Experimental solubility and thermodynamic modeling of CO2 in four new imidazolium and pyridinium-based ionic liquids

• [PMPY][Tf2N] was found to be a promising ionic liquid for CO2 capture applications.
• The effect of changing the anion and cation on CO2 solubility was investigated.
• Enthalpy, entropy and Henry's law constant for the ionic liquids were evaluated.
• Solubility Modeling was done using PR-EoS and NRTL model.
• Density measurements were performed at different temperatures.

The solubility of carbon dioxide (CO2) in four ionic liquids, 1-ethyl-3-methylimidazolium L-(+)-lactate ([EMIM][LACTATE]), 3-methyl-1-propylpyridinium bis[(trifluoromethylsulfonyl]imide ([PMPY] [TF2N]), 1-(4-sulfobutyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([(CH2)4SO3HMIm][TF2N]), 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate ([(CH2)4SO3HMIm][HSO4]), has been experimentally studied using the gravimetric microbalance method. (Carbon dioxide + IL) systems were studied at (313.15, 323.15 and 333.15)K over a pressure range of 100 mbar–20000 mbar. Experimental densities, Henry's Law constants, entropies and enthalpies of absorption were also reported. The results obtained showed that CO2 solubility diminished in the following sequence: [PMPY][Tf2N]>[EMIM][LACTATE] > [(CH2)4SO3HMIm][TF2N] > [(CH2)4SO3HMIm][HSO4]. It was found that [PMPY][Tf2N] shows comparable CO2 solubility with ionic liquids that are considered promising such as [HMIM] [Tf2N], which makes this ionic liquid an attractive solvent for gas separation processes. CO2 solubility in the ionic liquids was well correlated using Peng–Robinson equation of state with a quadratic mixing rule and the nonrandom two-liquid (NRTL) model.