Study On Reaction And Kinetics For Synthesis Of P-Aminophenol From Nitrobenzene Hydrogenation

As compared with the traditional processes of p-aminophenol from cholobenzene via three-step reaction of nitration and hydrolysis and reduction, the one-pot method for the preparation of p-aminophenol via hydroxylbenzeneamine precursor by Bamberge rearrangement from nitrobenzene in the presence of Pt/C catalyst appears of the atom economy towards an promising industrialization.For the industrial preparation of p-aminophenol from nitrobenzene with catalytic hydrogenation it is necessary to resolve the three main problems, which are engineering scale-up for four-phase involving hydrogen gas phase, nitrobenzene organic phase, sulfuric acid inorganic phase and Pt/C solid phase, a well-mixed reactor design as well as the macro-kinetics in engineering. The catalyst for noble metal Pt supported C could be met the economic demand on theoretical and practical resolutions for the catalyst activity and the catalytic reaction kinetics. Besides, the reactor equipment resistance to the dilute sulfuric acid corrosion must be selected.A Venturi mixer of vortex self-induction was employed to increase the rotating speed progressively by using frequency conversion equipment, since the rate could be increased correspondingly to a stable value so as to eliminate the exterior dispersion resistance from every phase. And with the decreasing the particle diameter progressively by a screening grading the rate was also increased correspondingly to a constant so that the interior dispersion resistance over the catalyst could be eliminated. The maintenance in constant concentration of nitrobenzene without the resistance from the interior and exterior dispersions the formation rate of p-aminophenol and aniline was varied with the hydrogen pressure and the reaction order could be obtained with an integration method. Moreover, the activation energy for the reaction can be obtained using the Arrenius equation by the formation rate of p-aminophenol and aniline with temperature variation.The catalyst efficacy was decreased with the increasing recycle times. The order for the catalyst deactivation rate can be obtained using the simple expression (SPLE) model proposed by Leivenspill fitting the experiment date. The activation energy for the deactivation was obtained by the Arrenius equation.Moreover, the four phase macro-kinetics for the formation of p-aminophenol and aniline by the selective catalytic hydrogenation of nitrobenzene without any resistance from the interior and exterior dispersion of catalyst, and deactivation kinetics for the Pt/C catalyst with the catalyst recycles were established. A plausible mechanism for the selective formation of p-aminophenol and aniline over Pt/C catalyst was suggested. The methodology for the preparation of Pt/C catalyst was developed to meet environmentally economic demand. Various technological parameters involving the Hastalloy resistant to the corrosion of the dilute sulfuric acid, the design for hydrogenation reactor for the four phases and the industrial scale experiment were discussed towards industrialization.Therefore, three novel results have been achived in this paper. The first is the four phase macrokinetics for the formation of p-aminophenol and aniline by the selective catalytic hydrogenation of nitrobenzene. The second is the deactivation kinetics for the Pt/C catalyst with the catalytic recycles. The third is the design for hydrogenation reactor for the four phases via successful industrial scale experiment.