Detection of alkylated fluorenes in Athabasca oil sand bitumens

Abstract

Athabasca oil sand aromatic fractions were subjected to base-catalyzed autoxidation to selectively oxidize fluorenes to fluoren-9-ones and to 9-alkylfluoren-9-ols. Owing to differing polarities, the oxidation products could be separated conveniently by column chromatography to yield a series of mono- to tetramethylfluoren-9-ones, 9- n-alkylfluoren-9-ols and their nuclear methylated derivatives which were previously detected in Alberta bitumen resins. In the samples analyzed, 1,4-dimethylfluorene was present as the major nuclear dimethylated fluorene along with minor amounts of the 2,4- and 3,4-dimethyl isomers. 2,4-Dimethylfluorene was found in one sample but was absent in the other. 9-Methylfluorene was the major 9-alkyl compound present. Individual members of these series were identified by comparison of capillary gas chromatographic retention times and mass spectra with those of synthetic standards. It is suggested that the fluorenes are the source of fluorenones and fluorenols in Athabasca oil sand. The reservoir may have experienced mildly oxidative conditions at some time.