Synthesis of p-Aminophenol by Catalytic Hydrogenation of Nitrobenzene
Organic Process Research & Development (Impact Factor: 2.53). 11/1999; 3(6). DOI: 10.1021/op990040r
The present work describes the preparation of p-aminophenol via single-step catalytic hydrogenation of nitrobenzene in acid medium. A conventional method of synthesis of p-aminophenol is a two-step reaction involving iron−acid reduction of p-nitrophenol. This method causes serious effluent disposal problems due to the stoichiometric use of iron−acid, which leads to the formation of Fe−FeO sludge (1.2 kg/kg of product) in the process, which cannot be recycled. The single-step hydrogenation of nitrobenzene was carried out using platinum catalyst, and the process conditions were optimized. Complete conversion of nitrobenzene was achieved with selectivity to p-aminophenol as high as 75% under the best set of conditions. Furthermore, the catalyst can be easily recovered and efficiently recycled giving the TON as high as 1.38 × 10.5 This paper presents studies on the effect of various process parameters such as temperature, hydrogen pressure, and substrate and acid concentration on the rate of reaction and selectivity to p-aminophenol.
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ABSTRACT: The kinetics of catalytic hydrogenation of nitrobenzene in acid medium to p-aminophenol was investigated in a batch slurry reactor in a temperature range of 323–353K. Aniline was formed as a byproduct (upto 20%). The initial rate data were analyzed to assess the mass transfer effects and it was found that gas–liquid mass transfer resistance was important under certain reaction conditions. A Langmuir–Hinshelwood type rate model has been proposed based on the initial rate data in the kinetic regime and considering the reaction taking place in both organic as well as aqueous phase. Since this was a four-phase system, the rate equation was suitably modified to include gas–liquid and liquid–liquid mass transfer steps. The kinetic parameters evaluated from a semibatch reactor model were found to represent the observed experimental data very well indicating the applicability of the proposed rate model.Chemical Engineering Science 02/2001; 56(4):1299-1304. DOI:10.1016/S0009-2509(00)00352-3 · 2.34 Impact Factor
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