Phase Equilibria in the Critical Region: Binary Systems with Chlorotrifluoromethane

Abstract

of phase equilibria is fundamental to the understanding of heterogeneous systems and to their use in separation processes and other chemical engineering operations. Phase equilibria in the critical region-the region a t elevated pressures above the critical temperature of one of the compounds-are characterized by large nonidealities in the gas phase as well as possible liquid phase nonidealities. These nonidealities are manifested in interesting but generally unpredictable phenomena such as the solution of relatively large amounts of nonvolatile liquids and solids in supercritical gases, the existence of liquid phases consisting almost entirely of a supercritical component, phase inversions, gas-gas immiscibilities, etc. Unique separation processes might utilize the large changes in solubilities that occur over small temperature and pressure ranges in the critical region.The present investigation is part of a continuing program a t Princeton aimed a t the understanding and generalization of phase equilibria just above the critical temperature of the gaseous component. Todd and Elgin (16) presented results of the original investigation of organic liquids with supercritical ethylene (T,9.5" C.) which established the three types of pressure-composition isotherms that have also been found in all subsequent binary systems. This work was extended by Gottschlich ( 7 ) , and ternary systems with ethylene were studied by Elgin and Weinstock ( 5 )

Reactions in supercritical fluids - a review

“…An example of very large negative partial molar volumes of a heavy solute in a supercritical fluid is shown in Figure 5 for the vinyl chloride-supercritical ethylene system (Ehrlich and Fariss, 1969). Other investigators have shown experimentally that the phenomenon of very large, negative partial-molar volumes exists for systems in which the solute is in dilute concentrations and the solvent is very close to its critical conditions (Eckert et al, 1983; Chappelear and Elgin, 1961;Ehrlich and Wu, 1973). Using a lattice-gas model, Wheeler (Wheeler, 1972) is able to theoretically explain this unusual partial molar volume behavior near the solvent critical point.…”

Thermodynamics of Ternary, Liquid-Supercritical Gas Systems with Applications for High Pressure Vapor Extraction

“…The parameter an is obtained from solubility data of the gas in pure solvent 1 such as that presented in Figure 6. Todd and Elgin (70) and Chappelear and Elgin (2) have reported such data for ethylene and chlorotrifluoromethane in organic liquids. For the 1-2 binary, *3 = 0 and Equation 21becomes…”

“…Effect of Margules Constants on Phase Behavior Since industrial separation processes operate in the Zi -Z2 region, it is important to determine how the Margules parameters affect the shape of the coexistence curve and the slope of the tie lines. In order for any liquid-liquid region to exist, at least one of the binary Margules constants must have a value greater than 2 (only positive values are being considered here); this is a consequence of the stability criteria given by Equation 5. Assume for illustrative purposes that the 2-3 binary satisfies this condition-that is,…”