Evaluation and correlation of separation heptane/ethanol with ionic liquids. Ternary liquid-liquid phase equilibrium data

Urszula Domańska-Żelazna , Anna Wiśniewska , Zbigniew Dąbrowski , Mikołaj Więckowski

Abstract

The objective of this work was to explore the feasibility of separation of heptane from ethanol using ammonium-based and imidazolium-based ionic liquids (ILs). With this aim, the liquid–liquid phase equilibrium (LLE) for four ternary systems of {IL (1) + ethanol (2) + heptane (3)} at temperature T = 313.15 K and pressure p = 101 kPa were determined. The synthesis of new ammonium-based ionic liquid (IL), N-benzyl-N-dimethyl-N-tetradecylammonium vannilliate, [NBz,1,1,14][Van] has been presented and used in LLE measurements. The results of selectivity of separation were compared to popular N-octyl-N-triethylammonium bis{(trifluoromethyl)sulfonyl}imide, [N8,2,2,2][NTf2], and two imidazolium-based ILs: 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM[TFA] and 1-hexyloxymethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [C6H13OCH2MIM][NTf2]. The [EMIM[TFA] IL showed excellent results in terms of selectivity and solute distribution ratio. On the basis of the results, the intermolecular interactions of the chosen ILs and solvents were discussed. The data presented here shows that [NBz,1,1,14][Van] reveals lower selectivity for the heptane/ethanol separation than the other used ILs. It allows expanding our knowledge about nature of the [NBz,1,1,14][Van], influence of polar functional groups and alkane chain in the cation on thermodynamical properties of [NBz,1,1,14][Van]. All experimental data were well correlated with the NRTL model.