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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 H_2-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 Ar-Cl...H~+Ni~-.And then C-Cl bond could not be polarized and activated.The hvdrodechlorination process was suppressed effectively.
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 at at the conversion of 100%. The results of H 2 -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. Chen 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 Ar-Cl ... H ~ + Ni ~ -And then C-Cl bond could not be polarized activated. hvdrodechlorination process was suppressed effectively.