SO<sub>2</sub>-Tolerant NO<sub><i>x</i></sub> Reduction by Marvelously Suppressing SO<sub>2</sub> Adsorption over Fe<sub>δ</sub>Ce<sub>1−δ</sub>VO<sub>4</sub> Catalysts
Lin Kang, Lupeng Han, Penglu Wang, Chong Feng, Jianping Zhang, Tingting Yan, Jiang Deng, Liyi Shi, Dengsong Zhang
Abstract
SO2-tolerant selective catalytic reduction (SCR) of NOx at low temperature is still challenging. Traditional metal oxide catalysts are prone to be sulfated and the as-formed sulfates are difficult to decompose. In this study, we discovered that SO2 adsorption could be largely restrained over FeδCe1−δVO4 catalysts, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO2 tolerance at an extremely low temperature of 240 °C. The increasing oxygen vacancies, enhanced redox properties, and improved acidity contributed to the SCR activity of the FeδCe1−δVO4 catalyst. The reaction pathway changed from the reaction between bidentate nitrate and the NH3 species over CeVO4 catalysts via the Langmuir–Hinshelwood mechanism to that between gaseous NOx and the NH4+/NH3 species over FeδCe1−δVO4 catalysts via the Eley–Rideal mechanism. The effective suppression of SO2 adsorption allowed FeδCe1−δVO4 catalysts to maintain the Eley–Rideal pathways on account of the reduced formation of sulfate species. This work demonstrated an effective route to improve SO2 tolerance via modulating SO2 adsorption on Ce-based vanadate catalysts, which presented a new point for the development of high-performance SO2-tolerant SCR catalysts.