THE REACTIONS OF AZOPROPANE, N-BUTANE AND N-BUTENES OVER RUTHENIUM

The Fischer-Tropsch reaction involves hydrocarbon fragments and other coadsorbed species on the surface and its selectivity is controlled by termination reactions of the alkyl fragments. This research addressed several ways to generate and study alkyl fragment surface reactions.; Azopropane was brought in contact with a freshly reduced RuSiO(,2) catalyst at room temperature using pure He or a H(,2)/He mixture as the carrier gas. The large amount of nitrogen formed suggests that azopropane is a viable source for generating propyl fragments on the Ru/SiO(,2) catalyst. However, room temperature was found to be too high to isolate the reactive propyl fragments. By applying a controlled-temperature increase technique during desorption, the scission and formation of the C-N, C-H and C-C bonds over the catalyst were observed. When only He was used as the carrier gas, propionitrile was formed through the breakage of the N-N bond. The addition of 20% hydrogen to the carrier gas stream enhanced the formation of propane. When pure hydrogen was used as the carrier gas, the C(,3)-fragments on the surface were further hydrogenated to methane and ethane (hydrogenolysis), along with the formation of other nonbranched hydrocarbons with higher carbon numbers (homologation). It was demonstrated that surface alkyl fragments are very reactive and that they must be formed and characterized at the same time.; The reactions of n-butane and n-butenes were investigated over Ru/SiO(,2) at 150(DEGREES)C and a H(,2)/reactant ratio of 11 by using a pyridine scavenging technique. For n-butane, a relatively larger amount of sec-butylpyridine than n-butylpyridine was found consistent with published mechanisms in which hydrogenolysis occurs through random C-H bond cleavage. The Horiuti-Polanyi mechanism was used to explain the hydrogenation of 1-butene over Ru/SiO(,2). No C(,4)-alkylpyridines were found for the internal butenes. This was used to suggest an alternate mechanism for internal butene hydrogenation that does not involve an alkyl species. No homologation was found for n-butane, which is different from the results of the n-butenes, where homologatin was always detected. This led to the suggestion that for homologation to occur, both an unsaturated carbon-carbon bond and a methylene species are required. Both syn-(pi)-allyl (from 1-butene and trans-2-butene) and anti-(pi)-allyl (from 1-butene and cis-2-butene) are reactive toward methylene to form metallacyclobutane. Metallacyclobutane was proposed to be the intermediate for homologation. (Abstract shortened with permission of author.)...