Predicting phase behavior of nonpolar mixtures from refractive index at ambient conditions

Abstract

In a recent work, Evangelista and Vargas proposed correlations relating critical properties for nonpolar hydrocarbons to simple measurements of refractive index or density performed at ambient conditions (Evangelista and Vargas, Fluid Phase Equilibria, 2018). These correlations are used in this work to develop two approaches for improving phase behavior predictions with cubic equations of state. First, the correlations are applied to mixed solvents, treated as pseudo-pure fractions, whose refractive index and molecular weight were measured experimentally. Phase behavior predictions are performed on these systems to test the utility of a lumped solvent approach to be used when compositional information on a solvent is unavailable. Second, the correlations are applied within the default mixing rules of the cubic equation of state framework to calculate binary interaction parameters algebraically. This approach requires only simple laboratory measurements performed at ambient conditions instead of the more customary saturation pressure data that is more laborious to obtain and that might not be readily determined for certain substances.