Mechanism study of Na poisoning on Ce/TiO2(001) surface based on adsorption of reaction species and elementary reaction pathways

Abstract

The presence of alkali metal Na in flue gas can significantly impair the reactivity of Ce/TiO2 (CT) SCR (Selective Catalytic Reduction) catalyst. This study investigates the deactivation mechanism of Na on the Ce/TiO2 catalyst using Density Functional Theory (DFT) calculations, focusing on the adsorption of surface species and the pathway of elementary reaction. Due to the high affinity between Na atom and the catalyst surface, Na poisoning readily occurs on Ce/TiO2 (001) surface. The presence of Na on the catalyst surface hampers hydrogenation, oxygen vacancy formation, and NH3 adsorption, while also reducing the catalyst's acidity and reducibility. Additionally, Na impedes the NH3 dehydrogenation reaction, as well as the formation and decomposition of NH2NO and the dissociation of O2 on the catalyst surface, thereby inhibiting the NH3-SCR reaction. The inhibition of NO2 formation further affects the fast SCR reaction, which may explain the low-temperature deactivation of the catalyst.