Metal-free ionic liquids serve as integrated catalyst-solvent systems for green H2S oxidation to sulfur by O2

Abstract

The removal of hydrogen sulfide (H2S), a highly toxic and corrosive component from fossil fuel processing and utilization, constitutes a critical environmental challenge in the clean utilization of carbon resources. The use of O2 as a green oxidant for its catalytic oxidation represents a promising and sustainable removal strategy. While most current gas–liquid systems employ chelated iron catalysts and exhibit favorable catalytic activity, they suffer from inherent limitations such as sluggish regeneration of Fe(II) and the chemical instability of organic ligands—key obstacles hindering their practical deployment. In this work, we report that basic imidazolium acetate ionic liquids (ILs) can efficiently catalyze the oxidation of H2S to elemental sulfur using molecular O2 under mild conditions, without requiring additional catalysts or additives. Detailed study revealed that imidazolium acetate ILs establish an optimal alkaline environment that promotes both the effective capture and activation of H2S, facilitating its selective oxidation. Moreover, the integrated "solvent-catalyst" design simplifies downstream processing, enabling facile catalyst recovery through simple solid-liquid separation and dehydration. The system maintains high performance over five consecutive cycles without noticeable deactivation, underscoring its robust recyclability. We hold the view that this work not only presents a novel strategy for the coupling of H2S capture and resource utilization, but also serves as a valuable reference for the future development of green, low-energy-consumption and resource-recovery gas purification technologies.