Interpreting Unary, Binary, and Ternary Mixture Permeation Across a SAPO-34 Membrane with Loading-Dependent Maxwell-Stefan Diffusivities
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- 作者：Shiguang Li ; John L. Falconer ; Richard D. Noble ; R. Krishna
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：April 5, 2007
- 年：2007
- 卷：111
- 期：13
- 页码：5075 - 5082
- 全文大小：915K
- 年卷期：v.111,no.13(April 5, 2007)
- ISSN：1932-7455
文摘
Unary permeation experiments were performed with He, H2, CO2, N2, O2, CO, Ar, and CH4 across a SAPO-34 membrane at 295 K with upstream pressures ranging to 7.2 MPa, ensuring that high occupancies withinthe zeolite layer are reached. Careful analysis of the unary permeation experiments shows that the Maxwell-Stefan (M-S) diffusivity 
i is loading-dependent for all gases except He and H2. The model of Reed andEhrlich (Surf. Sci. 1981, 102, 588-609) was used to describe the loading-dependence of i. The zero-loadingdiffusivity i(0) and the Reed-Ehrlich parameter 
i are backed out from the permeation experiments, providinga complete description of i as a function of loading, qi. Permeation experiments for CO2/CH4, CO2/N2,N2/CH4, H2/CH4, H2/N2, H2/CO, and CO2/CH4/N2 mixtures were performed to determine to what extent loading-dependent M-S diffusivities influence permeation fluxes and selectivities. Good agreement between the M-Smixture model and experiments are obtained, provided the binary exchange coefficients ij in the M-S uationsare assumed to have high enough values to ensure that intercage hops of the molecules occur practicallyindependently of one other.
i is loading-dependent for all gases except He and H2. The model of Reed andEhrlich (Surf. Sci. 1981, 102, 588-609) was used to describe the loading-dependence of i. The zero-loadingdiffusivity i(0) and the Reed-Ehrlich parameter i are backed out from the permeation experiments, providinga complete description of i as a function of loading, qi. Permeation experiments for CO2/CH4, CO2/N2,N2/CH4, H2/CH4, H2/N2, H2/CO, and CO2/CH4/N2 mixtures were performed to determine to what extent loading-dependent M-S diffusivities influence permeation fluxes and selectivities. Good agreement between the M-Smixture model and experiments are obtained, provided the binary exchange coefficients ij in the M-S uationsare assumed to have high enough values to ensure that intercage hops of the molecules occur practicallyindependently of one other.