The reduction of NO by NH3 over carbon catalysts was studied at temperatures in the range 140-320°C, and at NO and NH3 concentrations varying within 290-1160 ppm. The carbon catalysts of different surface areas were prepared by gasifying bituminous and sub-bituminous coal chars in CO2 to different extents of burn-off. The NO reduction rate was found to increase with the carbon surface area, which is an increasing function of the burn-off level. However, the activity per unit surface area of the carbons decreases with the extent of burn-off. By adding oxygen in the reacting system, the NO conversion can be significantly enhanced. The apparent activation energy was found to be around 20 kJ/mol for the reactions with or without oxygen addition. The apparent reaction orders with respect to NO and NH3 are functions of the reaction temperature and are affected by the presence of oxygen. It has been suggested on the basis of the kinetic study that the catalytic reduction of NO might be governed by two consecutive steps: the adsorption of NH3 on active sites, followed by the addition of NO or NO2 in the neighborhood of the C(NH3) complexes.
All Science Journal Classification (ASJC) codes
- 環境科學 (全部)