Screening of Lithium-Based Salts in Non-Aqueous Electrolyte Solution of Monoethanolamine for Carbon Dioxide Capture

This study investigates the screening of lithium-based salts in non-aqueous electrolyte solutions of monoethanolamine (MEA) for potential use in integrated carbon capture and conversion (ICCC) technology. Experimental measurements of density, viscosity, nitrous oxide (N₂O) solubility, and CO₂ solubility were conducted for various lithium salts, including lithium chloride (LiCl), lithium bromide (LiBr), and lithium nitrate (LiNO₃), in MEA–dimethyl sulfoxide (DMSO) system at 303.15 K at different CO₂ pressures ranging from 344 to 1379 kPa. The results indicated that the addition of lithium salts to the amine solution significantly enhances CO₂ absorption capacity, exceeding the benchmark value of 0.5 mol CO₂/mol MEA typically reported for 5 M MEA aqueous systems. The highest CO₂ solubility in the system was observed following the order 2 M MEA + 0.5 M LiBr < 2 M MEA + 0.5 M LiNO₃ < 2 M MEA + 0.5 M LiCl in DMSO with corresponding values of 1.2213, 1.2801, and 1.3381 mol CO₂/mol MEA, respectively, identifying LiCl as the most effective additive. It was also found that using DMSO as an organic solvent greatly enhanced the CO₂ absorption capacity compared to water, evidenced by Henry's law constant determined using N₂O analogy, in addition to its lower sensible heat than water. The findings demonstrate that MEA in organic solvent shows a promising performance in CO₂ capture, with CO₂ loading higher than the industrial standard (<0.5 mol CO₂/mol MEA). Ultimately, the screening process outlined in this study serves as a foundation for future research aimed at optimizing electrolyte formulations for enhanced carbon capture efficiency.