Petroleum asphaltenes form complex heterogeneous supramolecular aggregates stabilized by multiple and rather weak interactions, such as hydrogen bonding, dispersion, metal coordination and occlusion. We employ multiscale modeling methods developed at NINT to predict the supramolecular interactions of model archipelago asphaltene compounds containing heterocyclic polyaromatic moieties in solution and study the resultant UV-Vis and 1H NMR spectroscopic changes. In non-interacting organic solvents, asphaltene aggregation is driven by dispersion interactions that are identified using 1H NMR chemical shifts. The addition of trace amounts of water dramatically enhances aggregation due to the formation of water bridges hydrogen bonded to the lone pairs of pyridyl N atoms, as evidenced by 1H NMR chemical shift changes. The interaction of Ni and vanadyl porphyrins with pyridine and quinolines is more complex as it yields either hydrogen-bonded or axially-coordinated aggregates, depending on the steric accessibility of the metal and N atoms. The calculated spectral changes associated with all these interactions in solution are validated with respect to experimental spectra.

Spectroscopic characterization of the supramolecular aggregation interactions of petroleum asphaltenes in solution: A multiscale modeling investigation

245th National Meeting (2013)

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