Enhancement of the activity and stability of Au/TS-1 catalyst in the gas-phase epoxidation of propene through alkali carbonate modification

A serious of robust Au/TS-1 catalysts were prepared by modifying with various alkali carbonates including Na₂CO₃, K₂CO₃, Rb₂CO₃ and Cs₂CO₃ via the ultrasonic impregnation. The alkali carbonate-modified Au/TS-1 catalysts were characterized by XRD, ICP, XPS, UV-vis, FT-IR, NH₃-TPD and HAADF-STEM and their catalytic activity and stability in the gas-phase epoxidation of propene were investigated in a fixed-bed reactor in the presence of H₂ and O₂. The results indicate that the modification with alkali carbonates can decrease the surface acidity and inhibit the aggregation of Au particles; moreover, Rb₂CO₃ and Cs₂CO₃ can even reduce the content of extra-framework Ti in Rb-Au/TS-1 and Ce-Au/TS-1. The catalytic activity and stability of Au/TS-1 in the gas-phase epoxidation of propene are significantly improved after the modification with alkali carbonates. In particular, Cs₂CO₃-modified Cs-Au/TS-1 catalyst exhibits the best performance, with a propene conversion of 6.2%, selectivity of 86.2% to propene oxide (PO) and H₂ utilization efficiency of 26.2%. The results suggest that alkali carbonate modification could be a novel strategy to enhance the catalytic activity and stability of Au/TS-1 in propene epoxidation.