Ir/KLTL zeolites: Structural characterization and catalysis on n-hexane reforming

Journal Article · Fri Mar 01 04:00:00 EST 1996 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1996.0059· OSTI ID:263767

Triantafillou, N D; Gates, B C ^[1]

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1. Univ. of Delaware, Newark, DE (United States); and others

Ir/KLTL zeolite catalysts were prepared by incipient wetness impregnation of LTL zeolites with [Ir(NH{sub 3}){sub 5}Cl]Cl{sub 2}. The catalysts were characterized by extended X-ray absorption fine structure (EX-AFS) spectroscopy, infrared spectroscopy, and H{sub 2} chemisorption. EXAFS data show that the average Ir cluster size (after treatment at 300{degrees}C in H{sub 2}) increased from about 7 to 20 {Angstrom} as the zeolite K:Al atomic ratio increased from 0.34 to 1.56. Infrared spectra of adsorbed CO show that the electron donation to the Ir increased as the K:Al ratio increased. In contrast to the performance reported for Pt/KLTL zeolites with metal clusters as small as those observed in the present experiments, the Ir/KLTL catalyst has a low selectivity for dehydrocyclization of n-hexane at 440-480{degrees}C and 1 atm with a H{sub 2}: n-hexane feed molar ratio of 6. Instead, the catalysts are selective for hydrogenolysis. The selectivity is insensitive to the K:Al ratio, but the activity for dehydrocyclization is a maximum at a K:Al atomic ratio of about 1. The results show that even the smallest Ir clusters to which electron donation is significant still behave essentially like metallic Ir in the catalytic reactions. 49 refs., 4 figs., 7 tabs.

• OSTI ID: 263767
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 159; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
40 CHEMISTRY
ABSORPTION SPECTROSCOPY
CATALYSTS
CATALYTIC EFFECTS
CATALYTIC REFORMING
CHEMISORPTION
CYCLIZATION
DEHYDROGENATION
HEXANE
IRIDIUM
X-RAY SPECTROSCOPY
ZEOLITES