Asphaltenes are large, high density molecules 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 is soluble in toluene.