Molecular modelling and simulation of asphaltenes and bituminous materials

Abstract

Molecular level calculations targeting the behaviour of asphaltenes, resins and bitumens are reviewed with an objective of relating molecular structure and interactions to macroscale physical, chemical and mechanical properties. The review discusses molecular dynamics simulations of asphaltenes and bitumens and briefly summarises structure elucidation, quantum mechanics, coarse graining and thermodynamic model approaches. The molecular architecture of asphaltenes in simulations plays an important role, with continental and archipelago asphaltenes showing different packing tendencies in isolated systems and solutions. Alkyl side chains bonded to fused aromatic rings interfere with multiple ring stacking layers. Diversity of molecular structure increases asphaltene aggregate formation via alternatives that improve packing. Strongly bent aromatic rings are vacuum simulation artefacts and are absent when enough molecules can solvate unbent fused aromatic rings. Bitumen simulations provide methods to estimate the influence of asphaltenes on dynamic properties. Future needs include methods to incorporate chemically specific parameters into modelling approaches that address larger length and longer timescales.

Keywords:

• asphaltene
• model asphalt
• model bitumen
• molecular dynamics
• molecular modelling
• statistical mechanics

Acknowledgements

This work was supported by funds provided by the Rhode Island Department of Transportation (Research and Technology Division), the University of Rhode Island Transportation Center and the Asphalt Research Consortium of the Federal Highway Administration (contract DTFH61-07-H-00009), via a subcontract from the Western Research Institute.