Comparison of the poisoning mechanism of different zinc species on Nb-Doped Ce-Ti SCR catalysts

The effect of different Zn species (ZnSO4, ZnCl2, and ZnO) on Nb-doped Ce-Ti catalyst (CNT) was explored with XRD, N-2 physisorption, NH3-TPD, H-2-TPR, XPS, in situ DRIFTS and DFT calculation. The experimental results show that the deactivation rate of CNT by different Zn species was in the order: CNT-ZC > CNT-ZO > CNT-ZS. Nb doping enhanced the acidity of Ce-Ti catalyst and protected Ce active sites from different Zn species. After different Zn species were loaded on CNT, its specific surface area decreased, and the acid sites were occupied. The results from in situ DRIFTS demonstrated that, after anion poisoning, anions (SO42-, O2-, and Cl-) would create new NH3 adsorption sites while theoretical calculations also indicated that NH3 adsorption was enhanced by the poisoning of anions, but the activation of adsorbed NH3 was more difficult. Finally, in situ DRIFTS reveals that the SCR reaction on CNT is still under both E-R and L-H mechanisms.