Variation of catalytic activity over PtRe/. gamma. -Al/sub 2/O/sub 3/
Hydrogen isotope exchange (at 100/sup 0/C) and hydrogenolysis (at 240/sup 0/C) were studied over ..gamma..-Al/sub 2/O/sub 3/-supported Pt, Re, and a series of PtRe catalysts, where the composition and pretreatment conditions were varied. Sites catalyzing the rate-limiting step of the former reaction appear to be monoatomic, while those for the latter reaction are multiatomic. Alloys behave as physical mixtures for the isotope-exchange reaction, since the strength of the adsorption bond depends little on the atomic environment of the site. For hydrogenolysis, however, the PtRe catalysts behave differently than the Pt or Re monometallic catalysts. This is attributed to the formation of ensembles of atoms that contain both Pt and Re on the bimetallic catalyst and thus exhibit a heat of adsorption which is intermediate between the two. The most ensemble-specific reaction is total hydrogenolysis to methane. This rate is highest for sites on which adsorption is stronger than on Pt but weaker than on Re. This reaction, therefore, probes the extent of alloying on the supported particles.
- Research Organization:
- Northwestern Univ., Evanston, IL
- OSTI ID:
- 5851978
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 91:23; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
ADSORPTION HEAT
ALKANES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DEUTERIUM
ELEMENTS
ENTHALPY
EXPERIMENTAL DATA
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
MEDIUM TEMPERATURE
METALS
METHANE
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM
PLATINUM METALS
REACTION KINETICS
RHENIUM
STABLE ISOTOPES
SYNTHESIS
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
TRANSITION ELEMENTS