Aggregation behavior of model asphaltenes revealed from large-scale coarse-grained molecular simulations
File(s)aromatics_19_02_06.pdf (16.45 MB)
Accepted version
Author(s)
Jiménez-Serratos, Guadalupe
Totton, Tim S
Jackson, George
Muller, Erich A
Type
Journal Article
Abstract
Fully atomistic simulations of models of asphaltenes in simple solvents have allowed the study of trends in aggregation phenomena and the understanding of the role that molecular structure plays therein. However, the detail included at this scale of molecular modeling is at odds with the required spatial and temporal resolution needed to fully understand the asphaltene aggregation. The computational cost required to explore the relevant scales can be reduced by employing coarse-grained (CG) models, which consist of lumping a few atoms into a single segment that is characterised by effective interac- tions. In this work CG force fields developed via the SAFT-γ [Müller, E.A., Jackson, G. (2014) Annu. Rev. Chem. Biomolec. Eng., 5, 405–427] equation of state (EoS) provide a reliable pathway to link the molecular description with macroscopic thermophysical data. A recent modification of the SAFT-VR EoS [Müller, E.A. and Mejía, A. (2017) Langmuir, 33, 11518–11529], that allows parametrizing homonuclear rings, is selected as the starting point to propose CG models for polycyclic aromatic hydrocarbons (PAHs). The new aromatic-core parameters, along with others published for simpler organic molecules, are adopted for the construction of asphaltene models by combining different chemical moieties in a group-contribution fashion. We apply the procedure to two previously reported asphaltene models and perform Molecular Dynamics simulations to validate the coarse-grained representation against benchmark systems of 27 asphaltenes in pure solvent (toluene or heptane) described in a fully atomistic fashion. An excellent match between both levels of description is observed for cluster size, radii of gyration, and relative-shape-anisotropy-factor distributions. We exploit the advantages of the CG representation by simulating systems containing up to 2000 asphaltene molecules in explicit solvent investigating the effect of asphaltene concentration, solvent composi- tion, and temperature on aggregation. Upon employing large systems facilitated by the CG models, we observe stable continuous distributions of molecular aggregates at con- ditions away from the two-phase precipitation point. As a further example application, a widely accepted interpretation of cluster-size distributions in asphaltenic systems is challenged by performing system-size tests, reversibility proofs and time-dependence analysis. The coarse-graining procedure proposed is seen to be general and predictive, hence, can be applied to other asphaltenic molecular structures.
Date Issued
2019-03-14
Date Acceptance
2019-02-08
Citation
Journal of Physical Chemistry B, 2019, 123 (10), pp.2380-2396
ISSN
1520-5207
Publisher
American Chemical Society
Start Page
2380
End Page
2396
Journal / Book Title
Journal of Physical Chemistry B
Volume
123
Issue
10
Copyright Statement
© 2019 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry B, after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcb.8b12295
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
BP International Limited
Identifier
https://pubs.acs.org/doi/10.1021/acs.jpcb.8b12295
Grant Number
EP/E016340/1
EP/J014958/1
75195/ICAM15 (All) WS2
Subjects
Science & Technology
Physical Sciences
Chemistry, Physical
Chemistry
DIRECTIONAL ATTRACTIVE FORCES
EQUATION-OF-STATE
MESOSCALE SIMULATION
ASSOCIATING FLUIDS
FIELD PARAMETERS
DYNAMICS
SAFT
GASES
REPRESENTATION
PRECIPITATION
03 Chemical Sciences
09 Engineering
02 Physical Sciences
Publication Status
Published
Article Number
acs.jpcb.8b12295
Date Publish Online
2019-02-08