Improvement in activity and alkali resistance of a novel V-Ce (SO4) 2/Ti catalyst for selective catalytic reduction of NO with NH3.

A series of V-Ce(SO4)2/Ti catalysts for selective catalytic reduction (SCR) of NO with ammonia are prepared by impregnation method. Low temperature SCR activity and alkali resistance of the optimal V-0.5Ce(SO4)2/Ti sample are found to be better than on the commercial V-W/Ti catalyst. Also, V-0.5Ce(SO4)2/Ti shows an excellent durability in the presence of SO2 and H2O, indicating to have prospects for the industrial application. Based on catalysts characterization and in-situ DRIFTS studies, a higher proportion of surface active oxygen generated by the introduction of Ce and a much faster H2 reduction point out the improved redox properties of V-0.5Ce(SO4)2/Ti, which results in a stronger NO oxidative activation and is confirmed by a more abundant formation of surface NO⁺ and NO3⁻ species. When exposed to SCR conditions where both NH3 and NO are present, this enhanced NO activation can produce more reactive nitrite and/or NO⁺ intermediates which then readily react with adsorbed NH3 and decompose to N2 and H2O, accounting for the improved SCR activity of V-0.5Ce(SO4)2/Ti at low temperatures. The addition of Ce(SO4)2 also provides abundant reactive acid sites and adsorbed NH3 species thus increase. Even after Na poisoning, adequate surface acidity and redox properties still remain. Furthermore, relatively higher contents of V-OH are preserved owing to the interaction between Na and OSO, acting as a protection for the active sites. These promotional effects contribute to the better alkali resistance of V-0.5Ce(SO4)2/Ti. Therefore, all the results suggest that V-0.5Ce(SO4)2/Ti is a promising candidate as a catalyst for NH3-SCR in coal-fired power plants, especially under high Na-content conditions.