| dc.description.abstract | NiB alloy catalyst has been reported to be a good catalyst for the hydrogenation of p-chloronitrobenzene to p-chloroaniline. The objective of this study was to investigate the effects of Mo and Pd contents on the catalytic properties of NiB in the hydrogenation of p-chloronitrobenzene. A series of NiB catalysts with various modifiers (Mo, and Pd) were prepared by chemical reduction method using NaBH4 as the reducing agent at 298 K. The catalysts were characterized by inductively coupled plasma-mass spectrometry, X–ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive spectrometer, and X-ray photoelectron spectroscopy. The catalytic properties of these catalysts for p–chloronitrobenzene (p-CNB) hydrogenation were studied. Adding proper content of modifiers improved the activity, selectivity and thermal stability of NiB. Both of the modified catalysts Mo-NiB and Pd-NiB processed amorphous structure. The Pd and Mo acted as the spacer to prevent the NiB particles from aggregation, so the particle sizes of the modified catalysts were less than that of the unmodified NiB catalysts. Furthermore, the Magnetization of ultrafine particles remarkably increase with doping Pd into NiB. XPS results showed that molybdenum modifier existed both in elemental and oxidized states. Different modifiers had various effects on the surface composition of NiB catalyst. The elemental state of modifier( Mo and Pd) formed nano-alloy with Ni and affected their electron densities which influenced the products distributions (the relative contents of p–chloronitrobenzene, aniline, and nitrobenzene) in the p-CNB hydrogenation. The life time tests NiB and Mo-NiB were also studied. The results showed that Mo additive could extend the life of NiB. After the hydrogenation reaction, the NiB catalyst sintered to numerous large grains. However, Mo-NiB retained the original black nano-clusters and the catalytic activities were maintained at high level after 3 batch runs. These effects were responsible for the different behaviors of Mo-, and Pd-modified NiB catalysts in the p-CNB hydrogenation.
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