Reduction and cluster growth of palladium in zeolite Y containing transition metal ions. X-ray absorption studies
- Univ. of New Mexico, Albuquerque (USA)
The effect of a second transition metal on the reducibility and agglomeration behavior of palladium in zeolite Y is studied by EXAFS spectroscopy. Special attention is given to the potential bonding interactions between both metal constituents that could result in chemical anchoring of the noble metal to the support via the unreduced cocation. Zeolite Y was coexchanged with Fe{sup 2+} or Co{sup 3+} and Pd{sup 2+} and with each ion alone. Dehydration in oxygen atmosphere and reduction with hydrogen was performed at different temperatures up to 623 K. The structure of the samples during various stages of pretreatment and reduction was studied with EXAFS on both absorption edges. Palladium is partially reduced to Pd{sup 0} at room temperature and forms small metal clusters at higher temperatures. Iron is oxydized under oxygen atmosphere and is partially present in the form of iron oxide particles, which are redispersed under reducing conditions. A small enhancement of the reducibility of palladium is observed if iron is present in the zeolite, but neither a chemical anchoring nor an effect on the final agglomeration process of palladium is detected by the presence of iron cations. In contrast, coexchange with cobalt results in a substantially higher dispersion of the Pd(0) phase after high-temperature reduction. Apparently, the change in cation distribution induced by the Co ions influences the reduction process of palladium. When palladium ions are diffused into the zeolite containing aqueous Fe(II) ions, a Pd(0) phase consisting of larger crystallites is formed at room temperature by a redox reaction with Fe(II).
- DOE Contract Number:
- AS05-80ER10742
- OSTI ID:
- 6656590
- Journal Information:
- Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:2; ISSN 0022-3654; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structural Interconversion between Agglomerated Palladium Domains and Mononuclear Pd(II) Cations in Chabazite Zeolites
Related Subjects
360603* -- Materials-- Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
CHARGED PARTICLES
CLUSTER MODEL
COBALT IONS
DATA
DATA ANALYSIS
ELEMENTS
EXPERIMENTAL DATA
HIGH TEMPERATURE
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
IONS
IRON IONS
MATERIALS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
MINERALS
NUCLEAR MODELS
NUMERICAL DATA
PALLADIUM
PLATINUM METALS
SPECTROSCOPY
TRANSITION ELEMENTS
ZEOLITES