Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

In the present paper, a study on the influence of the alkyl chain length in N-alkyl-triethylammoniumbis(trifluoromethylsulfonyl)imide ionic liquids, [NR,222][Tf2N] (R = 6, 8 or 12), on the excess molar enthalpyat 303.15 K and excess molar volume within the temperature interval (283.15.338.15 K) of ionic liq-uid + methanol mixtures is carried out. Small excess molar volumes with highly asymmetric curves (i.e.S-shape) as a function of mole fraction composition were obtained, with negative values showing in themethanol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length ofthe ammonium cation of the ionic liquid and decrease with temperature. The excess enthalpies of selected binary mixtures are positive over the whole composition range and increase slightly with the length ofthe alkyl side-chain of the cation on the ionic liquid. Both excess properties were subsequently correlatedusing a Redlich.Kister-type equation, as well as by using the ERAS model. From this semipredictive modelthe studied excess quantities could be obtained from its chemical and physical contribution. Finally, theCOSMOThermX software has been used to evaluate its prediction capability on the excess enthalpy forinvestigated mixtures at 303.15 K and 0.1 MPa. From this work, it appears that COSMOThermX method predicts this property with good accuracy of approx. 10%, providing at the same time the correct orderof magnitude of the partial molar excess enthalpies at infinite dilution for the studied ILs.