Tailoring titanium species to boost bifunctional Au-TS-1 catalyzing propylene hydro-oxidation

Abstract

The speciation of titanium is a crucial factor that influences the catalytic activity of TS-1, an efficient catalyst for selective oxidations. This study investigates how different thermal treatment conditions affect titanium speciation in TS-1. A variety of characterization techniques were employed to identify changes in the titanium speciation, while propylene hydro-oxidation served as a probe reaction to assess the impact of these changes on the synergistic interaction between TS-1 and Au nanoparticles. Our findings reveal that conventional thermal calcination induces a transformation of some titanium species from tetrahedral coordination Ti⁴⁺ to extra-framework anatase TiO₂. In contrast, thermal treatment under an inert nitrogen atmosphere at lower temperatures effectively mitigates this transformation, resulting in a reduced amount of extra-framework TiO₂. This optimization leads to enhanced utilization of H₂O₂ and decreased isomerization conversion of propylene oxide, ultimately boosts bifunctional Au-TS-1 catalyzing propylene hydro-oxidation.