Understanding the temperature-dependent H2O promotion effect on SO2 resistance of MnOx-CeO2 catalyst for SCR denitration.

Understanding how H 2 O affects SO 2 tolerance of SCR catalysts at different working temperatures is of great importance. Herein, we reported that H 2 O addition at ultra-low temperature of 100 °C induced a significant promotion on SO 2 tolerance of MnO x -CeO 2 catalysts. Sole SO 2 led to serious activity loss from 100% to 20%, while H 2 O coexistence alleviated the deactivation and an admirable activity of 60% was reserved. Combining experimental characterizations with DFT calculation, we demonstrated that H 2 O promoted hydroxyl formed on defect sites, which promoted more sulfite formation and retarded sulfates with strong electron-withdrawing capacity disturbing active Mn sites. In comparison with sulfates, sulfites exhibited less interference in adsorbed species, ensuring the occurrence of Eley-Rideal and Langmuir-Hinshelwood mechanisms. The present study discloses the unique temperature-dependent effect of H 2 O on SO 2 tolerance, which is expected to deepen our understanding on the role of H 2 O in modulating surface species and catalytic behaviors of SCR catalysts. [Display omitted] • Unusual temperature-dependent H 2 O promotion effect on SO 2 tolerance of SCR catalysts was reported. • The addition of H 2 O greatly alleviated the SO 2 poisoning of MnO x -CeO 2 catalysts at ultra-low temperature of 100 °C. • Hydroxyl group derived from H 2 O disassociation restricted the electron interaction between sulfur species and Mn sites, protecting active Mn via more sulfites forming. • Sulfites showed less interference on surface active adsorbed species and ensured the occurrence of both L-H and E-R mechanism over MnCe-SO 2 +H 2 O catalyst. [ABSTRACT FROM AUTHOR]