Selective Hydrogenation of Halonitrobenzenes

Many effective strategies have been developed in order to inhibit the hydrodehalogenation in the selective hydrogenation of halonitrobenzene to haloaniline. However, hydrogenolysis of the carbon-halogen bond of the produced haloaniline as a defect of the hydrogenation process could not be avoided completely over usual metal catalysts, especially at complete conversion of the substrates. In the past few years, we reported that over platinum/iron-oxide nanocomposite catalysts, the hydrodehalogenation of haloanilines was completely suppressed even at complete conversion of halonitrobenzene. Investigation by FTIR-CO probe and XPS revealed the electron transfer from Pt nanoparticles to oxygen vacancies in the activated Pt/γ-Fe2O3 catalysts, which may play an important role in completely suppressing the hydrodehalogenation of haloanilines in the hydrogenation reactions. In this review, we deal with the great efforts and remarkable contributions of different authors during the long exploration for the solutions of this hard obstacle. Stress is placed on supported metal catalysts and polymer-protected metal nanoclusters or colloid catalysts.