Reactions of alkanes on rhenium and rhenium-gold films

Abstract

Rhenium–gold films prepared for use in catalytic studies have been found by X-ray diffraction to be two-phased in the range 30–70 atom % Re. One phase (of h.c.p. structure) is rhenium-rich but of variable composition, the other (c.c.p.) unvarying and close to pure gold.

Skeletal catalytic reactions of n-hexane, methylcyclopentane, 3-methylpentane, n-pentane and isobutane with hydrogen on these films have been studied. Both 100 % Re and a 98 atom % Re alloy showed activity for rearrangement of isobutane. All three C₆ hydrocarbons gave benzene (580 K) which, it is inferred, is formed both from a methylcyclopentane precursor and by a 1,6-cyclization process involving n-hexane. The proportion of benzene formed by the latter route was greater on alloy films of 30 atom % or more of gold than on 100 % Re. Hydrogenolytic activity decreased to varying extents on alloying whereas activity for benzene production tended on balance to increase.

Some comparative experiments with tungsten and tantalum films, giving similar results, are also reported.