ESTIMATION OF DISQUAC INTERCHANGE ENERGY PARAMETERS FOR 1-ALKANOLS PLUS BENZENE, OR PLUS TOLUENE MIXTURES

The data available in the literature on vapour-liquid equilibria (VLE), molar excess Gibbs energies (G(E)), molar excess enthalpies (H-E), molar excess heat capacities (C-p(E)), activity coefficients (gamma(i)(infinity)) and partial molar excess enthalpies (H-i(E,infinity)) at infinite dilution of 1-alkanol(1) + benzene(2), or + toluene(2) mixtures are examined on the basis of 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 a number of systems. The components in the mixtures are characterized by three types of groups of surfaces: hydroxyl (OH group), alkane (CH3 or CH2 groups), and aromatic (C6H6 or C6H5 groups in benzene or in toluene, respectively; both groups considered as different). The alkane/aromatic and alkane/hydroxyl contact parameters are available in the literature. The parameters for the hydroxyl/benzene and hydroxyl/toluene interactions are reported in this work. The quasichemical parameters are common for the whole set of alcohols (except the first interchange coefficient of methanol, which is different from that for the remaining alcohols), and do not depend on the aromatic molecule considered. Such dependence is encountered only for the second dispersive parameters. These interchange coefficients together with the first ones increase regularly with the size of the alcohol, although, from ethanol, the former are kept the same for each pair of alcohols. The third dispersive parameters behave in an opposite way to the second ones, and are constant from 1-dodecanol. The model consistently describes phase equilibria and the molar excess functions. Dependence on temperature of C-p(E) is well represented, even the S-shape of this quantity for the 1-butanol + toluene system at high temperatures. Natural logarithms of activity coefficients at infinite dilution are reasonably well reproduced. Predictions on H-i(E,infinity) are opposite to those for mixtures of 1-alkanols with n-alkanes or cyclohexane. They are surprisingly good in the case of H-1(E,infinity) and somewhat poorer for H-2(E,infinity).