Benzene Hydrogenation Activities of Supported Nickel Catalysts in Relation to Their Chemisorption Properties

Samples of nickel on alumina (1.1–10.4 wt.% Ni) were prepared by impregnating alumina in hydrated nickel nitrate. The textural properties of the calcined catalysts have been determined from nitrogen adsorption at 77 K. Calcined catalysts were reduced prior to determination of the chemisorbed benzene at 308 K or chemisorbed hydrogen at 383 K. Hydrogenation of benzene was also determined at 473 K using the flow technique.

The surface area of NiO/Al₂O₃ catalysts decrease and their mean pore radii increase with an increase in NiO content. These changes are more pronounced for catalysts containing more than 5% metal. Chemisorption of benzene proceeds via the formation of π-bonds with nickel. The chemisorption of hydrogen indicated that the percentage dispersion decreases and the crystallite size increases with an increase in metal loading. Dispersion, crystallite size and metal surface are important factors in determining the activity of supported nickel catalysts for benzene hydrogenation.