Efficient Catalytic Ozonation of Dimethyl Carbonate on M-Mn (M = Cr, Cu, Co)/ZSM-5 Zeolites: Further Analysis of Reaction Mechanism

Mn-based catalysts usually exhibit considerable potential for enhancing the catalytic ozonation of volatile organic compounds (VOCs) at a lower temperature. In this study, bimetallic oxides M-Mn (M = Cr, Cu, Co) were supported on HZSM-5 zeolites to degrade dimethyl carbonate (DMC, chemical formula C3H6O3), a typical VOC emitted during the productive process of lithium batteries, with Mn/ZSM-5 for comparison. The Cr-doped catalyst CrMn/ZSM-5 could achieve 92% DMC conversion with 91% CO2 selectivity (O3/DMC = 6, T = 120 °C), showing an excellent catalytic performance among the prepared catalysts. The exceptionally low-temperature activity of CrMn/ZSM-5 was attributed to the synergistic effect of its large surface area, sufficient oxygen vacancies, and suitable acidity and reducibility, which collectively enhanced the level of O3 activation and accelerated DMC degradation. Furthermore, the catalyst demonstrated desirable stability and resistance to varying concentrations of water vapor. To elucidate the reaction pathway, in situ DRIFTS was employed to track the evolution of intermediate species during the adsorption and catalytic ozonation of DMC. With a further study of DFT calculation, the reaction mechanism of DMC catalytic ozonation on CrMn/ZSM-5 catalysts was put forward.