Distribution of metal and adsorbed guest species in zeolites
Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6783704
- Report Number(s):
- LBL-28545; ON: DE90013871
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
AROMATICS
BENZENE
CALCINATION
CATALYSTS
CHEMICAL REACTIONS
CHEMICAL SHIFT
DECOMPOSITION
ELECTRON MICROSCOPY
ELEMENTS
FLUIDS
GASES
HYDROCARBONS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
METALS
MICROSCOPY
MINERALS
NMR SPECTRA
NONMETALS
ORGANIC COMPOUNDS
PLATINUM
PLATINUM METALS
POWDERS
PYROLYSIS
RARE GASES
REDUCTION
SAMPLE PREPARATION
SODIUM COMPOUNDS
SORPTIVE PROPERTIES
SPECTRA
SURFACE PROPERTIES
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY
XENON
YTTRIUM COMPOUNDS
ZEOLITES