PREPARATION AND CHARACTERIZATION OF COPPER-BASED BIMETALLIC CATALYSTS

Cu-M (M = Pt, Au, Ru) bimetallic catalysts were prepared by direct red uction of the corresponding metallic ions by Raney copper powders in a queous media. The redox reaction was followed by pH and COPPer ions co ncentration measurements. The alkaline dealumination of a CuAl alloy p owder (50/50 wt.%) produced non isotropic grains with various crystall ographic planes (extended faces and corresponding rims). Depending on the relative redox potential of M(n+)/M and Cu(n+)/Cu the deposit on t he grain exhibits a selectivity. The rim sites of copper (Cu(I)) are o xidized 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 transformat ions on the bimetallic catalysts.