Transformation of Arsenic from Poison into Active Site by Construction of Unique AsOx/CeO2 Interface for Stable NOx Removal.

Abstract

Arsenic in the flue gas has been widely reported as a common poison for SCR catalysts; however, an appropriate coping strategy is still lacking to improve the arsenic resistance performance. Herein, a unique AsOx/CeO2 interface is constructed to transform arsenic from poison into active site with balanced acid-redox property, successfully achieving efficient NOx removal. The optimized AsOx/CeO2 exhibits high NOx removal efficiency, four times that of the As-poisoned V2O5/TiO2 catalyst, and even comparable to the state-of-the-art SCR catalysts. It was found that the As-O-Ce interfacial sites in oxygen-bridged As dimers on CeO2 can provide both Lewis acid sites and active lattice oxygen species, enhancing the adsorption and activation of NH3 to form key -NH2 intermediates, thereby facilitating the NH3-SCR reaction. More surprisingly, a thin CeO2 layer on the top of V2O5/TiO2 can capture arsenic to protect catalysts from arsenic attacking, which improves the catalytic activity to 2.8 × 10-7 mol g-1 s-1, even higher than that of fresh V2O5/TiO2 (2.0 × 10-7 mol g-1 s-1). Therefore, this strategy provides new ideas not only for designing antipoisoning SCR catalysts but also a feasible solution for the stable operation of commercial SCR catalysts in arsenic-containing flue gas.