(84e) Deasphalting of Oil Sands Bitumen Using Supercritical Solvent Mixtures

The processing of heavy oil and bitumen is becoming increasingly important due to the decreasing supply of light crude. Conventional bitumen upgrading processes, such as vacuum distillation and coking, are energy-intensive and the liquid products are accompanied by significant amounts of coke and gases. In addition, the liquid products obtained are of poor quality and have high aromatic content. Using solvent deasphalting (SDA) can reduce energy consumption by as much as 30% compared to conventional upgrading processes.

Experiments involving the solvent deasphalting of bitumen using various solvent mixtures at supercritical conditions were carried out in a two-liter 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^oC 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 micro carbon 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.