Thermodynamics and activity coefficients at infinite dilution for organic compounds in ionic liquid 1-ethyl-2,3-dimethylimidazolium thiocyanate.

The infinite dilution activity coefficient (γ i ∞) is one of important thermodynamic parameters. In this study, new sets of experimental γ i ∞ data of 30 organic solutes in the ionic liquid 1-ethyl-2,3-dimethylimidazolium thiocyanate ([EDMIM][SCN]) have been measured in the temperature range of 353.15–383.15 K. The infinite dilution partial molar excess enthalpy (H ¯ i E , ∞) was determined from the temperature dependence of the ln γ i ∞ value, and Gibbs free energy (G ¯ i E , ∞) and entropy (T r e f S ¯ i E , ∞ ) of various solutes in [EDMIM][SCN] were calculated from the γ i ∞ value at a reference temperature T r e f = 298.15 K. The density of [EDMIM][SCN] as a function of temperature at pressure p = 101.33 kPa were measured and gas-liquid partition coefficients (K L) were determined. The interaction between the solute and the IL was quantified using the linear free energy relationship (LFER) model. Moreover, the Hildebrand's solubility parameter of [EDMIM][SCN] was obtained by the regular solution theory (RST) combined with the Flory equation by Kikic et al. modification. At 358.15 K, the selectivity (S i j ∞) for cyclohexane(i)/benzene (j), and capacity factor (k j ∞) at infinite dilution of benzene have been gotten. The results were analyzed in comparison with literature data of the ILs with [SCN]−. [Display omitted] [ABSTRACT FROM AUTHOR]