Development of techniques for the supercritical fluid extraction of oils

Experimental equipment, procedures and an analysis method have been developed to provide equilibrium data for supercritical fluid solvents CO₂, C₂H₄, C₂H₆, C₃H₆ and C₃H₈ in tne presence of a multicomponent separator oil. The equilibrium cell was developed around a 1 dm³ high pressure autoclave. The maximum pressure and temperature ratings of the developed cell were 34.5 MPa and 200°C respectively. A circulating system was used in the design of the cell to allow the sampling of two fluid phases at isobaric equilibrium conditions. The high pressure samples were expanded to ambient conditions forming a liquid and gas phase. The liquid phase represents the oil fraction and the gas phase the solvent fraction. The oil analysis was based on a gas chromatographic distillation. The chromatographic analyses provided a qualitative and quantitative description of compounds with molecular weights up to n-C₃₉H₈₀. No gas analysis was performed and therefore the procedures were unsuitable for hydrocarbons more volatile than decane (n-CO₁₀H₂₂). The reliability of the present equipment and procedures were checked by comparing equilibrium data for the CO₂/n-CO₁₀H₂₂ system, obtained at a pressure of 10.34 MPa and a temperature of 137.8°C, with previously published data. Repeatability tests were also performed using supercritical CO₂ and a multicomponent oil solute at pressures of 13.5 MPa and 20.2 MPa at a temperature of 65.5°C.