Effect of asphaltenes structure on interfacial properties: A dissipative particle dynamics study

Asphaltenes are important components of crude oil that stabilize oil-water emulsions. Due to their complex molecular nature, the connections between molecular structure and interfacial properties of asphaltenes remain unclear. In this work, the effects of polyaromatic cores size, length and the number of aliphatic side chains, and heteroatoms on the structural properties of asphaltenes in oil-water system are investigated by dissipative particle dynamics (DPD). The results show that the asphaltene molecules with larger aromatic cores are better for reducing the interfacial tension (IFT) of the system. The relationship between the interfacial activity of asphaltenes and the length of aliphatic side chains is not monotonic as the concentration increases. Asphaltene molecules with intermediate length and shorter length aliphatic side chains are effective in reducing IFT at lower and higher concentrations, respectively. The asphaltenes with more aliphatic side chains contribute more to the reduction of IFT at lower concentrations, but the side chains can hinder the adsorption of asphaltenes at the interface, which is not conducive to the stability of the system at higher concentrations. In addition, oxygen atoms in the molecular structure of asphaltenes are the key factors that promote the adsorption of asphaltenes to the interface and reduce the IFT. This detailed investigation of the behavior of asphaltenes would be useful to understand the role of asphaltenes in the formation of oil-water emulsions.