Improving performance of Cu-ZSM-5 catalytic decomposition of NO and resistance to K-poisoning by Ce and Zr co-doping

The most economical denitration method is the direct decomposition of NO into the most environmental friendly and cleanest N₂ and O₂ in the action of the Cu-ZSM-5 catalyst. There are a lot of alkali metals in the high temperature flue gas. However, the alkali metals can reduce the catalytic activity, shorten the service life of the catalyst, and cause an irreversible deactivation of the catalyst. The MZ5(M: Cu, Ce, Zr, CuCe, CuZr, CuCeZr) catalysts were prepared by the ion exchange method, and the K ions were loaded onto the MZ5 catalysts by the incipient wetness impregnation method. The results of the denitration experiments indicated that at the optimal reaction temperature of 550 ℃, the NO conversion rate of the CuCeZrZ5 catalyst increased from 53% to 58% compared with that of CuZ5; the NO conversion rate of the KCuCeZrZ5 catalyst increased from 39% to 52% compared with that of KCuZ5; and the NO conversion rate of the KCuCeZrZ5 catalyst increased from 53% to 52% compared with that of CuZ5. The ICP, SEM, XRD, BET, XPS, H₂-TPR and O₂-TPD were used to analyze thoroughly the element content, micro morphology, skeleton structure, pore law, copper species, chemical adsorption oxygen, copper ion reduction temperature and oxygen desorption temperature in active species. The characterization results showed that the introduction of Ce and Zr did not damage the framework structure, crystallinity and grain size of the catalyst, on the other hand, it promoted the formation of more oxygen vacancies and the active component Cu—O—Cu⁽2+ )in the catalyst, and enhanced the oxygen storage and transport capacity of the catalyst. When K⁺ was introduced, the denitrification activity of CuZ5 catalyst decreased obviously, the pore structure deteriorated, and CuO was formed by the migration of K⁽+ )with the active component Cu—O—Cu²⁺. K⁺ preferentially combined with Ce species, which effectively protects the unique three-dimensional cross-pore structure of ZSM-5, reduces the migration of Cu²⁺ to form CuO and promotes the redox cycle between the active component Cu—O—Cu²⁺ and Cu—□—Cu²⁺.