Structural and electronic double effects on S-doping dendritic mesoporous CeFeW/DM catalyst for enhancing SO2 tolerance in the low temperature NH3-SCR reaction

Abstract

SO₂ poisoning severely impedes the development of Ce-based catalysts in NH₃-SCR process for nitrogen oxides elimination. S-doping dendritic mesoporous

(DM)-structured CeFeW/DM catalyst has been carefully designed in this work and its tolerance to SO₂ has been effectively enhanced. The DM structure allowed metal oxides to be highly dispersed and generated Ce–O–Fe active pairs with enhancing redox ability via the efficient electron transfer between Ce³⁺ + Fe³⁺ ↔ Ce⁴⁺ + Fe²⁺. Importantly, the opened center–radial pore channels not only facilitated rapid adsorption of NO and NH₃, but also distinctly alleviated the problem of ammonium sulfate blocking the catalyst pores during the NH₃-SCR process. Notably, S-doping enhanced the surface acidity and inhibited the adsorption and oxidation of SO₂ effectively. Besides, density functional theory calculation revealed that S-doping further perturbed the local electronic environment and formed an electron enrichment region around the Ce–O–Fe interface, which made SO₂ preferentially adsorbed on Fe sites, whereas NO was more inclined to be adsorbed on Ce sites. Therefore, the Ce active site was protected from SO₂ poisoning, enabling both L-H and E-R reaction pathways simultaneously occurring with smooth adsorption and activation of NO on CeFeW/DM. This study deeply reveals the coordination efforts between catalyst structure and electronic effects, which provided a new idea for designing highly efficient SO₂-resistant Ce-based catalysts for low temperature NH₃-SCR reaction.