Evaluation of the predictive capability of ionic liquid force fields for CH4, CO2, NH3, and SO2 phase equilibria

Abstract

Molecular dynamics simulations were performed to systematically compare four all-atom classical ionic liquid force fields and provide recommendations for the appropriate selection of an ionic liquid force field for the calculation of Henry's constants of gases. Four solutes of varying polarity, viz., CH4, CO2, NH3, and SO2 were investigated. The ionic liquids considered in this work contain the same cation, 1-n-butyl-3-methylimidazolium [C4mim]+ paired with four different anions chloride Cl−, methylsulfate [MeSO4]-, dicyanamide [DCA]-, and bis(trifluoromethanesulfonyl)imide [NTf2]-. The calculations were performed at three temperatures of 333, 353, and 373 K to enable the computation of enthalpies and entropies of absorption. Based on a comparison of the predicted results with those available in the literature, it was observed that the recently developed virtual-site ionic liquid force field tends to exhibit an overall better agreement with the published data in comparison to other force fields. Our results further indicate that, in general, SO2 is the most soluble gas due to the strongest interaction with ionic liquids, followed by NH3, CO2 and CH4.