Conversions of n-pentane, n-hexane, 3-methylpentane, n-heptane, 2-methylhexane, 3-methylhexane, 3-ethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 2,2-dimethylpentane, 3,3-dimethylpentane, n-octane, and 2-methylheptane to aromatics, skeletal isomers, C5-cyclic products, and fragments were studied on Pt black catalysts and compared to each other. Yields of these skeletal reactions show maxima as a function of the hydrogen pressure between 5 and 60 kPa (35 and 450 Torr) hydrogen pressure. Low hydrogen pressures favor highly dehydrogenated surface intermediates leading to aromatization and/or hydrogenolysis. Under higher hydrogen pressures, C5-cyclic intermediates prevail: these give cyclopentane and/or skeletal isomers. Radiotracer studies confirm that the main route of skeletal isomerization involves C5-cyclic intermediates. A new type of hydrogenolysis, "C5-unit splitting", is reported. Comparison of the present results with single-crystal data by Somorjai et al. permits us to suggest that the hydrogen control of the selectivities by controlling the surface intermediates may be valid for both types of catalysts.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry