Alloys cyclohexane dehydrogenation over

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). 

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.

In contrast, the rate of cyclohexane dehydrogenation increases slightly for small contents of Cu in the alloy, then remains constant over a wide range, and only decreases at high Cu contents. Such effects are also noticeable for other alloys in cyclohexane dehydrogenation. For example, Pd/Ni, Pd/Ru, and Pd/Pt alloys have higher activities than Pd alone. 

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