Thermal evolution of the support promoter effect in Rh/La sub 2 O sub 3

Journal Article · Thu Jan 31 23:00:00 EST 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90194-9· OSTI ID:5716650

Gallaher, G; Goodwin, Jr, J G; Huang, C S; Houalla, M ^[1]

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1. Univ. of Pittsburgh, PA (USA)

Suppression of CO chemisorption and the rates of ethane hydrogenolysis and cyclopropane hydrogenation along with a {minus} 1-eV shift in the Rh 3d{sub 5/2} binding energy were observed for a 200{degree}C-reduced Rh/La{sub 2}O{sub 3} catalyst compared to Rh/SiO{sub 2}. These results are consistent with the decoration model proposed for the metal-support interaction between La{sub 2}O{sub 3} and noble metals, where the decoration species play the role of a promoter. The presence of these effects after such a mild pretreatment suggests that dissolution of the support by acidic precursor solutions during impregnation/drying and/or migration of support species during the early stages of reduction are probably the primary causes of the decoration. The extent of decoration appeared to be increased upon reduction of the La{sub 2}O{sub 3}-supported catalyst at 400{degree}C as evidenced by a further suppression of CO chemisorption and cyclopropane hydrogenation rate. H{sub 2} uptake, which greatly exceeded CO uptake after the 200{degree}C reduction suggesting spillover of H{sub 2} to decorating species and/or the support, increased further after a 400{degree}C reduction indicating an increased capacity of the decorating species and support for spillover H{sub 2}. This thermal modification of the decorative overlayer occurs concurrent with the dehydration of La(OH){sub 3} to La OOH and La{sub 2}O{sub 3} and the Rh-catalyzed decomposition of La{sub 2}(CO{sub 3}){sub 3}, those compounds which constitute the support after impregnation and/or exposure to air.

• OSTI ID: 5716650
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 127:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ADSORPTION
ALKANES
ALKENES
BINDING ENERGY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
COMPARATIVE EVALUATIONS
CONFIGURATION INTERACTION
CYCLOALKANES
DECOMPOSITION
DEHYDRATION
DEHYDROGENATION
DISSOLUTION
ELEMENTS
ENERGY
ETHANE
ETHYLENE
HYDROCARBONS
HYDROGEN
HYDROGENATION
IMPREGNATION
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
METALS
METHANATION
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
PROMOTERS
RARE EARTH COMPOUNDS
REDUCTION
RHODIUM
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SURFACE PROPERTIES
TRANSITION ELEMENTS