The CO2/CH4 gas mixture solubility in ionic liquids [Bmim][Ac], [Bmim][BF4] and their binary mixtures

Design of suitable solvent is important to separate CO2 from natural gas. Ionic liquids, known as “green solvents”, are proper alternatives for conventional solvents in gas sweetening process. In this work, the abilities of ionic liquids 1-butyl-3-methylimidazolium acetate ([Bmim][Ac], 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and their binary mixtures are experimentally investigated for CO2 separation from CH4. The solubility of CO2/CH4 mixtures (25/75 mol%, 50/50 mol% and 75/25 mol%) in ionic liquids [Bmim][Ac], [Bmim][BF4] and their binary mixtures containing {75 w% [Bmim][Ac] + 25 w% [Bmim][BF4], 50 w% [Bmim][Ac] + 50 w% [Bmim][BF4] and 25 w% [Bmim][Ac] + 75 w% [Bmim][BF4]} are measured at (298.15, 308.15 and 318.15) K for pressures up to 5.0 MPa. The ideal and real CO2/CH4 solubility selectivities for the studied ionic liquids are also reported. Finally, the cubic plus association (CPA) equation of state has been applied to predict the experimental solubilities.