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.