Purification method of 2-chloro-5-chloromethylpyridine synthetic liquid

Abstract

The invention relates to the technical field of fine chemical engineering, and particularly discloses a purification method of a 2-chloro-5-chloromethylpyridine synthetic liquid, which mainly comprises the following steps: carrying out reduced pressure distillation on the 2-chloro-5-chloromethylpyridine synthetic liquid to remove toluene to obtain a distillation base solution; adding an extracting agent into the distillation base solution, extracting, standing for layering, and collecting supernatant to obtain an extracting solution; heating and distilling the extracting solution to remove the extracting agent, so as to obtain a 2-chloro-5-chloromethylpyridine crude product; and adding a calcium salt stabilizer into the 2-chloro-5-chloromethylpyridine crude product, and carrying out high-vacuum distillation to collect distillate, thereby obtaining the 2-chloro-5-chloromethylpyridine product. The 2-chloro-5-chloromethylpyridine product obtained by the purification method has the characteristics of high content, high yield and simple purification process, the extraction agent process is used for replacing hydrolysis and neutralization processes, the extraction agent can be recycled, no water is introduced, no large amount of wastewater is generated due to introduction of water, and the method is suitable for industrial production.

Description

Technical Field

[0001] The present application relates to the technical field of fine chemical industry, and more specifically, to a method for purifying a synthetic liquid of 2-chloro-5-chloromethylpyridine. Background Art

[0002] 2-chloro-5-chloromethylpyridine is an important pesticide and pharmaceutical intermediate, widely used in the synthesis of nicotinoid insecticides, such as imidacloprid, acetamiprid, etc. The traditional synthesis method of 2-chloro-5-chloromethylpyridine includes a methyl chloride method, an N-oxidation method, and a cyclopentadiene route using 3-methylpyridine as a raw material. Among them, in the prior art, such as the patent application of CN107043349A, it discloses a 2-chloro-5-chloromethylpyridine refining method, wherein the intermediate 2-chloro-2-chloromethyl-4-cyanobutyraldehyde is subjected to a cyclization reaction at high temperature with phosphorus oxychloride in the presence of reagents such as N, N-dimethylformamide and toluene to obtain 2-chloro-5-chloromethylpyridine. Then, after hydrolysis, neutralization, solvent removal, and rectification, a 2-chloro-5-chloromethylpyridine product is obtained, and the content of the 2-chloro-5-chloromethylpyridine product is 92-95%. In the post-treatment, in order to remove impurities, during the hydrolysis and neutralization, not only a large amount of difficult-to-treat tar-containing wastewater with high COD and high ammonia nitrogen will be produced, but also water and alkali will damage 2-chloro-5-chloromethylpyridine, affecting the yield. At the same time, since 2-chloro-5-chloromethylpyridine is a heat-sensitive substance, it is easy to decompose during the distillation and purification process, resulting in low content and yield.

[0003] For example, patent application CN101948424A discloses a method for preparing 2-chloro-5-chloromethylpyridine, in which phosphorus oxychloride is replaced by chlorination reagents such as triphosgene and phosgene, thereby reducing the consumption of N,N-dimethylformamide, and also reducing the amount of water used and wastewater generated in post-treatment. However, a large amount of wastewater with high COD and high ammonia nitrogen will still be produced, and there is also a problem that 2-chloro-5-chloromethylpyridine is decomposed more during distillation purification, thus affecting the content and yield.

[0004] For example, the patent application CN102491943A discloses an improved synthesis process of 2-chloro-5-chloromethylpyridine, which uses a toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde to react with a toluene solution of triphosgene to obtain 2-chloro-5-chloromethylpyridine. Then, a certain amount of trialkylamine is added, and the trialkylamine hydrochloride is separated by suction filtration. The filtrate is distilled and desolventized, and then the product 2-chloro-5-chloromethylpyridine is obtained by vacuum distillation. Although the use of water is omitted, the yield of 2-chloro-5-chloromethylpyridine product is about 70%. Summary of the invention

[0005] In order to improve the content and yield of 2-chloro-5-chloromethylpyridine product and reduce the amount of wastewater generated in the purification process, the present application provides a method for purifying 2-chloro-5-chloromethylpyridine synthetic liquid, using the following technical scheme:

[0006] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution mainly comprises the following steps:

[0007] S1, removing toluene from the 2-chloro-5-chloromethylpyridine synthetic liquid by vacuum distillation to obtain a distillation bottom liquid;

[0008] S2, adding an extractant to the distilled bottom liquid, extracting, standing and stratifying, and collecting the upper layer liquid to obtain an extract;

[0009] S3, heating the extract and distilling it to remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine;

[0010] S4, adding a calcium salt stabilizer to the crude 2-chloro-5-chloromethylpyridine, collecting the distillate by high vacuum distillation, and obtaining a 2-chloro-5-chloromethylpyridine product;

[0011] Wherein, the extractant is an ether extractant, or the extractant is a mixed solvent of an ether extractant and an alkane extractant.

[0012] The purification method of the synthetic liquid of 2-chloro-5-chloromethylpyridine of the present application first performs vacuum distillation on the synthetic liquid of 2-chloro-5-chloromethylpyridine to remove toluene. Then an extractant is used for extraction, the upper liquid is the extractant layer, the lower liquid is the tar layer, N, N-dimethylformamide, intermediate oxidation products and other impurities are left in the tar layer, and 2-chloro-5-chloromethylpyridine is transferred to the extractant, thereby achieving extraction, and then vacuum distillation is performed to remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine product. Further, in the presence of a calcium salt stabilizer, high vacuum distillation is performed to distill out 2-chloro-5-chloromethylpyridine to obtain a 2-chloro-5-chloromethylpyridine product.

[0013] The purification method of the present application utilizes the mutual coordination between the various steps to make the content of the 2-chloro-5-chloromethylpyridine product greater than 96% and the yield greater than 81%, showing the characteristics of high content, high yield and simple purification process, and is suitable for industrial production.

[0014] At the same time, in the purification method of the present application, in the extraction treatment, the extractant is an ether extractant, or the extractant is a mixed solvent of an ether extractant and an alkane extractant. The ether extractant can transfer more 2-chloro-5-chloromethylpyridine from the distillation bottom liquid to the extractant, and more impurities remain in the distillation bottom liquid, that is, the extraction rate is improved. On this basis, an alkane extractant is added to the ether extractant, and the polarity of the ether extractant is further improved by using the alkane extractant. Moreover, in the extraction treatment, not only the impurity content is reduced, but also the destruction of 2-chloro-5-chloromethylpyridine by water and alkali during the hydrolysis and neutralization process is avoided, which is conducive to separating more 2-chloro-5-chloromethylpyridine, and the use of the extractant process instead of the hydrolysis and neutralization process, the extractant can be recycled, no water is introduced, and no large amount of wastewater is generated due to the introduction of water.

[0015] In the process of collecting the distillate by high vacuum distillation, a calcium salt stabilizer is added to the crude 2-chloro-5-chloromethyl pyridine, and the calcium salt stabilizer is used to improve the stability of 2-chloro-5-chloromethyl pyridine at high temperature, reduce the decomposition loss of 2-chloro-5-chloromethyl pyridine, and improve the content and yield of the 2-chloro-5-chloromethyl pyridine product.

[0016] Optionally, the ether extractant is one or more of methyl tert-butyl ether, diethyl ether, and ethyl tert-butyl ether, and / or the alkane extractant is one or more of n-hexane, cyclohexane, and petroleum ether. Optimizing the ether extractant and the alkane extractant can improve the extraction efficiency and selectivity of the extractant.

[0017] Optionally, the extractant is a mixed solvent of an ether extractant and an alkane extractant, and the weight ratio of the ether extractant to the alkane extractant is 1:(0.05-0.5).

[0018] The extractant is a combination of an ether extractant and an alkane extractant, and the ratio of the two is reasonably prepared. The mutual cooperation between the two is beneficial to the separation of 2-chloro-5-chloromethylpyridine and impurities, improves the extraction effect of 2-chloro-5-chloromethylpyridine, and increases the content and quality of the 2-chloro-5-chloromethylpyridine product.

[0019] Optionally, the amount of the extractant added is 1-5 times the total weight of the distillation bottom liquid. Preferably, the amount of the extractant added is 1-3 times the total weight of the distillation bottom liquid. The amount of the extractant added is optimized so that 2-chloro-5-chloromethylpyridine is fully dissolved in the extractant to ensure the extraction effect.

[0020] Optionally, the calcium salt stabilizer is one or more of calcium carbonate, calcium bicarbonate, calcium acetate, and calcium stearate. The calcium salt stabilizer is optimized to facilitate the selection of the calcium salt stabilizer.

[0021] Optionally, the calcium salt stabilizer is added in an amount of 0.1-1% of the total weight of the crude 2-chloro-5-chloromethylpyridine. The amount of the calcium salt stabilizer added is limited to improve the stability of 2-chloro-5-chloromethylpyridine in high vacuum distillation, reduce the acidity of the 2-chloro-5-chloromethylpyridine product, and increase the content of the 2-chloro-5-chloromethylpyridine product.

[0022] Optionally, in the extraction of step S2, the extraction time is 10-30 min and the temperature is 30-50° C. The extraction time and temperature are optimized to allow the 2-chloro-5-chloromethylpyridine in the distillation bottom liquid to fully contact with the extractant, thereby improving the extraction rate.

[0023] Optionally, in the extraction of step S2, the extractant is divided into multiple portions and multiple extractions are performed. Dividing the extractant into multiple portions and performing multiple extractions can effectively remove impurities in the distillation bottom liquid and increase the content of the 2-chloro-5-chloromethylpyridine product.

[0024] Optionally, in step S3, the temperature of the distillation is 40-90° C. The temperature of the distillation is selected according to different extractants to facilitate the removal of the extractant in the extract and reduce the residual extractant.

[0025] Optionally, in the high vacuum distillation collection distillate treatment in step S4, the high vacuum distillation temperature is 110-130°C and the pressure is (1×10 -1 )-(1×10 -5 ) Pa. Optimizing the temperature and pressure of high vacuum distillation not only facilitates the collection of 2-chloro-5-chloromethylpyridine in the crude 2-chloro-5-chloromethylpyridine product, but also reduces the decomposition of 2-chloro-5-chloromethylpyridine due to excessively high temperature, thereby increasing the content and yield of the 2-chloro-5-chloromethylpyridine product.

[0026] Optionally, the toluene is removed by vacuum distillation, the temperature of the vacuum distillation is 60-80°C and the pressure is (1-9)×10 4 Pa. Optimizing the temperature and pressure of vacuum distillation not only facilitates the removal of toluene in the 2-chloro-5-chloromethylpyridine synthesis solution, but also reduces the decomposition of 2-chloro-5-chloromethylpyridine due to excessive temperature, thereby increasing the yield of 2-chloro-5-chloromethylpyridine product.

[0027] Optionally, the 2-chloro-5-chloromethylpyridine synthesis liquid is a 2-chloro-2-chloromethyl-4-cyanobutyraldehyde toluene solution and a triphosgene toluene solution, and the 2-chloro-5-chloromethylpyridine synthesis liquid is obtained after a cyclization reaction, thereby ensuring the stability of the source of the 2-chloro-5-chloromethylpyridine synthesis liquid.

[0028] Optionally, the 2-chloro-5-chloromethylpyridine synthetic solution is mainly prepared by the following method:

[0029] T1, mixing a 2-chloro-2-chloromethyl-4-cyanobutyraldehyde solution and toluene to obtain a toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde;

[0030] T2, mixing toluene and triphosgene to obtain a toluene solution of triphosgene;

[0031] T3. Heat the toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde to 100-110° C., add the toluene solution of triphosgene dropwise, and after the addition of the toluene solution of triphosgene is completed, continue stirring the cyclization reaction for 1-3 hours, cool to room temperature, and obtain a 2-chloro-5-chloromethylpyridine synthetic solution.

[0032] Optionally, the raw materials of the 2-chloro-2-chloromethyl-4-cyanobutyraldehyde solution mainly include 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and N,N-dimethylformamide, and the weight ratio of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and N,N-dimethylformamide is 97:(15-30).

[0033] Optionally, the weight ratio of the 2-chloro-2-chloromethyl-4-cyanobutyraldehyde solution and toluene is 117:(60-100).

[0034] Optionally, the weight ratio of triphosgene to toluene is 1:(1-3).

[0035] Optionally, the dripping time of the toluene solution of triphosgene is 3-5 hours.

[0036] Optionally, the weight ratio of the toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde to the toluene solution of triphosgene is 197:(170-190).

[0037] In summary, this application has at least the following beneficial effects:

[0038] 1. The purification method of the synthetic liquid of 2-chloro-5-chloromethylpyridine of the present application is first to perform vacuum distillation on the synthetic liquid of 2-chloro-5-chloromethylpyridine to remove toluene. Then an extractant is used for extraction. After that, vacuum distillation is performed to remove the extractant. Further, in the presence of a calcium salt stabilizer, high vacuum distillation is performed to distill out 2-chloro-5-chloromethylpyridine to obtain a 2-chloro-5-chloromethylpyridine product. The purification method of the present application utilizes the mutual coordination between the steps to make the content of the 2-chloro-5-chloromethylpyridine product greater than 96% and the yield greater than 81%, showing the characteristics of high content, high yield and simple purification process, and is suitable for industrial production.

[0039] 2. In the extraction treatment, the extractant is an ether extractant, or a mixed solvent of an ether extractant and an alkane extractant. The extractant can leave impurities such as N,N-dimethylformamide and intermediate oxidation products in the tar layer, and transfer 2-chloro-5-chloromethylpyridine to the extractant, thereby achieving extraction, reducing the impurity content, and avoiding the destruction of 2-chloro-5-chloromethylpyridine by water and alkali during the hydrolysis and neutralization process, which is conducive to separating more 2-chloro-5-chloromethylpyridine. That is, in the purification method, the extractant process is used instead of the hydrolysis and neutralization process, and the extractant can be recycled, without introducing water, and no large amount of wastewater is generated due to the introduction of water.

[0040] 3. In the process of collecting the distillate by high vacuum distillation, a calcium salt stabilizer is added to the crude 2-chloro-5-chloromethylpyridine. The calcium salt stabilizer is used to improve the stability of 2-chloro-5-chloromethylpyridine at high temperature, reduce the decomposition loss of 2-chloro-5-chloromethylpyridine, and improve the content and yield of the 2-chloro-5-chloromethylpyridine product. DETAILED DESCRIPTION

[0041] In order to make the present application easier to understand, the present application will be further described in detail below in conjunction with the examples, which are merely illustrative and are not intended to limit the scope of application of the present application. The raw materials or components used in the present application can be obtained through commercial routes or conventional methods unless otherwise specified.

[0042] Preparation Example

[0043] Preparation Example 1

[0044] A 2-chloro-5-chloromethylpyridine synthetic liquid is mainly prepared by the following method:

[0045] T1. Add toluene to the 2-chloro-2-chloromethyl-4-cyanobutyraldehyde solution, and stir for 3 minutes to obtain a toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde.

[0046] Among them, the raw materials of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde solution include 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and N,N-dimethylformamide, and the weight ratio of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and N,N-dimethylformamide is 97:20. The weight ratio of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde solution and toluene is 117:80.

[0047] T2. Add triphosgene to toluene and stir for 3 minutes to obtain a toluene solution of triphosgene.

[0048] Among them, the weight ratio of triphosgene to toluene is 1:2.

[0049] T3. Heat the toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde to 100° C., add the toluene solution of triphosgene dropwise, and after the addition of the toluene solution of triphosgene is completed, continue stirring the cyclization reaction for 2 hours, cool to 23° C., and obtain a 2-chloro-5-chloromethylpyridine synthetic solution.

[0050] The toluene solution of triphosgene was added dropwise for 4 hours. The weight ratio of the toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde to the toluene solution of triphosgene was 197:180.

[0051] Example

[0052] Example 1

[0053] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution mainly comprises the following steps:

[0054] S1, 2-chloro-5-chloromethylpyridine synthesis liquid, at a temperature of 60 ° C and a pressure of 2 × 10 4 Pa, toluene was removed by reduced pressure distillation to obtain a distillation bottom liquid.

[0055] Among them, the 2-chloro-5-chloromethylpyridine synthesis liquid is a toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and a toluene solution of triphosgene, and the 2-chloro-5-chloromethylpyridine synthesis liquid is obtained after a cyclization reaction, and is prepared by the method of Preparation Example 1.

[0056] S2. Add an extractant to the distillation bottom liquid, the amount of the extractant added is 3 times the total weight of the distillation bottom liquid. Then, stir and extract at a temperature of 50° C. for 10 minutes, stand for stratification and collect the upper layer to obtain an extract.

[0057] Wherein, the extractant is an ether extractant, and the ether extractant is methyl tert-butyl ether.

[0058] S3. The extract is heated to 70° C. and distilled to remove the extractant to obtain a crude product of 2-chloro-5-chloromethylpyridine.

[0059] S4. Add calcium salt stabilizer to the crude 2-chloro-5-chloromethylpyridine, the amount of calcium salt stabilizer added is 0.5% of the total weight of the crude 2-chloro-5-chloromethylpyridine. Then, at a temperature of 120°C and a pressure of 1×10 -3 Pa, and the distillate was collected by high vacuum distillation to obtain 2-chloro-5-chloromethylpyridine product.

[0060] Wherein, the calcium salt stabilizer is calcium carbonate.

[0061] Example 2

[0062] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic liquid, which differs from Example 1 in that in step S2, the amount of the extractant added is different, and the amount of the extractant added is twice the total weight of the distillation bottom liquid.

[0063] Example 3

[0064] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic liquid, which differs from Example 1 in that in step S2, the amount of the extractant added is different, and the amount of the extractant added is 5 times the total weight of the distillation bottom liquid.

[0065] Example 4

[0066] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, which differs from Example 1 in that in step S4, the amount of calcium salt stabilizer added is different, and the amount of calcium salt stabilizer added is 0.1% of the total weight of the crude 2-chloro-5-chloromethylpyridine.

[0067] Example 5

[0068] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, which differs from Example 1 in that in step S4, the amount of calcium salt stabilizer added is different, and the amount of calcium salt stabilizer added is 1% of the total weight of the crude 2-chloro-5-chloromethylpyridine.

[0069] Example 6

[0070] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, which differs from Example 1 in that step S2 and step S3 are different.

[0071] Step S2 specifically includes: adding an extractant to the distillation bottom liquid, wherein the amount of the extractant added is 3 times the total weight of the distillation bottom liquid, and then stirring and extracting at a temperature of 30° C. for 10 minutes, standing to separate layers and collecting the upper layer to obtain an extract.

[0072] Wherein, the extractant is an ether extractant, and the ether extractant is diethyl ether.

[0073] Step S3 specifically comprises: heating the extract at 50° C. to distill and remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine.

[0074] Example 7

[0075] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, which differs from Example 1 in that step S2 and step S3 are different.

[0076] Step S2 specifically includes: adding an extractant to the distillation bottom liquid, wherein the amount of the extractant added is 3 times the total weight of the distillation bottom liquid, and then stirring and extracting at a temperature of 50° C. for 10 minutes, standing to separate layers and collecting the upper layer to obtain an extract.

[0077] Among them, the extractant is a mixed solvent of an ether extractant and an alkane extractant, and the weight ratio of the ether extractant to the alkane extractant is 1:0.09; the ether extractant is methyl tert-butyl ether, and the alkane extractant is cyclohexane.

[0078] Step S3 specifically comprises: heating the extract at 90° C. to distill and remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine.

[0079] Example 8

[0080] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic liquid, which differs from Example 7 in that in step S2, the weight ratios of the ether extractant and the alkane extractant are different, and the weight ratio of the ether extractant to the alkane extractant is 1:0.2.

[0081] Example 9

[0082] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic liquid, which differs from Example 7 in that in step S2, the weight ratios of the ether extractant and the alkane extractant are different, and the weight ratio of the ether extractant to the alkane extractant is 1:0.5.

[0083] Example 10

[0084] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, which differs from Example 1 in that step S2 and step S3 are different.

[0085] In step S2: the extractant is divided into two parts, namely the first extractant and the second extractant, and two extractions are performed.

[0086] Step S2 specifically includes: adding the first extractant to the distillation bottom liquid, wherein the amount of the first extractant added is twice the total weight of the distillation bottom liquid. Then, stirring and extracting the mixture at a temperature of 50° C. for 10 minutes, standing the mixture for stratification, and collecting the first extraction upper layer liquid and the first extraction lower layer liquid.

[0087] Add the second extractant to the lower layer of the first extraction, and the amount of the second extractant added is 1 times the total weight of the distillation bottom liquid. Then, stir and extract at a temperature of 50°C for 10 minutes, stand for stratification and collect the upper layer of the second extraction.

[0088] The upper layer liquid of the first extraction and the upper layer liquid of the second extraction were combined to obtain an extract.

[0089] Among them, the extractant is a mixed solvent of an ether extractant and an alkane extractant, and the weight ratio of the ether extractant to the alkane extractant is 1:0.09; the ether extractant is methyl tert-butyl ether, and the alkane extractant is cyclohexane.

[0090] Step S3 specifically comprises: heating the extract at 90° C. to distill and remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine.

[0091] Embodiment 11

[0092] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, which differs from Example 1 in that step S2 and step S3 are different.

[0093] In step S2: the extractant is divided into two parts, namely the first extractant and the second extractant, and two extractions are performed.

[0094] Step S2 is specifically as follows: adding the first extractant to the distillation bottom liquid, wherein the amount of the first extractant added is twice the total weight of the distillation bottom liquid. Then, stirring and extracting the mixture at a temperature of 30° C. for 10 minutes, standing the mixture for stratification, and collecting the first extraction upper layer liquid and the first extraction lower layer liquid.

[0095] Add the second extractant to the lower layer of the first extraction, and the amount of the second extractant added is 1 times the total weight of the distillation bottom liquid. Then, stir and extract at a temperature of 30°C for 10 minutes, stand for stratification and collect the upper layer of the second extraction.

[0096] The upper layer liquid of the first extraction and the upper layer liquid of the second extraction were combined to obtain an extract.

[0097] Among them, the extractant is a mixed solvent of an ether extractant and an alkane extractant, and the weight ratio of the ether extractant to the alkane extractant is 1:0.2; the ether extractant is diethyl ether, the alkane extractant is petroleum ether, and the boiling point of petroleum ether is 60°C.

[0098] Step S3 specifically comprises: heating the extract at 80° C. to distill and remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine.

[0099] Comparative Example

[0100] Comparative Example 1

[0101] A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution mainly comprises the following steps:

[0102] S1. The synthetic liquid of 2-chloro-5-chloromethylpyridine is allowed to stand for stratification to obtain an upper toluene liquid and a lower tar liquid.

[0103] Among them, the 2-chloro-5-chloromethylpyridine synthesis liquid is a toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and a toluene solution of triphosgene, and the 2-chloro-5-chloromethylpyridine synthesis liquid is obtained after a cyclization reaction, and is prepared by the method of Preparation Example 1.

[0104] S2. Add toluene to the lower layer of tar liquid. The amount of toluene added is 3 times the total weight of the lower layer of tar liquid. Stir and extract for 10 minutes. Let stand to separate the layers and collect the upper layer to obtain a toluene extract.

[0105] S3. Combine the toluene extract and the upper toluene liquid to obtain a crude extract.

[0106] S4. At a temperature of 50°C, add water to the crude extract in an amount of 20% of the total weight of the crude extract, stir and hydrolyze for 1 hour, let stand to separate the layers and collect the upper layer to obtain a hydrolyzed purified liquid.

[0107] S5. Add an alkaline solution to the hydrolyzed purified liquid and adjust the pH value to 8, let it stand for stratification and collect the upper layer to obtain a neutralized purified liquid.

[0108] The alkaline solution is a sodium hydroxide solution, and the mass concentration of sodium hydroxide in the sodium hydroxide solution is 30%.

[0109] S6, the neutralized purified liquid is heated at a temperature of 60°C and a pressure of 2×10 4 Pa, toluene was removed by reduced pressure distillation to obtain crude 2-chloro-5-chloromethylpyridine.

[0110] S7, 2-chloro-5-chloromethylpyridine crude product, at a temperature of 120 ° C and a pressure of 1 × 10 -3 Pa, and the distillate was collected by high vacuum distillation to obtain 2-chloro-5-chloromethylpyridine product.

[0111] Performance Testing

[0112] (1) The 2-chloro-5-chloromethylpyridine synthetic solution was purified by the purification methods of Examples 1-11 and Comparative Example 1, respectively, to obtain a 2-chloro-5-chloromethylpyridine product, and the content and yield of the 2-chloro-5-chloromethylpyridine product were tested. The test results are shown in Table 1.

[0113] Table 12-chloro-5-chloromethylpyridine product content and yield testing results

[0114]

[0115]

[0116] As can be seen from Table 1, the purification method of the 2-chloro-5-chloromethylpyridine synthetic liquid of the present application, through the mutual coordination between the steps, makes the 2-chloro-5-chloromethylpyridine product have a higher content and yield, the content is 96.1-96.8%, and the yield is 81.1-82.6%. It has the characteristics of high content and high yield, and is suitable for industrial production.

[0117] Compare Example 1 with Example 7. The extractant in Example 1 is an ether extractant; the extractant in Example 7 is a mixed solvent of an ether extractant and an alkane extractant. It can be seen that the extractant is a mixed solvent of an ether extractant and an alkane extractant, and the cooperation between them can increase the content of the 2-chloro-5-chloromethylpyridine product.

[0118] Compare Example 7 with Example 10. In Example 7, the extraction was performed once with the extractant; in Example 10, the extraction was performed twice with the extractant. It can be seen that multiple extractions are beneficial to increasing the content of the 2-chloro-5-chloromethylpyridine product.

[0119] (2) Take the 2-chloro-5-chloromethylpyridine product obtained in Comparative Example 1, the content of the 2-chloro-5-chloromethylpyridine product is 93.5% and the acidity is 0.40%. Add a calcium salt stabilizer to the 2-chloro-5-chloromethylpyridine product, the amount of the calcium salt stabilizer added is 0.5% of the total weight of the 2-chloro-5-chloromethylpyridine crude product, obtain a mixed solution, and use it as a sample. Then, at a temperature of 130°C, the mixed solution is allowed to stand for 6 hours to obtain a high-temperature treated 2-chloro-5-chloromethylpyridine product. The content and acidity of the high-temperature treated 2-chloro-5-chloromethylpyridine product are tested. At the same time, a blank control group is made, and no calcium salt stabilizer is added to the 2-chloro-5-chloromethylpyridine product of the blank control group. The test results are shown in Table 2.

[0120] Among them, in the mixed liquid of sample 1, the calcium salt stabilizer added is calcium carbonate.

[0121] The mixed solution of sample 2, wherein the added calcium salt stabilizer is calcium bicarbonate.

[0122] The mixed solution of sample 3, wherein the added calcium salt stabilizer is calcium acetate.

[0123] The mixed solution of sample 4, wherein the added calcium salt stabilizer is calcium stearate.

[0124] Table 2 Test results of calcium salt stabilizer stability

[0125]

[0126] As can be seen from Table 2, calcium salt stabilizer is added to 2-chloro-5-chloromethyl pyridine product, and high temperature treatment is carried out, the decomposition of 2-chloro-5-chloromethyl pyridine at high temperature can be effectively reduced, and the stability of 2-chloro-5-chloromethyl pyridine at high temperature is improved. Further, in conjunction with the method for purification of the present application, in step S4, in the high vacuum distillation treatment of 2-chloro-5-chloromethyl pyridine crude product, calcium salt stabilizer is added to 2-chloro-5-chloromethyl pyridine crude product, the stability of 2-chloro-5-chloromethyl pyridine at high temperature can be improved, the decomposition of 2-chloro-5-chloromethyl pyridine is reduced, the content of 2-chloro-5-chloromethyl pyridine product is improved, and the purification treatment of 2-chloro-5-chloromethyl pyridine synthetic solution is conducive to.

[0127] It should be noted that the embodiments described above are only used to explain the present application and do not constitute any limitation to the present application. The present application is described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present application may be modified as specified within the scope of the claims of the present application, and the present invention may be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein. On the contrary, the present application can be extended to all other methods and applications with the same functions.

Claims

1. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution, characterized in that: The main steps are as follows: S1, removing toluene from the 2-chloro-5-chloromethylpyridine synthetic liquid by vacuum distillation to obtain a distillation bottom liquid; S2, adding an extractant to the distilled bottom liquid, extracting, standing and stratifying, and collecting the upper layer liquid to obtain an extract; S3, heating the extract and distilling it to remove the extractant to obtain a crude 2-chloro-5-chloromethylpyridine; S4, adding a calcium salt stabilizer to the crude 2-chloro-5-chloromethylpyridine, collecting the distillate by high vacuum distillation, and obtaining a 2-chloro-5-chloromethylpyridine product; Wherein, the extractant is an ether extractant, or the extractant is a mixed solvent of an ether extractant and an alkane extractant.

2. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: The ether extractant is one or more of methyl tert-butyl ether, diethyl ether, and ethyl tert-butyl ether, and / or the alkane extractant is one or more of n-hexane, cyclohexane, and petroleum ether.

3. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: The extractant is a mixed solvent of an ether extractant and an alkane extractant, and the weight ratio of the ether extractant to the alkane extractant is 1:(0.05-0.5).

4. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: The amount of the extractant added is 1-5 times the total weight of the distillation bottom liquid.

5. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: The calcium salt stabilizer is one or more of calcium carbonate, calcium bicarbonate, calcium acetate and calcium stearate.

6. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: The calcium salt stabilizer is added in an amount of 0.1-1% of the total weight of the crude 2-chloro-5-chloromethylpyridine.

7. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: In the extraction of step S2, the extraction time is 10-30 minutes and the temperature is 30-50°C.

8. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: In step S3, the distillation temperature is 40-90°C to remove the extractant.

9. A method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: In the high vacuum distillation collection distillate treatment in step S4, the high vacuum distillation temperature is 110-130°C and the pressure is (1×10 -1 )-(1×10 -5 )Pa.

10. The method for purifying a 2-chloro-5-chloromethylpyridine synthetic solution according to claim 1, characterized in that: The 2-chloro-5-chloromethylpyridine synthesis liquid is a toluene solution of 2-chloro-2-chloromethyl-4-cyanobutyraldehyde and a toluene solution of triphosgene, and the 2-chloro-5-chloromethylpyridine synthesis liquid is obtained after a cyclization reaction.

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