Method for synthesizing 2, 3-dichloro-5-trifluoromethylpyridine in fixed bed reactor

Abstract

The invention belongs to the technical field of chemical synthesis, and relates to a method for synthesizing 2, 3-dichloro-5-trifluoromethylpyridine in a fixed bed reactor. The method comprises the following steps: reacting molten 2-chloro-5-trifluoromethylpyridine with chlorine in a fixed bed reactor filled with a supported metal catalyst to generate 2, 3-dichloro-5-trifluoromethylpyridine; the metal in the supported metal catalyst is one or more of iron, platinum, ruthenium, nickel or cobalt, the carrier is a molecular sieve, and the loading amount of the metal accounts for 0.5-5% of the mass of the carrier. According to the method, recycling of the byproduct 2-chloro-5-trifluoromethylpyridine generated in synthesis of 2, 3-dichloro-5-trifluoromethylpyridine is achieved, resource recycling of waste is achieved, the purity of refined 2, 3-dichloro-5-trifluoromethylpyridine obtained after rectification is larger than or equal to 99%, and the yield reaches 90% or above; the method is simple in process, has the advantages of few side reactions, high quality, high yield, short reaction time, few three wastes, safety and the like, is easy to industrialize, and has better application value.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis and relates to a method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine in a fixed bed reactor. Background Art

[0002] Fluazinam is a heterocyclic protective fungicide developed by Ishihara Sangyo Co., Ltd. of Japan. It is effective against Alternaria, Botrytis (especially those that have developed resistance to benzimidazoles and dicarboximides), Phytophthora, Monoaxella, Sclerotinia, and Venturia. It is not systemic and has no therapeutic effect, but it is extremely resistant to rain erosion and has a long residual effect. It is a good foliar spray and can also treat spider mites. Soil treatment can also effectively prevent and control cruciferous clubroot and rice damping-off caused by black root mold. It is plant-safe when used on fruit trees and vegetables.

[0003] 2,3-Dichloro-5-trifluoromethylpyridine is an important intermediate in the synthesis of fluazinam. Currently, the reports on the synthesis method of 2,3-dichloro-5-trifluoromethylpyridine are relatively single, and a by-product 2-chloro-5-trifluoromethylpyridine is produced during the synthesis process. During the distillation process of 2,3-dichloro-5-trifluoromethylpyridine, the by-product 2-chloro-5-trifluoromethylpyridine is extracted as a fore fraction and is generally scrapped, resulting in great waste.

[0004] In the prior art, WO2019 / 109936A1 uses 2-chloro-5-trifluoromethylpyridine and chlorine as raw materials to prepare 2,3-dichloro-5-trifluoromethylpyridine, adopts an autoclave reaction, and the temperature is 150°C, the pressure is about 2.0 MPa, and the reaction time is 20 hours. This method has a long reaction time and complex post-processing.

[0005] CN 109988102 A adopts a molded catalyst to prepare 2,3-dichloro-5-trifluoromethylpyridine by chlorination reaction in a fixed bed reactor at a reaction temperature of 280-320°C, and carbon tetrachloride is added as a reaction solvent. This method has a high reaction temperature and a high process risk, and is difficult to realize industrialization.

[0006] The above documents all use directly purchased high-purity 2-chloro-5-trifluoromethylpyridine to prepare 2,3-dichloro-5-trifluoromethylpyridine, and do not mention the method of recovering the by-product 2-chloro-5-trifluoromethylpyridine in the distillation process of 2,3-dichloro-5-trifluoromethylpyridine to prepare 2,3-dichloro-5-trifluoromethylpyridine. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine by using a fixed bed reactor. The method uses 2-chloro-5-trifluoromethylpyridine, a byproduct produced in the process of producing 2,3-dichloro-5-trifluoromethylpyridine, as a raw material, fixes a catalyst supported on a molecular sieve on a pipeline reactor, and then introduces chlorine in proportion to synthesize 2,3-dichloro-5-trifluoromethylpyridine.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine in a fixed bed reactor, wherein molten 2-chloro-5-trifluoromethylpyridine reacts with chlorine in a fixed bed reactor filled with a supported metal catalyst to generate 2,3-dichloro-5-trifluoromethylpyridine;

[0010] The metal in the supported metal catalyst is one or more of iron, platinum, ruthenium, nickel or cobalt, the carrier is a molecular sieve, and the metal loading accounts for 0.5-5% of the carrier mass.

[0011] The chemical reaction formula is as follows:

[0012]

[0013] The raw material 2-chloro-5-trifluoromethylpyridine is a by-product produced in the process of preparing 2,3-dichloro-5-trifluoromethylpyridine. The content of 2-chloro-5-trifluoromethylpyridine in the raw material is 80%-90%.

[0014] The supported metal catalyst is loaded into a fixed bed reactor, and molten 2-chloro-5-trifluoromethylpyridine liquid and chlorine gas are introduced into the preheated and pressurized fixed bed reactor to react and generate 2,3-dichloro-5-trifluoromethylpyridine.

[0015] The preparation method of the supported metal catalyst is to load chloride, oxide or acetylacetone complex of iron, platinum, ruthenium, nickel or cobalt onto a molecular sieve by solution impregnation method, and calcine at 250-300° C. for 2-3 hours. The molecular sieve is HZMS-5.

[0016] The molar ratio of the introduced 2-chloro-5-trifluoromethylpyridine to the chlorine gas is 1:1-10, and the flow rate of the introduced 2-chloro-5-trifluoromethylpyridine is 10-100 ml / min.

[0017] Furthermore, the molar ratio of the introduced 2-chloro-5-trifluoromethylpyridine to the chlorine gas is 1:1-3.0.

[0018] The molten 2-chloro-5-trifluoromethylpyridine liquid is obtained by heating 2-chloro-5-trifluoromethylpyridine solid to 50-80° C. to turn it into liquid.

[0019] The preheating and pressurizing are to heat the solid bed reactor to 50-150° C., pass air and pressurize it to 2-3 MPa, and the reaction time is 2-20 minutes.

[0020] After the reaction is completed, the material is cooled, and then 2,3-dichloro-5-trifluoromethylpyridine is obtained after alkali washing and distillation.

[0021] The purity of the obtained product 2,3-dichloro-5-trifluoromethylpyridine is ≥99%.

[0022] The alkaline washing is to add water and alkaline solution to the reaction solution, adjust the pH to 8-9, and separate the layers. The alkaline solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution.

[0023] The mass concentration of the alkaline solution is 10% to 50%.

[0024] The distillation temperature is 130-150° C. and the distillation pressure is 100-350 Pa.

[0025] Beneficial effects of the present invention:

[0026] The present invention realizes the recycling of 2-chloro-5-trifluoromethylpyridine, a byproduct generated in the synthesis of 2,3-dichloro-5-trifluoromethylpyridine, and achieves the resource recycling of waste. After distillation, the purity of refined 2,3-dichloro-5-trifluoromethylpyridine is ≥99%, and the yield is more than 90%. The fixed bed reactor is adopted to avoid the problem of separation and recovery of the catalyst, and no other solvent is required for the reaction, which reduces the energy consumption of post-processing. The catalyst of the present invention can make the reaction proceed at a lower temperature and can improve the reaction yield. The process of the present invention is simple, has the advantages of less side reactions, high quality, high yield, short reaction time, less three wastes, safety, etc., is easy to industrialize, and has good application value. DETAILED DESCRIPTION

[0027] The specific implementation of the technical solution of the present invention is described in detail below, but the present invention is not limited to the following description: The present invention is described below in conjunction with specific embodiments. The raw material 2-chloro-5-trifluoromethylpyridine is a by-product produced in the process of preparing 2,3-dichloro-5-trifluoromethylpyridine, and the content of 2-chloro-5-trifluoromethylpyridine in the raw material is 80%-90%.

[0028] Embodiment 1:

[0029] (1) HZSM-5 was selected as a carrier and ferric chloride was used as a metal source. The catalyst was prepared by an impregnation method and calcined at 250° C. for 3 h to obtain a Fe / ZSM-5 catalyst. The Fe loading amount accounted for 1.5% of the carrier mass. The catalyst was loaded into a fixed bed reactor and the device was set up.

[0030] (2) 1600 g of raw material 2-chloro-5-trifluoromethylpyridine (content 85.3%, equivalent to 1364.8 g) was temporarily stored in a raw material bottle and kept warm in an oil bath at 60°C;

[0031] (3) The temperature in the reactor is set to 120-125°C;

[0032] (4) The metering pump is connected to the raw material bottle, and the flow rate of the metering pump is set to 15 ml / min. The gas flow meter is connected to the chlorine gas cylinder, and the regulating valve is opened to control the flow rate to 4.5 L / min. At this flow rate, the molar ratio of 2-chloro-5-trifluoromethylpyridine to chlorine is 1:2. First, open the gas phase valve to let in air, and control the system pressure to 2 MPa. Turn on the pump and pump the raw materials into the fixed bed reactor at a flow rate of 15 ml / min for reaction. The reaction liquid stays in the reactor for about 5 minutes;

[0033] (5) The reaction liquid taken out from the reactor was cooled to 20-30° C., and 2-chloro-5-trifluoromethylpyridine was sampled and tested. The gas chromatography normalized the reaction liquid to 1.5%. 400 g of water and 11.5 g of liquid alkali (30% sodium hydroxide aqueous solution) were added to the reaction liquid to adjust the pH to 8-9, and the layers were separated. The oil layer was heated to 130-150° C. under negative pressure (100-350 Pa) and distilled to obtain 1560 g of refined 2,3-dichloro-5-trifluoromethylpyridine, with a yield of 96.1% and a purity of ≥99%.

[0034] Embodiment 2:

[0035] (1) HZSM-5 was selected as a carrier and ruthenium chloride was used as a metal source. The catalyst was prepared by an impregnation method and calcined at 250° C. for 3 h to obtain a ruthenium / ZSM-5 catalyst. The ruthenium loading amount accounted for 0.8% of the carrier mass. The catalyst was loaded into a fixed bed reactor and the device was set up.

[0036] (2) 1600 g of raw material 2-chloro-5-trifluoromethylpyridine (content 85.3%, equivalent to 1364.8 g) was temporarily stored in a raw material bottle and kept warm in an oil bath at 60°C;

[0037] (3) The temperature in the reactor is set to 100-105°C;

[0038] (4) The metering pump is connected to the raw material bottle, and the flow rate of the metering pump is set to 15 ml / min. The gas flow meter is connected to the chlorine gas cylinder, and the regulating valve is opened to control the flow rate to 4.5 L / min. At this flow rate, the molar ratio of 2-chloro-5-trifluoromethylpyridine to chlorine is 1:2. First, open the gas phase valve to pass air to control the system pressure to 2 MPa. Turn on the pump and pump the raw materials into the fixed bed reactor at a flow rate of 15 ml / min for reaction. The reaction liquid stays in the reactor for about 5 minutes;

[0039] (5) The reaction liquid taken out from the reactor was cooled to 20-30° C., and 2-chloro-5-trifluoromethylpyridine was sampled and tested. The gas chromatography normalized the reaction liquid to 0.6%. 400 g of water and 11.8 g of liquid alkali (30% sodium hydroxide aqueous solution) were added to the reaction liquid to adjust the pH to 8-9, and the layers were separated. The oil layer was heated to 130-150° C. under negative pressure (100-350 Pa) and distilled to obtain 1576 g of refined 2,3-dichloro-5-trifluoromethylpyridine, with a yield of 97.1% and a purity of ≥99%.

[0040] Embodiment 3:

[0041] (1) HZSM-5 was selected as a carrier and ruthenium chloride was used as a metal source. The catalyst was prepared by an impregnation method and calcined at 250° C. for 3 h to obtain a ruthenium / ZSM-5 catalyst. The ruthenium loading amount accounted for 0.8% of the carrier mass. The catalyst was loaded into a fixed bed reactor and the device was set up.

[0042] (2) 1600 g of raw material 2-chloro-5-trifluoromethylpyridine (content 85.3%, equivalent to 1364.8 g) was temporarily stored in a raw material bottle and kept warm in an oil bath at 60°C;

[0043] (3) The temperature in the reactor is set to 100-105°C;

[0044] (4) The metering pump is connected to the raw material bottle, and the flow rate of the metering pump is set to 30 ml / min. The gas flow meter is connected to the chlorine gas cylinder, and the regulating valve is opened to control the flow rate to 4.5 L / min. At this flow rate, the molar ratio of 2-chloro-5-trifluoromethylpyridine to chlorine is 1:1.5. First, open the gas phase valve to pass air to control the system pressure to 2 MPa. Turn on the pump and pump the raw materials into the fixed bed reactor at a flow rate of 30 ml / min for reaction. The reaction liquid stays in the reactor for about 2.5 min;

[0045] (5) The reaction liquid taken out from the reactor was cooled to 20-30° C., and 2-chloro-5-trifluoromethylpyridine was sampled and tested. The gas chromatography normalized the reaction liquid to 0.9%. 400 g of water and 11.3 g of liquid alkali (30% sodium hydroxide aqueous solution) were added to the reaction liquid to adjust the pH to 8-9, and the layers were separated. The oil layer was heated to 130-150° C. under negative pressure (100-350 Pa) and distilled to obtain 1583 g of refined 2,3-dichloro-5-trifluoromethylpyridine, with a yield of 97.5% and a purity of ≥99%.

[0046] Embodiment 4:

[0047] (1) HZSM-5 was selected as a carrier, ruthenium chloride and ferric chloride were used as metal sources, and the catalyst was prepared by an impregnation method. After calcination at 250° C. for 3 h, a ruthenium-Fe / ZSM-5 catalyst was prepared. The ruthenium loading amount accounted for 0.8% of the carrier mass, and the Fe loading amount accounted for 1.5% of the carrier mass. The catalyst was loaded into a fixed bed reactor and the device was set up;

[0048] (2) 1600 g of raw material 2-chloro-5-trifluoromethylpyridine (content 85.3%, equivalent to 1364.8 g) was temporarily stored in a raw material bottle and kept warm in an oil bath at 60°C;

[0049] (3) The temperature in the reactor is set to 100-105°C;

[0050] (4) The metering pump is connected to the raw material bottle, and the flow rate of the metering pump is set to 30 ml / min. The gas flow meter is connected to the chlorine gas cylinder, and the regulating valve is opened to control the flow rate to 4.5 L / min. At this flow rate, the molar ratio of 2-chloro-5-trifluoromethylpyridine to chlorine is 1:1.5. First, open the gas phase valve to pass air to control the system pressure to 2 MPa. Turn on the pump and pump the raw materials into the fixed bed reactor at a flow rate of 30 ml / min for reaction. The reaction liquid stays in the reactor for about 2.5 min;

[0051] (5) The reaction liquid taken out from the reactor was cooled to 20-30° C., and 2-chloro-5-trifluoromethylpyridine was sampled and tested. The gas chromatography normalized the reaction liquid to 1.2%. 400 g of water and 11.7 g of liquid alkali (30% sodium hydroxide aqueous solution) were added to the reaction liquid to adjust the pH to 8-9, and the layers were separated. The oil layer was heated to 130-150° C. under negative pressure (100-350 Pa) and distilled to obtain 1581 g of refined 2,3-dichloro-5-trifluoromethylpyridine, with a yield of 97.4% and a purity of ≥99%.

[0052] Comparative Example 1:

[0053] The ferric chloride in Example 1 was used as the metal source, and manganese chloride was used as the metal source. The catalyst was prepared by impregnation method, and the catalyst was calcined at 250° C. for 3 h to obtain a Mn / ZSM-5 catalyst. The Mn loading amount accounted for 2.5% of the carrier mass. The other reaction conditions and product treatment methods were the same as those in Example 1. The reaction liquid extracted from the reactor was cooled to 20-30° C., and 2-chloro-5-trifluoromethylpyridine was sampled and tested. The gas chromatography normalized 56.89%, and a large amount of raw materials remained unreacted, indicating that the catalytic effect was poor.

[0054] Comparative Example 2:

[0055] The HZSM-5 in Example 1 was replaced with L-type molecular sieve, and the other reaction conditions and product treatment methods were the same as those in Example 1. The reaction liquid taken out of the reactor was cooled to 20-30° C., and 2-chloro-5-trifluoromethylpyridine was sampled and tested. The gas chromatography normalized 35.26%, and a large amount of raw materials remained unreacted, indicating that the molecular sieve had a poor effect;

[0056] The above examples are only for illustrating the technical concept and technical features of the present invention, and cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine in a fixed bed reactor, characterized in that: Molten 2-chloro-5-trifluoromethylpyridine reacts with chlorine in a fixed bed reactor filled with a supported metal catalyst to produce 2,3-dichloro-5-trifluoromethylpyridine; The metal in the supported metal catalyst is one or more of iron, platinum, ruthenium, nickel or cobalt, the carrier is a molecular sieve, and the metal loading accounts for 0.5-5% of the carrier mass.

2. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1, characterized in that: The supported metal catalyst is loaded into a fixed bed reactor, and molten 2-chloro-5-trifluoromethylpyridine liquid and chlorine gas are introduced into the preheated and pressurized fixed bed reactor to react and generate 2,3-dichloro-5-trifluoromethylpyridine.

3. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1, characterized in that: The preparation method of the supported metal catalyst is to load chloride, oxide or acetylacetone complex of iron, platinum, ruthenium, nickel or cobalt onto a molecular sieve by solution impregnation method, and calcine at 250-300° C. for 2-3 hours. The molecular sieve is HZMS-5.

4. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1 or 2, characterized in that: The molar ratio of the introduced 2-chloro-5-trifluoromethylpyridine to the chlorine gas is 1:1-10, the flow rate of the introduced 2-chloro-5-trifluoromethylpyridine is 10-100 ml / min, and the reaction time is 2-20 min.

5. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1 or 2, characterized in that: The molten 2-chloro-5-trifluoromethylpyridine liquid is obtained by heating 2-chloro-5-trifluoromethylpyridine solid to 50-80° C. to turn it into liquid.

6. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1 or 2, characterized in that: The preheating and pressurizing are to heat the solid bed reactor to 50-150° C. and pressurize it to 2-3 MPa through air.

7. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 1 or 2, characterized in that: After the reaction is completed, the material is cooled, washed with alkali and distilled to obtain 2,3-dichloro-5-trifluoromethylpyridine.

8. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 8, characterized in that: The alkaline washing is to add water and alkaline solution to the reaction solution, adjust the pH to 8-9, and separate the layers. The alkaline solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution.

9. The method for synthesizing 2,3-dichloro-5-trifluoromethylpyridine according to claim 8, characterized in that: The distillation temperature is 130-150° C. and the distillation pressure is 100-350 Pa.

Images