XPS and TPR study of the reduction of promoted cobalt-Kieselguhr Fischer-Tropsch catalysts
Reduction of unpromoted Co- and promoted Co-ThO/sub 2/-MgO-Kieselguhr catalysts has been studied with X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. A mechanism of reduction is proposed based on spectroscopic measurements of the surface phases before and after H/sub 2/ treatment at 400/sup 0/C. Cobalt oxide Co/sub 3/O/sub 4/ is present on all air-calcined catalysts, and is reduced rapidly to CoO at temperatures > 300/sup 0/C in hydrogen. CoO is then more slowly reduced to Co metal on the unpromoted catalysts at 400/sup 0/C. If the promoters MgO and ThO/sub 2/ are present, a reaction between CoO and promoter can occur resulting in new phases which are more resistant to reduction than CoO alone. XPS results suggest one phase as a CoO-MgO solid solution, but the CoO-ThO/sub 2/ phase could not be identified. The cobalt in magnesia-promoted CoO phases is reduced completely to the metal at much higher temperatures (500-700/sup 0/C) but at 400/sup 0/C the surface reduction is limited to 55% +/- 5 after 1 h. Variability in the degree of reduction of various promoted cobalt catalysts is therefore dependent on the nature and loading of the promoter, and the reduction temperature. Promotion of a Co-Kieselguhr catalyst with ThO/sub 2/ or MgO does allow a higher degree of control over the CoO reduction kinetics than is found with unpromoted catalysts.
- Research Organization:
- Univ. of Melbourne, Parkville (Australia)
- OSTI ID:
- 5205885
- Journal Information:
- J. Catal.; (United States), Vol. 97:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CATALYSTS
REDUCTION
COBALT OXIDES
FISCHER-TROPSCH SYNTHESIS
CARBON MONOXIDE
MAGNESIUM OXIDES
METHANATION
PHOTOELECTRON SPECTROSCOPY
PROMOTERS
REACTION INTERMEDIATES
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
THORIUM OXIDES
X-RAY SPECTROSCOPY
ACTINIDE COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COBALT COMPOUNDS
ELECTRON SPECTROSCOPY
MAGNESIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SPECTROSCOPY
THORIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
010408* - Coal
Lignite
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