Study on the direct gas phase epoxidation of propylene over Ag-MoO3/ZrO2 catalyst by in situ FT-IR

The Ag-MoO3/ZrO2 catalyst for the direct gas phase epoxidation of propylene was prepared. The in situ Fr-IR technology was employed to study the adsorption and reaction behavior of propylene, propylene oxide (PO) and the mixture gas of propylene and oxygen on the surface of ZrO2 support and Ag-MoO3/ZrO2 catalyst. The studies show that propylene adsorbed on ZrO2 support or 20%Ag-4%MoO3/ZrO2 catalyst is stable. When the reaction temperature is more than 400 degrees C, the ring-opening reaction of propylene oxide adsorbed on ZrO2 support happens; over the 20%Ag-4%MoO3/ZrO2 catalyst, the ring-opening reaction of adsorbed propylene oxide occurs at 300 degrees C. As the reaction temperature rises to 400 degrees C, propylene adsorbed reacts with oxygen adsorbed on ZrO2 support to form water and CO2; over the 20%Ag-4%MoO3/ZrO2 catalyst, this surface reaction just takes place at 350 degrees C. Comparing with the unsupported Ag-MoO3 catalyst, the presence of ZrO2 support can increase the selectivity of PO and while decrease the conversion of propylene.