Reactions of 2- and 3-methylpentane, methylcyclopentane, cyclopentane, and cyclohexane on activated Mo[sub 2]C

Journal Article · Wed Sep 01 00:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1270· OSTI ID:5738227

Pham-Huu, C; Ledoux, M J ^[1]; Guille, J ^[2]

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1. Universite Louis Pasteur, Strasbourg (France)
2. IPCMS, Strasbourg (France)

Molybdenum carbide, prepared by a new synthetic route and further activated either by reductive or by oxidative treatments, has been studied as a catalyst for isomerization of 2- and 3-methylpentane and also for hydrogenolysis of cyclopentane, cyclohexane, and methylcyclopentane. The nature of this activating pretreatment dramatically modifies both the activity and the selectivity of the catalyst. Reductive pretreatments lead either to inactive, or to active but poorly selective, catalysts (Mo metal on the surface or pure Mo carbide), whereas oxidative treatments first inhibits the hydrogenolysis reaction present on oxygen-free molybdenum carbide, and second, enhances the isomerization rate of the catalyst. The branched molecules isomerize to give mostly acyclic isomers. No deactivation is observed with time on stream during isomerization of the branched molecules. The rate of hydrogenolysis of methylcyclopentane and cyclopentane is about four times lower than the rate obtained with branched molecules, and the catalyst is strongly deactivated. This phenomenon is attributed to the formation of highly dehydrogenated polyaromatics, and to the formation of CH[sub 4], by demethylation of methylcyclopentane, which can irreversibly reduce the oxicarbide phase. The deactivated catalyst can easily be regenerated by a short oxidative treatment at 350[degrees]C. The results, in terms of both activity and isomer selectivity, obtained for n-hexane, 2-methylpentane, and 3-methylpentane isomerization are attributed to a bond-shift mechanism involving a metallocyclobutane ring intermediate which would take place on an oxicarbide phase. 23 refs., 1 fig., 6 tabs.

• OSTI ID: 5738227
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 143:1; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
CARBIDES
CARBON COMPOUNDS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CYCLOALKANES
CYCLOHEXANE
DEACTIVATION
HETEROGENEOUS CATALYSIS
HYDROCARBONS
ISOMERIZATION
MOLYBDENUM CARBIDES
MOLYBDENUM COMPOUNDS
ORGANIC COMPOUNDS
REACTION INTERMEDIATES
REFRACTORY METAL COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS