THE H/D EXCHANGE AND HYDROGENOLYSIS OF PROPANE ON ALUMINA-SUPPORTED NICKEL-CATALYST

The exchange of propane with deuterium on an alumina-supported nickel catalyst has been studied over a range of temperature (80-190°C) and two hydrocarbon/deuterium ratios. The results are interpreted in terms of a model containing three parameters in which two different adsorbed species are assumed: in the "alkyl" species one H-atom is exchanged in a single adsorption step, and the triadsorbed species exchanges at least three H-atoms per sojourn of the hydrocarbon molecule on the surface of the catalyst. The adsorbed species may undergo multiple exchange per adsorption step. The exchange of CH3 · CD2 · CH3 and CD3 · CH2 · CD3 with H2 and D2 was also studied. This showed that the monoadsorbed species is mainly adsorbed at the methyl group and the triadsorbed species twice at a methyl group and once at the methylene group. The hydrogenolysis reactions of propane were studied in the same system between 190 and 240°C. A wide range of conversion was covered, and the product distributions were fitted to kinetic equations in order to obtain the initial rate constants, i.e., selectivities. The nickel/alumina catalyst leads to multiple hydrogenolysis. Several CC bonds are broken before the adsorbed species are desorbed. Under the conditions used in these experiments, surface cracking is the rate-limiting step. © 1990.