Effect of an ionic liquid (IL) cation on the ternary system (IL plus p-xylene plus hexane) at T=298.15 K

Liquid-liquid equilibrium data are presented for mixtures of {ionic liquid (butyl(2-hydroxyethyl)dimethylammonium tetrafluoroborate, or hexyl(2-hydroxyethyl)dimethylammonium tetrafluoroborate, or 1,3-dihexyloxymethylimidazolium tetrafluoroborate) + p-xylene + hexane} at 298.15 K. The alkyl chain length, hexyl vs butyl, has an influence on the separation process: the selectivities are statistically higher for the shorter alkyl chain. Unfortunately, polar 1,3-dihexyloxymethylimidazolium tetrafluoroborate is shown to have a very low selectivity. The nonrandom two liquid (NRTL) model was successfully used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems. The average mean square deviation phase composition error is 0.018. The results are discussed in terms of the selectivity of separation of related systems. The data presented here indicate the usefulness of butyl(2-hydroxyethyl)dimethylammonium tetrafluoroborate as a solvent for the separation of aromatic and aliphatic hydrocarbons using solvent extraction.