Reactions of saturated hydrocarbons with hydrogen and deuterium on epitaxially oriented (111) Pd and Pd-Au alloy films
The reactions of neopentane, n-butane, propane, and n-pentane in the presence of an excess of hydrogen have been studied on evaporated Pd/Au-on-mica films. The characterization of films showed that they were predominantly (111) oriented. The selectivity in hydrogenolysis of all hydrocarbons decreased markedly with an increase in the content in Au. The catalytic activity for isomerization of neopentane and n-butane was higher for ca. 10 at. % Au alloys than for pure Pd. This finding appears to support the mechanism involving 1,2-bond shift isomerization at one metal site proposed by McKervey et al. Additional experiments with CH/sub 4//D/sub 2/ and neopentane/D/sub 2/ exchange over Pd-Au(111) alloys at higher temperatures showed considerable difficulties in forming carbene adspecies which could be responsible for another isomerization route. The isotopic exchange between cyclopentane and deuterium over (111) oriented Pd-Au alloys showed that the rate of multiple exchange goes through a gentle maximum for ca. 10 at. % Au. At the same time no special catalytic role of the surface sites of a low coordination number is seen. It is speculated that the rollover process may involve similar intermediate species as in alkene hydrogenation. The relative importance of ensemble size vs electronic effects in the Pd-Au alloys for various reactions is discussed.
- Research Organization:
- Inst. of Physical Chemisry, Warszawa, Poland
- OSTI ID:
- 6876588
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 77:1; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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ALKANES
ALLOYS
CARBENES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
DATA
DEUTERIUM
ELEMENTS
EXPERIMENTAL DATA
FILMS
GOLD ALLOYS
HYDROCARBONS
HYDROGEN
HYDROGEN ISOTOPES
HYDROGENATION
INFORMATION
ISOMERIZATION
ISOTOPES
ISOTOPIC EXCHANGE
LIGHT NUCLEI
METALS
MICA
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PALLADIUM
PALLADIUM ALLOYS
PLATINUM METAL ALLOYS
PLATINUM METALS
RADICALS
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENTS