Patent ID: 8609899
Filing Date: 2013-12-17
Classification: C07C

Abstract:
1. A process for the continuous preparation of toluenediamine by liquid-phase hydrogenation of dinitrotoluene by means of hydrogen in the presence of a suspended, nickel-comprising catalyst in a reactor with a product isolation unit downstream of the reactor to give a product output from the reactor comprising a liquid phase comprising toluenediamine and dinitrotoluene, in which the nickel-comprising catalyst is suspended, wherein the concentration of dinitrotoluene in the liquid phase of the product output from the reactor in the region between the reactor and the downstream product isolation unit is set to a value in the range from 1 to 200 ppm by weight, based on the total weight of the liquid phase of the product output from the reactor, wherein the setting of the dinitrotoluene concentration in the liquid product output from the reactor in the region between the reactor and the downstream product isolation unit is carried out on the basis of a repeated measurement of the dinitrotoluene concentration in the liquid product output from the reactor at time intervals of ≦24 hours.