INSIGHTS OF ASPHALTENE AGGREGATION MECHANISM FROM MOLECULARDYNAMICS SIMULATION

摘要

Asphaltene aggregation process was studied using molecular dynamics techniques. Four different structures were used. The first threemolecules have a continental structure, with condensed aromatic cores, while the forth has an archipelago structure, with small groups ofaromatic rings connected with saturated chains. The molecules were constructed in an atomistic framework, in which atoms are describedindividually. Interaction forces were calculated at 300 K and 200 atm; Van der Waals and electrostatic interactions were evaluatedseparately. For all four molecules the solubility parameter was calculated. It was found that Van der Waals interactions due to thepresence of aromatic rings and electrostatic forces caused by the presence of heteroatoms such as oxygen, nitrogen and sulfur, are equallyrelevant in the aggregation of asphaltene molecules. For all molecules it was found asphaltene systems are more stable in aggregationstate than in monomeric state. For continental structures, the presence of long ramifications obstructs the formation of asphalteneaggregates. For archipelago structures, the flexibility of the molecules enables the aggregation with other structures. The presence ofheteroatoms creates a repulsive force that hinders the aggregation process. The molecular volume and the cohesive energy are alsosensitive to the geometric configuration and the composition of the species, which affects the solubility parameter.