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Process for preparing aromatic amines

A technology for aromatic amines and aromatic hydrocarbons, applied in the field of preparation of aromatic amines, which can solve problems such as process difficulties and reduce the thermal stability of dinitrotoluene

Active Publication Date: 2005-02-02
COVESTRO DEUTSCHLAND AG +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, the use of this water in chemical processes is often problematic because these impurities cause difficulties in processes where the impurities are present in the reclaimed water
For example, this recycled water can produce unwanted side reactions
[0004] In particular, diaminotoluene reacts with dinitrotoluene to form unwanted by-products, in other words, especially reduces the thermal stability of dinitrotoluene

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] Separate the reaction water from the reaction solution obtained by the hydrogenation reaction

[0030] A 50 mm diameter bubble column with 30 plates and a transverse discharge on the 20th plate was used. This column is operated at a pressure of 3 bar absolute and a bottom temperature of about 200°C. Reaction of about 60% by weight toluenediamine (TDA) isomer mixture with an organic secondary product concentration of 0.5% by weight and a water content of about 40% by weight by catalytic hydrogenation of dinitrotoluene (DNT) and hydrogen mixture. This reaction mixture is fed into the 5th plate of the column at a rate of 2 kg / h. By heating at the bottom of the column, 1100 g / h of steam are generated at the top of the column. These vapors were condensed and returned to the column as reflux, and 15 g / h of distillate were withdrawn, which contained the volatile secondary products. 1250 g of a TDA isomer mixture with a water content of 4% by weight were withdrawn continuo...

Embodiment 2

[0032] Crude DNT was washed with reaction water from the hydrogenation reaction

[0033] In this example three mixer / separators in series were used, each consisting of a 1 liter stirred flask and a 1 liter separating vessel. At 70° C., 1900 g / h of crude DNT (similar to the two-step reaction of toluene and nitrating acid) with a sulfuric acid concentration of 1.2% by weight, a nitric acid concentration of 0.8% by weight and a cresol and organic acid concentration of 0.6% by weight mixture) placed in this mixer / separator set. The washed DNT from each stage was siphoned from each separation vessel into the next stirred vessel in series as the lower phase. DNT of technical grade purity was obtained from the last separation vessel.

[0034]In a first stirred vessel, 200 g / h of reaction water from Example 1 were added as washing liquid. In a second stirred vessel, 200 g / h of 5% strength by weight soda solution were added. In a third stirred vessel, 535 g / h of the remaining rea...

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PUM

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Abstract

Aromatic amines are produced from aromatic hydrocarbons by a) reacting the aromatic hydrocarbon(s) with a mixture of nitric acid and sulfuric acid to generate a two-phase reaction mixture, b) separating the reaction mixture into an aqueous acid phase and an organic phase containing the nitroaromatic compounds c) washing the organic phase to purify the nitroaromatic compound(s), d) hydrogenating the nitroaromatic compound(s) in the presence of a catalyst to produce the aromatic amine(s) and water of reaction, and e) separating the water of reaction formed in step d) from the aromatic amine(s), in which the water of reaction separated in step e) is used to wash the organic phase containing the nitroaromatic compounds in step c).

Description

technical field [0001] The invention relates to a method for preparing aromatic amines from aromatic hydrocarbons, wherein the nitrated aromatic compounds obtained by nitrating corresponding aromatic hydrocarbons are washed with reaction water produced in the process of hydrogenating nitroaromatic compounds. Background technique [0002] Aromatic amines and diamines are used in large quantities as chemical intermediates, for example for the preparation of dyes or plastics; industrially, it is produced by nitrating aromatic hydrocarbons to form nitroaromatic compounds and then hydrogenating said nitroaromatic compounds. In this case, during nitration with nitric acid, 1 mole of water is produced per mole of nitro groups; during hydrogenation, 2 moles of water are produced per mole of amine groups. This water eventually leaves the process as wastewater. In particular other waste waters are also generated during the treatment of said nitroaromatics, which is usually carried ou...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07B61/00C07C201/08C07C201/16C07C205/06C07C209/36C07C209/82C07C209/86C07C211/50C07C211/51
CPCC07C201/08C07C209/36C07C201/16C07C211/51C07C205/06C07C209/82
Inventor B·凯根霍夫K·R·西特克斯C·穆勒D·N·泽弗迪斯
Owner COVESTRO DEUTSCHLAND AG
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