Catalytic activity and deactivation mechanisms of supported NiO in CH/sub 4/ oxidation
The partial oxidation of CH/sub 4/ was studied using a commercial Ni/..cap alpha..-Al/sub 2/O/sub 3/ catalyst. The results show that two operating regimes can be maintained: a low-conversion regime where CO/sub 2/ and H/sub 2/O are formed and a high-conversion regime where CO, CO/sub 2/, H/sub 2/ and H/sub 2/O are formed. The latter regime is established by catalytic light-off which among other conditions depends on temperature, feed composition and catalyst activity. Prior to light-off, the catalyst is in the NiO form. Following light-off, the catalyst is in NiO form near the inlet and metallic form further downstream. A series of NiO/..cap alpha..-Al/sub 2/O/sub 3/ and NiO/ZrO/sub 2/ catalysts were prepared by impregnation and calcination in air between 750 and 1050/sup 0/C. These catalysts were characterized by the BET method, O/sub 2/ chemisorption, x-ray diffraction, electron microscopy and ESCA. Test analyses indicate that the supported NiO particles are made up of a large number of small crystallites which become more dispersed after reduction and reunite after oxidation. The activity of these catalysts for CH/sub 4/ oxidation under pre-light-off conditions was found to decrease dramatically with increasing calcination temperature. However, the calcined catalysts can be reactivated by reduction in H/sub 2/ prior to reaction. The change in activity is attributed mainly to the change in specific activity of NiO which is explained in terms of the change in excess oxygen content.
- OSTI ID:
- 5375151
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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10 SYNTHETIC FUELS
METHANE
OXIDATION
NICKEL OXIDES
CATALYTIC EFFECTS
PARTIAL OXIDATION PROCESSES
CATALYSTS
ALUMINIUM OXIDES
CARBON DIOXIDE
CARBON MONOXIDE
CATALYSIS
DEACTIVATION
HYDROGEN PRODUCTION
WATER
ZIRCONIUM OXIDES
ALKANES
ALUMINIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
HYDROCARBONS
HYDROGEN COMPOUNDS
NICKEL COMPOUNDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
080109* - Hydrogen- Production- Partial Oxidation Processes
090110 - Hydrocarbon Fuels- Properties- (1979-1989)