Chemisorption and catalysis by metal clusters. II. Chemisorption of carbon monoxide and of oxygen by supported osmium clusters derived from Os/sub 3/(CO)/sub 12/ and from Os/sub 6/(CO)/sub 18/

Journal Article · Sun Apr 01 04:00:00 EST 1984 · J. Catal.; (United States)

OSTI ID:7076490

Hunt, D J; Jackson, S D; Moyes, R B; Wells, P B; Whyman, R

Carbon monoxide and oxygen have been chemisorbed at 293 K on the high-nuclearity carbonyl-protected clusters (the various species A) obtained by heating in vacuo to 523 K Os/sub 3/(CO)/sub 12/ or Os/sub 6/(CO)/sub 18/ impregnated on silica, alumina, or titania. The adsorption isotherms have a conventional appearance, but most are composed of a primary and a secondary region. Material adsorbed in the secondary region is removed by evacuation at room temperature whereas that adsorbed in the primary region is removed by evacuation at elevated temperatures. For species A/alumina and the species A/titania the primary region is complete and the secondary region commences when the pressure over the adsorbent is 0.2 Torr. Species A/silica gave no secondary region in oxygen adsorption. Adsorption and subsequent temperature-programmed desorption of (/sup 18/O)CO occurred without any dilution by (/sup 16/O)CO, indicating that ligand-(/sup 16/O)CO and adsorbed-(/sup 18/O)CO do not exchange even at elevated temperatures. The two species A/aluminas catalyzed oxygen isotope exchange at 293 K. From the experimental evidence it is deduced that carbon monoxide and oxygen each adsorbs molecularly in both the primary and the secondary regions. In the primary region carbon monoxide adsorption occurs at osmium sites on the cluster framework, whereas in the secondary region it occurs at ligand-carbon bonded to osmium. For oxygen, adsorption in the primary region is again at osmium sites on the cluster framework but that in the secondary region is at osmium sites of the cluster framework suitably modified as a result of the support-cluster interaction.

• Research Organization: Univ. of Hull, England
• OSTI ID: 7076490
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 86:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

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10 SYNTHETIC FUELS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
ELEMENTS
MEDIUM TEMPERATURE
METALS
MOLECULAR STRUCTURE
NONMETALS
OSMIUM
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PLATINUM METALS
SEPARATION PROCESSES
SORPTION
TRANSITION ELEMENTS