Ni-based structured catalyst for selective 3-phase hydrogenation of nitroaromatics

We report herein on the development of Ni-based catalyst using activated carbon fibres (ACFs) as a structured support and its application for the three‐phase hydrogenation of nitroarenes (T = 353 K; P = 10 bar). It was shown that metallic Ni0 nanoparticles (NPs) with a mean diameter of ∼2.0 nm stabilized by the ACF microporous network were responsible for the catalytic transformation. To obtain optimum catalytic activity, the Ni/ACF catalyst must be freshly prepared and activated in situ by H2 at T > 353 K. Pre-treatment of the ACFs by nitric acid boosted the activity of the Ni/ACF catalyst, which exhibits high performance in hydrogenation of nitrobenzene to aniline (yield, Y ∼100%). The catalyst was tested for the reuse attaining a quasi-steady-state after the sixth reaction thereafter remaining relatively stable over seven consecutive runs. Near-quantitative transformation (Y > 99%) of p-chloronitrobenzene to p‐chloroaniline was achieved under mild conditions over the Ni/ACF catalyst with a ca. 20-fold higher activity than conventional Raney Ni. Thus, new catalyst reported here represents a significant step forward towards a simple, heterogeneous catalytic selective hydrogenation of nitroarenes that employs H2 as the hydrogen source.