Aggregation of model asphaltenes: a molecular dynamics study

Abstract

Natural asphaltenes are defined as polyaromatic compounds whose chemical composition and structure are dependent on their geological origin and production history, hence are regarded as complex molecules with aromatic cores and aliphatic tails that occur in the heaviest fraction of crude oil. The aggregation of asphaltenes presents a range of technical challenges to the production and processing of oil. In this work we study the behaviour of the model asphaltene-like molecule hexa-tert-butylhexa-peri-hexabenzocoronene (HTBHBC) using molecular dynamics simulation. It was found that the regular arrangement of the tert-butyl side chains prevents the formation of strongly-bound dimers by severely restricting the configurational space of the aggregation pathway. In contrast, a modified molecule with only 3 side chains is readily able to form dimers. This work therefore confirms the influence of the molecular structure of polyaromatic compounds on their aggregation mechanism, and reveals the unexpected design rules required for model systems that can mimic the behavior of asphaltenes.

Enhanced Computational Sampling of Perylene and Perylothiophene Packing with Rigid-Body Models

“…50 Indeed, simulations that include atomistic representations or explicit solvents generally access fewer than 150 ns for fewer than 30 molecules. 46,47,51−53 Wang and Ferguson used coarse-grained models and GPU acceleration to access 500 ns trajectories for 200 asphaltenes at 27 state points, demonstrating the sampling advantages of simplified models and hardware accelerators. 48 The work presented here extends the ideas of Wang and Ferguson, demonstrating that rigid-body models, combined with GPU accelerators can be used to efficiently sample thousands of thermodynamic state points, by equilibrating systems of 200 molecules for over 100 ns each.…”

CO2-Fluid-Rock Interactions and the Coupled Geomechanical Response during CCUS Processes in Unconventional Reservoirs

“…A flexible structure is used to deal with carbon dioxide. Visual molecular dynamics (VMD) was used to prepare visualizations [188]. Mehana et al studied the system's physical conditions and composition on asphaltene aggregation dynamics [189].…”

Clustering behaviour of polyaromatic compounds mimicking natural asphaltenes

“…52 Optimized potential for liquid simulations/all atoms (OPLS/AA) force field was employed. 53,54 A protocol previously used by this group 55 was used to build an HTBHBC model and its derivative (DevHTBHBC). One dimer formed of two HTBHBC molecules was constructed and placed by turn in a toluene and n-heptane solvated simulation box.…”

“…Our previous molecular simulation work suggests that modifications to the structure of HTBHBC could result in different aggregation pathways. 55 1 H-NMR spectra were acquired at time intervals 1, 24, 168, and 336 hours for the 20 mg/mL suspension to identify the chemical nature of the compounds that were present in the liquid phase and in the solid deposit (re-dispersed in toluene), respectively. The peak at 9.76 ppm (see Figure 2) that corresponds to the aromatic protons of HTBHBC was chosen as the reference peak.…”