Hydrogen adsorption behavior and strong metal-support interaction (SMSI) on Rh-Pt bimetallic catalysts

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:7183190

Huang, H

Chemisorption and catalytic activity studies have been used to probe the surface structure and the nature of metal-support interaction on rhodium-platinum bimetallic catalysts which were supported on two types of silica, and on alumina and titania. All of the results suggest that Rh is enriched relative to Pt on the surface of the bimetallic particles. The extent of Rh enrichment strongly depends on the surface properties of the supports. The hydrogen chemisorption equilibrium constant is found to be very much larger on Pt than on Rh. Using the observed equilibrium constant and the known slow desorption kinetics of H/sub 2/ from Pt, one can rationalize the relative rates of hydrogenolysis on Rh and Pt and the bimetallic catalysts as well as the observed apparent activation energies and their sensitivity to the kind of reactor (pulse or flow) used. Pulse-mode CO hydrogenation experiments demonstrate an effect of strong metal-support interaction in CO + H/sub 2/ reaction as well as in hydrocarbon hydrogenolysis on titania supported Rh-Pt bimetallic catalysts. The experiments support the surface migration model where a reduced TiO/sub x/ species moves onto the active metal surface. Hydrogen-oxygen titration experiments indicated that this species has the stoichiometry of TiO on Rh/TiO/sub 2/ catalyst and Ti/sub 2/O on Pt/TiO/sub 2/. These same experiments over the bimetallic catalysts indicate that SMSI does not affect the surface segregation situation, i.e., the surfaces of Rh-Pt/TiO/sub 2/ catalysts are enriched in Rh to a similar extent to that observed on other supports.

• Research Organization: Yale Univ., New Haven, CT (USA)
• OSTI ID: 7183190
• Country of Publication: United States
• Language: English

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BIMETALS
CARBON COMPOUNDS
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