Characterization of supported cobalt and cobalt-rhodium catalysts. III. Temperature-programmed reduction, oxidation, and EXAFS of Co-Rh/SiO/sub 2/
Temperature-Programmed Reduction, Oxidation, and Extended X-Ray Absorption Fine Structure (TPR, TPO, and EXAFS) experiments supply clear evidence for the formation of bimetallic particles in Co-Rh/SiO/sub 2/ catalysts. After coimpregnation and drying, as well as after oxidation, the reduction of Co-Rh/SiO/sub 2/ catalysts proceeds at lower temperatures than the reduction of comparable Co/SiO/sub 2/ catalysts, indicating that rhodium catalyzes the reduction of the cobalt metal salt and cobalt oxide. EXAFS of the Rh K-edge of the Co-Rh/SiO/sub 2/ catalyst shows that after reduction the rhodium atoms in the catalyst have less cobalt neighbors than those in the Co-Rh alloy. The Rh-Co and Rh-Rh peak intensities in the Fourier transform of the Rh EXAFS were only slightly influenced by adsorption of oxygen at room temperature, whereas the EXAFS spectrum of the cobalt K-edge changed completely to that of cobalt oxide. From these results it is concluded that the reduced catalyst contains bimetallic Co-Rh particles, the interior of which are enriched in rhodium, while the outer layers contain more cobalt.
- Research Organization:
- Eindhoven Univ. of Technology (Netherlands)
- OSTI ID:
- 5353288
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 97:1; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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400201* -- Chemical & Physicochemical Properties
BIMETALS
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PROPERTIES
CHEMICAL REACTIONS
COBALT
COBALT COMPOUNDS
COBALT OXIDES
CRYSTAL STRUCTURE
ELEMENTS
FISCHER-TROPSCH SYNTHESIS
FOURIER TRANSFORMATION
INTEGRAL TRANSFORMATIONS
METALS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REDUCTION
REFRACTORY METAL COMPOUNDS
RHODIUM
RHODIUM COMPOUNDS
RHODIUM OXIDES
SILICON COMPOUNDS
SILICON OXIDES
SPECTROSCOPY
SURFACE PROPERTIES
TRANSFORMATIONS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY