CN101781175B - Method for separating 2,4-Dichlorophenol and 2,6-Dichlorophenol - Google Patents

Abstract

The invention discloses a method for separating 2,4-dichlorophenol and 2,6-dichlorophenol. The method is as follows: dissolving the mixture of 2,4-dichlorophenol and 2,6-dichlorophenol In an organic solvent, add basic organic matter, stir and react at 40-80°C until the reaction liquid is clear, the reaction is over, after the reaction liquid is cooled, stand to precipitate crystals, filter to obtain filter cake A and filtrate A, 2, 4 -Dichlorophenol stays in filtrate A, and filter cake A is 2,6-dichlorophenol crude product; Described basic organic matter is triethylenediamine, morpholine, piperazine, ethylpiperazine or methylpiperazine; The organic solvent is ethanol, methanol, acetone or ethyl acetate. The separation efficiency of the present invention is relatively high, only one crystallization is required, the total yield of 2,4-dichlorophenol is 90%-95%, the purity is 96%-99%, and the total yield of 2,6-dichlorophenol is 77% to 89%, purity 90% to 99%, simple operation, good repeatability, low implementation cost, and beneficial to industrial scale-up.

Description

A method for separating 2,4-dichlorophenol and 2,6-dichlorophenol

(1) Technical field

The invention relates to a method for separating 2,4-dichlorophenol and 2,6-dichlorophenol.

(2) Background technology

2,4-Dichlorophenol is an important fine chemical product, mainly used in pesticides, medicines and auxiliary products. Due to the intensified development of downstream products of p-dichlorophenol in China in recent years, especially the successful development of antifungal agent TCS and pesticide oxadiazone in my country, it has brought great benefits to the application and development of 2,4-dichlorophenol in my country. opportunity.

In the pesticide industry, 2,4-dichlorophenol is mainly used in the production of insecticides phenophos and herbicides, methyl ester herbicides, biben, dichlorophenoxy acid and its esters; in the pharmaceutical industry for the production of Insect repellent sulfur bisdichlorophene; used in the auxiliary industry to produce preservative TCS. However, the amount of 2,4-dichlorophenol used in the production of diclofenac and its ester herbicides in China is relatively stable, and is increasing at an annual growth rate of 8% to 10%.

Generally, the products 2,4-dichlorophenol and 2,6-dichlorophenol are obtained by direct chlorination of phenol, but in this reaction, 2,4-dichlorophenol and 2,6-dichlorophenol are equally generated, Therefore, the purity of the 2,4-dichlorophenol obtained in this way is relatively low. Most of the current products use 2,4-dichlorophenol with a content of less than 90%, so that the yield of the downstream products produced is low and more wastes are generated. With the increasing emphasis on environmental protection and the requirement for the purity of processed products, these manufacturers will gradually switch to high-content 2,4-dichlorophenol. The following are the molecular structures of 2,6-dichlorophenol and 2,4-dichlorophenol:

2,6-Dichlorophenol 2,4-Dichlorophenol

From the above molecular structures of 2,6-dichlorophenol and 2,4-dichlorophenol, it can be seen that the structural formulas of the two are very similar, and their boiling points are 218°C and 210°C respectively. Traditional separation and purification methods include: fractional crystallization, refining, dissociation extraction, adsorption separation, and separation using the difference in physical properties of the ammonia salts of two phenols.

(1) Distillation is the main traditional purification method. Some factories use rectification to separate and purify 2,4-dichlorophenol, but chlorophenols are kept at high temperature for a long time during the rectification process, and the resinous raffinate formed by some chlorophenols increases post-processing and environmental protection. Load, the difference in boiling point of each isomer is very small. The small difference in properties makes it difficult to achieve the expected separation effect by traditional distillation methods. In addition, rectification is energy-intensive and therefore not ideal.

(2) Hermann A et al. have reported utilizing zeolite to adsorb and separate 2,4-dichlorophenol, and using zeolite as an adsorbent to separate chlorophenols can contain 2,4-dichlorophenol and 2,6-dichlorophenol 2,4-dichlorophenol is separated from the mixture, but this method is complicated to operate and has low efficiency, which is not suitable for industrialization.

(3) Foreign patents report the separation of 2,4-dichlorophenol and 2,6-dichlorophenol mixed phenols by utilizing the physical properties of the ammonia salts of two phenols. In this method, after treating the mixed phenol with ammonia water, the feed liquid will be separated into a solid phase layer rich in 2,4-dichlorophenol and a water layer rich in 2,6-dichlorophenol, and the two phases can be further treated. Separate 2,4,2,6-mixed phenols. The disadvantage of this method is that the yield is low and it is not suitable for industrialization.

(4) Someone used dissociation extraction to separate 2,4,2,6-dichlorophenol. The dissociation constants of 2,4-dichlorophenol and 2,6-dichlorophenol are 18 and 160 respectively, and the difference in acidity will cause 2,6-dichlorophenol to preferentially form a salt and enter the water phase, so that when the material and the organic The 2,6-dichlorophenol will gradually transfer to the water phase when the solution and the aqueous solution of the inorganic alkali are in constant contact, and the purer 2,4-dichlorophenol can be obtained from the organic phase. The disadvantages are that the requirements for equipment are relatively high, the investment is relatively large, the operation is complicated, and a large amount of organic solvents and alkalis are used.

(5) Foreign patents report the separation of 2,4,2,6-dichlorophenol mixtures by means of dissociation, extraction, dehydration and precipitation. Based on the molar equivalent of 2,6-dichlorophenol that is predicted to be preferentially salted in mixed phenols, add NaOH quantitatively and gradually remove all the water, and 2,6-dichlorophenol will be in the form of sodium salt in the liquid that has no water phase. Precipitate from the organic phase under certain conditions, so as to achieve the purpose of separation and purification. This method has less investment than simple dissociation extraction equipment and is simple to operate, but it still cannot avoid the use of a large amount of organic solvents, and the product purity is not ideal.

The above separation methods have the disadvantages of high energy consumption, difficult post-processing, high requirements for equipment conditions, correspondingly large investment, and complicated operation. Therefore, a more economical and simple separation method needs to be further studied. The purpose of the present invention is to utilize the principle of molecular recognition, on the basis of carefully considering low energy consumption, environmental friendliness and simple process, to provide a method for separating 2,6-dichlorophenol and 2,4-dichlorophenol mixture .

(3) Contents of the invention

The technical problem to be solved by the present invention is to provide a simple and efficient method for separating the mixture of 2,4-dichlorophenol and 2,6-dichlorophenol by using the principle of molecular recognition.

The research idea of the present invention is: the physical and chemical properties of 2,4-dichlorophenol and 2,6-dichlorophenol are very similar, but their spatial configuration and acidity have certain differences, and this difference makes them different from specific alkalis. Sexual organisms have different binding abilities, resulting in selective binding.

In order to solve the technical problems of the present invention, the present invention adopts the following technical solutions:

A method for separating 2,4-dichlorophenol and 2,6-dichlorophenol, said method comprising the following steps: (1) first detecting 2,4-dichlorophenol and 2,6-dichlorophenol The content of 2,6-dichlorophenol in the mixture, the mixture of 2,4-dichlorophenol and 2,6-dichlorophenol is dissolved in the organic solvent, the basic organic matter is added, and the reaction is stirred at 40-80°C , until the reaction solution is clear and the reaction is over, the reaction solution is cooled to -10～40°C, and the crystals are separated out after standing, and the filter cake A and the filtrate A are obtained by filtration. 2,4-Dichlorophenol remains in the filtrate A, and the filter cake A is 2,6-dichlorophenol crude product; Described basic organic matter is triethylenediamine, morpholine, piperazine, ethylpiperazine or methylpiperazine; Described basic organic matter and 2,4-dichlorophenol and The amount ratio of 2,6-dichlorophenol in the mixture of 2,6-dichlorophenol is 1.2-1.5:1; the organic solvent is ethanol, methanol, acetone or ethyl acetate.

The method also includes step (2): recrystallizing the filter cake A obtained in step (1) with a recrystallization solvent to obtain complex crystals, adding hydrochloric acid to the complex crystals, stirring to fully react, then extracting with an extraction solvent, and statically Place the layers and get the organic layer for distillation to obtain 2,6-dichlorophenol; the recrystallization solvent is ethanol, methanol, acetone or ethyl acetate; the extraction solvent is petroleum ether, benzene, chloroform or ethyl acetate.

The filtrate A obtained in the step (1) is distilled to obtain 2,4-dichlorophenol.

The time for standing to precipitate crystals in the step (1) is 6-10 days.

The volumetric usage of the organic solvent in the step (1) is 3-4 ml/g based on the mass of the mixture of 2,4-dichlorophenol and 2,6-dichlorophenol.

The mass concentration of hydrochloric acid in the step (2) is 5-20wt%.

In the described step (2), the mass ratio of 2,6-dichlorophenol measured in the mixture of hydrogen chloride and 2,4-dichlorophenol and 2,6-dichlorophenol in hydrochloric acid is 1～2: 1.

The basic organic substance in the present invention is preferably triethylenediamine, morpholine or piperazine.

The organic solvent of the present invention is preferably ethanol, methanol or acetone.

The recrystallization solvent of the present invention is preferably ethanol, methanol or acetone.

The extraction solvent of the present invention is preferably petroleum ether, benzene or chloroform.

More specifically, it is recommended that the method of the present invention be carried out according to the following steps:

(1) first detect 2, the content of 2,6-dichlorophenol in the mixture of 2,4-dichlorophenol and 2,6-dichlorophenol, the content of 2,4-dichlorophenol and 2,6-dichlorophenol Dissolve the mixture in an organic solvent, add basic organic matter, stir and react at a temperature of 40-80°C for 1-2 minutes, until the reaction liquid is clear, and the reaction is completed, the reaction liquid is cooled to -10-40°C, and allowed to stand for 6-10 days Crystals are precipitated, filtered to obtain filter cake A and filtrate A, and filtrate A is distilled to obtain 2,4-dichlorophenol, and filter cake A is the crude product of 2,6-dichlorophenol; the basic organic matter is triethylenediamine, morpholine , piperazine, ethylpiperazine or methylpiperazine; the amount of 2,6-dichlorophenol in the mixture of said basic organic matter and 2,4-dichlorophenol and 2,6-dichlorophenol The ratio is 1.2～1.5: 1; the organic solvent is ethanol, methanol, acetone or ethyl acetate; the volume consumption of the organic solvent is based on the mass of the mixture of 4-dichlorophenol and 2,6-dichlorophenol 3~4ml/g;

(2) Recrystallize the filter cake A obtained in step (1) with a recrystallization solvent to obtain complex crystals, add 5 to 20 wt% hydrochloric acid to the complex crystals, stir and react fully, hydrogen chloride in hydrochloric acid and 2,4-dichlorophenol and 2, the mass ratio of 2,6-dichlorophenol measured in the mixture of 6-dichlorophenol is 1～2: 1, then extract with extraction solvent, leave to stand for layering, get the organic layer and distill to obtain 2 , 6-dichlorophenol; the recrystallization solvent is ethanol, methanol, acetone or ethyl acetate; the extraction solvent is petroleum ether, benzene, chloroform or ethyl acetate.

The consumption of described recrystallization solvent is counted as 3～4ml/g with the mass of filter cake A, and the consumption of extraction solvent in described step (2) and the volume ratio (being the volume of hydrochloric acid) of extracted mother liquor are 1 : 1~2.

Compared with the existing technology, this method is based on the basic principle of supramolecular assembly, using the topological matching between the host molecule and the guest molecule, so that 2,6-dichlorophenol can selectively form a stable compound with basic organic matter. Molecular crystals, so as to achieve efficient and rapid separation, its advantages mainly lie in:

a) The separation efficiency is relatively high. Due to the high selectivity of molecular recognition, only one crystallization is required to achieve a total yield of 2,4-dichlorophenol between 90%-95%, and a purity between 96%-99%; 2,6- The total yield of dichlorophenol is between 77%-89%, and the purity is between 90%-99%.

b) The operation is simple, the repeatability is good, the implementation cost is low, and it is beneficial to industrial scale-up.

(4) Specific implementation methods

The technical solutions of the invention will be further described below with specific implementation examples, but the protection scope of the present invention is not limited thereto.

The mixture of 2,4-dichlorophenol and 2,6-dichlorophenol in the examples of the present invention is the product obtained by direct catalytic chlorination of phenol, which comes from a chemical factory in Shangyu

The detection method in the embodiment of the present invention is high performance liquid chromatography, Shimadzu LC-10AT type high performance liquid chromatography.

Example 1:

In a 200ml beaker, add 150ml ethanol and 50g 2,4 dichlorophenol, 2,6-dichlorophenol mixture, detect through high performance liquid chromatography (the same below) wherein 2,4-dichlorophenol and 2,6-dichlorophenol The content of phenol was 50% and 50% respectively, then 16g of morpholine was added, stirred and heated at 70° C. for 2 minutes until the solution was clear. Placed under the greenhouse for 7 days, colorless and transparent crystals were precipitated, and filtered under reduced pressure to obtain 31.5 g of filter cake crystals and filtrate. compound, and 2,4-dichlorophenol is left in the filtrate, and then high-purity 2,4-dichlorophenol 22.8g can be obtained by distillation, the yield is 91%, and the purity is 96% (high performance liquid Phase chromatography detection, the same below). Use 100ml of ethanol to recrystallize the crude 2,6-dichlorophenol once, add it to 60ml of 10% dilute hydrochloric acid solution for a full reaction at room temperature, then add 60ml of petroleum ether for extraction, leave it to stand for layers, and take the organic layer by distillation. 20.4 g of 2,6-dichlorophenol was obtained with a yield of 82% and a purity of 93% (detected by high performance liquid chromatography, the same below).

Example 2:

In a 500ml beaker, add 200ml methanol and 50g 2,4 dichlorophenol, 2,6-dichlorophenol mixture, wherein the contents of 2,4-dichlorophenol and 2,6-dichlorophenol are respectively 60% and 40%, then add 16g of triethylenediamine, stir and heat at 60°C for 2 minutes until the solution is clear. Placed under the greenhouse for 6 days, colorless and transparent crystals were precipitated, and suction filtration under reduced pressure obtained 30.8 g of filter cake crystals and filtrate. The crystals were 2,6-dichlorophenol crude product, which was 2,6-dichlorophenol and triethylene The compound of diamine, while 2,4-dichlorophenol is left in the filtrate, and then 28.0 g of high-purity 2,4-dichlorophenol can be obtained by distillation, the yield is 93%, and the purity is 98%. Recrystallize the crude product of 2,6-dichlorophenol once with 100ml of methanol, add it to 60ml of 10% dilute hydrochloric acid solution for a full reaction at room temperature, then add 60ml of benzene for extraction, let it stand for layers, and take the organic layer and obtain it by distillation 15.4 g of 2,6-dichlorophenol, with a yield of 77% and a purity of 96%.

Example 3:

Add 150ml ethanol and 50g 2,4 dichlorophenol, 2,6-dichlorophenol mixture in 200ml beaker, wherein 2,4-dichlorophenol and 2, the content of 6-dichlorophenol are respectively 60% and 40%, then add 12.5g piperazine, stir and heat at 70°C for 2 minutes until the solution is clear. Placed at room temperature for 8 days, colorless and transparent crystals precipitated, and filtered under reduced pressure to obtain 30.5 g of filter cake crystals and filtrate. The crystals were crude 2,6-dichlorophenol, which was the mixture of 2,6-dichlorophenol and piperazine. The complex, while 2,4-dichlorophenol is left in the filtrate, and then high-purity 2,4-dichlorophenol 29.1g can be obtained by distillation, the yield is 97%, and the purity is 98%. Use 100ml of acetone to recrystallize the crude 2,6-dichlorophenol once, add it to 60ml of 10% dilute hydrochloric acid solution for a full reaction at room temperature, then add 60ml of chloroform for extraction, let it stand for layers, and take the organic layer by distillation to obtain 17.0 g of 2,6-dichlorophenol, with a yield of 85% and a purity of 99%.

Example 4:

Add 150ml of acetone and 50g of 2,4-dichlorophenol and 2,6-dichlorophenol mixture into a 200ml beaker, the contents of 2,4-dichlorophenol and 2,6-dichlorophenol are respectively 70% after testing and 30%, then add 15.7g of ethylpiperazine, stir and heat at 50°C for 2 minutes until the solution is clear. Placed under the greenhouse for 7 days, colorless and transparent crystals precipitated, and 25.7 g of filter cake crystals and filtrate were obtained by suction filtration under reduced pressure. The crystals were crude 2,6-dichlorophenol. The compound of piperazine, while 2,4-dichlorophenol is left in the filtrate, and then 31.9 g of high-purity 2,4-dichlorophenol can be obtained by distillation, the yield is 91%, and the purity is 97%. Use 100ml of ethyl acetate to recrystallize the crude 2,6-dichlorophenol once, add it to 50ml of 10% dilute hydrochloric acid solution for a full reaction at room temperature, then add 50ml of ethyl acetate for extraction, let stand to separate layers, and take the organic layer 13.4 g of 2,6-dichlorophenol was obtained by distillation with a yield of 89% and a purity of 93%.

Example 5:

Add 150ml of ethyl acetate and 50g of 2,4-dichlorophenol and 2,6-dichlorophenol mixture into a 200ml beaker, the contents of 2,4-dichlorophenol and 2,6-dichlorophenol are respectively 80% after testing and 20%, then add 7.2g of methylpiperazine, stir and heat at 77°C for 2 minutes until the solution is clear. Placed under the greenhouse for 6 days, colorless and transparent crystals precipitated, and filtered under reduced pressure to obtain 16.2 g of filter cake crystals and filtrate. The crystals were 2,6-dichlorophenol crude product, which was 2,6-dichlorophenol and methyl The compound of piperazine, while 2,4-dichlorophenol is left in the filtrate, and then 38.0 g of high-purity 2,4-dichlorophenol can be obtained by distillation, the yield is 95%, and the purity is 98%. Use 50ml of ethanol to recrystallize the crude product of 2,6-dichlorophenol once, add it to 30ml of 10% dilute hydrochloric acid solution for a full reaction at room temperature, then add 30ml of petroleum ether for extraction, let it stand for stratification, and take the organic layer by distillation. 7.8 g of 2,6-dichlorophenol was obtained with a yield of 78% and a purity of 99%.

Claims (8)

1. one kind is separated 2, 4-chlorophenesic acid and 2, the method of 6-chlorophenesic acid, it is characterized in that described method comprises the following steps: (1) first detects 2, 4-chlorophenesic acid and 2, in the mixture of 6-chlorophenesic acid 2, the content of 6-chlorophenesic acid, by 2, 4-chlorophenesic acid and 2, the mixture of 6-chlorophenesic acid is dissolved in organic solvent, add alkaline organic, stirring reaction at 40 ~ 80 DEG C of temperature, clarify to reaction solution, reaction terminates, reaction solution is cooled to-10 ~ 40 DEG C, leave standstill crystallize out, filtration obtains filter cake A and filtrate A, 2, 4-chlorophenesic acid is stayed in filtrate A, filtrate A distillation obtains 2, 4-chlorophenesic acid, filter cake A is 2,6-chlorophenesic acid crude product, described alkaline organic is triethylene diamine, in the mixture of described alkaline organic and 2,4 dichloro phenol and 2,6-chlorophenesic acid, the ratio of the amount of substance of 2,6-chlorophenesic acid is 1.2 ~ 1.5:1, described organic solvent is ethanol, methyl alcohol, acetone or ethyl acetate,

(2): filter cake A recrystallization solvent recrystallization step (1) obtained, obtain compound crystal, compound crystal adds hydrochloric acid, stir fully reaction, then with extraction solvent extraction, stratification is got organic layer distillation and is obtained 2,6-chlorophenesic acid; Described recrystallization solvent is ethanol, methyl alcohol, acetone or ethyl acetate; Described extraction solvent is sherwood oil, benzene, chloroform or ethyl acetate.

2. the method for claim 1, is characterized in that the volumetric usage of described organic solvent counts 3 ~ 4ml/g with the quality of the mixture of 2,4 dichloro phenol and 2,6-chlorophenesic acid.

3. the method for claim 1, is characterized in that the mass concentration of hydrochloric acid in described step (2) is 5 ~ 20wt%.

4. the method for claim 1, is characterized in that the amount of substance ratio of 2,6-chlorophenesic acid in the mixture of hydrogenchloride and 2,4 dichloro phenol and 2,6-chlorophenesic acid in hydrochloric acid in described step (2) is 1 ~ 2:1.

5. the method for claim 1, is characterized in that the time of the standing crystallize out in described step (1) is 6-10 days.

6. the method for claim 1, is characterized in that described method is carried out in accordance with the following steps:

(1) first 2 are detected, 4-chlorophenesic acid and 2, in the mixture of 6-chlorophenesic acid 2, the content of 6-chlorophenesic acid, by 2,4 dichloro phenol and 2, the mixture of 6-chlorophenesic acid is dissolved in organic solvent, add alkaline organic, at 40 ~ 80 DEG C of temperature, stirring reaction 1 ~ 2 minute, clarifies to reaction solution, reaction terminates, reaction solution is cooled to-10 ~ 40 DEG C, leaves standstill 6-10 days crystallize outs, filters and obtains filter cake A and filtrate A, filtrate A obtains 2 after distilling, 4-chlorophenesic acid, filter cake A is 2,6-chlorophenesic acid crude product; Described alkaline organic is triethylene diamine; In the mixture of described alkaline organic and 2,4 dichloro phenol and 2,6-chlorophenesic acid, the ratio of the amount of substance of 2,6-chlorophenesic acid is 1.2 ~ 1.5:1; Described organic solvent is ethanol, methyl alcohol, acetone or ethyl acetate; The volumetric usage of described organic solvent counts 3 ~ 4ml/g with the quality of the mixture of 2,4 dichloro phenol and 2,6-chlorophenesic acid;

(2) filter cake A recrystallization solvent recrystallization step (1) obtained, obtain compound crystal, compound crystal adds 5 ~ 20wt% hydrochloric acid, stirs and fully reacts, hydrogenchloride and 2 in hydrochloric acid, in the mixture of 4-chlorophenesic acid and 2,6-chlorophenesic acid, the amount of substance ratio of 2,6-chlorophenesic acid is 1 ~ 2:1, then extract with extraction solvent, stratification, gets organic layer distillation and obtains 2,6-chlorophenesic acid; Described recrystallization solvent is ethanol, methyl alcohol, acetone or ethyl acetate; Described extraction solvent is sherwood oil, benzene, chloroform or ethyl acetate.

7. method as claimed in claim 6, is characterized in that the consumption of described recrystallization solvent counts 3 ~ 4ml/g with the quality of filter cake A.

8. method as claimed in claim 6, the consumption that it is characterized in that described extraction solvent is 1:1 ~ 2 with the volume ratio of the mother liquor be extracted.