Phase Equilibria Near Critical Co2 + Propane Mixtures With Fixed Oils In The LV, LL And LLV Region

PABLO E. HEGEL; GUILLERMO D. B. MABE; MARCELO S. ZABALOY; ESTEBAN A. BRIGNOLE

Orlando, USA

Simposio; International Symposium on Supercritical Fluids; 2005

Solvents like propane and carbon dioxide had been studied in previous works at supercritical and near-critical conditions and also as high-pressure liquid solvents for the extraction of vegetable oils. The variation of solvent power with pressure and temperature makes possible to apply these solvents to very different separation problems. Propane is completely miscible with fixed oils at room temperature but has liquid-liquid phase equilibrium with vegetable oils (sunflower oil, tripalmitin, etc.) at temperatures between the lower critical end point (LCEP) and the upper critical end point (UCEP) The liquid-liquid region is observed in a temperature range around 340 to 370 K - for typical vegetable fixed oils. At these temperatures the propane solvent power for triglycerides is drastically reduced and much higher pressures are required to recover the single phase region. The application of propane in the extraction of grounded seeds also has been questioned due to safety reasons. The solubility of fixed oils in near critical or supercritical CO2 is very low unless very high pressures of extraction are applied. The use of Propane + Carbon Dioxide mixture s as near critical solvents, can offer special properties regarding solvent power, selectivity and safety. The CO2 concentration effect on the emergence of the liquid-liquid equilibrium phenomena in ternary mixtures with propane and oil has been determined in the present work. Experimental phase equilibrium  data are obtained for binary and ternary mixtures of Propane + Carbon Dioxide and sunflower oil.with the purpose of obtaining the region of complete miscibility in the near critical (liquid) state of these ternary systems. The measurements were carried out from room temperatures at to the LCEP of the Propane Sunflower oil binary. This region has been studied in a variable volume, high pressure, view cell. In this way, experimental data were obtained for liquid-vapor, liquid-liquid-vapor and liquid-liquid phase behaviour. The compositions of the phases in equilibrium were obtained by sampling each phase at constant temperature and pressure. The oil concentration was determined gravimetrically and the concentration of Propane + Carbon Dioxide by Gas Chromatography. The experimental data are modelled with the group contribution equation of state.The experimental information will be valuable to obtain higher extraction efficiencies and safer operating conditions in the recovery of oils from grounded seeds (sunflower oil, tripalmitin, etc.) at temperatures between the lower critical end point (LCEP) and the upper critical end point (UCEP) The liquid-liquid region is observed in a temperature range around 340 to 370 K - for typical vegetable fixed oils. At these temperatures the propane solvent power for triglycerides is drastically reduced and much higher pressures are required to recover the single phase region. The application of propane in the extraction of grounded seeds also has been questioned due to safety reasons. The solubility of fixed oils in near critical or supercritical CO2 is very low unless very high pressures of extraction are applied. The use of Propane + Carbon Dioxide mixture s as near critical solvents, can offer special properties regarding solvent power, selectivity and safety. The CO2 concentration effect on the emergence of the liquid-liquid equilibrium phenomena in ternary mixtures with propane and oil has been determined in the present work. Experimental phase equilibrium  data are obtained for binary and ternary mixtures of Propane + Carbon Dioxide and sunflower oil.with the purpose of obtaining the region of complete miscibility in the near critical (liquid) state of these ternary systems. The measurements were carried out from room temperatures at to the LCEP of the Propane Sunflower oil binary. This region has been studied in a variable volume, high pressure, view cell. In this way, experimental data were obtained for liquid-vapor, liquid-liquid-vapor and liquid-liquid phase behaviour. The compositions of the phases in equilibrium were obtained by sampling each phase at constant temperature and pressure. The oil concentration was determined gravimetrically and the concentration of Propane + Carbon Dioxide by Gas Chromatography. The experimental data are modeled with the group contribution equation of state.The experimental information will be valuable to obtain higher extraction efficiencies and safer operating conditions in the recovery of oils from grounded seeds.