Fe-oxide/Al₂O₃ for the enhanced activity of H₂S decomposition under realistic conditions: Mechanistic studies by in-situ DRIFTS and XPS

Fe-oxide nanoparticles (less than 2 nm) were evenly dispersed onto mesoporous Al₂O₃ beads, and the structure was used as an adsorbent and catalyst for removing H₂S. The Fe-oxide enhanced the removal efficiency of H₂S molecules at room temperature and suppressed SO₂ emission into the gas phase upon thermal treatment of the H₂S-covered substrate. Compelling evidence is provided by in-situ DRIFTS and XPS that Fe-oxide not only catalyzes the conversion of H₂S to S₈, as previously suggested, but also facilitates the formation of SO₄²⁻ species on the surface of Fe-oxide/Al₂O₃. A spill-over process of SO₄²⁻ from Fe-oxide to Al₂O₃ at their interfacial site was proposed. The removal efficiency of the SO₄²⁻-poisoned surfaces could be recovered by water cleaning. This study clearly provides molecular level information about the problems one can face when supported Fe-oxide catalysts are used as H₂S-removing agents in field applications, and details regarding how one can avoid such problems.