Characterization of the Nonstable Fraction of Hassi−Messaoud Asphaltenes

The objective of this work was to separate and study a least stable fraction of Hassi-Messaoud asphaltenes that flocculate during oil transport and storage. The unstable fraction was studied by consecutive fractioning with solvents differing in polarity. A correlation between structural parameters of asphaltenes and the flocculation onset was established. It was demonstrated that the spontaneously flocculating part of asphaltenes is composed of relatively small molecules that are less aromatic and contain more heteroatoms than more stable asphaltenes. The length of the side aliphatic chain was shown to be an important parameter influencing the flocculation onset.