Liquid-Phase Hydrogenation of Chloronitrobenzene to Chloroaniline over Ni-Co-B Amorphous Alloy Catalyst

Abstract The Ni-Co-B bimetallic amorphous alloy with Co/(Co+Ni) molar ratio varying from 0 to 1 was prepared by chemical reduction of Ni(NO3)2 and Co(NO3)2 with KBH4 in solution. Its amorphous structure was verified by X-ray powder diffraction and selected area electron diffraction. The thermostability of the amorphous alloy was characterized by thermogravimetry-differential thermal analysis. Scanning electron microscopy and transmission electron microscopy were used to determine its morphology and particle size. The Ni-Co-B amorphous catalyst with a Co/(Co+Ni) molar ratio of 0.5 exhibits a much higher activity and selectivity than the Ni-B and Co-B catalysts in the liquid-phase hydrogenation of chloronitrobenzene to chloroaniline. The maximum conversion of both o-chloronitrobenzene and 3,4-dichloronitrobenzene reaches 99.9%, whereas the dechlorinations of chloroaniline are 1.12% and 0.42%, respectively, showing a good potential for industrial applications. The higher activity and selectivity of the Ni-Co-B catalyst can be attributed to the electron donation from the alloying B and metallic Co to the metallic Ni. By following this, the B and Co atoms become electron-deficient whereas the Ni atom becomes electron-rich, which can activate the N=O bond, inhibit the hydrodechlorination of chloronitrobenzene, and increase the thermostability of the amorphous alloy.