Method for synthesizing 3, 5-dichlorobenzoic acid

Abstract

The invention discloses a method for synthesizing 3, 5-dichlorobenzoic acid, and relates to the technical field of raw material synthesis. 3, 5-dichlorobenzoyl chloride, a solvent and water are put into a reactor for reaction, the reaction temperature, the reaction pressure and the stirring speed are controlled, and tail gas is absorbed by tap water; sampling and detecting the content of 3, 5-dichlorobenzoyl chloride in the solvent, injecting a mixed solution of 3, 5-dichlorobenzoyl chloride and water into the reactor, cooling the reactor, repeatedly stirring, washing and carrying out suction filtration by using a vacuum suction filter until the pH value of washing water is neutral, and washing a filter cake by using ultrapure water to obtain a wet material; and feeding the wet material into an air-drying oven for drying to obtain a 3, 5-dichlorobenzoic acid product. The 3, 5-dichlorobenzoic acid is prepared through one-step synthesis of a hydrolysis method, the production efficiency is improved, the technological process is simple, side reactions are few, production is safe and environmentally friendly, the detection and control cost is low, cost is reduced, efficiency is improved, the product purity is high, and the technological yield is high.

Description

Technical Field

[0001] The invention relates to the technical field of raw material synthesis, in particular to a method for synthesizing 3,5-dichlorobenzoic acid. Background Art

[0002] Halogenated formic acid and its derivatives are an important class of chemical and pharmaceutical intermediates, which are widely used as raw materials for the production of fungicides, insecticides, dyes and drugs. 3,5-Dichlorobenzoic acid is one of them, which can be used to prepare a variety of chemical products such as medicines, pesticides, dyes, fungicides, etc.

[0003] Patent CN103224451A discloses a method for synthesizing 3,5-dichlorobenzoic acid: benzonitrile is mainly used as a raw material, and 3,5-dichlorobenzonitrile is chlorinated in an acidic environment in the presence of a solvent and a chlorinating agent to generate 3,5-dichlorobenzonitrile; 3,5-dichlorobenzonitrile is first hydrolyzed in an alkaline environment to 3,5-dichlorobenzoate, and then acidified to obtain 3,5-dichlorobenzoic acid, or 3,5-dichlorobenzonitrile is directly hydrolyzed in an acidic environment to obtain 3,5-dichlorobenzoic acid. The steps are relatively complicated, the process flow is long, and the inspection and control costs are high. Summary of the invention

[0004] The purpose of the present invention is to provide a method for synthesizing 3,5-dichlorobenzoic acid, which can synthesize 3,5-dichlorobenzoic acid in one step by hydrolysis, greatly improve production efficiency, increase the diversity of the product synthesis path, reduce dependence on a single raw material, and solve the problems raised in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for synthesizing 3,5-dichlorobenzoic acid comprises the following specific steps: S1. Add 3,5-dichlorobenzoyl chloride, solvent and water into a reactor, control the reaction temperature to 80°C-130°C, the reaction pressure to -2-5KPa, the stirring speed to 180-270r / min, react for 12-18h, and absorb the tail gas with tap water; It should be noted that 3,5-dichlorobenzoyl chloride is an acyl chloride with high reactivity; water, as a nucleophile, attacks the carbon-based carbon atom of the acyl chloride. High-temperature stirring provides the activation energy required for the reaction and accelerates the reaction process. The acyl chloride is hydrolyzed to generate the corresponding carboxylic acid, namely 3,5-dichlorobenzoic acid, and hydrogen chloride is released as a by-product. Hydrogen chloride is toxic and appropriate protective measures need to be taken. Therefore, tap water is used to absorb part of it.

[0006] S2, sampling and detecting the content of 3,5-dichlorobenzoyl chloride in the solvent, injecting a mixed solution of 3,5-dichlorobenzoyl chloride and water into the reactor, cooling the reactor to below 25°C, repeatedly stirring and filtering with a vacuum filter until the pH of the washing water is neutral, and washing the filter cake with ultrapure water to obtain a wet material; It should be noted that the mixed solution is used to absorb the hydrogen chloride produced in the reaction process, and can safely absorb the hydrogen chloride, reducing harm to the environment and operators. It also has the function of cooling the solvent, using the cooling effect of water to control the reaction rate, avoid violent reactions, and ensure safety.

[0007] S3. Send the wet material into an air drying oven, set the oven temperature to 60°C-90°C, and dry for 12-18 hours to obtain 3,5-dichlorobenzoic acid product.

[0008] Furthermore, in S1, the solvent is one of petroleum ether, toluene, xylene and methanol.

[0009] Furthermore, in S1, the volume ratio of 3,5-dichlorobenzoyl chloride, solvent and water is 1:3:0.2.

[0010] Furthermore, in S1, the purity of the 3,5-dichlorobenzoyl chloride is ≥99%.

[0011] Furthermore, in S2, the sampling is performed and the content of 3,5-dichlorobenzoyl chloride is detected. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, a mixed solution of 3,5-dichlorobenzoyl chloride and water can be injected into the reactor.

[0012] It should be noted that when the concentration of 3,5-dichlorobenzoyl chloride is low, the reaction rate will slow down. Adding a mixed solution can effectively control the reaction and avoid side reactions (further hydrolysis of carboxylic acid and other chlorinated products) or incomplete reactions caused by too fast a reaction. Adding a cooling agent can help maintain the temperature of the reaction system within a suitable range to prevent side reactions or product decomposition caused by overheating. A small amount of 3,5-dichlorobenzoyl chloride in the mixed solution can ensure that the remaining acid chloride is completely hydrolyzed and increase the yield.

[0013] Furthermore, in S2, the volume ratio of 3,5-dichlorobenzoyl chloride to water in the mixed solution of 3,5-dichlorobenzoyl chloride and water is 1:2.

[0014] Furthermore, in S3, the 3,5-dichlorobenzoic acid product has a 3,5-dichlorobenzoic acid content of ≥99%, a single component impurity of ≤0.5%, a moisture content of ≤0.5%, and is in the form of a white powdery solid.

[0015] Furthermore, a method for synthesizing 3,5-dichlorobenzoic acid has a comprehensive yield of 80%-85%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 3,5-dichlorobenzoic acid is prepared by one-step synthesis through hydrolysis, which improves production efficiency, has a simple process flow, few side reactions, safe and environmentally friendly production, low inspection and control costs, and reduces costs and increases efficiency. The prepared 3,5-dichlorobenzoic acid has high purity and high process yield, providing the industry with a direction for increasing the diversity of product synthesis pathways. DETAILED DESCRIPTION

[0017] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: S1. Put 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 into a reactor. The purity of 3,5-dichlorobenzoyl chloride is ≥99%. The reaction temperature is controlled at 85°C, the reaction pressure is 4KPa, the stirring speed is 200r / min, the reaction is carried out for 18h, and the tail gas is absorbed by tap water; S2. Take a sample and detect the content of 3,5-dichlorobenzoyl chloride in the solvent. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, inject a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2 into the reactor. After the reactor is cooled to below 25°C, use a vacuum filter to repeatedly stir and filter until the pH of the washing water is neutral. Wash the filter cake with ultrapure water to obtain a wet material. S3. Send the wet material into an air drying oven, set the oven temperature to 80°C, and dry for 12 hours to obtain 3,5-dichlorobenzoic acid product.

[0019] Embodiment 2: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: S1. Put 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 into a reactor. The purity of 3,5-dichlorobenzoyl chloride is ≥99%. The reaction temperature is controlled at 100°C, the reaction pressure is 2KPa, the stirring speed is 220r / min, the reaction is carried out for 18h, and the tail gas is absorbed by tap water; S2. Take a sample and detect the content of 3,5-dichlorobenzoyl chloride in the solvent. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, inject a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2 into the reactor. After the reactor is cooled to below 25°C, use a vacuum filter to repeatedly stir and filter until the pH of the washing water is neutral. Wash the filter cake with ultrapure water to obtain a wet material. S3. Send the wet material into an air drying oven, set the oven temperature to 80°C, and dry for 12 hours to obtain 3,5-dichlorobenzoic acid product.

[0020] Embodiment 3: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: S1. Put 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 into a reactor, the purity of 3,5-dichlorobenzoyl chloride is ≥99%, the reaction temperature is controlled at 115°C, the reaction pressure is 0KPa, the stirring speed is 240r / min, the reaction is carried out for 18h, and the tail gas is absorbed by tap water; S2. Take a sample and detect the content of 3,5-dichlorobenzoyl chloride in the solvent. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, inject a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2 into the reactor. After the reactor is cooled to below 25°C, use a vacuum filter to repeatedly stir and filter until the pH of the washing water is neutral. Wash the filter cake with ultrapure water to obtain a wet material. S3. Send the wet material into an air drying oven, set the oven temperature to 80°C, and dry for 12 hours to obtain 3,5-dichlorobenzoic acid product.

[0021] Embodiment 4: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: S1. Put 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 into a reactor. The purity of 3,5-dichlorobenzoyl chloride is ≥99%. The reaction temperature is controlled at 80°C, the reaction pressure is 5KPa, the stirring speed is 270r / min, the reaction is carried out for 18h, and the tail gas is absorbed by tap water; S2. Take a sample and detect the content of 3,5-dichlorobenzoyl chloride in the solvent. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, inject a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2 into the reactor. After the reactor is cooled to below 25°C, use a vacuum filter to repeatedly stir and filter until the pH of the washing water is neutral. Wash the filter cake with ultrapure water to obtain a wet material. S3. Send the wet material into an air drying oven, set the oven temperature to 80°C, and dry for 12 hours to obtain 3,5-dichlorobenzoic acid product.

[0022] Embodiment 5: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: S1. Put 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 into a reactor, the purity of 3,5-dichlorobenzoyl chloride is ≥99%, the reaction temperature is controlled at 130°C, the reaction pressure is -2KPa, the stirring speed is 180r / min, the reaction is carried out for 18h, and the tail gas is absorbed by tap water; S2. Take a sample and detect the content of 3,5-dichlorobenzoyl chloride in the solvent. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, inject a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2 into the reactor. After the reactor is cooled to below 25°C, use a vacuum filter to repeatedly stir and filter until the pH of the washing water is neutral. Wash the filter cake with ultrapure water to obtain a wet material. S3. Send the wet material into an air drying oven, set the oven temperature to 80°C, and dry for 12 hours to obtain 3,5-dichlorobenzoic acid product.

[0023] Comparative Example 1: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: S1. Put 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 into a reactor. The purity of 3,5-dichlorobenzoyl chloride is ≥99%. The reaction temperature is controlled at 85°C, the reaction pressure is 4KPa, the stirring speed is 200r / min, the reaction is carried out for 18h, and the tail gas is absorbed by tap water; S2. Inject a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2 into the reactor. After the reactor is cooled to below 25° C., use a vacuum filter to repeatedly stir, wash and filter until the pH of the washing water is neutral. Wash the filter cake with ultrapure water to obtain a wet material. S3. Send the wet material into an air drying oven, set the oven temperature to 80°C, and dry for 12 hours to obtain 3,5-dichlorobenzoic acid product.

[0024] The difference between this comparative example and Example 1 is that S2 does not take samples and detect the content of 3,5-dichlorobenzoyl chloride in the solvent, but directly injects a mixed solution of 3,5-dichlorobenzoyl chloride and water in a volume ratio of 1:2.

[0025] Comparative Example 2: A method for synthesizing 3,5-dichlorobenzoic acid, the specific steps are as follows: 3,5-dichlorobenzoyl chloride, toluene and water in a volume ratio of 1:3:0.2 are put into a reactor, the purity of 3,5-dichlorobenzoyl chloride is ≥99%, the reaction temperature is controlled at 85°C, the reaction pressure is 4KPa, the stirring speed is 200r / min, the reaction is carried out for 18 hours, the tail gas is absorbed by tap water, and the reactor is cooled to below 25°C and then repeatedly stirred, washed and filtered using a vacuum filter until the pH of the washing water is neutral. The filter cake is washed with ultrapure water to obtain a wet material; the wet material is sent to an air drying oven, the oven temperature is set at 80°C, and the drying is carried out for 12 hours to obtain a 3,5-dichlorobenzoic acid product.

[0026] The difference between this comparative example and Example 1 is that the original S2 step is omitted.

[0027] test: 1. Analysis of ingredients of 3,5-dichlorobenzoic acid products: The 3,5-dichlorobenzoic acid product was qualitatively and quantitatively analyzed by nuclear magnetic resonance spectrometry and high performance liquid chromatography.

[0028] Table 1 2. 3,5-dichlorobenzoic acid product yield: Product yield = (actual output / theoretical output) × 100% Table 2 3. Results and Discussion 1. As can be seen from Table 1, the 3,5-dichlorobenzoic acid content in the 3,5-dichlorobenzoic acid product prepared in Example 1-3 is ≥99%, the impurities in a single component are ≤0.5%, and the moisture is ≤0.5%, which is significantly higher than the purity of 3,5-dichlorobenzoic acid in Comparative Example 1-2.

[0029] 2. As shown in Table 2, the comprehensive yield of 3,5-dichlorobenzoic acid product in the process flow of Example 1-3 is 80%-85%, which is significantly higher than the process yield of Comparative Example 1-2.

[0030] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0031] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for synthesizing 3,5-dichlorobenzoic acid, characterized in that: The specific steps are as follows: S1. Add 3,5-dichlorobenzoyl chloride, solvent and water into a reactor, control the reaction temperature to 80°C-130°C, the reaction pressure to -2-5KPa, the stirring speed to 180-270r / min, react for 12-18h, and absorb the tail gas with tap water; S2, sampling and detecting the content of 3,5-dichlorobenzoyl chloride in the solvent, injecting a mixed solution of 3,5-dichlorobenzoyl chloride and water into the reactor, cooling the reactor to below 25°C, repeatedly stirring and filtering with a vacuum filter until the pH of the washing water is neutral, and washing the filter cake with ultrapure water to obtain a wet material; S3. Send the wet material into an air drying oven, set the oven temperature to 60°C-90°C, and dry for 12-18 hours to obtain 3,5-dichlorobenzoic acid product.

2. A method for synthesizing 3,5-dichlorobenzoic acid according to claim 1, characterized in that: In S1, the solvent is one of petroleum ether, toluene, xylene and methanol.

3. A method for synthesizing 3,5-dichlorobenzoic acid according to claim 1, characterized in that: In S1, the volume ratio of 3,5-dichlorobenzoyl chloride, solvent and water is 1:3:0.

2.

4. A method for synthesizing 3,5-dichlorobenzoic acid according to claim 1, characterized in that: In S1, the purity of the 3,5-dichlorobenzoyl chloride is ≥99%.

5. A method for synthesizing 3,5-dichlorobenzoic acid according to claim 1, characterized in that: In S2, the sampling is performed and the content of 3,5-dichlorobenzoyl chloride is detected. When the content of 3,5-dichlorobenzoyl chloride is lower than 0.5%, a mixed solution of 3,5-dichlorobenzoyl chloride and water is injected into the reactor.

6. A method for synthesizing 3,5-dichlorobenzoic acid according to claim 1, characterized in that: In S2, the volume ratio of 3,5-dichlorobenzoyl chloride to water in the mixed solution of 3,5-dichlorobenzoyl chloride and water is 1:

2.

7. A method for synthesizing 3,5-dichlorobenzoic acid according to claim 1, characterized in that: In S3, the 3,5-dichlorobenzoic acid product has a 3,5-dichlorobenzoic acid content of ≥99%, a single component impurity of ≤0.5%, a moisture content of ≤0.5%, and is in the form of a white powdery solid.

8. A method for synthesizing 3,5-dichlorobenzoic acid according to any one of claims 1 to 7, characterized in that: The comprehensive yield of 3,5-dichlorobenzoyl chloride is 80%-85%.

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