A molecular dynamics study of the solvation of carbon dioxide and other compounds in the ionic liquids [emim][B(CN)4] and [emim][NTf2]

Abstract

In this paper, we calculate solvation free energies of several compounds in ionic liquids. These free energies are used to compute properties such as Henry's law constants and activity coefficients, generally required in the design of environmentally sustainable processes. It is known, for instance, that carbon dioxide from combustion is one of the main sources of anthropogenic greenhouse gases. Recently, the propensity of the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate ([emim][B(CN) 4 ]) for the physisorption of CO 2 has been reported, which makes it a potential solvent for carbon capture. In the present work, molecular dynamics simulations of the solvation of CO 2 in ionic liquids [emim][B(CN) 4 ] and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([emim][NTf 2 ]) are carried out both at infinite dilution and at high concentrations. A systematic study is performed by comparing several force fields and assessing the efficacy of simplifications in the simulations by using rigid-body dynamics and pairwise electrostatics. Our results confirm recent experimental observations that, for a given volume of solvent, lower pressure is required to absorb a certain amount of CO 2 in [emim][B(CN) 4 ] than in other ionic liquids.