Alumina-Supported Trirhenium Clusters: Stable High-Temperature Catalysts for Methylcyclohexane Conversion

Journal Article · Tue May 19 04:00:00 EDT 2009 · J. Phys. Chem. C112:3383,2008

OSTI ID:953092

Lobo-Lapidus, R J; McCall, M J; Lanuza, M; Tonnesen, S; Bare, S R; Gates, B C

Samples prepared from H{sub 3}Re{sub 3}(CO){sub 12} adsorbed on porous {gamma}-Al{sub 2}O{sub 3} were decarbonylated at 773 K in flowing H{sub 2} and characterized by X-ray absorption spectroscopy (XAS). X-ray absorption near-edge spectra show that rhenium in the treated sample was cationic, and extended X-ray absorption fine structure spectra show a Re-Re first-shell coordination number of approximately 2, consistent with trirhenium clusters bonded to the support. The samples were tested as catalysts for the conversion of methylcyclohexane in the presence of H{sub 2} at atmospheric pressure and at 723 and at 773 K in a flow reactor. A range of hydrocarbon products was observed, indicating the occurrence of dehydrogenation, isomerization, ring opening, and hydrocracking reactions. The catalyst used at 723 K underwent deactivation over a period of several hours, during which the selectivity for the major dehydrogenation product (toluene) increased significantly. At 773 K, the catalyst underwent activation, during which the product distribution changed. This increase in activity was retained when the temperature was reduced to 723 K, resulting in higher activity and different selectivity relative to what had been observed before at this temperature. The fresh and used catalyst samples were characterized by X-ray absorption spectroscopy, which showed that the trirhenium framework remained intact after catalysis, although changes in the rhenium coordination were observed. The catalytically active species are inferred to be trirhenium.

• Research Organization: Stanford Linear Accelerator Center (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 953092
• Report Number(s): SLAC-REPRINT-2009-192
• Journal Information: J. Phys. Chem. C112:3383,2008, Journal Name: J. Phys. Chem. C112:3383,2008 Journal Issue: 9 Vol. 112; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALUMINIUM OXIDES
CATALYSIS
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CYCLOALKANES
DEACTIVATION
DEHYDROGENATION
HYDROCRACKING
ISOMERIZATION
Other
CHEM
PHYS
RHENIUM