Effect of potassium on the catalyzed reaction of n-hexane over Pt(111) single crystal surfaces

Journal Article · Thu Dec 01 04:00:00 EST 1983 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(83)90009-X· OSTI ID:6356290

Zaera, F; Somorjai, G A

The effect of potassium on the n-hexane conversion catalyzed by Pt(111) single crystals has been studied near atmospheric pressures. Reaction activity, selectivity, and self-poisoning with time were studied as a function of potassium coverage of the crystal faces. The activity of the catalyst dropped drastically with as little as 2% potassium atoms on the surface, with no improvement in selectivity or stability. The temperature dependence in the range 55-625 K of the reaction rates was not significantly different from the clean platinum case. The changes in the structure of the carbonaceous deposits formed during the reaction have also been studied. The amount of carbon on the surface after reactions was slightly higher on the platinum surface that was covered with 2% potassium atoms, as compared with the clean platinum case. The amount of bare platinum available for reaction, however, increase by a factor of 2 when theta/sub k/ = 0.3. When potassium was added to the platinum surface, the carbonaceous deposits showed a higher hydrogen content, with a higher activation energy for its desorption, an increase up to 4 kcal/mol more than for the clean platinum case. The inhibition of the dehydrogenation of adsorbed hydrocarbons species in the presence of coadsorbed potassium on the platinum surface explains the changes of reactivity that are reported. 10 figures, 2 tables.

• Research Organization: Univ. of California, Berkeley
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6356290
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 84:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ACTIVATION ENERGY
ADSORPTION
ALKALI METALS
ALKANES
AROMATICS
AUGER ELECTRON SPECTROSCOPY
BENZENE
CARBON
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL COATING
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHEMICAL VAPOR DEPOSITION
CHROMATOGRAPHY
COATINGS
CRYSTALS
CYCLOALKANES
CYCLOHEXANE
DATA
DEPOSITION
DESORPTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY
EXPERIMENTAL DATA
GAS CHROMATOGRAPHY
HEXANE
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROGENATION
INFORMATION
ISOMERIZATION
KINETICS
MASS SPECTRA
MEDIUM VACUUM
METALS
MONOCRYSTALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
POTASSIUM
PRESSURE DEPENDENCE
REACTION KINETICS
SAMPLE PREPARATION
SAMPLING
SEPARATION PROCESSES
SORPTION
SPECTRA
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
SURFACE COATING
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
TRANSITION ELEMENTS
ULTRAHIGH VACUUM
VAPOR DEPOSITED COATINGS
YIELDS