Hydrogenation of nitrobenzene to 4-aminophenol in a fully reusable solvent system, by using Pt, Rh, Pd supported on carbon-CF3COOH catalytic system

4-Aminophenol is an important raw material for several products in the field of dyes, photographs and pharmaceutics. For instance, paracetamol (N-acetyl-4-aminophenol) a widely employed analgesic and antipyretic whose production is in continuous growth specially in the far east region. Industrial synthesis of paracetamol is based mainly on 4-aminophenol, which is obtained by three different routes: i) nucleophilic substitution of the Cl of the 4-chloronitrobenzene, ii) reduction of 4-nitro-phenol, iii) selective hydrogenation of nitrobenzene [1]. The selective hydrogenation of nitrobenzene is however, the most convenient from both economical and environmental point of view [1, 2]. The major concern of this process is, however, the presence of H2SO4, which is origin of corrosion, safety, environmental and separation problems. The reaction is typically carried out in CSTR in which the biphasic reaction medium is used to accomplish simultaneously the Pt catalyzed hydrogenation of nitrobenzene and the acid catalyzed Bamberger rearrangement of the intermediate N-phenylhydroxylamine. From environmental point of view, the major drawback of the process is the neutralization of the acidic phase, with the consequent by-production of sulfate salts, which are undesired wastes. Starting from recent results obtained in the Beckmann rearrangement of the cyclohexanone oxime in CH3CN-CF3COOH system [3], here we show some findings on the hydrogenation of nitrobenzene to 4-aminophenol in a single liquid phase CH3CN-H2O-CF3COOH and in the presence a hydrogenation catalyst. The easy of recovery of solvent and catalysts allows to develop a greener process than that based on the biphasic H2SO4-nitrobenzene system