DISQUAC PREDICTIONS OF PHASE-EQUILIBRIA, MOLAR AND STANDARD PARTIAL MOLAR EXCESS QUANTITIES FOR 1-ALKANOL PLUS CYCLOHEXANE MIXTURES

Literature data for phase equilibria: vapor-liquid VLE, liquid-liquid LLE, and solid-liquid SLE; molar excess Gibbs energies G(E), molar excess enthalpies H(E); activity coefficients gamma(i)infinity and partial molar excess enthalpies H(i)E,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 H(i)E,O and DISQUAC predictions for H(i)E,O are strongly dependent on temperature.