Study of the pressure effect on the thermodiffusion behavior in multicomponent n-alkane mixtures by using non-equilibrium molecular dynamics

The influence of high pressure on the Soret effect of multicomponent n-alkanes mixtures was investigated with the non-equilibrium molecular dynamics method to provide simulation support to the SJ10/SCCO experiments. In this work, n-pentane/n-heptane/n-decane ternary mixtures and methane/n-pentane/n-heptane/n-decane quaternary mixtures were built and simulated under the same situations as the space experiments. TraPPE-UA force field and eHEX algorithm were employed in Soret effect simulations, and three different amounts of heat (ΔQ) were applied in each mixture. The simulated thermodiffusion ratios (k T ) were compared with the data from other literature. In ternary mixtures, the k T values were influenced by the pressure, but the migration directions and separation relationship of the components did not change. While in quaternary mixtures, the strong and weak separation relationships of the two lowest separated components changed. The results demonstrated that the high pressure weakens the Soret effect in multicomponent n-alkane mixtures to an extent and may affect more in the mixture composed of more components.