NICKEL-ALUMINA PREPARED BY CONSTANT AND VARYING PH METHOD - EVALUATION BY HYDROGEN-OXYGEN CHEMISORPTION AND ANILINE HYDROGENATION

Ni/Al2O3 catalysts with different weight percentages of nickel (10-50 wt.-%) were prepared by a co-precipitation method under constant and v arying pH conditions. Bulk density, pore volume and surface area of th e catalysts were measured. The catalysts were characterized by X-ray d iffraction. Hydrogen and oxygen chemisorptions were used to measure th e metal area, percentage reducibility and metal dispersion. The crysta llite size, as calculated from adsorption measurements, is very high. This is explained as being due to poor dispersion. Aniline hydrogenati on under vapour phase conditions over these catalysts was studied. Cat alysts prepared by the constant pH method show higher activity compare d to those prepared by the varying pH method, especially at low metal content, N-phenylcyclohexylamine is the major product. The mechanism o f product selectivity under different experimental conditions is expla ined.