Solid-supercritical fluid phase equilibria

Abstract

Different types of phase behavior observed in binary mixtures containing a solid and a supercritical fluid (SCF) are discussed at the supercritical fluid extraction conditions. The pressure-temperature (P-T) projection of the solid-liquid-gas (S-L-G) three-phase coexistence curves together with the equilibrium liquid phase composition (x) values were determined by the first freezing point (FFP) method. The equilibrium cell was useful for the determination of liquid-gas critical loci for the binary system, leading to the location of the upper critical end point. The FFP technique was extended to ternary mixtures containing two solids. The PT projection of solid1-solid2-liquid-gas (S1-S2-L-G) four-phase coexistence curves together with the x values of the two solids were successfully determined. In addition, methods for calculation of solid solubilities in SCF by means of cubic equations of state are presented. © 1989, IEEE. All rights reserved.