Patent ID: 8030522

Claim:
A process for the production of toluene diisocyanate comprising: a) hydrogenating dinitrotoluene at temperatures of from 120 to 180° C. under 20 to 40 bar hydrogen pressure and at 0.5 to 4 hours dwell time, in the presence of a catalyst which is selected from the group consisting of doped or undoped Raney nickel catalysts, doped or undoped nickel catalysts fixed to a support and noble metal catalysts fixed to a support and loaded with one or more noble metals, to yield a crude toluenediamine mixture, b) purifying the crude toluenediamine mixture in a multi-stage distillation, which comprises a stage in which the high boilers and cyclic ketones are separated off with the aid of a distillation column comprising an evaporator, a condenser and a stripping section, said stripping section having at least 3 theoretical plates, wherein said distillation column is operated at absolute head pressures of from 50 to 2000 mbar and at head temperatures of from 140 to 320° C., to yield a toluenediamine which contains a total of less than 0.1% by weight of cyclic ketones, based on 100% by weight of the toluenediamine, and c) phosgenating the toluenediamine which contains a total of less than 0.1% by weight of cyclic ketones, based on 100% by weight of the toluenediamine, to yield the toluene diisocyanate.