Bimetallic catalysts. V. Kinetics of the hydrogenolysis of butane over Pt-Mo/SiO[sub 2] catalysts

Journal Article · Mon Nov 01 00:00:00 EST 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1318· OSTI ID:5078463

Leclercq, G; Gharbi, A El; Pietrzyk, S ^[1]

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1. Universite des Sciences et Technologies de Lille, Cedex (France)

The kinetics of the hydrogenolysis of butane on various Pt-Mo catalysts deposited on silica with the same metal content but with various Mo/(Mo + Pt) ratios has been studied. The hydrogenolysis of the two different kinds of C-C bonds has been distinguished. It is shown that the addition of Mo to Pt drastically changes the selectivity of the reaction, but that this selectivity is approximately the same for all the bimetallic Pt-Mo catalysts. Using a rate equation that had already been used for the hydrogenolysis of alkanes (Maurel, R., Leclercq, G., and Leclercq, L., J. Catal. 44, 68 (1975)), calculation has been made of the values of the equilibrium adsorption constants ([lambda]) and those of the rate constants of the C-C bond splitting steps (k) for the hydrogenolysis of the terminal C-C bonds ([lambda][sub 1] and k[sub 1]) and of the middle C-C bond ([lambda][sub 2] and k[sub 2]). In this way it has been shown that only Pt alone, two different intermediaries with high [lambda] values are formed in which the C-C bonds will be broken further with different selectivities but with low rate constants. On the contrary, on all Pt-Mo catalysts, butane is adsorbed as a single intermediate adsorbed species with a much lower adsorption equilibrium constant than on Pt alone, but this adsorbed species is much more reactive (k[sub 1] and k[sub 2]). The adsorption equilibrium constants are the same for all Pt-Mo taking into account the margin of error, which shows that, on all Pt-Mo, butane is adsorbed on the same mixed Pt-Mo site of constant composition whatever the catalyst's composition. The number of these active sites (proportional to k[sub 1] and k[sub 2]) increases as Mo/(Mo + Pt) increases up to 25-30%, then it decreases. 38 refs., 3 figs., 5 tabs.

• OSTI ID: 5078463
• Journal Information: Journal of Catalysis; (United States), Vol. 144:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
10 SYNTHETIC FUELS
BUTANE
HYDROGENATION
MOLYBDENUM COMPLEXES
CATALYTIC EFFECTS
PLATINUM COMPLEXES
SILICA
CHEMICAL REACTION KINETICS
ALKANES
CHALCOGENIDES
CHEMICAL REACTIONS
COMPLEXES
HYDROCARBONS
KINETICS
MINERALS
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SILICON COMPOUNDS
SILICON OXIDES
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
100200 - Synthetic Fuels- Production- (1990-)