Structure sensitivity of cyclohexane dehydrogenation and hydrogenolysis catalyzed by platinum single crystals at atmospheric pressure

Journal Article · Sun Feb 01 00:00:00 EST 1981 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(81)90297-9· OSTI ID:6455405

Herz, R K; Gillespie, W D; Petersen, E E; Somorjai, G A

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, CA (United States)
• OSTI ID: 6455405
• Journal Information: J. Catal.; (United States), Vol. 67:2
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CYCLOHEXANE
DEHYDROGENATION
PLATINUM
CATALYTIC EFFECTS
DECOMPOSITION
ALKANES
BENZENE
CHEMICAL REACTION KINETICS
COMPARATIVE EVALUATIONS
CYCLOALKENES
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
HEXANE
HIGH TEMPERATURE
HIGH VACUUM
LOW PRESSURE
SURFACES
ALKENES
AROMATICS
CHEMICAL REACTIONS
COHERENT SCATTERING
CYCLOALKANES
DIFFRACTION
ELEMENTS
HYDROCARBONS
KINETICS
METALS
ORGANIC COMPOUNDS
PLATINUM METALS
REACTION KINETICS
SCATTERING
SPECTROSCOPY
TRANSITION ELEMENTS
400301* - Organic Chemistry- Chemical &amp; Physicochemical Properties- (-1987)