Study on the synergy effect of MnOx and support on catalytic ozonation of toluene

Abstract

MnO_x has received widespread attention in low-temperature catalytic oxidation of VOCs, however, the synergy effect of MnO_x and support on the VOCs catalytic ozonation were rarely studied. In this study, five different MnO_x/X (X: MCM-41, 13X, ZSM-5, HY, USY) were synthesized and found their support greatly affect the catalytic oxidation activity. MnO_x/MCM-41 presents the largest specific surface area, pore volume and unique surface morphology, and thereby provides more sites for MnO_x loading and VOCs adsorption. Moreover, MnO_x/MCM-41 presents a high proportion of Mn³⁺, which helps to enhance the ion exchange capability, and thus promotes the regeneration of oxygen vacancies. Furthermore, a part of Mn was proved to be introduced into the MCM-41 lattice, which can promote the electron transfer between the active components and the support, and thereby effectively improve the surface electronic properties of the catalyst. The toluene catalytic experiments showed that MnO_x/MCM-41 exhibited the best catalytic activity, presenting complete degradation of O₃ and VOCs at room temperature. In addition, 5 wt%MnO_x/MCM-41 exhibited better catalytic activity than other loading, and its higher surface oxygen species endowed it with strong water resistance and stability. In-situ DRIFTs indicated that toluene was initially oxidized into benzyl alcohol during the adsorption process, and then decomposed to intermediate products (benzaldehyde, phenolate, etc.) during the catalytic ozonation process, and finally oxidized to carbon dioxide. In conclusion, the supply of loading sites and the improvement of interfacial electron transfer are the manifestations of the synergy between the support and MnO_x, leading to the promotion of the catalytic ozonation of VOCs.

Keywords: Catalyst; Catalytic ozonation; Degradation; Ozone; Support; Toluene.