Nickel-copper alloys cyclohexane dehydrogenation

At the same time that our work on ethane hydrogenolysis and cyclohexane dehydrogenation on nickel-copper alloys was published, a paper by Ponec and Sachtler on the reactions of cyclopentane with deuterium appeared (9). These workers reported data on the rates of formation of deuterocyclopen-tanes via exchange, and of CD4 by hydrogenolysis. The exchange reaction occurred at about the same rate (per surface nickel atom) on nickel-copper alloys as on pure nickel, while the rate of formation of CD4 was substantially decreased. 

Fig. 6. Activities of copper-nickel alloy catalysts for the hydrogenolysis of ethane to methane and the dehydrogenation of cyclohexane to benzene. The activities refer to reaction rates at 316° C. Ethane hydrogenolysis activities were obtained at ethane and hydrogen pressures of 0.030 and 0.20 atm., respectively. Cyclohexane dehydrogenation activities were obtained at cyclohexane and hydrogen pressures of 0.17 and 0.83 atm, respectively (74).

Figure 5.2.6 I Effect of alloy composition on the rates of ethane hydrogenolysis and cyclohexane dehydrogenation on Ni-Cu catalysts. (Figure from Catalytic Hydrogenolysis and Dehydrogenation Over Copper-Nickel Alloys by J. H.

Cusumano et al. (128) studied the reaction over Pt on alumina and on silica supports and concluded that the TOF was about the same for both catalysts, which did show quite different atomic rates AR. The later work of Sinfelt et al. (269) on reactions over copper-nickel alloys led also to the suggestion that cyclohexane dehydrogenation over Ni does not require a large ensemble of surface atoms and thus may be structure insensitive on a geometric basis. For ethane hydrogenolysis studied on the same CuNi alloys, it was found that the activity decreased much more rapidly than did the fraction of Ni atoms on the surface of the alloys. This implies that ethane hydrogenolysis requires an ensemble of surface atoms and should show antipathetic structure sensitivity. This reaction will be discussed in connection with Fig. 15 (below). 

Fig. 5-28. Specific activity of copper-nickel alloys for the dehydrogenation of cyclohexane and the hydrogenolysis of ethane to methane at 316 °C...

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