CS255372B1 - The method of detoxifying waste water after arylation by diazonium salts - Google Patents

Abstract

The solution deals with the detoxification of wastewater after arylation with diazoin salts. After separation of the reaction mixture by sedimentation, the aqueous layer containing smaller amounts of solvent and starting material is subjected to differential rectification with a variable reflux ratio. The obtained distillate consists of solvent and starting aryl substance and a small amount of water. The residue after rectification does not contain toxic substances in concentrations harmful to biological wastewater treatment with activated sludge.

Description

(54) Method of detoxifying wastewater after arylation with diazonium salts

The solution deals with the detoxification of waste leads after arylation with diazoin salts. After partitioning of the reaction mixture by sedimentation, the aqueous layer containing minor amounts of solvent and feedstock is subjected to a liquid rectification with varying reflux ratio. The distillate obtained consists of a solvent and a starting aryl material and a small amount of water. The residue after rectification does not contain toxic substances in concentrations that are harmful in biological treatment of waste water by activated sludge.

The invention is concerned with the detoxification of waste water after arylation with diazonium salts.

After arylation with diazonium salts, the resulting reaction mixture was separated into an aqueous and an organic layer. Depending on the concentration of the components and the partition coefficient values in the aqueous layer, there is a mixture of solvent and unreacted feedstock residues. In order to recover the solvent poorly, this aqueous solution is further processed in two stages. In the first aqueous layer after the arylation, it is subjected to differential distillation. The mixture of solvent and starting material is separated from water from the distillate by differential rectification. The residue after distillation and rectification is water contaminated with organic substances, so it is necessary to purify it. This method of detoxification has several drawbacks. Multiple thermal stresses lead to reactions leading to the formation of biodegradable toxic substances. Insufficient distillation of the components by differential distillation and discontinuous rectification with a constant reflux ratio leads to further raw material losses and waste water pollution.

These disadvantages are overcome by the present invention. The method for detoxifying waste water after arylation with diazone salts according to the present invention is based on the principle of differential rectification of the aqueous phase with a variable reflux ratio in the range of 0.5 to 10.

Waste water after differential rectification shows low contamination and does not occur! problems with its biological purification. It does not contain toxic substances that are difficult to decompose. Advantages of the process of the present invention are the reduction of raw material and solvent losses, the reduction of the energy consumption of the process, and the reduction of the environmental harmfulness of the waste water produced.

Example 1

Arylation of acrylonitrile with 4-chlorophenyldiazonium chloride under catalysis with cuprous chloride and acetone affords 3- (4-chlorophenyl) -2-chloropropionitrile. The reaction mixture is separated into aqueous and organic layers. The water contained acetone and acrylonitrile in an amount of 15%. Acetone and acrylonitrile are separated from the water in two stages. First, by differential distillation, a mixture with a water content of 38% was obtained, with a distillation residue such as waste water, acetone and acrylonitrile in an amount of 2% by weight. The distillate was subjected to differential rectification with a constant reflux ratio R = 4. The resulting waste water contained 0.9% acetone and acrylonitrile.

Separation of the mixture of the present invention with a reflux ratio of 0.5 to 10 gave a distillate of 20% acrylonitrile and 80% acetone. The water contained in trace amounts. The presence of acetone and acrylonitrile in the residue was not detected by conventional analytical procedures.

Example 2

Arylation as in Example 1. The acetone and acrylonitrile content was 13.5%. The distillate by differential distillation contained acetone and acrylonitrile in an amount of 32.1% and a distillation residue of 2.2%. After differential rectification with a reflux ratio of 4 in the waste water, acetone and acrylonitrile were detected in an amount of 0.8%. According to the present invention, the distillate contained 0.3% water. In wastewater, acetone and acrylonitrile were not detected by conventional analytical procedures.

Claims (1)

SUBJECT A process for detoxifying waste water after arylation with diazonium salts, characterized in that the solvent and the unreacted compound are separated by differential rectification with a variable reflux ratio in the range of 0.5 to 10.