Mechanism of catalytic hydrogenation of but-1-yne on palladium

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(88)90044-9· OSTI ID:7128622

Hub, S; Touroude, R ^[1]

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1. Universite Louis Pasteur, Strasbourg (France)

The deuteration mechanism of but-1-yne on differently dispersed Pd/Al{sub 2}O{sub 3} catalysts (D = 26%, >80%) was studied at 293 K. Experiments were performed by flowing a hydrocarbon square pulse at constant pressure (15 Torr) and a H{sub 2}-He carrier gas (37-708 Torr) onto the catalyst. Three stages were observed, namely (i) an initial stage with high activity and very low selectivity; the duration of this stage was proportional to the palladium weight and the number of hydrocarbon molecules which passed through the catalyst; (ii) a steady-state stage with constant activity and 98% but-1-ene selectivity; using microwave spectroscopy the authors found that in addition to the cis addition of two deuterium atoms, 10 to 20% of but-1-ene were produced by a different route; (iii) a final stage in which, when the hydrocarbon pressure decreased in the gas phase, an additional desorption peak was obtained consisting of C{sub 4} hydrocarbons. It is proposed that the palladium surface during the steady state is covered by strongly but reversibly adsorbed but-1-yne molecules which act as a poison and are in equilibrium with the reactive chemisorbed but-1-yne molecules. The reactive molecules are described as vinylic adsorbed species in equilibrium with carbene and carbyne species. The first lead to a cis addition mechanism. The latter two lead to the trans addition and direct hydrogenation.

• OSTI ID: 7128622
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 114:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
ALKENES
ALKYNES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BUTENES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DEUTERIUM
ELEMENTS
HYDROCARBONS
HYDROGEN ISOTOPES
HYDROGENATION
ISOTOPES
KINETICS
LAYERS
LIGHT NUCLEI
METALS
MICROWAVE SPECTRA
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
POISONING
REACTION KINETICS
SPECTRA
STABLE ISOTOPES
SURFACE PROPERTIES
TRANSITION ELEMENTS