Selective catalytic reduction of nitric oxide with carbon monoxide over alumina-pellet-supported catalysts in the presence of excess oxygen.

Selective catalytic reduction of nitrogen oxides with carbon monoxide (CO-SCR) is a promising technology to remove NO and CO simultaneously from flue gas. The thermodynamic analyses of catalytic process were performed toward four kinds of active metal oxides (CuO, CoO, MnO and CeO). According to the standard Gibbs free-energy changes calculated, Mn had better resistance to oxygen than Cu, Co and Ce, while Cu and Ce had better resistance to water vapor poisoning, as active metals. Then, a series of binary- and ternary-preformed catalysts with different metal ratios were prepared by the impregnation method using AlO pellets as support and tested in excess oxygen (16 vol%) atmosphere with or without SO. The results of experiment were analyzed based on thermodynamic analyses. Results indicated that the NO conversions of Cu-Co/AlO catalysts increased with the rise of reaction temperature; however, the tendency changed at 160°C for Cu-Mn/AlO. Besides, the NO conversions of Cu-Mn/AlO were better than Cu-Co/AlO. The catalysts with the metal ratio of 1.5 had the best denitrification performance. Among various binary catalysts, Cu-Mn/AlO with the metal ratio Cu:Mn of 1.5 showed promising activity for CO-SCR, giving nearly 90% NO conversion. Besides, the doping of Ce could inhibit the sulfur poisoning and promote the oxide of CO under experimental conditions.