Kinetic Studies of the Direct Decomposition of Nitric Oxide

The dependence of NO decomposition rate on partial pressures or concentrations of NO and O_2 was investigated over H-Cu-ZSM-5-32.2-101.7 zeolite. The dependence of NO conversion into N_2 on contact time was examined to ensure that the reaction was not diffusion-limited under the experimental conditions. The reaction orders in NO concentration and the rate constants at 350, 450 and 550 oC were determined by varying NO concentrations in the feed while oxygen was absent. Then, oxygen was added to the inlet gas and the dependence of the reaction rate on oxygen concentration was examined by varying O_2 concentration for an NO concentration of 0.2%. The reaction order for O_2 and reaction constants at 450 and 550 oC were determined. Based on the reaction order for O_2 obtained at these two temperatures and a proposed reaction mechanism, the order was predicted at temperatures less than 450 oC. The reaction order for O_2 was negative and dependent on reaction temperature. On the basis of the experimental results obtained in this study, a new reaction rate equation at temperatures less than the most effective temperature as well as the mechanism involved were proposed.