Structure sensitivity of n-heptane dehydrocyclization and hydrogenolysis catalyzed by platinum single crystals at atmospheric pressure

Journal Article · Wed Jul 01 00:00:00 EDT 1981 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(81)90324-9· OSTI ID:6360477

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

The dehydrocyclization and hydrogenolysis of n-heptane catalyzed by platinum single-crystal surfaces have been investigated at temperatures from 533 to 603 K in the range of 1 atm total pressure. The flat (111), stepped (557), and kinked (10, 8, 7) and (25, 10, 7) surfaces used in this study were characterized under ultrahigh vacuum by low-energy electron diffraction and Auger electron spectroscopy before and after reaction experiments. The initial rate of dehydrocyclization to toluene on the four surfaces increased in the selectivity of toluene production versus hydrogenolysis increased by an order of magnitude in the order (111) approx. = (25, 10, 7) < (557) approx. = (10, 8, 7). Hydrogenolysis, however, increased in the order (557) < (10, 8, 7) < (25,10,7). As a result, the selectivity of toluene production versus hydrogenslysis increased by an order of magnitude in the orders (25, 10, 7) < (111) < (10, 8, 7) < (557). The sum of the rates of hydrogenolysis and toluene production remains relatively constant. The effect of preoxidation of the single-crystal catalysts was to increase the rate of hydrogenolysis and decrease the rate of dehydrocyclization. In general, the reaction rates decreased with increasing reaction time. This decrease was shown to be the result of the deposition of irreversibly adsorbed carbonaceous species.

• Research Organization: Univ. of California, Berkeley
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6360477
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 70:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

090121* -- Hydrocarbon Fuels-- Chemical Synthesis-- (1976-1989)
10 SYNTHETIC FUELS
ALKANES
AROMATICS
ATMOSPHERIC PRESSURE
AUGER ELECTRON SPECTROSCOPY
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTALS
CYCLOALKANES
CYCLOHEXANE
DEHYDROGENATION
DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
HEPTANE
HIGH TEMPERATURE
HYDROCARBONS
KINETICS
METALS
ORGANIC COMPOUNDS
PLATINUM
PLATINUM METALS
REACTION KINETICS
SCATTERING
SPECTROSCOPY
SURFACES
SYNTHESIS
TOLUENE
TRANSITION ELEMENTS
X-RAY DIFFRACTION