| Abstract
| - The aggregation behavior of asphaltenes in apolar solvents is studied using a molecular thermodynamicapproach. The theory is based on a molecular model for asphaltene aggregates that describes them asaromatic cores, composed of stacked aromatic sheets, surrounded by aliphatic chains. Using this simplemolecular model, an analytical expression is developed for the free energy of aggregation that incorporatesfive contributions due to (1) transfer of the polyaromatic rings from the solvent into the aromatic core, (2)mixing of the aliphatic chains with the solvent, (3) deformation of the aliphatic chains, (4) steric repulsionamong the aliphatic chains, and (5) aggregate core−solvent interactions. The proposed approach providesa qualitative description of the main experimental trends observed for asphaltene aggregation. Specifically,the experimentally observed variation of cmc values and aggregate size with (1) asphaltene molecularcharacteristics, (2) asphaltene concentration, (3) solvent composition, and (4) temperature has beenqualitatively reproduced by the theory. In addition, the thermodynamic molecular model developed doesnot utilize any information derived from experiments on asphaltene solutions, and therefore, it is strictlypredictive.
|
