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The chemistry of silica-based materials, including zeolites, is strongly influenced by the nature and number of their silanols.

International audience; The current energy transition presents many technological challenges, such as the development of highly stable catalysts. Herein, we report a novel "top-down" synthesis approach for preparation of a single-site Mo-containing nanosized ZSM-5 zeolite possessing atomically dispersed framework-molybdenum homogenously distributed through the zeolite crystals. The introduction of Mo heals most of the native point defects in the zeolite structure resulting in an extremely stable material. The important features of this single-site Mo-containing ZSM-5 zeolite are provided by an in-depth spectroscopic and microscopic analysis. The material demonstrates superior thermal (up to 1000 °C), hydrothermal (steaming), and catalytic (converting methane to hydrogen and higher hydrocarbons) stability, maintaining the atomically disperse Mo, structural integrity of the zeolite, and preventing the formation of silanols.

n-Hexadecane hydroconversion has been investigated in a series of bifunctionnal metal/acid catalysts featuring distinct well-defined pore architectures. The acidic components were prepared from dealuminated Y zeolites with Si/Al of 15 and 30 post treated in alkaline medium to generate ordered or non-ordered secondary networks of mesopores and from aluminated ordered mesoporous materials MCM-41, MCM-48, KIT-6 type materials and amorphous silica gel. Activity relates linearly to the strength and number of strong Brönsted acid sites, while selectivity, more precisely the yield in isomerization products, scales directly with the mesopore volume of the catalyst. The architecture of the mesoporous network, namely the ordering, interconnectivity, homogeneity of the mesopores, affects little catalytst behavior. Confrontation of catalytic data with diffusion measurements suggests the existence of an optimal mesopore size above which the number of strong Brönsted sites and the mesopore volume are the only parameters governing catalytic performance.

International audience; Direct evidence of the successful incorporation of atomically dispersed molybdenum (Mo) atoms into the framework of nanosized MFI zeolite is demonstrated for the first time. Homogeneous distribution of Mo with a size of 0.05 nm is observed by scanning transmission electron microscopy high-angle annular dark-field imaging (STEM-HAADF). 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) and Fourier-transform infrared (FT-IR) spectroscopy, using trimethylphosphine oxide (TMPO) and deuterated acetonitrile as probe molecules, reveal a homogeneous distribution of Mo in the framework of MFI nanozeolite, and the presence of Lewis acidity. 31P MAS NMR using TMPO shows probe molecules interacting with isolated Mo atoms in the framework, and physisorbed probe molecules in the zeolite channels. Moreover, 2D 31P–31P MAS radio frequency-driven recoupling NMR indicates the presence of one type of Mo species in different crystallographic positions in the MFI framework. The substitution of framework Si by Mo significantly reduces the silanol defect content, making the resulting zeolite highly hydrophobic. In addition, the insertion of Mo into the MFI structure induces a symmetry lowering, from orthorhombic (Pnma), typical of high silica MFI, to monoclinic (P21/n), as well as an expansion of unit cell volume. The novel material opens many opportunities of catalysts design for application in mature and emerging fields

International audience; A methodology for determining the micropore, mesopore, and external surface areas of hierarchical microporous/mesoporous materials from N2 adsorption isotherms at 77 K is described. For FAU-Y zeolites, the microporous surface area calculated using the Rouquerol criterion and the Brunauer–Emmett–Teller (BET) equation is in accord with the geometrical surface determined by the chord length distribution method. Therefore, BET surface area (SBET) is the well representative of micropore surface areas of microporous materials and of total surface area of microporous/mesoporous materials. Mechanical mixtures of mesoporous MCM-41 and microporous FAU-Y powders of known surface areas were used to calculate the respective surface areas by weighted linear combination and the results were compared to the values obtained by the t-plot method. The first slope of the t-plot determined the mesopore and external surface areas (Smes+ext). The linear fit of the first slope is in general in the range 0.01 < p/p0 < 0.17 and contains the volumes and relative pressures at which all micropores are filled (p/p0 > 0.10). Overestimation of Smes+ext values was evident and appropriate corrections were provided. External surface areas (Sext) were obtained from the second slope of the t-plot, without noting an overestimation of Sext, thus allowing the determination of mesopore surface areas (Smes) by difference. Micropore surface areas were calculated by subtracting Smes+ext from the total surface area, SBET. As an example, this methodology was applied to characterize a family of hierarchical microporous/mesoporous FAU-Y (FAUmes) synthesized from H-FAU-Y (H-Y, Si/Al = 15) using C18TAB as the surfactant and different NaOH/Si ratios (0.05 < NaOH/Si < 0.25). By increasing the NaOH/Si ratio in the synthesis of FAUmes, it was shown that as the micropore surface area decreases, the mesopore surface area increases, whereas the micropore and mesopore surface area remains constant. This methodology allows accurate characterization of the surface areas of microporous/mesoporous materials.

Mn–Na–W silica supported catalysts are highly selective toward ethylene and ethane in the oxidative coupling of methane (OCM) process. However, they present lower activities than La/Sr/CaO catalysts and subsequently a lower ethylene productivity. Optimisation of the Mn–Na–W catalysts has been focused within the range of 2–8 wt% of active elements relative to the support, while silica is partially converted into inert cristobalite. This study focused on the increase of the activity of Mn–Na–W catalysts while maintaining their intrinsically high C 2 selectivity. The increase in the concentration of the active elements with respect to the support revealed that the improvement of the catalyst activity was possible but limited. A high concentration of Mn–Na–W favours the formation of a smooth cristobalite phase and strongly decreased the number of active sites. The silica support was replaced by silica-free supports to limit the formation of cristobalite. The use of SiC as a support led to the formation of cristobalite near the surface of the catalysts but the porous SiC skeleton, which remained non-oxidised at the core of the catalysts, allowed maintaining a high surface area. SiC supported catalysts thus presented higher activities than silica catalysts. The use of α-alumina support led to catalysts with lower performances and revealed that exposed alumina was detrimental for the catalyst performance.

International audience; The texture of mesoporous FAU-Y (FAUmes) prepared by surfactant-templating in basic media is a subject of debate. It is proposed that mesoporous FAU-Y consists of: (1) ordered mesoporous zeolite networks formed by a surfactant-assisted zeolite rearrangement process involving local dissolution and reconstruction of the crystalline framework, and (2) ordered mesoporous amorphous phases as Al-MCM-41, which coexist with zeolite nanodomains obtained by a dissolution-reassembly process. By the present systematic study, performed with FAU-Y (Si/Al = 15) in the presence of octadecyltrimethylammonium bromide and 0 < NaOH/Si ratio < 0.25 at 115 °C for 20 h, we demonstrate that mesoporous FAU zeolites consist, in fact, of a complex family of materials with textural features strongly impacted by the experimental conditions. Two main families have been disclosed: (1) for 0.0625 < NaOH/Si < 0.10, FAUmes are ordered mesoporous materials with zeolite walls, which coexist with zeolite nanodomains (100–200 nm) and (2) for 0.125 < NaOH/Si < 0.25, FAUmes are ordered mesoporous materials with amorphous walls as Al-MCM-41, which coexist with zeolite nanodomains (5–100 nm). The zeolite nanodomains decrease in size with the increase of NaOH/Si ratio. Increasing NaOH/Si ratio leads to an increase of mesopore volume, while the total surface area remains constant, and to a decrease of strong acidity in line with the decrease of micropore volume. The ordered mesoporous materials with zeolite walls feature the highest acidity strength. The ordered mesoporous materials with amorphous walls present additional large pores (50–200 nm), which increase in size and amount with the increase of NaOH/Si ratio. This alkaline treatment of FAU-Y represents a way to obtain ordered mesoporous materials with zeolite walls with high mesopore volume for NaOH/Si = 0.10 and a new way to synthesize mesoporous Al-MCM-41 materials containing extralarge pores (50–200 nm) ideal for optimal diffusion (NaOH/Si = 0.25).

Here, we report a new, one-pot method to prepare a highly active and yet selective as well as stable acidic micro-mesoporous zeolite catalyst composite for the conversion of bulky substrates (acetylisation of aldehydes). The process involves generating highly dispersed zeolitic sheets (ITQ-2) inside the synthesis gel of a mesoporous host structure (siliceous TUD-1) by the in-situ delamination of the zeolite MCM-22(P).

In this contribution we describe the use of heterogeneous catalysts for the liquid-phase self-metathesis of 1-octene in supercritical CO2. Our work aims at addressing the mass-transfer problems associated with such reaction systems. By coupling a heterogeneous supported Re2O7 catalyst with the use of scCO2, the self-metathesis of 1-octene takes place by and large much more rapidly than in traditional solvent media, and furthermore, by using scCO2 the overall efficiency and sustainability of the transformation can be improved.

The title compound, [Co(C6H15NO3)2](CH3CO2)2, contains two triethanolamine ligands bound to a Co2+ metal centre, which lies on a crystallographic inversion site such that the asymmetric unit contains half of the cation and one acetate anion. The triethanolamine ligands coordinate via each axial N and two of the three O atoms, while the third arm of the ligand is pendant with the hydroxyl group pointing away from the metal centre. The acetate anions are hydrogen bonded to the coordinated hydroxyl groups and also to the free arm, forming a two-dimensional sheet-like motif.

SSCI-VIDE+ING:+SLI:CAQ:LGU:ATU:YSC:DFA; International audience; The selective oxidation of CO over C3H6 is achieved in yolk-shell Pt@Silicalite-1 catalysts in which Pt nanopartides are encapsulated in hollow silicalite-1 single crystals. The thin shell operates as a permselective membrane which limits Pt surface poisoning by C3H6. From adsorption measurements, we condude that the catalytic selectivity arises from the fastest diffusion of CO over C3H6 through the silicalite-1 membrane.

MATERIAUX:INGENIERIE:SURFACES+LBU:CAQ:ATU:FMO:JRO:DFA; We report an original and scalable synthesis pathway to produce encapsulated gold nanoparticles. Precise control of the gold particles is achieved in the range of 1-10 nm through the impregnation of silicalite-1 with a controlled concentration of gold solution, followed by dissolution-recrystallization of the zeolite.

INGENIERIE+SAG:CAQ:JEC:DFA; We report two new microporous mixed-metal triazolate based MOFs made from zinc and nickel salts combined with either 1,2,4-triazole or 3,5-diamino-1,2,4-triazole. Their structures, refined from X-ray powder diffraction, their CO2 adsorption and photoluminescent properties show a direct correlation with the structure of their parent organic ligand.

Publisher Summary This chapter showcases the versatility of the TUD-1 mesoporous oxide family as a catalyst/drug carrier, anion-exchanger, and donor material to micro-mesoporous composites. MCM-41 material exhibits a regular, hexagonal arrangement of pores (P6mm symmetry) with one-dimensional parallel channels, formed as a result of liquid crystal templating. Early examples of these mesoporous materials exhibited low hydrothermal stability, thin walls, the use of an expensive template, and the one-dimensional pore arrangement. Thus, much work has been targeted at either the improvement of these materials or the synthesis of novel mesoporous materials. A novel, next-generation, mesoporous material set out to improve the short-comings of MCM-41 is TUD-1, first reported in 2001. TUD-1 is one recent development whereby a non-surfactant organic compound (triethanolamine) templates the formation of mesoporous oxides. Transition metals varying from atomically dispersed isolated centers to nanoparticulate oxides are incorporated easily and controllably in a one-pot synthesis mixture, and have shown considerable catalytic performance when evaluated in various reaction types. In addition to the advantage of higher hydrothermal stability and three-dimensional arrangement of pores, the structure directing agent, TEA, is inexpensive and the material allows for a tunable pore size. Various metal-incorporated TUD-1 materials are easily synthesized in a one-pot synthesis gel, and the synthesis can be tuned to result in atomic dispersion of the desired metal in the framework, or the formation of stable metal oxide nanoparticles. TUD-1's ease of synthesis (even complex systems can be made in a “one-pot approach”) and the controllability of its compositional and structural details mean that it may serve as a very useful material for many current and future applications.