Epoxidation of Methyl Oleate and Unsaturated Fatty Acid Methyl Esters Obtained from Vegetable Source over Ti-Containing Silica Catalysts

With different oxidants (aqueous H2O2 or cumene hydroperoxide), Ti-containing silica catalysts (hierarchical TS-1, Ti-MCM-41, and Ti-HMS) were applied as catalysts for the epoxidation of methyl oleate (MO) and vegetable-derived unsaturated fatty acid methyl esters (FAMEs). We found that the catalytic performances of titanium silicalites were highly dependent on oxidant types. For the epoxidation of MO over hierarchical TS-1 (HTS-1), aqueous H2O2 is a better oxidant compared with cumene hydroperoxide (CHP). Benefiting from good molecular accessibility and high activity of Ti sites, combined with high hydrophobicity, ultra-high-yield epoxides were obtained over HTS-1. In contrast, CHP was more favorable for Ti-HMS catalyst, which was beneficial to selective conversion of MO into epoxide under solvent-free conditions. The superior catalytic performance was ascribed to the high surface area and pore volume of Ti-HMS. Furthermore, the corresponding structure–catalytic performance relationships and reusability of various catalysts were discussed in consideration of the effect of oxidants.