Covestro Deutschland Ag

Bayer Materialscience Ag

Antoni Mairata

Thomas Knauf

Erik Sluyts

Jan Van Tricht

Bernd Pennemann

Michael Merkel

Alexandre Racoes

Wolfgang Dohmen

Antonia Zock

The invention concerns a method for producing toluenediamine by hydrogenation of dinitrotoluene in the presence of a catalyst, a dinitrotoluene being used as starting material and being processed by applying an electrical voltage.

Method for producing toluenediamine

The present invention provides a process for working up alkaline waste water which is formed during washing of crude nitrobenzene obtained by nitration of benzene, wherein

Process for working up waste water from nitrobenzene preparation

The invention relates to a process for working up alkaline waste water which is formed during washing of crude nitrobenzene obtained by nitration of benzene, wherein

The present invention relates to a continuously operated adiabatic process for the preparation of nitrobenzene by nitration of benzene with nitric acid and sulfuric acid, in which the dilute sulfuric acid obtained after the nitration has taken place and the crude nitrobenzene has been separated off from the aqueous phase is concentrated for the purpose of re-use in the nitration, and after its concentration, at least one minute before it comes into contact with fresh nitric acid again an oxidizing agent is added such that a concentration of the oxidizing agent of from 10 ppm to 5,000 ppm, based on the total weight of the concentrated sulfuric acid to be recycled into the nitration, is established.

Process for the preparation of nitrobenzene by adiabatic nitration

The invention relates to an adiabatic process for producing nitrobenzene by nitrating benzene with sulphuric acid mixtures and nitric acid mixtures using a stoichiometric excess of benzene and reusing non-reacted benzene, the content of the aliphatic organic compounds in the feed benzene being limited, by the targeted evacuation of aliphatic organic compounds to at least one step in the process, to a content of less than 1.5 mass-%, in relation to the total amount of feed benzene.

Method for producing nitrobenzene by adiabatic nitriding

The invention provides a continuous adiabatic process for the preparation of nitrobenzene by nitrating benzene with mixtures of sulfuric and nitric acids using a stoichiometric excess of benzene, wherein the content of organic compounds in the circulating sulfuric acid, at least during the start-up period of the production plant, is always kept below 1.0 mass percent, based on the total mass of circulating sulfuric acid. This is preferably achieved by a procedure in which, either after the end or before the beginning of a production cycle, the circulating sulfuric acid is circulated at elevated temperature so that the organics contained in the sulfuric acid, preferably comprising nitrobenzene and traces of benzene, dinitrobenzene and nitrophenols, are separated off in the evaporation apparatus for concentrating the sulfuric acid.

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Dusseldorf, Germany

Antoni Mairata