SURFACE CHARACTERIZATION OF PALLADIUM-COPPER BIMETALLIC CATALYSTS BY FTIR SPECTROSCOPY AND TEST REACTIONS

Different bi-metallic palladium-copper catalysts have been prepared ac cording to different sequences of impregnation of a commercial alumina . CO adsorption followed by FTIR spectroscopy was performed in order t o identify the nature of the superficial sites. Two test reactions wer e also used to characterize the nature of the active surface site: gas phase toluene hydrogenation was selected in order to show the hydroge nating activity of metallic palladium, whereas the reaction of decompo sition of ethanol, which exhibits 100% selectivity in the formation of ethanal on pure copper catalysts, was also studied on this series of catalysts. The results obtained by both methods are complementary. By comparison with the behaviour of pure palladium or copper based cataly sts, they allow to propose hypotheses on the surface composition: sepa rated phases, alloys or a phase covered by the other one.