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The isothermal, low-temperature stepwise conversion of methane to methanol over copper-exchanged zeolites eliminates the time-consuming heating and cooling steps of the conventional high temperature activation approach. To better understand differences between the two approaches, a series of zeolites were screened, of which omega zeolite (MAZ) showed superior performance in both the isothermal and conventional approaches.

Methane is often flared due to the heavy economic burden of transportation, particularly at rural petroleum extraction sites. Directly converting methane to methanol is possible through a stepwise process with copper- exchanged zeolites. Factors affecting this conversion are not yet fully understood. Omega zeolite ( MAZ) can yield 197 mu mol per gram- zeolite, the highest reported thus far. Here we show that the synthesis and resulting morphology of the zeolite play an enormous role in the yield of methanol. High yields are only achieved when the zeolite has a longer stick- like bundled morphology ( 2- 4 mu m by 100 nm). When the zeolite forms small spherulitic aggregates, the methanol yield is severely diminished ( 60- 97 mu molmethanol per gram- zeolite). This difference originates from minute changes in the synthesis procedure, emphasizing the extreme sensitivity of zeolite properties towards synthesis conditions. This work shows that selecting a parent zeolite is crucial and is an opportunity for process optimization to achieve high and industrially- relevant methanol yields.

Zeolite mordenite (MOR) is one of the most studied zeolites for the stepwise direct conversion of methane to methanol, but it also can exist in two forms: large port and small port. Here we report that the synthesis and selection of the parent mordenite is critical for optimizing productivity, and that large-port mordenite outperforms small-port mordenite for the stepwise conversion of methane to methanol.

International audience; A family of Al-rich ZSM-5 zeolites with Si / Al = 8 ± 0.5 was prepared according to a biomass-mediated supramolecular approach. A combination of advanced characterisation techniques and periodic density functional theory (DFT) calculations unraveled the purity and stability of unexpected Al-enriched ZSM-5 structures, hence allowing to cross the frontier of Si / Al lower limit. In addition, these Al-rich ZSM-5 zeolites demonstrated high catalytic activity in n-hexane cracking and methanol conversion into hydrocarbons, being in line with the presence of numerous BrØnsted acid sites.

A study exploring the use of ionic liquid reactions based on imidazolium halides in molecular sieve synthesis has produced a novel zincoaluminophosphate material with an open DFO-type framework structure. This framework structure had only been observed previously in the magnesioaluminophosphate system (Mg-DAF-1) where decamethonium was used as the structure directing agent. The new Zn-DAF-1 material has been characterized using chemical and thermogravimetric analysis and ^(13)C, ^(19)F, ^(27)Al and ^(31)P MAS NMR techniques. Structure analysis (P6/mcc, a = 22.2244(1) Å, c = 42.3293(3) Å) using synchrotron powder diffraction data not only confirmed the framework structure, but also revealed the locations of the Al, P and Zn atoms in the framework, the N,N′-di-isopropyl-imidazolium (DIPI) ions in the pores, some fluoride ions associated with double 4-rings, and some water molecules and anions filling the remaining space. This level of structural detail had not been possible in the Mg-DAF-1 material. Four different locations for the DIPI cation were found in the two 12-ring channels and Zn was found to substitute for only one of the six crystallographically distinct Al sites to yield the approximate crystal chemical formula |(DIPI)_(17)(OH,F)_(11)(H2O)_(23)|[Zn_6Al_(126)P_(132)O_(528)]-DFO.

Using heavy-atom labeling in conjunction with electron microscopy, we here visualize the distribution of point defects, i.e. internal silanol groups, in silicalite-1 zeolites at the single crystal level., Chemical Communications, 55 (4), ISSN:1359-7345, ISSN:1364-548X

The potential of valence to core Al X-ray emission spectroscopy to determine aluminum distribution in ferrierite zeolites was investigated. The recorded emission spectra of four samples prepared with different structure directing agents exhibit slight variations in the position of the main emission peak and the intensity of its low energy shoulder. Theoretical calculations indicate that an increased intensity of the Kβx shoulder in the Al emission spectra can be linked to a predominant occupation of the T3 site by a single aluminum atom. This study thus suggests that valence to core X-ray emission spectroscopy can be applied to help determine the occupation of aluminum at crystallographic T-sites in zeolites.

Large ZSM-5 zeolite crystals synthesized in fluoride medium show an astonishing activity, stability as well as selectivity towards light olefins in the Methanol-To-Olefins (MTO) reaction. By proper control of the synthesis parameters, ZSM-5 single crystals of unprecedented high quality are produced. The absence of usually uncontrollable variables such as structural defects, external non selective surface acid sites and extra-framework aluminium (EFAl) species was evidenced by SEM, HRTEM, CO-FTIR, 27Al and 19F MAS-NMR, Rietveld structure refinement and N2- and Ar-gas sorption measurements. Interestingly, diffusivity evaluation of different probe molecules (toluene, benzene and neopentane) has been carried out with PFG-NMR, allowing casting light on an interesting structure-diffusion-activity relationship. A “levitation” effect could be experimentally demonstrated and its impact on catalysis is highlighted in a rationalization attempt: Maxwell-Boltzmann based diffusion models properly predict product distributions for this counter-intuitively outstanding Methanol-To-Propylene (MTP) catalyst.

Funding: Royal Society for provision of an industry fellowship and the EPSRC for funding (EP/K025112/1 and EP/L014475/1) (R.E.M.); Czech Science Foundation for (P106/12/G015) (J.Cˇ.); European Community under a Marie Curie Intra-European Fellowship (A.B.P.). Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure-directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8-rings all the way to extra-large pores consisting of 14-rings. Publisher PDF

A preliminary inspection of natural zeolites samples in the north east of Ethiopia showed a large deposit of highly pure stilbite (hereafter called |CaNa|-STI). Rietveld refinement of synchrotron powder diffraction data (C2/m, a = 13.62(1) Å, b = 18.2563(1) Å, c = 11.28(1) Å, β = 127.8(2)°) has shown that both Ca2+ and Na+ ions reside at the intersection of the ten- and eight-ring channels, and are completely surrounded by H2O molecules that make close contacts with the zeolite framework. Therefore, no coordination of the cations with framework oxygen atoms is observed. In an attempt to improve the defluoridation capacity, |CaNa|-STI was subjected to a NH4+ and subsequent Ca2+ ion-exchange treatment. Analysis of the diffraction pattern of the |Ca–NH4|-STI sample revealed the presence of a mixture of crystals with monoclinic and orthorhombic symmetry. This double-exchange treatment notably improved the ability of this material to remove fluoride from water, what is probably related to the formation of connectivity defects that are generated during the exchange treatments., The financial support from the Spanish Ministry of Foreign Affairs-Spanish Agency for Cooperation and Development through the Scientific Cooperation Program project number A1/035517/11 is acknowledged.

Hydrolysis of germanosilicate zeolites with the IWW structure shows two different outcomes depending on the composition of the starting materials. Ge-rich IWW (Si/Ge=3.1) is disassembled into a layered material (IPC-5P), which can be reassembled into an almost pure silica IWW on treatment with diethoxydimethylsilane. Ge-poor IWW (Si/Ge=6.4) is not completely disassembled on hydrolysis, but retains some 3D connectivity. This structure can be reassembled into IWW by incorporation of Al to fill the defects left when the Ge is removed., Angewandte Chemie, 53 (27), ISSN:1521-3757, ISSN:0044-8249

The alkenyl substituted zirconocene complexes, [Zr(η5-C5H4{CMeRCH2CH2CH = CMe2})2Cl2] (R = Me (1), Ph (2) were prepared from the reaction of the lithium derivative Li(C5H4{CMeRCH2CH2CH = CMe2}) (R = Me, Ph) with zirconium tetrachloride. The bulky alkyl substituted cyclopentadienyl ligand precursor was prepared as its fulvene derivative (C5H4) = CMeCH2CHMe2 (3) via the reaction of cyclopentadiene with 4-methyl-2-pentanone and then converted to Li(C5H4{CMe2CH2CHMe2}) (4) via nucleophilic attack of LiMe. The reaction of 4 with [TiCl4(THF)2] and ZrCl4 gave the metallocene complexes [M(η5-C5H4{CMe2CH2CHMe2})2Cl2] (M = Ti (5), Zr (6)), respectively. The ansa-ligand precursor, SiMe2(C5HMe4)(C5H4{CMe2CH2CHMe2}) (7), was prepared via the reaction of 4 with SiMe2(C5HMe4)Cl and subsequently converted to its dilithium derivate, Li2(Me2Si(C5Me4)(C5H3{CMe2CH2CHMe2})) (8), using n-butyllithium. The ansa-zirconocene complex, [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9), was synthesized by the reaction of 8 with zirconium tetrachloride. Compounds 1–9 were characterized by 1H and 13C{1H} NMR spectroscopy. In addition, the molecular structures of 5, 6 and 9 were determined by single crystal X-ray diffraction studies. The metallocene complexes have been tested as catalyst (with co-catalyst MAO) in the polymerization of ethylene where the substituents on the cyclopentadienyl ligand have a direct influence on the catalytic activity.

The Authors would like to thank: The EPSRC (grant EP/K025112/1) and the Czech Science Foundation grant no. P106/12/G015 (Centre of Excellence) for funding opportunities and beam lines I15 and I11 at the Diamond Light Source. Nicola Casati and Antonio Cervelino from the MS Powder beamline at the Swiss Light Source are acknowledged for their support in the data collection. A.B.P. acknowledges the support of the European Community under a Marie Curie Intra-European Fellowship for Career Development. The disordered intermediate of the ADORable zeolite UTL has been structurally confirmed using the pair distribution function (PDF) technique. The intermediate, IPC-1P, is a disordered layered compound formed by the hydrolysis of UTL in 0.1M hydrochloric acid solution. Its structure is unsolveable by traditional X-ray diffraction techniques. The PDF technique was first benchmarked against high-quality synchrotron Rietveld refinements of IPC-2 (OKO) and IPC-4 (PCR) – two end products of IPC-1P condensation that share very similar structural features. An IPC-1P starting model derived from density functional theory was used for the PDF refinement, which yielded a final fit of Rw = 18% and a geometrically reasonable structure. This confirms the layers do stay intact throughout the ADOR process and shows PDF is a viable technique for layered zeolite structure determination. Postprint

The skeletal isomerization of n-butenes to isobutene has been carried out over ferrierite catalysts (Si/Al ~ 15) containing different acid sites distribution and different amount of defects. The zeolite crystals were synthesized under hydrothermal conditions in fluoride medium in the absence of alkaline cations by using suitable combinations of structure directing agents. Template-driven low density of acid sites in 10-membered-ring channels enhances the isobutene selectivity and decreases catalyst deactivation. The presence of high amount of silanol groups and Lewis acid sites increases the yields of by-products and catalysts decay., MICINN (CTQ2006-06282) CSIC (JAE-doc contract)

The germanosilicate ITQ-24 (IWR framework type) was synthesized in fluoride medium using 1,3,5-tris(1,2-dimethylimidazolium) benzene as the structure directing agent (SDA). A structure analysis of the as-synthesized ITQ-24 material using synchrotron powder diffraction data and difference electron density calculations have allowed the fluoride ions and the germanium atoms to be located and the conformation of the SDA to be determined. The benzyl ring is perpendicular to the b axis with the three imidazolium moieties forming a “T-shaped” arrangement. Ge atoms replace some of the Si in the double-4-ring (d4r) and in one of the single-4-rings (s4r). The other s4r contains only Si. Fluoride ions are in the d4r units. Initially, the space group Cmmm (highest possible symmetry) was assumed, but the framework geometry was strained. An independent evaluation of the symmetry using the powder charge flipping algorithm in Superflip led to a successful refinement with reasonable geometry and a refined composition of |[(C_6H_3)(C_7H_(10)N_2)_3]_2F_2|[Si_(40.2)Ge_(15.8)O_(112)] in the space group Pban.

Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact., Nature Communications, 6, ISSN:2041-1723

Adsorption of ethane in a slit shaped micropore system has been studied by Monte Carlo molecular simulation by considering this hydrocarbon as a two interacting sites molecule. Ethane adsorption in pore sizes from 0.41 to 1.66 nm was simulated at 303 K. Microscopic characteristics of the adsorbed phase have been studied for pores of different size, comparing two density profiles: the molecule centre of mass profile and the molecular interaction site profile. Averaged angle distribution of molecule positions with respect to the slit plane across the pore width has been also obtained by simulation. These results were related to ethane molecule packing efficiency, which is also related to the adsorption capacity in terms of the adsorbed phase density. Packing efficiency presents an oscillation shape as the result of the adsorbate disorder inside the pore. Pressure influence on the adsorption has been studied by following pore filling by simulation. When pore condensation takes place and for pressures above condensation, fluid-fluid interactions are determinant in molecule disorder observed between the two adsorbed layers.

© 2014 American Chemical Society, 1,3-Diphenylguanidine (DPG) has distinguishable polar and apolar groups, aromatic rings that can self-assemble through π-π type interactions, and high conformational flexibility. These features make it a potential self-assembling structure-directing agent in the synthesis of hybrid host-guest aluminophosphates. Computational simulations show that the molecule has a strong tendency to self-assemble in aqueous solution. Large supramolecular organic aggregates are produced, with the hydrophobic aromatic rings located in the center of the aggregates, stabilized by π-π type interactions, and the hydrophilic guanidine groups on the external surface in close contact with water molecules. With this organic molecule, a new 1-D AlPO framework material (ICP-1) was formed. Its structure, characterized by a combination of single-crystal and powder diffraction techniques, consists of AlP 2O8H chains connected to the polar groups of the organic DPG molecules through a complex H-bonding network. This material has an extremely high organic content, close to that of typical mesoporous materials. However, DPG molecules are part of the ICP-1 network, rather than guest molecules in the pores, so removal of DPG results in a collapse of the structure, limiting its potential applications. Nevertheless, this work demonstrates the potential of using self-assembling organic molecules for producing very open-framework materials., The research leading to these results has received funding from the Spanish Ministry of Science and Innovation MICINN (Projects MAT2009-13569 and MAT2012-31127) and the European Research Council, under the Marie Curie Career Integration Grant program (FP7-PEOPLE-2011-CIG), Grant Agreement PCIG09-GA-2011-291877. L.G.-H. acknowledges Ministerio de Economıa y Competitividad for a Ramón y Cajal ́ contract (RYC-2012-11794) A.B.P. acknowledges the support of the European Community under a Marie Curie IntraEuropean Fellowship for Career Development

The tailoring of the aluminum distribution over the various T sites in zeolites remains a major challenge. By using differing combinations of templating molecules, we managed to control the aluminum siting over the T sites as identified by 27Al MQ MAS NMR in samples of the same Si/Al ratio. This is unique evidence of a modified aluminum distribution in samples prepared following a strategy to tailor the location of aluminum in the zeolite ferrierite framework., A.B.P. is thankful for the support of the European Community under a Marie Curie Intra-European Fellowship for Career Development. Funding from the Spanish Ministry of Economy (project MAT2012-31127) is greatly acknowledged.

Analysis of the structure of the zeolite ferrierite (framework type FER) synthesized using a combination of tetramethylammonium (TMA) and pyrrolidine as organic structure-directing agents (|((CH3)4N) 0.4((CH2)4NH)3.6H 1.7|[Si33.9Al2.1O72]) has revealed that TMA ions reside exclusively in the [58668 2] cavities of the FER framework, whereas pyrrolidine species are found in both the [586682] cavities and the main 10-ring channel. A similar, but not identical, arrangement of pyrrolidine molecules was found for a sample synthesized with pyrrolidine as the only SDA (|((CH2)4NH)4.2H2.2|[Si 33.8Al2.2O72])). A comparison of the two structures shows the influence of TMA on the location of pyrrolidine and the framework Al. Pyrrolidine species establish stronger interactions with the zeolitic framework than does TMA, suggesting a different ability of the amine to exert an influence on the aluminum distribution of the zeolite. These findings have implications in the catalytic performance of the samples. © 2013 American Chemical Society., A.B.P. acknowledges the support of the European Community under a Marie Curie Intra-European Fellowship for Career Development. L.G.H. acknowledges the Spanish Ministry of Economy for a Juan de la Cierva contract. The Spanish Ministry of Economy has funded this work (project MAT2012–31127) .

A synthesis strategy to tailor the acid sites location in ferrierite crystals has been developed. The zeolite catalysts were synthesised in fluoride medium using different combinations of organic structure directing agents (SDAs) in the absence of inorganic cations. Therefore, the negative charge associated to the incorporation of aluminium to the framework was compensated exclusively by the positive charge of the organic SDAs. In this way, Al sitting in the zeolite framework was driven by the specific location of the different SDA molecules within the zeolite void volume. Following this synthesis strategy, it has been found that the distribution of strongly acidic hydroxyl groups in the proton form of the zeolites obtained after removal of the organic templates was dependent on the combination of organic molecules used as SDAs. Moreover, the catalytic activity of the zeolites in m-xylene and 1-butene isomerisation increased as the relative population of strong Brönsted acid groups in sterically constrained sites inside the ferrierite cavity decreased., This work has been financially supported by the MICINN (project CTQ2006-06282).

Ferrierite synthesis from gels containing a mixture of two template molecules, in the absence of inorganic cations and in fluoride media, is described. One of them is a bulky structure-directing agent (SDA), 1-benzyl-1-methylpyrrolidinium cation (bmp), and the other one is a small organic cation acting as a co-template. We present here the results obtained with tetramethylammonium (TMA) and quinuclidinium (Qui) compounds as co-templates in a gel containing bmp cation as SDA. It has been observed that in both cases co-templates exert a marked effect on the nature of the synthesis products, This work has been financially supported by the CICYT (project CTQ2006-06282).