Effect of SO2 introduction into CeO2 on its surface acidity and redox property for the selective catalytic reduction of NO with NH3

Gaseous SO2 acidification Ce-based catalysts were prepared and used for the selective reduction of NO with NH3. S–Ce was obtained by direct anaerobic sulfation of CeO2, while H–S–Ce was obtained by reduction of CeO2 and then anaerobic sulfation. Both S–Ce and H–S–Ce exhibited excellent SCR activity, and the S–Ce catalyst displayed the best catalytic performance. The activity of CeO2 was below 30% in the whole temperature range, while the activity of S–Ce reached 90% at 250 °C and remained 100% at 300–450 °C. Anaerobic sulfation could enhance the redox and surface acidity of the S–Ce catalyst. The acid sites favored NH3 adsorption, while the H–S–Ce catalyst exhibited considerable surface acidity, but the redox performance was weakened by stable sulfate. The reaction mechanism showed that a huge number of NH3 species adsorbed on S–Ce catalysts were consumed by NO gas. The present nitrate species and NO2 were removed. The SCR reaction followed E–R and L–H mechanisms for S–Ce. A large number of NH3 species on H–S–Ce were cleared by NO, and NO could hardly adsorb on its surface. The SCR reaction followed the E–R mechanism.