Analysis of thermodynamic models representing mixtures with hydrocarbons, water and alcohol - I. General treatment and representation of vapor-liquidequilibria and enthalpies of mixign of low-pressure binary systems

The aim of this work was to indicate some thermodynamic models based on the formalism 'Equation of state-Excess function' able to represent thermodyna mic properties of complex systems. First, we have developed the characteris tics of the corrected Peng-Robinson equation of state for pure components a s well as the conditions of its extension to mixtures by using excess funct ion models such as those of van Laar, NRTL, Adachi-Sugie, Schwartzentruber- Renon and that of the 'Surrounded Molecule'. Afterwards, we have studied the simultaneous representation of vapor-liquid equilibria and mixing enthalpies of binary systems containing non-polar, p olar or associated compounds by using a temperature-dependence of the param eters for all models considered. The obtained results allow thus to establi sh what classes of compounds need the use of excess functions depending of one, two or three binary interaction parameters.