Catalytic oxidation of benzene in gas phase with ozone was carried out at 70°C over manganese oxides and manganese-based mixed oxides to investigate the effect of catalyst composition and preparation conditions on their catalytic properties. The oxides were prepared by an evaporation-to-dryness method and a co-precipitation method from metal nitrate precursors, followed by calcination at 400-900°C. As for manganese monoxides, benzene oxidation rate normalized by catalyst surface area, product distribution and ozone/benzene decomposition ratio were almost independent of the preparation method and calcination temperature. Perovskite-type mixed oxides, LaMnO3 and La0.8Sr0.2MnO3 showed much lower activity and lower efficiency for ozone utilization in benzene oxidation than manganese monoxide and La sites promoted the accumulation of less-reactive byproduct compounds on the catalysts. In the case of manganese-based mixed oxides that contained Fe, Co, Ni, and Cu, benzene oxidation activity, CO2 selectivity and ozone/benzene decomposition ratio depended on the catalyst composition and preparation conditions. Among the mixed oxide catalysts, the Co-Mn mixed oxide prepared by the evaporation-to dryness method and calcined at 400°C was the most effective for benzene oxidation from the standpoint of CO2 selectivity and efficiency for ozone utilization.
All Science Journal Classification (ASJC) codes
- General Environmental Science
- Process Chemistry and Technology