Abstract:

Mo and La have been independently reported to be good promoters of NiB nanocluster in the hydrogenation of para-chloronitrobenzene (p-CNB). However, a bi-promoter effect of Mo and La in NiB catalysts has not previously been investigated. In this work, a series of La-Mo-doped, nanosized NiB catalysts with different La contents were prepared by chemical reduction and were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The liquid-phase hydrogenation of p-CNB was carried out in a batch reactor at 333 K, 1.2 MPa H₂ pressure and at a spinning rate of 500 r/min. Even doping a small amount of La in NiMoB had a significant effect on its activity and selectivity to p-chloroaniline. The addition of an appropriate amount of La suppressed the growth and long-range order of NiMoB and helped the NiMoB maintain its amorphous state. La was determined to be present in its oxide form and to act as a spacer, preventing NiMoB from sintering and aggregation. However, a high amount of La had an opposite effect, and the optimum ratio of La:Ni was 0.2.

Key words: Nickel, Lanthanum boride, Hydrogenation, Chloronitrobenzene, Chloroaniline