High Catalytic Performance of MoO3‐Bi2SiO5/SiO2 for the Gas‐Phase Epoxidation of Propylene by Molecular Oxygen

Abstract MoO 3 ‐Bi 2 SiO 5 /SiO 2 catalysts with a Mo/Bi molar ratio of 5, prepared by a two‐step hydrothermal and simple impregnation method, were investigated for the epoxidation of propylene by O 2 and characterized by XRD, N 2 absorption–desorption isotherms, thermogravimetric analysis (TGA), temperature‐programmed reduction, NH 3 temperature‐programmed desorption (TPD), and IR, Raman, and X‐ray photoelectron spectroscopy (XPS). On MoO 3 ‐Bi 2 SiO 5 /SiO 2 with Mo/Bi=5 calcined at 723 K, a propylene conversion of 21.99 % and a propylene oxide selectivity of 55.14 % were obtained at 0.15 MPa, 673 K, and flow rates of C 3 H 6 /O 2 /N 2 =1/4/20 cm 3 min −1 . XRD, IR spectroscopy, and XPS results show that Bi 2 SiO 5 and MoO 3 are crystalline nanoparticles. NH 3 ‐TPD results indicate that the surface acid sites are necessary for the high catalytic activity. The results of TGA and N 2 absorption–desorption isotherms reveal that a reasonable calcination temperature is 723 K. The reaction mechanism of propylene epoxidation on MoO 3 ‐Bi 2 SiO 5 /SiO 2 catalysis is hypothesized to involve an allylic radical generated at the molybdenum oxide species and the activation of O 2 at the bismuth oxide cations.