Molecular Dynamics Simulation of the Heat-Induced Relaxation of Asphaltene Aggregates

Abstract

The energy-minimum conformation calculated by molecular mechanics−molecular dynamics simulation for the asphaltene obtained from the vacuum residue of Khafji crude oils showed that structures aggregated through several noncovalent interactions are the most stable. Changes induced in aggregated structures by heating were investigated using molecular dynamics calculations. The simulation showed that the hydrogen bond between asphaltene molecules dissociated at 523 K, while aromatic−aromatic stacking interactions appeared to be stable. At 673 K, however, some stacking interactions could be disrupted, but some stable aggregates remained even at this high temperature where some decomposition reactions would be expected to occur. Simulations on two model compounds were carried out to investigate the effects of aliphatic chains and polar functional groups on the stability of asphaltene aggregates during heating. Aliphatic chains and polar functional groups contributed to the stability of aggregates; in simulations of “imaginary” structures in which the original structure was modified by removing the aliphatic side chains and then replacing heteroatoms with carbon, dissociation occurred at lower temperatures at to greater extents than for the original structure; van der Waals interactions between aliphatic chains acted cooperatively to stabilize the asphaltene aggregates.

The influence of asphaltene-resin molecular interactions on the colloidal stability of crude oil

“…As an example, in an asphaltene-resin (trimer), A-R(trimer), the contribution of the side chains to stability of the system is 8.9 kcal/mol. This is in line with Takanohashi et al's results, which emphasize the stabilizing effects of aliphatic side chains [94].…”

Investigating the Interactions of the Saturate, Aromatic, Resin, and Asphaltene Four Fractions in Asphalt Binders by Molecular Simulations

“…Asphaltenes molecules of At-N+S+O and At-N+2S+O in Figure 1 were provided by Takanohashi from NMR as a kind of Kuwait asphalts [29], the same oil resource as Q70# and H90#. For sulfur existing condition, J.…”

Asphaltene aggregation studied by molecular dynamics simulations: role of the molecular architecture and solvents on the supramolecular or colloidal behavior

“…Both the chemical composition and the molecular cartography (i.e, how the chemical elements form the various structures) play a key role in the understanding of this problematic phenomenon (Headen et al 2017). In this way, a clear and well-determined structure-function link between molecular structure and aggregation behavior of asphaltenes is highly sought after so that these nasty effects can be avoided, and new refining techniques, asphaltene inhibitors and catalysts can be developed, and so on (Murgich et al 1996;Takanohashi et al 2003;Ortega-Rodriguez et al 2004).…”