A series of poly-N-vinylpyrrolidone (PVP)-modified NiCoB catalysts with various PVP contents were prepared by chemical reduction method. The Ni and Co cations were reduced by NaBH(4) at room temperature. PVP was added during preparation. The materials were characterized by X-ray diffraction, transmission electron microscopy, and differential scanning calorimeter. The results showed that all samples possessed amorphous structure. After washing, the residual PVP adsorbed on the surface of NiCoB and acted as a spacer to prevent NiCoB particles from aggregation and agglomeration. The liquid-phase hydrogenation of p-chloronitrobenzene was carried out to investigate the catalytic properties of the PVP-modified NiCoB catalysts. The catalytic activities of NiCoB catalysts decreased by modifying with PVP but the selectivities for p-chloroaniline improved significantly. The competitive adsorption of PVP with p-chloronitrobenzene and p-chloroaniline on the NiCoB nanoparticles was responsible for the catalytic performance. The amount of the PVP played a key role in the hydrogenation reaction. (C) 2010 Elsevier B.V. All rights reserved.
