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.