Combination of Molecular Dynamics Simulation and Cosmo-Rs to Understand Asphaltenes Aggregation

Abstract

Asphaltenes interaction produces problems in oil transport and recovery, and understanding the association process is vital to improving economic and industrial production. Here, we propose COSMO-RS model in combination with molecular dynamics (MD) simulations, to complement the results obtained by Newtonian mechanics with quantum results to get reliable association data. Four asphaltene molecules were studied with toluene and heptane solvents. COSMO showed molecular interaction tendencies, which were later verified with MD. The average aggregation number was calculated through MD and turned out to be entirely dependent on the aromaticity due to 𝞹-𝞹 stacking. The aromatic rings are responsible for aggregation, while the sulfur heteroatom plays a less fundamental role. Viscosity is also related to the aggregation process; a higher tendency in aggregation increases the dynamic viscosity. Diffusion coefficients were correlated with the aromaticity, dipole moment, and molecular weight. Finally, a mathematical comparison between COSMO-RS and MD results is accomplished.

Keywords: Asphaltene, Molecular dynamics simulation, COSMO-RS, viscosity, diffusion coefficient