DISQUAC predictions of phase equilibria, molar and standard partial molar excess quantities for 1-alkanol+cyclohexane mixtures

Abstract

Literature data for phase equilibria: vapor-liquid VLE, liquid-liquid LLE, and solid-liquid SLE; molar excess Gibbs energies GE, molar excess enthalpies HE; activity coefficients γi∞ and partial molar excess enthalpies HiE,o at infinite dilution for 1-alkanol (1)+cyclohexane (2) mixtures are examined by the DISQUAC group contribution model. For a more sensitive test of DISQUAC, the azeotropes, obtained from the reduction of the original isothermal VLE data, are also examined for systems characterized by hydroxyl, alkane and cyclohexane groups. The alkane/cyclohexane and alkane/hydroxyl interaction parameters have been estimated previously. The cyclohexane/hydroxyl interaction parameters are reported in this work. The first dispersive parameters increase regularly with the size of the alkanol; from 1-octadecanol they are constant; an opposite behavior is encountered for the third dispersive parameters, which are constant from 1-dodecanol. The second dispersive parameters decrease as far as 1-propanol and then increase regularly; from 1-octadecanol they are constant. The quasichemical parameters are equal to those for the alkane/hydroxyl interactions. Phase equilibria, the molar excess functions, and activity coefficients at infinite dilution are reasonably well reproduced. Poor results are found for HiE,o and DISQUAC predictions for HiE,o are strongly dependent on temperature.