New Understanding of the Promotional Nature of SO<sub>2</sub> on Ce-Based Oxide Catalysts for Selective Catalytic Reduction of NO<sub><i>x</i></sub> with NH<sub>3</sub>
Tao Zhang, Guoxin Ma, Yunsong Mu, Jie Li, Yue Peng, Guohua Liu, Bing Liu, Jianjun Chen, Junhua Li
Abstract
Sulfur dioxide (SO 2 ) can significantly improve the selective catalytic reduction (SCR) performance of some metal oxide catalysts. Although extensively studied, understanding the promotional nature of SO 2 at the molecular and atomic levels is still a great challenge. Herein, we demonstrate that the redox and acid properties of Ce 1 Cr 3 O x could be successfully balanced via the sulfation, and its SCR activity is, therefore, significantly enhanced. More specifically, large-sized oxygen vacancies with a better oxidizing ability were covered by the formed sulfate ions (SO 4 2– ) during the sulfation process. At the same time, both small-sized oxygen vacancies and Lewis acid sites were introduced around the sulfated interface due to the reverse oxygen spillover from CeO x -S to sulfite-like ion (SO 3 – ) on CrO x -S, thus resulting in forming an active pair to promote two critical reaction steps of NH 3 -SCR reaction, i.e., the adsorption and activation of NH 3 molecules and the dissociation of the N–O bond in NHNO species. This work may fill the urgent need to solve the SO 2 poisoning problem of SCR catalysts.