Improved activity and significant SO2 tolerance of samarium modified CeO2-TiO2 catalyst for NO selective catalytic reduction with NH3

The Sm doped CeO2-TiO2 mixed oxide catalyst, which exhibited excellent activity and tolerance to H2O and SO2 in the NH3-SCR reaction, was synthesized. The reasons for the high activity and SO2 resistance of the catalyst were investigated by a series of characterization. The H2-TPR and O2-TPD results suggested that the reducibility and oxygen storage capacity (OSC) of CeTi catalyst were promoted by the addition of Sm species, which was beneficial for improving the activity of catalyst. The in situ DRIFTS results revealed that the adsorptive ability of NOx species and activation ability of NH3 were enhanced by Sm doping, which was also propitious to enhance the activity. XPS combined with DFT calculated results confirmed that the transfer of electron by Sm2++Ce4+⇌Sm3++Ce3+ circles occurred in the SmCeTi catalyst. The redox circles may be the reason of the good SO2 tolerance of the SmCeTi catalyst, for which suppressed the electron transferring from adsorbed SO2 to Ce4+. Through in situ DRIFTS and TG-DSC results, it can be concluded that the sulphation of catalyst was lowered by samarium doping into CeTi catalyst. Consequently, the SmCeTi catalyst exhibited significant SO2 tolerance ability.