Deactivation Mechanism of Potassium on the γ-Fe₂O₃ Catalysts for SCR Reaction: A DFT Study

The presence of alkali metals in flue gas can lead to catalyst poisoning, which can significantly impact the de-NOx efficiency of the catalyst. There is a lack of specific studies on the influence of potassium (K) poisoning on the efficiency of γ-Fe₂O₃. In this study, the mechanism of K poisoning on the γ-Fe₂O₃ surface was studied based on DFT, and the influence of K on molecular adsorption and SCR reaction process was analyzed. The results show that the K₂O and KCl provide O, K, and Cl ions when deposited on the catalyst surface. The adsorption and dehydrogenation processes of NH3 were enhanced to varying degrees near the O and Cl iron sites, but the subsequent generation and decomposition of NH₂NO were inhibited. On the sites near K cations, the adsorption, dehydrogenation, and subsequent SCR reaction processes of NH₃ are hindered, and the adverse effects on the reaction are greater on the Fe sites closer to K. As well as the presence of K can to some extent promote the adsorption of NO and O₂.