THERMODYNAMIC PROPERTIES OF N-ALKYLBENZENE-ALKANE OR CYCLOHEXANE MIXTURES - COMPARISON WITH DISQUAC PREDICTIONS(N)

The molar excess enthalpies (H-E), at 298.15 K, of some mixtures of al kylbenzenes with n-heptane or cyclohexane were measured using a flow c alorimeter. These data, along with the literature data on molar excess enthalpies (H-E), molar excess Gibbs energies (G(E)), molar excess he at capacity (C-p(E)) and activity coefficients at infinite dilution (g amma(i)(infinity)) of mixtures in n-alkanes or cyclohexane of mono-alk ylbenzenes of general formula, C6H5-(CH2)(n-1)CH3, isomeric dimethylbe nzenes (xylenes) and isomeric trimethylbenzenes were treated within th e framework of DISQUAC, an extended group contribution model, in the s implified 'dispersive' version. The systems were characterized by thre e types of contact surfaces: phenyl (C6H5 group), alkane (CH3 or CH2 g roups) and cyclohexane (c-CH2 group). The interchange energy parameter s of the alkane/cyclohexane contacts were determined previously, the i nteraction parameters of the alkane/phenyl and cyclohexane/phenyl cont acts are reported in this study. The dispersive parameters depend on t he environment of the phenyl group and the number of alkyl groups adja cent to the phenyl group. The model provides a fairly consistent descr iption of the experimental data as a function of concentration. (C) 19 98 Elsevier Science B.V.