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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.

Nanometric Fe2O3 particles could be inserted inside the internal pore volume of SBA-15 mesoporous silica and mesoporous alumina supports, when Fe(III) chelates (EDTA, gluconate or citrate) were used as impregnating precursors. The oxidative degradation of the chelating anions was followed by combined TG-DTA. Strong chelate-SiOH interactions (case of bulky EDTA), favored by the mesopore curvature, yield sub-nanometric extremely well dispersed Fe2O3 particles preferentially located at the micropore mouths (confinement effect). Fe2O3 even more strongly interacts with alumina walls, generating either (Fe,Al)2O3 mixed phases or Fe-aluminate micro domains. These iron-based mesoporous alumina composites proved very active catalysts in total oxidation of phenol at ambient conditions, with extremely low iron leaching (0.2%).

As an extension of a study to generate ceramic-metal nanosized composites further deposited on ceramic foams, here we describe a new route to prepare Pt–TiO2 nanopowders of controlled metallic size and their further coating of TiO2 foams. Their efficiency as catalysts in volatile organic compound elimination (deVOC) reactions was evaluated and compared to those of the corresponding classical unsupported mixed powders. Composite metal/ceramic nanopowders (Pt–TiO2) were synthesized by laser pyrolysis using organo-metallic precursors. Successive dip-coatings on TiO2 foams with aqueous slurries of nanodispersed Pt–TiO2 particles were then achieved. Both foam-supported and unsupported Pt–TiO2 grains of about 20 nm could be stabilized, confirming no significant particles coalescence after a thermal treatment at 460 °C. Both proved equally efficient catalysts for the total oxidation of methanol, selected as probe deVOC reaction, thereby demonstrating that the dispersion of the nanopowders over the preformed ceramics does not modify their catalytic performances.

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).

A mesoporous siliceous material of MCM-41 type was characterized by nitrogen adsorption, X-ray diffraction, and Fourier transform infrared spectroscopy. Its pore diameter, external and internal surface, pore volume, wall thickness, and pore wall density were determined. Special attention was paid to sample aging and its stability toward temperature, water vapor, and mechanical compression, aiming at using this material in industrial applications such as adsorption or catalysis. Calcined MCM-41 loses an important part of its mesoporosity during aging under ambient temperature, pressure, and humidity conditions but then becomes stable after 3 months, still retaining a noticeable porosity. The aged MCM-41 can withstand temperatures up to 873 K and uniaxial compressions up to 100 MPa without too much damage. After contact with water vapor at 358 K, the porous structure was totally destroyed and an amorphous phase was obtained.

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.

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.

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.

Various mesoporous silicas and the corresponding aluminosilicates or gallosilicates have been synthesized using a series of literature or `home made' recipes. The efficiency of Al or Ga incorporation in the siliceous walls of these materials depends markedly on the trivalent source and the evolution (ageing) of the so-formed Si-MIII gel-type phases at different starting pH values and temperatures, after adding the surfactant-structuring compounds. Crystallization at low temperature (e.g. < 373 K) yielded mesoporous compounds with hexagonal topology (MCM-41 type), involving double-layered Si walls possibly partly substituted by Al or Ga. Such structures remain stable after calcination in air at 873 K. When the same gels are crystallized at 423 K for 2 d, lamellar frameworks (MCM-50 type) are preferentially stabilized. They readily collapse on heating. The ultra-small-angle X-ray scattering (USAXS) data and the first part of the SAXS data show a power behaviour that indicates a fractal interface before calcination. After calcination, in the case of MCM-50 type materials, the fractal dimension significantly increases, the fractality region being larger than in the precursor. By contrast, in the case of MCM-41 type materials, the fractal region tends to disappear after calcination. The second part of the SAXS curve reflects the hexagonal or lamellar structure. Some precursors simultaneously exhibit both structures. The hexagonal parameter ranges from 4.6 to 5.8 nm, while the thickness of the wall is estimated to be of the order of 0.7 nm from observations of the satellite peaks in the vicinity of the successive peaks characterizing the hexagonal array. The successive peaks relative to the lamellar structure are consistent with the superposition of two or three layers, the thickness of which are of the order of 3.3, 2.85 and 2.5 nm. Predominant hexagonal structures are maintained after calcination while lamellar structures collapse during calcination. In the case of hexagonal structure, the hexagonal array is slightly contracted.

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.

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.

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...

Nanometric Fe(III) oxide particles could be inserted inside the internal pore volume of SBA-15 mesoporous silica when Fe(III) chelates (EDTA, gluconate and citrate-NH4) were used as impregnating precursors. Fe(III) nitrate preferentially yields 8 nm uniformly sized Fe2O3 clusters that selectively plug the SBA-15 channels. The control of the size and dispersion of the Fe2O3 particles generated after subsequent oxidative degradation of the chelates was shown to be dependent of the nature (geometry) of the complex used, that preferentially interacts with the SBA-15 internal walls that exhibit a high curvature (confinement effect). Cyclic voltammetry along with TPR, was used to evaluate the redox properties of Fe(III) species in the final composites, arguing in all cases for a partial reduction of Fe2O3 to FeO and for a strong interaction with the silica support of the very small Fe2O3 particles resulting from the decomposition of Fe-EDTA.

Binary Cu-Al mesoporous phases prepared by direct synthesis proved particularly selective (up to 76%) in the hydrogenation of conjugated unsaturated carbonyl compounds (cinnamaldehyde) into the corresponding alcohol. This is due to the presence of a large number of (sub)nanometer sized Cu2O particles, well dispersed and probably in strong interaction with the mesoporous alumina walls. However, all the calcined and reduced phases also involve larger CuO and Cuo particles respectively. A systematic study of various synthesis parameters, such as the order of addition of the reactants, the final pH of the medium and the nature of the copper salt, allowed us to modulate the relative amounts of both sub-nanometric and larger oxidic or metallic particles, along with their degree of dispersion. The dual small size and excellent dispersion of the sub-nanometric particles were shown to be the key properties to control for the efficient use of such systems in hydrogenation reactions.

The texturing process of Bi–Sr–Ca(Dy)–Cu–O (2212) is optimized by sintering under a magnetic field. The precursor crystalline powder is melted and grown under a 1.2 T magnetic field. Textured samples are characterized by x‐ray diffraction, scanning electron microscopy, electrical resistivity, and magnetic susceptibility.

Publisher Summary This chapter discusses the stabilization of uniformly sized and dispersed copper particles in new copper (Cu)–zinc (Zn)–aluminum (Al) mesoporous catalysts. A series of binary Cu–Al and ternary Cu–Zn–A1 surfactant assisted mesoporous precursors prepared through direct synthesis yield after calcination and reduction, both Cu o and cuprous oxide (Cu 2 O) clusters of variable size, well dispersed on the mesoporous alumina substrate. These materials prove, particularly selective in the hydrogenation of the carbonyl group of cinnamaldehyde because of the presence of a large number of nanometer sized Cu 2 O particles that stay uniformly dispersed and in strong interaction with the Al mesoporous walls. In the ternary Cu–Zn–A1 mesoporous systems, ZnO exerts a major influence on the catalytic performance of such catalysts. Experimental evidence of a Cu 2 O/zinc oxide (ZnO) synergetic interaction is presented.

Selected binary Cu−Al mesoporous precursors prepared through direct synthesis yielded through controlled calcination and reduction, Cu° clusters of variable size, well dispersed on the interface of the alumina mesophase support. Small, nanometer sized Cu° particles in strong interaction with the Al mesoporous walls very selectively favor the hydrogenation of the carbonyl group of cinnamaldehyde at the expense of the conjugated C=C bond that is more readily hydrogenated on larger Cu° clusters in weak interaction with the support. Neither the (residual) internal pore volume of the Al-rich binary mesophase, nor even the its total (external and internal) surface area are influencing this selectivity, thereby confirming that this latter is basically due to the particular electronic configuration of the small copper particles.

Summary Various mesoporous silicas and the corresponding alumino- or gallosilicates have been synthesized using a series of literature or home made recipes. The efficiency of the Al or Ga incorporation markedly depends on the trivalent source and the evolution (aging) of the so formed Si-M(III) gel-type phases at different starting pH values, prior to the addition of the surfactant-structuring compounds. Low temperature (e.g. 29 Si-NMR data), eventually partly substituted for by Al or Ga, ( 27 Al- and 71 Ga-NMR). Such structures do remain stable after calcination in air at 600°C (TG-DSC and sorption data). The calcination either results in the expulsion of the (too voluminous) Ga(III) ions from the framework, or to a structural rearrangement of the remaining Al species. The resulting solids still exhibit quite strong Bronsted type acidic sites (NH 3 -TPD data). When the same gels are crystallized at 150°C fro 2 days, lamellar frameworks (MCM-50 type) are preferentially stabilized. They readily collapse upon heating but the final amorphous phase still involves both Al and/or Ga cationic (acidic) species randomly distributed in various structural environments. Small-angle X-ray scattering (SAXS) proved to be the choice method to unambiguously identify different topologies. The actual roughness (smoothness) of the various as-synthesized or calcined phases could be directly related to the fractal dimension derived from SAXS spectra. The presence of peaks at very small diffraction angles allowed us to estimate that the channel lengths of the thermally stable mesoporous materials essentially extend in the 150–200 nm range.

A new synthesis route leading to a rapid crystallization of alkali-free gallo-, alumino-, or gallo-alumino MFI-type zeolites from methylamine-Pr4N+ media, was proposed. Methylamine plays a similar mobilizing-complexing role towards both Al3+ and Ga3+ ions so that they are quasi-homogeneously distributed in the final zeolite lattice. Mild (hydro)thermal treatments of the as-synthesized materials directly yield the protonated forms involving quite strong Bronsted acid sites. While the Al species remain stable in the framework, gallium is partly extracted from the lattice upon these treatments. The framework Ga stability appears to be markedly dependant on the actual lattice Al concentrations

The different stages of SAPO-37 crystallization have been characterized by NMR of 129 Xe adsorbed on a series of intermediate phases isolated during synthesis. The nucleation of SAPO-37 occurs within the amorphous phase; the gel then undergoes a preliminary structuration through the formation of large cavities during the aging period. Upon heating at 200°C, the gel transforms into well-defined crystals of SAPO-37. The crystallinity increases with the synthesis time and reaches a maximum after 32h. For longer synthesis times, a crystalline side-phase, SAPO-40, develops in the liquid phase. SAPO-40 has a narrower pore structure than SAPO-37, possibly limited by 12 T puckered rings.

A series of intermediate phases, isolated during the synthesis of SAPO-37, have been characterized by XRD, SEM, NMR of adsorbed Xe, and solid state 27 Al- and 31 P-NMR, in order to evidence the successive steps occurring during the crystallization process. SAPO-37 stems from a direct gel restructuration: large cavities form in the amorphous phase during the aging period at ambient temperature. Upon heating at 200°C, aluminum and phosphorus respectively incorporate in configurations Al(4P) and P(4Al) in the framework, at the expense of the amorphous phase, giving rise to the formation of well-defined SAPO-37 crystals, showing an octahedral morphology, and growing with time. The crystallinity reaches a maximum after 32h. For excessive synthesis times (149h), the appearing of structural defects observed by NMR illustrates the partial degradation of the SAPO-37 framework, whereas a side-phase, SAPO-40, possibly involving interconnected channels limited by 12T puckered rings, co-crystallizes from the mother liquid phase.

Different preparation routes of the high critical temperature superconducting YBa 2 Cu 3 O 6.5+x material from solid reactant powders Y 2 O 3 , BaCO 3 and CuO have been explored. Portions of precursor were heated/annealed/cooled under various atmospheres (O 2 , air, N 2 , …) and the resulting solid intermediate or final phases characterized by X-ray diffraction and bulk analysis (PIXE). Results of long and short heat treatments confirm the importance of the oxygen stoichiometry and then O 2 partial pressure in order to obtain a superconducting phase. The basic reactions were quantitatively studied performing repeated short thermal treatments (heating/cooling cycles) of the same precursor and collecting thermogravimetric and differential thermal analysis data. On heating, the orthorhombic-tetragonal phase transition of YBa 2 Cu 3 O 6.5+x is found as a first endotherm at 850°C, not accompanied by any weight variation. Upon cooling the corresponding exotherm is seen at 765°C. The high temperature stabilized tetragonal phase reversibly loses oxygen in a series of sharp steps (DTA) at selected temperatures.

Nuclear probes using energetic (MeV range) charged particle irradiation and prompt detection of atomic and nuclear signals are powerful tools to determine quickly and accurately the chemical constituants of YBaCuO superconductors. PIXE in milliprobe geometry is used to determine the actual concentration ratios of Y/Ba and Cu/Ba, with an accuracy of 3% or better. Calculated matrix effects in the detection of characteristic K X-rays allow accurate determinations even when the composition of samples are very different from reference materials. RBS of 2 MeV α-particles is used to certify the homogeneity of the Y-Ba-Cu composition without reference material to a thickness of 250 μg/cm2 under the surface. Deuteron microbeam irradiation leads to simultaneous composition maps of all the elements (YBaCuO) in volume of 5 × 5 × 5 μm using X-rays and protons as identification signals.

Important reaction variables which affect the hydrothermal synthesis of ZSM-5 zeolites are reviewed. Nucleation and growth mechanisms of these materials are strongly dependent on the nature and concentration of the Al- and Si-bearing reactants, pH, and the type of autoclave used. The resulting ZSM-5 particles exhibit specific sizes and morphologies desired for various catalytic applications: large single crystals having a Si-rich core and an Al-enriched outer surface or polycrystalline aggregates composed of small and homogeneous particles. A close control of these variables enables the formation of a submicrocrystalline material, possibly ZSM-5-like, embedded in an Al-rich aluminosilicate gel phase. The major role of OH − species in controlling the formation of stable nuclei is emphasized. The competitive interaction between various alkali and organic cations with (alumino)silicate anionic species in the initial hydrogel affects the kinetics of crystallization, the product morphology, the particle size, and the Al radial distribution. In addition to zoning, for a given synthesis, the Si Al ratio of different crystallites increases with their particle size.

Aluminosilicate gels heated in Pyrex autoclaves yield crystalline ZSM-5 materials containing BO 4 units incorporated in the tetrahedral sites of their framework. These BO 4 groups are accurately characterized by a narrow HRMAS 11 B-NMR resonance different from the one corresponding to tetrahedral BO 4 units randomly distributed in the precursor gel. The variation of the relative intensity of these two lines is quantitatively related to the % of crystallinity of each intermediate phase. The final crystalline ZSM-5 may contain up to 0.15 (synthesis of type A) or 0.8 to 1.3 (synthesis of type B) framework boron atoms per unit cell. The boron concentration gradient within a growing crystallite can be evaluated and correlated to the mechanism that governs the nucleation and growth of ZSM-5 prepared from each procedure.

Solid intermediate phases obtained from amorphous aluminosilicate gels during mordenite crystallization have been characterized by multinuclear solid-state NMR spectroscopy. The progressive reorganization of the amorphous gel into the crystalline ordered zeolitic phase has been detected by high resolution magic-angle-spinning (HRMAS) solid state 29Si-NMR. Broad band solid state 27Al and 23Na-NMR were used to follow the incorporation of Al- and Na-atoms into the mordenite lattice and channels. An evidence of aluminium gradient in the crystallites is obtained from the comparison between surface and bulk analysis methods.

Mordenite is synthesized from different aluminosilicate gels in sealed pyrex tubes at 165°C. Its crystallization domain is established for these conditions and the coexisting phases are identified. Differences with published data are explained assuming partial dissolution of the silica-rich pyrex glass. Morphologies and composition of the mordenite crystallites are related to the molar ratios of the reactants. In addition, the composition range of mordenite and the structure of coexisting phases (analcite, gismondine, silica polymorphs…) give information about the nature of some probable mordenite precursor species: single four-membered rings and single six-membered rings.

The crystallization of the silicoaluminophosphate SAPO-37 has been achieved in two different synthesis media: a single aqueous liquid phase reaction mixture and a two-liquid phase synthesis system. This work analyses the influence of the synthesis conditions (ageing time and temperature, stirring, crystallization time) on the nature and properties (purity, crystallinity, size) of the materials which are formed.

The structure of various natural and synthetic zeolites was investigated by high resolution magic-angle-spinning (HRMAS) solid state 29Si-NMR spectroscopy. The NMR analysis is based on the great sensitivity of the 29Si-chemical shifts either on the chemical environment (i.e. the number of aluminium atoms in the second coordination shell of silicon), on the crystal symmetry (i.e. the number of crystallographically different sites) or on local strains in the crystal.