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International audience; The rich diversity and complexity of organic matter found in meteorites is rapidly expanding our knowledge and understanding of extreme environments from which the early solar system emerged and evolved. Here, we report the discovery of a hitherto unknown chemical class, dihydroxymagnesium carboxylates [(OH)(2)MgO2CR](-), in meteoritic soluble organic matter. High collision energies, which are required for fragmentation, suggest substantial thermal stability of these Mg-metalorganics (CHOMg compounds). This was corroborated by their higher abundance in thermally processed meteorites. CHOMg compounds were found to be present in a set of 61 meteorites of diverse petrological classes. The appearance of this CHOMg chemical class extends the previously investigated, diverse set of CHNOS molecules. A connection between the evolution of organic compounds and minerals is made, as Mg released from minerals gets trapped into organic compounds. These CHOMg metalorganic compounds and their relation to thermal processing in meteorites might shed new light on our understanding of carbon speciation at a molecular level in meteorite parent bodies.

The mechanism of fast hydrogen generation from pure water using selectively activated Al-SnCl2 composites was elucidated with the help of experimental data using combined XRD, SEM, EDX, DSC and calorimetric techniques. It is found that H-2 is produced from two different but simultaneous routes specific to the Al-SnCl2 composite stoichiometry achieved after ball milling the precursor that readily yields, besides the excess of Al, Sn and AlCl3. Hydrogen is simultaneously produced from the reaction of the so-formed Al-Sn alloy with water, and from the reaction of the in situ generated AlCl3 with water, yielding HCl (protons) that further again react with Al, both reactions significantly increasing the hydrogen production rate. The effect of Bi on the hydrogen conversion yield on the Al-SnCl2 composite was also investigated. The electrochemical activity of Al is further enhanced by doping Bi into Al-SnCl2 composite. Meanwhile, DFT (density functional theory) calculations show that Bi micro domains present onto the Al (111) crystallite faces of the composite significantly reduce the adsorption energy of the OH groups while, Mg- or Cr-doped Al-SnCl2 composites increase this adsorption energy. The Mulliken charge analysis indicates that Bi leads to less electron transport between Al and O atoms (weaker interaction) than pristine Al (111) surface. Bi therefore contributes to inhibit the formation of the hydroxyls on the Al metal surface, thereby allowing the clean metal to continuously react with water. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Transition metal halides are mostly used as dopants to improve the hydrogen storage properties of lialh4, but they will cause hydrogen capacity loss because of their relatively high molecular weights and reactions with lialh4. to overcome these drawbacks, active nano-sized tih2 (tih2nano) prepared by reactive ball milling is used to dope lialh4. it shows superior catalytic effect on the dehydrogenation of lialh4 compared to commercial tih2. tih2nano-doped lialh4 starts to release hydrogen at 75 degrees c, which is 80 degrees c lower than the onset dehydrogenation temperature of commercial lialh4. about 6.3 wt.% h-2 can be released isothermally at 100 degrees c (800 min) or at 120 degrees c (150 min). the apparent activation energies of the first two dehydrogenation reactions of lialh4 are reduced by about 20 and 24 kj mol(-1), respectively. meanwhile, the regeneration of lialh4 is realized through extracting the solvent from lialh4 center dot 4thf, which is obtained by ball milling the dehydrogenated products of tih2nano-doped lialh4 in the presence of thf and 5 mpa h-2. this suggests that tih2 is also an effective catalyst for the formation of lialh4 center dot 4thf. copyright (c) 2012, hydrogen energy publications, llc. published by elsevier ltd. all rights reserved.

Two metal-organic frameworks, Ca(2,6-NDC)(DMF) (1) and Mn3(2,6-NDC)3(DMF)4 (2) (where 2,6-NDC = 2,6-naphthalene dicarboxylate and DMF = N,N′-dimethylformamide) have been solvothermally synthesized under optimized conditions and characterized by X-ray powder diffraction, elemental analysis, FT-IR spectroscopy, and TG analysis. The thermal decomposition characteristics were investigated under air atmosphere from 300 to 1,170 K (for 1) and from 300 to 971 K (for 2). The molar heat capacities were measured from 198 to 548 K (for 1) and from 198 to 448 K (for 2) by temperature modulated differential scanning calorimetry (TMDSC) for the first time. The fundamental thermodynamic parameters such as entropy and enthalpy variations with temperature were calculated based on the experimentally determined molar heat capacities.

Numerous descriptions of organic molecules present in the Murchison meteorite have improved our understanding of the early interstellar chemistry that operated at or just before the birth of our solar system. However, all molecular analyses were so far targeted toward selected classes of compounds with a particular emphasis on biologically active components in the context of prebiotic chemistry. Here we demonstrate that a nontargeted ultrahigh-resolution molecular analysis of the solvent-accessible organic fraction of Murchison extracted under mild conditions allows one to extend its indigenous chemical diversity to tens of thousands of different molecular compositions and likely millions of diverse structures. This molecular complexity, which provides hints on heteroatoms chronological assembly, suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biological- and biogeochemical-driven chemical space.

Nanometric Fe2O3 particles could be inserted inside the internal pore volume of SBA-15 mesoporous silica when Fe(III) chelates (EDTA, gluconate and citrate) were used as impregnating precursors. Fe(III) nitrate preferentially yields 8 nm uniformly sized Fe2O3 clusters that selectively plug the SBA-15 channels through a geometric confinement effect. An oxidative degradation of Fe-chelate precursors yielded Fe(III) oxidic particles of various sizes and dispersion, depending on the nature and geometry of chelate anion. Fe(EDTA) precursors specifically generated Fe2O3 nanoparticles that selectively migrate towards two types of positions where the silica surface exhibits a high curvature. In samples involving low Fe loadings, Fe2O3 particles first creep towards the silica micropore mouths (nests), in which they are readily confined and stabilized. For higher Fe loadings, when most of the micropore nests were filled, oxidic particles eventually settle as a superficial film on the mesopore walls and undergo stabilization onto the surface roughness that can also favors their confinement, as theoretically predicted by Derouane and co-workers. Upon further reduction, as selectively followed by combined cyclic voltammetry and TPR, Fe2O3 readily yield FeO nanoslabs that remain even more efficiently confined within their respective nest positions through a further acid–base type stabilization.

Monolithic megaloporous carbon cryogels were examined for their potential applications as cathodic electrodes in secondary zinc–bromine cells. This work investigates the possibility of using their particular macroporous texture as microscopic bromine tanks in a zinc/bromine battery. The electrochemical behaviour of a cell based upon such a Br 2 electrode was studied and discussed in terms of energy yields, energy storage capability and cycle life. Good storages (over 20 Wh kg −1 ) could be obtained during the first 2 h of cell charging for currents between 10 and 20 mA g −1 . The energy yield remains almost constant during a fairly large number of cycles, basically for weak charges (e.g. 25 C g −1 ). Our findings show that the good cyclability of the cathodic electrode is a consequence of the liquid state of the active bromine phase.

The selective synthesis of phytosterol esters from natural sterols and methyl esters was investigated on new grounds by a chemical process using basic solids that are reusable, active, and more selective than the currently used homogeneous catalysts (e.g., alkali hydroxides, carbonates). Various lanthanum oxides with different synthesis procedures and varying specific surface areas were tested. The catalytic performance of the new solids and, more specifically, the ability of La2O3 oxides in increasing phytosterol ester selectivity, was correlated with their acido-basic properties, which were fully characterized by infrared spectroscopy. All La2O3 oxides involved surface carbonate species with different structural states and strengths, as revealed by propyne adsorption. The selectivity to phytosterol ester varied from 90 to 96%, confirming that the side reaction of dehydration of β-sitosterol was strongly inhibited. The phytosterol ester yield could reach 89% and was related to the basic strength of the carbonate species. The lower the carbonate basicity, the higher the phytosterol ester yield. Moreover, IR spectra of catalysts diluted in KBr powder showed that the higher the intensity of unidentate carbonate bands, the higher the yield. It was concluded that the synthesis of phytosterol esters from fatty methyl esters and sitosterols in the presence of La2O3 catalysts requires ionic carbonate species of medium basic strength.

International audience; SBA-15 with a 2D hexagonal mesoporous structure exhibiting a narrow pore size distribution and commercial AEROSIL380 silica were used as supports for the dispersion of Ni, Co or Fe metal oxide particles. After reduction at 973 K, catalytic properties of these materials were evaluated for ethanol conversion to H-2 and carbon nanotubes (CNTs). The reduced composites were selective for hydrogen production as follows: iron (45-55%) < cobalt (55-70%) < nickel (70-80%) regardless of the type of silica used as support. The nickel-based catalysts appeared to be the most active for the production of hydrogen and also generate carbon nanotubes in large amounts, independently of the support porosity. HRTEM micrographs showed a generally well-defined morphology and a quite uniform outer diameter of CNTs produced using the Ni composites. The texture of the silica support had however a particular influence on the catalytic properties of the cobalt-based catalysts. Both Ni and Co supported on SBA-15 silica generate a mixture of CNTs and carbon nanofibers (CNFs) with a wider size distribution compared with that of the CNTs produced over Ni/Aerosil. This lack of selectivity was attributed to the expelling of Co particles from the SBA-15 mesoporous channels upon reduction. All Fe/silica materials proved the least active and selective. Along the major carbon fibers, they generate a few poorly defined multi-walled CNTs with small diameter. TG analysis indicated that all CNTs exhibit a relative high stability in an oxidizing atmosphere.

A combination of advanced powder diffraction and NMR techniques have allowed the structure of the novel microporous aluminophosphate IST-1 ( | (CH3NH2)4(CH3NH3+)4(OH−)4 | [ Al12P12O48 ] ) to be elucidated. The framework structure was determined in the non-centrosymmetric space group Pca21 (a=9.61523(1) A, b=8.67024(1) A, c=16.21957(2) A) from high-resolution synchrotron powder diffraction data using the program FOCUS. Extra framework species were then located on difference electron density maps. A hydroxyl group was found to bridge between two of the framework Al atoms, and one methylamine species, presumably protonated, could be located in the channels where it H-bonds to three framework oxygens. The most unusual feature of the structure is the second methylamine molecule, which bonds directly to a framework Al atom. The structure is entirely consistent with 31P and 27Al MAS NMR studies, which showed there to be three P (all 4-coordinate) and three Al (one 4-, one 5- and one 6-coordinate) sites, and with 13C MAS NMR, which showed there to be two different types of methylamine species in equal amounts. Assignment of the 31P, 27Al and 13C MAS NMR signals could be deduced from the crystallographic data,31P-27Al HETCOR spectra and ab initio calculations.

A nanoscale aluminium-based metal organic framework (NMOF) with high thermal stability has been synthesized, which shows high H(2) and CO(2) uptake capacities and an excellent selectivity for CO(2) over N(2) and O(2).

Starting from an as-synthesized Na-bearing MCM-41 sample with Si/Al=20, several Cs or K exchanged samples have been obtained. All samples, both washed after exchange to remove the excess alkali–metal salt and unwashed, were characterized by studying in the IR the adsorption of CO at a nominal temperature of 77 K, and of CO 2 at room temperature. On unwashed samples, after thermal treatment at 500 °C, a basic alkali-oxide phase and a surface silicate were detected. In contrast, washed samples did not exhibit basic character and only Lewis acidic cationic centers were detected, the strength of which is close to that of alkali-cation exchanged ZSM-5 systems. Unwashed samples were inactive in the isomerization of 1-butene. Washed samples converted 1-butene to cis/trans -2-butene, with a ratio close to one (the presence of isobutene was negligible), as typical of mildly acidic Bronsted centers, which are probably present even after exchange: indeed, a sample of Al-MCM-41 in the protonic form, tested as reference, gave the same reaction with highest activity.

Acetylenes may behave either as acidic or basic probes, by virtue of the C–H group, which is acidic, and of the CC triple bond, which can interact with positively charged centers, such as acidic hydroxyls or metal cations. The interaction of methylacetylene and acetylene with alkali-metal cations, acting as Lewis sites in MCM-41 materials, is studied through combined spectroscopic and ab initio techniques. On the experimental side, MCM-41 materials with low Al content, exchanged with aqueous solutions of alkali-metal nitrates, have been selected as they provide exposed alkali-metal cations with few basic adjacent oxygens. On the computational side, ab initio density functional techniques have been applied to minimal cluster models, consisting one cation (Li, Na, K, Cs) and one molecule (either acetylene or methylacetylene). A thorough characterization of the adsorption of acetylenes on Lewis acidic centers is provided, enlightening the presence of two contributions to the interaction, namely that with alkali-cations, through the CC triple bond, and the one with basic oxygen species near the Lewis acidic sites, through H-bonding.

Light-fastness properties of composites involving mesoporous calcium-modified aluminosilicate substrates (MCM-41 structure) and dye (Lithol Rubine B) were examined. High surface area Al-MCM-41 materials synthesized in the presence of Ca 2+ ions proved efficient hosts for Lithol Rubine B, yielding mesophase–dye composites with the highest light-fastness qualities, when compared to Ca-exchanged Al-MCM-41 aluminosilicates, to non composite pigment or to smectite–dye composites. The marked resistance of the new composites to fading was attributed to an optimized Ca–dye interaction favored by a controlled heating the Ca(OH) 2 -loaded mesoporous precursors, yielding tiny CaO particles, highly dispersed and retained onto the large internal surface of the substrate.

A series of binary Cu–Al mesoporous precursors have been prepared by direct synthesis using “catanionic” (mixed cationic and anionic) surfactants. The as-synthesized materials, involving a mesotructured framework composed of minor Cu hydroxynitrate domains overdispersed within the major alumina based mesophase, yielded through controlled calcination and reduction, Cu 0 particles of variable size, well dispersed and quite strongly attached on the alumina support. In each calcined sample, combined transmission electron microscopy and energy dispersive X-ray analyses revealed the presence of both very small, nanometer sized, CuO particles and of larger CuO domains, the size of which depends on the initial copper amount. The fact that each Cu hydroxynitrate domain in the as-synthesized sample yields, upon calcination and subsequent reduction, respectively the corresponding CuO domains and Cu 0 particles of about the same size and similar dispersion, reflects the regular pre-dispersion of the Cu islands during the very first synthesis stages. The (Cu,Al) mesoporous samples have been tested as catalysts for selective hydrogenation of cinnamaldehyde (CNA) and compared to classical Cu-impregnated alumina catalysts. The remarkable selectivity of the (Cu,Al) mesoporous samples towards the formation of unsaturated alcohol (hydrogenation of the carbonyl group of CNA) was attributed to the particular strong interaction of the nanometer sized Cu 0 “islets” with the Al mesoporous walls, while the conjugated CC bond is more readily hydrogenated on larger Cu 0 clusters in weaker interaction with the support.

Barrerite from Alaska was investigated by 29 Si, 27 Al and 23 Na MAS NMR both in its untreated (as-found) and heated forms. The chemical shift of the 29 Si NMR lines of the natural phase revealed the presence of three different Si( n Al) configurations. The 27 Al NMR signal of the natural phase, positioned in the region of tetrahedrally coordinated Al, becomes more shielded with increasing temperature, in agreement with the changes of the Al-O-Si bond angles caused by the distortion of the framework observed by means of X-ray diffraction (Alberti & Vezzalini, 1978). Changes in the 27 Al NMR line-width were also correlated to dehydration at high temperature. 27 Al 2D triple-quantum MAS NMR spectra were recorded on natural and dehydrated barrerite. In neither case the five tetrahedral sites could be differentiated by the MQMAS technique. 23 Na MAS spectra were preliminarily collected on the untreated barrerite and on the sample heated at 450°C and the shift of the resonance line towards higher fields in the heated phase was interpreted as a consequence of the heating process and of the increased coordination number.

The stability of MCM-41 after ion exchange and impregnation with cesium species and calcination was investigated. A pure silica and two Al-containing samples (Si/ Al ≅ 25 ), the latter synthesized either in the sodium or in the cesium form, were used as test samples. The conditions chosen for the various treatments were those usually employed to introduce basic species in zeolites or in mesoporous materials aiming at their use in catalysis. The results show that even mild basic media (pH≅8.5) can be detrimental to the stability of the structure and that impregnation with cesium acetate followed by calcination caused a severe damage to the structure. Al-containing samples were less resistant than the purely siliceous one to basic media.

This paper reports a variety of synthesis pathways leading to thermally stable mesoporous aluminum oxide phases, based on cooperative self-assembly of inorganic and surfactant species. All the mesostructured phases were obtained in aqueous media by hydrolysis and condensation of different inorganic aluminum reactants involving monomeric cations such as [Al(H 2 O) 6 ] 3+ and/or oligomeric cationic species such as Keggin aluminum clusters, in the presence of single (anionic or non-ionic) or mixed (cationic–anionic) surfactant micelles, at pH values lower than the isoelectric point of alumina, typically 8–9. Selected anionic surfactants were dodecyl sulfate or carboxylic acids, optionally admixed with small amounts of cetyltrimethylammonium bromide, while the non-ionic surfactants belong to the polyethyleneglycol–phenylether and the amine- N -oxide families. Most of the mesophases proved thermostable and exhibited a regular porous structure. Strongly depending on the synthesis and calcination conditions, their mean pore diameters vary between 8 and 60 A and their specific surface areas range between 300 and 820 m 2 g −1 .

The title compound, Mu-7, is a new layered aluminophosphate. It was obtained from a quasi-nonaqueous system involving methylformamide (MF) as solvent in addition to restricted amounts of water. MF is decomposed into methylamine during synthesis and the latter is occluded into the interlayer spacing of the material. The structure was determined by single-crystal X-ray diffraction. The symmetry is triclinic, space group P1, a = 8.368(7), b = 11.274(10), c = 11.462(12) A, α = 72.40(7), β = 89.45(8), and γ = 85.37(7)°. Mu-7 is built from zigzag ladder-type chains connected to form layers containing only four- and eight-membered rings. Mu-7 is the first lamellar aluminophosphate having such a 4 × 8 network. Characterization of the new compound by 13C, 27Al, and 31P solid-state NMR spectroscopy, bulk chemical analysis and TG/DSC is reported. A possible crystallization mechanism based on the condensation between “parent” ([AlP2O8H2]-) and zigzag ladder-type ([Al4P4O20H4]4-) chains is proposed.

A series of MFI-type metallosilicates (M=Al, Ga, Zn, Cu or their admixtures), prepared through original procedures involving direct crystallization of TPABr-containing silica gels admixed with the corresponding metallic nitrates and various mineralizing agents, has been tested as catalysts for oxidation of phenol with hydrogen peroxide in aqueous solution. The zeolites crystallized in the presence of Cu 2+ –methylamine complex proved the most active for the total organic carbon conversion and the most stable in terms of copper leaching. An optimum amount of acid sites generated by the presence of specific amounts of framework Ga or Al appeared to be a prerequisite to generate stable and active cationic copper species. The best results (78% phenol conversion, 61% total phenolic carbon conversion after 4 h on stream) were obtained so far with 0.5 g of an MFI catalyst containing 0.56 wt.% of Cu, 2 wt.% of Zn and 0.25 wt.% of Al. Our results show that phenol is mainly oxidized over the solid catalyst surface and that soluble copper in aqueous phase plays a negligible role.

The dynamics of the tetrapropylammonium (TPA) cation in the early stages of the synthesis of a siliceous MFI zeolite gel were investigated by in situ 1 H, 14 N and 29 Si nuclear magnetic resonance spectroscopy. Hydrogen bonds between the organic and water-clathrated molecules are progressively replaced by hydrophobic interactions between the organic and silica species. This feature occurs in the liquid phase of the gel (at the beginning of its preparation) and induces a considerable decrease in the dynamics of TPA. However, in the gel, the motion remains isotropic and prevents polarisation transfer from the organic protons to silicon atoms. When the first crystallites form, polarisation transfer becomes effective owing to the reduced motion of TPA within the MFI framework.

A new microporous aluminophosphate was obtained in a quasi-non-aqueous system using dimethylformamide (DMF) as solvent and templating agent. The limited amount of water is responsible for the slow hydrolysis of the Al source, yielding sodalite cages stabilized by DMF templates. The new phase has monoclinic symmetry and space group Cc. The structure of the monoclinic AlPO4-SOD is close to the sodalite structure type, with a framework composed of [4668] cages. The unit cell parameters are, respectively, a=12.94 A, b=12.47 A, c=8.63 A and β=95.77°. All the phosphorus atoms are tetracoordinated, while aluminum atoms show both tetrahedral and octahedral coordination. Upon heating, the monoclinic AlPO4-SOD is converted into AlPO4-20, which has cubic SOD topology. The bonding scheme involving water and dimethylformamide molecules linked to hexacoordinated Al atoms of the monoclinic AlPO4-SOD framework is destroyed, yielding a more relaxed cubic network.

The as-synthesized alkali-free [Ga,Al]-ZSM-5 zeolites were steamed at different steam pressures (68 kPa≤P≤92 kPa), reaction times (0 h≤t≤9 h) and temperatures (530°C≤T≤800°C). The obtained solids were characterized by XRD, FT-IR, N2 adsorption, 27 Al and 71 Ga MAS-NMR. Acidity of the solids was characterized using n-heptane cracking (T=350°C, PN2/PC7=4, P=100 kPa) as a model reaction. Acidic or bifunctional behavior of these catalysts was determined using propane aromatization (530°C, PC3=100 kPa) as a model reaction. Steaming of solids, even at low temperatures (530°C), leads to a profound and progressive demetalliation (degalliation and/or dealumination). Catalysts obtained under mild steaming conditions show for propane aromatization, properties similar to those of catalysts prepared by means of direct calcination under dry air at higher temperatures (T>700°C), or by conventional impregnation methods. Solids steamed under more severe conditions (T≥600°C or t>6 h) present a strong dealumination and total degalliation, which leads to a strongly dehydrogenating catalyst, unable for aromatization, due to a drastic decrease of the number of acidic sites present on the zeolite structure.

Gallium concentration depth profiling in various as-synthesised and post-synthesis thermally treated Ga- and (Ga,Al)-ZSM-5 zeolites was quantitatively evaluated by RBS. This technique proved for the first time that Ga-ZSM-5 synthesised in the presence of methylamine involves a homogeneous Ga framework distribution. When both Al and Ga are present in the gel precursor, they form mixed complexes with methylamine and incorporate the zeolite lattice at different rates while some unreacted Ga-amino complex overcoats the outer rim of the crystals. Gallosilicates synthesised in the fluoride medium show a fairly homogeneous Ga incorporation with an increased Ga concentration on surface due to its overcoating by residual Ga fluoro complexes. Post-synthesis thermal treatments result in a partial degalliation of the framework that could be quantified by RBS. The nature, mobility and location of the extra framework Ga species markedly depend on the calcination conditions. A rapid calcination in dry conditions leads to the formation of extra framework Ga oxides that migrate towards the crystal core. Under milder heating, these species stay homogeneously partitioned within the crystal channels. Under a humid atmosphere, the extra framework Ga species migrate towards the crystal surface, the migration being enhanced by a partial reduction of Ga during non-oxidative treatments. Humid air treatment maintains the homogeneous distribution of both Ga 2 O 3 and residual Ga 3+ framework ions.

The steaming of as-synthesized alkali-free TPA-MeNH3-[Ga0.99Al1.99]-ZSM-5 zeolite was carried out at temperatures of 530°C (St-530), 550°C (St-550), and 600°C (St-600). Physical characterization of the solids was carried out by XRD, IR, N2 adsorption, and27Al and71Ga MAS-NMR. n-Heptane cracking (T=350°C; PN2/PnC7=4; P=1 atm) was used as a model reaction to characterize the acidity of the catalysts. Propane aromatization (T=530°C; P=1 atm) was used to characterize the acid or the bifunctional behavior of solids. Results show that steaming produces less acid solids due to degalliation and dealumination of the zeolite structure. Because the presence of steam reduces the temperature at which the formation of extra framework gallium species occurs, bifunctional “Ga2O3”/H-[Ga,Al]-ZSM-5 catalysts are formed at lower temperature (T=530°C) in comparison when calcination is carried out under dry air. Catalysts are less selective to BTX as steaming temperature increases because of a strong reduction of Bronsted acid sites.

A new synthesis method for a rapid crystallization of metallosilicates called the in situ seeding method was applied to the MFI titanosilicate (TS-1) synthesis. This method, which involves the preheating of the silicate gel and the consequent generation in situ of MFI silicate (silicalite-1) seeds before the addition of Ti source, dramatically accelerated the crystallization of TS-1 in methylamine medium. Ti ions were readily incorporated into 1he zeolite framework as confirmed by IR and the unit cell expansion measured by XRD. In comparison, the classical seeding method achieved under identical conditions yielded Ti-free silicalite-1 crystals. The optimal crystallimty of the preheated silicate gel for the in situ seeding method was evaluated to ca. 5%; a lower amount of silicalite-1 seeds led to a slower crystallization of TS-1, while crystallinity over 5% resulted in the continuation of the seed growth, leading eventually to crystalline silicalite-1.

SAPO-40 exhibits five main OH species, describable as high-frequency ones (HF, at 3737, 3730, and 3724 cm-1) and low-frequency ones (LF1 and LF2, at 3559 and 3528 cm-1, respectively), the former probably sitting in 12-member-ring channels and the latter either in side pockets or eight-member-ring channels of the AFR structure. The low-temperature interaction of such OH species with CO shows that HF species have strictly similar acidity (comparable to that of HY zeolites), in contrast with previous results concerning H-transfer to NH3. The ease of interaction and the spectral features are in accord with the location in large cavities. The vibration of H-bonded hydroxyl has a noticeable structure with subbands. The interaction of CO with LF1 and LF2 species occurs with difficulty and yields nonlinear complexes because of the steric hindrance brought about by small cavities. Adsorption of N2 follows similar patterns.

New synthesis routes leading to a rapid crystallization of alkali-free MFI type borosilicates from TPA-methylamine media have been thoroughly explored. When fumed silica was used as Si source, pure MFI borosilicate crystals were obtained rapidly. They stay hydrothermally stable for 20 days at 185°C. The evaluation of framework boron by 11 B-NMR along the growth process suggests a liquid phase transportation type mechanism. Crystallization using SiCl 4 as Si source is much slower, the hydrolysis of the chloride in methylamine being the rate limiting step for the nucleation to start. Appropriate amounts of boron species markedly increase the crystallization, probably by forming readily intermediate BOSi oligomeric associations in the reaction gel. This latter partly undergoes a solid state restructuring and, along with the remaining soluble SiB oligomers, yield crystalline MFI borosilicates.

A new synthesis route leading to a rapid crystallization of boro-titano MFI type zeolites from methylamine media has been explored. The principal advantage of this synthesis method is that the use of costly ingredients such as TPAOH and Ti- and Si-alkoxides can be avoided. Ti and B are readily incorporated into the MFI framework as confirmed by spot EDX analysis, IR, 11B-NMR and XPS. Preheating the borosilicate gel before mixing with titanium tetrachloride improves the (B,Ti)-MPI crystallization rate and prevents the formation of extraframework titanium dioxides.

A new synthesis route for MFI-type titanosilicates (TS-1) using methylamine along with tetrapropylammonium bromide (TPABr), silica or silicon tetrachloride and titanium tetrachloride, thus avoiding the use of costly TPAOH and Ti-alkoxide, has been investigated. The presence of titanium ions in the reaction gel slowed down the crystallization of MFI zeolites, while addition of hydrogen fluoride as a co-mineralizer into the gel dramatically improved the crystallization kinetics. Ti was readily incorporated into the zeolite framework, as confirmed by IR, XRD (unit cell expansion), and UV-vis spectroscopy. Reduced initial amounts of methylamine in the gel led to an increase of the apparent crystallization rate of the zeolite and to a remarkable decrease of the amount of framework Ti, suggesting that high concentration of methylamine is needed for the Ti incorporation into the growing MFI crystallites.

The experimental conditions leading to the synthesis of pure and highly crystalline AlPO 4 -40, CoAPO-40, and ZnAPO-40 have been optimized. Although the preparation of these phases is favored by the presence of TMA + in the synthesis gel, these ions have not been found incorporated in the final AFR structures. All materials have been characterized by powder XRD, t.g./d.s.c, SEM, EDX, 13 C, 27 AI, and 31 P solid-state n.m.r., diffuse reflectance u.v.-vis spectroscopy, FT i.r., and catalytic tests using the m -xylene isomerization as a model reaction. This multitechnique approach provides strong evidence for the framework incorporation of cobalt and zinc. The acid sites generated by the framework insertion of cobalt and zinc are stronger than those generated by the incorporation of silicon.

The thermal and hydrothermal stability of SAPO-40 has been evaluated using the isomerization of m-xylene as model reaction. The characterization of the porosity was also studied and compared to other well known structures, namely Y zeolite, mordenite and ZSM-5. The structural changes that occur under thermal treatments influence the activity and selectivity of SAPO-40, while hydrothermal treatments do not significantly change those properties. The results confirm the high stability of SAPO-40 under thermal and hydrothermal treatments. Catalytic tests and adsorption of cyclohexane indicate that regular large side pockets or lobes exist along the main channels of SAPO-40, which create a large void volume responsible for the high rate of adsorption, high amount of adsorbed cyclohexane and the low shape selectivity in m-xylene isomerization.

FTIR, MAS 1H-NMR, and molecular graphics data are reported concerning the hydroxyl species in a series of SAPO-40 samples with variable Si contents, as well as FTIR data concerning the interaction of ammonia with the different acid sites. Up to seven types of Si(OH)Al Bronsted sites are present, mainly differing by the O−H stretching frequency. Three high-frequency bands (3637−3624 cm-1) correspond to hydroxyls located in the 12-member channels and two low-frequency bands (3559 and 3528 cm-1) to OH species in eight-member rings and side pockets of the AFR structure. Two bands at exceptionally low frequency (3485 and 3445 cm-1 ) are due to OH species interacting with silica islands. All low-frequency bands behave with temperature as H-bonded species. All types of hydroxyls form ammonium ions, the thermal decomposition of which shows some difference in acidity among the OH species. IR evidence indicates that NH4+ species interact strongly with the basic oxygen atoms of the lattice. No Lewis sites were evide...

The synthesis of [M]-ZSM-5 zeolites (M = Ga, Al, Ga + Al) in the absence of inorganic cations and with tetrapropylammonium (TPA) as a template agent and methylamine (MA) as a complexing and mobilizing agent, was carried out at 185°C, under autogenous pressure and rocking agitation, using a low reactive aerogel. The samples were characterized by XRD, i.r., SEM, and 27 Al and 71 Ga MAS n.m.r. The results show that the efficiency of the aluminum and gallium addition into the zeolite structure is almost 100%, but the morphology and the size of the crystals as well as the crystallization rate of the zeolites are modified by the chemical composition of the synthesis gel. The presence of aluminum strongly reduces the crystallization rate of metallosilicates with MFI-type structure. The higher the concentration of aluminum, the higher the decrease. This might be related to the lower stability of the aluminum monomeric species.

Thermal and hydrothermal stability of SAPO-40 were studied by X-ray powder diffraction (XRD) and magic-angle spinning nuclear magnetic resonance (MAS-NMR). For the X-ray study, the hydrothermal treatments were carried out, in situ, in a high-temperature chamber. The SAPO-40 structure shows a remarkable stability to high temperatures under both dry and humid air. At high temperatures a reorganisation of silicon occurs, but the long-range order is only lost above ca. 1000°C. Changes in the XRD pattern induced by water at room temperature are completely reversible upon re-heating at 200°C, as well as the changes in the coordination and local environments of aluminium and phosphorus observed by NMR. For silicon however, some changes, that are observed upon hydration, remain after dehydration.

A novel 3D porous metal-organic framework with 1D polarized channels was synthesized, and its adsorption properties for gas separation and chemical sensing were studied. The framework shows a preferential adsorption of CO(2) over N(2) with a selectivity of 22:1. It also exhibits a very good sensitivity to water with respect to most of the organic solvents in view of chemical sensing applications.

Three synthesis procedures leading to SAPO-40 and using tetrapropylammonium hydroxide (TPAOH) as a template have been investigated, and their reproducibility has been tested. The kinetic study of the crystallization shows that the gel composition proposed in the original patent devoted to the silicoaluminophosphates [B.M. Lok et al. , U.S. Pat. 4 440 871 (1984)] favours the co-crystallization of SAPO-5, which competes for the same organic template as SAPO-40 and forms much more rapidly. It is demonstrated that the addition of small amounts of alkali cations (Li + , Na + , K + , Cs + ) to the reaction mixture prevents the nucleation of SAPO-5. The efficiency of the procedure depends on the Si content and cation/Si ratio of the gel. An explanation is offered in terms of electrostatic interactions in the liquid phase between the alkali ions and the building units of SAPO-5. The alkali cations tend to precipitate an amorphous phase, which causes the crystallinity of the products to decrease significantly. A more efficient method, which exclusively leads to the formation of SAPO-40, is to dilute the gel while keeping the TPAOH/water ratio constant. The lower the Si content of the reaction mixture, the larger the dilution necessary to avoid the contamination of SAPO-40 with by-products.

Gallosilicate MFI-type zeolites ([Ga]-ZSM-5) were synthesized at 170°C, with autogeneous pressure and agitation. Samples were characterized by71GaMAS n.m.r., XRD, i.r., X.p.s., and chemical analysis. The influence of synthesis parameters such as theSiO2/Ga2O3,(TPA)2O/SiO2, andNa2O/SiO2 gel molar ratios on the crystallization kinetics were evaluated. Pure and highly crystalline [Ga]-ZSM-5 are formed after 20–24 h heating, independently of the gel composition, provided that traces of the template agent (tetrapropylammonium ions, TPA+) are present. Such particular behavior is related to the presence of very stable monomer gallate ions in the alkaline synthesis media that are readily incorporated in the MFI framework structure, irrespective of low oligomeric hydroxy-Al species present in similar conditions.

The dehydration of a series of VPI-5 and H3 samples, synthesized under various conditions, as well as the solid state transformation of VPI-5 to AlPO4-8 have been investigated using combined TG-DTG-DSC and high-resolution solid state31P-NMR. The TG curves show a quasi-continuous release of water, the total loss being characteristic for each sample. Complete dehydration is achieved when the samples are heated from 20°C to about 150°C at various beating rates. Besides the main dehydration effect, several weak endothermic peaks are observed. These generally non-reproducible modulated peaks, recorded at high heating rates, are presumably due to the interactions of the water molecules leaving the channels of VPI-5 with the randomly positioned fragments stemming from the destruction of the water triple helix assemblage. The non-isothermal kinetic parameters of the dehydration have been evaluated from the TG and DTG curves recorded at low heating rates.

A full Rietveld refinement, based on high-resolution synchrotron powder diffraction data, was undertaken to investigate the structural features of a pure sample of as-synthesized SAPO-40 (space group: P112 / n ; a = 21.9410 A, b = 13.6912 A, c = 14.2486 A, γ = 90.0°; chemical formula: [(Si, Al, P) 64 O 128 ]·4 TPAOH). The fine structural details have been correlated with other experimental data obtained by thermal analysis and 13 C, 27 Al and 29 Si NMR. The topology proposed previously for the AFR framework structure of SAPO-40, with 12- and 8-ring channels intersecting to form a two-dimensional system, has been confirmed. Refined atomic coordinates for both the framework atoms and the organic template (tetrapropylammonium ion) are presented. The latter is located in the 12-ring channels with the N-atom near the center of the saddle-shaped 12-ring. The terminal methyl groups of the propyl chains are quite rigidly confined in two different framework environments. The possible interaction of the template with some framework Al atoms is discussed and the heterogeneous distribution of Si throughout the structure is shown.

In situ variable temperature 31 P- and 27 Al-NMR provide choice techniques to follow the dehydration of VPI-5. Two samples were characterized by these methods. The first sample (VPI-5-A ) is transformed into AlPO 4 -8 as soon as water is removed by heating while the second one (VPI-5-B) keeps the VFI topology, even after complete dehydration. The relative stability of the structures can be interpreted in terms of lattice defect density.

The removal of water at 100 °C (or under specific conditions) from VPI-5/MCM-9 materials results in significant structural changes. The VPI-5/MCM-9 products transform into AIPO 4 -8/SAPO-8. This transformation is partially reversible and strongly depends on the evacuation and rehydration treatments, the heating rate, and probably on lattice defect concentrations. From the knowledge of the VPI-5 structure and of the structural model recently proposed for AIPO 4 -8, we have reassigned all the 31 P n.m.r. lines characterizing both materials and explained further the effect of water on the dramatic changes occurring in their 31 P and 27 Al n.m.r. spectra. 31 P and 27 Al n.m.r. have been used to investigate systematically the transformation of VPI-5 into AIPO 4 -8 and to determine which specific T sites undergo modifications. A mechanism accounting for the transformation is proposed together with a model allowing the determination of the degree of VPI-5/AIPO 4 -8 conversion by computing the relative intensities of five specific 31 P n.m.r. lines that characterize the transition intermediate structures. 31 P n.m.r. proved more sensitive than did conventional X-ray diffraction to detect short-range structural changes in these open structures.

The formation and annealing of various kinds of defects in the framework of highly siliceous MFI-type zeolites, as evidenced by high-resolution solid-state 29 Si n.m.r., can be explained by considering the systematic influence of synthesis parameters and postsynthesis treatments. High pH values and high concentrations of alkali metal and fluoride ions prevent a complete polycondensation of the silicate species and generate materials that contain significant levels of nonbonding point defects. By contrast, a high crystallization temperature results in the ready hydrolysis of the terminal Si-O − groups, leading to structures containing fewer defects. A large number of T vacancies (hydroxyl nests) are created in zeolites crystallized at low temperatures in the presence of high Pr 4 N + concentations and in the absence of F − or Na + ions. Such conditions favor the formation of double-5-ring silicate anions. The hypothesis, that such species may further condense, conducting to frameworks with an important number of empty T-sites, is proposed. On the basis of these findings, ideal synthesis conditions can be proposed to produce (Si) MFI zeolites that contain a minimum number of defects. Various postsynthesis treatments, namely, different calcination conditions followed, or preceded, by selected ionic (akali cation) exchanges, result in a partial or a nearly total healing of these defects in the final materials.

Several organic compounds favour the formation of the high-silica zeolite ZSM-48. This paper gives insight into the state of the organic molecules (1,8-diaminooctane — C8DN and hexamethonium bromide — HMBr2) occluded in the channels of ZSM-48. Combined thermal analysis and13C-NMR techniques have been used to characterize their structural state in the pore volume of the as-synthesized zeolite and their thermal stability. A decomposition scheme is proposed in each case. Both C8DN and HMBr2 are incorporated intact into the intracrystalline volume of ZSM-48 and they ensure a good pore filling of the zeolite lattice. By contrast, for the (HM)ZSM-48 synthesized in the presence of HM++ and ammonium ions, a partial decomposition of hexamethonium ions to hexyltrimethylammonium and trimethylammonium ions has been observed, the latter compounds also being occluded in ZSM-48. The progressive removal of the various organics occluded in ZSM-48 could be followed by TG—DTA and a decomposition scheme is proposed in each case.

International audience; MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn-Laplace law while, in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of sponge-like silica glasses. The results vindicate the models of Wenzel and Kloubek on the effect of surface defects on the mercury contact angle, which is significantly larger for a rough surface than for a plane surface. The surface defects of SBA-15 does not affect the evaluation of the mesopore size by nitrogen adsorption, as they are filled at an early stage of the adsorption and do not interfere with capillary condensation.

MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn−Laplace law, while in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of spongelike silica glasses. The results vindicate the models of Wenzel and Kloubek on the effect of surface defects on the mercury contact angle, which is significantly larger for a rough surface than for a plane surface. The surface defects of SBA-15 does not affect the evaluation of the mesopore size by nitrogen adsorption, as they are fi...

SAPO-34 and SAPO-11 with an increased number of acid sites were synthesized by adding methylamine (MA) as co-template to tetraethylammonium hydroxide (TEAOH) or dipropylamine (DPA) respectively currently used as true templates. Along with minor changes of the final chemical and morphological properties of the as-synthesized materials, the major role of methylamine was shown to prevent a rapid silica polymerization (or to slow down its depolymerization) in the early synthesis steps, thereby favoring the progressive framework insertion of small Si oligomers that further generate an increased number of SAPO domains, with respect to Si islands.

We report here for the first time a xenon NMR study on zeolite Nu-10, a high-silica medium-pore aluminosilicate involving a framework constructed from 5-1 secondary building units (pentasil material), with non-interconnected channels running parallel to the c-axis and formed by an elliptical (0.45×0.55 nm) 10-T-ring system

The synthesis of the pure silicoaluminophosphate SAPO-37 requires the knowledge of optimal crystallization conditions. SAPO-37 is obtained by two different methods. In synthesis of type A, a hydrogel prepared by mixing orthophosphoric acid, fumed silica, and aluminium oxide with the organic cations tetrapropylammonium (TPA + ) and tetramethylammonium (TMA + ) is aged before crystallization. In synthesis of type B, SAPO-37 is prepared from a two-liquid-phase reaction mixture containing the reactants dissolved in both a liquid organic ( n -hexanol) and an aqueous phase. The physicochemical characterization of the crystalline products prepared by these two procedures allows the proposal of a model for the distribution of Si in a hypothetical AIPO 4 framework. Si preferentially replaces P in the AIPO 4 structure. When larger amounts of silicon are introduced in the gel, Si-rich domains are created in the more siliceous product that is formed. In addition, zeolitic faujasite-type domains with Si/Al= 1.6 are also observed. The proportion of each region can be estimated by 29 Si n.m.r.