Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: in situ Cu and S K-edge XAS studies

Abstract

In situ Cu and S K-edge X-ray absorption spectroscopy (XAS) was used for the investigation of sulfur-poisoned and regenerated Cu-SSZ-13 selective catalytic reduction (SCR) catalysts. Highly dispersed sulfur in the oxidation state +6 was found in the catalysts. Even though a similar amount of sulfur was deposited in the catalysts poisoned at both 200 and 500 °C, a higher fraction of sulfur-free Cu species was seen for the catalyst poisoned at the higher temperature. Regeneration at 550 °C resulted in more sulfur-free Cu species in the catalyst poisoned at 500 °C, even though a higher amount of sulfur was detected in this catalyst compared to the regenerated catalyst poisoned at 200 °C. Inconsistencies between the amount of sulfur and the fraction of sulfur-free Cu species were attributed to the additional sulfur storage at sites that do not involve Cu. It was suggested that increased temperature of poisoning may facilitate the formation of Al sulfates along with Cu sulfates. These results provide the next step in detailed understanding of sulfur poisoning and regeneration of Cu-SSZ-13 catalysts.