Acid treatment of ZrO2-supported CeO2 catalysts for NH3-SCR of NO: Influence on surface acidity and reaction mechanism

Abstract

BackgroundDue to excellent oxygen storage capacity and redox ability, Ce-based catalysts are usually considered as one of the promising candidates of traditional V-based catalysts for NH3-SCR of NO. However, surface acidity of Ce-based catalysts is often insufficient which restrains their SCR performance to some extent. MethodsHerein, ZrO2-supported CeO2 catalysts were prepared by precipitation and wet impregnation methods. Aiming to promote catalyst surface acidity, a novel method was proposed to pre-treat ZrO2 support with various acids (HCl, HNO3, H3PO4 and H2SO4) via impregnation process. and the effects of acid treatment on SCR performance of CeO2/ZrO2 catalysts had been investigated. Significant findingsIt was worthy to note that H2SO4-treated CeO2/ZrO2 catalyst exhibited a superior NO removal efficiency which was higher than 94% in a wide temperature range of 248–500 °C. NH3-TPD results revealed that the surface acidities acidity of CeO2/ZrO2 catalysts had been obviously enhanced after acid treatment with HNO3, H3PO4 and H2SO4, except for HCl. According to in-situ DRIFRS results, one could infer that SCR reactions occurred over CeO2/ZrO2 catalyst without acid treatment might proceed only in E-R mechanism. But for acid-treated CeO2/ZrO2 catalysts, both E-R and L-H mechanisms were might be followed in SCR reaction process.