Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites
The self-diffusion of hydrogen in Ca2+-, Mg2+- and Ba2+-exchanged X zeolites (Mg46X, Ca46X, and Ba46X) has been studied by molecular dynamics (MD) simulations for various temperatures and loadings. The results indicate that in the temperature range of 77–298 K and the loading range of 1–80 molecules...
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Wiley
2014-01-01
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| Series: | International Journal of Chemical Engineering |
| Online Access: | http://dx.doi.org/10.1155/2014/701057 |
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| author | Du Xiaoming |
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| author_sort | Du Xiaoming |
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| description | The self-diffusion of hydrogen in Ca2+-, Mg2+- and Ba2+-exchanged X zeolites (Mg46X, Ca46X, and Ba46X) has been studied by molecular dynamics (MD) simulations for various temperatures and loadings. The results indicate that in the temperature range of 77–298 K and the loading range of 1–80 molecules/cell, the self-diffusion coefficients are found to range from 1.2×10-9 m2·s−1 to 2.3×10-7 m2·s−1 which are in good agreement with the experimental values from the quasielastic neutron scattering (QENS) and pulse field gradients nuclear magnetic resonance (PFG NMR) measurements. The self-diffusion coefficients decrease with loading due to packing of sorbate-sorbate molecules which causes frequent collusion among hydrogen molecules in pores and increases with increasing temperature because increasing the kinetic energy of the gas molecules enlarges the mean free path of gas molecule. The mechanism of diffusion of hydrogen molecules in these zeolites is transition diffusion. Knudsen diffusion occurs at low loading and the molecular bulk diffusion occurs at higher loading. For given temperature and loading, the self-diffusion coefficients decrease in the order Ba46X<Mg46X<Ca46X, due to the different sizes and locations of the divalent cations. Moreover, the effect of concentration of molecular hydrogen on self-diffusion coefficient also is analyzed using radial distribution function (RDF). |
| format | Article |
| id | doaj-art-86dc6d4037124767a59e06d5b2a3aa24 |
| institution | Kabale University |
| issn | 1687-806X 1687-8078 |
| language | English |
| publishDate | 2014-01-01 |
| publisher | Wiley |
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| series | International Journal of Chemical Engineering |
| spelling | doaj-art-86dc6d4037124767a59e06d5b2a3aa242025-08-20T03:37:53ZengWileyInternational Journal of Chemical Engineering1687-806X1687-80782014-01-01201410.1155/2014/701057701057Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X ZeolitesDu Xiaoming0School of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110159, ChinaThe self-diffusion of hydrogen in Ca2+-, Mg2+- and Ba2+-exchanged X zeolites (Mg46X, Ca46X, and Ba46X) has been studied by molecular dynamics (MD) simulations for various temperatures and loadings. The results indicate that in the temperature range of 77–298 K and the loading range of 1–80 molecules/cell, the self-diffusion coefficients are found to range from 1.2×10-9 m2·s−1 to 2.3×10-7 m2·s−1 which are in good agreement with the experimental values from the quasielastic neutron scattering (QENS) and pulse field gradients nuclear magnetic resonance (PFG NMR) measurements. The self-diffusion coefficients decrease with loading due to packing of sorbate-sorbate molecules which causes frequent collusion among hydrogen molecules in pores and increases with increasing temperature because increasing the kinetic energy of the gas molecules enlarges the mean free path of gas molecule. The mechanism of diffusion of hydrogen molecules in these zeolites is transition diffusion. Knudsen diffusion occurs at low loading and the molecular bulk diffusion occurs at higher loading. For given temperature and loading, the self-diffusion coefficients decrease in the order Ba46X<Mg46X<Ca46X, due to the different sizes and locations of the divalent cations. Moreover, the effect of concentration of molecular hydrogen on self-diffusion coefficient also is analyzed using radial distribution function (RDF).http://dx.doi.org/10.1155/2014/701057 |
| spellingShingle | Du Xiaoming Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites International Journal of Chemical Engineering |
| title | Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites |
| title_full | Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites |
| title_fullStr | Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites |
| title_full_unstemmed | Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites |
| title_short | Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites |
| title_sort | molecular dynamics study of hydrogen on alkali earth metal cations exchanged x zeolites |
| url | http://dx.doi.org/10.1155/2014/701057 |
| work_keys_str_mv | AT duxiaoming moleculardynamicsstudyofhydrogenonalkaliearthmetalcationsexchangedxzeolites |