Hydrogenolysis of alkanes. Part 1.—Hydrogenolysis of ethane, propane and n-butane on 6% Pt/SiO2(EUROPT-1)

Abstract

The hydrogenolysis of ethane, propane and n-butane has been studied on a 6.3% platinum/silica catalyst (EUROPT-1); for ethane the rate and other kinetic parameters agree well with literature values. Treatment of the catalyst in hydrogen between 623 and 1173 K leads to a loss of capacity for hydrogen chemisorption greater than that attributable to an increase in particle size, and to an even greater loss of activity for n-butane hydrogenolysis, partly restorable by oxidation. Extensive reorganisation of the metal occurs during a short oxidation at 873 K.

Product selectivities to methane, ethane and propane are interpreted by a simple but comprehensive reaction network due to Kempling and Anderson; this is thought to be more informative than the usual approach of assuming that two or more reactions proceed in parallel. Selectivities are not much changed by the thermal treatments. This observation, coupled with the fact that the activity for ethane hydrogenolysis, according to the literature, varies greatly from one platinum catalyst to another while the activation energy and reaction orders scarcely alter, strongly suggests that each hydrogenolysis reaction demands a uniquely defined active site for initiation of the reaction, whereafter it proceeds in a uniform manner.