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

Abstract

Ru nanoparticles were successfully deposited onto 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 °C and 13.5 and 19.3 MPa and further reduction in H₂/N₂ at 400 °C at low pressure, reactive deposition of Ru(tmhd)₂(COD) with H₂ in scCO₂ at 150 °C and reactive deposition of RuCl₃·xH₂O with ethanol in scCO₂ at 150 and 200 °C. 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.