Brønsted base/acid cycle: Boosting the directional conversion of hydrogen sulfide in chelated iron-based deep eutectic solvents

• Published in: Fuel (Guildford) Vol. 379; p. 132980
• Main Authors: Bai, Wenxuan, Chen, Jinxiang, Liu, Fen, Gu, Zhiping, Zhong, Yan, Yu, Jiang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2025
• Subjects: Catalytic oxidation; Deep eutectic solvent; Directional transformation; Hydrogen sulfide; Iron-based ionic liquid; Directional transformation; IL; EDTA; Iron-based ionic liquid; Hydrogen sulfide; Bmim; PEG200; Catalytic oxidation; Deep eutectic solvent; DES; Fe-DES; Fe(Ⅲ)EDTA; Fe-DES-MDEA; MDEA; Fe-IL
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.132980

[Display omitted] •Fe-DES-MDEA surpasses the limitations of conventional Fe-IL reactivity.•Fe-DES-MDEA exhibits outstanding desulfurization-regeneration cyclability.•MDEA/[HMDEA]+ interconversion substantially enhances the cycling of Fe(III)/Fe(II).•Vacating cage to change bird leads to the directional conversion of H2S to sulfur. The removal of hydrogen sulfide (H2S) during fossil fuel extraction is crucial for mitigating environmental impact and improving fuel quality. Recent advancements in non-aqueous iron-based ionic liquid desulfurization technology have overcome some limitations of aqueous systems, such as side reactions. However, its lower sulfur capacity and reaction activity have limited its industrial development. In this work, a chelated iron-based deep eutectic solvent (Fe-DES) was synthesized by combining a chelated iron-based ionic liquid (BmimFeEDTA) with PEG200. Subsequently, MDEA was introduced into Fe-DES to form Fe-DES-MDEA for the oxidative desulfurization of H2S. Fe-DES-MDEA demonstrated enhanced desulfurization and regeneration capabilities when compared to conventional wet oxidative desulfurizers. Notably, Fe-DES-MDEA maintained consistent desulfurization efficiency over five cycles, effectively converting hydrogen sulfide to sulfur without producing by-salts. Characterization techniques such as FT-IR, Py-IR, and CV were used to analyze the microstructure and catalytic activity of Fe-DES-MDEA. Additionally, DFT calculations indicated that the transition of MDEA/[HMDEA]+ facilitated the cycling performance of Fe(III)/Fe(II) in the oxidation of H2S. Furthermore, the molecular cage of deep eutectic solvent mitigated excessive O2 activation, enabling the directed conversion of H2S, akin to the mechanism of “vacating cage to change bird”. Consequently, Fe-DES-MDEA shows promising potential for effective hydrogen sulfide removal in fuel gas processing applications.