Method and system for separating acetone from tetramethylpiperidone reaction liquid

Abstract

The invention relates to a method for separating acetone in a tetramethylpiperidone reaction liquid, which adopts a double-tower continuous rectification system to separate acetone in the tetramethylpiperidone reaction liquid, and the double-tower continuous rectification system is used for treating the reaction liquid through two rectification towers in sequence. Separation is continuously carried out, separation efficiency is remarkably improved, separation time is shortened, and equipment size is reduced.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, specifically relating to a method and system for separating acetone from a tetramethylpiperidone reaction solution. Background Technology

[0002] Triacetone amine, chemically named 2,2,6,6-tetramethylpiperidinone, is an important intermediate for hindered amine light stabilizers and pharmaceutical intermediates. Especially in the field of hindered amine light stabilizers, triacetone amine is the only parent nucleus of hindered amine light stabilizer piperidine derivatives and is an important raw material for the synthesis of tetramethylpiperidinol, tetramethylpiperidinamine, and polymerization inhibitor 702.

[0003] The preparation of triacetone amine typically uses acetone and ammonia as raw materials, reacting in the presence of an acidic catalyst. To improve the conversion rate and selectivity, an excess of acetone is usually used industrially, typically 1.5-2.0 times the theoretical amount. Simultaneously, a large amount of water is generated at the end of the reaction. Excess acetone and water need to be effectively separated and recovered. In China, triacetone amine industrial production generally uses concentrated alkali extraction or distillation to dehydrate the synthesis liquid. The former uses a concentrated alkali of over 40% to extract water from the synthesis liquid; after the concentrated alkali absorbs water, it needs to be concentrated again by vacuum distillation before reuse, resulting in high energy consumption and severe equipment corrosion. In the latter, during distillation, some triacetone amine intermediates form azeotropes with water, affecting water separation, leading to high energy consumption and low efficiency. The separation of acetone and water faces the following challenges: 1) Azeotropic phenomenon: Acetone and water form an azeotrope under normal pressure (acetone content approximately 88%), making it difficult to obtain high-purity acetone through conventional distillation. 2) High water content: The water content in the reaction solution after treatment is as high as about 30%, requiring a large amount of energy for separation. 3) Continuous production requirements: Modern chemical production requires the separation process to be carried out continuously in order to improve production efficiency.

[0004] Patent CN117903042A discloses a dual-tower synthesis method for tetramethylpiperidinone, employing a dual-tower reactive distillation apparatus to couple the reaction and separation within the same device. The first tower is a reactive distillation tower for the reaction of acetone and ammonia; the second tower is a product distillation tower for separating tetramethylpiperidinone and unreacted acetone. The patent does not specifically optimize the acetone-water separation process, resulting in an acetone recovery rate of only 90-95% and high energy consumption.

[0005] Patent CN102659671A discloses a method for preparing tetramethylpiperidone, using acetone and ammonia as raw materials, reacting them in the presence of a catalyst to produce tetramethylpiperidone, and separating the reaction products by distillation and rectification. The patent mainly optimizes the catalyst and process formulation, and employs traditional distillation and rectification to separate acetone.

[0006] Patent CN107602447A discloses a production process for tetramethylpiperidone, employing a combination of a high-pressure column (1.2-1.5 atm) and a low-pressure column (0.5-0.8 atm) to achieve efficient separation of acetone and water through differential pressure distillation, achieving an acetone purity ≥99.5% and a recovery rate ≥99%. However, the equipment is large in size, and its mass transfer efficiency needs improvement.

[0007] In summary, existing technologies for acetone separation in tetramethylpiperidone production still suffer from problems such as low separation efficiency, high energy consumption, and low recovery rate. Therefore, developing a high-efficiency, energy-saving, and high-recovery continuous acetone separation technology has significant industrial application value. Summary of the Invention

[0008] The purpose of this invention is to provide a method for separating acetone from a tetramethylpiperidone reaction solution. This method uses a dual-tower continuous distillation system to separate acetone from the tetramethylpiperidone reaction solution, which can obtain acetone with high purity and extremely low water content.

[0009] The first aspect of the present invention provides a method for separating acetone from a tetramethylpiperidone reaction solution, wherein a dual-tower continuous distillation system is used to separate acetone from the tetramethylpiperidone reaction solution, wherein the dual-tower continuous distillation system refers to processing the reaction solution sequentially through two distillation towers.

[0010] In some implementations, the separation method includes the following steps:

[0011] S1, add alkali to adjust the pH to alkaline, and preheat the reaction solution;

[0012] S2, the preheated reaction liquid enters the first distillation column for distillation, and acetone-water azeotrope vapor is obtained at the top of the column, and a heavy component containing tetramethylpiperidinone is obtained at the bottom of the column;

[0013] S3, the acetone-water azeotrope obtained in S2 is directly introduced into the second distillation column for distillation, and acetone vapor is recovered at the top of the column.

[0014] In some embodiments, there is a pressure difference between the two distillation columns of the dual-tower continuous separation system, wherein the first distillation column is a high-pressure distillation column, the second distillation column is a low-pressure distillation column, and the pressure difference between the first distillation column and the second distillation column is 0.05-0.08 MPa, preferably 0.06-0.09 MPa.

[0015] In some embodiments, S1 controls the pH to be 11–13; and / or,

[0016] The preheating temperature in S1 is 60-70℃.

[0017] In some embodiments, the first distillation column is a supergravity distillation column; more preferably, the supergravity machine in the supergravity distillation column in S2 rotates at 1000-1200 rpm.

[0018] In some embodiments, the temperature at the top of the column in S2 is controlled at 80-85°C; and / or, the temperature at the bottom of the column in S2 is controlled at 95-105°C.

[0019] In some embodiments, the pressure in S2 is 0.13 to 0.15 MPa.

[0020] In some embodiments, the second distillation column is a supergravity distillation column; more preferably, the supergravity machine in the supergravity distillation column in S3 rotates at 1200-1500 rpm.

[0021] In some embodiments, the temperature at the top of the middle tower in S3 is controlled at 58–60°C; and / or, the temperature at the bottom of the middle tower in S3 is controlled at 70–75°C.

[0022] In some embodiments, the pressure of S3 is 0.06 to 0.07 MPa.

[0023] The present invention also provides a dual-tower continuous distillation system for acetone separation, the dual-tower continuous distillation system comprising: a centrifugal pump, a high-pressure distillation column, a reboiler, a centrifugal pump, and a low-pressure distillation column connected in sequence.

[0024] In some embodiments, both the high-pressure distillation column and the low-pressure distillation column are ultragravity distillation columns. The high-pressure distillation column is the first ultragravity distillation column, and the conditions for the first ultragravity distillation column described above can be used. The low-pressure distillation column is the second ultragravity distillation column, and the conditions for the second ultragravity distillation column described above can be used.

[0025] The present invention has achieved the following positive effects:

[0026] The separation method of this invention employs a dual-tower separation process that is continuous, significantly improving separation efficiency, shortening separation time, and reducing equipment size. By applying hypergravity technology to a dual-tower differential pressure distillation system, the gas-liquid mass transfer is enhanced using a hypergravity field, resulting in a 40-50% increase in separation efficiency and a reduction in energy consumption. Attached Figure Description

[0027] Figure 1 The diagram shows the dual-tower differential pressure distillation system of this application. In the diagram: 1. Centrifugal pump; 2. High-pressure distillation column; 3. Reboiler; 4. Centrifugal pump; 5. Low-pressure distillation column. Detailed Implementation

[0028] The present invention is described in detail below with reference to specific embodiments. However, it should be noted that the scope of protection of the present invention is not limited by these specific embodiments and principle explanations, but is determined by the claims.

[0029] In this invention, except where expressly stated, any matters or issues not mentioned herein are directly applicable to those known in the art without any modification. Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or concepts are considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination clearly unreasonable.

[0030] All features disclosed in this invention can be combined arbitrarily, and such combinations should be understood as the contents disclosed or recorded in this invention, unless those skilled in the art consider such combinations to be obviously unreasonable.

[0031] The numerical points disclosed in this specification include not only the numerical points specifically disclosed in the embodiments, but also the endpoints of each numerical range in the specification. Any combination of these numerical points should be regarded as the range disclosed or recorded in this invention.

[0032] In this invention, the technical and scientific terms that are given a definition shall be used as defined thereon, and those that are not given a definition shall be understood according to their common meaning in the art.

[0033] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly used in the field to which this invention pertains. For the purposes of interpreting this specification, the following definitions will apply, and where appropriate, terms used in the singular will also include the plural forms, and vice versa.

[0034] Unless otherwise indicated, the terms “comprising” and “including” as used herein are used in their open, non-restrictive sense.

[0035] A method for separating acetone from a tetramethylpiperidone reaction solution, comprising using a dual-tower continuous distillation system, wherein the reaction solution is sequentially passed through two distillation towers.

[0036] The tetramethylpiperidone reaction solution described in this invention refers to a reaction solution obtained by reacting acetone and ammonia (such as ammonia gas or ammonia water) as raw materials under an acidic catalyst.

[0037] Preferably, the molar ratio of acetone to ammonia is (3-10):1, for example 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 and any value between them, preferably (4.5-6):1.

[0038]

[0039] During the reaction and processing of tetramethylpiperidone, a large amount of water is generated and introduced. Acetone and water are miscible and difficult to separate, and conventional distillation separation methods are energy-intensive.

[0040] In a specific implementation, the separation method includes the following steps:

[0041] S1, add alkali to adjust the pH to alkaline, and preheat the reaction solution;

[0042] S2, the preheated reaction liquid enters the first distillation column for distillation, and acetone-water azeotrope vapor is obtained at the top of the column, and a heavy component containing tetramethylpiperidinone is obtained at the bottom of the column;

[0043] S3, the acetone-water azeotrope obtained in S2 is directly introduced into the second distillation column for distillation, and acetone vapor is recovered at the top of the column.

[0044] After the synthesis of tetramethylpiperidone is completed, the composition of the feed column is improved by controlling the alkali concentration. Acetone and water are separated by continuous distillation using the differential pressure of the two columns, which realizes the efficient recovery and utilization of acetone. This provides a technological breakthrough for continuous distillation after the continuous synthesis of tetramethylpiperidone, and enables the industrialization of the continuous production process of tetramethylpiperidone.

[0045] Preferably, the acetone vapor obtained by this method, after condensation, has a water content of ≤0.5%, more preferably, it has a water content of ≤0.45%, ≤0.40%, ≤0.35%, ≤0.30%, ≤0.25%, ≤0.20%, or ≤0.25%.

[0046] Studies have shown that when the water content of the separated acetone is ≤0.5%, the purity of the acetone reaches over 99.5%, and it can be used for the next batch of production without any impact. If the water content is greater than 0.5%, it will affect its recycling.

[0047] In a specific embodiment, S1 controls the pH to be between 11 and 13, for example, pH is approximately 11, 11.2, 11.5, 11.8, 12, 12.2, 12.5, 12.8, or 13, preferably between 11.2 and 12.2. More preferably, the alkali includes, but is not limited to, sodium hydroxide. By controlling the concentration of the alkali in the reaction solution when neutralizing the catalyst in the triacetone amine reaction solution, the composition of the inlet column is changed, providing a compositional basis for continuous separation in the dual-tower system.

[0048] In a specific embodiment, the preheating temperature in step S1 is 60–70°C. Preheating vaporizes unreacted acetone after the synthesis of triacetone amine, providing a compositional basis for continuous separation in the dual-tower configuration. This preheating is a commonly used technique in the art and is not particularly limited; a suitable heat source can be selected based on the operating conditions. The preheating temperature ensures the overall reaction liquid temperature is 60–70°C, for example, approximately 60°C, approximately 62°C, approximately 65°C, approximately 68°C, or approximately 70°C. This ensures sufficient vaporization of the unreacted acetone.

[0049] In one specific embodiment, there is a pressure difference between the two distillation columns of the dual-tower continuous separation system. The first distillation column is a high-pressure distillation column, and the second distillation column is a low-pressure distillation column. The pressure difference between the first distillation column and the second distillation column is 0.05-0.08 MPa, more preferably 0.06-0.09 MPa (e.g., 0.07 MPa, 0.08 MPa).

[0050] In one specific embodiment, the first distillation column is a supergravity distillation column, i.e., the first supergravity distillation column.

[0051] Applying centrifugal technology to a dual-tower differential pressure distillation system enhances gas-liquid mass transfer using a centrifugal field, significantly improving separation efficiency and reducing equipment size. A centrifugal distillation column is a device that utilizes the principles of centrifugal technology to enhance the gas-liquid mass transfer process. Essentially, it uses a rotating centrifugal force field to replace the conventional gravity field, greatly increasing the relative velocity of the gas and liquid phases, accelerating phase interface renewal, and multiplying production intensity. This significantly enhances the gas-liquid mass transfer process, achieving the goals of increasing efficiency, reducing equipment size, and lowering energy consumption.

[0052] In a specific implementation, the rotational speed of the supergravity machine in the supergravity distillation column in S2 is 1000-1200 rpm; for example, approximately 1000 rpm, 1100 rpm, or 1200 rpm.

[0053] In a specific embodiment, the pressure in S2 is 0.13–0.15 MPa (e.g., 0.14 MPa);

[0054] In a specific embodiment, the temperature at the top of the tower in S2 is controlled at 80-85℃ (e.g., 80℃, 81℃, 82℃, 83℃, 84℃, 85℃), preferably 82℃.

[0055] In a specific implementation, the temperature at the bottom of the tower in S2 is controlled at 95-105℃ (e.g., 95℃, 98℃, 100℃, 102℃, 105℃), preferably 100℃.

[0056] In a specific embodiment, the heavy component containing tetramethylpiperidone in S2 is transported to the intermediate tower to remove the intermediate, and then enters the product tower for distillation to obtain triacetone amine product.

[0057] In a specific embodiment, the second distillation column is a supergravity distillation column, i.e., the second supergravity distillation column; preferably, the supergravity machine in the supergravity distillation column in S3 rotates at 1200 to 1500 rpm (e.g., 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm).

[0058] In this invention, the rotational speed of the supergravity machine in the second supergravity distillation column is greater than or equal to the rotational speed of the supergravity machine in the first supergravity distillation column. Preferably, the difference between the two is within 500 rpm, for example, 400 rpm, 300 rpm, 200 rpm, or 100 rpm.

[0059] In a specific embodiment, the pressure of S3 is 0.06–0.07 MPa. By setting different pressures in the first and second supergravity distillation columns, acetone, water, products, and impurities are fully separated, ensuring that the purity of acetone reaches over 99.5% and can be directly used as raw material in the reaction stage. The first supergravity distillation column of this invention is also called a supergravity high-pressure distillation column, and the second supergravity distillation column is also called a supergravity low-pressure distillation column.

[0060] In a specific implementation, the temperature at the top of the middle tower in S3 is controlled at 58-60°C;

[0061] In a specific implementation, the temperature at the bottom of the middle tower in S3 is controlled at 70-75°C (e.g., 70°C, 72°C, 74°C, 75°C).

[0062] The present invention also provides a dual-tower continuous distillation system for acetone separation, the dual-tower continuous distillation system comprising: a centrifugal pump, a high-pressure distillation column, a reboiler, a centrifugal pump, and a low-pressure distillation column connected in sequence.

[0063] Preferably, the dual-tower distillation system is the dual-tower distillation system described above.

[0064] Preferably, both the high-pressure distillation column and the low-pressure distillation column are ultragravity distillation columns. The ultragravity high-pressure distillation column is the first ultragravity distillation column, which is applicable to the conditions of the first ultragravity distillation column. The ultragravity low-pressure distillation column is the second ultragravity distillation column, which is applicable to the conditions of the second ultragravity distillation column.

[0065] In a specific implementation, the reboiler connected to the first supergravity distillation column serves as the heat source for the second supergravity distillation column. Specifically, the overhead steam from the first supergravity distillation column is used as the heat source for the reboiler of the second supergravity distillation column, achieving cascaded energy utilization and significantly reducing energy consumption. The integrated heat system recovers and utilizes the latent heat of the overhead steam, reducing energy consumption by 40-45% compared to a traditional single-column system.

[0066] In a specific embodiment, after the S3 distillation, the product is condensed by a condenser and collected from the bottom of the tower as wastewater containing less than 0.1% acetone, which is then treated and discharged.

[0067] In a preferred embodiment of the present invention, the dual-tower distillation system is as follows: Figure 1 As shown, the dual-tower continuous high-gravity distillation system of this application includes a centrifugal pump (1), a high-pressure high-gravity distillation column (2), a reboiler (3), a centrifugal pump (4), and a low-pressure high-gravity distillation column (5) connected in sequence. The preheated tetramethylpiperidone reaction solution is sent to the high-pressure high-gravity distillation column (2) through the centrifugal pump (1), and after treatment, it is rich in tetramethylpiperidone heavy components; the tetramethylpiperidone-containing heavy components are transported to the intermediate column, where intermediates are removed, and then enter the product column for distillation. The top vapor of the high-pressure high-gravity distillation column is used as the heat source for the reboiler of the low-pressure high-gravity distillation column. The acetone-water azeotrope is transported to the low-pressure high-gravity distillation column through the centrifugal pump (4), and after treatment, recoverable acetone vapor is obtained, which can be directly reused in the next batch of synthesis.

[0068] The technical solution of this application will be described in detail below with specific examples.

[0069] The tetramethylpiperidone mentioned in this application is 2,2,6,6-tetramethylpiperidone, which is the same substance as triacetoneamine.

[0070] The acetone described in the examples can be directly recycled and reused, meaning that the water content of the acetone is required to be ≤0.5% for recycling and reuse, and that its application in the next batch of synthesis will not have a direct impact on selectivity and reaction.

[0071] The reaction solution used in the examples, after preheating and water separation, contained approximately 26.5% acetone, approximately 34.5% tetramethylpiperidone, approximately 30.5% water, and the remainder consisted of small amounts of light or heavy components.

[0072] Preparation of the reaction solution used in the examples: The molar ratio of acetone to ammonia was (4.5-6):1. The reaction was carried out at 60-65°C under the action of Lewis acid catalyst to obtain the tetramethylpiperidinone synthesis reaction solution.

[0073] Example 1

[0074] 400g of tetramethylpiperidinone synthesis reaction solution was placed in a reactor. A 25% alkali solution was added to adjust the pH to 11.5, and the temperature was raised to 60℃. 310.0g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidinone, and 30.5% water, with the remainder being small amounts of light or heavy components) was fed into the first centrifugal distillation column. The column operated at a pressure of 0.13MPa, and the centrifugal machine rotated at 1000rpm. The top temperature of the first centrifugal distillation column was controlled at 82℃ to obtain acetone-water azeotropic vapor, and the bottom temperature was controlled at 100℃ to obtain a heavy component rich in tetramethylpiperidinone. The heavy component containing tetramethylpiperidinone was transferred to an intermediate column to remove intermediates, and then distilled in the product column to obtain 58.8g of triacetone amine product. The acetone-water azeotrope vapor from the top of the first centrifugal distillation column was directly introduced into the reboiler of the second centrifugal distillation column as a heat source. The operating pressure of the second centrifugal distillation column was 0.06 MPa, and the centrifugal compressor speed was 1200 rpm. The top temperature of the second centrifugal distillation column was controlled at 60°C, yielding acetone vapor, which was condensed and collected as a product with a purity of 99.6%. The bottom temperature of the second centrifugal distillation column was controlled at 75°C, yielding wastewater containing 0.08% acetone, which was treated and discharged. The acetone with a water content of 0.18% was directly reused in the next batch of synthesis. The time from the reaction liquid entering the centrifugal distillation system to the production of all qualified acetone was 1.6 hours.

[0075] Example 2

[0076] 400g of the reaction solution was placed in a reactor, and the pH was adjusted to 12.0 with 25% liquid alkali. The temperature was then raised to 65℃. 310.5g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidone, and 30.5% water) was fed into the first centrifugal distillation column. The column operated at a pressure of 0.15MPa and the centrifugal machine rotated at 1200rpm. The top temperature of the first centrifugal distillation column was controlled at 80℃ to obtain acetone-water azeotrope vapor, and the bottom temperature was controlled at 105℃ to obtain a heavy component rich in tetramethylpiperidone. The heavy component containing tetramethylpiperidone was sent to the intermediate column to remove intermediates and then entered the product column for distillation to obtain 59.1g of triacetone amine product. The acetone-water azeotrope vapor from the top of the first high-gravity distillation column was directly introduced into the reboiler of the second high-gravity low-pressure distillation column as a heat source. The operating pressure of the second high-gravity distillation column was 0.06 MPa, and the speed of the high-gravity machine was 1500 rpm. The top temperature of the second high-gravity distillation column was controlled at 58℃, yielding acetone vapor, which was condensed and collected as a product with a purity of 99.5%. The bottom temperature of the second high-gravity distillation column was controlled at 72℃, yielding wastewater containing 0.09% acetone, which was treated and discharged. The acetone with a water content of 0.16% was directly reused in the next batch of synthesis. The time from the reaction liquid entering the high-gravity distillation system to the production of all qualified acetone was 1.9 hours.

[0077] Example 3

[0078] 400g of tetramethylpiperidinone synthesis reaction solution was placed in a reactor, and the pH was adjusted to 12.5 with 25% liquid alkali before heating to 68℃. 310.3g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidinone, and 30.5% water) was fed into a first centrifugal distillation column. The column operated at a pressure of 0.14MPa and a centrifugal speed of 1000rpm. The top temperature of the first centrifugal distillation column was controlled at 85℃ to obtain acetone-water azeotropic vapor, and the bottom temperature was controlled at 105℃ to obtain a heavy component rich in tetramethylpiperidinone. The heavy component containing tetramethylpiperidinone was transferred to an intermediate column to remove intermediates, and then distilled in the product column to obtain 58.6g of triacetone amine product. The acetone-water azeotrope vapor from the top of the first high-gravity distillation column was directly introduced into the reboiler of the second high-gravity low-pressure distillation column as a heat source. The operating pressure of the second high-gravity distillation column was 0.06 MPa, and the speed of the high-gravity machine was 1200 rpm. The top temperature of the second high-gravity distillation column was controlled at 60℃, yielding acetone vapor, which was condensed and collected as a product with a purity of 99.5%. The bottom temperature of the second high-gravity distillation column was controlled at 75℃, yielding wastewater containing 0.07% acetone, which was treated before discharge. The acetone with a water content of 0.20% was directly reused in the next batch of synthesis. The time from the reaction liquid entering the high-gravity distillation system to the production of all qualified acetone was 1.7 hours.

[0079] Example 4

[0080] 400g of tetramethylpiperidinone synthesis reaction solution was placed in a reactor, and the pH was adjusted to 11.2 by adding 25% liquid alkali. The temperature was then raised to 70℃. 310.3g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidinone, and 30.5% water) was fed into the first centrifugal distillation column. The operating pressure of the column was 0.14MPa, and the centrifugal speed was 1200rpm. The top temperature of the first centrifugal distillation column was controlled at 80℃ to obtain acetone-water azeotrope vapor, and the bottom temperature was controlled at 95℃ to obtain a heavy component rich in tetramethylpiperidinone. The heavy component containing tetramethylpiperidinone was transferred to the intermediate column to remove intermediates and then entered the product column for distillation to obtain 58.7g of triacetone amine product. The acetone-water azeotrope vapor from the top of the first high-gravity distillation column is directly introduced into the reboiler of the second high-gravity low-pressure distillation column as a heat source. The operating pressure of the second high-gravity distillation column is 0.06 MPa, and the speed of the high-gravity machine is 1400 rpm. The top temperature of the second high-gravity distillation column is controlled at 60℃ to obtain acetone vapor, which is condensed and collected as a product with a purity of 99.7%. The bottom temperature of the second high-gravity distillation column is controlled at 75℃ to obtain wastewater containing 0.06% acetone, which is treated and then discharged. The acetone has a water content of 0.12% and can be directly reused in the next batch of synthesis. The time from the reaction liquid entering the high-gravity distillation system to the production of all qualified acetone is 2.0 hours.

[0081] Example 5

[0082] 400g of tetramethylpiperidinone synthesis reaction solution was placed in a reactor, and the pH was adjusted to 11.8 with 25% liquid alkali before heating to 68℃. 310.8g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidinone, and 30.5% water) was fed into a first centrifugal distillation column. The column operated at a pressure of 0.15MPa and a centrifugal speed of 1000rpm. The top temperature of the first centrifugal distillation column was controlled at 83℃ to obtain acetone-water azeotropic vapor, and the bottom temperature was controlled at 100℃ to obtain a heavy component rich in tetramethylpiperidinone. The heavy component containing tetramethylpiperidinone was transferred to an intermediate column to remove intermediates, and then fed into the product column for distillation to obtain 57.9g of triacetone amine product. The acetone-water azeotrope vapor from the top of the first high-gravity distillation column was directly introduced into the reboiler of the second high-gravity low-pressure distillation column as a heat source. The operating pressure of the second high-gravity distillation column was 0.06 MPa, and the speed of the high-gravity machine was 1500 rpm. The top temperature of the second high-gravity distillation column was controlled at 60℃, yielding acetone vapor, which was condensed and collected as a product with a purity of 99.8%. The bottom temperature of the second high-gravity distillation column was controlled at 73℃, yielding wastewater containing 0.03% acetone, which was treated and discharged. The acetone with a water content of 0.11% was directly reused in the next batch of synthesis. The time from the reaction liquid entering the high-gravity distillation system to the production of all qualified acetone was 2.0 hours.

[0083] Comparative Example 1

[0084] 400g of tetramethylpiperidinone synthesis reaction solution was placed in a reactor, and the pH was adjusted to 11.8 with 25% liquid alkali before heating to 68℃. 310.9g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidinone, and 30.5% water) was fed into a first centrifugal distillation column. The column operated at a pressure of 0.17MPa and a centrifugal speed of 800rpm. The top temperature of the first centrifugal distillation column was controlled at 78℃ to obtain acetone-water azeotropic vapor, and the bottom temperature was controlled at 92℃ to obtain a heavy component rich in tetramethylpiperidinone. The heavy component containing tetramethylpiperidinone was transferred to an intermediate column to remove intermediates, and then fed into the product column for distillation to obtain 69.8g of triacetone amine product. The acetone-water azeotrope vapor from the top of the first high-gravity distillation column was directly introduced into the reboiler of the second high-gravity low-pressure distillation column as a heat source. The operating pressure of the second high-gravity distillation column was 0.06 MPa, and the speed of the high-gravity machine was 1500 rpm. The top temperature of the second high-gravity distillation column was controlled at 60°C, yielding acetone vapor, which was condensed and collected as a product with a purity of 97.6%. The bottom temperature of the second high-gravity distillation column was controlled at 73°C, yielding wastewater containing 0.12% acetone, which was treated before discharge. The acetone contained 2.06% water and could not be directly reused in the next batch of synthesis.

[0085] Comparative Example 2

[0086] 400g of the tetramethylpiperidone synthesis reaction solution was placed in a reactor, and the pH was adjusted to 11.8 with 25% liquid alkali before heating to 68℃. 310.9g of the preheated reaction solution (containing approximately 26.5% acetone, 34.5% tetramethylpiperidone, and 30.5% water) was fed into a conventional distillation column equivalent to a high-gravity distillation column for processing. By adjusting the reflux ratio, the acetone content was adjusted to approximately 5%, making it unsuitable for direct use in the next batch of synthesis. The time from the reaction solution entering the conventional distillation system to the distillation of acetone was 4.0 hours.

[0087] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for separating acetone from a tetramethylpiperidone reaction solution, comprising using a dual-tower continuous distillation system to separate acetone from the tetramethylpiperidone reaction solution, wherein the dual-tower continuous distillation system refers to processing the reaction solution sequentially through two distillation towers.

2. The method according to claim 1, characterized in that, The separation method includes the following steps: S1, add alkali to adjust the pH to alkaline, and preheat the reaction solution; S2, the preheated reaction liquid enters the first distillation column for distillation, and acetone-water azeotrope vapor is obtained at the top of the column, and a heavy component containing tetramethylpiperidinone is obtained at the bottom of the column; S3, the acetone-water azeotrope obtained in S2 is directly introduced into the second distillation column for distillation, and acetone vapor is recovered at the top of the column.

3. The method according to claim 2, characterized in that, S1 controls the pH to be 11–13; and / or, The preheating temperature in S1 is 60-70℃.

4. The method according to any one of claims 1-3, characterized in that, There is a pressure difference between the two distillation columns of the dual-tower continuous separation system. The first distillation column is a high-pressure distillation column, and the second distillation column is a low-pressure distillation column. Preferably, the pressure difference between the first distillation column and the second distillation column is 0.05-0.10 MPa, and more preferably 0.06-0.09 MPa.

5. The method according to claim 2, characterized in that, The first distillation column is a supergravity distillation column; preferably, the supergravity machine in the supergravity distillation column in S2 rotates at 1000-1200 rpm.

6. The method according to claim 2, characterized in that, The temperature at the top of the tower in S2 is controlled at 80-85℃; and / or the temperature at the bottom of the tower in S2 is controlled at 95-105℃. And / or, the pressure in S2 is 0.13 to 0.15 MPa.

7. The method according to claim 2, characterized in that, The second distillation column is a supergravity distillation column; preferably, the supergravity machine in the supergravity distillation column in S3 rotates at 1200-1500 rpm.

8. The method according to claim 2, characterized in that, The temperature at the top of the middle tower of S3 is controlled at 58-60℃; and / or the temperature at the bottom of the middle tower of S3 is controlled at 70-75℃. And / or, the pressure of S3 is 0.06 to 0.07 MPa.

9. A dual-tower continuous distillation system, characterized in that, The dual-tower continuous distillation system comprises: a centrifugal pump, a high-pressure distillation column, a reboiler, a centrifugal pump, and a low-pressure distillation column connected in sequence; preferably, the dual-tower distillation system is the dual-tower distillation system as described in any one of claims 1-8.

10. The dual-tower continuous distillation system according to claim 9, characterized in that, Both the high-pressure distillation column and the low-pressure distillation column are ultragravity distillation columns. The high-pressure distillation column is a first ultragravity distillation column, and the low-pressure distillation column is a second ultragravity distillation column.

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