Molecular dynamics studies of interaction between asphaltenes and solvents

TL;DR

This study uses molecular dynamics simulations to analyze how different asphaltenes interact with water and ortho-xylene, revealing the roles of hydrogen bonds and electrostatic versus van der Waals forces in these interactions.

Contribution

It provides detailed insights into the molecular interactions between various asphaltenes and solvents, highlighting the influence of functional groups and interaction types.

Findings

Hydrogen bonds form between asphaltenes and water due to polar groups.

Electrostatic and van der Waals interactions significantly affect asphaltene-water interactions.

Temperature influences potential energies and hydrogen bond formation, while pressure has minimal effect.

Abstract

Understanding of the molecular interaction between asphaltenes and other molecules, which may act as its solvents, provides insights into the nature of its stability in petroleum fluids and its phase transitions. Molecular dynamics simulations were performed and reported here on systems consisting of a single asphaltene molecule and pure solvents. Three types of asphaltenes with different architectures, molecular weights, and heteroatoms content were investigated. Water and ortho-xylene were selected to be the interacting solvents. All simulations were performed by using GROMACS software. OPLS_AA potential model for hydrocarbons and SPC/E potential model for water were used in simulations. It was shown that the polar functional groups in asphaltenes were responsible for generating hydrogen bonds (HBs) between asphaltenes and water. It was also demonstrated that both electrostatic (ES) and van der Waals (vdW) interaction energies between asphaltenes and water had important roles. On the contrary, ES between asphaltenes and ortho-xylene had a minor effect as compared with the vdW. In all cases, potential energies increased rather slightly when the pressure was boosted. Moreover, they decreased noticeably when the temperature was raised. HBs between asphaltenes and water were not influenced by pressure change. Additionally, they increased slightly when the temperature was dropped.