An experimental study of three- and four-phase equilibria for isopropanol—water—carbon dioxide mixtures at elevated pressures

Abstract

Compositions and molar volumes of the three phases in liquid—liquid—gas equilibrium are reported for ternary mixtures of isopropanol, water and CO 2 at elevated pressures and at temperatures of 50 and 60°C. Phase compositions and molar volumes were also obtained for three-phase, liquid—liquid—liquid equilibrium and four-phase, liquid—liquid—liquid—gas equilibrium at 40°C. Gas—liquid and liquid—liquid critical endpoints, which represent pressure bounds on the liquid—liquid—gas region at 60°C, were determined from observations of critical opalescence. The phase behavior exhibited by the isopropanol—water—CO 2 system is quite complex, particularly at conditions near the critical point of CO 2. These conditions are well within the range of operating conditions proposed for supercritical-fluid extraction of organic compounds from water using CO 2. Therefore, the existence of multiple coexisting phases can be an important factor in designing and operating such extraction processes.