The Recycle of Red Mud as NH₃-SCR Catalyst by Acid Pretreatment: Insight into the Interaction Between Iron and Titanium Species

The red mud was activated by an acid leaching and reprecipitation approach to be used as NH3-SCR catalyst. The effect of acid concentration on the leaching rates of Fe, Ti, Al, Ca and Na was investigated, specifically, the interaction between Fe and Ti components in the obtained red mud-based catalysts was concerned. With the acid concentration increasing (below 3.1 mol/L), more Fe and Ti are leached out, meanwhile, Ti can be incorporated into Fe2O3 phase and the crystallite size of Fe2O3 becomes smaller, and the obtained catalyst exhibits better low-temperature activity and SO2 resistance. The HRM3.1 catalyst obtained at the acid concentration of 3.1 mol/L possesses strongest reducibility, largest amount of surface chemisorbed oxygen and medium surface acidity. The in-situ DRIFTS results show that more NO can be adsorbed and oxidized over the HRM3.1 catalyst to generate more nitrate species, even though in the presence of SO2, alleviating the suppression of SO2 on the NH3-SCR reaction, and thus the SO2 tolerance is enhanced. [GRAPHICS] .