Synergistic promotion effects of surface hydroxyl groups (-OH) and nitrate groups (-NO3) on catalytic ozonation of toluene over MnFe catalyst

Abstract

A series of MnFe catalysts were prepared by hydrothermal synthesis combined with heat treatment at different temperatures. The characterizations demonstrated that MnFe-120 with both surface -OH and -NO3, MnFe-175 with surface -OH, MnFe-300 containing neither surface -OH nor -NO3, and MnFe-300-NO3 containing surface -NO3 were gained by drying or calcination and impregnation. The activity evaluation showed that the order of catalytic activity was MnFe-120 > MnFe-175 > MnFe-300-NO3 > MnFe-300. Further, characterizations and experiment results revealed that O3 adsorbed on the surface of the catalyst can interact with surface -OH and generated hydroxyl radicals (·OH). The presence of surface -NO3 provided more Lewis acid sites, thereby promoting H2O adsorption and conversion to the surface -OH, which supplemented the surface -OH consumed by the interaction with O3. It was deduced that the coexistence of surface -OH and -NO3 improved the production of·OH, which synergistically promoted the catalytic ozonation of toluene.