Hydrogenation of Nitro Compounds Catalyzed by Urushibara Nickel Catalysts

The Urushibara nickel catalysts were prepared by reducing nickel chloride with Zn powder. The structure and composition of the catalysts were characterized by X-ray diffraction, inductively coupled plasma analysis, and transmission electron microscopy. The optimal preparation conditions of the catalysts were determined. The Urushibara nickel catalysts were applied to the selective hydrogenation of m-dinitrobenzene to m-phenylenediamine and 2,5-dichloronitrobenzene to 2,5-dichloroaniline. The effects of Zn powder, developing agent, temperature of catalyst preparation and reaction conditions such as solvent and pressure on the catalyst activity were studied. The Urushibara nickel catalysts exhibited high catalytic activity and selectivity for m-phenylenediamine and 2,5-dichloroaniline. The optimized content of water in solvent remarkably promoted the reaction. An appropriate quantity of the dechlorination inhibitor in the hydrogenation of 2,5-dichloronitrobenzene evidently increased the reaction rate and the selectivity for 2,5-dichloroaniline. The catalysts could be reused five times without any significant loss in their catalytic activity.