{sup 129}Xe NMR study of molecular diffusion within zeolites
Conference
·
OSTI ID:370738
- Universite P. et M. Curie, Paris (France); and others
The application of zeolites as catalysts and molecular sieves may depend decisively on their transport properties. It is the interplay between the transport resistance associated with the individual crystallites (surface barriers and intracrystalline transport resistance) and the bed resistance which determines the overall transport behaviour. The {sup 129}Xe NMR spectrum of adsorbed xenon used as a probe reflects the distribution of the concentrations of coadsorbed species within a sample. We have used this technique to study the rate of adsorption of benzene (or n-hexane) from the gas phase on ZSM-5 zeolites, as well as the rate of combined of adsorption and desorption in a bed consisting of initially loaded and unloaded crystallites. In the land case, when the two types of crystallites are intimately mixed, the limiting rate is the intracrystalline diffusion. A simple modelisation of the evolution of the spectra during the adsorption/desorption process allows us to determine an intracrystalline diffusion coefficient of the coadsorbed molecule. On the contrary, when the two types of crystallites make two separated layers, one can observe the diffusion through the bed.
- OSTI ID:
- 370738
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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