Synergistic resource recovery of hydrogen sulfide and carbon dioxide in ionic liquid deep eutectic solution: Construction <?A3B2 pi6?>and development

<sec><p indent="0mm">The efficient capture of hydrogen sulfide (H₂S) and carbon dioxide (CO₂) from acid gases is essential in the chemical industry for achieving ambitious carbon neutrality goals. Transforming H₂S and CO₂ into valuable chemicals is a critical pathway for synergistically reducing pollution and carbon emissions. This transformation not only addresses environmental concerns but also facilitates high-quality progress toward meeting carbon neutrality objectives. The hydrogenation utilization of CO₂ requires a reliable hydrogen supply to react with activated CO₂ molecules. This hydrogen donor can be derived from protons (H) in reaction medium, water (H₂O), and hydrogen atoms, produced by reaction or external supply of H₂ gas. </sec><sec> In the indirect wet oxidation desulfurization process, the H⁺ released by H₂S oxidation can be electrolyzed to produce hydrogen. Both hydrogen ions and reactive hydrogen atoms on the electrode surface are crucial precursors for the CO₂ hydrogenation reduction. Using H₂S as hydrogen donor, the functionalized solution system that integrates the indirect wet oxidative desulfurization of H₂S with the electrochemical hydrogenation reduction of CO₂ can be developed to a groundbreaking process known as CO₂ and H₂S capture and utilization (CSCU). </sec><sec> This paper critically reviews CSCU technology in different reaction mediums, including aqueous solutions, organic solvents, and ionic liquids. There are various limitations to aqueous alkaline systems, such as low product selectivity, pronounced hydrogen evolution reactions (HER), and inadequate activity of hydrogen sources. While organic systems can help mitigate some of these issues, their low Faradaic efficiency significantly hampers broader applications. In contrast, iron-based ionic liquid deep eutectic solutions (MIL-DES) present notable advantages in terms of stability, conductivity, and tunability, making them particularly suitable for the advancement of CSCU technical process. </sec><sec> Based on the latest progress in MIL-DES research, this paper proposes a novel CSCU technical process that integrates several critical reactions into one comprehensive process. The innovative process consists of non-aqueous wet oxidative desulfurization, indirect electrolysis of H₂S for hydrogen production, phase change absorption-extraction, and diaphragm-free electrochemical reduction. This multifaceted strategy effectively addresses key problems, including the efficient separation of sulfur during the H₂S oxidation and the improvement of the regeneration process of desulfurization-rich liquid. Furthermore, it enhances the directed overall efficiency of H₂S conversion and CO₂ emission reduction. </sec><sec> However, the development of the CSCU technical process faces multiple challenges. The inherent complexities of raw gas can induce side reactions that make the overall system uncontrolled. Additionally, the desulfurization liquid should possess high thermal and chemical stability to meet the need of long-term operation. Whatever oxidation desulfurization of H₂S or electrochemical reduction of CO, it is necessary to improve the reaction selectivity to match the use of raw gas. Moreover, navigating the intricacies of process control is essential for achieving optimal performance. These challenges require necessitate elevated standards for the development and application of MIL-DES and related technologies. </sec><sec> In short, the successful implementation of the CSCU process promises to deliver dual economic and environmental benefits. This innovative approach not only tackles the pressing challenges of gas capture and conversion but also significantly enhances resource utilization. By paving the way for cleaner energy solutions, the CSCU process holds immense potential and offers extensive application prospects within the energy sector. </sec>