Titanium silicalite-1 zeolite encapsulating Au particles as a catalyst for vapor phase propylene epoxidation with H2/O2: a matter of Au–Ti synergic interaction

Abstract

Developing a highly effective Au–Ti catalyst with synergic interaction for vapor phase propylene epoxidation with H₂/O₂ has tremendous industrial and scientific significance. In this study, a novel zeolite encapsulated catalyst is proposed to enhance such a synergic interaction. The proposed Au–Ti@MFI catalyst is prepared via seed-directed solvent-free synthesis combined with bio-extract integration, in which the encapsulated Au nanoparticles (NPs) are anchored with the Ti site of the titanium silicalite-1 zeolite (TS-1). The as-prepared catalyst shows a simultaneously high propylene conversion of 14.8%, a PO selectivity of 83.9% and an excellent PO yield of 205.0 g_PO kg_cat⁻¹ h⁻¹, outperforming the conventional supported Au/TS-1 catalyst. The intrinsic properties for Au–Ti synergic interaction are elucidated by multiple characterizations and DFT calculations. It is found that the zeolite encapsulated structure realizes intimate contact and electronic interaction between Au and Ti, remarkably enhancing the Au–Ti synergic interaction of the catalyst. This synergy effectively facilitates the generation and transfer of hydrogen peroxide, thereby significantly promoting the performances of the catalyst.