Selective hydrogenation of unsaturated nitriles to unsaturated amines over amorphous CoB and NiB alloys doped with chromium

Amorphous binary (CoB, NiB) and ternary (CoBCr, NiBCr) alloys prepared by chemical reduction with NaBH4 were characterized by atomic absorption spectroscopy (AAS), nitrogen physisorption (BET), X-ray diffraction (XRD), temperature programmed desorption (TPD), temperature programmed reduction (TPR), hydrogen chemisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) and the influence of their properties on catalytic performance in the hydrogenation of unsaturated nitriles to unsaturated amines was studied. The hydrogenation over NiB(Cr) catalysts lead to preferential hydrogenation of the C=C bond, whereas the hydrogenation over CoB(Cr) catalysts Occurred preferentially to the unsaturated amine. Addition of chromium dramatically increased the activity of both NiB and CoB catalysts, due to its effect on the binding energy of adsorbed hydrogen and the adsorption strength of the nitrile functional group. Amorphous cobalt borides treated with sodium hydroxide can hydrogenate unsaturated nitrites to primary unsaturated amines with medium-to-high selectivity without the presence of ammonia. (c) 2006 Elsevier B.V. All rights reserved.