Hydrogenolysis of alkanes with quaternary carbon atoms over Pt and Ni black catalysts

Abstract

Hydrogenolysis of hydrocarbons with quarternary C atoms (neopentane, neohexane, 2,2,3-trimethyl-butane, 2,2- and 3,3-dimethylpentanes and 2,2,3,3-tetramethylbutane) has been studied over Pt and Ni black catalysts. The reactivities of different types of C—C bond have been determined. The probability of C—C bond rupture where one of the carbon atoms is quaternary is inversely proportional to the bond dissociation energy. On Pt, two essential types of hydrogenolysis can be distinguished. One reaction is responsible for the breaking of internal C—C bonds attached to the quaternary carbon atom and the other for demethylation. With larger molecules, the former reaction is preferred and the surface intermediate should be 1,4-diadsorbed, while that for the latter reaction is 1,3-diadsorbed. Nickel, as previously suggested, causes terminal C—C rupture, although with branched hydrocarbon reactants internal C—C bond rupture is also possible, presumably via 1,4-adsorption.