Bayer Aktiengesellschaft

Bayer Materialscience Ag

Covestro Deutschland Ag

Gerd Greger

Bernd Pennemann

Heiko Beckhaus

Harro Witt

Bill Brady

Rainer Buse

Uwe-Jens Zarnack

Toluenediamine is produced and separated from by-products of the reaction by:

Process for the preparation of toluenediamine

Amine mixtures generated during the production of diaminotoluene by hydrogenating dinitrated aromatic compounds are treated to separate high boiling materials from the desired amine products. In this process, any water of reaction and any solvent are first removed from the diaminotoluene isomer mixture (TDA mixture). The low-boiling TDA isomers are then separated using a TDA isomer distillation column. In the process of the present invention, the bottom phase remaining after the initial distillation contains a mixture of m-TDA and high-boiling materials. This bottom phase is separated and concentrated until the high-boiling material content is from approximately 25 to 60 wt. %. This concentrated bottom phase is then mixed with o-TDA in a ratio of 1:1 to 1:5 and a m-/o-TDA mixture is removed by distillation. The m-/o-TDA mixture thus recovered is then returned to the TDA isomer distillation column.

Process for the separation of high-boiling materials from the reaction

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Kempen, Germany

Gerd Greger