Thermal degradation of supported catalysts: coarsening kinetics of alloy platinum-palladium particles on oxide substrates. With appendix on palladium loss due to oxide volatilization
A systematic method for analysis of coarsening kinetics of small metal alloy particles supported on flat surfaces was developed and applied to data from coarsening experiments on 5.0 at. Vertical Bar3< platinum-palladium particles on alumina substrates. The initial average particle radii were about 5 nm, and the heat treatment was at 600/sup 0/-900/sup 0/C. The technique used for particle size measurements was based on a thin film sputtering and transmission electron microscopy. The results are described by interparticle transport of PtO/sub 2/ molecules for the platinum at all temperatures and for the palladium PdO molecules at 600/sup 0/ and 700/sup 0/C and palladium atoms at 800/sup 0/ and 900/sup 0/C. The dominant interparticle transport path was the substrate surface. The compositions remained nearly constant during coarsening. Transport of PdO was rate-controlling at 600/sup 0/C, and at each of the higher temperatures, transport by either platinum or palladium species gave the same coarsening rates. The dominant mode of coarsening after long heat treatment times was nucleation-inhibited, although the early time coarsening at 700/sup 0/ and 800/sup 0/C and all coarsening at 900/sup 0/ was noninhibited.
- OSTI ID:
- 6971653
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM OXIDES
CATALYTIC EFFECTS
CATALYST SUPPORTS
THERMAL DEGRADATION
CATALYSTS
PALLADIUM ALLOYS
REACTION KINETICS
PALLADIUM OXIDES
EVAPORATION
PLATINUM ALLOYS
HIGH TEMPERATURE
PARTICLE SIZE
PLATINUM OXIDES
SURFACE PROPERTIES
TEMPERATURE EFFECTS
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
KINETICS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM COMPOUNDS
PHASE TRANSFORMATIONS
PLATINUM COMPOUNDS
PLATINUM METAL ALLOYS
SIZE
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties