Effect of preparation condition on performance of Ag–MoO 3/ZrO 2 catalyst for direct epoxidation of propylene by molecular oxygen

Abstract

The Ag–MoO 3/ZrO 2 catalyst for an epoxidation of propylene by molecular oxygen was prepared by the precipitation/impregnation method, and characterized by N 2 adsorption at low temperature, XRD, NH 3-TPD and CO 2-TPD. The effects of preparation condition of ZrO 2 support on its physicochemical properties and catalytic performance were studied. The results show that suitably low surface area, big pore size, and modest and weak surface acidity–basicity for the Ag–MoO 3/ZrO 2 catalyst are in favor of the selective formation of propylene oxide. High surface area, abundant micro-pore structure and strong acidity–basicity or acidity-free are liable to the deep oxidation of propylene to CO 2 and H 2O. As the support of the Ag–MoO 3 catalyst for an epoxidation of propylene, the monoclinic phase of ZrO 2 is preferable to tetragonal one. Suitably larger particles of Ag and highly dispersed MoO 3 on the Ag–MoO 3/ZrO 2 catalyst are beneficial to improve the selectivity to propylene oxide.