Study On Catalytic Hydrogenation Of O-Chloronitrobenzene Over Nickel-Based Catalysts

The catalytic hydrogenation technology of o-chloronitrobenzene(o-CNB) in liquid phase is an attractive and elegant routine for the production of o-chloroaniline(o-CAN), owing to the advantages such as high product yield, good product quality and much less pollution to environment. Supported nickel catalysts have been widely used in some hydrogenation processes due to its lower cost, easy availability, ideal catalytic activity and environmental benefit. Up to now, however, few studies about hydrogenation of o-CNB over the supported nickel catalysts have been reported.A series of supported nickel-based catalysts for the liquid-phase catalytic hydrogenation of o-CNB to o-CAN were designed and prepared by the incipient impregnation method. The effects of supports, nickel loadings, calcination temperature, reduction temperature and promoters on the physico-chemical properties of catalysts were investigated by the characterization technologies of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD) and temperature-programmed reduction (TPR), and the reactivity of the catalysts were also evaluated. In addition, the hydrogenation properties of different mono-chloronitrobenzene isomers were investigated.Among the catalysts with the different supports, such as SiO₂, TiO₂, ZrO2 andγ-Al2O3, the TiO₂ supported nickel catalyst showed the highest activity owing to the strong mutual interaction between TiOx and Ni. With the increase in nickel loadings, the active Ni0 species on surfaces increased, and so the conversion of o-CNB increased. When nickel loadings were higher than 30 wt.%, there was no difference in catalytic performance for the catalysts with different nickel loadings.With the increase of calcination temperature for TiO₂ supported nickel catalysts, the mutual interaction between NiO and TiO₂ became stronger and new NiTiO3 phase formed if the calcination temperature was higher than 773 K. The proper amount of NiTiO3 in the catalysts could be beneficial to the dispersion of Ni species, however, too much amount of NiTiO3 could decrease the reducibility of nickel species sharply, which made against the activity of the catalysts. At the too low reduction temperature, the catalysts couldn't be reduced completely, and their activity was lower. However, too higher temperature would cause the sintering of metal nickel crystallites and the...