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

Abstract

Asphaltene aggregation is a subject under vivid discussion: There are several parameters one needs to determine before its behavior can be mastered and better target solutions can be tailored. The nature of asphaltene aggregation (colloidal or supramolecular) and the role of solvents and their mixtures are among the least understood parameters in asphaltene science. This paper addresses molecular dynamic simulations to correlate the aggregation properties of asphaltenes, their molecular structure and the concentration of these solvents. We show that the formation of the nanoaggregate depends, primarily, on the size of the conjugated core and on the eventual presence of polar groups capable of forming H-bonds. Heteroatoms on the conjugated core do not change their shape or type of aggregation but may induce stronger π − π interactions. The macroaggregation formation depends upon the length of the lateral chains of asphaltenes and also on the presence of polar groups at its end. Moreover, n-heptane and water may interact selectively with asphaltenes in function of their molecular architecture. Given this fact and the aggregation behavior observed, we advocate toward the assumption that a colloidal behavior of asphaltenes might be a particular case of a more general model, based on a supramolecular description.

Fractionation and Characterization of Petroleum Asphaltene: Focus on Metalopetroleomics

“…Molecular simulation methods provide an efficient way to explore the role of metalloporphyrins in asphaltene aggregation at the atomic scale. The investigation of asphaltene aggregation via a molecular simulation route should consider both the thermodynamic conditions [210,211] and chemical compositions [210,212,213] of the system. The competition between π-stacking interactions due to the aromaticity and the formation of hydrogen bonds due to the presence of heteroatoms demonstrated that the presence of hydrogen bonds is a key factor for the formation of large aggregates [213].…”

Assessing the Interfacial Activity of Insoluble Asphaltene Layers: Interfacial Rheology versus Interfacial Tension

“…At higher concentrations, these aggregates form clusters, which have smaller binding energies than the ones occurring within the nanoaggregates. Molecular dynamics simulations (MD) and dissipative particle dynamics (DPD) are consistent with the presence of nanoaggregates, in bulk, − and at liquid/liquid interfaces. , …”

Non-Exponential 1H and 2H NMR Relaxation and Self-Diffusion in Asphaltene-Maltene Solutions

“…The result can be a rather stable structure, as it is for example reported for the benzene dimer (dissociation energy (moderate hydrogen bonds: [ 29 ], van der Waals bonds: ) ) [ 30 , 31 ], though the importance of -stacking, that means the face-centered stacking arrangement of aromatic molecules, for aromatic–aromatic interactions is still under discussion [ 32 ]. Nevertheless, - interactions are considered as an important interaction among others responsible for asphaltene aggregation and precipitation [ 33 , 34 , 35 , 36 ]. Recently, an unusual type of parallel -stacking, the so-called pancake bonding, which occurs between radicals with highly delocalized electrons, as they occur in asphaltenes, gained attention with regard to the aggregation of asphaltenes [ 37 ].…”