Monitoring of the stoichiometric ratio in the reaction of nitroaromatics with hydrogen

A continuous process for preparing at least one aromatic amine by hydrogenation of at least one nitroaromatic by means of hydrogen, where a liquid phase comprising at least the aromatic amine and a gas phase comprising at least hydrogen are present, in the presence of a catalyst suspended in the liquid phase at a temperature of from 50 to 250° C. and a pressure of from 5 to 50 bar, wherein

• the pressure in the reactor is kept essentially constant by continuous adaptation of the amount of hydrogen fed to the reactor,
• the total amount of hydrogen fed to the reactor is monitored and
• the introduction of the at least one nitroaromatic is interrupted if the hydrogen uptake in the reactor is not at least 50 mol %, preferably at least 70 mol %, particularly preferably at least 90 mol %, very particularly preferably at least 95 mol %, in particular at least 98 mol %, of the amount of hydrogen required for stoichiometric reaction of the at least one nitroaromatic to form the at least one aromatic amine.