Effects of sodium modification, different reductants and SO2 on NO reduction by Rh/Al2O3 catalysts at excess O2 conditions

Although many catalysts of NO reduction have been developed, the presence of excess O2 and SO2 significantly inhibits their performance when they are used to treat the incineration flue gas. To solve such problem, this study prepared new Rh/Al2O3 catalysts and investigated the effects of Na modification, SO2 and different reductants. Experimental results indicated that the average removal efficiency of NO at such high O2 concentrations exceeded 80% when the Rh/Al2O3 catalysts were used. CO was a better reductant than C3H6 and the best concentration ratio of reductant/NO was equal to 1. Adding Na to modify Rh/Al2O3 catalysts significantly enhanced the removal efficiency of NO from 80 to 99% at 250-300 °C, especially at relative high SO2 concentrations. Unfortunately, Rh-Na/Al2O3 catalysts do not have long-time activities for NO reduction, possibly because of the formation of NaNO3. Both Rh/Al2O3 and Rh-Na/Al2O3 catalysts have good performance for NO reduction, they can feasibly be used to reduce NO in the flue gas from waste incineration.