Microwave catalytic process: Low-temperature selective oxidation of toluene to benzoic acid over V2O5/TiO2

Under microwave irradiation, the effects of reaction bed temperature, O2/ toluene ratio, total space velocity (SV) of feed gas and V2O5 loading were investigated in order to optimize the reaction conditions over V2O5/TiO2 for the selective oxidation of toluene. It was suggested that when the reaction bed temperature was 250°C, O2/toluene molar ratio was 6, the total SV was 10 000 h-1, and the V2O5 loading was 8%, the catalytic activity of V2O5/TiO2 was the highest with 20% yield of benzoic acid. Specially, in the microwave catalytic process the modification of V2O5/TiO2 with MoO3 or Ag2O, which had no or negative influence on the titled reaction in the conventional case, greatly promoted the selective oxidation of toluene leading to further improvement in the catalyst performance in terms of benzoic acid yield (41%). Compared with the conventional catalytic process, the effects of microwave electromagnetic field on the catalysts were also discussed tentatively.