Selective catalytic hydrogenation of bifunctional compounds over amorphous nickel alloys

The hydrogenation of bifunctional carbonyl compounds (2,2,4,4-tetramethyl-1,3-cyclobutanedione (1), 5-hexen-2-one (2) and (−)−verbenone (3)) was studied over amorphous Ni-P and Ni-B alloys. The amorphous Ni alloys were Ni-P and Ni-B powders prepared by chemical reduction, and Ni-P foils prepared by electrolytic reduction or rapid quenching. A commercial Raney Ni and 3% Ni/SiO₂ served as reference catalysts. The amorphous alloys exhibited lower catalytic activities, but much higher selectivities as compared to the polycrystalline nickel catalysts. Selective monohydrogenation of 1,3-diketone (1) to the corresponding hydroxy ketone took place on all amorphous catalysts, except on Ni-P foil prepared by electrolytic reduction. Here, exclusive ring-opening attributed to acidic centres occurred. The hydrogenation of unsaturated carbonyl compounds (2 and 3) took place in two consecutive steps. At 373 K the selective saturation of carbon-carbon double bond occurred, while at 398 K the carbonyl group too was reduced to a hydroxy group, yielding saturated alcohols. In contrast, the conventional polycrystalline catalysts yielded a mixture of the corresponding hydroxy ketone and diol from 1, and saturated ketones and alcohols from 2 and 3, even at low temperature.