Effect of hydrogen addition on SO2 tolerance of silver–alumina for SCR of NO with propane

The effect of H2 addition and silver loading on the SO2 tolerance and de-NOx performance of Ag/Al2O3 for the C3H8-SCR reaction was investigated by catalytic testing combined with various characterization results. SO2 tolerance is improved by H2 cofeeding as well as an increase in Ag loading of Ag/Al2O3. In situ IR results shows that the reaction of sulfates on Ag-containing sites with H2 results in the desorption of SO2 or migration of the sulfates to alumina surface. TPD/TRP results show that sulfate desorption in He or in H2 occurs at lower temperature for the higher loading sample. Combined with UV–vis and in situ IR results, these findings suggest that the higher SO2 tolerance of high loading catalyst for the H2–C3H8-SCR reaction is caused by the higher rate of sulfate reduction that is more advantageous over partially reduced silver sites than over Ag+ sites.