Unveiling the Remarkable Arsenic Resistance Origin of Alumina Promoted Cerium-Tungsten Catalysts for NH3-SCR.

The deactivation of selective catalytic reduction (SCR) catalysts by arsenic is a serious problem for NH3-SCR. However, it is tough to design catalysts with good resistance to arsenic compared to other poisons such as alkali metal, SO2, etc., because As not only deteriorates surface acidity but also redox property, causing excessive N2O generation. A novel CeO2-WO3-Al2O3 catalyst is developed with excellent arsenic resistance in this study, which presents only less than 10% activity loss compared to nearly 40% loss for CeO2-WO3 with same arsenic loading (As: 2.1 wt %). Moreover, a significant negative impact on the N2O generation for poisoning catalysts from 26.7 to 7.5 ppm has also been found. The characterization results demonstrated that the interaction between cerium and arsenic lead to Lewis acid sites and oxygen vacancies loss as well as unexpected oxidation sites formation. However, the introduction of Al weakens the deactivation effect by replacing cerium to interact with arsenic. Three aspects are proposed for obtaining excellent arsenic-resistant performance: (1) the protection of Lewis acid sites, (2) release of oxygen vacancies from As restriction, and (3) confinement of As5+ oxidizing capacity. This study may provide an effective strategy to design and develop novel virtuous antipoisoning catalysts.