Mitigating SO2 poisoning during CO oxidation over Pt/Al2O3 catalysts via sulfur spillover from highly under-coordinated platinum to the Al2O3 support

SO 2 in the sintering flue gas severely inhibits the CO oxidation performance of commercial Pt/Al 2 O 3 catalysts. However, the major poisoning mechanism of SO 2 on Pt/Al 2 O 3 in CO oxidation in the presence of H 2 O remains to be elucidated. Here, Pt/Al 2 O 3 was pretreated with different reducing atmospheres at high temperatures. Among these, the catalyst pretreated with a CO atmosphere at 600 °C (denoted as Pt/Al 2 O 3 -CO-600) exhibited superior CO oxidation performance and enhanced sulfur resistance in the presence of both H 2 O and SO 2 . The combination of XPS, HAADF-STEM, TG-MS, SO 2 oxidation test, and in-situ DRIFTS reveal that the Pt species on Pt/Al 2 O 3 -CO-600 transformed from Pt oxide clusters to metallic Pt nanoparticles. This transformation enhanced SO 2 adsorption and reactivity, leading to increased sulfate accumulation. Despite the high SO 2 reactivity and sulfate content, in-situ DRIFTS revealed that the CO reaction of Pt/Al 2 O 3 -CO-600 was less hindered by SO 2 and the sulfated Al 2 O 3 . This is attributed to the high ratio of the under-coordinated (UC) Pt sites in Pt/Al 2 O 3 -CO-600, which promotes the reaction intermediates spillover from Pt site to Al 2 O 3 compared to the Pt/Al 2 O 3 . This phenomenon was positively correlated with the sulfur resistance of reduced catalysts. Accordingly, the UC site contributes to the spillover of sulfate intermediate (H 2 SO 4 ), reducing the CO reactivity loss of Pt/Al 2 O 3 due to the intermediate coverage. This study elucidates that the primary poisoning pathway of Pt/Al 2 O 3 in the presence of H 2 O and SO 2 is the difficulty of sulfate intermediate spillover.