High Nickel Loading Research Articles

Study of copper-nickel alloy formation on silica supports by the magnetostatic and other methods

Magnetostatic and resonance methods have demonstrated the formation of alloys in several silica-supported copper-nickel systems whose metal loadings were varied between 1 and 10% wt. The preparations studied were obtained by impregnation, ion exchange and coprecipitation techniques. In most systems the metals were believed to be reduced but for samples prepared by impregnation with a metal sulfate some sulfide formation was indicated. In all the bimetallic samples the composition of the alloy particles was found to be nonuniform. The two-phase “cherry” model demonstrated for large particles at temperatures and compositions where the Cu-Ni system is characterized by a miscibility gap, is not found applicable to the much smaller particles in supported Cu-Ni catalysts. Incorporation of a calcination step or reduction of the surface area of the support lowered the degree of dispersion but led to more homogeneous alloys. The conclusions from the magnetic data were confirmed and augmented by X-ray diffraction results, which demonstrated for the precalcined preparations a preferential copper oxide reduction. It is also shown that the preparation of fairly homogeneous supported copper-nickel alloys is assisted by using high relative nickel loadings in those cases where there is an enhanced oxide miscibility prior to reduction.