Mechanistic insight into absorption performance assessment for SO2 by mixed ionic liquids

Abstract In this work, the thermodynamic feasibility, absorption results and molecular mechanism of capturing SO2 with mixed ionic liquids (MILs) for 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) and 1-ethyl-3-methylimidazolium chlorine ([EMIM][Cl]) were investigated for the first time. The analysis of excess enthalpy of SO2 and IL systems shows the thermodynamic feasibility of SO2 capture process by the ionic liquids (ILs). The results of free volume (Vf) and fractional free volume (FFV) of the MILs system indicating that adding [EMIM][Cl] to [EMIM][SCN] could increase the SO2 absorption capacity. Then the weak interaction between molecules was analyzed microscopically, indicating that the van der Waals force played a leading role in the process of SO2 absorption. Moreover, molecular dynamics (MD) simulations were carried out for the process of MILs absorption of SO2, and the interaction between molecules and the distribution state were further analyzed in terms of interaction energy, radial distribution functions (RDFs) and spatial distribution functions (SDFs). Overall, the study on MILs desulfurization mechanism could provide new perspective for the design of green and efficient flue gas desulfurization solvents.