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

Understanding how H2O affects SO2 tolerance of SCR catalysts at different working temperatures is of great importance. Herein, we reported that H2O addition at ultra-low temperature of 100 °C induced a significant promotion on SO2 tolerance of MnOx-CeO2 catalysts. Sole SO2 led to serious activity loss from 100% to 20%, while H2O coexistence alleviated the deactivation and an admirable activity of 60% was reserved. Combining experimental characterizations with DFT calculation, we demonstrated that H2O 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 H2O on SO2 tolerance, which is expected to deepen our understanding on the role of H2O in modulating surface species and catalytic behaviors of SCR catalysts.