Study of Cu/sup 2 +/ location in zeolites Na-A and K-A by electron spin resonance and electron spin spectroscopies
Electron spin resonance (ESR) and electron spin echo (ESE) spectroscopies are used to determine the cation site location of Cu/sup 2 +/ in hydrated and dehydrated forms of Cu/sup 2 +/-doped zeolites Na-A and K-A. This is achieved by partial exchange of the Na-A and K-A zeolites by Cs/sup +/ cations which reside in well-defined crystallographic sites. Monitoring the weak hyperfine interaction between the Cu/sup 2 +/ and Cs/sup +/ cations using ESE makes it possible to determine the cation siting of Cu/sup 2 +/ relative to the matrix of Cs/sup +/ cations. At low Cu/sup 2 +/ loadings the Cu/sup 2 +/ favor sites on the threefold axis close to a zeolite six-ring. The larger the number of water molecules coordinated to the Cu/sup 2 +/ the more the displacement of the Cu/sup 2 +/ from the center of the six-ring face - except in the case of a trigonal-bipyramidal Cu/sup 2 +/ complex coordinated to one water molecule in the ..cap alpha..-case, one in ..beta..-cage, and three equatorial lattice oxygens which is located in site S2. An octahedrally coordinated Cu/sup 2 +/ complex in both zeolites, Na-A and K-A, coordinated to three H/sub 2/O molecules is displaced 0.09 nm into the ..beta..-cage while a tetrahedrally coordinated Cu/sup 2 +/ complex bound to only one water molecule in K-A is displaced 0.02 nm into the ..beta..-cage. After complete dehydration the Cu/sup 2/ moves almost into the plane of the six-ring to give the strongest possible cation-zeolite interaction with a Cu/sup 2 +/-O/sub z/ bond length of 0.23 nm (O/sub z/ = zeolite oxygen).
- Research Organization:
- Univ. of Houston, TX
- OSTI ID:
- 6631097
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 91:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CESIUM COMPOUNDS
CRYSTAL STRUCTURE
VACANCIES
COPPER COMPOUNDS
POTASSIUM COMPOUNDS
SODIUM COMPOUNDS
ACOUSTIC ESR
CATIONS
ELECTRON SPIN RESONANCE
EXPERIMENTAL DATA
HYPERFINE STRUCTURE
IMPURITIES
ZEOLITES
ALKALI METAL COMPOUNDS
CHARGED PARTICLES
CRYSTAL DEFECTS
DATA
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
IONS
MAGNETIC RESONANCE
MATERIALS
MINERALS
NUMERICAL DATA
POINT DEFECTS
RESONANCE
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties