Structure sensitivity of cyclohexane dehydrogenation and hydrogenolysis catalyzed by platinum single crystals at atmospheric pressure
The dehydrogenation and hydrogenolysis of cyclohexene catalyzed by platinum single-crystal surfaces has been investigated at total reactant pressures of 115 to 760 Torr and temperatures of 533 to 573 K. The flat (111), stepped (557), and kinked (25, 10, 7) and (10, 8, 7) surfaces used in this study were characterized in ultrahigh vacuum by low-energy electron diffraction and Auger electron spectroscopy, before and after reaction experiments. Benzene, cyclohexane, n-hexane, and alkane fragments with carbon number less than 6 were observed as reaction products. The rate of dehydrogenation to benzene on the four surfaces increased in the order (111) < (557) < (10, 8, 7) < (25, 10, 7). On the other hand, the hydrogenolysis rates and the rate of cyclohexene production were highest on the (111) surface. In general, the reaction rates decreased with increasing reaction time. The decrease of the dehydrogenation rates was due to reversible product inhibition by benzene, as well as the irreversible adsorption of tightly bound carbonaceous deposits. The hydrogenolysis rates did not exhibit product inhibition and decreased solely as the result of the irreversibly adsorbed carbonaceous species. The strength of inhibition by benzene increased in the order (25, 10, 7) < (10, 8, 7) < (557) < (111). These high-pressure results using single-crystal catalysts are compared to similar studies previously performed at pressures of less than 10/sup -5/ Torr. A comparison is also made to studies by others using dispersed platinum catalysts.
- Research Organization:
- Univ. of California, Berkeley
- OSTI ID:
- 6455405
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 67:2; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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The structure sensitivity of n-heptane dehydrocyclization and hydrogenolysis catalyzed by platinum single crystals at atmospheric pressure
Structure sensitivity of n-heptane dehydrocyclization and hydrogenolysis catalyzed by platinum single crystals at atmospheric pressure
Related Subjects
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALKANES
ALKENES
AROMATICS
BENZENE
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COHERENT SCATTERING
COMPARATIVE EVALUATIONS
CYCLOALKANES
CYCLOALKENES
CYCLOHEXANE
DECOMPOSITION
DEHYDROGENATION
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
HEXANE
HIGH TEMPERATURE
HIGH VACUUM
HYDROCARBONS
KINETICS
LOW PRESSURE
METALS
ORGANIC COMPOUNDS
PLATINUM
PLATINUM METALS
REACTION KINETICS
SCATTERING
SPECTROSCOPY
SURFACES
TRANSITION ELEMENTS