Abstract: The existing states of different diesel molecules at different temperatures were simulated by molecular dynamics. It is found that the main reason for the aggregation and crystallization of n-alkanes at low temperatures is the changes of molecular conformation from “curved” to “straight” as the temperature decreases, and that keeping n-alkanes in curved conformation is beneficial to improve the low temperature flow performance of n-alkanes system. The conformation changes of existing states of n-alkane molecules in diesel containing low temperature flow improver (CFI) when the temperature decreases were investigated. The results show that CFI can change the molecular torsion angle by the intermolecular force to keep the curved comformations, resulting in a weak intermolecular force and diminished order and compactness of n-alkanes. The CFI molecules that can extend to multiple directions, contain multiple high degree curved molecular segments and strong interaction with n-alkanes can significantly keep n-alkane molecules in curved conformation.

Key words: cold flow improver, diesel molecules, molecular conformation, intermolecular interaction, molecular dynamics simulation