Investigation into the roles of different oxygen species in toluene oxidation over manganese-supported platinum catalysts

With the aim to elucidate the roles of different oxygen species, the catalytic oxidation of toluene over Pt/Mn3O4 synthesized by a facile reduction method was investigated. Compared with the Pt/Mn3O4-C using the commercial Mn3O4 as the support, Pt/Mn3O4-R was found to possess more surface oxygen vacancies, exhibit better redox properties and dispersion of platinum particles, leading to its higher activity for toluene oxidation (T90 = 183 ℃). Through toluene-TPD, toluene-TPSR and in-situ DRIFTS, it was found that toluene oxidation over Pt/Mn3O4-R catalyst might follow the Mars–van Krevelen (MVK) mechanism and the pathway of toluene oxidation over Pt/Mn3O4-R was possible toluene → benzoate → carbonate → CO2. The lattice oxygen species on the surface of catalysts was directly involved in the oxidation of toluene and played an important role in the formation of key intermediate such as carbonate, resulting in the difference of the reaction mechanism and pathway between Pt/Mn3O4-R and Pt/Mn3O4-C. In addition, the degradation of the surface carbonate was demonstrated to be the rate-controlling step at 180℃ to 200℃.