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Describing binary mixture diffusion in carbon nanotubes with the Maxwell-Stefan equations. An investigation using molecular dynamics simulations
被引:63
作者:
Krishna, R
[1
]
van Baten, JM
[1
]
机构:
[1] Univ Amsterdam, Vant Hoff Inst Mol Sci, NL-1018 WV Amsterdam, Netherlands
关键词:
D O I:
10.1021/ie051126d
中图分类号:
TQ [化学工业];
学科分类号:
0817 ;
摘要:
Adsorption and diffusion of pure components and binary mixtures containing methane, ethane, propane, n-butane, isobutane, and hydrogen at 300 K in a variety of configurations of carbon nanotubes (CNTs) have been investigated using configurational-bias Monte Carlo (CBMC) simulations and molecular dynamics (MD) simulations. Both self-diffusivities, D-i,D-self, and the Maxwell-Stefan (MS) diffusivities, D-i, were determined for a variety of molecular loadings Theta, approaching saturation limits. For comparison purposes, self-diffusivities were also determined in pure fluids of varying densities using MD. At low loadings Theta, the D-i,D-self correspond to the value for low-density gases. With increasing loadings, however, the D-i,D-self in CNTs are slightly higher than the values in fluids when compared at the same molecular density. In CNTs, the D-i,D-self is significantly smaller in magnitude than the MS diffusivity D-i, signifying strong correlations between molecular jumps along the tube. Consequently, for mixture diffusion, the component self-diffusivities are close to-ether. MD simulations of binary-mixture diffusion demonstrate that the mixture-diffusion characteristics can be estimated with good accuracy from the pure-component diffusion parameters using the MS diffusion formulation. In the estimation procedure, the binary-exchange parameter D-12 is estimated from the pure-component self-exchange coefficients D-11 and D-22 using the interpolation scheme Suggested earlier for transport in zeolites.
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页码:2084 / 2093
页数:10
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