Catalytic removal of NO in waste incineration processes over Rh/Al2O3 and Rh–Na/Al2O3: Effects of particulates, heavy metals, SO2 and HCl

Two novel catalysts Rh/Al2O3 and Rh–Na/Al2O3 were prepared for NO removal and tested their practical performances in a laboratory-scale waste incineration system. The effects of particulates, heavy metals, and acid gases on the catalysts were evaluated and investigated through several characterization techniques, such as SEM, EA, XRPD, ESCA, and FTIR. The results indicated that the NO conversions were increased with the accumulation of particulates on the surface of catalysts, which was attributed to the increase in carbon content. However, the increase in heavy metals Cd and Pb contents on the surface of catalysts decreased the activity of catalyst for NO removal but did not change the chemical state of Rh and Na. The Rh/Al2O3 catalysts were poisoned when the acid gases SO2 and HCl were present in the flue gas, because Rh and Al reacted with S and Cl to form inactive products. Adding Na to Rh/Al2O3 catalysts produced a promoting effect for SO2 removal due to the formation of Na2SO4. The influence levels of different pollutants on the performances of Rh/Al2O3 and Rh–Na/Al2O3 catalysts for NO removal followed the sequence of HCl > heavy metals > SO2 > particles.