A method for synthesizing 2,2,6,6-tetramethyl-4-piperidone

Abstract

The application discloses a synthesis method of 2,2,6,6-tetramethyl-4-piperidone, and belongs to the technical field of 2,2,6,6-tetramethyl-4-piperidone synthesis. The method adopts a synthesis system comprising a gas-liquid-solid three-phase reactor to prepare 2,2,6,6-tetramethyl-4-piperidone; the three-phase reactor is provided with a gas distributor at the bottom and is provided with a first material inlet and a second material inlet, the first material inlet is connected with the gas distributor, and the second material inlet is located below the gas distributor; a catalyst overflow outlet is arranged at the upper portion of the gas-liquid-solid three-phase reactor; raw material ammonia entering from the first material inlet is distributed through the gas distributor and reacts with raw material acetone entering from the second material inlet under the action of a catalyst, and the catalyst is discharged from the catalyst overflow outlet. The synthesis method has the technical advantages of simple and easy-to-control reaction process, low catalyst unit consumption, high ammonia conversion rate and selectivity, and low tail gas ammonia content.

Description

Technical Field

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

[0002] Acetone and ammonia react to produce piperidinone, with a theoretical molar ratio of 3:1. In actual production, acetone is usually used in excess to improve the conversion rate of ammonia. However, when acetone and ammonia react, ammonia is in the gas phase and acetone is in the liquid phase. The gas-liquid phase interface area is small, making it difficult for ammonia and acetone to react completely. As a result, the conversion rate of ammonia remains low. The unreacted ammonia enters the tail gas treatment system or ammonia recovery system through the tail gas venting pipeline, which is difficult to recover and consumes a lot of energy.

[0003] Furthermore, the batch reactors and fixed-bed reactors commonly used in the preparation of 2,2,6,6-tetramethyl-4-piperidinone have the following drawbacks: Batch reactors typically use homogeneous or heterogeneous catalysts for batch reactions. Due to the limitations imposed by reaction equilibrium, the single-pass conversion rate is low, and unreacted ammonia enters the tail gas. Simultaneously, the abrasion intensity between catalyst particles or between the catalyst and the stirring blades / reactor wall is significant in batch reactors, leading to substantial catalyst loss. Fixed-bed technology uses heterogeneous catalysts. Although it eliminates the alkaline washing step and simplifies the process, it still does not overcome the influence of reaction equilibrium limitations, resulting in low ammonia conversion and a large amount of ammonia entering the tail gas. Moreover, once the catalyst in a fixed-bed reactor deactivates, the entire catalyst assembly needs to be replaced; online catalyst replenishment and recovery are not possible, leading to significant catalyst loss.

[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 synthesizing 2,2,6,6-tetramethyl-4-piperidinone, in order to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] This invention provides a method for synthesizing 2,2,6,6-tetramethyl-4-piperidinone, using a synthetic system to prepare 2,2,6,6-tetramethyl-4-piperidinone;

[0008] The synthesis system includes a gas-liquid-solid three-phase reactor. The bottom of the gas-liquid-solid three-phase reactor is equipped with a gas distributor. The bottom of the gas-liquid-solid three-phase reactor is also equipped with a first material inlet for introducing raw material ammonia and a second material inlet for introducing raw material acetone and catalyst. The first material inlet is connected to the gas distributor, and the second material inlet is located below the gas distributor. The upper part of the gas-liquid-solid three-phase reactor is equipped with a catalyst overflow outlet.

[0009] The raw material ammonia, which enters from the first material inlet, is distributed by the gas distributor and then reacts with the raw material acetone, which enters the gas-liquid-solid three-phase reactor from the second material inlet, under the catalytic action of the catalyst. The catalyst moves upward under the action of the gas flow and overflows from the catalyst overflow port.

[0010] 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 5 h⁻¹. -1 ~200h -1 The molar ratio of acetone to ammonia is 1:1 to 9:1.

[0011] In an optional embodiment, the raw material acetone is preheated to 30°C to 56.5°C before entering the gas-liquid-solid three-phase reactor;

[0012] And / or, the raw material ammonia is vaporized before entering the gas-liquid-solid three-phase reactor.

[0013] In an optional embodiment, the reaction temperature between the raw material acetone and the raw material ammonia is 60°C to 150°C, and the reaction pressure is 0.01 MPa to 10 MPa.

[0014] In an optional embodiment, the catalyst includes at least one of a homogeneous catalyst and a heterogeneous catalyst;

[0015] The homogeneous catalyst includes at least one of ammonium nitrate and ammonium chloride; the heterogeneous catalyst includes at least one of sulfonic acid resin, solid acid and molecular sieve.

[0016] In an optional embodiment, the particle size of the heterogeneous catalyst is 0.01 mm to 2 mm.

[0017] In an optional embodiment, the gas-liquid-solid three-phase reactor also has at least one of the following features:

[0018] Feature 1: A distribution plate is provided above the gas distributor;

[0019] Feature 2: A demister is installed at the top of the gas-liquid-solid three-phase reactor.

[0020] In an optional embodiment, the synthesis system further includes a catalyst recovery tower having a catalyst inlet;

[0021] The catalyst overflow port is connected to the catalyst inlet of the catalyst recovery tower.

[0022] In an optional embodiment, the catalyst overflow port includes a first catalyst overflow port and a second catalyst overflow port, and the catalyst inlet includes a first catalyst inlet and a second catalyst inlet. The first catalyst overflow port is connected to the first catalyst inlet, and the second catalyst overflow port is connected to the second catalyst inlet.

[0023] In an optional embodiment, a heat exchanger is also provided in the catalyst recovery tower to remove the heat of reaction.

[0024] In an optional embodiment, the temperature of the reaction liquid inside the catalyst recovery tower is 50°C to 120°C.

[0025] In an optional embodiment, the synthesis system further includes a condenser and a compressor. The inlet of the condenser is connected to the top outlet of the gas-liquid-solid three-phase reactor for acetone recovery of ammonia gas carrying the reaction liquid in the condenser. The condenser also has a first outlet and a second outlet. The first outlet is connected to the inlet of the compressor, and the outlet of the compressor is connected to the first material inlet to return the non-condensable gas in the condenser to the gas-liquid-solid three-phase reactor after compression by the compressor. The second outlet of the condenser is connected to a catalyst recovery tower to return the condensate to the catalyst recovery tower.

[0026] In an optional implementation, the synthesis system further includes a circulation pump and a filter;

[0027] The inlet of the circulating pump is connected to the outlet of the catalyst recovery tower. The outlet of the circulating pump is divided into a first stream, a second stream, and a third stream. The first stream is used to return to the gas-liquid-solid three-phase reactor, the second stream is used to return to the catalyst recovery tower, and the third stream is used for filtration. The mother liquor obtained from filtration is returned to the catalyst recovery tower.

[0028] The beneficial effects of this invention include:

[0029] This invention synthesizes 2,2,6,6-tetramethyl-4-piperidinone from ammonia and acetone in a gas-liquid-solid three-phase reactor. During the synthesis, the catalyst is fluidized by bubbles in a rising turbulent flow system within the gas-liquid-solid three-phase reactor system, resulting in minimal catalyst particle wear compared to batch reactors and jet reactors. Furthermore, ammonia gas is uniformly distributed in the reaction liquid through a gas distributor within the gas-liquid-solid three-phase reactor. The ammonia gas moves upwards in the form of bubbles, significantly increasing the gas-liquid surface area. Simultaneously, the bubbles fluidizing the catalyst particles carry the catalyst particles upwards, ensuring uniform catalyst distribution within the reactor and continuous surface renewal, thus avoiding dead zones.

[0030] The synthesis of 2,2,6,6-tetramethyl-4-piperidinone using the above-mentioned gas-liquid-solid three-phase reactor not only has the advantages of low catalyst consumption, high ammonia conversion and selectivity, and low ammonia content in the tail gas, but also the corresponding synthesis method has a simple and easy-to-control reaction process and low cost. Attached Figure Description

[0031] 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.

[0032] Figure 1 A schematic diagram of the synthetic system for 2,2,6,6-tetramethyl-4-piperidinone provided by the present invention.

[0033] Icons: 001-Ammonia (raw material); 002-Acetone (raw material); 003-Catalyst; 004-Top discharge from reactor; 005-Side discharge from first reactor; 006-Side discharge from second reactor; 007-2,2,6,6-Tetramethyl-4-piperidinone; 008-Condensate; 009-Non-condensable gas; 010-Compressed ammonia; 011-Stream containing catalyst; 012-First stream containing catalyst; 013-Second stream containing catalyst; 014-Third stream containing catalyst; 015-Mother Liquid; 016-Waste catalyst; 101-Gas-liquid-solid three-phase reactor; 102-Catalyst recovery tower; 103-Condenser; 104-Compressor; 105-Filter; 106-Circulating pump; 107-Heat exchanger; 108-Gas distributor; 109-Distribution plate; 110-Demister; 111-First material inlet; 112-Second material inlet; 113-First catalyst overflow port; 114-Second catalyst overflow port; 115-First catalyst inlet; 116-Second catalyst inlet. Detailed Implementation

[0034] 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.

[0035] The method for synthesizing 2,2,6,6-tetramethyl-4-piperidinone provided by the invention will be described in detail below.

[0036] This invention proposes a method for synthesizing 2,2,6,6-tetramethyl-4-piperidinone, which uses a synthetic system to prepare 2,2,6,6-tetramethyl-4-piperidinone.

[0037] Please refer to Figure 1 The synthesis system includes a gas-liquid-solid three-phase reactor 101; the bottom of the gas-liquid-solid three-phase reactor 101 is equipped with a gas distributor 108, and the bottom of the gas-liquid-solid three-phase reactor 101 is also provided with a first material inlet 111 for introducing raw material ammonia 001 and a second material inlet 112 for introducing raw material acetone 002 and catalyst 003. The first material inlet 111 is connected to the gas distributor 108, and the second material inlet 112 is located below the gas distributor 108; the upper part of the gas-liquid-solid three-phase reactor 101 is provided with a catalyst overflow outlet.

[0038] The raw material ammonia 001 entering from the first material inlet 111 is distributed by the gas distributor 108 and then reacts with the raw material acetone 002 entering the gas-liquid-solid three-phase reactor 101 from the second material inlet 112 under the catalytic action of the catalyst 003. The catalyst 003 moves upward under the action of the airflow and overflows from the catalyst 003 overflow port.

[0039] The 2,2,6,6-tetramethyl-4-piperidinone 007 obtained from the reaction is discharged from the bottom of the gas-liquid-solid three-phase reactor 101.

[0040] In some embodiments, the raw material acetone 002 may be preheated to 30°C to 56.5°C (e.g., 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 56.5°C) before entering the gas-liquid-solid three-phase reactor 101. The raw material ammonia 001 may be vaporized before entering the gas-liquid-solid three-phase reactor 101.

[0041] The feed volume hourly space velocity (VHSV) of the raw material acetone 002 can be 0.1 h⁻¹. -1 ~2.5h -1 , such as 0.1h -1 0.5h -1 1h -1 1.5h -1 2h -1 Or 2.5h -1 etc., can also be 0.1h -1 ~2.5h -1 Any other value within the range.

[0042] The feed volume hourly space velocity (VHSV) for raw material ammonia 001 can be 5 h⁻¹. -1 ~200h -1 , such as 5h -1 10h -1 20h-1 40h -1 50h -1 80h -1 100h -1 120h -1 140h -1 150h -1 180h -1 or 200h -1 Wait, or it can be 5 hours. -1 ~200h -1 Any other value within the range.

[0043] The above-mentioned feed volume hourly space velocities are all relative to the reaction zone.

[0044] The molar ratio of raw material acetone 002 to raw material ammonia 001 can be from 1:1 to 9:1, such as 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, or other values ​​within the range of 1:1 to 9:1.

[0045] It should be noted that in existing technologies, acetone 002 is usually required in excess to improve the ammonia conversion rate. However, the synthesis system and method provided by this invention can achieve a high ammonia conversion rate even without an excess of acetone 002. That is, in this invention, acetone 002 can be used in excess or not.

[0046] In some embodiments, the reaction temperature of raw material acetone 002 and raw material ammonia 001 can be 60℃ to 150℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, or other values ​​within the range of 60℃ to 150℃.

[0047] The reaction pressure can be 0.01MPa to 10MPa, such as 0.01MPa, 0.05MPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa or 10MPa, or other values ​​within the range of 0.01MPa to 10MPa.

[0048] In this invention, catalyst 003 includes at least one of homogeneous catalyst and heterogeneous catalyst.

[0049] The homogeneous catalyst includes at least one of ammonium nitrate and ammonium chloride.

[0050] Heterogeneous catalysts include at least one of sulfonic acid resins, solid acids, and molecular sieves.

[0051] The particle size of the above heterogeneous catalyst can be 0.01 mm to 2 mm, such as 0.01 mm, 0.05 mm, 1 mm, 1.5 mm or 2 mm, or other values ​​within the range of 0.01 mm to 2 mm.

[0052] In some embodiments, the catalyst 003 enters the gas-liquid-solid three-phase reactor 101 in the form of a slurry. Exemplarily, in addition to the catalyst 003, the slurry may also contain separately provided acetone feedstock for periodic replenishment.

[0053] In some embodiments, a distribution plate 109 is provided above the gas distributor 108. The distribution plate 109 can have multiple layers. The distribution plate 109 can be, by example, a sieve plate, a valve tray, or other types of perforated plate.

[0054] In some embodiments, a demister 110 may also be provided at the top of the gas-liquid-solid three-phase reactor 101.

[0055] Continuing from the above, this invention employs a slurry-type gas-liquid-solid three-phase reactor 101. The catalyst 003 is fluidized by bubbles in the rising turbulent system within the system, resulting in minimal wear on the catalyst 003 particles compared to batch reactors and jet reactors. Secondly, ammonia gas is uniformly distributed in the reaction liquid through a gas distributor 108 within the gas-liquid-solid three-phase reactor 101. The ammonia gas moves upward in the form of bubbles, significantly increasing the gas-liquid surface area. Simultaneously, the bubbles fluidize the catalyst 003 particles, carrying them upward, ensuring uniform distribution of the catalyst 003 within the reactor and continuous surface renewal, avoiding dead zones. Thirdly, the gas-liquid-solid three-phase reactor 101 incorporates multiple layers of secondary distribution plates 109. This increases the gas phase residence time and, during the upward movement of the gas phase, continuously aggregates and breaks up under the action of the distribution plates 109, resulting in rapid renewal of the gas-liquid interface and promoting a complete reaction. In addition, the catalyst 003 particles in the slurry gas-liquid-solid reactor are in a dispersed fluidized state, and the ammonia gas continuously aggregates and breaks up in the form of bubbles, which together create a better heat transfer system. Through the heat absorption of acetone vaporization in the reactor and the heat transfer of heat by heat exchanger 107 in the catalyst recovery tower 102, the temperature of the reaction process can be effectively controlled, so as not to cause excessive by-products due to overheating.

[0056] Furthermore, the synthesis system provided by the present invention also includes a catalyst recovery tower 102 to recover the catalyst 003 used in the reaction, thereby greatly reducing the loss of catalyst 003.

[0057] The catalyst recovery tower 102 has a catalyst inlet; the catalyst overflow port of the gas-liquid-solid three-phase reactor 101 is connected to the catalyst inlet of the catalyst recovery tower 102.

[0058] In some embodiments, the catalyst overflow port includes a first catalyst overflow port 113 and a second catalyst overflow port 114, and the catalyst inlet includes a first catalyst inlet 115 and a second catalyst inlet 116. The first catalyst overflow port 113 is connected to the first catalyst inlet 115, and the second catalyst overflow port 114 is connected to the second catalyst inlet 116. The first catalyst overflow port 113 is located above the second catalyst overflow port 114, and the first catalyst inlet 115 is located above the second catalyst inlet 116.

[0059] The height settings of the first catalyst overflow port 113 and the second catalyst overflow port 114 are different. For example, the first catalyst overflow port 113 is set at the top of the tower, which serves as the main catalyst circulation pipeline. The second catalyst overflow port 114 is set in the middle of the tower, mainly used to establish catalyst circulation during start-up (if only the first catalyst overflow port is used, the amount of catalyst fed will be too large). Secondly, it is used to adjust the residence time of the reaction liquid and adjust the production capacity of the unit.

[0060] In some preferred embodiments, a heat exchanger 107 is also provided in the catalyst recovery tower 102 to remove the heat of reaction. Exemplarily, the temperature of the reaction liquid in the catalyst recovery tower 102 can be controlled between 50°C and 120°C, such as 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C, or other values ​​within the range of 50°C to 120°C. Since the reaction liquid circulation volume in the catalyst recovery tower 102 is large, this circulating liquid is used both to circulate the catalyst and to remove the heat of reaction. If the temperature is too high, it is easy to make it difficult to control the temperature of the reaction zone and increase by-products; if the temperature is too low, it is easy to reduce the catalyst activity and cause incomplete reaction. Therefore, this application controls the temperature of the reaction liquid in the catalyst recovery tower 102 to be between 50°C and 120°C.

[0061] Furthermore, the synthesis system provided by the present invention also includes a condenser 103 and a compressor 104, wherein the condenser 103 is mainly used to recover acetone, and the compressor 104 is mainly used to compress and recover ammonia.

[0062] Because the slurry-type gas-liquid-solid ammonia reaction is relatively complete, a small amount of unreacted ammonia, along with a small amount of reaction liquid (referred to as "reactor top discharge 004"), is discharged from the top of the reactor. The acetone in the condenser 103 is then separated out. The ammonia after the acetone separation is compressed by the compressor 104 and recycled back to the first material inlet 111 for further reaction. This not only effectively controls the amount of ammonia tail gas and avoids the complex subsequent ammonia recovery operations involved in conventional methods, but also helps to improve the conversion rate of ammonia and the yield of the product.

[0063] In some embodiments, the inlet of the condenser 103 is connected to the top outlet of the gas-liquid-solid three-phase reactor 101 for acetone recovery of ammonia gas carrying reaction liquid in the condenser 103. The condenser 103 also has a first outlet and a second outlet. The first outlet is connected to the inlet of the compressor 104, and the outlet of the compressor 104 is connected to the first material inlet 111 to return the non-condensable gas 009 in the condenser 103 to the gas-liquid-solid three-phase reactor 101 for recycling after compression by the compressor 104. The second outlet of the condenser 103 is connected to the catalyst recovery tower 102 to return the condensate 008 to the catalyst recovery tower 102.

[0064] Furthermore, the synthesis system provided by the present invention also includes a circulation pump 106 and a filter 105. The circulation pump 106 is mainly used to circulate the catalyst 003 slurry, and the filter 105 is mainly used to filter the spent catalyst 016.

[0065] In some embodiments, the inlet of the circulating pump 106 is connected to the outlet of the catalyst recovery tower 102. The outlet of the circulating pump 106 is divided into a first stream, a second stream, and a third stream. The first stream is a replenished fresh catalyst 003 stream (new catalyst added periodically), which is returned to the gas-liquid-solid three-phase reactor 101. The second stream is returned to the catalyst recovery tower 102 to impact the bottom of the tower and prevent excessive catalyst deposition and blockage. The third stream is deactivated catalyst. After being filtered by the filter 105, the mother liquor 015 is returned to the upper feed port of the catalyst recovery tower 102, and the filter cake is treated as waste catalyst 016 as appropriate.

[0066] Continuing on the above, the synthesis method provided by this invention can achieve an ammonia conversion rate of 95% or higher and an ammonia selectivity of 75% or higher (e.g., 75% to 80%). Furthermore, the energy consumption of catalyst 003 is reduced by at least 25% compared to commonly used batch reactors and fixed-bed reactors. This can significantly reduce the ammonia content in the tail gas system while improving the conversion rate, thereby reducing the difficulty of ammonia tail gas treatment.

[0067] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0068] Example 1

[0069] This invention provides a synthetic system for 2,2,6,6-tetramethyl-4-piperidinone. Please refer to [link / reference]. Figure 1 The synthesis system includes a gas-liquid-solid three-phase reactor 101, a catalyst recovery tower 102, a condenser 103, a compressor 104, a circulating pump 106, and a filter 105.

[0070] The gas-liquid-solid three-phase reactor 101 has a gas distributor 108 at its bottom, and also has a first material inlet 111 for introducing raw material ammonia 001 and a second material inlet 112 for introducing raw material acetone 002 and catalyst 003 at its bottom. The first material inlet 111 is connected to the gas distributor 108, and the second material inlet 112 is located below the gas distributor 108. A multi-layer distribution plate 109 (sieve plate) is provided above the gas distributor 108. The upper part of the gas-liquid-solid three-phase reactor 101 has a catalyst overflow outlet, and the top of the gas-liquid-solid three-phase reactor 101 is also provided with a demister 110.

[0071] The catalyst overflow outlets include a first catalyst overflow outlet 113 and a second catalyst overflow outlet 114. The catalyst recovery tower 102 has a first catalyst inlet 115 and a second catalyst inlet 116. The first catalyst overflow outlet 113 is connected to the first catalyst inlet 115, and the second catalyst overflow outlet 114 is connected to the second catalyst inlet 116. The first catalyst overflow outlet 113 is located above the second catalyst overflow outlet 114, and the first catalyst inlet 115 is located above the second catalyst inlet 116. A heat exchanger 107 is also provided inside the catalyst recovery tower 102.

[0072] The feed inlet of the condenser 103 is connected to the top outlet of the gas-liquid-solid three-phase reactor 101. The condenser 103 also has a first discharge port and a second discharge port. The first discharge port is connected to the feed inlet of the compressor 104, the discharge port of the compressor 104 is connected to the first material inlet 111, and the second discharge port of the condenser 103 is connected to the catalyst recovery tower 102.

[0073] The inlet of the circulating pump 106 is connected to the outlet of the catalyst recovery tower 102. The outlet of the circulating pump 106 is divided into a first stream 012 containing catalyst, a second stream 013 containing catalyst, and a third stream 014 containing catalyst. The first stream 012 containing catalyst is returned to the gas-liquid-solid three-phase reactor 101; the second stream 013 containing catalyst is returned to the catalyst recovery tower 102; and the third stream 014 containing catalyst enters the filter 105. The mother liquor 015 filtered by the filter 105 is returned to the upper feed port of the catalyst recovery tower 102.

[0074] Example 2

[0075] This embodiment provides a method for synthesizing 2,2,6,6-tetramethyl-4-piperidinone, combined with Figure 1 The method uses the synthesis system of 2,2,6,6-tetramethyl-4-piperidinone provided in Example 1 for synthesis.

[0076] Specifically, after the raw material ammonia 001 is vaporized, it enters the gas-liquid-solid three-phase reactor 101 through the first material inlet 111 from the gas distributor 108. The raw material acetone 002 is preheated to 45°C and fed into the gas-liquid-solid three-phase reactor 101 through the second material inlet 112 at the bottom of the gas-liquid-solid three-phase reactor 101 along with fresh catalyst 003 (sulfonic acid resin No. 1 catalyst with a particle size of 0.01mm to 2mm, brand name D001). The raw material ammonia 001 and raw material acetone 002 entering the gas-liquid-solid three-phase reactor 101 react under the catalytic action of catalyst 003 to generate 2,2,6,6-tetramethyl-4-piperidinone 007. The generated 2,2,6,6-tetramethyl-4-piperidinone 007 is discharged from the bottom of the gas-liquid-solid three-phase reactor 101.

[0077] The feed volume hourly space velocity (VHSV) of the raw material acetone 002 is 1.5 h⁻¹. -1 The feed volume hourly space velocity (VHSV) of the raw material ammonia 001 is 70 h⁻¹. -1 The molar ratio of acetone 002 to ammonia 001 is 1:1. The reaction temperature of acetone 002 and ammonia 001 is 75℃, and the reaction pressure is 0.2MPa.

[0078] During the reaction, a portion of the catalyst stream (referred to as "first reactor side stream discharge 005") exits from the first catalyst overflow port 113 of the reactor, and a portion of the catalyst stream (referred to as "second reactor side stream discharge 006") exits from the second catalyst overflow port 114 of the reactor. The two catalyst streams enter the catalyst recovery tower 102 through the first catalyst inlet 115 and the second catalyst inlet 116, respectively. The heat exchanger 107 is used to control the temperature of the reaction liquid in the catalyst recovery tower 102 at 55°C. After the reaction, ammonia gas carrying a small amount of reaction liquid exits from the top of the reactor. This reaction liquid stream is condensed by the condenser 103. The non-condensable gas 009 in the condenser 103 enters the compressor 104 through the inlet of the compressor 104 through the first outlet of the condenser 103. The compressed ammonia gas 010 obtained after compression is returned to the gas-liquid-solid three-phase reactor 101 for recycling. The condensate 008 in the condenser 103 enters the catalyst recovery tower 102 through the second outlet of the condenser 103.

[0079] The bottom stream after treatment by the catalyst recovery tower 102 is a catalyst-containing stream 011. The catalyst-containing first stream 012 is returned to the gas-liquid-solid three-phase reactor 101 via the circulation pump 106. The catalyst-containing second stream 013 is recycled back to the catalyst recovery tower 102. The catalyst-containing third stream 014 is filtered by the filter 105. The mother liquor 015 is returned to the upper feed port of the catalyst recovery tower 102. The filter cake is recovered as waste catalyst 016.

[0080] Example 3

[0081] The difference between this embodiment and Example 1 is that the catalyst is sulfonic acid resin 2# (brand name D061), the molar ratio of raw material acetone to raw material ammonia is 6:1, the reaction temperature of raw material acetone and raw material ammonia is 100℃, and the reaction pressure is 0.38MPa.

[0082] Example 4

[0083] The difference between this embodiment and Example 1 is that the catalyst is sulfonic acid resin 3# (brand name NKC-9), the molar ratio of raw material acetone to raw material ammonia is 9:1, the reaction temperature of raw material acetone and raw material ammonia is 120℃, and the reaction pressure is 0.6MPa.

[0084] Example 5

[0085] The difference between this embodiment and Example 1 is that the catalyst is ammonium nitrate, the molar ratio of acetone to ammonia is 1:1, the reaction temperature of acetone and ammonia is 150°C, and the reaction pressure is 1.2 MPa.

[0086] Comparative Example 1

[0087] This comparative example uses a reaction vessel to synthesize 2,2,6,6-tetramethyl-4-piperidinone. The catalyst used is ammonium nitrate. The molar ratio of acetone to ammonia is 6:1. The reaction temperature of acetone and ammonia is 65℃~75℃, as detailed in CN218710089U.

[0088] Comparative Example 2

[0089] This comparative example uses a reaction vessel to synthesize 2,2,6,6-tetramethyl-4-piperidinone. The catalyst used is sulfonic acid resin 1#. The molar ratio of acetone to ammonia is 6:1. The reaction temperature of acetone and ammonia is 65℃~75℃, as detailed in CN107033066B.

[0090] Test case

[0091] The ammonia conversion rate, product yield, and catalyst consumption of Examples 2-5 and Comparative Examples 1-2 were compared, and the results are shown in Table 1.

[0092] Table 1 Comparison Results

[0093] Ammonia conversion (%) Product yield (%) Catalyst specific consumption (%) Example 2 96.5 77.7 31.5 Example 3 96.8 80.9 35.7 Example 4 98.7 80.9 33.2 Example 5 99.1 78.8 25.9 Comparative Example 1 88.9 70.6 100 Comparative Example 2 90.5 65.0 100

[0094] Note: The catalyst consumption in the above embodiments is a relative value compared with Comparative Example 1 and Comparative Example 2.

[0095] As can be seen from Table 1, the synthesis method provided in the embodiments of the present invention can achieve a high ammonia conversion rate and product yield, and the catalyst consumption is low.

[0096] In summary, the synthesis method of 2,2,6,6-tetramethyl-4-piperidinone provided by the present invention has at least the following advantages: significantly reduced catalyst consumption, improved ammonia conversion rate and product yield, effectively reduced ammonia content in tail gas, simplified reaction process control, and simplified preparation system.

[0097] 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 synthesizing 2,2,6,6-tetramethyl-4-piperidinone, characterized in that, 2,2,6,6-Tetramethyl-4-piperidinone was prepared using a synthetic system; The synthesis system includes a gas-liquid-solid three-phase reactor; the bottom of the gas-liquid-solid three-phase reactor is equipped with a gas distributor, and the bottom of the gas-liquid-solid three-phase reactor is also provided with a first material inlet for introducing raw material ammonia and a second material inlet for introducing raw material acetone and catalyst. The first material inlet is connected to the gas distributor, and the second material inlet is located below the gas distributor; the upper part of the gas-liquid-solid three-phase reactor is provided with a catalyst overflow outlet. The raw material ammonia, which enters from the first material inlet, is distributed by the gas distributor and then reacts with the raw material acetone, which enters from the second material inlet into the gas-liquid-solid three-phase reactor, under the catalytic action of the catalyst. The catalyst moves upward under the action of the airflow and overflows from the catalyst overflow port.

2. The synthesis 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 5 h⁻¹. -1 ~200h -1 The molar ratio of the raw material acetone to the raw material ammonia is 1:1 to 9:

1.

3. The synthesis method according to claim 2, characterized in that, The raw material acetone is preheated to 30°C to 56.5°C before entering the gas-liquid-solid three-phase reactor; And / or, the raw material ammonia is vaporized before entering the gas-liquid-solid three-phase reactor.

4. The synthesis method according to any one of claims 1 to 3, characterized in that, The reaction temperature between the raw material acetone and the raw material ammonia is 60℃~150℃, and the reaction pressure is 0.01MPa~10MPa.

5. The synthesis method according to claim 4, characterized in that, The catalyst includes at least one of a homogeneous catalyst and a heterogeneous catalyst; The homogeneous catalyst includes at least one of ammonium nitrate and ammonium chloride; the heterogeneous catalyst includes at least one of sulfonic acid resin, solid acid and molecular sieve. Preferably, the particle size of the heterogeneous catalyst is 0.01 mm to 2 mm.

6. The synthesis method according to claim 4, characterized in that, The gas-liquid-solid three-phase reactor also has at least one of the following characteristics: Feature 1: A distribution plate is provided above the gas distributor; Feature 2: The top of the gas-liquid-solid three-phase reactor is equipped with a demister.

7. The synthesis method according to claim 5 or 6, characterized in that, The synthesis system also includes a catalyst recovery tower, which has a catalyst inlet; The catalyst overflow port is connected to the catalyst inlet of the catalyst recovery tower; Preferably, the catalyst overflow port includes a first catalyst overflow port and a second catalyst overflow port, and the catalyst inlet includes a first catalyst inlet and a second catalyst inlet, wherein the first catalyst overflow port is connected to the first catalyst inlet, and the second catalyst overflow port is connected to the second catalyst inlet.

8. The synthesis method according to claim 7, characterized in that, The catalyst recovery tower is also equipped with a heat exchanger to remove the heat of reaction. Preferably, the temperature of the reaction liquid in the catalyst recovery tower is 50℃~120℃.

9. The synthesis method according to claim 8, characterized in that, The synthesis system further includes a condenser and a compressor. The inlet of the condenser is connected to the top outlet of the gas-liquid-solid three-phase reactor for acetone recovery of ammonia gas carrying the reaction liquid in the condenser. The condenser also has a first outlet and a second outlet. The first outlet is connected to the inlet of the compressor, and the outlet of the compressor is connected to the first material inlet to return the non-condensable gas in the condenser to the gas-liquid-solid three-phase reactor after compression by the compressor. The second outlet of the condenser is connected to a catalyst recovery tower to return the condensate to the catalyst recovery tower.

10. The synthesis method according to claim 9, characterized in that, The synthesis system also includes a circulation pump and a filter; The inlet of the circulating pump is connected to the outlet of the catalyst recovery tower. The outlet of the circulating pump is divided into a first stream, a second stream, and a third stream. The first stream is used to return to the gas-liquid-solid three-phase reactor, the second stream is used to return to the catalyst recovery tower, and the third stream is used to be filtered by the filter. The mother liquor obtained from the filtration is returned to the catalyst recovery tower.

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