Gas-phase epoxidation of propylene through radicals generated by silica-supported molybdenum oxide Original Research Article

It was found that silica-supported molybdenum oxide was high effective for the epoxidation of propylene among various silica-supported metal oxides. The post-catalytic bed volume played an important role in its formation. On a MoOx/SiO2 with 0.255 mmol/g-SiO2, a propylene conversion of 17.6% and a PO selectivity of 43.6% were obtained at 5 atm, 573 K and flow rates of C3H6/O2/He = 10/5/10 cm3 min−1. The characterization studies indicated that crystalline MoO3 nano-particle species was more effective for propylene epoxidation to PO than molecularly dispersed Mo oxide species. The reaction mechanism of propylene epoxidation on MoOx/SiO2 catalysts is hypothesized to involve gas-phase radicals generated at relatively low temperature by the dispersed molybdenum oxide species. These radicals participated in homogeneous reactions with molecular oxygen to produce propylene oxide.