Prediction of CO2 solubility in ionic liquids with [HMIM] and [OMIM] cations by equation of state

Abstract

The discovery of various ionic liquids which can effectively absorb CO2 from flue gases motivated us to study the phase behavior of carbon dioxide with ionic liquids. A convenient thermodynamic model such as an equation of state is required for predicting structure–property relationship. In this study, Perturbed Hard Sphere Chain Equation of State (PHSC) has been selected to model CO2 absorption in a series of ionic liquids including 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF4], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF6], 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [HMIM][Tf2N], 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF4], 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM][PF6] and 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [OMIM][Tf2N]. Using three molecular-based parameters plus regression of only one binary interaction parameter is sufficient for PHSC EoS to achieve noticeable modeling purposes.