The Asphaltene Fraction – Demystified

The asphaltene constituents of crude oil are the highest molecular weight heaviest and most polar constituents in the oil and the fraction is isolated a dark brown to black friable solids that have no definite melting point and usually foam and swell on heating to leave a carbonaceous residue. The fraction is obtained from crude oil by the addition of a hydrocarbon liquid (such as n-pentane or n-heptane). Any molecular models derived for asphaltene constituents must be in keeping with behavioral characteristics. Efforts have been (and continue to be) made without justification to describe the asphaltene fraction in terms of a single, representative asphaltene molecule or molecules incorporating, in the correct proportions, all of the chemical constituents known to be present in a given asphaltenic matrix. Obviously, the chemistry and structural features of the constituents of crude oil asphaltene fractions will be dictated by the distribution of functional and structural type that occur in the fraction. This makes the representation of the structure and functionality of the constituents by so-called average structures very difficult (if not, impossible) to conceive.