Enhanced sulfur resistance of H3PW12O40-modified Fe2O3 catalyst for NH3-SCR: Synergistic effect of surface acidity and oxidation ability

Abstract

A series of H3PW12O40 (HPW)-modified Fe2O3 catalysts for the selective catalytic reduction of NOx by NH3 (NH3-SCR) were synthesized via impregnation of HPW on Fe2O3 micro-flowers followed calcination. The optimum HPW/Fe2O3-350-0.5 catalyst exhibits nearly 100% of NO conversion at 240–460 °C as well as excellent SO2 resistance. The number of Brønsted acid sites and Lewis acid sites increases significantly after HPW modification, which promotes the adsorption of NH3. Moreover, the incorporation of HPW decreases the oxidation ability of Fe2O3 catalysts, which effectively inhibits the overoxidization of NH3, resulting in excellent catalytic activity and N2 selectivity. In-situ DRIFTS results indicate that the NH3-SCR reaction on HPW/Fe2O3-350-0.5 catalyst mainly follows Eley–Rideal (E-R) mechanism, in addition, the adsorption and oxidization of SO2 on the surface of HPW/Fe2O3-350-0.5 catalyst are suppressed due to high surface acidity and the decrease of oxidation ability, leading to the enhancement of SO2 tolerance of HPW-modified Fe2O3 catalysts.