Extraction of Benzene from Aliphatic Compounds Using Commercial Ionic Liquids as Solvents: Study of the Liquid–Liquid Equilibrium at T = 298.15 K

In this paper, the liquid extraction of benzene from aliphatic compounds (heptane, octane, cyclooctane, and methylcyclohexane) using commercial ionic liquids (ILs; 1-propyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, [PMim][NTf2], and 1-butyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, [BMim][NTf2]) as solvents was studied. The liquid–liquid equilibrium (LLE) data for five ternary systems (aliphatic compound + benzene + IL) are reported at T = 298.15 K and atmospheric pressure. The cloud point method was used to determine the solubility curves, and the tie-line compositions were obtained by density measurements. From the experimental LLE data, the selectivity and the solute distribution ratio were calculated. The degree of consistency of the tie-lines was tested using the Othmer–Tobias equation, and the experimental LLE data were correlated using nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) thermodynamic models. Moreover, a systematic study about the influence of the size of the aliphatic and IL on the aromatic extraction was carried out.