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 gamma-Fe2O3. In this study, the mechanism of K poisoning on the gamma-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 O-2. [GRAPHICS]