Hydrogenation of p-Chloronitrobenzene on Lanthanum-Promoted NiB Nanometal Catalysts

Amorphous nanosized NiB catalysts have been reported to be a good catalyst for the liquid-phase hydrogenation of chloronitrobenzene. This study was conducted to investigate the effect of lanthanum on the catalytic properties of the NiB catalyst in the liquid-phase hydrogenation of p-chloronitrobenzene (p-CNB). The lanthanum-promoted NiB catalyst was prepared via the liquid-phase reduction of nickel cations by borohydride. The atomic ratio of boron to nickel in the mother solution was B/Ni = 3:1. The catalysts were characterized by N2 sorption, powder X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Liquid-phase hydrogenation of p-CNB was performed in a well-stirred, high-pressure batch reactor system. The catalysts prepared in this study had nanosized particles. La-NiB was much more active than NiB and the Raney nickel catalyst. The selectivity of the main product (p-chloroaniline, p-CAN) was >99% on La-NiB catalysts. However, excess amounts of lanthanum caused a decrease in the activity. The effect of the lanthanum promoter can be attributed to the electronic modification of nickel by lanthanum.