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Measurement of thermodiffusion coefficient in n-alkane binary mixtures: composition dependence
J A Madariaga1, C Santamaría, M Mounir Bou-Ali
1Department of Applied Physics II, University of Basque Country, Apdo. 644, 48080 Bilbao, Spain.
The Journal of Physical Chemistry. B
|May 1, 2010
Summary
The thermodiffusion coefficient in n-alkane mixtures correlates with component mass difference and fluid properties. This study provides an equation to calculate thermodiffusion coefficients for n-alkane binary mixtures.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Transport Phenomena
Background:
- Understanding molecular transport in liquid mixtures is crucial for chemical engineering processes.
- The thermodiffusion coefficient quantifies mass transfer driven by temperature gradients, a key phenomenon in separation technologies.
Purpose of the Study:
- To measure and analyze the thermodiffusion coefficient in n-alkane binary mixtures.
- To develop a predictive model for the thermodiffusion coefficient based on mixture properties.
- To compare experimental findings with existing theories and data for dilute polymer solutions.
Main Methods:
- Thermogravitational technique was employed to measure the thermodiffusion coefficient.
- Binary mixtures of n-alkanes, including n-dodecane/n-heptane, were studied at various concentrations.
- Measurements were conducted at a constant temperature (25°C) and pressure (1 atm).
Main Results:
- The thermodiffusion coefficient was found to be proportional to the mass difference between mixture components.
- A direct relationship was observed between the thermodiffusion coefficient and the ratio of thermal expansion coefficient to viscosity.
- A linear dependence of the thermodiffusion coefficient on mass fraction was established.
Conclusions:
- An equation was derived to calculate the thermodiffusion coefficient, enabling determination of infinite dilution values.
- The findings support the applicability of the derived equation for n-alkane mixtures and offer insights into thermodiffusion in polymer solutions.
- The thermodiffusion coefficient can be accurately predicted using properties of pure components, such as viscosity and thermal expansion.
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