A multiscale approach to the simulation of asphaltenes

The molecular structures of asphaltenes contained in crude oil samples were determined and their behaviour in solution was studied at a full atomistic level by combining computer graphics, quantum mechanical calculations and forcefield based simulations. The definition of an average molecule for each asphaltene sample was carried out by model building likely molecular structures within a graphical interface, supported by the available experimental data. The structural relaxation of all produced candidates was achieved with density functional theory methods, allowing the final selection of a single molecular structure for each asphaltene, in a collection of 17 samples. Two of the produced molecules were adopted in the simulation of asphaltene aggregation properties in four different solvents. The spontaneous formation of supramolecular clusters along time in concentrated asphaltene solutions was followed by classical molecular dynamics under periodic boundary conditions. The Hildebrand solubility parameter was calculated for the whole collection of asphaltene structures, as a practical example of obtaining useful physicochemical properties from molecular simulations.