Sulfur poisoning of SCR catalysts
Yasser Jangjou, University of Houston
The impact of SO2 on NH3 oxidation and SCR was studied over Cu-SAPO-34 and Cu-SSZ13. In terms of the SO2 effect, significant loss in NH3 oxidation activity was observed at temperatures below 350 Â°C. However, at higher temperatures, SO2 had no significant effect on NH3 oxidation. Temperature-programmed-desorption (TPD) data obtained after NH3 and SO2 exposures demonstrate that SO2 inhibited monomeric copper NH3 oxidation activity through formation of ammonium sulfate, whose formation was catalyzed by the Cu. The monomeric copper regained NH3 oxidation activity after ammonium sulfate decomposed. SCR activities suffered similar losses, and were found to be for the same reasons. This shows that SO2 impacts redox properties, but does not rule out site blocking via ammonium sulfate formation.