NaY zeolite-supported rhodium and iridium cluster catalysts: Characterization by X-ray absorption spectroscopy during propene hydrogenation catalysis

Journal Article · Mon Feb 15 04:00:00 EST 1999 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1998.2306· OSTI ID:328294

Weber, W A; Zhao, A; Gates, B C ^[1]

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

Clusters of rhodium and of iridium were synthesized in the cages of the sodium form of the faujasite zeolite Y by decarbonylation of zeolite-supported [Rh{sub 6}(CO){sub 16}] or [Ir{sub 4}(CO){sub 12}] in H{sub 2} at 200 or 300 C, respectively. Larger clusters (aggregates) of rhodium or iridium consisting of 10 to 20 atoms each on average were formed by treatment of zeolite-supported [Rh{sub 6}(CO){sub 16}] or [Ir{sub 6}(CO){sub 16}] in H{sub 2} at 250 or 300 C. The samples were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy under vacuum and in (a) H{sub 2}, (b) propene, and (c) H{sub 2}/propene mixtures (with catalytic hydrogenation taking place). The EXAFS data indicate that the clusters or aggregates were intact, with the metal frames changed undetectably in the presence of any of the gases, even during catalysis and at temperatures up to 140 C. In the presence of propene only, rhodium clusters showed changes in their X-ray absorption near-edge spectra, but the iridium clusters did not. When propene was present with H{sub 2} during catalysis, the near-edge spectra were essentially the same as those characterizing the metal clusters (or aggregates) in H{sub 2} only. The data are consistent with the inference that the metal clusters, approximated as predominantly Ir{sub 4} or Rh{sub 6} (the latter not fully decarbonylated) are catalytically active themselves, as are larger aggregates of those metals.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-89ER45384; AC02-76CH00016
• OSTI ID: 328294
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 182; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
CATALYTIC EFFECTS
CHEMICAL PREPARATION
HYDROGENATION
IRIDIUM
MORPHOLOGY
PROPYLENE
RHODIUM
ZEOLITES