EXPERIMENTAL MEASUREMENTS OF PHASE-EQUILIBRIA FOR TERNARY AND QUATERNARY SYSTEMS OF GLUCOSE, WATER, CO2 AND ETHANOL WITH A NOVEL APPARATUS

Vapor-liquid equilibrium data have been measured for the ternary glucose-water-CO2 system and for the quaternary glucose-water-ethanol-CO2 system at temperatures from 323 to 343 K and pressures up to 30 MPa. Since the solubility of glucose in the vapor phase is small, a special high pressure apparatus has been designed and developed to ensure reliable sampling and analysis. The heart of the apparatus is a autoclave with a volume of 500 cm3 equipped with capillary tubes for liquid samples. The vapor phase is recirculated by an air-driven piston pump. The novel feature of our design is a sample bomb of 300 cm3 capacity placed in the vapor phase loop which can be blocked off and the content of which can be analyzed without disturbing equilibrium. Results indicate that while the solubility of glucose in pure supercritical CO2 is very small (10(-5)-10(-4) mol%), it shows a remarkable increase (2*10(-4)-5*10(-2) mol%) with increasing pressure when ethanol is added as a polar co-solvent.