Ternary liquid–liquid equilibria of trifluorotris(perfluoroethyl)phosphate based ionic liquids + benzothiophene + heptane

• Ternary liquid–liquid equilibria for [FAP]− anion based ILs + benzothiophene + heptane.
• The influence of ionic liquid cation structure on phase diagrams is discussed.
• High selectivity for separation of heptane/benzothiophene is observed.

Ionic liquids: (4-(2-methoxyethyl)-4-methylmorpholinium trifluorotris(perfluoroethyl)phosphate, ethyldimethyl-(2-methoxyethyl)ammonium trifluorotris(perfluoroethyl)phosphate and 1-(2-hydroxyethyl)-3-methyl-imidazolium trifluorotris(perfluoroethyl)phosphate were investigated in separation of heptane/benzothiophene mixture. Three systems of ternary liquid–liquid equilibria containing studied ionic liquids + benzothiophene + heptane have been determined at T  =  308.15 K. All systems show high solubility of benzothiophene in the ionic liquid and low solubility of heptane. The experimental results have been correlated using of NRTL model. The selectivity and the solute distribution ratio were calculated for all systems. High selectivities and solute distribution ratios were obtained for all systems. Additionally the densities and the viscosities of one studied ionic liquid were measured.