Selectivity of Product Formation in Alkane Hydrogenolysis

The procedure to be adopted is that expounded by R.B. Anderson and his associates, initially for n-butane, but later for more complex alkanes. The 

The reviewer of the literature faces considerable difficulties. Quite often, those studying the reactions of propane and -butane do not trouble to measure or report product selectivities, and when they are given it is most usually in graphical form, from which numbers of limited accuracy have to be extracted by tedious interpolation. Sometimes only ethane selectivities are quoted. Measurements made in UHV systems seem to be more scattered than those made in conventional equipment, and almost all values have to be converted into the Kempling-Anderson formalism (equations 13.13 and 13.14) to make them comparable. In the accompanying Tables 13.9 and 13.10, most values of F and Tj, are obtained by method (2) above. Although for n-butane products the values of 5i can easily be derived from S2 and 53,they are quoted in the tables to save the reader unnecessary labour. 

Our task is now to try to summarise the ways in which product selectivities vary with temperature and reactant pressures, especially that of hydrogen. 

Many of the cited publications give more results tiian those abstracted for liiis table, the purpose of which is to illustrate effects of metal, form, support, etc. 

Very little has been published on hydrogenolysis of the lower alkanes using either nickel or palladium ° catalysts, perhaps because both are liable to suffer rapid deactivation by carbon deposits, or to show unstable behaviour. With -butane, both gave predominantly terminal C—C bond fission at low conversion, but there are no detailed kinetic studies to report. 

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