PREPARATION AND CHARACTERIZATION OF COPPER-BASED BIMETALLIC CATALYSTS

Cu-M (M = Pt, Au, Ru) bimetallic catalysts were prepared by direct reduction of the corresponding metallic ions by Raney copper powders in aqueous media. The redox reaction was followed by pH and COPPer ions concentration measurements. The alkaline dealumination of a CuAl alloy powder (50/50 wt.%) produced non isotropic grains with various crystallographic planes (extended faces and corresponding rims). Depending on the relative redox potential of M(n+)/M and Cu(n+)/Cu the deposit on the grain exhibits a selectivity. The rim sites of copper (Cu(I)) are oxidized first and Ru3+ can only oxidize these sites. For Pt4+ and Au3+, in contrast, all Cu(I) and Cu(0) sites are involved. The location of the deposits is related to the selectivity for the polyol transformations on the bimetallic catalysts.