A MnO2-based catalyst with H2O resistance for NH3-SCR: Study of catalytic activity and reactants-H2O competitive adsorption

MnO2 with interlayer Ce3+ cation (Ce-MnO2) was synthesized by ion exchange approach. The Ce-MnO2 exhibited better low-temperature NH3-SCR catalytic activity as compared to Ce0.38Mn0.62O2-CP prepared by co-precipitation. The good performance was due to easy supply of labile oxygen species generated by migration of Ce species in Ce-MnO2 catalyst, which could promote the oxidation of reactants. The special structure of Ce-MnO2 promoted better properties in terms of low-temperature reduction properties, lower element species, adsorption capacity of reactants and surface acid sites, which was beneficial to NH3-SCR at low-temperature. It also showed superior H2O resistance with NOx conversion above 90 % below 150 degrees C. The competitive adsorptions between H2O and reactants over both of Ce-containing catalysts were investigated by in-situ DRIFT and TPD. The results indicated NOx with strong competitive adsorption on Ce-MnO2 surface than H2O. No competitive adsorption between NH3 and H2O over both of Ce-containing catalysts was also observed, different from previous reports.