Insight into the mechanism of asphaltene disaggregation by alkylated treatment: An experimental and theoretical investigation

Abstract

Mechanism of asphaltene disaggregation by alkylated treatment was revealed experimentally and theoretically. Significant increases both in inter-sheet distance and critical aggregation concentration were clearly observed after alkylation reaction of asphaltenes, indicating that alkylated treatment could well disaggregate asphaltenes and retard them reaggregating, further confirmed by molecular dynamics (MD) simulations. MD results indicate that grafting side-chains with moderate chain lengths, introducing isoalkyl side-chains with larger steric hindrance, or increasing the number of grafted side-chains, is more readily to achieve better disaggregation effect on asphaltene aggregate. Furthermore, a series of non-covalent interactions (NCIs) analyses was performed to elucidate diverse driving forces for disaggregating asphaltenes. Especially via the van der Waals potential analysis, newly developed in recent years, it was found that aside from enhancing exchange-repulsion, the introduction of side-chains brings additional dispersion attraction orthogonal to π-π stacking, thus disrupting the regularity of accumulation of asphaltenes; moreover, through averaged reduced density gradient (aRDG) analysis and adjuvant MD simulations, the role of solvents in affecting the disaggregation behavior was elucidated. This research provides an effective method to disaggregate asphaltenes and contributes to solving the problems caused by asphaltenes aggregation.