Kinetic and mechanistic study of cyclohexene disproportionation: example of irreversible hydrogen transfer

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(88)90098-X· OSTI ID:7052918

Rebhan, D M; Haensel, V

The kinetics and mechanism of cyclohexane disproportionation, as well as its structure sensitivity, have been studied over a variety of Group VIII metal catalysts (i.e., Pt, Pd, and Ni). The goal of this work was to better understand how hydrogen transfer occurs in heterogeneous catalysis. Three reactions were studied: cyclohexene disproportionation, cyclohexene hydrogenation, and benzene hydrogenation. A gas-phase, microcatalytic reactor was used to obtain the data. The results were analyzed in terms of their activities, apparent activation energies, and selectivities. It was found that all the catalysts (except 0.001% Pt/Al/sub 2/O/sub 3/) were active catalysts for benzene hydrogenation. The apparent E/sub a/'s were between 42 and 50 kJ/mole. The activities decreased in the following manner, Pt > Ni > Pd. In contrast, during cyclohexene disproportionation, the apparent E/sub a/'s varied among catalysts (Pt approx. = 84, Pd approx. = 50, and Ni approx. = 25 kJ/mole), but their activities at 100/sup 0/C were similar (except 0.01 and 0.001% Pt/Al/sub 2/O/sub 3/). There existed a transition temperature below which the correct stoichiometry for cyclohexene disproportionation was observed, and above which the selectivity (measured as moles cyclohexane produced/moles benzene produced) decreased with temperature. This transition temperature varied with type of metal (T was 60/sup 0/C for Ni, 90/sup 0/C for Pd, and 110/sup 0/C for Pt).

• Research Organization: Univ. of Massachusetts, Amherst (USA)
• OSTI ID: 7052918
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 111:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
ACTIVATION ENERGY
ALKENES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AROMATICS
BENZENE
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL REACTORS
CYCLOALKENES
ELEMENTS
ENERGY
HETEROGENEOUS CATALYSIS
HYDROCARBONS
HYDROGEN TRANSFER
HYDROGENATION
KINETICS
METALS
NICKEL
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PERFORMANCE TESTING
PLATINUM
PLATINUM METALS
REACTION KINETICS
REDUCTION
TEMPERATURE EFFECTS
TESTING
TRANSITION ELEMENTS