Bayer Materialscience Ag

Bayer Aktiengesellschaft

Covestro Deutschland Ag

Bayer Intellectual Property Gmbh

Jürgen Münnig

Berthold Keggenhoff

Wolfgang Lorenz

Dietmar Wastian

Thomas Knauf

Bernd Pennemann

Friedhelm Steffens

Michael Merkel

Andreas Karl Rausch

Peter Lehner

Joachim Ritter

Dieter Grenner

Heiko Beckhaus

Manfred Keller-Killewald

Rainer Buse

Erwin Dieterich

Anke Hielscher

Heinrich Lokum

Jörg Schmiedler

Denise Chan

Joerg Schmiedler

Wulf Dietrich

Andreas Rausch

The invention relates to a method for producing dinitrotoluene, comprising the following steps: a) nitrating toluene with a mixture of nitric acid and sulfuric acid and subsequently separating a sulfuric-acid-containing aqueous phase that arises in the nitration, wherein a raw dinitrotoluene is obtained, b) washing the raw dinitrotoluene in a water wash with neutral and/or alkaline washing water, wherein a pre-cleaned dinitrotoluene, which contains at least water in addition to dinitrotoluene, is obtained after the washing water used in the last wash has been separated, and c) separating the water from the pre-cleaned dinitrotoluene, d) collecting the waste water from steps a), b), and/or c), e) optionally extracting the collected waste water from step d) with toluene and returning the thus obtained organic phase to step a), f) freeing the collected waste water from step d), or, if the optional step e) is performed, the extracted waste water from step e), of toluene in a toluene stripper, wherein a toluene-containing exhaust gas flow is obtained, g) feeding at least one exhaust gas flow from steps a), b), c), d), e), or f) into an exhaust gas condenser and removing the toluene contained in the at least one exhaust gas flow in said exhaust gas condenser, wherein the method comprises the following further step: h) feeding the exhaust gas flow arising in step g) after the condensing out of the toluene to a thermal exhaust air cleaning, wherein nitrogen is added to the exhaust gas flow to be fed to the exhaust gas condenser or to the exhaust gas flow leaving the exhaust gas condenser, wherein preferably a nitrogen concentration in the exhaust gas flow of at least 0.1 vol % is set, especially preferably of at least 0.5 vol %.

Exhaust gas cleaning in a method for continuously producing dinitrotoluene

The present invention relates to a method for producing nitrobenzene, in which the waste gas streams accruing in the process and containing benzene and (traces of) nitrobenzene, possibly low- and medium-boiling components, possibly non-condensable gases and possibly water, optionally after removal of nitrogen oxides, are scrubbed in an absorption column with nitrobenzene, which comprises only very small amounts (maximum 50 ppm) of benzene and is distributed by means of a liquid distributor at a rate of 50 to 200 drip points per square meter, preferably 60 to 120 drip points per square meter, wherein (i) a liquid stream containing benzene and nitrobenzene, possibly organic low- and medium-boiling components and additionally containing sulfuric acid if sulfuric acid is used as the scrubbing agent and (ii) waste gas depleted in benzene and possibly in organic low- and medium-boiling components are obtained. A waste gas purified by the method according to the invention is particularly suitable for burning in a thermal exhaust air treatment process.

Method for the continuous production of nitrobenzene

Nitrobenzene is continuously produced by nitration of benzene with mixed acid under adiabatic conditions. In this process, the pressure upstream of the nitration reactor is from 14 bar to 40 bar above the pressure in the gas phase of the phase separation apparatus used to separate crude nitrobenzene and waste acid.

Process for the continuous preparation of nitrobenzene

The invention relates to a process for the production of phosgene, in which chlorine and carbon monoxide are reacted in the presence of an activated charcoal catalyst in a shell-and-tube reactor which contains a plurality of reaction tubes and a coolant space surrounding the reaction tubes, in which

Process and apparatus for the production of phosgene

The invention describes a stirring device made from a gassing stirrer and a liquid mixer or two liquid mixers, which are arranged on a shaft and each have a feed and at least one exit opening, wherein the exit openings of the gassing stirrer and of the liquid mixer or the liquid mixers are at a distance from one another, the ratio, a/d, of the distance, a, between the exit openings to the diameter, d, of the gassing stirrer or liquid mixer being 0.02 to 0.5 and the ratio, b/d, of the distance, b, between the outer edges to the diameter, d, of the gassing stirrer or liquid mixer being 0.01 to 0.4.

Stirring device and process for carrying out a gas-liquid reaction

The invention relates to a process for the production of dinitrotoluene by the two-stage nitration of toluene. In the first stage of this process, toluene was reacted adiabatically with nitrating acid so that at least 90% of the toluene was reacted off and no more than 70% of the toluene formed dinitrotoluene. The resulting organic phase containing mononitrotoluene and the aqueous acid phase containing sulfuric acid were separated, and the aqueous acid phase containing sulfuric acid was concentrated by flash evaporation. The resulting concentrated sulfuric acid was recycled into the reaction in the first stage, and/or into the reaction in the second stage, and/or into the concentration in the second stage. In the second stage, the organic phase containing mononitrotoluene from the first stage was completely reacted isothermally with nitrating acid. The organic phase and the aqueous acid phase containing sulfuric acid were then separated, and the aqueous acid phase containing sulfuric acid was concentrated by vacuum evaporation. The resulting concentrated sulfuric acid was recycled into the reaction in the first stage and/or the second stage.

Process for the two-step production of dinitrotoluene

The present invention relates to a process for working up organic secondary components which are formed in the one-stage or two-stage nitration of toluene to dinitrotoluene. These organic secondary components are present in the acidic and alkaline waste water from the dinitrotoluene washing step and in the aqueous distillate from the sulfuric acid concentration step, together with small amounts of mononitrotoluene and dinitrotoluene. This process comprises

Process for working up secondary components in the preparation of dinitrotoluene

The present invention relates to a process for working up or treating aqueous waste waters which are formed during the nitration of toluene to dinitrotoluene with nitrating acid. These aqueous waste waters containing acidic wash water and alkaline wash water from the dinitrotoluene washing step, and distillate from the sulfuric acid concentration step. The process comprises,

Process for working up the waste water obtained in the preparation of dinitrotoluene

A process is provided for the purification of sulfuric acid contaminated with impurities, such as nitric acid, nitrosylsulfuric acid, dinitrotoluenes and mononitrotoluenes, wherein this contaminated sulfuric acid was obtained from the production of nitrated toluene using toluene and nitric acid. The contaminated sulfuric acid is preheated to a temperature in the range of 50 to 180.degree. C. in a heat exchanger. The heated, contaminated sulfuric acid is freed from steam-volatile impurities, such as dinitrotoluenes and mononitrotoluenes, and the nitrogen-containing compounds within the sulfuric acid are decomposed by counter currently contacting the contaminated sulfuric acid with steam and vapors from a downstream concentration step in a steam stripper, which is operated at a pressure ranging from 300 to 1,000 mbars. The steam-stripped sulfuric acid is fed into a first concentration stage, which is operated at the same pressure used in the steam stripper. The concentrated sulfur acid is then fed into a vacuum concentration process which produces a sulfuric acid having a concentration of 88 to 97 percent by weight. By using the same pressure that the steam stripper operates at in the first concentration stage, the crystallization of nitroaromatic compounds can be avoided in the condensation system of the concentration stages, along with the concomitant blockage of the condensation system that would have been caused by the crystals.

Process for purifying and concentrating spent sulfuric acids

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Kaarst, Germany

Jürgen Münnig