Structural Relaxation Behaviors of Three Different Asphaltenes Using MD Calculations

For asphaltene obtained from vacuum residues of three different kinds of crude oils (Khafji, Maya, and Iranian-Light), the energy-minimum conformation calculated by molecular mechanics-dynamics simulations showed that aggregated structures of asphaltene molecules through noncovalent interactions are the most stable conformation. Changes of aggregated structures by heating or solvent treatment were investigated by using the molecular dynamics calculation. For Khafji and Iranian-Light asphaltenes, the simulation showed that the aggregated structure was dissociated at 673K, while for Maya asphaltene the dissociation behavior was not observed, showing that Maya asphaltene seems difficult to be dissociated by heating, compared to other asphaltenes. In contrast, the simulation of relaxation of the Maya aggregates in quinoline showed that at 573K a part of aggregates was dissociated more easily than Khafji and Iranian-Light asphaltenes. These results above suggest that the effects of heating and solvent treatment on the structural relaxation of asphaltene aggregates can be different.