Effect of metal elements doping on the CePO4 catalysts for selective catalytic reduction of NO with NH3

A series of Metals doped M-CePO4 (M=Zr, Co, Mo, Cu) catalysts were prepared via the coprecipitation method for selective catalytic reduction of NO with NH3 (NH3-SCR). The results showed that the NOx conversion of M-CePO4 were higher than that of CePO4, especially the Mo-CePO4 catalysts exhibited the best low-temperature activity and N-2 selectivity, the Mo-CePO4 catalysts can reach about 99% at 300 C and excellent 70 h long stability with the coexistence of SO2 and H2O. The effect of metal elements doping on physiochemical properties of catalysts were characterized by XRD, BET, Raman, TEM, XPS, H-2-TPR and NH3-TPD. SEM and TEM analysis. The results showed that part of M ions doped into CePO4 lattice resulted in lattice shrinkage. More importantly, the MOx species could not only increased the relative content of Ce3+ and surface adsorption oxygen (O & PRIME;) of M-CePO4 catalysts, but also increased the specific surface area of the catalysts. It could provide more reaction sites for active gas to promote the activation of NH3 and enhance oxidation-reduction performance. The in-situ DRIFTS results suggested that NH3 were adsorbed on both Lewis and Bronsted acid sites which can easily react with NOx gas. The NO species were adsorbed on Mo-CePO4 in the form of bidentate nitrate. The main reactants of Mo-CePO4 catalysts were NH3 linked to Lewis acid sites and bidentate nitrate species on the catalytic surface. The Eley-Rideal and Langmuir-Hinshelwood mechanisms coexisted in the SCR reaction route.