Wax Inhibition by Ethylene-Vinyl Acetate Using United Atom Molecular Simulations

We used the TraPPE-UA [Martin, M. G.; Siepmann, J. I. J. Phys. Chem. B 1998, 102, 2569] scheme to investigate the inhibition of crystal growth in an octacosane matrix embedded with an ethylene-vinyl acetate (EVA) inhibitor. Through elucidating the phenomena of EVA-induced morphological transitions, we demonstrated that an EVA chain needs to possess suitable configurations with an optimal concentration of polar vinyl acetate (VA) side units, minimal distance between VA units subject to the constraint that VA units remain separate, and symmetrical location distributions of VA units to achieve the best inhibition performance. Furthermore, we revealed that the EVA inhibition was triggered by distortions of the EVA backbone section due to the strong affinity of VA components to neighboring molecules. We obtained an agreement with the experimental characterizations and provided an insight into the solution for the problem of paraffin crystallizations in crude oil pipelines.