Preparation of NiFeB Nanoalloy Catalysts and Their Applications in Liquid-Phase Hydrogenation of p-Chloronitrobenzene.

A series of NiFeB nanoalloy catalysts were prepared by chemical reduction method using metal acetates as the starting materials, and NaBH4as the reducing agent. The amorphous metal materials, combining the features of amorphous and nanometer materials, have more surface atoms and a higher concentration of coordinately highly unsaturated sites. Sodium borohydride in excess amount was added dropwise into the mixture to ensure full reduction of metal cations. The catalysts were characterized with X-ray diffraction, nitrogen sorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. The hydrogenation of p-chloronitrobenzene was carried out in a batch reactor at 1.2 MPa H2pressure and 323−393 K. The Ni/Fe molar ratios in the starting materials affected the concentration of boron bounded to the nickel and iron metals, resulting in the difference in surface area, electronic structures of the metals, and the catalytic activities of the catalysts. The addition of iron in NiB catalyst could reduce the particle of the nickel metal, suppress the growth of crystalline structure of NiFeB, and help the NiFeB catalyst to maintain its amorphous state. On the basis of the electron transfer between elemental nickel and boron, Ni in NiFeB had more d-band electrons and higher electron density than in NiB; therefore, it also has higher activities of hydrogenation of the nitro group than does NiB. [ABSTRACT FROM AUTHOR]