Effect of modifiers in n-pentane on the supercritical extraction of Athabasca bitumen

Experiments involving the supercritical extraction of bitumen using various solvent mixtures were carried out in a 2-l batch autoclave to determine the effect of modifier type and concentration on deasphalted oil (DAO) yield and quality. Athabasca bitumen was used as the feedstock and n-pentane was used as the primary solvent for extraction. Acetone, toluene, methanol and ethyl acetate were each added to n-pentane as modifiers in different concentrations to form the solvent mixtures. Extraction temperatures and pressures were maintained at around 200 °C and 1100 psi to achieve supercritical conditions for solvents, and the solvent-to-feed volume ratio was kept around 6.5. Higher DAO yields were obtained with increasing modifier concentrations in n-pentane. DAO yields ranged from 79 to 92 wt.% of the bitumen, with n-pentane/toluene mixtures providing the highest yields and n-pentane/methanol mixtures producing the lowest. Increases in DAO yield were accompanied by higher nickel, vanadium, nitrogen, sulfur and microcarbon residue content in DAO. Moreover, it was found that n-pentane/methanol and n-pentane/acetone solvent mixtures had lower selectivities for metals impurities than the other modifiers, while n-pentane/toluene had the highest selectivities.