Dehydrogenation processes on nickel and platinum surfaces. Conversion of cyclohexane, cyclohexene, and cyclohexadiene to benzene

Described is the surface coordination chemistry of cyclohexane, 1,3 and 1,4-cyclohexadiene and cyclohexene on the low Miller index planesand a stepped surface of nickel and on the platinum ( 111) and stepped 6(lll)x(lll) surfaces as established by thermal desorption spectroscopy, chemical displacement reactions, and isotopic labeling studies.Cyclohexane did not react with Ni(lll) at o to 70°C,.Ni (110) at 20-90°C, Ni (100) at 25-200°C, and Ni 9 (111) x (111)at 20-70°C.A similar behavior was observed for Pt(lll) at -35 to +135°C although a small degree of dehydrogenation was evident on this surface.Definite evidence for cyclohexane conversion to benzene was obtained for ' the stepped platinum surface; the reactivity of this stepped surface toward cyclohexane was substantially higher than the platinum (111) plane.Cyclehexene and 1,3 and 1,4-cyclohexadiene were converted, at least partially, to benzene on all the nickel and platinum surfaces.Hydrogen-deuterLum (C-H) exchange during the conversion of a mixture of chemisorbed c 6 H 10 and c 6 o 10 and of a mixture of chemisorbed cyclohexadiene and deuterium atoms to benzene was evident only for the platinum surfaces.•carbon significantly altered the• cyclohexene chemistry on Ni{llO); Ni(llO)-C was far more effective than the clean surface for dehydrogenation of cyclohexene to benzene.A substantial carbon effect on the chemistry of the other surfaces was not evident.iii.