Iron Oxide as a Promoter for Toluene Catalytic Oxidation Over Fe–Mn/γ-Al2O3 Catalysts

Fe–Mn/γ-Al2O3 catalysts that prepared by the wet-impregnation method were used to degrade toluene, a VOCs model compound. The results indicated that the 10Fe–15Mn/γ-Al2O3 exhibited 95% of toluene conversion as well as 95% of CO2 yield at 300 °C. The Fe–Mn/γ-Al2O3 showed a better toluene oxidation activity with respect to the Fe/γ-Al2O3 and Mn/γ-Al2O3. The introduction of Fe into the Mn/γ-Al2O3 resulted in higher surface area, higher Mn3+/(Mn3+ + Mn4+) ratio, lower reduction temperature, and homogenous distribution of Mn. Meanwhile, the co-exist of the Fe3+ and Mn3+ over the 10Fe–15Mn/γ-Al2O3 also favored for the oxygen transfer, which may enhance the catalytic oxidation performance. The initial toluene was adsorbed on surface of the catalysts and formed benzoyl oxide (C6H5–CH2–O), and then the benzoyl oxide (C6H5–CH2–O) was oxidized to benzaldehyde. Furthermore, the benzaldehyde was further oxidized to form benzoic acid that could be converted to CO2 and H2O.