Benzene hydrogenation over supported and unsupported palladium. I. Kinetic behavior
The kinetics of benzene hydrogenation over supported Pd catalysts and unsupported Pd powder were examined under a wide range of reaction conditions. At temperatures below 433 K, apparent activation energies were routinely near 12.0 kcal/mol. The reaction order in hydrogen for supported catalysts increased from 0.5 to nearly 4 as the temperature increased from 353 to 573 K, and this same parameter for Pd powder showed a similar trend but was more temperature sensitive. The reaction order in benzene increased from zero to 0.8 over the same temperature range but a smaller difference was observed between the results obtained for supported and unsupported Pd. The activity of all the samples showed a temperature-dependent maximum near 495 K, but the unsupported Pd had a greater tendency to exhibit deactivation which was attributed to carbonaceous surface species formed from reversible dehydrogenation of adsorbed benzene. The lowest turnover frequencies occurred on the Pd powder whereas values 10-50 times higher were obtained over low-temperature reduced Pd catalysts prepared using Cl-containing precursors and acidic supports such as SiO/sub 2/-Al/sub 2/O/sub 3/ and TiO/sub 2/. The enhanced activity over these last two catalysts is attributed to additional benzene adsorption sites present on the support surface in the metal-support interfacial region. 51 references.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- DOE Contract Number:
- FG02-84ER13276
- OSTI ID:
- 5231371
- Journal Information:
- J. Catal.; (United States), Vol. 107:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BENZENE
HYDROGENATION
PALLADIUM
CATALYTIC EFFECTS
ACTIVATION ENERGY
ALUMINIUM OXIDES
CATALYST SUPPORTS
CHEMICAL REACTION KINETICS
COMPARATIVE EVALUATIONS
DEACTIVATION
SILICA
TEMPERATURE DEPENDENCE
TITANIUM OXIDES
ALUMINIUM COMPOUNDS
AROMATICS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
ENERGY
HYDROCARBONS
KINETICS
METALS
MINERALS
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REACTION KINETICS
SILICON COMPOUNDS
SILICON OXIDES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
020400* - Petroleum- Processing