Enhanced Hydrothermal Stability of Cu-SSZ-50 NH3-SCR Catalysts via the Re-dispersion of Introduced Fe upon Hydrothermal Processing

Cu-SSZ-50 zeolite is considered as a promising candidate for NH3-SCR catalysts. However, its hydrothermal stability is unsatisfactory, which limiting its application. In this study, the hydrothermal stability of Cu-SSZ-50 catalyst was remarkably improved by the introduction of Fe. Specifically, The NOx conversion of Fe-Cu-SSZ-50 was elevated from ~25% to ~80% at 200 ℃ in the NH3-SCR reaction after the hydrothermal aging process. H2-TPR, EPR, NH3-TPD, UV-Vis, XPS, TEM, NMR and DRIFTS were carried out to investigate the changes in the active sites and framework structure of the catalysts brought about by hydrothermal aging. The characterization results revealed that FexOy in the fresh samples underwent re-dispersion into smaller nanoclusters and also transformed into active Fe3+ ions during the hydrothermal aging process. This process inhibited the formation of inactive CuAl2Ox, thereby increasing the quantity of active Cu2+ sites in the aged catalyst and mitigating dealumination of the framework, ultimately enhancing the hydrothermal stability.