Improved hydrogenation process for preparing 4-aminophenol

The process for the production of 4-aminophenol by reducing nitrobenzene with hydrogen in a reaction zone at an elevated temperature and moderate pressure in the presence of aqueous sulfuric acid, a surfactant and a catalyst, is improved by using a platinum on carbon catalyst; utilizing a reaction zone which is not completely filled so that there is both a vapor space and a lower liquid space in the reaction zone and introducing the hydrogen into the vapor space part of said reaction zone; stirring the reaction mixture vigorously using an impeller placed at 40-60% of liquid depth to attain a rate of hydrogenation resulting in a performance index [expressed as grams 4-aminophenol produced per minute per liter of reaction volume] of 0.2 and higher.