Effect of oxygen on hydrocarbon catalysis by platinum crystal surfaces at high and low pressure
- Univ. Calif., Lawrence Berkeley Lab.
The reactions of cyclohexane with hydrogen were tested at 100-500 mm Hg and 573/sup 0/K or < 0.00001 mm Hg and 423/sup 0/K on platinum single crystal surfaces of a close-packed hexagonal array (111), a stepped surface containing 17% low-coordination number atoms (557), a surface with step sites and 6% kink sites (10,8,7), and a stepped surface with 9% kink sites (25,10,7). Dehydrogenation of cyclohexane to benzene increased with increasing coordinative unsaturation and deactivation occurred owing to benzene adsorption and coke deposition; catalysts with kink sites deactivated more slowly than the (111) surface, probably due to higher energy hydrogen binding states. The difference between flat and kinked surface activities was greater at high than at lower pressure. Ring opening and fragmentation reaction rates were higher on (111) surfaces than on stepped or kinked surfaces. Preoxidation of the catalysts enhanced the hydrogenation and dehydrogenation reactions; the effect was structure sensitive and greatest on the (10,8,7) surface.
- OSTI ID:
- 6138938
- Report Number(s):
- CONF-791108-
- Journal Information:
- 72nd AIChE Annu. Meet. Prepr.; (United States), Journal Name: 72nd AIChE Annu. Meet. Prepr.; (United States) Vol. 59C
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201 -- Chemical & Physicochemical Properties
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ADSORPTION
ALKANES
AROMATICS
BENZENE
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COKE
CRYSTAL STRUCTURE
CYCLOALKANES
CYCLOHEXANE
DEACTIVATION
DEHYDROGENATION
DEPOSITION
ELEMENTS
HIGH TEMPERATURE
HIGH VACUUM
HYDROCARBONS
HYDROGENATION
KINETICS
LOW PRESSURE
METALS
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXYGEN
PLATINUM
PLATINUM METALS
REACTION KINETICS
SORPTION
SURFACES
TESTING
TRANSITION ELEMENTS