QUANTITATIVE STRUCTURAL INFORMATION OF RESIDUE FRACTIONS FROM MOLECULAR REPRESENTATIONS

William C. McCaffrey, Murray R. Gray, Heather D. Dettman, Jeffrey M. Sheremata

Chemical and Materials Engineering, University of Alberta, Canada

A complete description of heavy oil is elusive despite the wide variety of analytical methods that are available to asphaltene scientist and engineers.  Quantitative molecular representations are a powerful tool to reconcile this data and produce manageable sets of molecules. In this study, quantitative molecular representations were constructed for ten fractions of Athabasca vacuum residue that were prepared by supercritical fluid extraction.  Construction of the molecules followed the general archipelago framework of asphaltene structure with alkyl and sulfur bridges linking aromatic groups.  The primary structural data that was used for construction included molecular weight, elemental analysis and proton and ¹³C-NMR. The algorithm was also expanded to incorporate the aromatic-aliphatic sulphur distribution for each fraction.  Six molecules were needed to adequately represent the primary structural data for each fraction.  An important benefit of the quantitative molecular representations is that secondary structural information can be determined from the representations.  Analysis of the molecular representations yielded secondary structural information that could not be determined solely from the NMR analysis. This work also provides a basis for kinetic and thermodynamic models for bitumen based on realistic molecular components.