Rhodium supported on faujasites: Effects of cluster size and CO ligands on catalytic activity for toluene hydrogenation

Journal Article · Thu Dec 10 04:00:00 EST 1998 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1998.2264· OSTI ID:316311

Weber, W A; Gates, B C ^[1]

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1. Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

NaY zeolite-supported rhodium carbonyls, with the predominant species being [Rh{sub 6}(CO){sub 16}], were prepared by carbonylation of adsorbed [Rh(CO){sub 2}(acac)] at 125 C. The zeolite-supported rhodium carbonyl clusters were treated in He or in H{sub 2} at 200, 250, or 300 C to remove the carbonyl ligands. When the decarbonylation took place in He, the resultant clusters had Rh-Rh coordination numbers (determined by extended X-ray absorption fine structure spectroscopy) between 3.5 and 3.9, with hardly any evidence of Rh-C contributions, indicating that the rhodium cluster frames were nearly intact and that decarbonylation was nearly complete. In contrast, when the treatment took place in H{sub 2}, partially decarbonylated rhodium clusters and aggregates formed, having Rh-Rh coordination numbers between 3.8 and 6.7; the rhodium aggregation increased with increasing temperature. The clusters formed by treatment in He at 200, 250, or 300 C all had similar catalytic activities of the clusters and aggregates (partially decarbonylated at temperatures <300 C) formed in the presence of H{sub 2} showed a strong dependence on treatment temperature, which is explained by inhibition by the remaining CO ligands and by cluster and aggregate size effects, with the aggregates being more active than the smaller clusters. Comparison of the data with those reported separately for rhodium clusters in NaX zeolite shows that NaY and NaX zeolites were nearly equivalent as supports. Comparison of the data with separately reported data indicates that the rhodium clusters are approximately the same in activity as iridium clusters of nearly the same size in NaY zeolite.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: FG02-87ER13790; FG02-89ER45384; AC02-76CH00016
• OSTI ID: 316311
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 180; ISSN JCTLA5; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
CARBONYLS
CATALYTIC EFFECTS
COMPARATIVE EVALUATIONS
FAUJASITE
HYDROGENATION
RHODIUM COMPOUNDS
TOLUENE