Study Of Reducing Nitrobenzene To P-aminophenol

This paper prepares p-aminophenol by selective catalytic hydrogenation of nitrobenzene and two-step synthesis method which including reducing by Zinc powder and rearrangement of phenylhydroxylamine. The two methods in this paper are compared to seek the optimum reaction conditions.The synthesis of p-aminophenol by selective of nitrobenzene is studied in the laboratory,using5%Pt/C as catalyst, CTAB as surfactant and adding an organic solvent which can be miscible with sulfuric acid to the reaction solution in the experiment. Effects of some key parameters such as reaction temperature, pressure of hydrogen, concentration of sulfuric acid, types and usage of additives and the amount of catalyst are investigated. The optimum condition is as follow:nitrobenzene2.00g,17.5%sulfuric acid33.3ml, reaction temperature80°C, pressure of hydrogen0.3Mpa, CTAB0.03g, methanol0.5g,5%Pt/C O.lOg; In this condition, the yield of the aminophenol is75.60%. This paper also studies the recycling of the catalyst which can reduce production costs.For the two-step preparation of aminophenol, this paper applies the traditional method which involves using zinc as catalyst to restore nitrobenzene to phenylhydroxylamine under weak acidic conditions. Then phenylhydroxylamine happens Bambergre-arranged reaction to prepare p-aminophenol under acidic conditions which is the second important content of this paper. In this part of the experiment, the synthesis of p-aminophenol by rearrangement of phenylhydroxylamine which uses a homemade zirconia solid acid as catalyst and deionized water as a solvent and an organic solvent as an addition is investigated. Effects of some key parameters are investigated. The optimum condition is as follow:phenylhydroxylamine0.109g, deionized water7ml, SO42-/ZrO20.2g, reaction time2.5h, reaction temperature80°C, the yield of p-aminophenol is up to81.45%, In addition, the rearrangement reaction of phenylhydroxylamine on the inorganic acid is discussed, compared with the rearrangement reaction of phenylhydroxylamine on solid acid, founding that the rearrangement reaction on a homemade solid acid is superior to the rearrangement reaction on the inorganic acid.