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【答案】应助回帖
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du511(sunshan4379代发): 金币+5 2014-09-05 09:23:57
sunshan4379: LS-EPI+1, 感谢应助！ 2014-09-05 09:24:06
Accession number:
20141317525876
Title:
Molecular dynamics study of hydrogen on alkali-earth metal cations exchanged X zeolites
Authors:
Xiaoming, Du1
Author affiliation:
1School of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110159, China
Corresponding author:
Xiaoming, D. (du511@163.com)
Source title:
International Journal of Chemical Engineering
Abbreviated source title:
Int. J. Chem. Eng.
Issue date:
2014
Publication year:
2014
Article number:
701057
Language:
English
ISSN:
1687806X
E-ISSN:
16878078
Document type:
Journal article (JA)
Publisher:
Hindawi Publishing Corporation, 410 Park Avenue, 15th Floor, 287 pmb, New York, NY 10022, United States
Abstract:
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 m 2·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 Ba 46 X < Mg 46 X < Ca 46 X, 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). © 2014 Du Xiaoming.
Number of references:
29
Main heading:
Loading
Controlled terms:
Calcium - Diffusion in liquids - Fluidized beds - Hydrogen - Kinetics - Molecular dynamics - Molecules - Positive ions - Zeolites
Uncontrolled terms:
Experimental values - Increasing temperatures - Molecular dynamics simulations - Molecular hydrogen - Pulse field gradients - Quasielastic neutron scattering - Radial distribution functions - Self-diffusion coefficients
Classification code:
549.2 Alkaline Earth Metals - 672 Naval Vessels - 801.4 Physical Chemistry - 802.1 Chemical Plants and Equipment - 804 Chemical Products Generally - 804.2 Inorganic Compounds - 931 Classical Physics; Quantum Theory; Relativity
DOI:
10.1155/2014/701057
Database:
Compendex
Compilation and indexing terms, © 2014 Elsevier Inc. |
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