Intracrystalline diffusion regulation of Au/hierarchical TS-1 for simultaneously enhanced stability and selectivity in propene epoxidation with H2 and O2

Abstract

Regulation of intracrystalline diffusion plays a pivotal role in ensuring the catalytic stability of metal-supported zeolite catalysts. Herein, we successfully achieved precise modulation of intracrystalline diffusion in Au-loaded hierarchical TS-1 catalysts by two-step recrystallization approach. This modulation was achieved by manipulating the length of mesoporogens, characterized by the hierarchical factor (HF). The HF could be used as the descriptor to reveal the reaction stability and deactivation process including blocking degree (V_Au: gold volume / V_na: volume not accessible for N₂) by the Au nanoparticles and coke formation in fresh and used catalysts, respectively. In addition, the enhanced selectivity was attributed to the improved hydrophobicity of Au/hierarchical TS-1 with gradually decreased terminal silanols by two-step recrystallization approach. This work not only provides the new strategy for the regulation of zeolite intracrystalline diffusion, but also could shed new lights on the industrial process of direct propene epoxidation with H₂ and O₂.