Highly selective hydrogenation of halonitroaromatics to aromatic haloamines by ligand modified Ni-based catalysts

Ligand modification of Ni-based catalysts by coordination of dicyandiamide to Ni metal leads to enhanced selectivity for the selective hydrogenation of halonitroaromatics. The selectivity of above 99.9% to aromatic haloamines can be achieved at the conversion of 100%. The results of H2–TPD and FT-IR experiments show that Ni−H+ species possessing the properties of Lewis acid site on the surface of Raney Ni could be responsible for the hydrodehalogenation. When Raney Ni was treated by dicyandiamide, Ni−H+ species interacted with N atom from the dicyandiamide. This interaction was stable even at reaction temperature, which reduced the possibility to form the intermediate state of ArCl⋯H+Ni−. And then CCl bond could not be polarized and activated. The hydrodechlorination process was suppressed effectively.