Impact of calcination conditions on the structure of alumina-supported nickel particles

Alumina-supported nickel catalysts are widely used in industry. The synthes is of these catalysts often proceeds through coprecipitation: following the precipitation of nickel salts and drying, the material is calcined, reduce d, and passivated. Each of these steps may influence the catalyst ultimatel y obtained. In the present study, the synthesis conditions were systematica lly investigated. Following precipitation, a hydrotalcite is formed. Starti ng from hydrotalcite precursors with varying Ni/Al ratios, the conversion t o the ultimate Ni-on-alumina catalyst was studied, using TEM, TPR, XRD, and chemisorption. In particular, we examined the effect of water vapour and a cidic gases-liberated during calcination-on the morphology of the catalyst ultimately obtained. Two competing mechanisms for the formation of the ulti mate catalyst morphology are suggested. (C) 2001 Academic Press.