Bayer Aktiengesellschaft

Jurgen Zimmermann

Gerhard Wiechers

Thomas Schieb

Uwe Klingler

Nitroaromatic compounds are produced by continuously reacting an aromatic compound with nitrating acid. The reaction mixture is separated into an organic phase from which the desired nitroaromatic compound is recovered and an acid phase. The acid phase is subjected to flash evaporation to remove at least 5% by weight of the water present therein. The vapors generated during the flash evaporation are introduced into a jet spray of coolant to produce a condensate made up coolant, condensed vapors and suspended organic compounds. A portion of the condensate is subjected to phase separation to remove water and organic compounds present therein. The water and organic compounds may be reused. The process of the present invention is particularly advantageous in that deposits which block pipelines and interfere with heat transfer are not generated.

Process for the production of nitroaromatic compounds

Dinitrotoluene is produced from toluene and nitric acid in the presence of sulfuric acid in a two stage process in the first stage, toluene and nitric acid are reacted under isothermal conditions in amounts such that mononitrotoluene is produced. The reaction mixture is then separated into an organic phase and an acid phase. The organic phase is then further reacted with nitric acid under adiabatic conditions to produce dinitrotoluene. The reaction mixture is then separated into an organic phase and an acid phase. Dinitrotoluene is recovered from the organic phase. After at least 5% by weight water is removed from the acid phase and sufficient nitric acid to replace that consumed during the nitration reaction has been added, the acid phase may be recycled.

Process for the production of dinitrotoluene

Dinitrotoluene is produced in a two-stage process from toluene and nitric acid in the presence of sulfuric acid under adiabatic conditions in the presence of nitrating acids made up of specified components. The reaction product of the first phase is separated into an acid phase and an organic phase containing the mononitrotoluene. Some water is removed from the acid phase, nitric acid is added and the resultant mixture is recycled. The organic phase containing mononitrotoluene is further nitrated to produce the dinitrotoluene. This nitration mixture is also separated into an acid phase and an organic phase. The acid phase is treated to remove some water, nitric acid is added and the resultant acid mixture is recycled. Dinitrotoluene is recovered from the organic phase. This process is advantageous in that dilute nitric acid may be used and the heat of the nitration reaction is utilized.

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Walnut Creek, CA, United States of America

Jurgen Zimmermann