Modified impregnation combined with thermal treatment to boost Au-Ti catalytic hydro-oxidation of propylene

Abstract

Designing highly efficient Au-Ti bifunctional catalysts is pivotal to the hydro-oxidation of propylene to propylene oxide (PO). Herein, we report that the catalytic performance of Au/uncalcined TS-1 (i.e., TS-1-B) catalyst prepared via impregnation method using Na₃Au(S₂O₃)₂ as precursor can be remarkably enhanced by tuning the properties of active sites through thermal treatment. Increasing thermal treatment temperature favors the decomposition of sulfur species adsorbed on the surface of Au nanoparticles and the TPA⁺ templates adsorbed on the external surface of the catalyst, thereby exposing more Au and Ti sites, while the dispersion of Au particles and surface hydrophobicity are inferior at elevated thermal treatment temperature. Consequently, PO formation rate exhibits a volcano-shaped relationship with thermal treatment temperature. Importantly, the as-obtained 0.035 wt% Au/TS-1-B catalyst displays a hydrogen efficiency of up 62 % in addition to promising PO selectivity (95 %) and PO formation rate (155 g_PO·h⁻¹·kg_cat^-1) with no significant decline over 140 h.