Deactivation mechanisms of Cu–Zn–Al₂O₃ in CO₂ hydrogenation induced by SO₂ exposure

The presence of sulfur compounds, particularly SO₂, is known to significantly degrade the performance of metal-based catalysts, posing a significant challenge in CO₂ hydrogenation reactions. In this study, we systematically investigate the impact of SO₂ on Cu–ZnO–Al₂O₃ catalysts for CO₂ hydrogenation to elucidate the deactivation mechanisms. Our findings reveal that SO₂ adsorption leads to the formation of surface sulfate and sulfite species, which effectively block active sites, impeding the adsorption and activation of reactants. Moreover, SO₂ exposure inhibits CO desorption, further compromising catalytic efficiency. In parallel, progressive sulfidation of Cu and ZnO results in the formation of catalytically inactive CuS, Cu₂S, and ZnS phases, ultimately leading to complete catalyst deactivation. These results highlight the dual role of sulfur species in both surface passivation via sulfates/sulfites deposition and irreversible structural transformation via sulfidation. Our study provides new insights into the SO₂-induced catalyst deactivation in CO₂ hydrogenation and offers a theoretical foundation for enhancing CO₂ hydrogenation reactions, with implications for optimizing environmentally sustainable catalytic systems in industrial applications.