Separation of Heavy Oil into Narrow Fractions by Supercritical Fluid Extraction Using a CO2–Toluene Mixture

We demonstrate that the method based on supercritical fluid extraction (SFE) using supercritical carbon dioxide (SC-CO2) as a basis of a solvent can be used, in principle, to fractionate a sample of heavy oil into narrow fractions. Studies are conducted using heavy oil of the Ashalchinskoye field as an example. The composition and yield of the fractions extracted from heavy oil depend on the concentration of the organic modifier (toluene) added to SC-CO2. Supercritical fluid extraction was carried out in a semiperiodic mode at 50°C and a pressure of 100 bar with a gradual increase in the concentration of toluene from 0 to 40 wt %. This resulted in nine fractions extracted with a total extract yield of 83.4 wt %. The use of SFE can significantly decrease the amount of the residue after the fractionation of heavy oil. The composition and properties of narrow fractions extracted from heavy oil are determined. The distribution of group hydrocarbon components, metals, sulfur, and Conradson carbon residue (CCR) between the extract fractions and the residue is found.