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_x and CO simultaneously from flue gas. The thermodynamic analyses of catalytic process were performed toward four kinds of active metal oxides (Cu_xO_y, Co_xO_y, Mn_xO_y and Ce_xO_y). 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 Al₂O₃ pellets as support and tested in excess oxygen (16 vol%) atmosphere with or without SO₂. The results of experiment were analyzed based on thermodynamic analyses. Results indicated that the NO conversions of Cu-Co/Al₂O₃ catalysts increased with the rise of reaction temperature; however, the tendency changed at 160°C for Cu-Mn/Al₂O₃. Besides, the NO conversions of Cu-Mn/Al₂O₃ were better than Cu-Co/Al₂O₃. The catalysts with the metal ratio of 1.5 had the best denitrification performance. Among various binary catalysts, Cu-Mn/Al₂O₃ 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.