SIMULTANEOUS REPRESENTATION OF VAPOR-LIQUID-EQUILIBRIA AND EXCESS-ENTHALPIES OF METHANOL - HYDROCARBONS SYSTEMS USING AN EQUATION OF STATE

We use the excess functions - equations of state model to represent thermodynamic properties (VLE and H(E)) of methanol - hydrocarbon binary systems. It is characterized by two conditions: the pure component Helmholtz energies are calculated by equations of state, the exces functions are defined at constant packing fraction. We have chosen a Peng-Robinson-type equation of state and for the excess function the UNIQUAC model in which parameters tau12 and tau21 are temperature-dependent. This method has been applied to twelve binary VLE in a wide range of temperatures and pressures. The average relative deviation with experiment in bubble-point pressure is about 1.5 % over 950 data points. We have treated the excess enthalpies of eight binary systems, the average deviation is about 6.4 % over 400 data points.