Molecular Transport in a Two-Dimensional Lattice of Sorption Sites

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Title:Molecular Transport in a Two-Dimensional Lattice of Sorption Sites
Creators:
Kočiřík, Milan
Zikánová, Arlette
Dubský, Josef
Kroček, Petr
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 59, 5, pp. 1001-1017

Abstract

<p>It is known from experimental study of the sorption of some aromatic compounds (such as <i>p</i>-xylene) in zeolites with the MFI lattice that the adsorption kinetics in such systems exhibits appreciable deviations from the 2<sup>nd</sup> Fick law. To account for those deviations, whose origin lies in the crystal bulk, the existence of two phases which are not in local chemical equilibrium is postulated: a mobile phase is assumed to occur in the straight zeolite channels whereas an immobile phase is assumed in the zig-zag channels. A microkinetic model is proposed assuming localization of the sorbed molecules on two kinds of centres arranged in a regular two-dimensional lattice, along which migration takes place in agreement with the Langmuir kinetics of exchange of molecules between the occupied and unoccupied centres. For an exact description of the time evolution of the considered physical system the model results in a set of ordinary differential equations which are transformed into a system of two partial differential equations providing a spatially continuous description of the physical system. This approach enables the phenomenological kinetic parameters to be interpreted in terms of the jump frequency of molecules between the various kinds of adsorption centres. For small perturbations in the concentration of the sorbing substance the mathematical model is linearized, and the behaviour of the system is illustrated using the numerical solution of the model equations. In dependence on changes in the model parameters, the transition from the case of pure diffusion along a one-dimensional lattice in the mobile phase, with the zig-zag channels inaccessible, via the case of a slowly establishing local equilibrium between the two sub-lattices, to the limiting case of instantaneously establishing local equilibrium between the sub-lattices is discussed.

Title:Molecular Transport in a Two-Dimensional Lattice of Sorption Sites
Creators:
Kočiřík, Milan
Zikánová, Arlette
Dubský, Josef
Kroček, Petr
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:59
Number:5
Page Range:pp. 1001-1017
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19941001UNSPECIFIED
ID Code:518
Item Type:Article
Deposited On:06 Feb 2009 17:01
Last Modified:06 Feb 2009 16:01

Citation

Kočiřík, Milan; Zikánová, Arlette; Dubský, Josef; Kroček, Petr (1994) Molecular Transport in a Two-Dimensional Lattice of Sorption Sites. Collection of Czechoslovak Chemical Communications, 59 (5). pp. 1001-1017. ISSN 0010-0765

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