Theoretical Study of the Prohibited Mechanism for Ethylene/Vinyl Acetate Co-polymers to the Wax Crystal Growth

Abstract

To understand the effect of pour point depressants (PPD) on the wax growth is important for designing PPD additives for use with different oils with high efficiency and good economics. In our current study, molecular mechanics, molecular dynamics, and quantum mechanics calculations were performed to investigate the prohibited mechanism of ethylene/vinyl acetate (EVA) additives on the paraffin deposition in oils. On the wax surface, a single C18 molecule and clusters were preferably deposited on the wax surface (010) in a parallel conformation, which resulted in the formation of large blocks of wax crystal. MD simulation indicated that the linear conformation of EVA was more favorable to be adsorbed onto the carbon backbone of the wax surface (010) with the polar fragments of vinyl acetate staying upside of the surface. Furthermore, four EVA molecules can efficiently optimize the inhibition effect for the deposition of the solute C18 molecules over 10x8 size wax surface (010). According to the simulation results, a simplified rational model was established to estimate the minimum dosage of EVA-type PPD for fuels with different paraffin contents. In a certain degree, this simplified model has provided an effective route to correlate microstructures and the properties of polymer-involving systems, which will shed light on the application of theoretical studies in industries.

Recent advances on mitigating wax problem using polymeric wax crystal modifier

“…Theoretical studies of wax inhibition using EVA copolymers were performed by Lindeman and Allenson (2005) and Zhang et al (2008). Lindeman and Allenson provided a new approach using theoretical modeling to correlate the molecular structure of polymer with the experimental physical properties, which can be used to predict the wax inhibition performance of EVA copolymers.…”

Preparation of cubane-1,4-dicarboxylate–Zn–Al layered double hydroxide nanohybrid: comparison of structural and optical properties between experimental and calculated results

“…At rst, DFT method was used to get the geometry optimization conguration for the cubane-dc anions. [44][45][46] The rst step in arranging models of intercalates was the construction of the host positively charged Zn-Al-LDH layers. Fundamental works on the modeling for the rst developed CLayFF 30 force eld (FF) that was particularly appropriate to deal with LDHs containing Si, Al, Mg, Ca, Fe, and Li, and this force eld was more subsequently implemented and validated 31 with parameters for LDHs in which M(II) was Zn 2+ cation.…”

Blends of surfactants and EVA as cold flow improvers for diesel fuels

“…Owing to the wide variety of oil components, many polymers were developed as pour point depressants (PPD) to affect the flow property of diesel via adjusting the precipitation [2,3]. In general, these polymers have a wax-like paraffin part, which provides the interaction between the additive and paraffin, and a polar segment that is responsible for modifying the morphology of wax crystals [4,5].…”