Transformation of H2S in In Situ Landfill Gas Deoxygen with Pt/γ-Al2O3 as the Catalyst and Its Impact on Catalyst Activity

Catalytic deoxygenation is an effective technique for oxygen removal from landfill gas (LFG) in industry, thereby upgrading LFG to biomethane as a viable alternative energy source. However, LFG typically contains trace amounts of H2S, which may potentially exert adverse effects on the catalytic deoxygen reaction. To clarify this issue and provide a theoretical support for industrial practice, we simulated the actual catalytic deoxygen reaction of LFG in the presence of 200 ppm of H2S. Different from the conventional belief that H2S is a catalyst poison in various reactions, the present study has discovered that trace amounts of H2S exhibit a promotional effect on the catalytic deoxygen activity of the Pt/gamma-Al2O3 catalyst. Characterizations and theoretical calculations reveal the transformation behavior of H2S and its promotion mechanism. It is demonstrated that H2S is adsorbed on Pt sites, undergoing multistep oxidation and ultimately forming SO42-. A portion of SO42- adsorbed on Pt sites is transferred to the support, while another portion is reduced to SO2 and enters the gas phase. The SO42- temporarily present on Pt sites significantly promotes the heterolytic cleavage of the C-H bond of methane, thereby enhancing the Pt/gamma-Al2O3 catalyst deoxygen activity.