Catalytic oxidation of toluene on Mn–containing mixed oxides prepared in reverse microemulsions

Catalytic combustion of toluene over Mn–containing mixed oxides has been investigated. The catalysts have been prepared by reverse microemulsion method and characterized by XRD, SEM and TPR. It is found that catalytic conversion of toluene on the Mn–Zr mixed oxides prepared by reverse microemulsion method is much higher than that on the Mn–Zr mixed oxides prepared by conventional coprecipitation with the same chemical compositions. The catalytic activity gradually increases with an increase of Mn loading on ZrO2 prepared by reverse microemulsion method. When Mn loading reaches 50 mol%, the total conversion temperature is lowered to 260 °C. Heat treatment of the catalysts leads to the decrease in the activity of toluene conversion, however the toluene conversion remains still high, i.e., 99% at 320 °C after calcination up to 750 °C, which implies the catalyst is highly thermally stable. In addition, Fe–Mn, Co–Mn and Cu–Mn mixed oxides have also been synthesized by reverse microemulsion method, and tested for catalytic oxidation of toluene. Among these metal oxides, the Cu–Mn catalyst is found to give the highest activity for complete oxidation of toluene. Mn0.67–Cu0.33 (Cu loading 33 mol%) shows the total oxidation of toluene at about 220 °C, which is very close to the activity of the widely investigated Pd catalyst for the reaction.