Contrasting Roles of H2S, SO2, and COS Impurities in Enhanced or Inhibited Propane Oxidation over Pt/TiO2 Catalyst

Industrial sulfur-containing exhaust streams severely compromise the oxidation removal of harmful air pollutants, leading to excessive emissions and thus posing significant risks to air quality. Even trace amounts of gaseous sulfur impurities can poison catalysts, yet their actual impact remains controversial due to their diversity and dynamic interconversion under realistic conditions. Herein, we systematically investigate the effects of three representative sulfur impurities (H2S, SO2, and COS) on propane (C3H8) oxidation as a probe molecule over a Pt1/TiO2 catalyst. Distinct and temperature-dependent roles are observed: SO2 strongly promotes C3H8 oxidation in the whole temperature range, whereas H2S and COS inhibit conversion below a transition temperature (TT = 269 °C) but become promotional at higher temperatures. Combined spectroscopic and theoretical analyses reveal that gaseous sulfur impurities transform into surface sulfate configurations that modulate oxygen reactivity and govern C3H8 reaction pathways. Specifically, SO2 forms Pt-O-O-SO3 motifs that enhance Pt-O reactivity and facilitate C-H bond activation, while H2S and COS generate Pt-O-SO3 structures that suppress Pt-O reactivity at low temperatures but evolve into an active state at elevated temperatures. These results demonstrate that catalytic behavior is jointly determined by sulfur speciation and temperature-dependent surface reconstruction, providing a mechanistic framework for designing catalysts for volatile organic compounds (VOCs) abatement in sulfur-containing exhaust streams.