Thermodiffusion coefficients of binary and ternary hydrocarbon mixtures.

In this study, we have measured the thermodiffusion coefficients of six hydrocarbon liquid ternary mixtures at 25 degrees C using the thermogravitational technique. Mixtures of 1,2,3,4-tetrahydronaphthalene-isobutylbenzene-n-dodecane at four different concentrations and 1,2,3,4-tetrahydronaphthalene-isobutylbenzene-n-decane at two concentrations have been considered. We have used a plane-thermogravitational column with a small gap dimension to improve the accuracy of the recently reported data. The obtained results have been confirmed by measurements in a cylindrical column. We have also measured the thermodiffusion coefficients of 13 binary mixtures between the different components of ternaries in order to analyze the validity of the additive rule proposed in the literature to determine thermodiffusion coefficients of ternary mixtures from binary thermodiffusion data. A new correlation based on column separation, which reproduces the data within the experimental error, is proposed.

Determination of thermal diffusion coefficient in equimolar n-alkane mixtures: Empirical correlations.

In this article we determined the thermal diffusion coefficient (D(T)) in equimolar mixtures of n-alkanes nC(i)-nC(12) (i=5,6,7,8,9,17,18), nC(i)-nC(10) (i=5,6,7,15,16,17,18), and nC(i)-nC(6) (i=10,12,14,16,18) at 25 degrees C and at atmospheric pressure using the thermogravitational technique. The results obtained from this study together with the previously published ones in the series of nC(i)-nC(18) (i=5,6,7,8,9,10,11,12,13) show that the main parameter that determines D(T) in each series is in association with the molecular weights of the mixture's components. However, an empirical quantitative correlation has been obtained between D(T), the molecular weights of the components, the viscosity, and the thermal expansion coefficient of the mixtures. This is the first report of a closely accurate correlation for D(T) in liquid mixtures.