Mechanistic effect of SO2 on mesoporous CuFeAlZrOx catalyst for simultaneous removal of Hg0 and NO at wide temperature range

Abstract

Mesoporous CuFeAlZrOx catalyst is a promising substitute of V-based catalysts for potential candidate for simultaneous removal of Hg0 and NO due to its excellent performance at a broad temperature range. SO2 poisoning effects remain a challenge in development of efficient SCR catalysts for applications. In this paper, the effect of SO2 on mesoporous CuFeAlZrOx catalyst for simultaneous removal of Hg0 and NO at wide temperature range was studied. Relevant characterization techniques of H2-TPR, NH3-TPD, TG, SO2-TPD, XPS, Hg-TPD and in situ DRIFTS were used to reveal the correlativity between the physicochemical properties and SO2 resistance of CuFeAlZrOx catalysts. SO2 exhibited an inhibitory effect at low temperature (<300 °C) but a facilitative effect at high temperature(≥300 °C) for NH3-SCR reaction. At the same time, a promoting effect on Hg0 removal was observed during the whole temperature range. The deposition of NH4HSO4 and the decrease of redox capacity caused the loss of SCR activity at low temperatures, while the formed iron sulfate provided more Lewis acid sites facilitate the high-temperature SCR performance due to the strong electron withdrawing effect of the SO double bonds. In addition, the generation of iron sulfates and NH4HSO4 on mesoporous Cu1FeAlZrOx were alleviated because of the sacrifice of copper sites and promoted NH4HSO4 decomposition in mesopore channels. SO2 reacted with Hg0 to form HgSO4 and Hg2SO4, which contributed to Hg0 removal performance.