Vapor-Liquid Equilibrium of Binary Systems Containing Cyano-based Ionic Liquids and CO2: SAFT-γ GC EoS Modeling

The unusual thermodynamic behavior of ionic liquid (IL)+CO2 mixtures has challenged their theoretical modeling. In this paper, a SAFT-γ equation-based group contribution method (SAFT-γ GC EoS) is used to predict the Vapor-Liquid Equilibrium (VLE) of these mixtures. The binary systems containing CO2 and 1-butyl-3-methyl-imidazolium-thiocyanate ([bmim][SCN]),1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]), 1-hexyl-3-methylimidazolium dicyanamide ([hmim][DCA]), 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]), 1-butyl-3-methylimidazolium tricyanomethanide ([bmim][TCM]) or 1-hexyl-3-methylimidazolium tetracyanoborate ([hmim][TCB]) are divided into the functional groups of CO2, cyano-based anion, CH2, CH3 and imidazolium-based cationic head. Some new SAFT-γ parameters are optimized at temperatures from 283.15 to 373.15 K and pressures up to about 20 MPa. The observation of an average error of 1.86% between experimental and estimated bubble pressures indicates the desirable performance of SAFT-γ GC EoS to predict the VLE of CO2+imidazolium-, cyano-based ionic liquid mixtures.