MCM-41 is proposed to build mesostructured Fe2O3-based sorbents as an alternative to other silica or alumina\ud
supports for mid-temperature H2S removal. MCM-41 was synthesized as micrometric (MCM41_M) and\ud
nanometric (MCM41_N) particles and impregnated through an efficient two-solvent (hexane–water)\ud
procedure to obtain the corresponding gamma-Fe2O3@MCM-41 composites. The active phase is homogeneously\ud
dispersed within the 2 nm channels in the form of ultrasmall maghemite nanoparticles assuring a high active\ud
phase reactivity. The final micrometric (Fe_MCM41_M) and nanometric (Fe_MCM41_N) composites were\ud
tested as sorbents for hydrogen sulphide removal at 300 °C and the results were compared with a reference\ud
sorbent (commercial unsupported ZnO) and an analogous silica-based sorbent (Fe_SBA15). MCM-41 based\ud
sorbents, having the highest surface areas, showed superior performances that were retained after the first\ud
sulphidation cycle. Specifically, the micrometric sorbent (Fe_MCM41_M) showed a higher SRC value than the\ud
nanometric one (Fe_MCM41_N), due to the low stability of the nanosized particles over time caused by their\ud
high reactivity. Furthermore, the low regeneration temperature (300–350 °C), besides the high removal\ud
capacity, renders MCM41-based systems an alternative class of regenerable sorbents for thermally efficient\ud
cleaning up processes in Integrated Gasification Combined Cycles (IGCC) systems
Novel heterogeneous bi-functional catalysts bearing tin or zinc inserted as single sites within the silica architecture acting as acid centres and decorated with imidazolium moieties as the nucleophile source were successfully synthesized. The materials were extensively characterized via various techniques including N 2 physisorption, solid state nuclear magnetic resonance, X-ray photoelectron spectroscopy, transmission electron microscopy and adsorption microcalorimetry. The solids were tested as catalysts for the conversion of carbon dioxide, selecting the synthesis of styrene carbonate as the target reaction.Both materials exhibited improved performances compared to the analogous solids functionalized with the sole imidazolium salt as well as to other materials reported in the literature. The Sn-based catalyst displayed excellent conversion also in the presence of various epoxides. In all experiments the bifunctional solid allowed reducing the reaction temperature below 150 C. In the presence of glycidol the temperature was decreased down to 30 C. The short synthesis protocol of the heterogeneous catalysts, together with the 100% atom economy of the target reaction and the low reaction temperature, make the entire process highly sustainable. Moreover, the Sn-based catalyst was stable under the selected reaction conditions and reusable for multiple catalytic cycles.
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