Skeletal Reactions of Heptane Isomers over EUROPT-1: A Comparison with Pt Black.

The reactions of five heptane isomers (n-heptane, 3-methylhexane, 3-ethylpentane, 2,4-dimethyl-pentane, and 3,3 dimethylpentane) are compared over a 6.3% Pt/SiO[sub 2] catalyst (EUROPT-1) as a function of the hydrogen pressure between 6 and 60 kPa. Preferred reactions are isomerization and C[sub 5]-cyclization: substituted pentanes exhibit higher reactivity and higher C[sub 5]-cyclization ability. Increasing H[sub 2] pressures enhance the reactivities in most cases, except for aromatization and C[sub 5-]-cyclization, where maxima are observed. The observed product compositions (including fragments involving more than one C-C bond rupture) do not change within a rather wide conversion range. This is explained in terms of the metal catalyst being covered mainly by hydrocarbons; their reactivity, in turn, is determined first of all, by the amount of hydrogen available. Differences between EUROPT-1 and Pt black may be due to their different surface structure and purity. 35 refs., 6 figs., 3 tabs.