SO₂ Poisoning, Regeneration, and Impact on Dimer-Cu Intermediates in the NH₃-SCR Reaction over Cu-Zeolites.

This study focuses on the resistance of Cu-SSZ-13 catalysts to sulfur dioxide (SO2) poisoning under selective catalytic reduction (SCR) conditions. The researchers found that catalysts with high copper (Cu) content and aluminum (Al)-rich composition exhibit superior resistance to SO2 poisoning. The high Cu content plays a crucial role in mitigating the risk of structural degradation caused by SO2 exposure. This is an important finding, as SO2 poisoning can significantly impact the performance and lifespan of SCR catalysts. The study also highlights the importance of controlling the regeneration temperature, as lower temperatures can lead to more severe secondary poisoning, while high temperatures can induce hydrothermal aging. The study also delves into the mechanisms of SO2-induced deactivation in Cu-zeolite SCR catalysts. According to the results, SO2 preferentially reacts with dimer-Cu species, particularly hydrogenated dimer-Cu, resulting in significant sulfate accumulation. This interaction inhibits the redox cycle of Cu+/Cu2+, which is essential for low-temperature activity. The researchers used a combination of experimental results and density functional theory (DFT) calculations to elucidate this mechanism. The findings of this study provide valuable insights into designing Cu-SSZ-13 catalysts with enhanced sulfur resistance. By optimizing the Cu and Al composition, it may be possible to develop catalysts that can better withstand SO2 poisoning and maintain their performance over time. Overall, this research contributes to a deeper understanding of the complex interactions between SO2 and Cu-zeolite SCR catalysts, which can inform the development of more efficient and durable catalysts for SCR applications. Link: https://pubmed.ncbi.nlm.nih.gov/40440499/