Discovering the remarkable deNOx activity and anti-K poisoning of MnFeOx/H-Beta composite catalyst
SEPARATION AND PURIFICATION TECHNOLOGY(2024)
摘要
The practical application of MnFeOx catalyst is limited due to its narrow temperature window and poor resistance to alkali metal poisoning, such as K and Na. Alkali metal poisoning has always been a major factor in the deactivation of fixed-source denitration (deNOx) catalysts. Despite high activity at around 200(degrees)C , the catalyst's susceptibility to alkali metal poisoning hinders its effectiveness. In this study, a novel MnFeOx/H-Beta composite catalyst was prepared by the simple wet impregnation method. Beta zeolite, known for its large specific surface area compared to MnFeOx, special twelve-membered ring channel, and abundant acid sites, was introduced to adjust the acid and redox active sites. This resulted in MnFeOx/H-Beta having a wider temperature window and excellent resistance to K poisoning. Notably, the NOx conversion rate exceeded 80% between 180 and 460 C . K poisoning significantly reduces the acidity of the catalyst, as confirmed by various characterizations such as NH3TPD and NH3 adsorption in situ DRIFTs. After K poisoning, the total acid content of MnFeOx/H-Beta decreased from 14.99 to 9.47 mmol g(-1). The low acid content of MnFeOx allows the active sites to be easily covered by K, resulting in a reduction of the SCR performance, which can be attributed to the reduction of active nitrate species. The abundant acid sites of MnFeOx/H-Beta act as sacrificial sites and can coordinate with alkali metal K, thereby alleviating the poisoning of the catalyst to some extent. DFT calculations confirmed K binding to Bronsted acid sites on H-Beta zeolite, mitigating the detrimental impact of K on catalyst activity and lifetime. This research offers a pathway for designing efficient and alkali metal-resistant deNO(x )catalysts for real-world industrial applications.
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关键词
Beta zeolite,MnFeOx,Composite catalyst,NH3-SCR,K resistance,Mechanism
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