The role of tellurium and antimony in PtTe/Al sub 2 O sub 3 and PtSb/Al sub 2 O sub 3 reforming catalysts

Journal Article · Sat Apr 01 00:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90100-0· OSTI ID:6469754

Cheng, C H; Dooley, K M; Price, G L ^[1]

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1. 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), Vol. 116:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
ANTIMONY
CATALYTIC EFFECTS
CYCLOHEXANE
DEHYDROGENATION
HEXANE
HYDROCRACKING
ISOMERIZATION
PLATINUM
TELLURIUM
ADSORPTION
ALUMINIUM OXIDES
ATMOSPHERIC PRESSURE
BENZENE
BIMETALS
CARBON MONOXIDE
CATALYST SUPPORTS
CATALYSTS
CHEMICAL PREPARATION
COMPARATIVE EVALUATIONS
CYCLOALKANES
FOURIER TRANSFORMATION
INFRARED SPECTRA
PETROLEUM PRODUCTS
REACTION INTERMEDIATES
REFINING
SPECTROSCOPY
SYNTHESIS
ALKANES
ALUMINIUM COMPOUNDS
AROMATICS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CRACKING
DECOMPOSITION
ELEMENTS
HYDROCARBONS
INTEGRAL TRANSFORMATIONS
METALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
PROCESSING
PYROLYSIS
SEMIMETALS
SORPTION
SPECTRA
THERMOCHEMICAL PROCESSES
TRANSFORMATIONS
TRANSITION ELEMENTS
020400* - Petroleum- Processing