Experimental study on sulfur poisoning characteristics of Cu-SSZ-13 SCR catalyst under diesel vehicle multivalent sulfur-containing exhaust atmosphere

Abstract

In this paper, the sulfur poisoning characteristics of Cu-SSZ-13 SCR catalysts were investigated in multivalent sulfur-containing exhaust gases. The catalyst samples were sulfur poisoned at different temperatures and in different valence sulfur oxide atmospheres for a duration of 2 h. The catalyst activity was evaluated before and after sulfur poisoning in the temperature range of 150–550 °C and characterized by SO₂-TPD, NH₃–NO-titration, and DRIFTS tests. The results demonstrated that SO₃ poisoning resulted in a significantly severe reduction of SCR activity compared to SO₂ poisoning. Furthermore, it was observed that sulfur poisoning at low temperatures (250 °C) resulted in a more severe deactivation than sulfur poisoning at high temperatures (400 °C). The SO₂-TPD results demonstrated a substantial increase in the amount of sulfate produced by SO₃ poisoning, which may be attributed to the fact that SO₃ is more susceptible to active site binding to form sulfate species and that SO₃ poisoning produced aluminum sulfate species, which were not present in SO₂ poisoning. NH₃–NO-titration and DRIFTS results demonstrated that low-temperature sulfur poisoning and the presence of SO₃ resulted in a substantial decrease in the number of active sites, where ZCuOH was more susceptible to sulfur poisoning compared to Z₂Cu.