Synergistic effect between the redox property and acidity on enhancing the low temperature NH3-SCR activity for NOx removal over the Co0.2CexMn0.8-xTi10 (x=0-0.40) oxides catalysts

A series of Co0.2CexMn0.8-xTi10 (x=0, 0.05, 0.15, 0.25, 0.35 and 0.40) oxides catalysts were prepared by the solgel method and used for NH3-SCR. These catalysts were characterized by means of XRD, SEM-EDS, H-2-TPR, NO/NH3 oxidation, NH3 (NO and SO2)-TPD, XPS and in situ DRIFTS. It was found that the Co0.2Ce0.35Mn0.45Ti10 catalyst showed excellent NH3-SCR activity and a broaden temperature window (180-390 degrees C), accompanied with good resistance to SO2 and H2O. It could be concluded that the redox ability of Co0.2Ce0.35Mn0.45Ti10 could be reduced by Co and Ce doping, which resulted in high NH3-SCR activity at high temperature and good resistance of SO2. The addition of Co and Ce can supply more acid sites and NOx adsorption sites over Co0.2Ce0.35Mn0.45Ti10. Thus, more surface Bronsted acid and Lewis acid sites, NOx adsorption sites and modest redox ability of Co0.2Ce0.35Mn0.45Ti10 play key roles in the special NH3-SCR activity due to the interactions among Ce, Co, Mn and Ti oxides. Furthermore, the results of in situ DRIFTS study reveal the NH3-SCR reactions over Co0.2Ce0.35Mn0.45Ti10 and Co0.2Mn0.8Ti10 catalysts are mainly controlled by E-R mechanism (> 210 degrees C) and the L-H mechanism (< 210 degrees C), respectively.