Effect of gold on hydrogenolysis, isomerization, and dehydrocyclization reactions on polycrystalline platinum and iridium foils

Journal Article · Mon Mar 01 04:00:00 EST 1976 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(76)90247-5· OSTI ID:7142525

Hagen, D I; Somorjai, G A

The effect of the addition of gold to polycrystalline platinum and iridium foil samples on the initial reaction rates for the hydrogenolysis of propane, isobutane and n-heptane, the isomerization of isobutane, and the dehydrocyclization of n-heptane to toluene has been studied. Mass spectroscopy was used to monitor the reactions in a temperature range of 100 to 500/sup 0/C. The rates of hydrogenolysis and isomerization on the pure platinum and iridium surfaces were found to be within a factor of 5 of the corresponding rates measured by others at higher pressures (48 Torr--1 atm), suggesting that the hydrogen to hydrocarbon ratio is more important to the rates than absolute pressure. Platinum was found in general to be more active for hydrogenolysis and isomerization while iridium was the more active for dehydrocyclization. Time-dependent poisoning of the rates, the existence of a rate maximum as a function of temperature, and the predominance of low molecular weight hydrogenolysis products are attributed to the lower hydrogen pressures used in this work. The addition of gold to the platinum and iridium surface decreases the rates for all reactions studied. The data suggest that different surface sites are responsible for isomerization than for hydrogenolysis and dehydrocyclization.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 7142525
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 41:3; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

090110 -- Hydrocarbon Fuels-- Properties-- (1979-1989)
10 SYNTHETIC FUELS
2-METHYLPROPANE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALKANES
BUTANE
CATALYTIC EFFECTS
CHEMICAL REACTIONS
ELEMENTS
GOLD
HEPTANE
HYDROCARBONS
IRIDIUM
ISOMERIZATION
MASS SPECTROSCOPY
METALS
ORGANIC COMPOUNDS
PLATINUM
PLATINUM METALS
PROPANE
REFRACTORY METALS
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS