The Influence of Hydrazine Reduction on Metal Dispersion and Support Morphology in Bimetallic Ru-Au/MgO Catalysts

The influence of hydrazine reduction on metal dispersion, particle size distribution, and support morphology was investigated for a series of bimetallic Ru-AuiMgO catalysts. The catalysts were prepared by impregnation of MgO with chlorine-containing precursor salt solutions. Hydrazine reduction significantly lowered the residual chlorine content of the catalysts and allowed the formation of high-surface-area MgO. This, in turn, led to much higher Ru metal dispersions as compared to that obtained after HZ reduction alone. X-Ray energy dispersive spectroscopy (EDS) proved that bimetallic Ru-Au aggregates were confined to a particle size range of less than 5 nm. Particles larger than 10 nm contained without exception monometallic Au. The hydrazine-treated catalysts did not show the suppression in catalytic activity for CO hydrogenation that was observed in HZ-reduced Ru/MgO catalysts. The increased metal dispersion and restored catalytic activity of Ru in the hydrazine-treated catalysts may be linked to the absence of chlorine contamination of the support.