Synergetic degradation of VOCs by vacuum ultraviolet photolysis and catalytic ozonation over Mn-xCe/ZSM-5.

Abstract

Volatile organic compounds (VOCs) are one of the most important precursors to form the fine particulate matter and photochemical smog, and should be strictly controlled. Vacuum ultraviolet (VUV) photolysis has provided a facile and an effective way to remove VOCs due to its powerful oxidation capability under mild reaction conditions. However, VUV irradiation would generate ozone which brings about secondary pollution. In this study, ZSM-5 supported Mn-Ce mixed oxides (Mn-xCe/ZSM-5) were fabricated as efficient catalysts for ozone catalytic oxidation (OZCO) process, which were applied in combination with VUV photolysis to remove O3 byproduct and simultaneously facilitate toluene oxidation. The results indicated that the Mn-3Ce/ZSM-5 catalyst considerably enhanced the catalytic degradation efficiency up to 93% for the gas-phase toluene, one of the hazardous VOCs. Meanwhile, almost all the O3 by-product could be eliminated in the process. It was found that the strong interaction of the MnOCe bond and the variable chemical valence of Mn and Ce based species in the mixed oxides would tune the redox capacity of Mn-xCe /ZSM-5. An increase in surface Ce3+ species and surface density of oxygen vacancies would benefit the adsorption and catalytic transformation of O3 which eventually form the reactive oxygen species over Mn-xCe/ZSM-5.