Molecular Simulations and Theoretical Predictions for Adsorption and Diffusion of CH ₄ /H ₂ and CO ₂ /CH ₄ Mixtures in ZIFs

Journal Article · Mon Jun 06 04:00:00 EDT 2011 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/jp203053h· OSTI ID:1053694

Liu, Jinchen ^[1]; Keskin, Seda ^[2]; Sholl, David S. ^[3]; Johnson, J. Karl ^[1]

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1. Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States; National Energy Technology Laboratory, Pittsburgh, Pennsylvania 15236, United States
2. Department of Chemical and Biological Engineering, Koç University, Istanbul, 34450, Turkey
3. School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0100, United States

Adsorption and diffusion of CO{sub 2}/CH{sub 4} and CH{sub 4}/H{sub 2} mixtures were computed in zeolite imidazolate frameworks (ZIFs), ZIF-68 and ZIF-70, using atomically detailed simulations. Adsorption selectivity, diffusion selectivity, and membrane selectivity of ZIFs were calculated based on the results of atomistic simulations. Mixture adsorption isotherms predicted by the ideal adsorbed solution theory agree well with the results of molecular simulations for both ZIFs. Mixture diffusivity calculations indicate that diffusion of CH{sub 4} is increased with increasing concentration of H{sub 2} in the CH{sub 4}/H{sub 2} mixture, while the diffusivity of H{sub 2} decreases with increasing CH{sub 4} concentration. In contrast, the diffusivity of CH{sub 4} is essentially independent of the concentration of CO{sub 2} in the CO{sub 2}/CH{sub 4} mixture, while CO{sub 2} diffusivity decreases with increased CH{sub 4} loading, even though the diffusivity of CH{sub 4} is substantially larger than that of CO{sub 2}. This unusual behavior can be explained in terms of differences in adsorption site preferences due to charge–quadrupole interactions.

• Research Organization: National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• DOE Contract Number: FE0004000
• OSTI ID: 1053694
• Report Number(s): TPR-3453
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 25 Vol. 115; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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