Effects of precipitant and calcination temperature on the catalytic activities of chromic oxide catalysts for NO oxidation at ambient temperature

Various chromic oxide catalysts were prepared by the precipitation method and used for NO oxidation at ambient temperature. It was found that the catalytic performance of chromic oxide catalysts was greatly dependent on the calcination temperature and the choice of the precipitants. The best catalyst was obtained under 300 °C with ammonia solution as the precipitant, which can oxidize NO to NO₂ for more than 500 min running. The examinations of catalysts based on XRD, BET, HRTEM, SEM, TG, RAMAN, XPS and in situ DRIFTS revealed that ammonia solution as the precipitant presented amorphous phase, large surface area with hydroxyl, packing particles with small size, distorted octahedral metal–oxygen bonds with high surface concentration of Cr and then exhibited high catalytic activity of chromic oxide catalysts. The precipitants displayed difficulty to decompose and introducing impurity showed low catalytic performance over the chromic oxide catalysts for NO oxidation.