Study of the Soret Effect in Hydrocarbon Chain/Aromatic Compound Mixtures

We studied the thermal diffusion behavior of equimolar mixtures of hydrocarbon chains in cyclohexane, p-xylene, and o-xylene experimentally and by reverse nonequilibrium molecular dynamics. The hydrocarbon chains heptane, 2,3-dimethylpentane, 2,4-dimethylpentane, 2-ethyl-3-methyl butadiene, and 2,4-dimethylpentadiene-1,3 with the same number of carbon atoms were considered in order to conserve the mass contribution and to investigate the shape influence on the Soret coefficient. Compared to the experimental data, the simulation results show the same trend. With increasing degree of branching, the Soret coefficient becomes larger. The negative Soret coefficient of the hydrocarbon chains indicates the enrichment in the warm side. We were able to find an empirical correlation between the properties of the pure components and the Soret coeffcients of the considered mixtures