STRUCTURAL UNITS OF ATHABASCA ASPHALTENE - THE AROMATICS WITH A LINEAR CARBON FRAMEWORK

A flash pyrolysis method has been employed, allowing the production of pyrolysis oil from Athabasca asphaltene on the multigram scale, for the identification of homologous series of n-alkylbenzenes, 9-n-alkylfluorenes, and 1-n-alkyldibenzothiophenes. These aromatic classes of compounds were concentrated from the pyrolysis oil by a sequence of selective oxidative and chromatographic steps. Identification was based on comparison of GC retention times and mass spectra with those of synthetic standards or with literature values. The 1-n-alkyldibenzothiophenes were also found in the maltene fractions of several heavy oils and bitumens of northern Alberta and the 9-n-alkylfluorenes were found before in the maltene fraction of Athabasca bitumen. These aromatic compounds all possess alkyl substitution patterns which suggest that they have been derived by the cyclization and aromatization of precursor substances which possessed a linear carbon framework. The linear carbon framework of these and other compounds previously identified in the pyrolysis oil of Athabasca asphaltene contrasts with the terpenoid carbon framework which characterizes the compounds identified in the distillable portion of the maltene of the same bitumen and points to an n-alkanoic origin of the asphaltene.