An investigation of the activity and mechanism of the catalytic oxidation of toluene by FeMnOx catalyst

Abstract

To examine the influence of Fe-Mn interactions on the catalytic removal to toluene, FeOx, MnOx and FeMnOx catalysts were manufactured via co-precipitation approach. FeMnOx catalysts presented the optimal low-temperature catalytic toluene activity which attained 100 % removal of toluene (T100) at 270 ℃. The physical and chemical characterization of the material confirmed an increased ratio of Mn3+/Mn4+ and Oads/Olat bonds caused by to the formation of Fe3+-O-Mn3+ bonds. Concurrently, the low-temperature catalytic activity for toluene increased with the increased density of oxygen vacancies, the changed properties in oxygen vacancies and the enhanced oxidation capacity of surface activated oxygen species. In situ DRIFTS experiments were performed to infer different toluene degradation pathways on three catalysts. The catalytic routes for toluene over FeMnOx catalyst was different at 150 ℃ and 260 ℃. At 150 ℃, as the surface oxygen vacancies were not fully activated, the reaction pathway was toluene → benzyl alcohol → benzaldehyde → phenol. The path of toluene over FeMnOx catalyst at 260 ℃ was toluene → benzyl alcohol → benzoaldehyde → benzoate → maleic anhydride and carbonate → H2O and CO2. As compared with MnOx and FeOx catalysts, FeMnOx catalyst could oxidize benzyl alcohol to benzaldehyde and phenol at 150 ℃. This decreased the energy required to open the ring of benzene and accelerated the catalytic oxidation rate.