Understanding the Aggregation of Model Island and Archipelago Asphaltene Molecules near Kaolinite Surfaces using Molecular Dynamics

The solubility of asphaltenes in hydrocarbons changeswith pressure,composition, and temperature, leading to precipitation and deposition,thereby causing one of the crucial problems that negatively affectsoil production, transportation, and processing. Because, in some circumstances,it might be advantageous to promote asphaltene agglomeration intosmall colloidal particles, molecular dynamics simulations were conductedhere to understand the impacts of a chemical additive inspired bycyclohexane on the mechanism of aggregation of model island and archipelagoasphaltene molecules in toluene. We compared the results in the presenceand absence of a kaolinite surface at 300 and 400 K. Cluster sizeanalyses, radial distribution functions, angles between asphaltenes,radius of gyration, and entropic and energetic calculations were usedto provide insights on the behavior of these systems. The resultsshow that the hypothetical additive inspired by cyclohexane promotedthe aggregation of both asphaltenes. Structural differences wereobserved among the aggregates obtained in our simulations. These differencesare attributed to the number of aromatic cores and side chains onthe asphaltene molecules as well as to that of heteroatoms. For theisland structure, aggregation in the bulk phase was less pronouncedthan that in the proximity of the kaolinite surface, whereas the oppositewas observed for the archipelago structure. In both cases, the additivepromoted stacking of asphaltenes, yielding more compact aggregates.The results provided insights into the complex nature of asphalteneaggregation, although computational approaches that can access longertime and larger size scales should be chosen for quantifying emergentmeso- and macroscale properties of systems containing asphaltenesin larger numbers than those that can currently be sampled via atomisticsimulations.

Automated summary

Chemical additive inspired by cyclohexane promotes the aggregation of asphaltene molecules in toluene, forming small colloidal particles. The study used molecular dynamics simulations to investigate the behavior of model island and archipelago asphaltene structures in the presence of the additive. The results show that the additive promotes stacking of asphaltenes, resulting in more compact aggregates.