A process for the preparation of 2,2,6,6-tetramethyl-4-piperidone

Abstract

The application discloses a preparation method of 2,2,6,6-tetramethyl-4-piperidone and belongs to the technical field of 2,2,6,6-tetramethyl-4-piperidone preparation. The preparation method comprises the following steps: in a preparation system comprising a tower type multifunctional reactor, raw material acetone and raw material ammonia are reacted under the action of a catalyst; the raw material acetone and the raw material ammonia are respectively fed into a middle reaction zone of the tower type multifunctional reactor from upper and lower feed ports of the middle reaction zone and are reacted with the catalyst; light components and 2,2,6,6-tetramethyl-4-piperidone which are not completely reacted are subjected to rectification separation in an upper rectification section, and separated ammonia, water and acetone are discharged from a top of the reactor; and the reaction product is subjected to stripping separation in a lower stripping section to discharge 2,2,6,6-tetramethyl-4-piperidone crude products. The method can break the reaction balance limitation of the acetone amination and greatly reduce the back mixing of the system, and the conversion rate of ammonia and the selectivity of the reaction are improved.

Description

Technical Field

[0001] This invention relates to the field of 2,2,6,6-tetramethyl-4-piperidinone preparation technology, and more specifically, to a method for preparing 2,2,6,6-tetramethyl-4-piperidinone. Background Technology

[0002] Currently, the preparation of 2,2,6,6-tetramethyl-4-piperidinone mainly involves synthesizing crude 2,2,6,6-tetramethyl-4-piperidinone using ammonia and acetone under catalytic conditions via a batch reactor or fixed-bed reactor. The crude product is then processed through alkaline washing, a dehydration tower, a pre-impurity removal distillation tower, a product tower, and a post-impurity removal distillation tower to produce a qualified product.

[0003] Among them, batch reactors typically use homogeneous catalysts for intermittent reactions, and due to the limitation of reaction equilibrium, the single-pass conversion rate is low; fixed-bed reactor technology typically uses heterogeneous catalysts. Although the alkaline washing step is eliminated and the process is simplified, it is still difficult to break the limitation of reaction equilibrium, and the conversion rate is not very high. At the same time, due to the low heat transfer efficiency of fixed beds, there are more by-products.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 2,2,6,6-tetramethyl-4-piperidinone, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing 2,2,6,6-tetramethyl-4-piperidinone, wherein acetone and ammonia are reacted in the presence of a catalyst in a preparation system including a tower-type multifunctional reactor.

[0008] The tower-type multifunctional reactor includes a reactor tower top, an upper rectification section, a middle reaction zone, a lower stripping section, and a reactor tower bottom; the upper and lower parts of the middle reaction zone are respectively equipped with an upper feed inlet and a lower feed inlet;

[0009] Acetone and ammonia are fed into the middle reaction zone from the top and bottom inlets, respectively, and react under the action of a catalyst. Unreacted light components and 2,2,6,6-tetramethyl-4-piperidinone are separated by distillation in the upper rectification section. The separated ammonia, along with water and acetone, is discharged from the top of the reactor column. The product is separated by stripping in the lower stripping section. The crude 2,2,6,6-tetramethyl-4-piperidinone containing interstitial impurities is discharged from the bottom of the reactor column.

[0010] In an optional embodiment, the reaction temperature in the central reaction zone is 60°C to 150°C; the molar ratio of acetone to ammonia in the central reaction zone is 3.5:1 to 9:1.

[0011] In an optional embodiment, the feed volume hourly space velocity (VHSV) of the raw material acetone is 0.1 h⁻¹. -1 ~2.5h -1 The feed volume hourly space velocity (VHSV) for the ammonia feedstock is 0.1 h⁻¹. -1 ~150h -1 .

[0012] In an optional embodiment, the raw material acetone is preheated to 30°C to 56.5°C before entering the central reaction zone.

[0013] In an optional embodiment, the vaporized liquid ammonia is preheated to 30°C to 56.5°C before entering the central reaction zone.

[0014] In an optional embodiment, the theoretical plate number in the middle reaction zone is 40 to 44, the top temperature is 0°C to 70°C, the bottom temperature is 70°C to 150°C, and the reflux ratio is 1 to 5; the pressure is 0 MPa to 2 MPa (gauge pressure).

[0015] In an optional embodiment, the catalyst is a solid-phase catalyst.

[0016] In an optional embodiment, the catalyst includes at least one of sulfonic acid resin, solid acid, and molecular sieve.

[0017] In an optional embodiment, the particle size of the catalyst is 0.01 mm to 5 mm.

[0018] In an optional implementation, a heat exchange system is provided in the central reaction zone to control the reaction temperature in the central reaction zone.

[0019] In an optional embodiment, the preparation system further includes a first condenser, a gas-liquid separator, and an acetone distillation column;

[0020] The discharge port at the top of the reactor column is connected to the inlet of the first condenser. The first condenser has a first discharge port and a second discharge port. The first discharge port is connected to the inlet of the gas-liquid separator. The gas-liquid separator also includes a gas phase outlet and a liquid phase outlet. The liquid phase outlet flows back to the top of the reactor column and the acetone distillation column through a pump and pipeline, respectively. The gas phase outlet of the gas-liquid separator is connected to the second discharge port. The second discharge port is connected to the compressor and then to the lower inlet of the middle reaction zone.

[0021] In an optional embodiment, the acetone distillation column has a theoretical plate number of 20 to 45, a top temperature of 0°C to 70°C, a bottom temperature of 70°C to 100°C, and a reflux ratio of 1 to 3; the pressure is -0.08 MPa to 1 MPa using a gauge manometer.

[0022] In an optional embodiment, the preparation system further includes a pre-impurity removal distillation column, wherein the outlet of the reactor bottom is connected to the inlet of the pre-impurity removal distillation column;

[0023] The theoretical plate number of the pre-impurity removal distillation column is 30-48, the top temperature is 40℃-110℃, the bottom temperature is 100℃-130℃, and the reflux ratio is 1-30; the pressure is -0.08MPa to -0.1MPa using a gauge pressure gauge.

[0024] In an optional embodiment, the preparation system further includes a finished product distillation column, wherein the bottom outlet of the pre-impurity removal distillation column is connected to the inlet of the finished product distillation column;

[0025] The theoretical plate number of the product distillation column is 35 to 55, the top temperature is 70℃ to 120℃, the bottom temperature is 122℃ to 136℃, and the reflux ratio is 1 to 5; the pressure is -0.09MPa to -0.1MPa using a gauge pressure gauge.

[0026] The beneficial effects of this invention include:

[0027] This invention employs a tower-type multifunctional reactor for the amination of acetone. This reactor includes a reactor top, an upper rectification section, a middle reaction zone, a lower stripping section, and a reactor bottom. It enables multi-stage reaction and rectification coupling. The middle reaction zone can carry out multi-stage reaction and rectification. Water generated during the reaction is carried away from the reaction system by ammonia gas, which helps to break the reaction equilibrium limitation of acetone amination. Through multi-stage reaction and rectification, backmixing and residence time of the reaction system are greatly reduced, which is beneficial to improving the conversion rate of ammonia and the selectivity of the reaction. The preparation system provided by this invention for the preparation of 2,2,6,6-tetramethyl-4-piperidinone has a shorter process flow, enables continuous reaction and rectification, has high conversion rate, low energy consumption, and stable product quality. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the preparation system for 2,2,6,6-tetramethyl-4-piperidinone provided by the present invention.

[0030] Icons: 01-Acetone (raw material); 02-Ammonia (raw material); 03-Recovered Ammonia; 04-Recovered Acetone; 05-Reactor Reflux; 001-Top of Reactor; 002-Upper Rectifying Section; 003-Middle Reaction Zone; 004-Lower Stripping Section; 005-Reactor Bottom; 101-Tower-type Multifunctional Reactor; 102-First Condenser; 103-Gas-Liquid Separator; 104-Compressor; 106-Heat Exchange System; 201-Acetone Distillation Column; 202-Second Condenser; 301-Pre-Impurity Removal Distillation Column; 302-Third Condenser; 401-Finish Product Distillation Column; 402-Fourth Condenser. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0032] The preparation method of 2,2,6,6-tetramethyl-4-piperidinone provided by the present invention will be described in detail below.

[0033] This invention proposes a method for preparing 2,2,6,6-tetramethyl-4-piperidinone, which is carried out in a preparation system including a tower-type multifunctional reactor 101 (such as...). Figure 1 In the process shown, acetone 01 and ammonia 02 are reacted under the action of a catalyst.

[0034] The tower-type multifunctional reactor 101 includes a reactor tower top 001, an upper rectification section 002, a middle reaction zone 003, a lower stripping section 004, and a reactor tower bottom 005; the upper and lower parts of the middle reaction zone 003 are respectively provided with an upper feed inlet and a lower feed inlet.

[0035] Raw materials acetone 01 and ammonia 02 enter the middle reaction zone 003 through the upper and lower feed inlets, respectively, and react under the action of the catalyst in the middle reaction zone 003. The unreacted light components such as raw materials ammonia 02 and acetone 01, as well as 2,2,6,6-tetramethyl-4-piperidinone, are separated by distillation in the upper rectification section 002. The separated raw materials ammonia 02, entrained with water and raw materials acetone 01, are discharged from the top of the reactor column 001. The product obtained from the reaction is separated by distillation in the lower stripping section 004. The crude product of 2,2,6,6-tetramethyl-4-piperidinone containing intermediate impurities is discharged from the bottom of the reactor column 005.

[0036] The tower-type multifunctional reactor 101 used in this invention can couple multi-stage reaction with distillation. The multi-stage reaction and distillation in the reaction zone separates the water generated in the reaction, breaking the reaction equilibrium limitation of acetone ammoniation. Furthermore, multi-stage distillation significantly reduces backmixing of the system, which is beneficial for improving the conversion rate of the raw material ammonia O2 and the selectivity of the reaction. The conversion rate of 2,2,6,6-tetramethyl-4-piperidinone can reach 99.5% or higher, and the selectivity can reach 75% or higher. For example, in some embodiments, the selectivity of 2,2,6,6-tetramethyl-4-piperidinone is approximately 75% to 80%.

[0037] It should be noted that, typically, after the reaction in one reactor is completed, the solvent is evaporated to complete one reaction separation process, which is called first-stage reaction separation. Three reactors connected in series constitute tertiary reaction separation. In a reactive distillation process, one theoretical plate is equivalent to one reaction and one separation. Therefore, the central reaction zone 003 of the tower-type multifunctional reactor 101 used in this application has multiple theoretical plates, which is equivalent to multiple reactors connected in series, i.e., multi-stage reaction separation.

[0038] The intermediate reaction zone 003 provided by the present invention is further provided with a heat exchange system 106 to control the reaction temperature of the intermediate reaction zone 003. The heat exchange system 106 includes a heat exchanger, such as a shell-and-tube heat exchanger, a plate heat exchanger, or a coiled tube heat exchanger, etc. Any related equipment that can realize the heat exchange function is within the protection scope of the present invention.

[0039] The temperature of the central reaction zone 003 can be effectively controlled by the heat transfer of the heat exchanger and the vaporization of acetone, so as to keep the reaction temperature stable and avoid the problems of low yield due to excessively low temperature and excessive by-products due to excessively high temperature.

[0040] In some embodiments, the reaction temperature of the central reaction zone 003 can be 60℃ to 150℃, such as 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃, or other values ​​within the range of 60℃ to 150℃.

[0041] The molar ratio of acetone 01 to ammonia 02 in the central reaction zone 003 can be from 3.5:1 to 9:1, such as 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1 or 9:1, or other values ​​within the range of 3.5:1 to 9:1.

[0042] In some embodiments, the feed volume hourly space velocity (VHSV) of the raw material acetone 01 can be 0.1 h⁻¹. -1 ~2.5h-1 , such as 0.1h -1 0.5h -1 0.8h -1 1h -1 1.2h -1 1.5h -1 1.8h -1 2h -1 2.2h -1 Or 2.5h -1 etc., can also be 0.1h -1 ~2.5h -1 Other values ​​within the range.

[0043] The feed volumetric space velocity (VHSV) for the raw material ammonia O2 can be 0.1 h⁻¹. -1 ~150h -1 , such as 0.1h -1 1h -1 5h -1 10h -1 20h -1 50h -1 80h -1 100h -1 120h -1 Or 150h -1 etc., can also be 0.1h -1 ~150h -1 Other values ​​within the range.

[0044] The above-mentioned feed volume hourly space velocities are all relative to the reaction zone.

[0045] In some preferred embodiments, acetone 01 is preheated to 30°C–56.5°C (e.g., 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 56.5°C) before entering the intermediate reaction zone 003. Correspondingly, ammonia 02 is first vaporized, then preheated to 30°C–56.5°C (e.g., 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 56.5°C) before entering the intermediate reaction zone 003.

[0046] In some embodiments, the theoretical plate number of the central reaction zone 003 can be 40 to 44, such as 40, 41, 42, 43 or 44, or other values ​​within the range of 40 to 44.

[0047] The top temperature of the middle reaction zone 003 can be between 0℃ and 70℃, such as 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, or 70℃, or other values ​​within the range of 0℃ to 70℃. In some of the listed embodiments, the top temperature of the middle reaction zone 003 can be between 54℃ and 58℃, such as 54℃, 55℃, 56℃, 57℃, or 58℃.

[0048] The reboiler temperature in the central reaction zone 003 can be between 70℃ and 150℃, such as 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, or 150℃, or other values ​​within the range of 70℃ to 150℃. In some of the listed embodiments, the reboiler temperature in the central reaction zone 003 can be between 94℃ and 98℃, such as 94℃, 95℃, 96℃, 97℃, or 98℃.

[0049] The reflux ratio of the central reaction zone 003 can be 1 to 5, such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5, or other values ​​within the range of 1 to 5. In some of the listed embodiments, the reflux ratio of the central reaction zone 003 can be 1.6 to 2, such as 1.6, 1.7, 1.8, 1.9, or 2.

[0050] Using a gauge manometer, the pressure in the middle reaction zone 003 can be 0MPa to 2MPa, such as 0MPa, 0.5MPa, 1MPa, 1.5MPa or 2MPa, or other values ​​within the range of 0MPa to 2MPa.

[0051] The catalyst used in the above reaction is a solid-phase catalyst, which may include at least one of sulfonic acid resin, solid acid and molecular sieve.

[0052] In some embodiments, the particle size of the catalyst can be 0.01 mm to 5 mm, such as 0.01 mm, 0.05 mm, 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm, or other values ​​within the range of 0.01 mm to 5 mm.

[0053] Furthermore, the preparation system provided by the present invention also includes a first condenser 102, a gas-liquid separator 103, and an acetone distillation column 201.

[0054] The discharge port of the reactor top 001 is connected to the inlet of the first condenser 102. The first condenser 102 has a first discharge port and a second discharge port. The first discharge port of the first condenser 102 is connected to the inlet of the gas-liquid separator 103. The second discharge port of the first condenser 102 is connected to the compressor 104 and then to the lower inlet of the middle reaction zone 003. The gas-liquid separator 103 also includes a gas phase outlet and a liquid phase outlet. The liquid phase outlet flows back to the upper rectification section 002 of the reactor and the acetone rectification column 201 of the reactor via a discharge pump and pipeline, respectively. The gas phase outlet is connected to the second discharge port.

[0055] The unreacted raw materials, such as ammonia 02 and acetone 01, are separated from 2,2,6,6-tetramethyl-4-piperidinone by distillation in the upper rectification section 002. The unreacted raw materials, including ammonia 02, water, and acetone 01, are discharged from the top of the reactor column 001 and further condensed in the first condenser 102. Some of the acetone containing water is returned to the upper rectification section 002 of the reactor, and some of the acetone containing water is fed into the acetone rectification column 201 as recovered acetone 04 for acetone recovery. Specifically, the material condensed by the first condenser 102 is separated by a gas-liquid separator 103. Part of the separated liquid phase (as reactor reflux 05) is returned to the tower via a discharge pump and reflux pipeline, while the other part, containing water-containing acetone, is fed into the acetone distillation tower 201 as recovered acetone 04 for separation. The acetone obtained from the acetone distillation tower 201 is connected to the upper feed port of the middle reaction zone 003 of the reactor via the top outlet of the tower for recycling. Meanwhile, the recovered ammonia 03 from the first condenser 102 is compressed by the compressor 104 and mixed with new raw material ammonia 02 before entering the middle reaction zone 003 to complete the recycling of ammonia, which can effectively improve the utilization rate of raw material ammonia 02.

[0056] It should be noted that the first condenser 102 mentioned above can also be used as a preheater for raw materials, and can preheat the recovered ammonia and acetone.

[0057] The theoretical plate number of the acetone distillation column 201 is 20-45, the top temperature is 0℃-70℃, the bottom temperature is 70℃-100℃, and the reflux ratio is 1-3; the pressure is -0.08MPa-1MPa measured by gauge pressure.

[0058] The theoretical number of plates in the acetone distillation column 201 described above can be 20 to 45, such as 20, 25, 30, 35, 40, or 45, or other values ​​within the range of 20 to 45. In some of the listed embodiments, the theoretical number of plates in the acetone distillation column 201 can be 20 to 22, such as 20, 21, or 22.

[0059] The top temperature of the acetone distillation column 201 can be from 0℃ to 70℃, such as 0℃, 5℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, or 70℃, or other values ​​within the range of 0℃ to 70℃. In some of the listed embodiments, the top temperature of the acetone distillation column 201 can be from 63℃ to 67℃, such as 63℃, 64℃, 65℃, 66℃, or 67℃.

[0060] The reboiler temperature of the acetone distillation column 201 can be between 70°C and 100°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C, or other values ​​within the range of 70°C to 100°C. In some of the listed embodiments, the reboiler temperature of the acetone distillation column 201 can be between 78°C and 82°C, such as 78°C, 79°C, 80°C, 81°C, or 82°C.

[0061] The reflux ratio of the acetone distillation column 201 can be 1 to 3, such as 1, 1.5, 2, 2.5 or 3, or other values ​​within the range of 1 to 3. In some of the listed embodiments, the reflux ratio of the acetone distillation column 201 can be 1.4 to 1.8, such as 1.4, 1.5, 1.6, 1.7 or 1.8.

[0062] The pressure of the acetone distillation column 201 can be -0.08MPa to 1MPa, such as -0.08MPa, -0.05MPa, 0MPa, 0.5MPa, 0.8MPa or 1MPa, or other values ​​within the range of -0.08MPa to 1MPa.

[0063] The top outlet of the acetone distillation column 201 is connected to a second condenser 202. After the top stream of the acetone distillation column 201 is condensed by the second condenser 202, part of it is returned to the acetone distillation column 201, and the other part is the top product of the acetone distillation column 201.

[0064] The bottom outlet of the acetone distillation column 201 is connected to a reboiler. After passing through the reboiler, part of the bottom stream of the acetone distillation column 201 returns to the acetone distillation column 201, while the other part, mainly water, enters the wastewater treatment unit.

[0065] Furthermore, the preparation system also includes a pre-impurity removal distillation column 301, and the bottom outlet of the tower-type multifunctional reactor 101 is connected to the inlet of the pre-impurity removal distillation column 301 to remove impurities from the product.

[0066] The theoretical number of plates in the aforementioned pre-impurity removal distillation column 301 can be 30 to 48, such as 30, 32, 34, 36, 38, 40, 42, 44, 46, or 48, or other values ​​within the range of 30 to 48. In some of the listed embodiments, the theoretical number of plates in the pre-impurity removal distillation column 301 can be 32 to 34, such as 32, 33, or 34.

[0067] The top temperature of the pre-impurity removal distillation column 301 can be between 40℃ and 110℃, such as 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, or 110℃, or other values ​​within the range of 40℃ to 110℃. In some listed embodiments, the top temperature of the pre-impurity removal distillation column 301 can be between 70℃ and 74℃, such as 70℃, 71℃, 72℃, 73℃, or 74℃.

[0068] The reboiler temperature of the pre-impurity removal distillation column 301 can be between 100℃ and 130℃, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, or 130℃, or other values ​​within the range of 100℃ to 130℃. In some of the listed embodiments, the reboiler temperature of the pre-impurity removal distillation column 301 can be between 118℃ and 122℃, such as 118℃, 119℃, 120℃, 121℃, or 122℃.

[0069] The reflux ratio of the pre-impurity removal distillation column 301 can be 1 to 30, such as 1, 5, 10, 15, 20, 25 or 30, or other values ​​within the range of 1 to 30. In some of the listed embodiments, the reflux ratio of the pre-impurity removal distillation column 301 can be 4.4 to 4.6, such as 4.4, 4.5 or 4.6.

[0070] Using a gauge pressure gauge, the pressure of the pre-impurity removal distillation column 301 can be -0.08 MPa to -0.1 MPa, such as -0.08 MPa, -0.085 MPa, -0.09 MPa, -0.095 MPa, or -0.1 MPa, or other values ​​within the range of -0.08 MPa to -0.1 MPa. In some listed embodiments, the pressure of the pre-impurity removal distillation column 301 can be -0.096 MPa to -0.1 MPa, such as -0.096 MPa, -0.097 MPa, -0.098 MPa, -0.099 MPa, or -0.1 MPa.

[0071] The top outlet of the pre-impurity removal distillation column 301 is connected to a third condenser 302. After the top stream of the pre-impurity removal distillation column 301 is condensed by the third condenser 302, part of it is returned to the pre-impurity removal distillation column 301, and the other part is used as the top output of the pre-impurity removal distillation column 301.

[0072] The bottom outlet of the pre-impurity removal distillation column 301 is connected to a reboiler. After passing through the reboiler, part of the bottom stream of the pre-impurity removal distillation column 301 is returned to the pre-impurity removal distillation column 301, and the other part is used to feed into the product distillation column 401.

[0073] Furthermore, the preparation system may also include a finished product distillation column 401, with the bottom outlet of the pre-impurity removal distillation column 301 connected to the inlet of the finished product distillation column 401 to further improve the purity of the finished product.

[0074] The theoretical number of plates in the aforementioned product distillation column 401 can be 35 to 55, such as 35, 40, 45, 50, or 55, or other values ​​within the range of 35 to 55. In some of the listed embodiments, the theoretical number of plates in the product distillation column 401 can be 35 to 36, such as 35 or 36.

[0075] The top temperature of the product distillation column 401 can be between 70℃ and 120℃, such as 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, or 120℃, or any other value within the range of 70℃ to 120℃. In some of the listed embodiments, the top temperature of the product distillation column 401 can be between 104℃ and 106℃, such as 104℃, 105℃, or 106℃.

[0076] The reboiler temperature of the product distillation column 401 can be between 122℃ and 136℃, such as 122℃, 124℃, 126℃, 128℃, 130℃, 132℃, 134℃, or 136℃, or other values ​​within the range of 122℃ to 136℃. In some of the listed embodiments, the reboiler temperature of the product distillation column 401 can be between 134℃ and 136℃, such as 134℃, 135℃, or 136℃.

[0077] The reflux ratio of the product distillation column 401 can be 1 to 5, such as 1, 2, 3, 4 or 5, or other values ​​within the range of 1 to 5. In some of the listed embodiments, the reflux ratio of the product distillation column 401 can be 2 to 2.4, such as 2, 2.1, 2.2, 2.3 or 2.4.

[0078] Using a gauge pressure gauge, the pressure of the product distillation column 401 can be -0.09 MPa to -0.1 MPa, such as -0.09 MPa, -0.096 MPa, -0.097 MPa, -0.098 MPa, -0.099 MPa, or -0.1 MPa, or any other value within the range of -0.09 MPa to -0.1 MPa. In some of the listed embodiments, the pressure of the product distillation column 401 can be -0.096 MPa to -0.1 MPa, such as -0.096 MPa, -0.097 MPa, -0.098 MPa, -0.099 MPa, or -0.1 MPa.

[0079] The top outlet of the finished product distillation column 401 is connected to a fourth condenser 402. After the top stream of the finished product distillation column 401 is condensed by the fourth condenser 402, part of it is returned to the finished product distillation column 401, and the other part is the top product of the finished product distillation column 401.

[0080] The bottom outlet of the product distillation column 401 is connected to a reboiler. After passing through the reboiler, part of the bottom stream of the product distillation column 401 is returned to the product distillation column 401, and the other part is discharged as the bottom product of the product distillation column 401.

[0081] As described above, the preparation method of 2,2,6,6-tetramethyl-4-piperidinone provided by this invention has a short process flow, can achieve continuous reaction and distillation, has high conversion rate, low energy consumption, and stable product quality.

[0082] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0083] Example 1

[0084] This embodiment provides a preparation system for 2,2,6,6-tetramethyl-4-piperidinone, which includes a tower-type multifunctional reactor 101, a compressor 104, a condenser, a gas-liquid separator 103, an acetone distillation column 201, a pre-impurity removal distillation column 301, and a finished product distillation column 401.

[0085] The tower-type multifunctional reactor 101 includes a reactor top 001, an upper rectification section 002, a middle reaction zone 003, a lower stripping section 004, a reactor bottom 005, and a heat exchange system 106. The middle reaction zone 003 has an upper feed inlet for acetone 01 and a lower feed inlet for ammonia 02, respectively. The heat exchange system 106 is connected to the middle reaction zone 003 to regulate its temperature.

[0086] The discharge port of the reactor top 001 is connected to the inlet of the first condenser 102. The first condenser 102 has a first discharge port and a second discharge port. The first discharge port of the first condenser 102 is connected to the inlet of the gas-liquid separator 103. The gas-liquid separator 103 also includes a gas phase outlet and a liquid phase outlet. The liquid phase outlet flows back to the upper rectification section 002 of the reactor and the acetone rectification column 201 of the reactor via a pump and pipeline, respectively. The gas phase outlet is connected to the second discharge port. The second discharge port of the first condenser 102 is connected to the compressor 104 and then to the lower inlet of the middle reaction zone 003.

[0087] A reboiler is connected to the outlet of reactor column 005. One outlet of the reboiler is connected to reactor column 005, and the other outlet is connected to the inlet of pre-impurity distillation column 301 via a discharge pump.

[0088] The top outlet of the acetone distillation column 201 is connected to a second condenser 202. One outlet of the second condenser 202 is connected to the acetone distillation column 201, and the other outlet of the second condenser 202 is used for top discharge. The bottom outlet of the acetone distillation column 201 is connected to a reboiler. One outlet of the reboiler is connected to the acetone distillation column 201, and the other outlet of the reboiler discharges the water generated in the reaction system through a discharge pump.

[0089] The top outlet of the pre-impurity removal distillation column 301 is connected to a third condenser 302. One outlet of the third condenser 302 is connected to the pre-impurity removal distillation column 301, and the other outlet of the third condenser 302 is used for top product discharge. The bottom outlet of the pre-impurity removal distillation column 301 is connected to a reboiler. One outlet of the reboiler is connected to the pre-impurity removal distillation column 301, and the other outlet of the reboiler is connected to the inlet of the finished product distillation column 401 via a discharge pump.

[0090] The top outlet of the product distillation column 401 is connected to a fourth condenser 402. One outlet of the fourth condenser 402 is connected to the product distillation column 401, and the other outlet of the fourth condenser 402 is used for top discharge. The bottom outlet of the product distillation column 401 is connected to a reboiler. One outlet of the reboiler is connected to the product distillation column 401, and the other outlet of the reboiler is used for bottom discharge via a discharge pump.

[0091] Example 2

[0092] This embodiment provides a method for preparing 2,2,6,6-tetramethyl-4-piperidinone. The preparation system for 2,2,6,6-tetramethyl-4-piperidinone is carried out using the preparation system provided in Example 1. The method includes:

[0093] Sulfonic acid resin catalyst #1 (brand name D001) with an average particle size of 1 mm was placed in the central reaction zone 003. The feed volume hourly space velocity (WHSV) of acetone 01 in the central reaction zone 003 was 0.1 h⁻¹. -1 (Relative to the reaction zone), the feed volume hourly space velocity (VHSV) for ammonia O2 gas is 0.1 h⁻¹. -1 The reaction zone temperature is 65℃; acetone 01 is preheated to 30℃ and fed into the upper feed port of the middle reaction zone 003; after gasification, the raw material is preheated to 45℃ and fed into the lower feed port of the middle reaction zone 003. The molar ratio of raw material acetone 01 to raw material ammonia 02 is 3.5:1; the temperature of the middle reaction zone 003 is controlled at 65℃ by a heat exchanger. Under the action of a catalyst, raw material acetone 01 and raw material ammonia 02 undergo a multi-stage reaction to synthesize 2,2,6,6-tetramethyl-4-piperidinone.

[0094] Unreacted raw materials, such as ammonia 02 and acetone 01, are separated from 2,2,6,6-tetramethyl-4-piperidinone by distillation in the upper rectification section 002. The unreacted ammonia 02, carrying water and acetone 01, is discharged from the top of the reactor column 001 and further condensed in the first condenser 102. A portion of the acetone containing water is returned to the upper rectification section 002 of the tower-type multifunctional reactor 101, while a portion of the acetone containing water is used as recovered acetone 04 and enters the acetone rectification column 201 for acetone recovery. This recovered acetone is then mixed with fresh acetone 01 and enters the middle reaction zone 003, completing the recycling of acetone. The unreacted ammonia 02 is compressed by compressor 104 and recovered, then mixed with fresh ammonia 02 and enters the middle reaction zone 003, completing the recycling of ammonia. The product obtained from the reaction was processed by the pre-impurity removal distillation column 301 and the product distillation column 401 to obtain the 2,2,6,6-tetramethyl-4-piperidinone product.

[0095] The theoretical plate number of the central reaction zone 003 is 42, the top temperature is 56℃, the bottom temperature is 96℃, the reflux ratio is 1.8, and the pressure is atmospheric pressure. The theoretical plate number of the acetone distillation column 201 is 21, the top temperature is 65℃, the bottom temperature is 80℃, the reflux ratio is 1.6, and the pressure is -0.09MPa. The theoretical plate number of the pre-impurity removal distillation column 301 is 33, the top temperature is 72℃, the bottom temperature is 120℃, the reflux ratio is 4.5, and the pressure is -0.098MPa. The theoretical plate number of the product distillation column 401 is 35, the top temperature is 105℃, the bottom temperature is 135℃, the reflux ratio is 2.2, and the pressure is -0.098MPa.

[0096] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this example was 77.06%, and the steam consumption was 4.2 t steam / t.

[0097] Example 3

[0098] This embodiment provides a method for preparing 2,2,6,6-tetramethyl-4-piperidinone. The preparation system for 2,2,6,6-tetramethyl-4-piperidinone is carried out using the preparation system provided in Example 1. The method includes:

[0099] Sulfonic acid resin catalyst #2 (brand name D061) with an average particle size of 3 mm was placed in the central reaction zone 003. The feed volume hourly space velocity (WHSV) of acetone 01 in the central reaction zone 003 was 1 h⁻¹. -1 (Relative to the reaction zone) The feed volume hourly space velocity (VHSV) of the raw material ammonia O2 is 20 h⁻¹. -1 The reaction zone temperature is 75℃; acetone 01 is preheated to 30℃ and fed into the upper feed port of the middle reaction zone 003; ammonia 02 is vaporized, preheated to 45℃, and fed into the lower feed port of the middle reaction zone 003. The molar ratio of acetone 01 to ammonia 02 is 5:1. The temperature of the middle reaction zone 003 is controlled at 75℃ by a heat exchanger. Under the action of a catalyst, acetone 01 and ammonia 02 undergo a multi-stage reaction to synthesize 2,2,6,6-tetramethyl-4-piperidinone.

[0100] Unreacted raw materials, such as ammonia 02 and acetone 01, are separated from 2,2,6,6-tetramethyl-4-piperidinone by distillation in the upper rectification section 002. The unreacted ammonia 02, carrying water and acetone 01, is discharged from the top of the reactor column 001 and further condensed in the first condenser 102. A portion of the acetone containing water is returned to the upper rectification section 002 of the tower-type multifunctional reactor 101, while a portion of the acetone containing water is used as recovered acetone 04 and enters the acetone rectification column 201 for acetone recovery. This recovered acetone is then mixed with fresh acetone 01 and enters the middle reaction zone 003, completing the recycling of acetone. The unreacted ammonia 02 is compressed by compressor 104 and recovered, then mixed with fresh ammonia 02 and enters the middle reaction zone 003, completing the recycling of ammonia. After processing the product obtained from the reaction in distillation column 301 (foreign impurity removal column) and product distillation column 401, 2,2,6,6-tetramethyl-4-piperidinone product is obtained.

[0101] The remaining conditions are the same as in Example 2.

[0102] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this example was 80.89%, and the steam consumption was 4.3 t steam / t.

[0103] Example 4

[0104] This embodiment provides a method for preparing 2,2,6,6-tetramethyl-4-piperidinone. The preparation system for 2,2,6,6-tetramethyl-4-piperidinone is carried out using the preparation system provided in Example 1. The method includes:

[0105] Sulfonic acid resin catalyst #3 (brand name NKC-9) with an average particle size of 5 mm was placed in the central reaction zone 003. The feed volume hourly space velocity (WHSV) of acetone 01 in the central reaction zone 003 was 2.5 h⁻¹. -1 (Relative to the reaction zone) The feed volume hourly space velocity (VHSV) of the raw material ammonia O2 is 120 h⁻¹. -1 The reaction zone temperature is 90℃; acetone 01 is preheated to 30℃ and fed into the upper feed port of the middle reaction zone 003; ammonia 02 is vaporized, preheated to 45℃, and fed into the lower feed port of the middle reaction zone 003. The molar ratio of acetone 01 to ammonia 02 is 9:1. The temperature of the middle reaction zone 003 is controlled at 90℃ by a heat exchanger. Under the action of a catalyst, acetone 01 and ammonia 02 undergo a multi-stage reaction to synthesize 2,2,6,6-tetramethyl-4-piperidinone.

[0106] Unreacted raw materials, such as ammonia 02 and acetone 01, are separated from 2,2,6,6-tetramethyl-4-piperidinone by distillation in the upper rectification section 002. The unreacted ammonia 02, carrying water and acetone 01, is discharged from the top of the reactor column 001 and further condensed in the first condenser 102. A portion of the acetone containing water is returned to the upper rectification section 002 of the tower-type multifunctional reactor 101, while a portion of the acetone containing water is used as recovered acetone 04 and enters the acetone rectification column 201 for acetone recovery. This recovered acetone is then mixed with fresh acetone 01 and enters the middle reaction zone 003, completing the recycling of acetone. The unreacted ammonia 02 is compressed by compressor 104 and recovered, then mixed with fresh ammonia 02 and enters the middle reaction zone 003, completing the recycling of ammonia. After processing the product obtained from the reaction in distillation column 301 (foreign impurity removal column) and product distillation column 401, 2,2,6,6-tetramethyl-4-piperidinone product is obtained.

[0107] The remaining conditions are the same as in Example 2.

[0108] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this example was 80.75%, and the steam consumption was 4.5 t steam / t.

[0109] Example 5

[0110] The difference between this embodiment and Example 1 is that the catalyst is a solid acid catalyst, specifically the heteropolyacid H4SiW. 12 O 40 .

[0111] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this example was 79.77%, and the steam consumption was 4.3 t steam / t.

[0112] Example 6

[0113] The difference between this embodiment and Example 1 is that the catalyst is a molecular sieve catalyst, specifically SM-5 molecular sieve.

[0114] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this example was 80.77%, and the steam consumption was 4.4 t steam / t.

[0115] Comparative Example 1

[0116] This comparative example uses a batch reactor to prepare 2,2,6,6-tetramethyl-4-piperidinone. The preparation method includes: adding ammonium chloride catalyst and acetone to the reactor; vaporizing liquid ammonia and preheating it to 45°C; feeding the mixture into the lower part of the reaction zone of the batch reactor; the molar ratio of acetone to ammonia is 3.5:1; controlling the reaction temperature at 65°C to 75°C; reacting acetone and ammonia under the action of a catalyst; and quenching, dehydrating, removing pre-impurities, and removing post-impurities to obtain the final piperidinone product.

[0117] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this comparative example was 70.60%, with a steam consumption of 6.5 t steam / t.

[0118] Comparative Example 2

[0119] This comparative example uses a fixed-bed reactor to prepare 2,2,6,6-tetramethyl-4-piperidinone. The preparation method includes: placing a solid acid catalyst in a fixed-bed reactor, with an acetone feed volume hourly space velocity of 1 h⁻¹. -1 (Relative to the reaction zone), the ammonia feed volume hourly space velocity is 0.5 h⁻¹. -1 The reaction zone temperature is 65℃~75℃. Acetone is preheated to 30℃~45℃, and liquid ammonia, after vaporization, is preheated to 30℃~45℃. Acetone and ammonia are mixed and fed into the lower part of the reaction zone. The molar ratio of acetone to ammonia is 3.5:1. The reaction zone temperature is controlled at 60℃~75℃ via a heat exchanger. Acetone and ammonia react under the action of a catalyst. The crude piperidinone obtained from the reaction is dehydrated, and then purified to obtain the final piperidinone product.

[0120] The yield of 2,2,6,6-tetramethyl-4-piperidinone obtained in this comparative example was 70.98%, with a steam consumption of 5.8 t steam / t.

[0121] In summary, the method for preparing 2,2,6,6-tetramethyl-4-piperidinone provided by this invention has at least the following advantages:

[0122] 1) By using the tower-type multifunctional reactor 101, multi-stage reaction and distillation were coupled. Multi-stage reaction and distillation in the middle reaction zone 003 separated the product water, broke the reaction equilibrium limitation of acetone amination and greatly reduced backmixing, and improved the conversion rate of ammonia and the selectivity of the reaction.

[0123] 2) The heat of reaction is effectively recovered, and the heat of reaction is used to preheat the raw materials, thus achieving full recovery and utilization;

[0124] 3) Stable temperature control: The reaction temperature in the central reaction zone 003 is effectively controlled by the heat transfer of the heat exchanger and the vaporization of acetone, so as not to exceed the temperature and cause excessive by-products.

[0125] 4) The unreacted raw material ammonia O2 is recovered and reused after separating it from the raw material acetone O1, which effectively improves the utilization rate of raw material ammonia O2;

[0126] 5) Ammonia in the crude 2,2,6,6-tetramethyl-4-piperidinone product in reactor column 005 is effectively recovered without the need for a separate distillation column, which greatly reduces energy consumption and simplifies the process.

[0127] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing 2,2,6,6-tetramethyl-4-piperidinone, characterized in that, In a preparation system including a tower-type multifunctional reactor, acetone and ammonia are reacted under the action of a catalyst. The tower-type multifunctional reactor includes a reactor tower top, an upper rectification section, a middle reaction zone, a lower stripping section, and a reactor tower bottom; the upper and lower parts of the middle reaction zone are respectively provided with an upper feed inlet and a lower feed inlet; Acetone and ammonia are fed into the middle reaction zone from the upper and lower feed inlets, respectively, and react under the action of a catalyst. Unreacted light components and 2,2,6,6-tetramethyl-4-piperidinone are separated by distillation in the upper rectification section. The separated ammonia, entrained with water and acetone, is discharged from the top of the reactor column. The product obtained from the reaction is separated by stripping in the lower stripping section. The crude 2,2,6,6-tetramethyl-4-piperidinone containing intermediate impurities is discharged from the bottom of the reactor column.

2. The preparation method according to claim 1, characterized in that, The reaction temperature in the central reaction zone is 60℃ to 150℃; the molar ratio of the raw material acetone to the raw material ammonia in the central reaction zone is 3.5:1 to 9:

1.

3. The preparation method according to claim 1, characterized in that, The feed volume hourly space velocity (VHSV) of the raw material acetone is 0.1 h⁻¹. -1 ~2.5h -1 The feed volume hourly space velocity (VHSV) of the ammonia feedstock is 0.1 h⁻¹. -1 ~150h -1 ; Preferably, the raw material acetone is preheated to 30°C to 56.5°C before entering the central reaction zone; Preferably, the vaporized liquid ammonia is preheated to 30°C to 56.5°C before entering the central reaction zone.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The theoretical plate number of the central reaction zone is 40 to 44, the top temperature is 0°C to 70°C, the bottom temperature is 70°C to 150°C, and the reflux ratio is 1 to 5; the pressure is 0 MPa to 2 MPa using a gauge.

5. The preparation method according to any one of claims 1 to 3, characterized in that, The catalyst is a solid-phase catalyst; Preferably, the catalyst comprises at least one of sulfonic acid resin, solid acid, and molecular sieve; Preferably, the particle size of the catalyst is 0.01 mm to 5 mm.

6. The preparation method according to claim 1, characterized in that, The central reaction zone is equipped with a heat exchange system to control the reaction temperature in the central reaction zone.

7. The preparation method according to claim 1, characterized in that, The preparation system also includes a first condenser, a gas-liquid separator, and an acetone distillation column; The discharge port at the top of the reactor tower is connected to the inlet of the first condenser. The first condenser has a first discharge port and a second discharge port. The first discharge port is connected to the inlet of the gas-liquid separator. The gas-liquid separator also includes a gas phase outlet and a liquid phase outlet. The liquid phase outlet flows back to the top of the reactor tower and the acetone distillation tower via a pump and pipeline, respectively. The gas phase outlet of the gas-liquid separator is connected to the second discharge port. The second discharge port is connected to a compressor and then to the lower inlet of the middle reaction zone.

8. The preparation method according to claim 7, characterized in that, The acetone distillation column has a theoretical plate number of 20 to 45, a top temperature of 0°C to 70°C, a bottom temperature of 70°C to 100°C, and a reflux ratio of 1 to 3; the pressure, measured by gauge pressure, is -0.08 MPa to 1 MPa.

9. The preparation method according to claim 8, characterized in that, The preparation system also includes a pre-impurity removal distillation column, and the outlet of the reactor bottom is connected to the inlet of the pre-impurity removal distillation column; The theoretical plate number of the pre-impurity removal distillation column is 30-48, the top temperature is 40℃-110℃, the bottom temperature is 100℃-130℃, and the reflux ratio is 1-30; the pressure is -0.08MPa to -0.1MPa using a gauge pressure gauge.

10. The preparation method according to claim 9, characterized in that, The preparation system also includes a finished product distillation column, wherein the bottom outlet of the pre-impurity removal distillation column is connected to the inlet of the finished product distillation column; The theoretical plate number of the product distillation column is 35 to 55, the top temperature is 70℃ to 120℃, the bottom temperature is 122℃ to 136℃, and the reflux ratio is 1 to 5; the pressure is -0.09MPa to -0.1MPa using a gauge pressure gauge.

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