Catalytic ozonation of toluene and dichloromethane mixture at low temperatures over modified MnOx-based catalyst

Catalytic ozonation is an efficient method for VOCs abatement at low temperatures, in which the rational design of highly active heterogeneous catalysts constitutes the most significant step. In this study, Al2O3 was first optimized by loading MnOx. And then K was used for modifying MnOx/Al2O3 catalyst, which exhibited 2.4 × 10−3 mol∙g−1∙s−1 oxidation rate for dichloromethane and toluene oxidation with ca. 0.89 ppm ozone detected at 80 °C. That could be directly applied for removing toluene and dichloromethane mixture or coupled with other treatment technologies (such as biological purification). Besides, appropriate K doping could increase the amount of reactive surface oxygen species and the ratio of Mn2+, hence contributing to an enhanced oxidation ability. By contrast, an excess K doping inevitably lowered the activity of active surface oxygen species and interfered with the transformation of Mn3+ to Mn2+, which resulted in a weakened oxidative ability and thus a decreased catalytic activity. Finally, the reaction mechanisms over 0.1 K-MnOx/Al2O3 were tried to be demonstrated that the degradation of toluene mainly followed the pathway of toluene – phenylcarbinol – benzaldehyde – benzoic acid – phenyl group – small-molecule species and/or CO2 while the route of dichloromethane – methanol – formaldehyde – formic acid – small-molecule species and/or CO2 explained the catalytic oxidation of dichloromethane. All of these findings may facilitate the design of novel heterogeneous catalysts for VOCs oxidation and progress the development of catalytic ozonation for toluene and dichloromethane abatement.