Supercritical fluid deposition of Ru nanoparticles into SiO2 SBA-15 as a sustainable method to prepare selective hydrogenation catalysts

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Ru nanoparticles were successfully deposited into mesoporous SiO2 SBA-15 using supercritical CO2 (scCO2). The use of scCO2 favoured the metal dispersion and Ru nanoparticles uniformly distributed throughout the support were obtained. Different precursors and methodologies were employed: impregnation with Ru(tmhd)2(COD) in scCO2 at 80 ºC and 13.5 and 19.3 MPa and further reduction in H2/N2 at 400 ºC at low pressure, reactive deposition of Ru(tmhd)2(COD) with H2 in scCO2 at 150 ºC and reactive deposition of RuCl3•xH2O with ethanol in scCO2 at 150 and 200 ºC. The size of the particles was limited in one dimension by the pore size of the support. The metal loading varied with the methodology and experimental conditions from 0.9 to 7.4% Ru mol. These materials exhibited remarkable catalytic activity. The Ru/SiO2 SBA-15 materials prepared by reactive deposition with H2 in scCO2 were selective catalysts for the hydrogenation reactions of benzene and limonene, allowing the production of partly hydrogenated hydrocarbons that may serve as building blocks for more complex chemicals. scCO2 is shown to be a green solvent that allows the preparation of efficient heterogeneous catalysts to design sustainable processes. Furthermore, in the hydrogenation of limonene, scCO2 was also used as the solvent.