Molecular Mechanisms of Suppressing Asphaltene Aggregation and Flocculation by Dodecylbenzenesulfonic Acid Probed by Molecular Dynamics Simulations

The behaviors of an asphaltene model compound, N-(1-undecyldodecyl)-N′-(5-carboxylicpentyl)-perylene-3,4,9,10-tetracarboxylbisimide (C5PeC11), in the absence and presence of an asphaltene inhibitor, dodecylbenzenesulfonic acid (DBSA), in n-heptane and toluene solutions were studied using molecular dynamics simulation. The presence of DBSA was found to reduce both the rate and degree of C5PeC11 aggregation while increasing the solvation of C5PeC11 molecules in the solvents studied. A higher concentration of DBSA molecules exhibited better dispersion of C5PeC11 molecules. Core–core stacking between polyaromatic cores was found to be the major driving force for C5PeC11 aggregation, while the association among the polar groups was a contributing factor for enhancing aggregation. DBSA molecules added after C5PeC11 aggregation were able to weaken the C5PeC11 aggregates by breaking the hydrogen bonds between C5PeC11 molecules within the aggregates. A protective shell of DBSA molecules around C5PeC11 aggregates was formed due to the interactions between DBSA and C5PeC11 and the self-association of DBSA molecules. The protective shell was beneficial for hindering the flocculation of C5PeC11 aggregates. The results provided a scientific basis for manipulating asphaltenes precipitation as often occurred in oil production wells and transport pipelines.