Nitrobenzene hydrogenation on Ni-P, Ni-B and Ni-P-B ultrafine materials

A series of ultafine Ni-P, Ni-B and Ni-P-B amorphous alloy catalysts with various atomic ratios was prepared by a chemical reduction method. The catalysts were characterized with respect to nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS) and hydrogenation activity. Conventional Raney nickel was included for comparison. The Ni/P/B molar ratios in the starting materials significantly affects the concentration of boron and phosphorus bonded to the nickel metal, subsequently affecting the surface area, amorphous structure and hydrogenation activity of the catalysts. The prepared catalyst, although easily degraded by gaseous oxygen, did not ignite in the atmosphere due to the passivation by phosphorus and boron. The hydrogenation of nitrobenzene to aniline catalyzed actively by the Ni-P-B, Ni-B and Ni-P amorphous alloy catalysts, following the zeroth order with respect to nitrobenzene and first order with respect to hydrogen kinetics. The specific activities per surface area catalyst are in the following order: Ni_85.0P_15.0>Ni_74.5P_12.1B_13.4> Ni_72.5P_2.0B_25.5 >Ni_71.4B_28.9>Ni_78.5P_6.0B_15.5 > Raney nickel. The modified nickel catalysts by the different electron transference, boron donates electrons to nickel and phosphorus draws electrons from nickel, depending on the different function groups of the reaction compounds, dramatically reveals a markedly different property of catalysis. By regulating the suitable P/B ratios, the ultrafine Ni-P-B amorphous alloy catalysts can be a very effective catalyst for the various liquid phase hydrogenation reaction than Raney nickel. (C) 2000 Elsevier Science B.V.