Kinetics study of molybdenum additives on catalytic performance of CeO₂/Al₂O₃ for selective catalytic reduction of NO

A series of CeMo_xO_y/Al₂O₃ catalysts were prepared by an extrusion method for the selective catalytic reduction of NO_x. Promotional effects of molybdenum additives on catalytic performances and the effects on the reaction of internal and external diffusion were studied; the reaction activation energy was calculated. The promotional effects of molybdenum additives on the reaction rate of CeO₂/Al₂O₃ for the selective catalytic reduction of NO were investigated.Results show that the catalyst with an Al/Ce/Mo molar ratio of 5:1:0.15, calcinated at 550℃, exhibits the highest catalytic activity (above 90%) in the active temperature window of 250 to 425℃ under the gas hourly space velocity (GHSV) of 7 200 h^-1. When the particle size is less than 40 mesh and the space velocity is more than 10⁵ h^-1, the effects of internal and external diffusion could be neglected. The selective catalytic reduction (SCR) reaction on CeMo_0.15O_y/Al₂O₃ was a first-order reaction, and the apparent reaction order was over the range of conditions, approximately 0 for NH₃ and O₂. The reaction activation energy of CeMo_0.15O_y/Al₂O₃ was 36.57 kJ·mol^-1, Mo additives reduced the activation energy of the catalyst reaction, which increased the rate of reaction and thereby improved the catalytic activity.