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

Background: Due 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. Methods: Herein, 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 findings: It 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 degrees 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. (c) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The study significantly enhanced the surface acidity of CeO2/ZrO2 catalysts through acid treatment, promoting the removal efficiency of NO in NH3-SCR, especially with higher performance observed in catalysts treated with H2SO4. Acid-treated catalysts may follow both E-R and L-H mechanisms in the SCR reaction process.