SU650984A1 - Method of purifying chlorbenzols - Google Patents

Description

This invention relates to a process for the purification of chlorobenzenes from acidic admixtures of hydrogen chloride, which is formed as a by-product in the benzene chlorination, and metal chloride, usually ferric chloride, which is the catalyst for the benzene chlorination process. Chlorobenzenes are widely used in the industry of basic organic synthesis. The benzene chlorination product has the following composition, wt.%: Benzene 65-70 Chlorobenzene 28-33 Polychlorides2-3. The liquid has an acid reaction, contains 2-4 g / l of hydrogen chloride and 0.2-0.5 g / l of ferric chloride (FeCy) A known method of purification of chlorobenzenes - products of chlorination of benzene from impurities of hydrogen chloride (НСЕ and ferric chloride FeCEj) by passing them through a column filled with an absorbing substance - silica-alumina, silica gel, clay 1. This method does not provide the required degree of purification. In addition, regeneration of the absorber by stripping leads to the formation of a large amount of toxic wastewater. The invention, according to its technical essence and the achieved result, is a method of purification of benzene derivatives from hydrochloric acid and aluminum chloride residues by passing them through a column filled with ion exchanger 2. The method provides complete purification. entails a significant consumption of hydrochloric acid ionite required for regeneration, which after regeneration is removed into drains, as well as loss of ion exchanger, which in general reduces the efficiency of the process . The aim of the invention is to eliminate these drawbacks, namely increasing the efficiency of the process. This goal is achieved by the method of purification of chlorobenzenes from acidic impurities and the catalyst, metal chloride, by passing an ion exchanger through the layer, and the initial chlorobenzenes are pre-washed with water, usually in countercurrent mode at 50-80 C.

Upon contact of the benzene derivatives with water, hydrochloric acid and ferric chloride are extracted into the aqueous layer.

Extraction is carried out in countercurrent mode, providing the most favorable contacting. The process is expediently carried out at 50-80 ° C, which contributes to a high degree of extraction of inorganic impurities into the aqueous phase.

Example. Washing the products of chlorination of benzene with water is carried out at 65 ° C in countercurrent mode, after cleaning the products of chlorination of benzene with water (molar ratio water: product of chlorination -1: 20)

in benzene chlorination product

before contact with water

2.65

NSE

0,

FeCE,

With a speed of 10–20 hours, the product is fed to a column 25 mm in diameter, 600 mm high, filled with 20 cm of cation exchanger KU-2.

The product leaving the column is monitored for acid, iron and chlorine content. Iron is determined by the calorimetric rhodanide method, chlorine-mercurometric ions. The test is carried out until the appearance of traces of iron or acid in the liquid being cleaned

The test results are presented in Table. 1 and tab. 2

Table 1

Content, g / l

in water after contact with product after contact with water

53.0

0,006

3.64

0,008

table 2

As can be seen from the tables, cleaning the chlorination products with pre-washing them with water at a ratio of water: product-1: 20 allows increasing the inter-regeneration period by about 15 times, reducing the amount of waste-regenerate in 15.7 r h compared to the known 2 method cleaning up.

The supply to the ionite of a product preliminarily purified with water contributes to the preservation of its exchange ability for a longer time, which makes it possible to increase the service life of the ion exchanger.

An increase in the interregeneration period leads to a decrease in ionch loss associated with its frequent regeneration, and a decrease in the consumption of hydrochloric acid for the regeneration of the ion exchanger.

In addition, when washing with water, almost all of the hydrogen chloride is absorbed. The resulting solution is hydrochloric

acids are removed from the process, purified from ferric chloride and used to produce conditioned hydrochloric acid.

Claims (2)

1. The method of purification of chlorobenzenes from acidic impurities and a catalyst of metal chloride by passing through an ion exchanger, about tl and h rain and so that, in order to improve the efficiency of the process, the initial chlorobenzenes are pre-washed with water. 2. Method POP.1, characterized by the fact that the washing with water is carried out in countercurrent mode at 50-80 ° C. Sources of information taken into account in the examination 1. USSR author's certificate No. 105134, cl. C 10 a 25/04, 21.04.55. 2. USSR author's certificate No. 295741, cl. From 07 to 13/00, 07/11/68.