Palladium compensation behavior

Fig. 5. Compensation behavior in reactions on palladium metal. The lines (Table 11) were calculated (Appendix II) for cracking ( ) and for exchange (x) and oxidation (o) processes (data references given in text).

The general pattern of compensation behavior found for platinum-catalyzed reactions was appreciably different from that described above for nickel and palladium. Moreover, since some of the trends were less well defined, these may not represent meaningful obedience to Eq. (2). 

This pattern of behavior resembles those described for nickel and for palladium in recognizing two groups of exchange processes but differs in that the data for the lighter molecules do not coincide with the line for the (more broadly defined) cracking reactions. A compensation trend has also been described for exchange reactions of butanes (2/7) from these measurements we calculate e = 0.1126 and ac = 0.0116. 

Compensation trends are found in the kinetic data reported for the catalytic hydrogenation of several hydrocarbons on bimetallic systems, including the reactions of ethylene on Ni-Cu and on Ni-Au alloys (252), buta-1,3-diene on Ni- Cu alloys (183), benzene on Ni-Cu (but the behavior of benzene on Cu-Pd was less obviously compensatory) (253), and the liquid phase hydrogenation of nitrobenzene on Pd Ag alloys (56). The kinetic characteristics of but-2-yne on Pd-Au alloys (28) was different in that E underwent little variation, while the value of log A systematically diminished as the proportion of palladium in the alloys was reduced. It was concluded that palladium was the active constituent and gold was an inactive diluent. 

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