WILSON AND NRTL CORRELATIONS OF THE VAPOR-LIQUID-EQUILIBRIA OF BINARYSOLVENT MIXTURE FOR ALL PRESSURE AND TEMPERATURE CONDITIONS

A single set of Wilson or NRTL parameters to describe the vapour liqui d equilibria of a solvent mixture at all pressure and temperature cond itions is best derived by nonlinear regression of combined experimenta l isobaric and isothermal data using a linear temperature function for the interaction energy parameters. Correction for the temperature eff ect on the molar volume of the solvents in the Wilson model or on the nonrandomness factor in the NRTL model has negligible effect on the co rrelation. For the 16 binary systems of both polar and nonpolar solven ts involving 224 isothermal and isobaric data sets with a combined tot al of 3161 data points over a considerable range of temperatures and p ressures, both the correlations by the Wilson and NRTL models show an overall mean absolute error of 0.011 (3%) for the vapour composition, 0.8-degrees-C (1%) for the bubble point and 60 mm Hg (3%) for the pres sure. These errors are comparable and in many cases better than those reported for the individual correlation of each of the data sets.