Effect of co-solvents on SC-CO₂ extraction of crude oil by consistency test

The capability of ethanol, methanol, propanol, acetone, and kirasol to improve the extraction of crude oil by supercritical carbon dioxide was investigated at 30-60 MPa and 60 °C. The co-solvent in an amount of 3 g was added in 100 mL extraction cell to modify the extraction of 40 g of oil. The applied consistency test showed that the co-solvent addition facilitated the decrease of both saturation pressures. The P1sat decreased as the average total oil recovery improved due to the effect of co-solvent in the following order: acetone, propanol, methanol, ethanol. The presence of kirasol had a substantial detrimental effect on total oil recovery. In order to determine the co-solvent effect on vapor recovery, a modified version of the consistency test, which included two types of plots, was introduced. The effect of the co-solvent on oil vapor recovery was evaluated based on the departure of the line or point corresponding to the modified extraction with the addition of specific co-solvent from the line or point corresponding to the extraction using pure supercritical carbon dioxide. The extracted oil samples were analyzed by GC-MS chromatography.