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

Abstract

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 N2 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, H2-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′) 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.