Insight into the Promoting Role of Er Modification on SO₂ Resistance for NH₃-SCR at Low Temperature over FeMn/TiO₂ Catalysts

• Main Authors: Huan Du, Zhitao Han, Xitian Wu, Chenglong Li, Yu Gao, Shaolong Yang, Liguo Song, Jingming Dong, Xinxiang Pan
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Catalysts
• Subjects: FeMn/TiO₂; Er modification; SCR; SO₂ resistance; low temperature
• Online Access: https://www.mdpi.com/2073-4344/11/5/618

Er-modified FeMn/TiO₂ catalysts were prepared through the wet impregnation method, and their NH₃-SCR activities were tested. The results showed that Er modification could obviously promote SO₂ resistance of FeMn/TiO₂ catalysts at a low temperature. The promoting effect and mechanism were explored in detail using various techniques, such as BET, XRD, H₂-TPR, XPS, TG, and in-situ DRIFTS. The characterization results indicated that Er modification on FeMn/TiO₂ catalysts could increase the Mn⁴⁺ concentration and surface chemisorbed labile oxygen ratio, which was favorable for NO oxidation to NO₂, further accelerating low-temperature SCR activity through the “fast SCR” reaction. As fast SCR reaction could accelerate the consumption of adsorbed NH₃ species, it would benefit to restrain the competitive adsorption of SO₂ and limit the reaction between adsorbed SO₂ and NH₃ species. XPS results indicated that ammonium sulfates and Mn sulfates formed were found on Er-modified FeMn/TiO₂ catalyst surface seemed much less than those on FeMn/TiO₂ catalyst surface, suggested that Er modification was helpful for reducing the generation or deposition of sulfate salts on the catalyst surface. According to in-situ DRIFTS the results of, the presence of SO₂ in feeding gas imposed a stronger impact on the NO adsorption than NH₃ adsorption on Lewis acid sites of Er-modified FeMn/TiO₂ catalysts, gradually making NH₃-SCR reaction to proceed in E–R mechanism rather than L–H mechanism.