Liquid‐liquid phase split in ionic liquid + toluene mixtures induced by CO 2

High pressure carbon dioxide was dissolved in ionic liquid + toluene mixtures to obtain the conditions of pressure and composition where a liquid‐liquid phase split occurs at constant temperature. Ionic liquids (ILs) with four different cations paired with the bis(trifluoromethylsulfonyl)imide ([Tf 2 N] − ) anion were selected: 1‐hexyl‐3‐methylimidazolium ([hmim] + ), 1‐hexyl‐3‐methylpyridinium ([hmpy] + ), triethyloctylphosphonium ([P 2228 ] + ), and tetradecyltrihexylphosphonium ([P 66614 ] + ). The solubility of CO 2 was measured in the liquid mixtures at temperatures between 298 and 333 K and at pressures up to 8 MPa, or until the second liquid phase appeared, for initial liquid phase compositions of 0.30, 0.50, and 0.70 mole fraction of IL. Ternary isotherms were compared with the binary solubility of CO 2 in each IL and pure toluene. The lowest pressure for separating toluene in a second liquid phase was achieved by decreasing the temperature of the system, increasing the amount of toluene in the initial liquid mixture and using [hmim][Tf 2 N]. © 2015 American Institute of Chemical Engineers AIChE J , 61: 2968–2976, 2015