Hydrogenation of nitrobenzene to p-aminophenol in a four-phase reactor: reaction kinetics and mass transfer effects

The kinetics of catalytic hydrogenation of nitrobenzene in acid medium to p -aminophenol was investigated in a batch slurry reactor in a temperature ra nge of 323-353 It. Aniline was formed as a byproduct (upto 20%). The initia l rate data were analyzed to assess the mass transfer effects and it was fo und that gas-liquid mass transfer resistance was important under certain re action conditions. A Langmuir-Hinshelwood type rate model has been proposed based on the initial rate data in the kinetic regime and considering the r eaction taking place in both organic as well as aqueous phase. Since this w as a four-phase system, the rate equation was suitably modified to include gas-liquid and liquid-liquid mass transfer steps. The kinetic parameters ev aluated from a semibatch reactor model were found to represent the observed experimental data very well indicating the applicability of the proposed r ate model. (C) 2001 Elsevier Science Ltd. All rights reserved.