Molecular dynamics simulation guiding the improvement of EVA-type pour point depressant

Addition of pour point depressants (PPDs) has been proved to be an efficient way to inhibit wax deposition of diesel fuels. However, the complexity of the oil is far beyond current commercial PPD products. So far it mainly depends on syntheses of numerous candidate compounds followed by repeating experimental measurements in order to improve the efficiency of PPDs. In this article, molecular dynamic simulation was successfully used to investigate the interaction between crystal planes of wax and EVA, as well as its derivatives with different branches, based on the model of wax. Side chain effects on adsorption energy and equilibrium adsorption conformations were studied under different kind and number of branches. It was concluded that side chains introduced by propylene were benefit to the affinity between the EVA-type molecules and alkanes in the wax plane, comparing with those branches introduced by butylenes. MD simulation calculations indicated that EVAP with one branch adjacent to the VA group would be a better PPD additive than EVA in diesel fuels, which has been proved in our experimental measurements. Therefore, the MD simulation is a promising method not only for exploring the interaction mechanism in polymer system, but also for directing the design of new candidates of PPD.