Studies on large crude oil alkanes. II. Isolation and characterization of aromatic waxes and waxy asphaltenes.

Isolation of very large alkane components as described in the first paper within this series, fail in some cases. This work describes two non-routine isolation procedures applied to two different non-typical petroleum fractions. The first one comprises a chromatographic approach applied for the separation of alkanes from alkylaromatic compounds derived from paving asphalt waxes. The second separation procedure was developed for the isolation of alkane fractions associated with asphaltenes that precipitated during long crude oil storage periods, resulting in highly insoluble organic composites. In the first case, the isolated fractions were characterized by spectroscopic and chromatographic methods. The evidence showed that long chain naphtheno-aromatic molecules behave like waxy asphalt components, which interact by unusual mechanisms with solid sorbents. Their chromatographic behavior was found to be between typical alkanes and typical aromatics. This behavior is caused by the simultaneous presence of three functionalities. The second sample type was characterized by spectroscopic methods only. The results permitted to assess that the waxy composite from crude oil tank sediments precipitated selectively, including highly aromatic and long alkyl chain asphaltenes as well as very large n-alkanes.