Recovery of asphaltenes from tar sand by supercritical fluid extraction

Many non-oil producing countries are enriched with other sources of energy, for example tar sand, oil shale, coal, biomass, and uranium, that are not fully utilized. Supercritical fluid extraction (SFE) of tar sand was carried out in a batch autoclave at different temperatures. Extracts recovered from SFE were fractionated into oils, asphaltenes, preasphaltenes and gases by solvent extraction. The highest yield) of SFE (24.3 wt% dry basis) from tar sand was obtained with n-pentane/benzene (1/1, v/v) mixture at 655 K. Comparison of the amount of n-alkanes (C-1-C-4) evolved at 585 K and 685 K shows that the amount of methane is significantly increased at 685 K whereas the amount of C-4 alkane is reduced. At 685 K, hydrogen and methane represent 45.1 vol % of the gases evolved from the SFE. The yields of C-1-C-3 alkane hydrocarbons were higher for supercritical fluid extracts at 685 K as compared to those obtained at 585 K. The quantity of olefines (C2H4 + C3H6) was found between 5.1 and 10.1 vol %.