THE ROLE OF POLAR SPECIES IN THE AGGREGATION OF ASPHALTENES

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Abstract
Many properties of heavy oils are Influenced by the presence of asphaltenes. According to solubility studies, asphaltenes are the most polar fraction of heavy oils, but the magnitude of the dlpole moment is not known. We quantified this parameter by applying dielectric spectroscopy to several heavy oils with different asphaitene concentrations, and the response of the permanent dlpoles was measured as a function of concentration and temperature. The asphaltenes have dielectric constants ranging from 5 to 7. Calculations Indicate more than one dlpole per asphaitene molecule. The diameter of the dlpole center was assessed to be 3 to 6 A. The probe was extended to study the Involvement of dlpoles In asphaitene aggregation. As the concentration of asphaltenes exceeds 10%, the dielectric constant exhibits substantial negative deviation from linearity, signifying the onset of Intermolecular Interactions (the pairing of dipoles in head-to-ta1l configurations to form clusters). Raising the temperature Increases the dielectric constant. Indicating dissociation of the aggregates. Based on comparison of these results with the dielectric behavior of model compounds the role of dipoles in the process of asphaitene association has been demonstrated for the first time.

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