Continuous crystallization production method of 2, 2, 6, 6-tetramethyl-4-piperidylamine

Abstract

The invention belongs to the technical field of continuous crystallization and purification, and relates to a continuous crystallization production method of 2, 2, 6, 6-tetramethyl-4-piperidylamine, which comprises the following steps: controlling the temperature of a crystallization kettle to be-10-15 DEG C, conveying a saturated or nearly saturated solution of the 2, 2, 6, 6-tetramethyl-4-piperidylamine at 55-65 DEG C into the crystallization kettle, and after the solid content in a crystallizer reaches 15-55%, cooling to room temperature to obtain the 2, 2, 6, 6-tetramethyl-4-piperidylamine. The crystal mush continuously flows into a centrifugal machine through a pipeline for solid-liquid separation, obtained crystals are washed with an organic solvent and dried, and a 2, 2, 6, 6-tetramethyl-4-piperidylamine product with the purity larger than or equal to 99.5% is obtained. The method disclosed by the invention has the advantages of improving the production efficiency, improving the product quality stability, reducing the production cost and the like, realizes continuous production of the 2, 2, 6, 6-tetramethyl-4-piperidylamine crystal, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of continuous crystallization purification, and relates to a continuous crystallization production method of 2,2,6,6-tetramethyl-4-piperidineamine. Background Art

[0002] 2,2,6,6-Tetramethyl-4-piperidineamine is an important organic chemical raw material and has wide applications in the fields of light stabilizers, pharmaceutical intermediates, pesticide intermediates, etc. The traditional production process of 2,2,6,6-tetramethyl-4-piperidineamine is mostly an intermittent crystallization process, and this process has many drawbacks. For example, the production efficiency is low. Each batch of production needs to go through multiple steps such as feeding, reaction, crystallization, and separation, and manual intervention and waiting are required between each step, resulting in a long production cycle. At the same time, the product quality stability of the intermittent process is poor. Since the operating conditions of each batch are difficult to be completely consistent, the indicators such as the purity and crystal form of the product fluctuate greatly. In addition, the intermittent process has high energy consumption, low equipment utilization rate, and high production costs, and it has been difficult to meet the growing market demand.

[0003] Currently, 2,2,6,6-tetramethyl-4-piperidineamine is often prepared by catalytic amination method as follows:

[0004] Chinese Patent CN119080678A discloses a preparation method of 2,2,6,6-tetramethyl-4-piperidineamine compounds. Mix 2,2,6,6-tetramethyl-4-piperidone, a novel catalyst, and a solvent, remove the air in the reaction vessel, then add an amine compound and introduce hydrogen gas. Separate the obtained solid-liquid mixture, and the liquid phase is subjected to rotary evaporation and distillation to obtain 2,2,6,6-tetramethyl-4-piperidineamine compounds. This method has a complex process, a high risk coefficient for the hydrogenation process, and high energy consumption and costs.

[0005] Chinese Patent CN110526860A discloses a method for preparing the intermediate 2,2,6,6-tetramethylpiperidineamine. Add ammonium nitrate as a catalyst to acetone and ammonia gas to react to generate piperidone and water; then add a catalyst, nickel skeleton modified by hydroxy phenyl sodium phosphate, to make piperidone react with ammonia gas to generate 2,2,6,6-tetramethylpiperidineimine and water, and make 2,2,6,6-tetramethylpiperidineimine react with hydrogen gas to generate 2,2,6,6-tetramethylpiperidineamine. The process includes steps such as rectification and crystallization, with a long operation time, introducing a catalyst, and subsequent issues related to recovery costs.

[0006] Chinese Patent CN1346825A discloses a preparation method of a light stabilizer intermediate, 2,2,6,6-tetramethyl-4-piperidinamine compound. Using 2,2,6,6-tetramethyl-4-piperidone as the raw material, the preparation is completed through three steps: premixing reaction, vacuum distillation for dehydration, and hydrogenation. However, the purity of the obtained finished product is only about 98%, which is relatively low.

[0007] Chinese Patent CN112724072A discloses a method for synthesizing 2,2,6,6-tetramethyl-4-piperidinamine without a catalyst. 2,2,6,6-tetramethyl-4-piperidone and ammonium formate are added to a reactor for the Leuckart reaction to obtain 2,2,6,6-tetramethyl-4-piperidinamine. During the process, low-boiling by-products need to be removed by rectification, resulting in relatively high energy consumption, and the purity of the obtained product is low.

[0008] For the above methods, most of them use a combination of catalytic reaction, rectification, and crystallization to prepare 2,2,6,6-tetramethyl-4-piperidinamine, which requires multiple steps, resulting in a long production cycle. At the same time, the product quality stability of the batch process is poor. Since the operating conditions of each batch are difficult to be completely consistent, the indicators such as the purity and particle size of the product fluctuate greatly. Moreover, during the rectification process, the material is evaporated and condensed multiple times, resulting in high energy consumption. In some methods, a catalyst is introduced, and the subsequent problem of recovery and treatment needs to be considered. Summary of the Invention

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a continuous crystallization production method for 2,2,6,6-tetramethyl-4-piperidinamine. This method can stabilize the product quality, greatly reduce the production cost, and achieve intelligent control and one-key start. Finally, a 2,2,6,6-tetramethyl-4-piperidinamine product with a purity ≥ 99.5% is prepared, and industrial large-scale production is realized.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A continuous crystallization production method for 2,2,6,6-tetramethyl-4-piperidinamine, comprising the following steps:

[0012] 1) Raw material preparation: Dissolve the 2,2,6,6-tetramethyl-4-piperidinamine crude product with a mass percentage content of 85 - 90 wt% in an organic solvent and water, and the mass ratio of the organic solvent to water is 1:1 - 2 to prepare a saturated or nearly saturated solution of 2,2,6,6-tetramethyl-4-piperidinamine at a preparation temperature of 55 - 65 °C;

[0013] 2) Continuous crystallization: Control the temperature of the crystallization kettle at -10 to 15°C, continuously feed a saturated or nearly saturated solution of 2,2,6,6-tetramethyl-4-piperidineamine into the crystallization kettle at a certain flow rate until the set liquid level of the crystallizer is reached. The crystallization residence time is 1 - 10 h. After the solid content in the crystallizer reaches 15 - 55%, continuously discharge the crystal slurry, and continuously feed the raw material liquid into the crystallizer.

[0014] 3) Solid-liquid separation and drying: Centrifuge the crystal slurry obtained in 2) for solid-liquid separation, return the mother liquor to the crystallizer, and after the crystals are washed and dried, obtain a 2,2,6,6-tetramethyl-4-piperidineamine product with a purity ≥ 99.5%.

[0015] Preferably, the organic solvent in step 1) is one or more of ethanol, methanol, and acetone. Further preferably acetone because of its good solubility and volatility, which can effectively promote the crystallization process.

[0016] Preferably, the mass ratio of the organic solvent to water in step 1) is 1:1 - 1.2.

[0017] Preferably, the temperature of the crystallization kettle in step 2) is set at -5 to 10°C.

[0018] Preferably, the crystallization residence time in step 2) is 2 - 8 h.

[0019] Preferably, in step 2), the crystal slurry is discharged after the solid content in the crystallizer reaches 20 - 40%.

[0020] Preferably, in step 2), control the ratio of the raw material feed flow rate to the crystallization circulation flow rate to maintain a constant liquid level in the crystallizer.

[0021] Preferably, the solvent required for washing the crystals in step 3) is a non-polar solvent, which is one or more of ether, toluene, ethane, and dichloromethane. Further preferably ether.

[0022] Advantages and beneficial effects of the present invention:

[0023] 1. Greatly improved production efficiency: The continuous crystallization process realizes uninterrupted production from raw material crude products to high-purity products. Compared with the traditional batch process, the production cycle is greatly shortened.

[0024] 2. Stable product quality and high efficiency in operation: Continuous crystallization can achieve intelligent control and one-key start. By precisely controlling various parameters in the continuous crystallization process, the quality of each batch of products can be kept highly consistent. The product purity can reach more than 99.5%, with high purity and uniform particle size, which is beneficial for subsequent processing and application.

[0025] 3. Reduction of production costs: Continuous production improves equipment utilization rate, reduces manual intervention, and lowers energy consumption and raw material waste, thus effectively reducing equipment investment, operating costs, and labor costs, enhancing the market competitiveness of products and the economic benefits of the factory. Detailed implementation manners

[0026] In order to enable those skilled in the art of this technology to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the best implementation cases.

[0027] Example 1

[0028] A continuous crystallization production method of 2,2,6,6 - tetramethyl - 4 - piperidineamine, comprising:

[0029] Dissolve the crude product of 2,2,6,6 - tetramethyl - 4 - piperidineamine with a mass percentage of 85wt% in acetone and water, with the mass ratio of acetone to water being 1:1.2, to prepare a saturated or nearly saturated solution of 2,2,6,6 - tetramethyl - 4 - piperidineamine at a temperature of 65°C. Control the temperature of the crystallization kettle at 8°C, continuously feed the solution into the crystallization kettle until the set liquid level of the crystallizer is reached, and stay for 6 hours for crystallization. When the solid content in the crystallizer reaches 20%, continuously discharge the crystal slurry through a pipeline, continuously feed the raw material liquid into the crystallizer, control the ratio of the raw material feed flow rate to the crystallization circulation flow rate, and maintain the liquid level in the crystallizer unchanged. Discharge the crystal slurry into a centrifuge for solid - liquid separation, return the mother liquor to the crystallizer, wash the crystals with ether, and after drying, obtain the product of 2,2,6,6 - tetramethyl - 4 - piperidineamine with a purity of 99.75wt%.

[0030] Example 2

[0031] A continuous crystallization production method of 2,2,6,6 - tetramethyl - 4 - piperidineamine, comprising:

[0032] Dissolve the crude product of 2,2,6,6 - tetramethyl - 4 - piperidineamine with a mass percentage of 85wt% in acetone and water, with the mass ratio of acetone to water being 1:1.2, to prepare a saturated or nearly saturated solution of 2,2,6,6 - tetramethyl - 4 - piperidineamine at a temperature of 65°C. Control the temperature of the crystallization kettle at 4°C, continuously feed the solution into the crystallization kettle until the set liquid level of the crystallizer is reached, and stay for 6 hours for crystallization. When the solid content in the crystallizer reaches 33%, continuously discharge the crystal slurry through a pipeline, continuously feed the raw material liquid into the crystallizer, control the ratio of the raw material feed flow rate to the crystallization circulation flow rate, and maintain the liquid level in the crystallizer unchanged. Discharge the crystal slurry into a centrifuge for solid - liquid separation, return the mother liquor to the crystallizer, wash the crystals with ether, and after drying, obtain the product of 2,2,6,6 - tetramethyl - 4 - piperidineamine with a purity of 99.71wt%.

[0033] Example 3

[0034] A continuous crystallization production method of 2,2,6,6-tetramethyl-4-piperidineamine, comprising:

[0035] Dissolve the crude product of 2,2,6,6-tetramethyl-4-piperidineamine with a mass percentage of 85 wt% in acetone and water, with the mass ratio of acetone to water being 1:1.2, to prepare a saturated or nearly saturated solution of 2,2,6,6-tetramethyl-4-piperidineamine at a temperature of 65 °C. Control the temperature of the crystallization kettle to 0 °C, continuously feed the solution into the crystallization kettle until the set liquid level of the crystallizer is reached, stay for 6 h for crystallization, when the solid content in the crystallizer reaches 40%, continuously discharge the crystal slurry through a pipeline, continuously feed the raw material liquid into the crystallizer, control the ratio of the raw material feed flow rate to the crystallization circulation flow rate, and maintain the liquid level in the crystallizer unchanged. Discharge the crystal slurry into a centrifuge for solid-liquid separation, return the mother liquor to the crystallizer, wash the crystals with ether, and after drying, obtain the product as 2,2,6,6-tetramethyl-4-piperidineamine with a purity of 99.55 wt%.

[0036] Example 4

[0037] A continuous crystallization production method of 2,2,6,6-tetramethyl-4-piperidineamine, comprising:

[0038] Dissolve the crude product of 2,2,6,6-tetramethyl-4-piperidineamine with a mass percentage of 85 wt% in acetone and water, with the mass ratio of acetone to water being 1:1.2, to prepare a saturated or nearly saturated solution of 2,2,6,6-tetramethyl-4-piperidineamine at a temperature of 65 °C. Control the temperature of the crystallization kettle to 4 °C, continuously feed the solution into the crystallization kettle until the set liquid level of the crystallizer is reached, stay for 3 h for crystallization, when the solid content in the crystallizer reaches 21%, continuously discharge the crystal slurry through a pipeline, continuously feed the raw material liquid into the crystallizer, control the ratio of the raw material feed flow rate to the crystallization circulation flow rate, and maintain the liquid level in the crystallizer unchanged. Discharge the crystal slurry into a centrifuge for solid-liquid separation, return the mother liquor to the crystallizer, wash the crystals with ether, and after drying, obtain the product as 2,2,6,6-tetramethyl-4-piperidineamine with a purity of 99.51 wt%.

[0039] The above content is only a preferred example of the present invention. For those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. The content of this specification should not be construed as a limitation to the present invention.

Claims

1. A continuous crystallization production method for 2,2,6,6-tetramethyl-4-piperidinamine, characterized in that: The following steps are involved: 1) Raw material preparation: dissolving a crude product of 2,2,6,6-tetramethyl-4-piperidinamine with a mass percentage of 85-90wt% in an organic solvent and water, wherein the mass ratio of the organic solvent to water is 1:1-2, and preparing a saturated or nearly saturated solution of 2,2,6,6-tetramethyl-4-piperidinamine at a temperature of 55-65°C; 2) Continuous crystallization: controlling the temperature of the crystallization kettle to -10 to 15°C, continuously passing a saturated or nearly saturated solution of 2,2,6,6-tetramethyl-4-piperidinamine into the crystallization kettle at a certain flow rate until the liquid level set in the crystallizer is reached, the crystallization residence time is 1 to 10 hours, and after the solid content in the crystallizer reaches 15 to 55%, the crystal slurry is continuously discharged, and the raw material liquid is continuously discharged into the crystallizer; 3) Solid-liquid separation and drying: The crystal slurry obtained in 2) is centrifuged for solid-liquid separation, and the mother liquor is returned to the crystallizer. After the crystals are washed and dried, a 2,2,6,6-tetramethyl-4-piperidinamine product with a purity of ≥99.5% is obtained.

2. The continuous crystallization production method according to claim 1, characterized in that: In step 1), the organic solvent is one or more of ethanol, methanol and acetone.

3. The continuous crystallization production method according to claim 1, characterized in that: In step 1), the mass ratio of the organic solvent to water is 1:1 to 1.

2.

4. The continuous crystallization production method according to claim 1, characterized in that: Step 2) The temperature of the crystallization kettle is set at -5 to 10°C.

5. The continuous crystallization production method according to claim 1, characterized in that: Step 2) The crystallization residence time is 2-8h.

6. The continuous crystallization production method according to claim 1, characterized in that: In step 2), the solid content in the crystallizer is discharged after reaching 20-40%.

7. The continuous crystallization production method according to claim 1, characterized in that: Step 3) Control the feed rate and crystallization circulation flow rate to maintain a constant liquid level in the crystallizer.

8. The continuous crystallization production method according to claim 1, characterized in that: Step 3) The washing solvent is one or more of ether, toluene, ethane and dichloromethane.