Study About Interaction Between Bitumen SARA Fractions From Oil Sands In Toluene

Oil sands, a kind of unconventional energy source with huge reserves, haveattracted more and more attention with the increasing demand of energy consumption.Organic solvent extraction has been proposed as an alternative method. Usuallysolvent extraction process has two stages: bitumen phase dissolution and separation ofbitumen, solvent and sands. The diffusion of bitumen fractions (saturate, aromatic,resin and asphaltene) and the reactions between SARA fractions are significant factorsin the solvent extraction process. In this study, pure solvent (toluene, acetone andethyl acetate) and composite solvent (toluene/heptane, acetone/heptane and ethylacetate/heptane) systems were used to investigate the total recovery of bitumen andthe relative recovery of SARA fractions. Results showed that the relative recovery ofSARA was more than85%,75%,75%and50%, respectively. Molecular dynamicsimulation was used to evaluate the diffusion of SARA molecular in toluene, When insingle-fraction system, the mean square displacement value of SARA molecular wasranked in the order of saturate> asphaltene>resin≈aromatic, when in themixed-system, the value was in the order of saturate> resin> aromatics> asphaltene,the change indicated that the diffusion behavior of SARA molecular was affected withthe addition of other fractions. The interactions between SARA fractions of oil sandsbitumen have been characterized by isothermal titration calorimetry (ITC). Thethermodynamic parameters, such as enthalpy change (ΔH) and Gibbs free energychange (ΔG) were obtained. Results of ITC showed that the value of ΔG was in rangeof-10~-40KJ/mol, in the order of Ar-Re>Re-As>S-Re>Ar-As>S-As>S-Ar, whichindicated that binding process happened when two of SARA fractions were mixedtogether, and the force of each reaction was in the limit of van der waals energy.