Effects of sodium modification, different reductants and SO 2 on NO reduction by Rh/Al 2O 3 catalysts at excess O 2 conditions

Abstract

Although many catalysts of NO reduction have been developed, the presence of excess O 2 and SO 2 significantly inhibits their performance when they are used to treat the incineration flue gas. To solve such problem, this study prepared new Rh/Al 2O 3 catalysts and investigated the effects of Na modification, SO 2 and different reductants. Experimental results indicated that the average removal efficiency of NO at such high O 2 concentrations exceeded 80% when the Rh/Al 2O 3 catalysts were used. CO was a better reductant than C 3H 6 and the best concentration ratio of reductant/NO was equal to 1. Adding Na to modify Rh/Al 2O 3 catalysts significantly enhanced the removal efficiency of NO from 80 to 99% at 250–300 °C, especially at relative high SO 2 concentrations. Unfortunately, Rh–Na/Al 2O 3 catalysts do not have long-time activities for NO reduction, possibly because of the formation of NaNO 3. Both Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts have good performance for NO reduction, they can feasibly be used to reduce NO in the flue gas from waste incineration.