Interpreting unary, binary and ternary mixture permeation across a SAPO-34 membrane with loading-dependent Maxwell-Stefan diffusivities

Li, Shiguang ; Falconer, John L. ; Noble, Richard D. ; Krishna, R. (2007) Interpreting unary, binary and ternary mixture permeation across a SAPO-34 membrane with loading-dependent Maxwell-Stefan diffusivities The Journal of Physical Chemistry C, 111 (13). pp. 5075-5082. ISSN 0022-3654

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp067404j

Related URL: http://dx.doi.org/10.1021/jp067404j

Abstract

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 within the zeolite layer are reached. Careful analysis of the unary permeation experiments shows that the Maxwell-Stefan (M-S) diffusivity Ði is loading-dependent for all gases except He and H2. The model of Reed and Ehrlich (Surf. Sci. 1981, 102, 588-609) was used to describe the loading-dependence of Ði. The zero-loading diffusivity Ði(0) and the Reed-Ehrlich parameter φ i are backed out from the permeation experiments, providing a complete description of Ði 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-S mixture model and experiments are obtained, provided the binary exchange coefficients Ðij in the M-S uations are assumed to have high enough values to ensure that intercage hops of the molecules occur practically independently of one other.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:65350
Deposited On:17 Oct 2011 03:26
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