Effect of SO2 on NH3 oxidation over a Cu-SAPO-34 SCR catalyst

Abstract

The impact of SO₂ on NH₃ oxidation, an undesired side reaction that can occur during NH₃-SCR, was studied using Cu-SAPO-34. Based on kinetic analysis, monomeric Cu⁺⁺ was active toward NH₃ oxidation. In terms of the SO₂ effect, significant loss in NH₃ oxidation activity was observed at temperatures below 350 °C. However, at higher temperatures, SO₂ had no significant effect on NH₃ oxidation, which corresponds to the lack of an observed effect on SCR performance. 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.