Bayer Aktiengesellschaft

Harro Witt

Heiko Beckhaus

Dieter Becher

Uwe J Zarnack

Gunter Lailach

Udo Birkenstock

Rudolf Gerken

Hermann Dallmeyer

Eckart Waldau

Gerd Greger

Uwe-Jens Zarnack

Peter Klein

Sludge phase reactor and process for performing sludge phase reactions

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

Sulphuric and nitric acids present in dinitrotoluene are separated from the dinitrotoluene by adding up to 10 wt. % water (based on quantity of dinitrotoluene) to the mixture of dinitrotoluene, sulphuric acid and nitric acid, mixing and separating the aqueous phase containing nitric and sulphuric acids. The mixtures treated by this process generally contain up to 5 wt. % nitric acid and up to 6 wt. % sulphuric acid.

Process for separating sulphuric acid and nitric acid from

A Pauling boiler for the concentration of sulphuric acid, wherein the external surface of the Pauling boiler is coated with aluminum. A process for the concentration of sulphuric acid in Pauling boilers by underfiring with gas or liquid fuels, wherein the concentration is carried out in a Pauling boiler coated with aluminum.

Pauling boiler and process for the concentration of sulphuric acid

Aromatic diamino compounds are produced by hydrogenating the corresponding dinitro compounds in the presence of a modified Raney catalyst. The modified Raney catalyst is obtained by treating an alloy made up of 50-95 wt % of aluminum, 4-45 wt % nickel and/or cobalt and 1-46 wt % of at least one modifying metal with an alkali material. The modifying metal is selected from the metals of the first, fourth, fifth, sixth, seventh and eighth subgroups of the Periodic Table of Elements. The hydrogenation is preferably carried out at from 170.degree. to 250.degree. C. and a pressure of 15-50 bar. The heat generated during hydrogenation is preferably used to produce steam.

Production of aromatic diamino compounds using a modified Raney catalyst

An amine is separated from an aqueous solution of amine and volatile organic compounds by distillation in a column. The vapors generated during distillation are condensed. The condensed vapors are then passed into a separating device in which the volatile organic compounds are removed. The liquid remaining in the separating device is then fed to the head of the distillation column. Water is removed from the column in a sidestream and diamine is the residue. This process is particularly effective in recovering aromatic diamines from solutions which accumulate during hydrogenation of dinitro aromatic compounds.

Process for working-up aqueous amine solutions

In the production of dinitrotoluene by a two-stage reaction of toluene with nitric acid in the presence of sulphuric acid, wherein toluene is nitrated to mononitrotoluene in the first stage using spent acid from the second stage, and the mononitrotoluene is nitrated to dinitrotoluene in the second stage using concentrated spent acid from the first stage, the improvement which comprises concentrating spent acid under vacuum in an indirectly-heated evaporator and feeding mononitrotoluene into the superheated vapor of the evaporator.

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Kuden, Germany

Harro Witt