Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

The Hildebrand's solubility parameter, d, gives a quantitative representation of the well-known "like dissolves like" aphorism for non-polar hydrocarbon liquids. This is of great commercial importance for certain polymers and hydrocarbon mixtures. However, the solubility parameters are usually available only at ambient conditions for a limited number of substances. Extrapolation of these parameters to high pressure and high temperature conditions is not attained by common empirical correlations or cubic equations of state. In this work a set of equations are derived from fundamental thermodynamic property relations to account for the pressure and temperature dependence of this cohesive energy parameter. The equations, which require a reference value for the solubility parameter eusually at ambient conditionse and volumetric data, are then applied to calculate the solubility parameters of four pure nonpolar hydrocarbons, namely n-heptane, n-dodecane, benzene and toluene, at temperatures from (298 e433) K and pressures up to 137 MPa. A comparison against literature data and predictions from the Perturbed Chain version of the Statistical Association Fluid Theory (PC-SAFT) and Peng-Robinson equations of state is also provided. The proposed method provides a novel approach for a quick, simple and accurate determination of the solubility parameters at elevated temperatures and pressures for non-polar hydrocarbons using density measurements.