Catalytic oxidation of benzene with ozone over alumina-supported manganese oxides

Catalytic oxidation of benzene with ozone over alumina-supported manganese oxides was carried out at room temperature (295 K) to investigate the behavior of benzene oxidation and CO_x formation. The ratio of the decomposition rate for ozone to that for benzene was found to be 6, independent of ozone concentration, reaction times, and the amount of Mn loading. A linear correlation was observed for the amount of ozone decomposed and that of CO_x formed, whereas deviation from linearity was observed between the amount of ozone decomposed and that of benzene reacted. Carbon balance was in the range of 26-37% due to the formation of two types of intermediates, weakly bound compounds including formic acid and strongly bound surface formate and carboxylates. Catalyst was significantly deactivated due to the buildup of the intermediates on the catalyst surface during the course of benzene oxidation. The weakly bound compounds were removed by heat treatment at 573 K in the O₂ flow. The strongly bound surface formate and carboxylates were oxidized to CO_x by further heating up to 723 K. The deactivated catalyst was regenerated by the heat treatment.