Unlocking Mixed-Metal Oxides Active Centers via Acidity Regulation for K&SO Poisoning Resistance: Self-Detoxification Mechanism of Zeolite-Confined NO Catalysts.

Selective catalytic reduction of nitrogen oxides (NO) with ammonia (NH-SCR) is an efficient NO reduction strategy, while the denitrification (NO) catalysts suffer from serious deactivation due to the coexistence of multiple poisoning substances, such as alkali metal (e.g., K), SO, ., in industrial flue gases. It is essential to understand the interaction among various poisons and their effects on the NO process. Herein, the ZSM-5 zeolite-confined MnSmO mixed (MnSmO@ZSM-5) catalyst exhibited better NO performance after the poisoning of K, SO, and/or K&SO than the MnSmO and MnSmO/ZSM-5 catalysts, the NO activity of which at high temperature (H-T) increased significantly (>90% NO conversion in the range of 220-480 °C). It has been demonstrated that K would occupy both redox and acidic sites, which severely reduced the reactivity of MnSmO/ZSM-5 catalysts. The most important, K element is preferentially deposited at -OH on the surface of ZSM-5 carrier due to the electrostatic attraction (-O-K). As for the K&SO poisoning catalyst, SO preferred to be combined with the surface-deposited K (-O-K-SO) according to XPS and density functional theory (DFT) results, the poisoned active sites by K would be released. The K migration behavior was induced by SO over K-poisoned MnSmO@ZSM-5 catalysts, and the balance of surface redox and acidic site was regulated, like a synergistic promoter, which led to K-poisoning buffering and activity recovery. This work contributes to the understanding of the self-detoxification interaction between alkali metals (e.g., K) and SO on NO catalysts and provides a novel strategy for the adaptive use of one poisoning substance to counter another for practical NO reduction.