Molecular Insights into SO2 Absorption by [EMIM][Cl]-Based Deep Eutectic Solvents

Deep eutectic solvents (DESs) as promising green solvents have been proposed for the removal of SO2 from fuel gases. In this work, an efficient SO2 absorption strategy based on three 1-ethyl-3-methylimidazolium chlorine ([EMIM]­[Cl])-based DESs, that is, [EMIM]­[Cl]–ethylene glycol, [EMIM]­[Cl]–triethylene glycol, and [EMIM]­[Cl]–acetamide DESs, was investigated. A comparison of the predicted absorption efficiency via molecular dynamics (MD) and that obtained from experimental results is used to validate the simulated results. Then, the interaction energy and radial and spatial distribution functions are calculated based on the MD simulation results to provide molecular insights into the separation mechanism. The hydrogen bonding and van der Waals interactions between molecules and SO2 were investigated by quantum chemical calculations. The results demonstrate that the anion ([Cl]−) plays a significant role in the absorption process. As a further step, a modeling method for SO2 absorption and DES recovery based on Aspen Plus is established. Under optimal operating conditions, the SO2 absorption ratio exceeds 99.6%, and the DES recovery ratio is 99.9%. DESs, as a new type of absorbent, will provide new insights for the sustainable development of the green chemical industry.

低共熔溶剂（Deep eutectic solvents, DESs）作为一类极具应用潜力的绿色溶剂，已被提出用于脱除燃料气中的二氧化硫（SO₂）。本研究针对三种基于1-乙基-3-甲基咪唑氯盐（[EMIM][Cl]）的低共熔溶剂，即[EMIM][Cl]–乙二醇、[EMIM][Cl]–三乙二醇以及[EMIM][Cl]–乙酰胺型低共熔溶剂，开发了一种高效的SO₂吸收策略并开展了相关研究。为验证模拟结果的可靠性，本研究将通过分子动力学（molecular dynamics, MD）模拟得到的吸收效率预测值与实验实测结果进行了对比。基于分子动力学模拟结果，本研究计算了分子间相互作用能、径向分布函数与空间分布函数，从分子层面揭示了该分离过程的作用机制。此外，通过量子化学计算，本研究探究了各组分分子与SO₂之间的氢键作用及范德华相互作用。研究结果表明，阴离子([Cl]⁻)在吸收过程中发挥了关键作用。在此基础上，本研究基于Aspen Plus软件构建了SO₂吸收与DES回收的建模方法。在最优操作工况下，SO₂吸收率超过99.6%，DES回收率可达99.9%。作为一类新型吸收剂，低共熔溶剂将为绿色化工行业的可持续发展提供全新的研究思路。