Sensitivity of the aggregation behaviour of asphaltenes to molecular weight and structure using molecular dynamics

Sensitivity of the aggregation behaviour of asphaltenes to molecular weight and structure using molecular dynamics

Type	Journal Article
Author	Philippe Ungerer
Author	David Rigby
URL	http://dx.doi.org/10.1080/08927022.2013.850499
Volume	40
Issue	1-3
Pages	115-122
Publication	Molecular Simulation
Date	January 2, 2014
Abstract	Asphaltenes are heavy crude oil compounds, defined as soluble in toluene and precipitating in alkanes. To understand the relation between asphaltene structure and aggregation, authors conducted equilibrium molecular dynamics with Large-scale Atomic and Molecular Massively Parallel Software (LAMMPS), using the atomistic force field PCFF+ in the MedeA® environment. The following three molecular models were considered: the continental model (1350 g/mol) having a large polyaromatic core and long alkyl chains, the island model (780 g/mol) having a smaller polyaromatic unit and shorter chains and the archipelago model (1350 g/mol) having three polyaromatic nuclei bridged with alkyl chains. The aggregation in a given solvent was monitored by visualizing solvent-free configurations over 15 ns trajectories at 350 K. Nanoaggregates were characterized by stacked polyaromatic units separated by 0.33–0.4 nm. Irreversible aggregation was found with the continental model in both solvents. Aggregation of the island model was significant in n-heptane and low in toluene. The archipelago model did not aggregate significantly. Results confirmed that the island model is a reasonable average model of asphaltenes.