WO2019179287A2 - Preparation method for 2,4-dichlorophenoxyacetic acid or salt thereof - Google Patents

Description

Preparation method of 2,4-dichlorophenoxyacetic acid and salt thereof

This application claims priority to Chinese patent application filed on March 19, 2018, the Chinese Patent Office, application number 201810226607.X, and the invention entitled "Preparation of a 2,4-dichlorophenoxyacetic acid and its salt" The entire contents are hereby incorporated by reference.

Technical field

The invention relates to the technical field of herbicide preparation, in particular to a preparation method of 2,4-dichlorophenoxyacetic acid and a salt thereof.

Background technique

As a hormonal selective herbicide, chlorophenoxycarboxylic acid compounds are environmentally friendly, have short residual period and low toxicity to humans and other organisms, and rarely produce drug resistance. They are mainly used for corn, wheat and other diseases. Undergraduate crop fields have a large market demand for the control of dicotyledonous weeds, sedges and certain malignant weeds. Among them, 2,4-dichlorophenoxyacetic acid is the most widely used.

At present, the preparation method of 2,4-dichlorophenoxyacetic acid mainly comprises the following two steps:

1) using phenol as the main raw material, chlorination to obtain 2,4-dichlorophenol;

2) 2,4-Dichlorophenol is condensed with chloroacetic acid under basic conditions to obtain a condensation liquid. When the target product is an alkali metal salt of 2,4-dichlorophenoxyacetic acid, the condensation liquid is directly filtered, washed with water and then dried to obtain an alkali metal salt of 2,4-dichlorophenoxyacetic acid; when the target product is In the case of 2,4-dichlorophenoxyacetic acid, the condensation liquid is acidified, washed with water and dried to obtain 2,4-dichlorophenoxyacetic acid; when the target product is 2,4-dichlorophenoxyacetic acid amine salt, condensation The liquid needs to be acidified, washed with water and dried to obtain 2,4-dichlorophenoxyacetic acid, and then reacted with ammonium carbonate, ammonium hydrogencarbonate, ammonia or organic amine.

In the above preparation method, the intermediate product 2,4-dichlorophenol is formed, which has an extremely unpleasant pungent odor, resulting in extremely poor environment at the production site, and poor chlorination selectivity results in low purity.

During the condensation of the condensation solution in step 2), the impurities in the chlorophenol, dichlorophenol and polychlorophenol, undergo condensation between the two molecules, resulting in a highly toxic, refractory series of compounds, dioxins. Produces a large amount of hazardous waste containing chlorophenols, chlorophenoxyacetic acid, and also contains dioxins in the output products, which poses a great risk to the health of the environment and production personnel, and the dioxin will follow The use of the product enters the plant, air, soil and water sources and is enriched with the food chain, causing more serious environmental hazards.

Therefore, the development of an advanced synthetic process is imminent.

Summary of the invention

In view of this, the technical problem to be solved by the present invention is to provide a preparation method of 2,4-dichlorophenoxyacetic acid and a salt thereof, which has high yield and purity, and less waste.

In order to solve the above technical problems, the present invention provides a preparation method of 2,4-dichlorophenoxyacetic acid, comprising the following steps:

S1) phenol and chloroacetate are reacted under basic conditions to obtain phenoxyacetate;

S2) phenoxyacetate under the action of catalyst A and catalyst B, and selective chlorination with a chlorinating agent to obtain 2,4-dichlorophenoxyacetate;

The catalyst A is a Lewis acid;

The catalyst B is a C5-22 thioether, thiazole, isothiazole, thiophene or a halogenated derivative thereof;

S3) 2,4-Dichlorophenoxyacetate is subjected to a hydrolysis reaction under acidic conditions to obtain 2,4-dichlorophenoxyacetic acid.

First, phenol and chloroacetate are reacted under basic conditions provided by a basic compound.

Preferably, the phenol and the base are dehydrated directly in an organic solvent, and then subjected to an anhydrous reaction with the chlorocarboxylic acid ester, thereby eliminating the generation of high-salt wastewater and reducing the by-product yield of the metal chloride by 50%. the above.

Specifically, the phenol and the basic compound are mixed in an organic solvent, and heated to reflux to a moisture content of ≤0.5% (mass content), and then mixed with chloroacetate to cause phenoxyacetate.

The basic compound may be a general basic compound containing potassium, sodium, calcium or magnesium, preferably sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate or sodium carbonate. And any one or more of potassium carbonate.

When the basic compound is sodium hydroxide, potassium hydroxide, sodium hydrogencarbonate or potassium hydrogencarbonate, the molar ratio of the phenol to the basic compound is preferably 1: (1 to 1.08), more preferably 1: (1). 1.04), further preferably 1: (1.02 to 1.04); when the basic compound is calcium hydroxide, magnesium hydroxide, sodium carbonate or potassium carbonate, the molar ratio of the phenol to the basic compound is preferably 1: (0.5) ～0.54) is more preferably 1: (0.5 to 0.52), still more preferably 1: (0.51 to 0.52).

The basic compound may be a solid, an aqueous solution, or a paste, and the concentration of the aqueous solution is preferably ≥ 30%.

The organic solvent is preferably any one or more of benzene, toluene and xylene.

The organic solvent is preferably used in an amount of from 1 to 5 times, more preferably from 1.5 to 2.5 times, based on the weight of the phenol.

The chloroacetate has a formula of ClCH ₂ COOR, wherein R is a C1-10 alkyl group or a C3-10 cycloalkyl group, preferably a C1-4 alkyl group. In certain embodiments of the invention, it is methyl, ethyl, propyl, isopropyl or butyl.

The molar ratio of the phenol to the chloroacetate is preferably 1: (1 to 1.08), more preferably 1: (1 to 1.04), still more preferably 1: (1.02 to 1.04).

The manner in which the chloroacetate is added is preferably dropwise.

The reaction temperature in the above step S1) is preferably 60 to 120 ° C, more preferably 60 to 100 ° C, still more preferably 80 to 100 ° C. The reaction time is preferably 0.2 to 1 h, more preferably 0.3 to 0.8 h, still more preferably 0.5 to 0.6 h.

After the reaction is completed, preferably, the system is cooled and filtered, and the filter cake is washed and dried to obtain a metal chloride. After the filtrate is distilled to recover the solvent, it is phenoxyacetate.

The phenoxyacetate has the structure shown in the following formula 1:

The range of R is the same as above, and will not be described here.

The obtained phenoxyacetate is then mixed with Catalyst A, Catalyst B, and then a chlorinating agent is added for selective chlorination.

The catalyst A is a Lewis acid; preferably SnCl ₄ , MgCl ₂ , FeCl ₃ , AlCl ₃ , BF ₃ , ZnCl ₂ , TiCl ₄ , SbF ₅ , Al ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , Pb (OAc ₂ , one or more of Zn(OAc) ₂ and Al ₂ O(OAc) ₄ ; more preferably one of MgCl ₂ , FeCl ₃ , ZnCl ₂ , SbF ₅ , TiO ₂ and Pb(OAc) ₂ One or more kinds are further preferably one or more of FeCl ₃ , TiO ₂ and Pb(OAc) ₂ .

The catalyst B is a C5-22 thioether, thiazole, isothiazole, thiophene or a halogenated derivative thereof; preferably tert-butyl methyl sulfide, tert-butyl sulfide, phenyl sulfide, 4,4'-two Chlorophenyl sulfide, 2-methylphenyl sulfide, 2,4,6-trimethylphenyl sulfide, 4,4'-thiobis(6-tert-butyl-3-methylphenol), thiazole, 2-ethylthiazole, 2,5-dichlorothiazole, 4-methylthiazole, 2-tert-butylthiazole, isothiazole, 4,5-dimethylisothiazole, 5-chloroisothiazole, 2,4, One of 5-tri-tert-butylisothiazole, thiophene, 2-methylthiophene, 2,5-dimethylthiophene, 3-chlorothiophene, 3,4-dichlorothiophene, and 2,3,4-trichlorothiophene Or more; more preferably t-butyl sulfide, 2,4,6-trimethylphenyl sulfide, 4,4'-thiobis(6-tert-butyl-3-methylphenol), 2- Ethylthiazole, 2,5-dichlorothiazole, 2,4,5-tri-tert-butylisothiazole, 4,5-dimethylisothiazole, 3,4-dichlorothiophene and 2,3,4-trichlorothiophene One or more of them; further preferably t-butyl sulfide, 4,4'-thiobis(6-tert-butyl-3-methylphenol), 2,4,5-tri-tert-butylisothiazole and One or more of 2,3,4-trichlorothiophene.

In some embodiments of the invention, the catalyst A is tin tetrachloride and the catalyst B is 2,5-dichlorothiazole.

In some embodiments of the invention, the catalyst A is ferric chloride and the catalyst B is tert-butyl methyl sulfide.

In certain embodiments of the invention, the catalyst A is alumina and the catalyst B is tert-butyl sulfide.

In some embodiments of the invention, the catalyst A is magnesium chloride and the catalyst B is 2,4,5-tri-tert-butylisothiazole.

In some embodiments of the invention, the catalyst A is zinc chloride and the catalyst B is 4,4'-dichlorophenyl sulfide.

In some embodiments of the invention, the catalyst A is iron oxide and the catalyst B is 2,4,6-trimethylphenyl sulfide.

In some embodiments of the invention, the catalyst A is titanium dioxide and the catalyst B is 2-ethyl thiazole.

In some embodiments of the invention, the catalyst A is lead acetate and the catalyst B is 2,3,4-trichlorothiophene.

In some embodiments of the invention, the catalyst A is titanium tetrachloride and the catalyst B is 3,4-dichlorothiophene.

In some embodiments of the invention, the catalyst A is aluminum chloride and the catalyst B is 4,4'-thiobis(6-tert-butyl-3-methylphenol).

The amount of the catalyst A used is preferably 0.05% to 1.0% by weight based on the weight of the phenoxyacetate, more preferably 0.25% to 1.0%, still more preferably 0.5% to 1.0%.

The amount of the catalyst B used is preferably 0.05% to 1.0% by weight based on the weight of the phenoxyacetate, more preferably 0.2% to 0.8%, still more preferably 0.3% to 0.5%.

The chlorinating agent may be a general chlorinating agent for phenol chlorination, preferably chlorine, thionyl chloride or sulfuryl chloride, more preferably chlorine or sulfuryl chloride.

The molar ratio of the phenoxyacetate to the chlorinating agent is preferably 1: (1.98 to 2.4), more preferably 1: (2 to 2.2), still more preferably 1: (2.02 to 2.06).

The temperature of the selective chlorination reaction is preferably -20 to 100 ° C, more preferably -20 to 60 ° C, still more preferably -20 to 20 ° C. The reaction time is preferably from 0.2 to 1 h.

After the end of the chlorination reaction, the present invention preferably distills and collects the fraction at the corresponding temperature to obtain 2,4-dichlorophenoxyacetate. The pressure of the distillation is preferably 1 KPa.

The 2,4-dichlorophenoxyacetate has the structure shown in Formula 2:

The range of R is the same as above, and will not be described here.

The acidic compound is then added to the 2,4-dichlorophenoxyacetate and the hydrolysis reaction is carried out under acidic conditions.

The acidic compound is preferably hydrochloric acid, phosphoric acid, sulfonic acid or sulfuric acid. Wherein, the sulfonic acid preferably has the formula: XSO ₃ H, X is a C1-18 alkyl group or a halogen-substituted alkyl group, a C5-18 aryl group or a halogen-substituted aryl group.

The acidic compound is preferably an aqueous solution, and its mass concentration is preferably 5% to 35%.

The amount of the acidic compound used is 0.4 to 1 times the weight of 2,4-dichlorophenoxyacetate.

The temperature of the hydrolysis reaction is preferably 60 to 120 ° C, more preferably 80 to 100 ° C; and the time of the hydrolysis reaction is preferably 2 to 4 hours.

In the process of the hydrolysis reaction, the alcohol formed by the reaction is simultaneously distilled off, and the reaction is cooled to room temperature, and the filter cake is washed by adding a small amount of water, and the filter cake is dried to obtain 2,4-dichlorophenoxyacetic acid, and the content is ≥98.5. %, total yield ≥ 98%, water wash water and filtrate can be combined and reused.

The impurities and impurity contents of 2,4-dichlorophenoxyacetic acid prepared by the present invention are shown in Table 1 below:

Table 1 Summary of impurities and impurities of 2,4-dichlorophenoxyacetic acid prepared by the present invention

The invention also provides a preparation method of 2,4-dichlorophenoxyacetic acid salt, comprising the following steps:

S1) phenol and chloroacetate are reacted under basic conditions to obtain phenoxyacetate;

S2) phenoxyacetate under the action of catalyst A and catalyst B, and selective chlorination with a chlorinating agent to obtain 2,4-dichlorophenoxyacetate;

The catalyst A is a Lewis acid;

The catalyst B is a C5-22 thioether, thiazole, isothiazole, thiophene or a halogenated derivative thereof;

SS3) 2,4-dichlorophenoxyacetate is mixed with a basic compound to carry out an alkali hydrolysis reaction to obtain an alkali metal salt or an amine salt of 2,4-dichlorophenoxyacetic acid.

The 2,4-dichlorophenoxyacetate is first prepared by the above method, and then a basic compound is added to carry out an alkali hydrolysis reaction.

The basic compound is preferably one or more of sodium hydroxide, potassium hydroxide, sodium hydrogencarbonate, sodium carbonate, potassium hydrogencarbonate, potassium carbonate, ammonium hydrogencarbonate, ammonium carbonate, ammonia, and an organic amine; more preferably One or more of sodium hydroxide, potassium hydroxide, sodium hydrogencarbonate, sodium carbonate, potassium hydrogencarbonate, potassium carbonate, dimethylamine and choline.

When the basic compound is a monobasic base, the molar ratio of the 2,4-dichlorophenoxyacetate to the basic compound is preferably 1: (1 to 1.2), more preferably 1: (1 to 1.1), further Preferably, it is 1: (1.02 to 1.06); when the basic compound is a dibasic base, the molar ratio of the 2,4-dichlorophenoxyacetate to the basic compound is preferably 1: (0.5 to 0.6), more Preferably, it is 1: (0.5 to 0.55), and further preferably 1: (0.51 to 0.53).

The temperature of the alkaline hydrolysis reaction is preferably from 60 to 120 ° C, more preferably from 80 to 100 ° C. The time of the alkaline hydrolysis reaction is preferably from 2 to 4 hours.

In the process of the alkaline hydrolysis reaction, the alcohol formed by the reaction is simultaneously distilled off, and the reaction is cooled to room temperature to obtain an alkali solution. When the basic compound used is an alkali metal compound, the reaction system is filtered, and the filter cake is dried to obtain an alkali metal salt of 2,4-dichlorophenoxyacetic acid, the content is ≥98.5%, and the mother liquor can be reused; When the basic compound used is ammonium hydrogencarbonate, ammonium carbonate, ammonia or an organic amine, the alkaline solution is a 2,4-dichlorophenoxyacetic acid amine salt. The total yield of 2,4-dichlorophenoxyacetate is ≥98% based on phenol.

Compared with the prior art, the present invention provides a preparation method of 2,4-dichlorophenoxyacetic acid, comprising the following steps: S1) phenol and chloroacetate are reacted under alkaline conditions to obtain phenoxyethyl b. Acidic acid; S2) phenoxyacetate under the action of catalyst A and catalyst B, and selective chlorination with a chlorinating agent to obtain 2,4-dichlorophenoxyacetate; the catalyst A is Lewis The catalyst B is a C5-22 thioether, a thiazole, an isothiazole, a thiophene or a halogenated derivative thereof; and the S3) 2,4-dichlorophenoxyacetate is subjected to a hydrolysis reaction under acidic conditions to obtain 2,4-Dichlorophenoxyacetic acid.

The invention also provides a preparation method of 2,4-dichlorophenoxyacetic acid salt, comprising the steps of: S1) reacting phenol and chloroacetate under alkaline conditions to obtain phenoxyacetate; S2 The phenoxyacetate is subjected to selective chlorination with a chlorinating agent under the action of a catalyst A and a catalyst B to obtain 2,4-dichlorophenoxyacetate; the catalyst A is a Lewis acid; Catalyst B is a C5-22 thioether, thiazole, isothiazole, thiophene or a halogenated derivative thereof; SS3) 2,4-dichlorophenoxyacetate is mixed with a basic compound to carry out an alkali hydrolysis reaction to obtain 2 An alkali metal or amine salt of 4-dichlorophenoxyacetic acid.

The invention effectively avoids the formation and use of 2,4-dichlorophenol with unpleasant odor, fundamentally eliminates the production of highly toxic dioxins, and greatly improves product quality and operation at the production site. surroundings. The invention uses phenol as a raw material, and obtains high-yield, high-quality 2,4-dichlorophenoxyacetic acid or a salt thereof by condensation, selective chlorination and acid hydrolysis/alkalilysis. And effectively avoiding the loss of active ingredients and increasing the yield of the product. And effectively eliminate the production of high COD, high-salt wastewater, while the output of waste salt (metal chloride) is reduced by more than 50%, and the output of the three wastes has been greatly reduced.

DRAWINGS

Fig. 1 is a nuclear magnetic resonance spectrum of 2,4-dichlorophenoxyacetic acid obtained in Example 1 of the present invention.

detailed description

In order to further illustrate the present invention, a method for preparing 2,4-dichlorophenoxyacetic acid and a salt thereof provided by the present invention will be described in detail below with reference to examples.

Example 1

To 95.06 g of 99% phenol, 42.83 g of 99% sodium hydroxide and 142.59 g of xylene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 116.20 g of 99% methyl chloroacetate was added dropwise thereto at 90 ° C. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 40 ° C, filtered, and an appropriate amount of xylene is added to wash the filter cake, and then dried to obtain sodium chloride and methyl phenoxyacetate containing xylene, and distilled and recovered. Toluene also obtained 172.02 g of methyl phenoxyacetate with a content of 96.1%.

To the methyl phenoxyacetate obtained by distillation, 1.72 g of 99% tin tetrachloride and 0.60 g of 99% 2,5-dichlorothiazole were added, and 279.41 g of 99% sulfuryl chloride was added at 60 ° C to react, and the addition was completed. The reaction was kept at this temperature for 0.5 h, and distilled at a pressure of 1 kPa to collect a fraction of 115 to 125 ° C to obtain 234.12 g of methyl 2,4-dichlorophenoxyacetate, and the content was 99.18%.

Add 780.40g of 30% hydrochloric acid to methyl 2,4-dichlorophenoxyacetate, and digest the reaction at 110 ° C for 4 h, while distilling off the alcohol formed by the reaction. After the reaction is cooled, it is filtered to room temperature and washed with a small amount of water. The cake and the filter cake were dried to obtain 219.46 g of 2,4-dichlorophenoxyacetic acid, the content was 98.8%, and the total yield was 98.07% based on phenol.

After testing, the impurity content is as follows: 4-chlorophenoxyacetic acid content 0.06%, 2,6-dichlorophenoxyacetic acid content 0.09%, 2,4,6-trichlorophenoxyacetic acid 0.12%, 2,5-two Chlorothiazole 0.02%.

1 embodiment of a nuclear magnetic resonance obtained in Example 2,4-dichlorophenoxyacetic acid analysis, hydrogen nuclear magnetic resonance spectrum which is obtained ^{(1 HNMR (DMSO-d6)} ), as shown in FIG.

Example 2

To 95.06 g of 99% phenol, 69.80 g of 99% potassium carbonate and 95.06 g of toluene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 152.14 g of 99% n-butyl chloroacetate was added thereto at 120 ° C to make it. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 30 ° C, filtered, and an appropriate amount of toluene is added to wash the filter cake, and then dried to obtain potassium chloride and n-butyl phenoxyacetate containing toluene, and toluene is distilled off simultaneously. The obtained n-butyl phenoxyacetate was 216.31 g, and the content was 95.9%.

To the n-butyl phenoxyacetate, 0.97 g of 99% ferric chloride and 1.41 g of 99% t-butyl methyl sulfide were added, and 236.92 g of 99% thionyl chloride was added dropwise at 40 ° C to react. The temperature was kept at this temperature for 0.5 h, and distilled at a pressure of 1 kPa to collect a fraction of 130 to 140 ° C to obtain 277.41 g of n-butyl 2,4-dichlorophenoxyacetate, and the content was 99.01%.

Add 1479.50g of 15% hydrochloric acid to n-butyl 2,4-dichlorophenoxyacetate, and digest the reaction at 60 ° C for 4 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature and adding a small amount of water to wash. The filter cake and the filter cake were dried to obtain 222.11 g of 2,4-dichlorophenoxyacetic acid, the content was 98.5%, and the total yield was 98.62% based on phenol.

Example 3

To 95.06 g of 99% phenol, 91.65 g of 99% sodium hydrogencarbonate and 427.77 g of toluene were added, and the mixture was heated to reflux to dehydrate to ≤0.5%, and 164.31 g of 99% isobutyl chloroacetate was added dropwise thereto at 80 ° C to make it After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 50 ° C, filtered, and an appropriate amount of toluene is added to wash the filter cake, and then dried to obtain sodium chloride and isobutyl phenoxyacetate containing toluene, and toluene is distilled off simultaneously. The obtained isobutyl phenoxyacetate was 215.73 g, and the content was 96.0%.

To the isobutyl phenoxyacetate obtained by distillation, 1.62 g of 99% alumina and 0.11 g of 99% tert-butyl sulfide were added, and 153.77 g of 99% chlorine gas was introduced at 100 ° C to react. The reaction was kept at a temperature for 0.5 h, and distilled at a pressure of 1 kPa to collect a fraction of 130 to 140 ° C to obtain 278.08 g of 2,4-dichlorophenoxyacetic acid isobutyl ester, and the content was 98.77%.

Adding 778.62g of 25% phosphoric acid to isobutyl 2,4-dichlorophenoxyacetate, acidifying at 80 ° C for 3 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature and adding a small amount of water to wash The filter cake and the filter cake were dried to obtain 220.26 g of 2,4-dichlorophenoxyacetic acid, the content was 98.6%, and the total yield was 98.29% based on phenol.

Example 4

To 95.06 g of 99% phenol, 31.22 g of 99% magnesium hydroxide and 285.18 g of benzene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 221.36 g of 99% of isooctyl chloroacetate was added thereto at 100 ° C to make it. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 40 ° C, filtered, and an appropriate amount of benzene washing filter cake is added to dry the magnesium chloride and the crude phenoxyacetate containing benzene, and the benzene is distilled to obtain benzene. The isooctyl oxyacetate was 272.78 g, and the content was 96.1%.

Add 1.77g of 99% magnesium chloride and 0.41g of 99% 2,4,5-tri-tert-butylisothiazole to isooctyl phenoxyacetate, and add 170.45g of 99% chlorine gas at -20 °C to react. After the temperature was kept at this temperature for 0.5 h, the fraction was distilled at a pressure of 1 kPa and a fraction of 150 to 160 ° C was collected to obtain 332.50 g of 2,4-dichlorophenoxyacetic acid isooctyl ester, and the content was 98.89%.

Add 1330.01g of 10% sulfuric acid to isooctyl 2,4-dichlorophenoxyacetate, and acidify at 100 ° C for 2 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature and adding a small amount of water to wash. The filter cake and the filter cake were dried to obtain 21.9-dichlorophenoxyacetic acid (219.61 g), the content was 98.8%, and the total yield was 98.15% based on phenol.

Example 5

To 95.06 g of 99% phenol, 55.67 g of 99% sodium carbonate and 237.65 g of xylene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 128.75 g of 99% ethyl chloroacetate was added dropwise thereto at 60 ° C to react. After the dropwise addition is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 40 ° C, filtered, and an appropriate amount of xylene is added to wash the filter cake, and then dried to obtain sodium chloride and a crude ethyl phenoxyacetate containing xylene, and the xylene is distilled off. At the same time, 185.99 g of ethyl phenoxyacetate was obtained, and the content was 96.2%.

To the ethyl phenoxyacetate, 1.58 g of 99% zinc chloride and 1.02 g of 99% 4,4'-dichlorophenyl sulfide were added, and 273.43 g of 99% sulfuryl chloride was added dropwise at 30 ° C to cause a reaction. After the addition, the reaction was kept at this temperature for 0.5 h, and distilled at a pressure of 1 kPa to collect a fraction of 120 to 130 ° C to obtain 248.47 g of ethyl 2,4-dichlorophenoxyacetate, and the content was 99.12%.

Adding 745.40g of 20% phosphoric acid to ethyl 2,4-dichlorophenoxyacetate, acidifying at 120 ° C for 3 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature and filtering with a small amount of water. The cake and the filter cake were dried to obtain 220.08 g of 2,4-dichlorophenoxyacetic acid, the content was 98.9%, and the total yield was 98.45% based on phenol.

Example 6

To 95.06 g of 99% phenol, 64.20 g of 90% potassium hydroxide and 475.30 g of xylene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 142.11 g of 99% isopropyl chloroacetate was added dropwise thereto at 70 °C. The reaction is carried out, the reaction is completed at this temperature for 0.5 h, the temperature is lowered to 30 ° C, filtered, and an appropriate amount of xylene is added to wash the filter cake, and then dried to obtain potassium chloride and a crude phenoxyacetate containing xylene. Dioxane was recovered by distillation to obtain 201.27 g of isopropyl phenoxyacetate in an amount of 96.0%.

0.30 g of 99% iron oxide and 1.71 g of 99% 2,4,6-trimethylphenyl sulfide were added to isopropyl phenoxyacetate, and 156.80 g of 99% chlorine gas was introduced at 0 ° C to react. After the addition, the reaction was kept at this temperature for 0.5 h, and distilled at a pressure of 1 kpa to collect a fraction of 125 to 135 ° C to obtain 262.17 g of isopropyl 2,4-dichlorophenoxyacetate, and the content was 99.29%.

To 2, 4-dichlorophenoxyacetic acid isopropyl ester, 2097.38 g of 5% sulfuric acid was added, and the reaction was acid-decomposed at 90 ° C for 2 h, and the alcohol formed by the reaction was distilled off. The reaction was cooled to room temperature and filtered with a small amount of water. The filter cake and the filter cake were dried to obtain 220.21 g of 2,4-dichlorophenoxyacetic acid, the content was 98.7%, and the total yield was 98.34% based on phenol.

Example 7

To 95.06 g of 99% phenol, 105.18 g of 99% potassium hydrogencarbonate and 190.12 g of toluene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 172.97 g of 99% of n-amyl chloroacetate was added dropwise thereto at 90 ° C. The reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 50 ° C, filtered, and an appropriate amount of toluene is added to wash the filter cake, and then the potassium chloride and the crude phenoxyacetate containing toluene are distilled to obtain toluene. At the same time, 231.30 g of n-pentyl phenoxyacetate was obtained, and the content was 95.8%.

1.27 g of 99% titanium dioxide and 0.58 g of 99% 2-ethylthiazole were added to n-pentyl phenoxyacetate, and 171.34 g of 99% chlorine gas was introduced at 50 ° C to react, and the temperature was kept at this temperature. The reaction was carried out for 0.5 h, and distilled at a pressure of 1 kPa to collect a fraction of 135 to 145 ° C to obtain 290.54 g of n-pentyl 2,4-dichlorophenoxyacetate in an amount of 99.08%.

Adding 122.61 g of 40% dimethylamine to n-amyl 2,4-dichlorophenoxyacetate, reacting at 100 ° C for 3 h, distilling off the alcohol formed by the reaction, and cooling to room temperature to obtain 2,4-di The dimethylphenoxyacetic acid dimethylamine salt was 319.87 g, the content was 81.6%, and the total yield was 98.03% based on phenol.

Example 8

To 95.06 g of 99% phenol, 40.42 g of 99% calcium hydroxide and 332.71 g of toluene were added, and the mixture was heated to reflux to dehydrate to ≤0.5%, and 256.15 g of 99% chloroacetic acid n-decyl ester was added dropwise thereto at 80 ° C. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 30 ° C, filtered, and an appropriate amount of toluene is added to wash the filter cake, and then the calcium chloride and the crude phenoxyacetate containing toluene are distilled to obtain toluene. The phenoxyacetic acid n-decyl ester was 303.29 g, and the content was 95.9%.

0.15 g of 99% lead acetate and 2.27 g of 99% 2,3,4-trichlorothiophene were added to n-decyl phenoxyacetate, and 236.68 g of 99% thionyl chloride was added dropwise at 20 ° C to react. After the temperature was kept at this temperature for 0.5 h, the fraction was distilled at a pressure of 1 kPa and a fraction of 160-170 ° C was collected to obtain 361.77 g of n-nonyl 2,4-dichlorophenoxyacetate with a content of 98.84%.

To the n-decyl 2,4-dichlorophenoxyacetate, 100.77 g of 99% sodium hydrogencarbonate and 151.16 g of water were added, and the mixture was reacted at 80 ° C for 2 h, and the alcohol formed by the reaction was distilled off, and the reaction was cooled to room temperature and filtered. The filter cake was dried to obtain 242.67 g of sodium 2,4-dichlorophenoxyacetate, the content was 98.6%, and the total yield was 98.44% based on phenol.

Example 9

To 95.06 g of 99% phenol, 116.88 g of 48% potassium hydroxide and 190.12 g of benzene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 194.66 g of 99% of n-heptyl chloroacetate was added dropwise thereto at 110 ° C. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 40 ° C, filtered, and an appropriate amount of benzene washing filter cake is added to dry the potassium chloride and the benzene-containing phenoxyacetic acid n-heptyl ester to obtain benzene. 258.41 g of n-heptyl phenoxyacetate was obtained, and the content was 96.1%.

Add 0.90 g of 99% titanium tetrachloride and 2.58 g of 99% 3,4-dichlorothiophene to n-heptyl phenoxyacetate, and add 273.29 g of 99% sulfuryl chloride dropwise at 70 ° C to react. After the temperature was kept at this temperature for 0.5 h, the fraction of 145-155 ° C was distilled under a pressure of 1 kPa to obtain 317.77 g of n-heptyl 2,4-dichlorophenoxyacetate, and the content was 98.94%.

Add 123.10g of 32% sodium hydroxide to n-heptyl 2,4-dichlorophenoxyacetate, and digest the reaction at 60 ° C for 4 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature, filtering cake The sodium salt of 2,4-dichlorophenoxyacetic acid was dried to obtain 241.32 g, the content was 98.8%, and the total yield was 98.12% based on phenol.

Example 10

To 95.06 g of 99% phenol, 127.50 g of 32% sodium hydroxide and 380.24 g of toluene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 184.09 g of 99% chlorohexyl chloroacetate was added dropwise thereto at 100 ° C. The reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 50 ° C, and the filter cake is washed with an appropriate amount of toluene, and then dried to obtain sodium chloride and a crude phenoxyacetate containing toluene, and toluene is distilled off. At the same time, 243.76 g of cyclohexyl phenoxyacetate was obtained, and the content was 96.3%.

To the cyclohexyl phenoxyacetate, 0.61 g of 99% aluminum chloride and 1.10 g of 99% 4,4'-thiobis(6-tert-butyl-3-methylphenol) were added and dropped at 80 ° C. 278.99 g of 99% sulfuryl chloride was added to react, and the reaction was kept at this temperature for 0.5 h, and distilled at a pressure of 1 kPa to collect a fraction of 140 to 150 ° C to obtain cyclohexyl 2,4-dichlorophenoxyacetate. 303.96g, content 99.09%.

To the cyclohexyl 2,4-dichlorophenoxyacetate, 79.90 g of 99% potassium carbonate and 119.85 g of water were added, and the reaction was carried out at 120 ° C for 4 h, while the alcohol formed by the reaction was distilled off, and the reaction was cooled to room temperature and filtered. The cake was dried to obtain 256.53 g of potassium salt of 2,4-dichlorophenoxyacetate, the content was 99.0%, and the total yield was 98.03% based on phenol.

Comparative example 1

To 95.06 g of 99% phenol, 116.88 g of 48% potassium hydroxide and 190.12 g of benzene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 194.66 g of 99% of n-heptyl chloroacetate was added dropwise thereto at 110 ° C. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 40 ° C, filtered, and an appropriate amount of benzene washing filter cake is added to dry the potassium chloride and the benzene-containing phenoxyacetic acid n-heptyl ester to obtain benzene. 258.41 g of n-heptyl phenoxyacetate was obtained, and the content was 96.1%.

0.90 g of 99% titanium tetrachloride was added to n-heptyl phenoxyacetate, and 273.29 g of 99% sulfuryl chloride was added dropwise at 70 ° C to react, and the reaction was kept at this temperature for 0.5 h under a pressure of 1 kpa. The fraction of 145 to 155 ° C was distilled and collected to obtain 318.63 g of n-heptyl 2,4-dichlorophenoxyacetate, and the content was 91.02%.

Add 123.10g of 32% sodium hydroxide to n-heptyl 2,4-dichlorophenoxyacetate, and digest the reaction at 60 ° C for 4 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature, filtering cake The sodium salt of 2,4-dichlorophenoxyacetic acid was dried to obtain 236.84 g, the content was 93.7%, and the total yield was 91.31% based on phenol.

Comparative example 2

To 95.06 g of 99% phenol, 31.22 g of 99% magnesium hydroxide and 285.18 g of benzene were added, and the mixture was refluxed and dehydrated to a water content of ≤0.5%, and 221.36 g of 99% of isooctyl chloroacetate was added thereto at 100 ° C to make it. After the reaction is completed, the reaction is kept at this temperature for 0.5 h, the temperature is lowered to 40 ° C, filtered, and an appropriate amount of benzene washing filter cake is added to dry the magnesium chloride and the crude phenoxyacetate containing benzene, and the benzene is distilled to obtain benzene. The isooctyl oxyacetate was 272.78 g, and the content was 96.1%.

0.41 g of 99% 2,4,5-tri-tert-butylisothiazole was added to isooctyl phenoxyacetate, and 170.45 g of 99% chlorine gas was introduced at -20 ° C to react, and the reaction was completed at this temperature. After 0.5 h, the mixture was distilled at a pressure of 1 kPa and a fraction of 150 to 160 ° C was collected to obtain 334.91 g of isooctyl 2,4-dichlorophenoxyacetate, and the content was 90.63%.

Add 1330.01g of 10% sulfuric acid to isooctyl 2,4-dichlorophenoxyacetate, and acidify at 100 ° C for 2 h, while distilling off the alcohol formed by the reaction, cooling the reaction to room temperature and adding a small amount of water to wash. The filter cake and the filter cake were dried to obtain 220.55 g of 2,4-dichlorophenoxyacetic acid, the content was 90.3%, and the total yield was 90.11% based on phenol.

It can be seen from the above examples that the preparation method provided by the present invention has high yield and purity.

The above description of the embodiments is merely to assist in understanding the method of the present invention and its core idea. It should be noted that those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the invention.

Claims (10)

1. A method for preparing 2,4-dichlorophenoxyacetic acid, comprising the steps of:

   S1) phenol and chloroacetate are reacted under basic conditions to obtain phenoxyacetate;

   S2) phenoxyacetate under the action of catalyst A and catalyst B, and selective chlorination with a chlorinating agent to obtain 2,4-dichlorophenoxyacetate;

   The catalyst A is a Lewis acid;

   The catalyst B is a C5-22 thioether, thiazole, isothiazole, thiophene or a halogenated derivative thereof;

   S3) 2,4-Dichlorophenoxyacetate is subjected to a hydrolysis reaction under acidic conditions to obtain 2,4-dichlorophenoxyacetic acid.
2. A method for preparing 2,4-dichlorophenoxyacetate comprises the following steps:

   S1) phenol and chloroacetate are reacted under basic conditions to obtain phenoxyacetate;

   S2) phenoxyacetate under the action of catalyst A and catalyst B, and selective chlorination with a chlorinating agent to obtain 2,4-dichlorophenoxyacetate;

   The catalyst A is a Lewis acid;

   The catalyst B is a C5-22 thioether, thiazole, isothiazole, thiophene or a halogenated derivative thereof;

   SS3) 2,4-dichlorophenoxyacetate is mixed with a basic compound to carry out an alkali hydrolysis reaction to obtain an alkali metal salt or an amine salt of 2,4-dichlorophenoxyacetic acid.
3. The preparation method according to claim 1 or 2, wherein the catalyst A is SnCl ₄ , MgCl ₂ , FeCl ₃ , AlCl ₃ , BF ₃ , ZnCl ₂ , TiCl ₄ , SbF ₅ , Al ₂ O ₃ , One or more of Fe ₂ O ₃ , TiO ₂ , Pb(OAc) ₂ , Zn(OAc) ₂ and Al ₂ O(OAc) ₄ .
4. The preparation method according to claim 1 or 2, wherein the catalyst B is tert-butyl methyl sulfide, t-butyl sulfide, phenyl sulfide, 4,4'-dichlorophenyl sulfide, 2- Methyl phenyl sulfide, 2,4,6-trimethyl phenyl sulfide, 4,4'-thiobis(6-tert-butyl-3-methylphenol), thiazole, 2-ethylthiazole, 2 , 5-dichlorothiazole, 4-methylthiazole, 2-tert-butylthiazole, isothiazole, 4,5-dimethylisothiazole, 5-chloroisothiazole, 2,4,5-tri-tert-butylisothiazole, One or more of thiophene, 2-methylthiophene, 2,5-dimethylthiophene, 3-chlorothiophene, 3,4-dichlorothiophene, and 2,3,4-trichlorothiophene.
5. The preparation method according to claim 1 or 2, wherein the catalyst A is used in an amount of 0.05% to 1.0% by weight based on the phenoxyacetate; and the catalyst B is used in an amount of phenoxyacetate. 0.05% to 1.0%.
6. The preparation method according to claim 1 or 2, wherein the step S1) is specifically: mixing phenol and a basic compound in an organic solvent, and heating and refluxing to a water content of ≤0.5%, followed by chloroacetic acid The ester is mixed and reacted to obtain phenoxyacetate.
7. The preparation method according to claim 6, wherein the basic compound is sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium carbonate and potassium carbonate. Any one or more of

   The organic solvent is any one or more of benzene, toluene and xylene.
8. The preparation method according to claim 1 or 2, wherein the step S2) is specifically:

   The phenoxyacetate is subjected to selective chlorination with a chlorinating agent by the action of the catalyst A and the catalyst B, and is distilled to obtain 2,4-dichlorophenoxyacetate.
9. The preparation method according to claim 1 or 2, wherein the reaction temperature of the step S1) is 60 to 120 ° C, and the time is 0.2 to 1 h; and the temperature of the selective chlorination reaction is -20 to 100. °C, the time is 0.2 ~ 1h.
10. The preparation method according to claim 2, wherein the basic compound is sodium hydroxide, potassium hydroxide, sodium hydrogencarbonate, sodium carbonate, potassium hydrogencarbonate, potassium carbonate, ammonium hydrogencarbonate, ammonium carbonate, ammonia. Or one or more of organic amines.

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