Iridium clusters in NaX zeolite cages: Synthesis, characterization, and selective catalysis of CO hydrogenation
- Univ. of Delaware, Newark, DE (United States)
[Ir(CO)[sub 2](acac)] in the pores of NaX zeolite was treated in CO at 1 atm and various temperatures and characterized by infrared and extended X-ray absorption fine structure (EXAFS) spectroscopies. The iridium precursor was converted predominantly into [HIr[sub 4](CO)[sub 11]][sup [minus]] at 70[degrees]C, and predominantly into [Ir[sub 6](CO)[sub 15]][sup 2[minus]] at 175[degrees]C, as indicated by infrared spectra. The infrared spectra indicate that both of these clusters interact through ion pairing with the zeolite support. The chemistry of their synthesis in the zeolite cages parallels that on the basic MgO surface and in basic solutions. The zeolite-supported samples catalyzed CO hydrogenation at 20 atom and 250[degrees]C, having a relatively low activity in comparison with those of typical Fischer-Tropsch catalysts. The catalyst gave a non-Schulz-Flory distribution of hydrocarbon products with a maximum at C[sub 1] and a relative maximum at C[sub 4]. Infrared and EXAFS spectra of the catalyst used with equimolar CO + H[sub 2] feed showed that the predominant iridium-containing species was [Ir[sub 6](CO)[sub 15]][sup 2[minus]]. 46 refs., 5 figs., 3 tabs.
- DOE Contract Number:
- FG05-89ER45384; AC02-76CH00016
- OSTI ID:
- 5602153
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 142:2; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBONYLS
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COMPLEXES
FISCHER-TROPSCH SYNTHESIS
HETEROGENEOUS CATALYSIS
HYDROGENATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
IRIDIUM COMPLEXES
MATERIALS
MINERALS
OXIDES
OXYGEN COMPOUNDS
SILICATE MINERALS
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY
ZEOLITES