Monte Carlo simulations of diffusion in zeolites and comparison with the generalized Maxwell-Stefan theory

Journal Article · Sat Aug 01 00:00:00 EDT 1992 · Journal of Catalysis; (United States)

OSTI ID:7241508

Nijhuis, S A; Krishna, R ^[1]

---

1. Univ. of Amsterdam (Netherlands)

Diffusion in zeolites is studied by means of Monte Carlo methods and the generalized Maxwell-Stefan theory of irreversible thermodynamics. The influence of the surface occupancy, the surface structure, and the surface chemical potential on one- and multicomponent surface diffusion has been investigated. Mass transfer has been simulated in one- and two-dimensional zeolitic channel structures. For the description of the sorption process two different models have been applied, a Langmuir model and a model with repulsive interactions between sorbed molecules. The one-component Fick diffusion coefficient, in the case of the Langmuir adsorption model, is found to be independent of the surface occupancy and depends weakly on the dimension of the lattice. Tracer diffusion on a one-dimensional lattice shows a linear dependence between the mean square displacement of labelled molecules and the square root of time. The mean square displacement in the case of tracer diffusion on the two-dimensional lattice follows the Einstein relation. The uptake behavior of binary mixtures, co- and counter-diffusion, on the two-dimensional lattice as obtained from the Monte Carlo simulations is in agreement with a single-file diffusion model. The single-file diffusion matrix can be considered as a limiting case of the generalized Maxwell-Stefan formulation. The results of the Monte Carlo simulations and the single-file diffusion model show that the zeolitic structure has an influence on mass transfer rates in tracer flow and counterdiffusion. The coupling between surface fluxes present in the case of the transient uptake of a multicomponent mixture is demonstrated.

• OSTI ID: 7241508
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 136:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
CRYSTAL STRUCTURE
DIFFUSION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MASS TRANSFER
MATERIALS
MATHEMATICAL MODELS
MICROSTRUCTURE
MINERALS
MONTE CARLO METHOD
ONE-DIMENSIONAL CALCULATIONS
PARTICLE MODELS
PERMEABILITY
POTENTIALS
SILICATE MINERALS
SIMULATION
SORPTION
SORPTIVE PROPERTIES
STATISTICAL MODELS
SURFACE POTENTIAL
SURFACE PROPERTIES
THERMODYNAMIC MODEL
TWO-DIMENSIONAL CALCULATIONS
ZEOLITES