Effect of manganese oxides supported on zeolite Y on catalytic oxidation of benzene by ozone

Abstract

Manganese oxide catalysts with different structures and loading levels were supported on zeolite Y catalysts using a dry impregnation method for the oxidation of low concentrations of benzene with ozone. X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) studies revealed that manganese oxide was highly dispersed on the zeolite in a low oxidation state for those prepared with the acetate precursor, and highly oxidized and aggregated manganese oxide for those prepared with the nitrate precursor. In the reaction at 70 ℃, the benzene oxidation rate, CO₂ selectivity, and ozone/benzene decomposition ratio were independent of the manganese loading, manganese precursor, and zeolite Y porosity. These catalytic properties were found to be less dependent on the manganese oxide structure. A slight increase in the reaction temperature enhanced both the catalytic activity and the catalyst performance, while the presence of water vapor had no significant impact. The XAFS analysis of the spent catalysts indicated that during the benzene decomposition reaction, the structure of the manganese oxide loaded on the catalyst was altered, and its oxidation state was uniformly reduced.