The hydrogenolysis of methylcyclopentane on platinum model catalysts: particle size effect due to a reaction occurring at the phase boundary metal-support
The hydrogenolysis of methylcyclopentane at 520 K on platinum model catalysts was studied and the mechanism of this reaction investigated. Catalysts of low metal dispersion (<0.15) were prepared by high-vacuum evaporation of platinum onto thin films of amorphous alumina. After annealing at 770 K in air and hydrogen treatment at 520 K the mean size of the Pt particles was about 10 nm as determined by electron microscopy. On these catalysts the reaction products are mainly 2-methylpentane and 3-methylpentane and only 9-14% n-hexane is formed, as is to be expected for large Pt particles. On top of these catalysts a thin layer of Al/sub 2/O/sub 3/ (0.3 nm mean thickness) was then deposited in order to reduce the surface area of platinum in relation to the phase boundary platinum/alumina. Thereafter a decrease of the catalytic activity, as well as a shift in the product distribution, was observed. The n-hexane content was significantly enhanced (up to 22%) and the ratio of the three products was comparable to that usually obtained with Pt catalysts of higher dispersion. This result supports a reaction model which consists of two parallel reactions (i) occurring on the platinum surface and producing mainly 2-methylpentane and 3-methylpentane and (ii) occurring on the phase boundary platinum/support and producing additional n-hexane.
- Research Organization:
- Univ. of Innsbruck, Austria
- OSTI ID:
- 5555502
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 80:2; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALKANES
ALKYL RADICALS
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ANNEALING
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CYCLOALKANES
ELECTRON MICROSCOPY
ELEMENTS
EVAPORATION
FILMS
HEAT TREATMENTS
HEXANE
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROGENATION
KINETICS
METALS
METHYL RADICALS
MICROSCOPY
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
PLATINUM
PLATINUM METALS
RADICALS
REACTION KINETICS
THIN FILMS
TRANSITION ELEMENTS