Preparation method of 2,4-dichlorophenoxyacetic acid by composite molecular sieve ZSM-5 catalysis synthesis and preparation method of water-reducing process

Abstract

The application discloses a preparation method of 2,4-dichlorophenoxyacetic acid synthesized by composite molecular sieve ZSM-5 and a water-reducing process, and relates to the following steps: under alkaline conditions, 2,4-dichlorophenol is reacted with a sodium chloroacetate solution under the catalysis of a composite molecular sieve catalyst to obtain 2,4-dichlorophenoxyacetic acid sodium salt crude product through condensation; and then hydrolysis and hydrochloric acid acidification are carried out to obtain 2,4-dichlorophenoxyacetic acid product. The process can reduce energy consumption, shorten reaction time and reduce production cost in obtaining 2,4-dichlorophenoxyacetic acid, and can improve the conversion rate and yield of the product and the color of the product. When a new batch of 2,4-dichlorophenoxyacetic acid sodium salt crude product is dissolved in the acidification reaction, the washing water of the last batch of 2,4-dichlorophenoxyacetic acid is used as the solvent reaction liquid, and the washing water of the last batch is used for the first water washing of the final product and is used in turn. The water consumption is reduced, the wastewater treatment cost is reduced, the conversion rate and yield of the product are improved, the product has high purity, the process is simple, the conditions are mild, and the raw materials can be recycled.

Description

Technical Field

[0001] This invention discloses a method for the catalytic synthesis of 2,4-dichlorophenoxyacetic acid using composite molecular sieve ZSM-5 and a water-reducing process, belonging to the field of chemical production technology, and particularly relating to a novel composite molecular sieve ZSM-5 catalytic synthesis method for 2,4-dichlorophenoxyacetic acid and its water-reducing process. Background Technology

[0002] 2,4-D, chemically known as 2,4-dichlorophenoxyacetic acid, is a herbicide belonging to the phenoxycarboxylic acid class. It is a widely used plant growth regulator and herbicide. 2,4-D, its salts, and esters are highly efficient, systemic, and selective, primarily used in vegetables, fruit trees, grain crops, and other cash crops. It can improve fruit quality and extend shelf life, and can also control broadleaf weeds such as barnyard grass and grasses. In grain production, it is used to control broadleaf weeds. Furthermore, 2,4-D has advantages over other herbicides, such as safety, low toxicity, low pollution, and easy degradation. To this day, 2,4-D remains one of the most widely used herbicides in the world.

[0003] In recent years, due to environmental pressures, the current production and synthesis methods of 2,4-D products still suffer from low atom utilization and increasingly prominent pollution problems such as wastewater, waste gas, and waste residue. In response to public calls, the government has taken measures to forcibly eliminate old production processes that generate large amounts of phenol-containing wastewater and has issued mandatory rectification orders to relevant enterprises. However, issues such as inconsistent product quality and the inability to meet the industry's vision of green production and environmental friendliness persist. Therefore, it is necessary to develop a new synthesis method to permanently solve the problems in 2,4-D production, providing guidance for environmental protection, reducing wastewater consumption, improving product yield, and enhancing product market competitiveness.

[0004] This paper uses chlorine gas as a raw material to directionally obtain 2,4-dichlorophenol through catalysis. Using 2,4-dichlorophenol and chloroacetic acid as raw materials, a composite molecular sieve catalyst is added to the reaction system under alkaline conditions to obtain sodium 2,4-dichlorophenoxyacetic acid through a condensation reaction. The wastewater generated in the process can be reused in the reaction solution of the next batch of condensation reaction. Subsequently, the sodium 2,4-dichlorophenoxyacetic acid solution is acidified with hydrochloric acid to obtain 2,4-dichlorophenoxyacetic acid (referred to as "2,4-drop") product. The wastewater generated in the acidification process is reused in the reaction solution of the next batch of reaction. This process has high atom utilization, high product yield, high quality, and the synthesis process can be applied to large-scale industrial production. Summary of the Invention

[0005] The problem to be solved by this invention is to provide a method for the synthesis of 2,4-dichlorophenoxyacetic acid catalyzed by composite molecular sieve ZSM-5 and the preparation method using a water-reducing process. In order to solve the above problem;

[0006] A method for synthesizing 2,4-dichlorophenoxyacetic acid using composite molecular sieve ZSM-5 catalysis and a water-reducing process is disclosed. This method utilizes a composite molecular sieve catalyst, which offers advantages such as high catalytic efficiency, no equipment corrosion, high reactivity, and no environmental pollution. Furthermore, wastewater can be reused and its usage reduced. The method is simple to operate, the reaction is mild, energy consumption is reduced, and the yield is high. The specific operating steps to achieve the above objectives are as follows:

[0007] (1) Under alkaline conditions, 2,4-dichlorophenol was condensed with sodium chloroacetate solution under the catalysis of composite molecular sieve ZSM-5 to obtain crude sodium 2,4-dichlorophenoxyacetate (abbreviated as: 2,4-dichlorophenol sodium salt).

[0008] (2) The obtained sodium 2,4-dichlorophenoxyacetic acid salt was washed with water and dried to obtain solid sodium 2,4-dichlorophenoxyacetic acid salt;

[0009] (3) Step (2) 2,4-Dichlorophenoxyacetic acid sodium salt solid is dissolved in water, acidified with hydrochloric acid, washed with water and dried to obtain 2,4-dichlorophenoxyacetic acid product.

[0010] In step (1), chloroacetic acid is used as the initial raw material, and sodium hydroxide solution is directly added to solid chloroacetic acid to dissolve and obtain sodium chloroacetate solution; 2,4-dichlorophenol and sodium hydroxide are used as raw materials to react the two to generate sodium 2,4-dichlorophenol solution.

[0011] The molar ratio of chloroacetic acid to sodium hydroxide solution is 1:(1.10-2.25), and the reaction is carried out at a temperature of 20-35℃ for 0.5-1 hours for neutralization.

[0012] In step (1), the alkaline conditions are achieved by adding sodium hydroxide. The molar ratio of sodium chloroacetate: 2,4-dichlorophenol: sodium hydroxide: water is 1:0.5-3.0:0.2-3.0:0.2-1:. The composite molecular sieve ZSM-5 catalyst is added to the reaction system. The catalysts selected are Fe3O4-ZSM-5, Fe-ZSM-5, MnO2-ZSM-5, etc. The reaction is carried out at 100-105℃ for condensation for 2-4 hours. After the reaction is completed, the temperature is kept at 100-110℃ for 2-5 hours.

[0013] In step (3), the mass ratio of sodium 2,4-dichlorophenoxyacetic acid solid to water is 1:1.5-3.5; the mass ratio of sodium 2,4-dichlorophenoxyacetic acid to water is 1:(1.5-3.5); during the hydrochloric acid acidification process, the mass concentration of hydrochloric acid is 20-35%; the molar ratio of sodium 2,4-dichlorophenoxyacetic acid to hydrochloric acid is 1:1.0-1.5, the acidification is carried out at a reaction temperature of 90-115℃ for 0.5-2 hours, and the pH value is 0.5-1.5 after the acidification reaction is completed.

[0014] In step (2), the washing water from the previous batch is reused in the new batch of condensation reaction. The washing water of sodium 2,4-dichlorophenoxyacetic acid is added to the new batch of condensation reaction according to the mass ratio of 2,4-dichlorophenol to water of 1:0.2-1. The composite molecular sieve ZSM-5 catalyst (such as Fe3O4-ZSM-5, Fe-ZSM-5, MnO2-ZSM-5, etc.) is added to the reaction system. The reaction temperature is 100-105℃, the reaction time is 2-4 hours, and after the reaction is completed, the temperature is kept at 100-110℃ for 2-5 hours.

[0015] The water used for acidification and washing in step (3) is reused as a solvent and washing water in the new batch of synthesis step (3). The mass ratio of crude sodium 2,4-dichlorophenoxyacetate to water is 1:1.5-3.5.

[0016] The chemical reaction process in the above technical solution is as follows:

[0017] Main reaction:

[0018] Side reaction: ClCH2COONa + NaOH → HOCH2COONa + NaCl

[0019] Compared with existing technologies, the outstanding advantages of this invention are:

[0020] 1. Directly adding sodium hydroxide to chloroacetic acid can reduce energy consumption by more than 30% and shorten the production time by 1-2 hours. The wastewater from sodium 2,4-dichlorophenoxyacetic acid salt and 2,4-dichlorophenoxyacetic acid generated during the production process can be recycled, reducing water consumption, reusing wastewater, and lowering wastewater treatment costs.

[0021] 2. During the reaction, the product conversion rate and yield are greatly improved after being catalyzed by the composite molecular sieve catalyst. Moreover, the composite molecular sieve catalyst has the advantages of high stability, high reactivity, no environmental pollution, no equipment corrosion, and is easy to recover.

[0022] 3. The synthesis process reduces energy consumption, simplifies operation, and is mild, economical, environmentally friendly, and clean, while also reducing product production costs and increasing economic value. Detailed Implementation

[0023] To further illustrate the present invention, the following embodiments are provided to further explain the substantive content of the present invention, but these embodiments are not intended to limit the present invention:

[0024] A method for synthesizing 2,4-dichlorophenoxyacetic acid using composite molecular sieve ZSM-5 catalysis and a water-reducing process is disclosed. This method utilizes a composite molecular sieve catalyst, which offers advantages such as high catalytic efficiency, no equipment corrosion, high reactivity, and no environmental pollution. Furthermore, wastewater can be reused and its usage reduced. The method is simple to operate, the reaction is mild, energy consumption is reduced, and the yield is high. The specific operating steps to achieve the above objectives are as follows:

[0025] Three methods for preparing composite catalysts are listed. A Fe3O4-ZSM-5 catalyst was synthesized using a hydrothermal method. The specific preparation process is as follows: 1 g of FeCl3·6H2O was added to ethanol and stirred with a magnetic stirrer at 25°C for 40 min. Then, 0.5 g of ZSM-5 molecular sieve and 4.5 g of sodium acetate were added, and stirring was continued vigorously for another 40 min. The suspension was then transferred to an autoclave and heated under hydrothermal conditions at 200°C for 6 h. Subsequently, the mixture of Fe3O4 solution and ZSM-5 molecular sieve was pretreated with ultrasound for a period of time, followed by reaction at 100°C for 3 h. The mixture was then filtered, washed three times with deionized water, and dried overnight at 60°C to obtain the Fe3O4-ZSM-5 composite catalyst.

[0026] The mixture of Fe(NO3)3·9H2O solution and ZSM-5 molecular sieve was pretreated in ultrasound for a period of time, then reacted at 100℃ for 3 h, filtered, washed three times with deionized water, dried at 100℃ overnight, and finally calcined at 500℃ in static air for 4 h to obtain the Fe-ZSM-5 composite catalyst.

[0027] The hydrothermal synthesis of the MnO2-ZSM-5 catalyst was carried out as follows: KMnO4 was added to 80 mL of ethanol and ultrasonically stirred at room temperature (25 °C) until completely dissolved. 1.02 g of ZSM-5 molecular sieve and 0.6 g of sodium acetate were added, and the mixture was stirred vigorously for 30 min. The mixture was transferred to a 100 mL polytetrafluoroethylene reactor and kept at 120 °C for 3 h in an oven. After cooling to room temperature, the precipitate was collected and washed alternately with deionized water and ethanol, followed by centrifugation three times. The precipitate was dried at 80 °C for 12 h and finally calcined at 500 °C in air for 2 h to obtain the MnO2-ZSM-5 composite material.

[0028] Example 1

[0029] Mix 94.5g of chloroacetic acid and 36g of water and stir until the chloroacetic acid is completely dissolved. Control the temperature at 20-35℃, then add 125g of 32% sodium hydroxide aqueous solution and react for 0.5-1 hour to obtain sodium chloroacetate solution.

[0030] Mix 163g of 2,4-dichlorophenol and 125g of 32% sodium hydroxide aqueous solution and stir. Heat the mixture to 80-95℃, and add sodium hydroxide aqueous solution dropwise to adjust the pH to 9.5-10. Maintain the temperature at 90-110℃ for 1 hour. After the reaction is complete, a sodium 2,4-dichlorophenol solution is obtained.

[0031] The prepared sodium chloroacetate solution was slowly added dropwise to the above-mentioned sodium 2,4-dichlorophenol solution at a 2,4-dichlorophenol:water mass ratio of 1:0.5, along with a 32% sodium hydroxide solution. The molar ratio of sodium hydroxide to sodium chloroacetate was 2.0. The mixture was refluxed at 90°C with stirring, and the reaction was carried out at 100-105°C for 3 hours. After the reaction was completed, the temperature was maintained at 100-110°C for 3 hours. After filtration, washing twice with water, and drying, solid sodium 2,4-dichlorophenoxyacetate was obtained.

[0032] Water was added to the solution at a mass ratio of 1:1.5 for sodium 2,4-dichlorophenoxyacetic acid salt solid and water, and stirred until dissolved. 121.6 g of 30% hydrochloric acid was added, and the mixture was kept at 90-115°C for 0.5-2 hours. After the reaction was complete, the pH was maintained at approximately 0.5-1.5. After filtration, washing three times with water, and drying, 165.7 g of solid 2,4-dichlorophenoxyacetic acid was obtained with a purity of 83.4% and a yield of 75.0%.

[0033] Example 2

[0034] Mix 94.5g of chloroacetic acid and 36g of water and stir until the chloroacetic acid is completely dissolved. Control the temperature at 20-35℃, then add 125g of 32% sodium hydroxide aqueous solution and react for 0.5-1 hour to obtain sodium chloroacetate solution.

[0035] Mix 163g of 2,4-dichlorophenol and 125g of 32% sodium hydroxide aqueous solution and stir. Heat the mixture to 80-95℃, and add sodium hydroxide aqueous solution dropwise to adjust the pH to 9.5-10. Maintain the temperature at 90-110℃ for 1 hour. After the reaction is complete, a sodium 2,4-dichlorophenol solution is obtained.

[0036] The prepared sodium chloroacetate solution was slowly added dropwise to the above-mentioned sodium 2,4-dichlorophenol solution. At a 2,4-dichlorophenol:water mass ratio of 1:0.5, 0.005 g of catalyst Fe-ZSM-5 was added to the reaction system, along with a 32% sodium hydroxide solution. The molar ratio of sodium hydroxide to sodium chloroacetate was 2.0. The mixture was refluxed at 90°C with stirring, and condensation was carried out at 100-105°C for 2 hours. After the reaction was completed, the temperature was maintained at 100-110°C for 2 hours. After filtration, washing twice with water, and drying, solid sodium 2,4-dichlorophenoxyacetate was obtained.

[0037] Add water at a mass ratio of 1:1.5 for sodium 2,4-dichlorophenoxyacetic acid and stir until dissolved. Add 121.6 g of 30% hydrochloric acid and keep warm at 90-115℃ for 0.5 hours. After the reaction is complete, maintain the pH at approximately 0.5-1.0. After filtration, washing with water three times, and drying, 214.4 g of solid 2,4-dichlorophenoxyacetic acid with a purity of 97.8% and a yield of 97.0% is obtained.

[0038] Example 3

[0039] Mix 94.5g of chloroacetic acid and 36g of water and stir until the chloroacetic acid is completely dissolved. Control the temperature at 20-35℃, then add 125g of 32% sodium hydroxide aqueous solution and react for 0.5-1 hour to obtain sodium chloroacetate solution.

[0040] Mix 163g of 2,4-dichlorophenol and 125g of 32% sodium hydroxide aqueous solution and stir. Heat the mixture to 80-95℃, and add sodium hydroxide aqueous solution dropwise to adjust the pH to 9.5-10. Maintain the temperature at 90-110℃ for 1 hour. After the reaction is complete, a sodium 2,4-dichlorophenol solution is obtained.

[0041] The prepared sodium chloroacetate solution was slowly added dropwise to the above-mentioned sodium 2,4-dichlorophenol solution. A 2,4-dichlorophenol:water mass ratio of 1:0.5 was maintained. 0.005 g of catalyst MnO2-ZSM-5 was added to the reaction system, along with a 32% sodium hydroxide solution. The molar ratio of sodium hydroxide to sodium chloroacetate was 2.0. The mixture was refluxed at 90°C with stirring, and condensation was carried out at 100-105°C for 2 hours. After the reaction was completed, the temperature was maintained at 100-110°C for 2 hours. After filtration, washing twice with water, and drying, solid sodium 2,4-dichlorophenoxyacetate was obtained.

[0042] Add water at a mass ratio of 1:1.5 for sodium 2,4-dichlorophenoxyacetic acid and stir until dissolved. Add 121.6 g of 30% hydrochloric acid and keep warm at 90-115℃ for 0.5-2 hours. After the reaction is complete, maintain the pH at approximately 0.5-1.5. After filtration, washing with water three times, and drying, 219.9 g of solid 2,4-dichlorophenoxyacetic acid with a purity of 96.1% is obtained.

[0043] Example 4

[0044] Mix 94.5g of chloroacetic acid and 36g of water and stir until the chloroacetic acid is completely dissolved. Control the temperature at 20-35℃, then add 125g of 32% sodium hydroxide aqueous solution and react for 0.5-1 hour to obtain sodium chloroacetate solution.

[0045] 163g of 2,4-dichlorophenol and 125g of 32% sodium hydroxide aqueous solution were mixed and stirred, and the temperature was raised to 80-95℃. During the process, sodium hydroxide aqueous solution was added dropwise to adjust the pH to 9.5-10. 0.005g of catalyst Fe-ZSM-5 was added to the reaction system, and the temperature was maintained at 90-110℃ for 1 hour. After the reaction was completed, a sodium 2,4-dichlorophenol solution was obtained.

[0046] The prepared sodium chloroacetate solution was slowly added dropwise to the above sodium 2,4-dichlorophenol solution. The washing water of sodium 2,4-dichlorophenoxyacetate (the washing water of sodium 2,4-dichlorophenoxyacetate in Example 1) was added to a new batch of condensation reaction at a mass ratio of 2,4-dichlorophenol to water of 1:0.5. Simultaneously, a 32% sodium hydroxide solution was added, with a molar ratio of sodium hydroxide to sodium chloroacetate of 2.0. The mixture was refluxed at 90°C with stirring, and the condensation was carried out at 100-105°C for 2 hours. After the reaction was completed, the temperature was maintained at 100-110°C for 2 hours. After filtration, washing twice with water, and drying, solid sodium 2,4-dichlorophenoxyacetate was obtained.

[0047] Add water (washing water of 2,4-dichlorophenoxyacetic acid from Example 1) at a mass ratio of 1:1.5 and stir until dissolved (part of which is the washing water of 2,4-dichlorophenoxyacetic acid from Example 1; if insufficient, add fresh soft water). Add 121.6 g of 30% hydrochloric acid and maintain the temperature at 90°C for 0.5-2 hours. After the reaction is complete, maintain the pH at approximately 0.5-1.5. After filtration, washing three times with water, and drying, 168.6 g of solid 2,4-dichlorophenoxyacetic acid with a purity of 84.1% and a yield of 76.3% is obtained.

[0048] Example 5

[0049] Mix 94.5g of chloroacetic acid and 36g of water and stir until the chloroacetic acid is completely dissolved. Control the temperature at 20-35℃, then add 125g of 32% sodium hydroxide aqueous solution and react for 0.5 hours to obtain sodium chloroacetate solution.

[0050] 163g of 2,4-dichlorophenol and 125g of 32% sodium hydroxide aqueous solution were mixed and stirred, and the temperature was raised to 80-95℃. During the process, sodium hydroxide aqueous solution was added dropwise to adjust the pH to 9.5-10. 0.005g of catalyst Fe-ZSM-5 was added to the reaction system, and the temperature was maintained at 90-110℃ for 1 hour. After the reaction was completed, a sodium 2,4-dichlorophenol solution was obtained.

[0051] The prepared sodium chloroacetate solution was slowly added dropwise to the above-mentioned sodium 2,4-dichlorophenol solution. The washing water of sodium 2,4-dichlorophenoxyacetate (as described in Example 1) was added to a new batch of condensation reactions at a mass ratio of 2,4-dichlorophenol to water (washing water of sodium 2,4-dichlorophenoxyacetate in Example 1) of 1:0.5. 0.005 g of catalyst Fe-ZSM-5 was added to the reaction system, along with a 32% sodium hydroxide solution. The molar ratio of sodium hydroxide to sodium chloroacetate was 2.0. The mixture was refluxed at 90°C with stirring, and the condensation was carried out at 100-105°C for 2 hours. After the reaction was completed, the temperature was maintained at 100-110°C for 2 hours. After filtration, washing twice with water, and drying, solid sodium 2,4-dichlorophenoxyacetate was obtained.

[0052] Add water (washing water of 2,4-dichlorophenoxyacetic acid from Example 1) at a mass ratio of 1:1.5 and stir until dissolved (part of which is the washing water of 2,4-dichlorophenoxyacetic acid from Example 1; if insufficient, add fresh soft water). Add 121.6 g of 30% hydrochloric acid and maintain the temperature at 90°C for 0.5-2 hours. After the reaction is complete, maintain the pH at approximately 0.5-1.5. After filtration, washing three times with water, and drying, 218.3 g of solid 2,4-dichlorophenoxyacetic acid with a purity of 99.0% and a yield of 98.8% is obtained.

[0053] The above description is only a preferred embodiment of the present invention, but it is not intended to limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A method for the synthesis of 2,4-dichlorophenoxyacetic acid catalyzed by composite molecular sieve ZSM-5 and the preparation method using a water-reducing process, characterized in that, Includes the following steps: (1) Under alkaline conditions, 2,4-dichlorophenol undergoes a condensation reaction with sodium chloroacetate solution in the presence of a composite molecular sieve ZSM-5 catalyst to obtain crude sodium 2,4-dichlorophenoxyacetate. The composite molecular sieve ZSM-5 catalyst is selected from any one of Fe3O4-ZSM-5, Fe-ZSM-5, and MnO2-ZSM-5. The washing water of sodium 2,4-dichlorophenoxyacetate is added to a new batch of condensation reaction according to the mass ratio of 2,4-dichlorophenol to water of 1:0.2-1. The composite molecular sieve ZSM-5 catalyst is added to the reaction system, the reaction temperature is 100-105℃, the reaction time is 2-4 hours, and after the reaction is completed, the temperature is kept at 100-110℃ for 2-5 hours. (2) The obtained sodium 2,4-dichlorophenoxyacetic acid salt was washed with water and dried to obtain solid sodium 2,4-dichlorophenoxyacetic acid salt; (3) Step (2) 2,4-Dichlorophenoxyacetic acid sodium salt solid is dissolved in water, acidified with hydrochloric acid, washed with water and dried to obtain 2,4-dichlorophenoxyacetic acid product.

2. The preparation method of 2,4-dichlorophenoxyacetic acid catalyzed by composite molecular sieve ZSM-5 and using a water-reducing process according to claim 1, characterized in that: In step (1), the alkaline conditions are achieved by adding sodium hydroxide, wherein the molar ratio of sodium chloroacetate: 2,4-dichlorophenol: sodium hydroxide: water is 1:0.5-3.0:0.2-3.0:0.2-1.

3. The preparation method of 2,4-dichlorophenoxyacetic acid catalyzed by composite molecular sieve ZSM-5 and using a water-reducing process according to claim 1, characterized in that: In step (3), the mass ratio of crude sodium 2,4-dichlorophenoxyacetate to water is 1:1.5-3.5; During the hydrochloric acid acidification process, the mass concentration of hydrochloric acid is 20-35%; the molar ratio of sodium 2,4-dichlorophenoxyacetic acid to hydrochloric acid is 1:1.0-1.5, the reaction temperature is 90-115℃, and the acidification is carried out for 0.5-2 hours. After the acidification reaction is completed, the pH value is 0.5-1.

5.

4. The preparation method of 2,4-dichlorophenoxyacetic acid catalyzed by composite molecular sieve ZSM-5 and using a water-reducing process according to claim 1, characterized in that: The water used for acidification and washing in step (3) is reused in a new batch of synthesis steps (3) as a solvent and water, with a mass ratio of crude sodium 2,4-dichlorophenoxyacetic acid salt to water of 1:1.5-3.5.

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