Asphaltene Self‐Association

Recent characterizations of asphaltene structures suggest that asphaltene monomers may consist of several small polynuclear aromatic clusters linked by alkyl chains and containing a variety of heteroatoms. This structure lends itself to the view that asphaltenes self‐associate in a manner analogous to oligimerization rather than simple stacking. If asphaltenes are assumed to be oligimers, some of the interesting features of asphaltene behavior can be explained in a self‐consistent approach, including: measured changes of asphaltene molar mass in different solvents and at different temperatures; the precipitation of asphaltenes from alkane‐diluted heavy oils; and the interfacial behavior of asphaltenes. Recent work in these areas indicates that asphaltene monomers are in the order of 1000 to 2000 g/mol and that self‐associated asphaltenes consist of two to six monomers per aggregate on average.