Molecular simulation of diffusion of hydrogen, carbon monoxide, and water in heavy n -alkanes

Zoi A. Makrodimitri, Dominik J M Unruh, Ioannis Economou

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The self-diffusion and mutual diffusion coefficients of hydrogen (H 2), carbon monoxide (CO), and water (H2O) in n-alkanes were studied by molecular dynamics simulation. n-Alkane molecules were modeled based on the TraPPE united atom force field. NPT molecular dynamics (MD) simulations were performed for n-C12 to n-C96 at different temperature and pressure values to validate the accuracy of the force field. In all cases, good agreement was obtained between literature experimental data and model predictions for the density and structure properties of the n-alkanes. Subsequently, the self-diffusion coefficient of the three light components in the various n-alkanes was calculated at different temperatures. Model predictions were in very good agreement with limited experimental data. Furthermore, the Maxwell-Stefan diffusion coefficients of H2 and CO in two n-alkanes, namely n-C12 and n-C28, were calculated based on long MD NVT simulations for different solute concentrations in the n-alkanes. Finally, the Fick diffusion coefficient of the components was calculated as a product of the Maxwell-Stefan diffusion coefficient and a thermodynamic factor. The latter was estimated from the statistical associating fluid theory (SAFT). The Fick diffusion coefficient was found to be higher than the Maxwell-Stefan diffusion coefficient for H2 and CO in n-C 28. The empirical Darken equation was used to estimate the Maxwell-Stefan diffusion coefficient, and calculations were found to be in good agreement with simulation results.

Original languageEnglish
Pages (from-to)1429-1439
Number of pages11
JournalJournal of Physical Chemistry B
Issue number6
Publication statusPublished - 17 Feb 2011
Externally publishedYes


ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry
  • Materials Chemistry

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