Bayer Aktiengesellschaft

Uwe Klingler

Thomas Schieb

Gerhard Wiechers

Jurgen Zimmermann

Dietmar Wastian

Hans-Georg Pirkl

Reinhard Schom Acker

J&uuml;rgen Zimmerman

J Urgen Zimmermann

Dinitrotoluene (DNT) is produced by the adiabatic nitration of toluene with nitric acid at a temperature of from about 60 to about 200&deg; C. and at a molar ratio of toluene to nitric acid of from about 1:1.5 to about 1:3.0. The reaction mixture thus-obtained is concentrated to a water content of up to 30% by weight. The dinitrotoluene which is present in the reaction mixture is at least partially (if not completely) removed from the reaction mixture either before or after concentration of the reaction mixture. The DNT which is still present in the vapor generated during the concentration of the reaction mixture is kept liquid by the addition of a solvent to the vapors generated during concentration of the reaction mixture. The solvent added to vapor, together with any DNT present in the vapor is recovered. This solvent/DNT mixture may be recycled directly to the reaction vessel. The solvent/DNT mixture may also be separated. The separated solvent may be recycled to the solvent addition step. The separated DNT may be combined with the recovered DNT product or it may be recycled to the nitration reaction mixture.

Adiabatic process for producing dinitrotoluene

Dinitrotoluene is produced by nitrating toluene with nitrating acid under adiabatic conditions in a manner such that some mononitrotoluene is present in reaction mixture. The nitration reaction mixture is then treated to remove at least 5% by weight of water before the reaction mixture is separated into an acid phase and an organic phase. The product dinitrotoluene is recovered from the organic phase. The acid phase may be recycled after nitric acid has been added to replace that which was used in the nitration reaction.

Process for the production of dinitrotoluene

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.

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.

Dinitrotoluene and isomer mixtures of dinitrotoluene are produced in a single stage, continuous process by nitrating mononitrotoluene or an isomer mixture of mononitrotoluene in which the ortho-mononitrotoluene content is low with a nitrating acid made up of (1) from about 80 to about 100 wt. % inorganic constituents and (2) up to 20 wt. % organic constituents. The inorganic constituents of the nitrating acid include: (a) from about 60 to about 90 wt. % sulfuric acid, (b) from about 1 to about 20 wt. % nitric acid, and (c) at least 5 wt. % water. The organic constituents of the nitrating acid include: from about 70 to about 100% by weight nitrotoluene isomers and up to about 30% by weight nitration by-products. The nitration reaction is carrier out under adiabatic conditions. The molar ratio of nitric acid to mononitrotoluene during the nitration reaction is generally from about 0.7:1 to about 1.4:1. The phases generated during the nitration are subsequently separated and the acid phase is treated to remove at least 5 wt. % of the water present therein. The water may be removed by distillation or flash vaporization, optionally with simultaneous heat supply. After removal of the water, nitric acid having a concentration of from about 50 to about 100 wt. % is added to the treated acid phase in amount sufficient to satisfy the compositional limits for a nitrating acid useful in the process of the present invention. This reconcentrated acid phase is then returned to the nitration reaction.

Process for the production of dinitrotoluene and isomeric mixtures of

An aromatic compound is polynitrated in a continuous process in a single apparatus under adiabatic conditions in an emulsion as the reaction medium. From 1.3 to 3.5 mol of HNO.sub.3 per mol of aromatic compound are introduced in the form of a nitronium ion solution into the reactor with the aromatic compound under conditions such that an emulsion forms. The emulsion, which has a tendency to coalesce, is maintained by repeated dispersion. The first dispersion of the liquid streams to produce the emulsion takes place in less than one second. At least 20% of the total amount of HNO.sub.3 to be used should generally be present during this first dispersion. It is preferred, however, that the total amount of nitronium ion solution to be used be present at the time the aromatic compound and nitronium ion solution are first dispersed.

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Dormagen, Germany

Uwe Klingler