Reduction of Nitrobenzene to Aniline by CO/H2O in the Presence of Palladium Nanoparticles

The transformation of aromatic nitrocompounds into amines by CO/H2O is catalyzed by palladium(II) complexes. Recently, we have proposed that the catalytic cycle includes Pd0 as the transient intermediate and herein, for the first time, we describe the application of palladium nanoparticles (PdNPs) stabilized by monodentate N-heterocyclic ligands as nanocatalysts facilitating the reduction of Ar–NO2 into Ar–NH2 by CO/H2O. Among the series—Pd(II) complexes, PdNPs and commercial Pdblack—the highest catalytic activity was observed for PdNPs (3.0 ± 0.5 nm) stabilized by 4-Me-pyridine in the presence of 2-Cl-pyridine. The results may be helpful for mechanistic considerations on the role of metallic nanoparticles as active species in other organic processes.

Hydrogenation of Aromatic Nitrocompounds on Supported Mono- and Bimetallic Catalysts

<p>Catalytic hydrogenation of substituted aromatic nitrocompounds and hydrocarbons has been studied. It was established that monometallic Pd-catalysts were suitable for reduction of nitrogroups. Bifunctional catalysts such as Rh-Pt, Rh-Pd, Pd-Ru and Rh-Ru were used for hydrogenation of both aromatic ring and nitrogroup and sequence of their hydrogenation depended on support nature. Over Rh-Pt alumina supported catalysts consequent hydrogenation of NO₂ and benzene ring took place, over silica supported catalysts their consecutive hydrogenation was observed. Such catalytic properties of bimetallic Rh-Pt and Rh-Pd catalysts probably connected with metal-metal interaction leading to optimal adsorption strength of uniformly adsorbed hydrogen. The optimal reaction conditions (temperature and hydrogen pressure) have been elaborated for synthesis of alicyclic amines with 95-99% yields.</p>