Process for the separation of high-boiling materials from the reaction mixture generated during the production of diaminotoluene

US5728880A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Heiko Beckhaus · Leverkusen, DE
• Harro Witt · Kuden, DE
• Uwe J. Zarnack · Wittmund, DE
• Gerd Greger · Kempen, DE

Key dates

• Filing date: Feb 25, 1997
• Grant date: Mar 17, 1998
• Expiry date: Feb 25, 2017

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C209/84
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

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.