Activity and characterization of Rh/Al2O3 and Rh–Na/Al2O3 catalysts for the SCR of NO with CO in the presence of SO2 and HCl

SO2 and HCl are major pollutants emitted from waste incineration processes. Both pollutants are difficult to remove completely and can enter the catalytic reactor. In this work, the effects of SO2 and HCl on the performance of Rh/Al2O3 and Rh–Na/Al2O3 catalysts for NO removal were investigated in simulated waste incineration conditions. The characterizations of the catalysts were analyzed by BET, SEM/EDS, XRD, and ESCA. Experimental results indicated the 1%Rh/Al2O3 catalyst was significantly deactivated for NO and CO conversions when SO2 and HCl coexisted in the flue gas. The addition of between 2 and 10 wt.% Na promoted the activity of the 1%Rh/Al2O3 catalyst for NO removal, but decreased the CO oxidation and BET surface area. The catalytic activity for NO removal was inhibited by HCl as a result of the formation of RhCl3. Adding Na to the Rh/Al2O3 catalyst decreased the inhibition of SO2 because of the formation of Na2SO4, which was observed in the XRD and ESCA analyses. SEM mapping/EDS showed that more S was residual on the surface of the Rh–Na/Al2O3 catalyst than Cl.