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

Abstract

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.