Asphaltenes are large, high-density hydrocarbons found in the heaviest distillation fractions of crude oil.
Asphaltenes are the primary components of the product asphalt.
High asphaltene content is desirable for a refiner producing asphalt, but undesirable if the asphaltene-containing resid is intended for fuel oil blending or feed to conversion units.
Asphaltenes include a large number of different hydrocarbon molecules. The primary definition of an asphaltene is that it is insoluble in n-heptane but soluble in toluene.