Journal of Chemical Thermodynamics, Vol.138, 116-126, 2019
The molar surface quasi-Gibbs energy and its application to the binary mixtures of 1-(2-methoxyethyl)-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide [MOEMIM][NTf2] with methanol
The IL (ionic liquid) 1-(2-methoxyethyl)-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide [MOEMIM][NTf2] was prepared and confirmed by H-1 NMR (H-1 nuclear magnetic resonance) spectroscopy and C-13 NMR (C-13 nuclear magnetic resonance) spectroscopy. The density and surface tension for the binary mixtures of [MOEMIM][NTf2] with methanol and ethanol were measured across the entire range of mole fraction (chi(1) = 0.0000-1.0000) at T = (288.15-318.15) K. The average molar volumes of the binary mixtures were calculated from the experimental density, which increased with the increase of mole fraction and temperature. The excess molar volumes, V-m(E), were obtained and fitted by Redlich-Kister equation. The interaction between ionic liquid and alcohol is the strongest efficient packing and/or attractive interaction at the minimum point. The lower the temperature was, the smaller the absolute value of excess molar volume was. The new function - the molar surface quasi-Gibbs energy of mixtures was obtained by us in this work. On a basis of molar surface quasi-Gibbs energy of mixtures, a new Eotvos equation was obtained of mixtures and applied to binary mixtures of [MOEMIM][NTf2] with alcohols. The absolute value of the slope of the new Eotvos equation is the mole surface entropy, s, and the intercept is the molar surface enthalpy, h, which is temperature-independent. The deviation of molar surface quasi-Gibbs energy, Delta g(s), of mixtures for [MOEMIM][NTf2] with methanol and ethanol were calculated. Delta g(s) was well fitted by Redlich-Kister equation. In terms of Redlich-Kister's parameters, A(i), a new method for estimating the surface tension, gamma, with any component of the mixtures is proposed and the estimated values, gamma (est.), are in good agreement with the corresponding experimental ones, gamma(exp.). (C) 2019 Published by Elsevier Ltd.
Keywords:1-(2-methoxyethyl)-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide;Ionic liquid;Binary mixtures;Molar surface quasi-Gibbs energy of mixture