Structure of Pt-Ir catalysts Moessbauer Spectroscopy studies employing /sup 57/Fe as a probe
Alumina-supported 1.75% iridium, 1.75% platinum, or 1.75% platinum/1.75% iridium catalyst were prepared by impregnation and 0.1% iron-57-enriched iron added in a second impregnation step. Hydrogen, carbon monoxide, and oxygen adsorption showed a dispersion near unity (i.e., nearly all metal atoms exposed) after calcination at 260/sup 0/C, and agglomeration and/or iridium oxide formation of the iridium and bimetallic catalysts after calcination at 600/sup 0/C. A careful evaluation of the Moessbauer spectra of these catalysts, of physically mixed iridium and platinum catalysts, and of bimetallic catalysts prepared by coimpregnation, at 25/sup 0/C and at 18/sup 0/-23.5/sup 0/K, at which temperature the samples became ferromagnetic and their spectra exhibited magnetic hyperfine splitting, provided evidence that the platinum/iridium catalysts consisted of bimetallic clusters in which virtually all metal atoms were surface atoms.
- Research Organization:
- Exxon Res. Eng. Co.
- OSTI ID:
- 6337217
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 62:1; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ADSORPTION
AGGLOMERATION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BIMETALS
CALCINATION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
DECOMPOSITION
DISPERSIONS
ELEMENTS
EVALUATION
FERROMAGNETIC MATERIALS
GAMMA SPECTROMETERS
HIGH TEMPERATURE
HYDROGEN
IMPREGNATION
IRIDIUM
IRIDIUM COMPOUNDS
IRIDIUM OXIDES
IRON
LOW TEMPERATURE
MAGNETIC MATERIALS
MAGNETIC PROPERTIES
MATERIALS
MEASURING INSTRUMENTS
MEDIUM TEMPERATURE
METALS
MIXTURES
MOESSBAUER SPECTROMETERS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM
PLATINUM METALS
PYROLYSIS
REFRACTORY METAL COMPOUNDS
SOLID CLUSTERS
SORPTION
SPECTRA
SPECTROMETERS
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
USES