A reaction system for preparing ultraviolet absorber UV-612

Abstract

The utility model provides a kind of reaction system of preparation ultraviolet absorber UV-612, including high pressure reation kettle, reflux condenser, out of condenser, acidification kettle, centrifuge, continuous freeze dryer;Gas pipeline system and self-suction stirrer are arranged in high pressure reation kettle, high pressure reation kettle top connects reflux elbow pipe, reflux straight pipe, reflux straight pipe bottom connects water receiving tank, reflux straight pipe upper portion is provided with reflux condenser, out of condenser, out of condenser connects receiving tank, high pressure reation kettle top is also connected with CO2 gas tank, high pressure reation kettle bottom is connected with oil phase receiving tank and water phase receiving tank by pipeline;The second discharge outlet of the bottom of water phase receiving tank is connected with acidification kettle by pump, acidification kettle top connects hydrochloric acid high tank, acidification kettle bottom connects centrifuge, centrifuge bottom connects centrifuge mother liquor tank and continuous freeze dryer;The utility model system improves the reaction activity of carbon dioxide, shortens reaction time, improves reaction efficiency, and is applicable to industrial production.

Description

Technical Field

[0001] This utility model relates to the technical field of ultraviolet absorber reaction systems, specifically a reaction system for preparing ultraviolet absorber UV-612. Background Technology

[0002] 3,5-Di-tert-butyl-4-hydroxybenzoic acid, also known as UV-612, has the chemical formula C15H22O3 (CAS No.: 1421-49-4). It belongs to the hindered phenolic ultraviolet (UV) absorber class. It absorbs UV energy through its intramolecular hydroxyl and benzene ring structures, and through the reversible breaking and recombination of intramolecular hydrogen bonds, converts the absorbed UV energy into heat energy, thus protecting materials from photo-oxidative degradation. As a light stabilizer, it is used in plastics such as polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyoxymethylene (POM) to prevent UV-induced yellowing and embrittlement. When used in synergy with benzotriazole UV absorbers (such as the Tinuvin series) or hindered amine light stabilizers (HALS), it can improve weather resistance.

[0003] Currently, there are four main synthetic routes for 3,5-di-tert-butyl-4-hydroxybenzoic acid (UV-612): The first method is the nitration-reduction oxidation method of 3,5-di-tert-butylbenzoic acid. This involves nitrating 3,5-di-tert-butylbenzoic acid to obtain a nitro compound, then reducing the nitro group to a hydroxyl group via a reduction reaction, and finally oxidizing it to obtain 3,5-di-tert-butyl-4-hydroxybenzoic acid. The disadvantages are that it involves many reaction steps, a low overall yield, and demanding nitration and reduction reaction conditions, making the operation complex.

[0004] The second synthetic method is the bromination oxidation of 2,6-di-tert-butyl-4-methylphenol. This method uses 2,6-di-tert-butyl-4-methylphenol as a raw material, first undergoing bromination to obtain the brominated product, and then proceeding with oxidation to finally obtain 3,5-di-tert-butyl-4-hydroxybenzoic acid. The disadvantages are that it uses bromine as the brominating agent, which is highly toxic and poses certain hazards to the environment and operators, and the reaction may generate a large number of byproducts.

[0005] The third synthetic method uses 2-amino-3,5-di-tert-butyl-4-hydroxy-6-bromo-benzyl alcohol as a starting material. In this method, 2-amino-3,5-di-tert-butyl-4-hydroxy-6-bromo-benzyl alcohol is added to a reaction vessel, followed by the sequential addition of sodium sulfate solution, nitromethane solution, diethyl glutarate solution, and niobium pentachloride powder. The reaction is carried out at a specific temperature and stirring speed. Finally, after washing, recrystallization, and dehydration, 3,5-di-tert-butyl-4-hydroxybenzoic acid is obtained. The disadvantages are the numerous reaction steps, the involvement of various reagents and complex operating conditions, and the high requirements for equipment and operators.

[0006] The fourth synthetic method is the Kolber-Schmidt reaction, which uses 2,6-di-tert-butylphenol as a starting material. This involves reacting 2,6-di-tert-butylphenol with sodium hydroxide in methanol to produce the sodium salt of 2,6-di-tert-butylphenol. Then, carbon dioxide is introduced into an autoclave, and the reaction is carried out under specific temperature and pressure. Finally, acidification yields 3,5-di-tert-butyl-4-hydroxybenzoic acid.

[0007] Compared to the three methods mentioned above, the fourth method has relatively mild reaction conditions, is relatively simple to operate, and yields higher product yields and purity. However, it requires high-pressure reaction equipment, and the reactivity of carbon dioxide is low, resulting in a longer reaction time. Therefore, it is necessary to design a special reaction system for the fourth synthesis method, optimize the synthesis process, thereby improving the reactivity of carbon dioxide, shortening the reaction time, increasing reaction efficiency, and making it suitable for industrial production. Summary of the Invention

[0008] The purpose of this invention is to provide a reaction system for preparing ultraviolet absorber UV-612, so as to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, this utility model provides the following technical solution:

[0010] This invention provides a reaction system for preparing ultraviolet absorber UV-612, including a high-pressure reactor, a reflux condenser, an outlet condenser, an acidification reactor, a centrifuge, and a continuous freeze dryer.

[0011] The high-pressure reactor is equipped with a gas pipeline system and a self-priming agitator. A first jacket is installed outside the high-pressure reactor, and a first temperature control medium is installed inside the first jacket. The top of the high-pressure reactor is connected to a reflux bend, the upper end of which is connected to the middle of a reflux straight pipe. The bottom of the reflux straight pipe is connected to a water receiving tank. One end of the reflux condenser is installed at the upper part of the reflux straight pipe. The other end of the reflux condenser is connected to one end of a distillation condenser through a pipe. The other end of the distillation condenser is connected to the receiving tank. A CO2 gas tank is also connected to the top of the high-pressure reactor. A first sampling port and a first discharge port are installed at the bottom of the high-pressure reactor. The first discharge port is connected to an oil phase receiving tank and a water phase receiving tank through a pipe.

[0012] The bottom of the aqueous phase receiving tank is equipped with a second sampling port and a second discharge port. The second discharge port is connected to the acidification reactor via a pump. The acidification reactor is equipped with a stirrer and a second jacket. The second jacket is equipped with a second temperature control medium. The top of the acidification reactor is connected to a hydrochloric acid high-level tank, and the bottom of the acidification reactor is connected to a centrifuge. The bottom of the centrifuge is connected to a centrifugal mother liquor tank and a continuous freeze dryer.

[0013] Furthermore, the first sampling port and the second sampling port are connected to a high-performance liquid chromatography detector.

[0014] Furthermore, the gas pipeline system includes three circular inlet pipes located at the upper, middle, and lower positions within the high-pressure reactor. These circular inlet pipes are fixed to the inner wall of the high-pressure reactor (the connection between the circular pipes and the inner wall can be achieved through welding, bolting, snap-fitting, or other methods). Each circular inlet pipe is connected to an inlet pipe, which has an inlet valve and an inlet flow meter and is connected to a CO2 gas cylinder. Multiple inlet branch pipes, preferably 10-15, are evenly distributed on the circular inlet pipes and inlet branch pipes, and can be connected by welding. Multiple air holes with a diameter of 1-5 mm are evenly distributed on the circular inlet pipes and inlet branch pipes. The inlet pipes have inlet valves and inlet flow meters for monitoring and adjusting the inlet volume.

[0015] Furthermore, the self-priming stirrer includes a stirring shaft, a motor driving the stirring shaft, and a self-priming cylindrical hollow stirring paddle. The stirring paddle is evenly arranged at the upper, middle, and lower parts of the stirring shaft. The stirring paddle includes a positioning cylindrical tube fixedly sleeved outside the stirring shaft. The positioning cylindrical tube is placed between two limiting rings on the stirring shaft. An upper support plate and a lower support plate are provided on the top and bottom outer edges of the positioning cylindrical tube. Multiple stirring cylinders with a diameter of 1-10cm are evenly arranged between the outer edges of the upper support plate and the lower support plate. Multiple stirring blades are arranged outward on the stirring cylinders.

[0016] Furthermore, the stirring cylinder is provided with a first hollow pipe inside, and multiple microholes are uniformly arranged on the stirring column. Multiple second hollow pipes are uniformly arranged radially inside the upper support plate and the lower support plate. A third hollow pipe is provided inside the stirring shaft. The first hollow pipe and the second hollow pipe are connected to each other, and the second hollow pipe and the third hollow pipe are connected to each other. Adjacent first hollow pipes are connected through a fourth hollow pipe, which is placed inside the upper support plate and the lower support plate.

[0017] Furthermore, the stirring blades are arc-shaped.

[0018] The interconnected hollow pipes and multi-layered hollow cylindrical agitator significantly increase mixing efficiency. The hollow sections allow fluid to flow freely between different layers, reducing dead zones and ensuring more uniform mixing. The multi-layered hollow structure generates multiple vortices, further enhancing the mixing effect. The hollow design increases the fluid flow path, reduces mixing time, and improves mixing efficiency. This design is particularly suitable for reaction processes requiring rapid mixing. The cylindrical shape allows the agitator to evenly distribute the stirring force within the reactor, reducing wear on the reactor's inner walls.

[0019] The cylindrical stirring device is equipped with multiple arc-shaped (preferably semi-circular) stirring blades on the stirring cylinder around its perimeter. Each stirring cylinder has a circular micro-pore structure for air intake, with a diameter of 1-3 mm, for air intake during the stirring process.

[0020] During the mixing process, the stirring blades generate multiple vortices, allowing materials to fully exchange, mix, and stir at different levels, thus ensuring the uniformity of the mixture. The compact layout of the stirring blades makes them suitable for applications with limited space, while also guaranteeing high-efficiency mixing. The stirring blades effectively reduce the formation of air pockets, thereby improving the pumping capacity of the impeller and enhancing mass transfer.

[0021] Compared with the prior art, the beneficial effects of this utility model are:

[0022] This utility model relates to a reaction system for preparing ultraviolet absorber UV-612. (1) Significantly improves production efficiency and enables continuous operation: No need for frequent loading, unloading and cleaning, reducing downtime and enabling 24-hour continuous production. Higher throughput: More products can be processed per unit time, suitable for large-scale industrial production. (2) Reduces production costs and optimizes energy consumption: The continuous system reduces energy waste through heat recovery and process optimization (traditional drying has high energy consumption, accounting for more than 30% of the cost). Saves labor: High degree of automation reduces manual intervention and operating costs. High equipment utilization: The same equipment runs continuously, spreading fixed costs. (3) More stable product quality: The continuous process avoids batch-to-batch differences and ensures product uniformity. Precise control: Real-time monitoring and adjustment of parameters (temperature, pressure, etc.) reduces the risk of product overheating or uneven drying. (4) Flexibility and scalability, modular design: Production lines can be expanded or adjusted according to capacity requirements. Adaptable to multiple products: Different materials (such as biological agents, instant coffee, pet food, etc.) can be processed through parameter adjustment. (5) Reduces pollution risk, closed system: Reduces the probability of human-caused pollution. Simplified cleaning validation: Continuous systems reduce the need for cleaning between batches. (6) Environmental advantages and reduced waste: Precise control reduces scrap rate. Energy-saving design: Some continuous systems use heat pumps or waste heat recovery technology to reduce carbon emissions.

[0023] This utility model's gas pipeline system features multi-point gas inlet: gas inlet pipes are arranged at the top, middle, and bottom of the reactor, ensuring that gas enters the reactor evenly at different heights and positions, avoiding localized gas accumulation or uneven distribution. Uniform mixing: This layout promotes thorough mixing of gas and reactants, improving reaction efficiency and product quality. During the reaction, uniform gas distribution significantly increases the reaction rate. Temperature uniformity: By introducing gas at different locations, temperature unevenness caused by localized gas accumulation is reduced, resulting in a more uniform temperature distribution within the reactor, which is beneficial for the smooth progress of the reaction. Segmented control: The gas inlet pipes at the top, middle, and bottom can be controlled independently, flexibly adjusting the gas intake according to different stages and needs of the reaction process, optimizing operating conditions. Rapid response: In emergency situations, multiple gas inlet points allow for faster adjustment of gas flow, reducing pressure peaks within the reactor and improving system safety. Reduced dead zones: Introducing gas inlet pipes in the middle and lower parts of the reactor effectively reduces dead zones within the reactor, preventing gas accumulation in these areas.

[0024] This invention employs a self-priming mechanically stirred reactor, featuring a hollow shaft with small openings in the stirring paddle. The negative pressure created by the paddle throwing out liquid draws gas from the upper part of the liquid surface, where it is then dispersed by the stirring blades. The size of the gas-liquid phase contact area significantly affects the reaction rate. Conventional stirring equipment is designed and manufactured to improve the dispersion characteristics of freshly added gas, but the flow rate of this fresh gas is sometimes very limited, severely restricting the increase in reaction rate. The self-priming stirrer, however, has the significant characteristic of re-drawing gas from the liquid surface within the reactor and dispersing it in the liquid phase, which can greatly increase the gas content and the gas-liquid phase contact area, thereby achieving the goal of increasing the reaction rate. In the self-priming gas-liquid stirring paddle, bubbles escape from the paddle tip, forming spherical shapes, and move to the reactor wall. After being impacted by the baffle, they form two circulating flows, one upward and one downward. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a reaction system for preparing ultraviolet absorber UV-612 according to the present invention;

[0026] Figure 2 This is a schematic diagram of the high-pressure reactor of this utility model;

[0027] Figure 3 This is a cross-sectional structural diagram of the stirring paddle of this utility model;

[0028] Figure 4 This is a top view of the stirring paddle of this utility model.

[0029] Explanation of reference numerals in the attached figures

[0030] In the diagram: 1. High-pressure reactor; 2. Acidification reactor; 3. Receiving tank; 4. Water receiving tank; 5. Distillation condenser; 6. Reflux condenser; 7. CO2 gas tank; 8. Oil phase receiving tank; 9. Aqueous phase receiving tank; 10. Centrifugal mother liquor tank; 11. Centrifuge; 12. Continuous freeze dryer; 13. Hydrochloric acid high-level tank; 14. High-performance liquid chromatography detector; 101. First jacket; 102. Stirring shaft; 103. Inlet circular pipe; 104. Inlet branch pipe; 105. Lower support plate; 106. Stirring blades; 107. Upper support plate; 108. Stirring cylinder; 109. Pore; 110. Micropore; 111. Inlet pipe; 112. Third hollow pipe; 113. Second hollow pipe; 114. First hollow pipe; 115. Limiting ring. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example 1

[0032] A reaction system for preparing ultraviolet absorber UV-612, as follows: Figure 1-4 As shown, it includes a high-pressure reactor 1, a reflux condenser 6, an outlet condenser, an acidification reactor 2, a centrifuge 11, and a continuous freeze dryer 12;

[0033] The high-pressure reactor 1 is equipped with a gas pipeline system and a self-priming stirrer. A first jacket 101 is installed outside the high-pressure reactor 1, and a first temperature control medium is installed inside the first jacket 101. The top of the high-pressure reactor 1 is connected to a reflux bend, the upper end of which is connected to the middle of a reflux straight pipe. The bottom of the reflux straight pipe is connected to a water receiving tank 4. One end of a reflux condenser 6 is installed at the upper part of the reflux straight pipe. The other end of the reflux condenser 6 is connected to one end of a distillation condenser 5 through a pipe. The other end of the distillation condenser 5 is connected to a receiving tank 3. A CO2 gas tank 7 is also connected to the top of the high-pressure reactor 1. The bottom of the high-pressure reactor 1 is equipped with a first sampling port and a first discharge port. The discharge port is connected to an oil phase receiving tank 8 and a water phase receiving tank 9 through pipes. The first sampling port and the second sampling port are connected to a high-performance liquid chromatography detector 14.

[0034] The bottom of the aqueous phase receiving tank 9 is provided with a second sampling port and a second discharge port. The second discharge port is connected to the acidification vessel 2 via a pump. The acidification vessel 2 is equipped with a stirrer and a second jacket is provided outside the acidification vessel 2. The second jacket is equipped with a second temperature control medium. The top of the acidification vessel 2 is connected to the hydrochloric acid high-level tank 13, and the bottom of the acidification vessel 2 is connected to the centrifuge 11. The bottom of the centrifuge 11 is connected to the centrifugal mother liquor tank 10 and the continuous freeze dryer 12.

[0035] The gas pipeline system includes three circular inlet pipes 103 located at the upper, middle, and lower positions within the high-pressure reactor 1. Each circular inlet pipe 103 is fixed to the inner wall of the high-pressure reactor 1 (the connection between the circular pipe and the inner wall of the high-pressure reactor 1 can be achieved through welding, bolting, snap-fitting, or other methods). Each circular inlet pipe 103 is connected to an inlet pipe 111. The inlet pipe 111 has an inlet valve and an inlet flow meter and is connected to a CO2 gas tank 7. Multiple inlet branch pipes 104, preferably 10-15, are evenly distributed on the circular inlet pipes 103 and the inlet branch pipes 104, and can be connected by welding. Multiple air holes 109 with a diameter of 1-5 mm are evenly distributed on the circular inlet pipes 103 and the inlet branch pipes 104. The inlet pipe 111 has an inlet valve and an inlet flow meter for monitoring and adjusting the inlet volume.

[0036] The self-priming mixer includes a mixing shaft 102, a motor driving the mixing shaft 102, and a self-priming cylindrical hollow mixing paddle. The mixing paddle is evenly arranged at the upper, middle, and lower parts of the mixing shaft 102. The mixing paddle includes a positioning cylindrical tube fixedly sleeved outside the mixing shaft 102. The positioning cylindrical tube is placed between two limiting rings 115 on the mixing shaft 102. An upper support plate 107 and a lower support plate 105 are provided on the top and bottom outer edges of the positioning cylindrical tube. Multiple mixing cylinders 108 with a diameter of 1-10cm are evenly arranged between the outer edges of the upper support plate 107 and the lower support plate 105. Multiple mixing blades 106 are arranged outward on the mixing cylinders 108. The mixing blades 106 are arc-shaped.

[0037] The stirring cylinder 108 has a first hollow pipe 114 inside, and multiple micro-holes 110 with a diameter of 1-3 mm are uniformly arranged on the stirring cylinder. Multiple second hollow pipes 113 are uniformly arranged radially inside the upper support plate 107 and the lower support plate 105. The stirring shaft 102 has a third hollow pipe 112 inside. The first hollow pipe 114 and the second hollow pipe 113 are connected to each other, and the second hollow pipe 113 and the third hollow pipe 112 are connected to each other. Adjacent first hollow pipes 114 are connected through a fourth hollow pipe, which is placed inside the upper support plate 107 and the lower support plate 105. Example 2

[0038] The method for preparing UV absorber UV-612 using the reaction system shown in Example 1 includes the following steps:

[0039] S101: Feed the raw material 2,6-di-tert-butylphenol, liquid alkali (32% sodium hydroxide aqueous solution), and solvent N,N-dimethylformamide (boiling point 153℃) sequentially into the stainless steel high-pressure reactor equipped with a self-priming stirrer through the feed port. After feeding, start the stirrer and set the stirring speed to 800-1000 r / min. At this time, the temperature inside the reactor is slowly raised to 155-160℃ by the steam in the jacket. The solvent N,N-dimethylformamide begins to reflux. The reactor is equipped with a water separator with cooling circulating water. The purpose is to reflux the solvent N,N-dimethylformamide and separate the water produced in the reaction. When no water is produced or a small amount of water is produced in the system, the content of raw material 2,6-di-tert-butylphenol in the system is detected online by an online high-performance liquid chromatography detector. When the content of raw material 2,6-di-tert-butylphenol is ≤1%, the reaction is stopped and the water separator is turned off.

[0040] S102: Then, CO2 gas is introduced into the reactor. The CO2 gas passes through the gas pipeline system to the gas diffusion coils (three gas diffusion coils are welded to the top, middle, and bottom of the reactor). CO2 gas is continuously introduced into the reactor until the pressure reaches 0.4-0.6 MPa. The reactor is then kept at 155-160℃ for 8-12 hours. After the reaction, the outlet condenser is opened, and the reflux condenser is closed. Excess CO2 is discharged from the reactor through the outlet pipe, and the pressure is reduced to atmospheric pressure. The solvent N,N-dimethylformamide in the reactor is distilled off and transferred to a receiving tank. When no more CO2 is discharged, the steam in the jacket is shut off, and the cooling circulating water in the jacket is turned on to lower the temperature inside the reactor to 35-40℃.

[0041] S103: Add pure water and extractant dichloromethane sequentially from the feed port of the reactor to dissolve the phenol salts obtained in the above reaction steps in the water and the impurities in the dichloromethane. Stir at 35-40℃ for 0.5 h, then stop stirring and let stand for 10 min. Use an automatic oil separation system to transfer the lower dichloromethane oil phase to the oil phase receiving tank. Then, use an online high-performance liquid chromatography detector to sample and test the 2,6-di-tert-butylphenol content in the aqueous phase. If it is not qualified, continue to add extractant dichloromethane to the aqueous phase in the reactor and repeat the above oil separation steps until the 2,6-di-tert-butylphenol content in the aqueous phase is ≤0.1%. Generally, two extractions are required.

[0042] S104: After successful extraction, the aqueous phase in the reactor is transferred to an aqueous phase receiving tank, and the content of 2,6-di-tert-butylphenol in the aqueous phase is retested using an online high-performance liquid chromatography (HPLC) detector to ensure that the treatment is qualified. After passing the retest, the aqueous phase is transferred to the acidification reactor via a pump. After the transfer is complete, stirring is started at a speed of 300-500 r / min. Dilute hydrochloric acid is slowly added dropwise to the acidification reactor through a hydrochloric acid high-level tank to adjust the pH to 1-2. The dropwise addition process is exothermic. During the dropwise addition, the temperature inside the acidification reactor needs to be maintained at 35-40℃ using cooling circulating water in the jacket. After the dropwise addition is complete, a white solid will precipitate in the acidification reactor. At this time, the temperature is further reduced to 10-15℃ using cooling circulating water in the jacket of the acidification reactor, and the mixture is stirred for 0.5 seconds. After h, the material in the reactor is pressurized to a centrifuge with nitrogen. The centrifuge separates the white wet product from the centrifugal mother liquor. The white wet product after centrifugation continues to enter the continuous freeze-drying system. The product is freeze-dried and discharged, which is the qualified product UV absorber UV-612. The HPLC content is ≥99%, and the overall yield is ≥90%.

[0043] This invention improves the reactivity of carbon dioxide, shortens the reaction time, increases the reaction efficiency, and is suitable for industrial production.

[0044] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0045] It should be noted that the above content merely illustrates the technical concept of this utility model and cannot be used to limit the scope of protection of this utility model. For those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and all such improvements and modifications fall within the scope of protection of the claims of this utility model.

Claims

1. A reaction system for preparing ultraviolet absorber UV-612, characterized in that, Includes high-pressure reactors, reflux condensers, outflow condensers, acidification reactors, centrifuges, and continuous freeze dryers; The high-pressure reactor is equipped with a gas pipeline system and a self-priming agitator. A first jacket is installed outside the high-pressure reactor, and a first temperature control medium is installed inside the first jacket. The top of the high-pressure reactor is connected to a reflux bend, the upper end of which is connected to the middle of a reflux straight pipe. The bottom of the reflux straight pipe is connected to a water receiving tank. One end of the reflux condenser is installed at the upper part of the reflux straight pipe. The other end of the reflux condenser is connected to one end of a distillation condenser through a pipe. The other end of the distillation condenser is connected to the receiving tank. A CO2 gas tank is also connected to the top of the high-pressure reactor. A first sampling port and a first discharge port are installed at the bottom of the high-pressure reactor. The first discharge port is connected to an oil phase receiving tank and a water phase receiving tank through a pipe. The bottom of the aqueous phase receiving tank is equipped with a second sampling port and a second discharge port. The second discharge port is connected to the acidification reactor via a pump. The acidification reactor is equipped with a stirrer and a second jacket. The second jacket is equipped with a second temperature control medium. The top of the acidification reactor is connected to a hydrochloric acid high-level tank, and the bottom of the acidification reactor is connected to a centrifuge. The bottom of the centrifuge is connected to a centrifugal mother liquor tank and a continuous freeze dryer.

2. The reaction system for preparing ultraviolet absorber UV-612 according to claim 1, characterized in that, The first sampling port and the second sampling port are connected to a high-performance liquid chromatography detector.

3. The reaction system for preparing ultraviolet absorber UV-612 according to claim 1, characterized in that, The gas pipeline system includes three circular inlet pipes located at the top, middle, and bottom of the high-pressure reactor. The circular inlet pipes are fixed to the inner wall of the high-pressure reactor. Each circular inlet pipe is connected to an inlet pipe with an inlet valve and an inlet flow meter connected to a CO2 gas tank. Multiple inlet branch pipes are evenly arranged on the circular inlet pipes, and multiple air holes are evenly arranged on the circular inlet pipes and the inlet branch pipes.

4. The reaction system for preparing ultraviolet absorber UV-612 according to claim 1, characterized in that, The self-priming agitator includes a stirring shaft, a motor driving the stirring shaft, and a self-priming cylindrical hollow stirring paddle. The stirring paddle is evenly arranged at the upper, middle, and lower parts of the stirring shaft. The stirring paddle includes a positioning cylindrical tube fixedly sleeved outside the stirring shaft. The positioning cylindrical tube is placed between two limiting rings on the stirring shaft. An upper support plate and a lower support plate are provided on the top and bottom outer edges of the positioning cylindrical tube. Multiple stirring cylinders are evenly arranged between the outer edges of the upper and lower support plates. Multiple stirring blades are arranged outward on the stirring cylinders.

5. The reaction system for preparing ultraviolet absorber UV-612 according to claim 4, characterized in that, The stirring cylinder has a first hollow pipe inside, and multiple microholes are evenly arranged on the stirring cylinder. Multiple second hollow pipes are evenly arranged radially inside the upper support plate and the lower support plate. The stirring shaft has a third hollow pipe inside. The first hollow pipe and the second hollow pipe are connected to each other, and the second hollow pipe and the third hollow pipe are connected to each other. Adjacent first hollow pipes are connected through a fourth hollow pipe, which is placed inside the upper support plate and the lower support plate.

6. The reaction system for preparing ultraviolet absorber UV-612 according to claim 4, characterized in that, The stirring blades are arc-shaped.

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