High-pressure phase equilibria in binary and ternary mixtures with one near- or supercritical and one high-molecular component. New insights for application and theory

In this work we report on two different high-pressure phase equilibria. The first is the solubility of a low-volatile solid in a supercritical phase. These are two anthraquinone dyes 1,4-bis-(hexadecylamino)-9,10-anthraquinone and 1,4-bis-(dodecylamino)-9, 10-anthraquinone dissolved in CO2 and N2O. Secondly, the partition of an infinitely diluted high-molecular biocompound between coexisting high-pressure liquid phases in a ternary system consisting of a nearcritical gas, water, and an organic solvent, that is a fully miscible with water at standard conditions, is investigated. The high-molecular compounds are two cardiac glycosides digoxin and digitoxin, which occur in the foxglove plant. The corresponding ternary phase-forming system consists of CO2, water, and 1-propanol. The binary solubilities are determined within 310 and 340 K and up to 180 MPa where retrograde solubility is observed. The partitioning experiments are done at 313 and 333 K and at pressures, where a three-phase liquid-liquid-gas equilibrium with one water-like and one propanol-like phase exists. Experimental data are listed and discussed. Additionally, the correlation of the solubility data with a recently developed Carnahan-Starling-van der Waals type equation of state extended for the nearcritical region are discussed. The partitioning data with a hybrid model that combines the Peng-Robinson equation of state with an excess Gibbs energy approach based on UNIQUAC are outlined briefly and the results interpreted. C 2006 Springer Science + Business Media, Inc.