Method for producing diaminotoluene

A continuous process for preparing toluenediamine by hydrogenation of dinitrotoluene in the gas phase, comprising:

• (I) spraying of a dinitrotoluene-comprising stream into a hydrogen-containing carrier gas stream in a vaporization apparatus, where
• a) the temperature of the dinitrotoluene-comprising stream is from 70° C. to 150° C. and the temperature of the hydrogen-containing carrier gas stream is from 140° C. to 300° C.,
• b) the absolute pressure of the dinitrotoluene-comprising stream is from 3.0 bar to 30 bar and the absolute pressure of the hydrogen-containing carrier gas stream is from 1.0 bar to 10 bar, where the pressure of the dinitrotoluene-comprising stream is higher than that of the hydrogen-containing carrier gas stream, and
• c) the molar ratio of hydrogen to dinitrotoluene is from 6.0:1 to 900:1.
• so as to give a stream comprising dinitrotoluene and hydrogen;
• (II) removing or targetedly decomposing the liquid droplets present in the stream comprising dinitrotoluene and hydrogen from step (I) to give a gas stream which comprises dinitrotoluene and hydrogen and has been depleted in liquid droplets;
• (III) reacting the dinitrotoluene present in the gas stream which comprises dinitrotoluene and hydrogen and has been depleted in liquid droplets with hydrogen in at least one reaction space in the presence of a catalyst at an absolute pressure of from 1.0 bar to 10 bar, a temperature of from 140° C. to 300° C. and a residence time in the reaction space of from 0.1 s to 10 s, so as to give a toluenediamine-containing gas stream,
• (IV) separating the toluenediamine-containing gas stream obtained in step (III) after passing through the last reaction space into a toluenediamine-comprising liquid phase and a hydrogen-comprising gas phase by condensation;
• and
• (V) recirculating at least part of the hydrogen-comprising gas phase obtained in step (IV) into the first vaporization apparatus of step (I).