The promoting effects of amorphous CePO4 species on phosphorus-doped CeO2/TiO2 catalysts for selective catalytic reduction of NOx by NH3

A series of phosphorus-doped Ceo(2)/TiO2 catalysts were prepared by impregnation method and the effects of P on NH3-SCR performance over CeO2/TiO2 were investigated. The P-doped catalysts showed much better deNO(x) performance than Ce-10/Ti catalyst. It was found that the optimal phosphorus loading was 3 wt.% (calculated as P2O5). The CeioP(3)/Ti catalyst also exhibited excellent resistance to H2O. The samples were characterized by BET, XRD, XPS, NH3-TPD, H-2-TPR and in-situ DRIFT studies. It was found that the ratio of surface Ce3+ and surface adsorbed oxygen species were promoted by phosphorus doping, thus the transfer of surface oxygen and the regeneration of active sites could be accelerated accordingly. Moreover, it was confirmed that the amorphous CePO4 appeared with excellent redox property after the doping of phosphorus. The amorphous CePO4 species could promote NH3-SCR activity by activating NH4+ species on the Bronsted acid sites of phosphate radical, forming -NH2 intermediates to react with gaseous NO via an Eley-Rideal mechanism.