Effects of metal-support interactions on the chemisorption of H/sub 2/ and CO on Pd/SiO/sub 2/ and Pd/La/sub 2/O/sub 3/

Journal Article · Mon Oct 01 00:00:00 EDT 1984 · J. Catal.; (United States)

OSTI ID:6462663

Hicks, R F; Yen, Q J; Bell, A T

The adsorption of H/sub 2/ and CO was investigated on SiO/sub 2//sup -/ and La/sub 2/O/sub 3/-supported Pd catalysts, and the structure of adsorbed CO was characterized by ir spectroscopy. For each of the Pd/SiO/sub 2/ catalysts, the ratio of adsorbed H atoms, or adsorbed CO, to surface Pd atoms is unity. The stoichiometry for atomic adsorption stoichiometry for CO decreases linearly from 0.6 to 0 as the Pd dispersion decreased from 30 to 8%. The suppression of CO adsorption is attributed to patches of partially reduced support material, LaO/sub x/, transferred to the surface of the Pd crystallites during catalyst preparation. The fraction of the Pd crystallite surface covered by LaO/sub x/ increases with Pd dispersion, in agreement with conclusions based on earlier x-ray photoelectron spectroscopy studies. Ir studies indicate that the structures of CO adsorbed on Pd/La/sub 2/O/sub 3/ and Pd/SiO/sub 2/ are similar, but that the strength of adsorption is weaker for Pd/La/sub 2/O/sub 3/ than for Pd/SiO/sub 2/. This is attributed to a weakening in the sigma-bond component of the Pd-CO bond due to charge transfer from the LaO/sub x/ patches to the Pd crystallites. The absence of any suppression of H/sub 2/ adsorption of Pd/La/sub 2/O/sub 3/ indicates that H/sub 2/ adsorption occurs both on the exposed Pd surface atoms as well as on the LaO/sub x/ patches covering the balance of the surface Pd atoms. 53 references, 11 figures, 2 tables.

• Research Organization: Univ. of California, Berkeley
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6462663
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 89:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

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CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
COMPARATIVE EVALUATIONS
CORRELATIONS
DATA
ELEMENTS
EXPERIMENTAL DATA
HYDROGEN
INFORMATION
INFRARED SPECTRA
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
METALS
MINERALS
NONMETALS
NUMERICAL DATA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
QUANTITY RATIO
RARE EARTH COMPOUNDS
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SORPTIVE PROPERTIES
SPECTRA
STOICHIOMETRY
STRUCTURAL CHEMICAL ANALYSIS
SURFACE PROPERTIES
TRANSITION ELEMENTS