An approach to the surface barrier concept in diffusion in zeolites by computer simulation

The technique of molecular dynamics has been used to determine the trajectories of Ar and Xe atoms passing through the outer surface of aluminum-free MFI- and MOR-type crystals. In the case of Xe, the passage of the atom through the outer silicalite surface was observed to be significantly retarded,...

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Bibliographic Details
Published in:Journal of catalysis 1992, Vol.134 (2), p.536-541
Main Authors: Vigne´-Maeder, F., El Amrani, S., Ge´lin, P.
Format: Article
Language:English
Subjects:
400201 - Chemical & Physicochemical Properties
ARGON
Catalysis
Chemical Sciences
Chemistry
COMPUTERIZED SIMULATION
CRYSTAL STRUCTURE
DIFFUSION
ELEMENTS
Exact sciences and technology
FLUIDS
GASES
General and physical chemistry
INORGANIC ION EXCHANGERS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
ION EXCHANGE MATERIALS
MAGNETIC RESONANCE
MATERIALS
MATHEMATICAL MODELS
MICROSTRUCTURE
MINERALS
NONMETALS
NUCLEAR MAGNETIC RESONANCE
PERMEABILITY
POROSITY
RARE GASES
RESONANCE
SILICATE MINERALS
SIMULATION
Solid-gas interface
Surface physical chemistry
XENON
ZEOLITES
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Summary:The technique of molecular dynamics has been used to determine the trajectories of Ar and Xe atoms passing through the outer surface of aluminum-free MFI- and MOR-type crystals. In the case of Xe, the passage of the atom through the outer silicalite surface was observed to be significantly retarded, compared to Ar behaviour. In addition to the mass effect, this result was ascribed to a purely geometrical effect, the size of Xe and silicalite pores being comparable. Although this result qualitatively featured the behaviour of Xe in ZSM-5 measured by NMR, the model would certainly not explain the significant retardation in exchange rates observed on a macroscopic scale. A better simulation of the adsorption process, adsorbate-adsorbate interactions and energy exchange between adsorbate and surface crystal atoms taken into account, is required.
ISSN:0021-9517
1090-2694
DOI:10.1016/0021-9517(92)90340-N