Influence of solvent effect, temperature, and pressure on the aggregation behavior of island model asphaltene: a molecular dynamics study.

The aggregation of asphaltene molecules strongly affects crude oil stability and flow assurance, yet the microscopic mechanisms remain unclear. In this study, molecular dynamics simulations were performed on the representative island-type asphaltene to investigate the effects of solvent composition, temperature, and pressure on its aggregation behavior. Thermodynamic and structural analyses were conducted using total energy, solvent accessible surface area (SASA), and intermolecular hydrogen bonding. Results show that solvent composition is the dominant factor: low toluene fractions (≤30%) enhance van der Waals interactions and promote compact aggregates, while higher toluene contents increase solvation and suppress aggregation. Temperature exhibits a nonlinear influence - moderate temperatures (60-70 °C) yield the lowest energy and most stable aggregates, whereas excessive or insufficient thermal motion at high or low temperatures weakens aggregation. Pressure has a secondary but notable effect: at moderate pressure (∼2 MPa), aggregates become looser due to enhanced solvation, while both low and high pressures favor denser, more stable configurations. Overall, asphaltene aggregation is jointly controlled by solvent polarity, temperature, and pressure, providing molecular-level insights for predicting and mitigating asphaltene deposition in petroleum systems.