Ti-sites environment-mediated hierarchical TS-1 catalyzing the solvent-free epoxidation: The remarkably promoting role of alcohol modification

The solvent-free epoxidation of vegetable oils-derived compounds is in great demand due to its green initiative and economic efficiency. Herein, we showcase a persuasive strategy for functionalizing hierarchical TS-1 (HTS-1) with alcohol to achieve remarkably enhanced catalytic activity and selectivity of methyl oleate (MO) epoxide with H2O2 as an oxidant. The effects of alcohol types, treatment temperature and time on the catalytic performance of modified HTS-1 were investigated. The functionalization of HTS-1 with ethanol was proven to be more beneficial to enhance catalytic performance than methanol and steric effect should be taken into account when using bulkier alcohol such as isopropanol. The optimal catalytic property was achieved over ethanol-functionalized HTS-1 through a facile treatment procedure (ambient temperature, 10 h). As a result, the MO conversion could reach as high as 92.7%, overwhelming that afforded by pristine HTS-1 (only 56.9%). This strategy unfolds the following multiple merits: (i) reducing non-framework Ti species and creating accessible channel for MO diffusion; (ii) increasing hydrophobicity of catalyst accompanied by the defect-mending; (iii) elevating electrophilicity of Ti active sites to obtain more electrophilic O as the active oxygen-donating species. Such merits are responsible for significantly improved catalytic activities of HTS-1.