The influence of annealing temperature on copper-manganese catalyst towards the catalytic combustion of toluene: The mechanism study

The CuO-MnOx catalysts annealed at different temperatures were prepared and applied for catalytic oxidation of toluene. It was found that with the increase of annealing temperature, the toluene conversion improved initially but then reduced. The catalyst annealed at 500 °C showed the best toluene oxidation performance, and T100 was only 230 °C. The results of XPS, Raman and H2-TPR proved that the Olatt/Oads ratio and the synergistic effect were enhanced with annealing temperature at 300–500 °C, while a slight decline was observed beyond 500 °C. Thereby, abundant lattice oxygen and strong synergistic effect between CuO and MnOx in CM-500 contributed to its superior toluene oxidation performance. In addition, a mechanism pathway was proposed based on the in-situ DRIFTS results. The initial step was the adsorption of toluene on catalyst, then the benzoic acid was rapidly converted to phenol and maleate in the presence of O2, then the intermediates were further oxidized to CO2 and H2O by reacting with the supplementary surface lattice oxygen.