Phosphate-Modified Effects on Uncalcined TS-1-Immobilized Au Catalysts for Propylene Epoxidation with H2 and O2

Au nanoparticle sizes, as well as surface properties and Ti species of titanosilicate zeolite, have been identified to significantly influence the performances of Au–Ti bifunctional catalysts over propylene epoxidation with H2 and O2 to propylene oxide (HOPO process). Herein, we perform a convenient and efficient strategy to simultaneously regulate the properties of Au and Ti active sites by impregnating phosphate onto the uncalcined TS-1 zeolite (i.e., TS-1-B). The optimal P-modified TS-1-B-immobilized Au catalyst shows notably increased activity by 75% compared to the pristine Au/TS-1-B catalyst with a near PO selectivity and H2 efficiency. We found that the introduction of phosphate conduces to the Au capture and formation of the smaller-sized Au nanoparticles with the smaller size over the TS-1-B zeolite, which promotes the generation of hydroperoxide species thereon and thus boosts the PO activity. Moreover, the moderate P modification could form highly active Ti species, reduce the surface defect, and enhance the Lewis acid sites over the TS-1-B zeolite, which makes for maintaining acceptable PO selectivity and H2 efficiency under a high PO formation rate. We suggested this work could help develop efficient modification methods over Au–Ti bifunctional catalysts for this reaction.