Experimental verification of the Maxwell-Stefan theory for micropore diffusion

Abstract

Experimental verification of the Maxwell-Stefan theory for micropore diffusion van den Broeke, L.J.P.; Krishna, R. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract--The main objective of this paper is to test the capability of the Maxwell-Stefan theory for predicting the diffusion behaviour of multicomponent mixtures within micropores on the basis of the diffusion behaviour of single components. Diffusion within micropores involves movement of sorbed species. It is an activated process. The proper driving force is the gradient of the surface chemical potential.In the Maxwell-Stefan theory for mieropore diffusion, the adsorption sites on the surface are viewed as pseudo-species, analogous to craters on the surface of the moon. The surface coverage has a significant influence on the mass transfer fluxes. The Maxwell-Stefan theory yields alternative approaches to micropore diffusion as special cases and is consistent with the theory of irreversible thermodynamics. The Maxwell-Stefan diffusivity for signal-component diffusion D is usually referred to as the "corrected" diffusivity in the literature. For binary diffusion, the Maxwell-Stefan equations, when combined with Langmuir adsorption equilibrium, coincide with the formulation derived by Habgood in 1958.To test the predictive capability of the Maxwell-Stefan theory we performed breakthrough experiments with single components and mixtures containing methane, carbon dioxide, propane and propene. These experiments were carried out in a packed bed of microporous activated carbon and with carbon molecular sieves. It is deafly demonstrated that the mixture behaviour can be predicted by the Maxwell-Stefan theory extremely well under a wide range of conditions: co-adsorption, co-desorption and counter-sorption. A model in which the matrix of Fick diffusivities is assumed to be constant is shown to be less successful in this regard.

Zeolite membranes – a review and comparison with MOFs

“…[170][171][172] The key to success for the Maxwell-Stefan model is the accurate determination of multicomponent adsorption and diffusion characteristics of the permeating species. Though these equations have provided a deep insight into the permeation through zeolite membranes, there are cases for which the Maxwell-Stefan model fails to interpret the experimental results.…”

Low-temperature anisotropic diffusion of helium in zircon: Implications for zircon (U–Th)/He thermochronometry

“…The quantity w [001] is a one-way jump frequency; therefore, the ''total jump frequency'' (i.e., diffusing atom jumps to any available adjacent site along the c-axis) becomes (Van den Broeke and Krishna, 1995):…”

Transient permeation of butanes through ZSM‐5 and ZSM‐11 zeolite membranes

“…The MaxwellStefan diffusion model, accounting for the interactions between diffusing molecules and their interactions with the zeolite surface, has been shown to quantitatively describe steady-state and transient diffusion in zeolites and zeolite membranes (Bakker et al, 1996;Burggraaf, 1999;Gardner et al, 2002a;Kapteijn et al, 1995bKapteijn et al, , 2000Krishna and van den Broeke, 1995;van den Broeke, 1994). The thermodynamic correction factor used in the Maxwell-Stefan diffusion model is calculated from the adsorption model.…”