Basf Se Corporation

Verein Für Kernverfahrenstechnik Und Analytik Rossendorf E.v.

Stefanie Haase

Andreas Raichle

Ulrich Penzel

Samuel Neto

Michael Zoellinger

Johannes Buettner

Holgar Braunsberg

Joana Coelho Tsou

Holger Allardt

Steffen Oehlenschlaeger

Anne-Kathrin Merten

Reiner Reetz

Rüdiger Fritz

Sandra Mühlbeyer

Michael Zöllinger

Johannes Büttner

Olaf Wiedenhoff

Alexander Schocker

Dusko Kadijevic

Steffen Oehlenschläger

Urlich Penzel

A process for preparing aromatic amines by hydrogenation of nitroaromatics in the presence of catalysts, forming a fluid, amine-comprising reaction mixture in a reactor, wherein chromatographic analysis of the reaction mixture is carried out to determine the concentration of nitro and nitroso compounds in the reaction mixture.

Process for preparing aromatic amines

The present invention relates to a continuous process for preparing at least one aromatic amine by hydrogenation of at least one nitroaromatic by means of hydrogen, where a liquid phase comprising at least the aromatic amine and a gas phase comprising at least hydrogen are present, in the presence of a catalyst suspended in the liquid phase at a temperature of from 50 to 250&#xb0; C. and a pressure of from 5 to 50 bar, wherein the pressure in the reactor is kept essentially constant by continuous adaptation of the amount of hydrogen fed to the reactor, the total amount of hydrogen fed to the reactor is monitored and the introduction of the at least one nitroaromatic is interrupted if the hydrogen uptake in the reactor is not at least 50 mol % of the amount of hydrogen required for stoichiometric reaction of the at least one nitroaromatic to form the at least one aromatic amine.

Monitoring of the stoichiometric ratio in the reaction of nitroaromatics with hydrogen

Precipitations of nitrohydroxyaromatic salts out of the nitrated crude products obtained in the nitration of aromatic compounds after alkaline scrubbing, for example mononitrotoluenes, are prevented by contacting the nitrated crude products with an acidic ion exchanger. The nitrated crude products are preferably selected from a feedstream to a distillation column, a bottoms circulation stream of a distillation column and a feedstream to a vaporizer.

Prevention of precipitation from nitrated aromatic crude products

The invention relates to 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.

Process for preparing toluenediamine by hydrogenation of dinitrotoluene

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Bretnig-Hauswalde, Germany

Stefanie Haase