Liquid-phase hydrogenation of chloronitrobenzene to chloroaniline over Ni-Co-B amorphous alloy catalyst

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 chloronitrobenze to chtoroaniline. The maximum conversion of both o-chloronitrobenzene and 3,4-dichtoronitrobenzene reaches 99.9%, whereas the dechlorination of chloroaniline was 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. Following this, the B and Co atoms become electron-deficient whereas the Ni atom becomes electron-enriched, which can activate the N=O bond, inhibit the hydrodechlorination of chloronitrobenzene, and increase the thermostability of the amorphous alloy.