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

The reduction of silica-supported nickel catalysts with hydrogen at temperatures higher than 873-923 K modifies the properties of the metallic particles. These modifications have been analysed through catalytic activity and selectivity variations, magnetic measurements, controlled atmosphere X-ray diffraction, temperature-programmed oxidation and Fourier-transform infrared spectroscopy, with carbon monoxide as a probe molecule. The modifications are not due to the sintering of nickel particles but seem to arise from an interaction between nickel and fractions of partially reduced carrier, both in the bulk and at the surface of the metallic particles.