INFLUENCE OF THE REDUCTION TEMPERATURE ON THE PROPERTIES OF SILICA-SUPPORTED NICKEL-CATALYSTS

The reduction of silica-supported nickel catalysts with hydrogen at te mperatures higher than 873-923 K modifies the properties of the metall ic particles. These modifications have been analysed through catalytic activity and selectivity variations, magnetic measurements, controlle d atmosphere X-ray diffraction, temperature-programmed oxidation and F ourier-transform infrared spectroscopy, with carbon monoxide as a prob e molecule. The modifications are not due to the sintering of nickel p articles but seem to arise from an interaction between nickel and frac tions of partially reduced carrier, both in the bulk and at the surfac e of the metallic particles.