Micromechanism of petroleum asphaltene aggregation

Abstract

The periodic molecular structure model of solvent-asphaltene system is constructed using molecular mechanical and molecular dynamical methods. The influences of six kinds of different solvents (Nitrobenzene, Quinoline, Pyridine, 1-methylnaphthalene, Dibromomethane, Benzene) on the aggregate process of asphaltene molecules are investigated at normal temperature and higher temperatures. According to the analyses of structure and energy, the main interaction for the asphaltene aggregate is determined, and the influencing mechanism for the asphaltene stability in different solvent is discussed at 300 K and 573 K temperatures. It is found that van-der-Waals (VDW) interaction plays an important role in the stability of the asphaltene aggregate. The electrostatic interaction is small compared to the VDW interaction, and the π-π interaction is the leading force for the aggregation of asphaltene molecules. The presence of heteroatom might be the major reason for the asphaltene polymerization. Benzene and nitrobenzene have a prominent inhibiting or disaggregation effect on the asphaltene aggregation, and they can be chosen as inhibiting and scavenging agents. Key words: asphaltene aggregate, molecular mechanics, molecular dynamics, interaction energy