Abstract

The influence of post-synthesis treatment with MnSO4, (NH4)2SO4 and (NH4)2S2O8 blended solution on NH3-SCR activity and hydrothermal stability of Cu-SAPO-18 (Cu-18) was investigated. Via adjusting the mixed solution concentration, the optimal Mn/Cu-18-Ⅲ with higher deNOx activity and hydrothermal stability was acquired. Based on the optimal Mn/Cu-18-Ⅲ, diverse metal cations such as La3+, Ce3+, Sm3+ or Zr4+ were simultaneously doped into Cu-18 during Mn2+ and NH4+ blended solution treatment to further promote its catalytic performance before and after hydrothermal treatment. The doping with Sm could improve the NH3 activity and hydrothermal stability of Mn/Cu-18-Ⅲ to the greatest extent. The elevation of acid sites content and the disappearance of CuO species in Mn/Cu-18-Ⅲ caused the enhancement of its NH3-SCR activity. More Cu2+ and acid sites in SmMn/Cu-18-Ⅲ were responsible for its higher NH3-SCR activity than Mn/Cu-18-Ⅲ. The decline of vulnerable Brønsted acid sites by substituting Mn2+ or Sm3+ for H+ could restrain the hydrolysis of Cu-18 and enhance the hydrothermal stability of Cu-18 during hydrothermal treatment. The mechanism analysis demonstrates that the fresh and aged Cu-18, Mn/Cu-18-Ⅲ and SmMn/Cu-18-Ⅲ follow both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanism in NH3-SCR reaction, with the L–H mechanism being more dominated.

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