Characterization of Silylated Ti–SiO₂ Prepared by Chemical Vapor Deposition and Its Catalytic Performance in Green Epoxidation of Soybean Oil

Silylated Ti–SiO₂ (S–Ti–SiO₂) was prepared by the chemical vapor deposition of TiCl₄ and following hexamethyldisilazane (HMDS) on SiO₂. Its specific surface area and pore size are decreased compared with Ti-SiO₂ while it keeps highly dispersed Ti species with low coordination. More importantly, S–Ti–SiO₂ possesses higher hydrophobicity than Ti-SiO₂, which can explain the fact that it performs better than Ti-SiO₂ in catalytic epoxidation of soybean oil using 30% aqueous H₂O₂ as oxidant. The relative conversion to oxirane (RCO) of S–Ti–SiO₂ can reach 27% and the catalyst can be used 3 times under the best reaction conditions.