Thermodynamics and selectivity of separation based on activity coefficients at infinite dilution of various solutes in ionic liquid [DMIM][Tf2N

Abstract

The activity coefficients at infinite dilution (γi∞) is an important thermodynamic parameter for ionic liquids. By analyzing and calculating them, the possibility of ionic liquids as extractants can be estimated. The infinite dilution activity coefficients of 32 kinds of organic solutes (eg. alkyl benzenes, acetonitrile, tetrahydrofuran, n-alkanes, ethyl acetate, etc.) in ionic liquid 1-decyl-3-methylimidazole bis (trifluoromethylsulfonyl)imide [DMIM][Tf2N] were measured by gas chromatography (GLC) at six temperatures: 313.15 K, 323.15 K, 333.15 K, 343.15 K, 353.15 K, 363.15 K. Calculated some basic thermodynamic parameters such as the partial molar excess enthalpies at infinite dilution (H-iE,∞) , Gibbs free energies (G-iE,∞) and entropies (TrefS-iE,∞) were calculated at a reference temperature Tref = 298.15 K. At 323.15 K, the selectivity (Sij∞) of n-hexane (i)/benzene (j), cyclohexane/benzene, and capacity factor (kj∞) at infinite dilution of benzene have been determined. The results were analyzed in comparison to literature data for alkylimidazolium ionic liquids with [Tf2N]−.