Low temperature oxidation of toluene by ozone over MnOx/γ-alumina and MnOx/MCM-41 catalysts

Ozonation of toluene catalyzed by manganese oxides supported on γ-alumina and siliceous MCM-41 was studied at temperatures from 22 to 100 °C. Nitrate and acetate precursors of manganese were used to compare structure and activity of dispersed manganese oxides on γ-alumina and MCM-41. Catalysts were characterized by X-ray diffraction, Raman spectroscopy, BET and ICP-MS. Catalysts became deactivated at room temperature due to accumulation of carbon species. A minimum reaction temperature of 65 °C was required to achieve steady state oxidation of toluene with ozone. Alumina supported catalysts prepared from the nitrate and acetate precursors had comparable activity. MCM-41 supported catalyst resulted in lower toluene and ozone conversion in comparison to γ-alumina catalysts above 40 °C. CO and CO2 were the main reaction products while oxalic acid, acetic acid, benzene and maleic anhydride were also detected as the minor reaction byproducts.

► Acetate and nitrate precursors of manganese result in different dispersion and structures.
► Catalysts deactivate at room temperature due to accumulation of carbon specious.
► Dispersion and oxidation state of Mn are two important factors on catalyst activity.
► COx are major reaction products while minor byproducts are oxalic acid, acetic acid, benzene and maleic anhydride.