title: Hydrogenolysis of cyclohexane over Ir/SiO(2) catalyst: a mechanistic study of carbon--carbon bond cleavage on metallic surfaces.
abstract: The hydrogenolysis of cyclohexane catalyzed by supported Ir/SiO(2) has been studied to get mechanistic information on the elementary steps of C--C bond cleavage for cyclic saturated hydrocarbons. The reaction was studied under conditions in which no dehydrogenation to benzene occurs. When a mixture of cyclohexane and H(2) flows over a Ir/SiO(2) catalyst at 200 degrees C and for a H(2)/cyclohexane ratio superior to 40, methane, ethane, propane, n-butane, n-pentane, and n-hexane are identified to be primary products. The hydrogenolysis of ethane and n-hexane has also been studied to clarify several mechanistic questions. To account for the primary products in the above reactions, a mechanism is proposed in which the key step of the carbon--carbon bond cleavage occurs via concerted electronic transfer in dimetallacyclopentane intermediate. The comparison of product distributions in the hydrogenolysis of cyclohexane and that observed for n-hexane led to conclusions about the relative ease of carbon--carbon bond cleavage with respect to surface alkyl isomerization.
authors.affiliation: Laboratoire de Chimie Organométallique de Surface, UMR 9986 CPE Lyon-CNRS, 43 boulevard du 11 novembre 1918, F-69616 Villeurbanne Cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Locatelli
authors.forename: J P
authors.initials: JP
authors.lastname: Candy
authors.forename: B
authors.initials: B
authors.lastname: Didillon
authors.forename: G P
authors.initials: GP
authors.lastname: Niccolai
authors.forename: D
authors.initials: D
authors.lastname: Uzio
authors.forename: J M
authors.initials: JM
authors.lastname: Basset