Molecular Dynamics Simulation of the Microscopic Interaction Mechanism between Asphaltenes and Wax Molecules/Aggregates Considering the Asphaltene Structure and Wax Carbon Number

Due to asphaltene's complex structure and its status as the most polar and surfactant component, it is extremely challenging to investigate the interaction between asphaltenes and wax molecules. In this study, we employ molecular dynamics methods to investigate the interaction mechanisms between asphaltenes including the isolated-island-type and the archipelago type and wax molecules with carbon numbers of 20, 25, and 30. By analyzing the aggregation rates, cluster sizes, distributions, and interaction energies of asphaltenes and wax molecules during the simulation process, we were able to elucidate that the branched structures of the isolated-island-type asphaltenes and the aromatic ring structures of the archipelago type asphaltenes play a dominant role in their interactions with wax molecules, which leads to a diffusion coefficient for island-type asphaltenes that is about 15% higher than that for archipelago-type asphaltene. In addition, as the wax molecules (C20, C25, and C30) aggregated, they tend to form elliptical structures, which exhibit affinity with the aromatic ring structure of asphaltenes. However, when wax molecules with C20, C25, and C30 are mixed and aggregated, the resulting ellipse-like structures have short chains at their ends due to varying wax molecule lengths. In this case, these short chains are attracted to the branched structures of asphaltenes, thereby enhancing the interaction between asphaltenes and waxes.