The components of petroleum asphaltenes exhibit complex bridged structures comprising sulfur, nitrogen, aromatic, and naphthenic groups linked by alkyl chains. These components aggregate in crude oil and toluene over a wide range of concentrations and temperatures, exhibit strong adhesion to a wide range of surfaces, occlude components that are otherwise soluble, are porous to solvents, and are elastic under tension. None of these properties is consistent with an architecture dominated only by aromatic stacking by electrostatic and/or van der Waals forces, often called π–π stacking. We propose an alternate paradigm based on supramolecular assembly of molecules, combining cooperative binding by Brønsted acid–base interactions, hydrogen bonding, metal coordination complexes, and interactions between cylcoalkyl and alkyl groups to form hydrophobic pockets, in addition to aromatic π–π stacking. A range of architectures are suggested, which almost certainly occur simultaneously, including porous networks and host–guest complexes. The latter may include organic clathrates, in which occluded guest molecules stabilize the assembly of a cage, as methane does in gas hydrates. This model has a number of implications for analysis of asphaltene mixtures and predicting asphaltene phase behavior and transport properties.

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A series of model compounds for the large components in petroleum, with molecular weights from 534 to 763 g/mol, was thermally cracked in the liquid phase at 365À420 °C to simulate catagenesis over a very short time scale and reveals the selectivity and nature of the addition products. The pyrolysis of three types of compounds was investigated: alkyl pyrene, alkylbridged pyrene with phenyl or pyridine as a central ring group, and a substituted cholestaneÀbenzoquinoline compound. Analysis of the products of reaction of each compound by mass spectrometry, high-pressure liquid chromatography, and gas chromatography demonstrated that a significant fraction of the products, ranging from 26 to 62 wt %, was addition products with molecular weights higher than that of the starting compounds. Nuclear magnetic resonance (NMR) spectroscopic analysis showed that the pyrene compounds undergo addition through the attached alkyl groups, giving rise to bridged archipelago products. These results imply that the same geochemical processes that generate the light components of petroleum, such as n-alkanes, simultaneously produce some of the most complex heavy components in the asphaltenes. Similarly, thermal cracking reactions during refinery processes, such as visbreaking and coking, will drive addition reactions involving the alkyl groups on large aromatic compounds.