by XRD, physisorption measurements, and TEM, whereas evidence for micropores by physisorption proved elusive. However, the micropore template was detected in the solids by TG/DTA even after extraction of the mesopore template, and among the Ti sites, which were confirmed to be tetrahedrally coordinated by UV-Vis and XANES, a clear majority was able to coordinate two water molecules. It was concluded that the pore walls had been built up from nanoparticulate TS-1 precursors resulting in walls of ca. 1.5 nm thickness, which resemble rather the exterior layers of a TS-1 crystallite than its (hydrophobic) interior. In cyclohexene epoxidation, the micro-mesophases were by 1-2 orders of magnitude more active than TS-1 and outperformed also Ti-MCM-41, at similar selectivity in hydrophobic medium. With 1-hexene in hydrophilic medium, however, the micro-mesophases failed completely whereas TS-1 exhibited high activity. © 2009 Elsevier Inc. All rights reserved.

We discuss how kinetic effects can be utilized to prepare polar ZnO(0001)-Zn surfaces as very well defined and single-crystalline surfaces by hydroxide stabilization of the polar face via a wet chemical etching process in 3N NaOH. An in situ AFM imaging study of the etching process is presented. In addition, measurement and analyses of grazing incidence X-ray diffraction experiments, reflectivity, and crystal truncation rods (CTRs) of the resulting ZnO(0001) surface structures in both dry and humid atmospheres are discussed. Analysis of the CTRs shows that these surfaces are topographically extremely flat, Zn-terminated, but covered with a defect-containing hydroxide/oxygen adlayer, which is adsorbed at hcp-hollow sites. This result is fully consistent with a stabilization of the polar surface by means of an adlayer of disordered hydroxides, which is adsorbed at hcp positions. Moreover, these studies indicate that the water structure at the solid/liquid interface is ordered within the first few layers, but no evidence for an "icelike" structure was found. Also, the pH-dependent stability of these hydroxide-stabilized ZnO(0001) surfaces within electrolyte solutions was investigated by means of an ex situ LEED approach. Hydroxides effectively stabilize the (0001) surface within a wide range of pH values between 11 and 4. In acidic solutions below pH 3.8, the formation of deep hexagonal etching pits is observed, whereas a crystalline structure with triangular reconstructions evolves between these etching pits. The origin of the hexagonal etching pits is discussed as a result of faster dissolution kinetics at dislocation sites. © 2010 American Chemical Society.

A new layered ammonium nickel(II) diphosphate, (NH4) 2[Ni3(P2O7)2(H 2O)2], has been synthesized ionothermally in the ionic liquid 1-butyl-3-methyl imidazolium bromide and characterized by powder X-ray diffraction, elemental analysis, scaning electron microscopy, thermogravimetry etc. The results of the characterization show that the crystal adopts the monoclinic space group P21/a with the lattice constants a = 9.23529(2) Å, b = 7.98489(2) Å, c = 9.40772(2) Å, β = 100.2608(2)° and Z = 2. Its structure consists of chains of cis- and trans-edge-sharing [NiO6]-octahedra linked via [P2O 7] units to form layers of [Ni3(P2O 7)2(H2O)2]2- in the ab plane. Adjacent layers are separated in the c-direction by ammonium ions. © 2010 Elsevier B.V. All rights reserved.

Figure Presented Open for business: The first aluminophosphate molecular sieve with 20-ring pore openings has been synthesized ionothermally using a co-structure-directing agent (see figure; H white, C turquoise, N blue). The new material has a -CLO framework and excellent stability in comparison to the QaPO4 analogue cloverite. These characteristics indicate its potential applications in separation, catalysis, and gas storage. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA,.

An LEV-type aluminosilicate zeolite RUB-50 was synthesized in the presence of diethyldimethylammonium (DEDMA) cation as a structure-directing agent (SDA), and its crystal structure was analyzed in detail by the Rietveld refinement and the maximum entropy method (MEM). RUB-50 was crystallized from an Al-containing mother gel with relatively low water content. As-made RUB-50 contained a large amount of organic SDAs in the cavity, and therefore calcined RUB-50 exhibited a large micropore volume. Through the MEM analysis of the as-made RUB-50, the actual conformation of the SDA molecule occluded in the cavity emerged. In accordance with the structural analysis, quaternary ammonium cations possibly having molecular conformations similar to that of DEDMA successfully direct the crystallization of LEV-type zeolites. © 2009 Elsevier Inc. All rights reserved.

ZSM-18 related zeolite UZM-22, framework type MEI, was synthesized with choline as structure directing agent (SDA). Sr2+ and Li+ are additional essential components in the synthesis. Rietveld structure analysis of the as synthesized sample confirmed the proposed crystal structure in space group P63/m with a = 13.1544(7) and c = 15.7409(3) and composition (Sr1.17Li0.05)[Si27.92Al6.08 O68]*3.69SDA*23.85H2O. Calcination showed that the material is stable up to at least 600 °C. Solid state NMR experiments revealed that the framework de-aluminated upon calcination and that Li is part of the as-made material as cation. N2 adsorption experiments confirmed the low framework density with a high surface area of 592 m2/g. The 12R pore has a diameter of 6.9 Å. Ammonium TPD revealed a high number of acid sites. © 2009 Elsevier Inc. All rights reserved.