Thermodynamic modeling of CO2 absorption in 1-butyl-3-methylimidazolium-based ionic liquids

There are a number of methods to capture the carbon dioxide; among them ionic liquids are the recent magical solvents as gas absorption agents. To understand and predict the phase behavior of CO2 + ionic liquid mixtures, a convenient thermodynamic model such as an equation of state is required. 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-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], 1-butyl-3-methylimidazolium methylsulfate [BMIM][MeSO4], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl − mide) [BMIM][Tf2N]. Three molecular-based parameters, i.e. hard-sphere diameter, the non-bonded interaction energy and the number of segments per molecule have been employed as scaling constants. It is the advantage of PHSC EoS that works satisfactorily by regression of only one binary interaction parameter. The binary interaction parameter is enhanced with rising temperature due to the lower interaction of CO2 with ionic liquids.