The role of tellurium and antimony in PtTe/Al sub 2 O sub 3 and PtSb/Al sub 2 O sub 3 reforming catalysts
- Louisiana State Univ., Baton Rouge (USA)
PtTe/Al{sub 2}O{sub 3} and PtSb/Al{sub 2}O{sub 3} bimetallic catalysts were studied using the model n-hexane isomerization, aromatization, and hydrocracking reactions at 673 K and the cyclohexane dehydrogenation reaction at 573 K, under atmospheric pressure in a recirculation batch reactor. An increase in the selectivity for isomerization (and a corresponding decrease in hydrocracking selectivity) was found for all coimpregnated PtTe/Al{sub 2}O{sub 3} and PtSb/Al{sub 2}O{sub 3} catalysts compared to Pt/Al{sub 2}O{sub 3}. The change in selectivity can be caused either by electronic effects, which increase the specific activities for isomerization, or by geometric effects, which reduce the rate of hydrocracking. The results of the kinetic experiments, along with FTIR spectroscopy of adsorbed CO using the isotopic dilution method, suggest that electronic effects can be identified with Te/Pt alloying in catalysts of low (Te/Pt < 0.06) Te content, while geometric effects predominate in catalyst formulations more concentrated in the post-transition metal. The dehydrogenation turnover frequencies were also enhanced at low Te/Pt ratio; in this respect the dehydrogenation and isomerization reactions are similar. Direct six-member ring closure, rather than ring expansion by way of an adsorbed methylcyclopentane intermediate, accounted for most of the production of benzene. PtTe/Al{sub 2}O{sub 3} catalysts were also prepared by vapor deposition of Te onto Pt/Al{sub 2}O{sub 3}. These catalysts exhibited selectivities which were influenced by the type of carrier gas used to deposit the tellurium. A carrier gas containing n-hexane improved the selectivity relative to hydrogen or helium carrier gases. The mechanism of this selectivity effect is unknown but possibly due to carbon incorporation into a Pt-Te alloy.
- OSTI ID:
- 6469754
- Journal Information:
- Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 116:2; ISSN 0021-9517; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Neopentane reactions over bimetallic Pt-Sn/Al sub 2 O sub 3 and Pt-Au/SiO sub 2 catalysts
Pt/Al{sub 2}O{sub 3} catalysts and Pt-Sn/Al{sub 2}O{sub 3} catalysts prepared by two different methods: Hydrogen pressure effects in the reactions of n-hexane
Related Subjects
020400* -- Petroleum-- Processing
ADSORPTION
ALKANES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ANTIMONY
AROMATICS
ATMOSPHERIC PRESSURE
BENZENE
BIMETALS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
CRACKING
CYCLOALKANES
CYCLOHEXANE
DECOMPOSITION
DEHYDROGENATION
ELEMENTS
FOURIER TRANSFORMATION
HEXANE
HYDROCARBONS
HYDROCRACKING
INFRARED SPECTRA
INTEGRAL TRANSFORMATIONS
ISOMERIZATION
METALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PETROLEUM PRODUCTS
PLATINUM
PLATINUM METALS
PROCESSING
PYROLYSIS
REACTION INTERMEDIATES
REFINING
SEMIMETALS
SORPTION
SPECTRA
SPECTROSCOPY
SYNTHESIS
TELLURIUM
THERMOCHEMICAL PROCESSES
TRANSFORMATIONS
TRANSITION ELEMENTS