Chemical Composition of Athabasca Bitumen: The Distillable Aromatic Fraction

摘要

The volatile aromatic fraction (240 °C and 10 3 Torr pressure) of Athabasca bitumen was separated via thin-layer chromatography (TLC) (Ag+/SiO_2), followed by alumina column chromatography, into 13 mono-, di-, and triaromatic subfractions, each of which was subjected to field ionization mass spectrometry (FIMS) analyses. Altogether, close to 6000 constituent molecules, ranging in molecular weight from 200 to ~800 Da, have been observed, including the partially and fully aromatized, ring-opened, and truncated derivatives of essentially all of the saturated biomarkers detected here or earlier in the saturated fraction of this bitumen. AU molecules detected were of aromatic character, with the exception of a complex suite of cyclic terpenoid (and steroid) sulndes, having adsorptive properties similar to those of the triaromatic hydrocarbons. In several cases, the FIMS analyses were supplemented by conventional biomarker analyses and a novel biomarker analysis, employing basic aqueous extraction of the whole oil sands. The high-molecular-weight portion (MW > 482 Da) of each subfraction isolated (which usually does not show up in conventional biomarker analyses) varies in concentration from a few to about 10 wt 96. This fraction may arise from processes analogous to the combination reactions occurring in the addition of biomarker molecules to asphaltene by C-C, C-S-C, and C-O-C covalent bond formation. In the present system (with the exception of the cyclic suliides), only C-C bond additions can be operative.