Effect of nickel promoter in Au/TS-1 catalysts for gas-phase propylene epoxidation

Au active sites on titanium silicalite are essential for the propylene epoxidation with H and O. To improve the amount of Au active sites Ni(II) as promoter was used to change the surface charge state of TS-1 support so that more Au species can be attracted to deposit on TS-1 (Au–Ni(II)/TS-1). The dispersion and the valence state of the Au and Ni species on Au-Ni(II)/TS-1 were analyzed by HAADF-STEM and XPS, respectively. Both the Au capture efficiency and the Au loading increased greatly with Ni(II) content but overmuch Au loading (0.396%) can result in the rapid agglomeration of the Au nanoparticles on the outer surface of TS-1 and lead to poor catalytic performance. So through regulating both the concentrations of Ni and Au species, the best comprehensive performance was reached on the catalyst 0.212Au0.154Ni(II)/TS-1 (0.212 wt% of Au and 0.154 wt% of Ni(II)) at 170 °C, propylene oxide (PO) formation rate of 154 gh kg, and H efficiency of 31%. The results could guide us to maximize the utilization efficiency of Au precursor and H more reasonably.