A continuous production method of an ultraviolet absorber intermediate

Abstract

This invention belongs to the field of fine chemicals, specifically relating to a continuous production method for ultraviolet absorber intermediates. The method involves a diazotization reaction between an acidic amine solution and a sodium nitrite solution in a microreactor to generate a diazonium salt solution. This solution is then coupled with an alkaline phenol solution in a split-flow reactor to generate a crude UV-234 intermediate product. Finally, the product is obtained by filtration and washing. The method provided in this application effectively shortens the diazotization and coupling reaction time for preparing the UV-234 intermediate, reduces the decomposition of the diazonium salt, improves product quality, eliminates the need for slurrying of the raw material solution, ensures uniform and long-term stability of the material, exhibits minimal scale-up effects, minimizes equipment wear, and is simple to operate, facilitating industrial scale-up and demonstrating promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of fine chemicals, specifically to a continuous production method and system for ultraviolet absorber intermediates. Background Technology

[0002] Ultraviolet (UV) absorbers are a crucial class of light stabilizers, playing an irreplaceable role in protecting materials from UV damage. These compounds efficiently and selectively absorb UV rays in the 290-400 nanometer wavelength range from sunlight and other light sources, especially the short-wave UV rays that are harmful to humans and materials. By absorbing these harmful rays, UV absorbers not only protect their own structure from damage but also effectively slow down the aging process of polymer materials such as plastics, coatings, and textiles under sunlight, extending their service life and maintaining performance stability.

[0003] Based on their molecular structures, ultraviolet (UV) absorbers can be classified into several categories, such as benzophenones, benzotriazoles, salicylates, and triazines. Among them, benzotriazoles are among the most widely produced and used UV absorbers on the market due to their good compatibility with polymers, stable performance, low toxicity, strong absorption capacity, and resistance to oil and discoloration. They are widely used in various synthetic materials, providing a solid guarantee for the sun protection and anti-aging properties of products. UV-234, also known as 2-(2'-hydroxy-3',5'-bis(a,a-dimethylbenzyl)phenyl)benzotriazole, is a high-performance UV absorber with broad application prospects and market value.

[0004] The main industrial synthesis route for UV-234 currently uses aromatic amines and alkylphenols as raw materials, followed by a diazotization and coupling reaction to obtain an azo intermediate, and then a ring-closure reduction reaction to synthesize the target product. This synthesis method is low-cost, uses readily available raw materials, and has a simple process, but the yield is relatively low. The intermediate for generating UV-234 through the diazotization and coupling reaction is also known as 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole.

[0005] In traditional diazotization coupling reactions, both diazotization and coupling reactions are accompanied by heat release, classifying them as exothermic reactions. Due to the significant thermal sensitivity of diazonium salts, they are easily decomposed by temperature fluctuations. Therefore, temperature control during diazotization and coupling steps requires extremely precise and strict control, often maintaining a low-temperature environment of 0–5°C. In traditional industrial practice, the production of UV-234 intermediates is mostly carried out using batch reactors. In this production mode, when the feed liquid is mixed at different temperatures and pH values ​​within the reactor, it often faces the challenge of uneven mass and heat transfer efficiency, leading to fluctuations and deviations in local temperature, pH, and chemical composition. These adverse factors significantly exacerbate side reactions, ultimately affecting the overall yield and quality of the product, resulting in decreased production efficiency and economic benefits. Continuous production of UV-234 intermediates can effectively solve these problems. Currently, the following information is available regarding continuous diazotization coupling production:

[0006] Chinese patent (CN 116969856A) reports a method for the continuous synthesis of diazonium salts of weakly basic aromatic amines. This invention utilizes the combined action of ultrasound and microbubbles to conduct the reaction within a tubular microreactor. Although the diazonium salt yield is high, the reaction apparatus is complex, the operation is difficult, and it results in a significant waste of water, which is inconsistent with green production.

[0007] Chinese patent (CN 116283650A) reports a method of atomizing and spraying a solution of molten o-amine and acid into water or an organic solvent to obtain a slurry containing o-amine salts. This slurry is then subjected to a diazotization reaction with a diazotizing agent in a multi-stage pipeline reactor, followed by a coupling reaction with phenolic substances. However, since the reactant in this method is a slurry, the pipeline reactor is prone to clogging during operation.

[0008] Chinese patent (CN 118084718 A) reports a continuous synthesis method for preparing azobenzene intermediates and benzotriazole light stabilizers. The continuous method involves mixing a diazonium salt solution and a phenolic compound solution in a Venturi effect-based mixer to prepare a mixed fluid; the mixed fluid is then passed into a continuous reactor to prepare the azobenzene intermediate through a coupled reaction. However, this method still employs a batch operation for diazonium salt preparation, which is time-consuming and unsafe.

[0009] Yang Shulin et al. from the Shenyang Chemical Research Institute achieved continuous production of diazo coupling reactions using diversified microreactors, significantly broadening the synthetic range of azo pigments (see *Dyes & Dyeing*, April 2017, Vol. 54, No. 2). However, the literature regrettably did not detail the specific experimental conditions and the fine-tuning parameters of the microchannels. In this synthetic process, the mixing method is collision-type or laminar flow contact mixing, which, compared to micron-level dispersion mixing, may lead to an increase in pigment particle size and a decrease in uniformity, thus affecting the reactant conversion rate.

[0010] Microreactor continuous synthesis is a technology that enables mixing and reaction in micrometer- to millimeter-scale pipeline systems, ushering in a new era for chemical and pharmaceutical production. This technology relies on highly efficient continuous-flow microchannel reactors, leveraging superior heat and mass transfer performance and low liquid retention to achieve precise dynamic control of reaction conditions. This innovation not only improves safety and environmental standards in production but also significantly enhances reaction efficiency and ensures accurate control of reaction conditions. Simultaneously, it effectively reduces energy consumption, contributing to the green and sustainable development of the chemical industry. Related information on microreactors includes:

[0011] Chinese invention patent (CN101224405B) reports a reactor / mixer with a micro-sieve structure, integrating inlet pipes for the continuous and dispersed phases, an outlet pipe for the mixed solution, a distribution chamber at the inlet, and a product collection chamber at the outlet. This design is suitable for the synthesis of low-viscosity products, such as the preparation of inorganic nanoparticles, but it is limited in the synthesis of high-viscosity pigments because the structure of the collection chamber and other components easily leads to the accumulation and precipitation of reactants and pigments, clogging the channels, interfering with the continuous synthesis process, and affecting production efficiency and product quality.

[0012] Currently, continuous synthesis techniques involving diazo coupling still have limitations in their mixing principles, failing to fully utilize micron-level dispersion and mixing processes to achieve more efficient mixing enhancement. Furthermore, existing microreactor structural designs have not adequately considered or adapted to the specific system requirements of high-viscosity azo pigment synthesis, lacking targeted optimization and improvement. This, to some extent, limits the widespread application and performance improvement of this technology in the field of pigment synthesis. Summary of the Invention

[0013] To address the above shortcomings, this invention aims to provide a continuous production method for ultraviolet absorber intermediates, solving problems such as diazotization blockage, heat dissipation, low yield, and easy encapsulation of raw materials, aggregation and precipitation, and channel blockage encountered in the continuous synthesis of UV-234 intermediates.

[0014] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0015] A continuous production method for ultraviolet absorber intermediates includes a system for continuous production of ultraviolet absorber intermediates, wherein the system includes a continuous diazotization unit and a continuous coupled reaction unit; the continuous diazotization unit includes a first miniaturized split-flow reactor and a first microreactor, and the continuous coupled reaction unit includes a second miniaturized split-flow reactor and a second microreactor.

[0016] The method includes the following steps:

[0017] 1) The amine solution and the sodium nitrite solution are simultaneously and continuously introduced into the first miniaturized split flow reactor at a rate of 5 ml to 40 ml / min to mix and react initially to obtain a mixed reaction solution A. The mixed reaction solution A is then introduced into the first microreactor to react and obtain a diazonium salt solution.

[0018] 2) Diazonium salt solution and phenolic solution are simultaneously and continuously introduced into the second miniaturized split flow reactor at a rate of 5 ml to 60 ml / min to mix and react initially to obtain mixed reaction solution B. Mixed reaction solution B is then introduced into the second microreactor for coupled reaction to generate crude UV-234 intermediate product.

[0019] 3) The crude UV-234 intermediate product is filtered and washed to obtain the UV-234 intermediate product;

[0020] Wherein: the amine solution is a homogeneous solution of concentrated sulfuric acid, m-nitroaniline and water;

[0021] The phenolic solution is a homogeneous solution of methanol, surfactant, sodium hydroxide, and 2,4-dicumylphenol.

[0022] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediate, the amine solution is prepared in a molar ratio of concentrated sulfuric acid, water and m-nitroaniline of 1-4:100-400:1; preferably 3-4:100-150:1.

[0023] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediate, the molar ratio of sodium nitrite to water in the sodium nitrite solution is 1:0.73 to 6.05.

[0024] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediate, the molar ratio of methanol, sodium hydroxide, and 2,4-dicumylphenol is 250-1500:5.5-8:1.

[0025] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediate, the surfactant is one of sodium dodecylbenzenesulfonate, polyethylene glycol, and hexadecyltrimethylammonium bromide, and 2 to 9 g of surfactant is added per mole of 2,4-dicumylphenol.

[0026] The mixed reaction solution A is held at 5-50°C for 10-50 seconds in the first microreactor; the mixed reaction solution B is held at 5-50°C for 4-20 seconds in the second microreactor.

[0027] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediates, the continuous diazotization device includes an amine solution storage tank, a sodium nitrite aqueous solution storage tank, a first metering pump, a second metering pump, a first miniaturized split-flow reactor, a first microreactor, a diazonium salt solution buffer storage tank, and a first constant temperature bath.

[0028] The amine solution storage tank, the first metering pump, and the first miniaturized split-flow reactor are connected in series via a first pipeline;

[0029] The sodium nitrite aqueous solution storage tank, the second metering pump, and the first miniaturized split-flow reactor are connected in series via a second pipeline;

[0030] The first miniaturized split-flow reactor is connected to the first microreactor, which is connected to the diazonium salt solution buffer tank via a third pipeline. The first miniaturized split-flow reactor and the first microreactor are placed in the first constant temperature bath.

[0031] The continuous coupled reaction device includes a diazonium salt solution buffer tank, a phenolic solution tank, a third metering pump, a fourth metering pump, a second miniaturized split-flow reactor, a second microreactor, a UV-intermediate tank, and a second constant temperature bath.

[0032] The phenolic solution storage tank, the third metering pump, and the second miniaturized split-flow reactor are connected in series via a fourth pipeline;

[0033] The diazonium salt solution buffer tank, the fourth metering pump, and the second miniaturized split-flow reactor are connected in series via a third pipeline;

[0034] The second miniaturized split-flow reactor is connected to the second microreactor, which is connected to the UV-intermediate storage tank via a fifth pipeline. The second miniaturized split-flow reactor and the second microreactor are placed in the second constant temperature bath.

[0035] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediate, a first back pressure valve is provided on the first pipeline, and the first back pressure valve is located on the pipeline between the first metering pump and the first miniaturized split flow reactor.

[0036] The second pipeline is equipped with a second back pressure valve, which is located on the pipeline between the second metering pump and the first miniaturized split flow reactor.

[0037] The third pipeline is equipped with a third back pressure valve, which is located on the pipeline between the third metering pump and the second miniaturized split flow reactor.

[0038] The fourth pipeline is equipped with a fourth back pressure valve, which is located on the pipeline between the fourth metering pump and the second miniaturized split flow reactor.

[0039] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediates, the first miniaturized split-flow reactor and the second miniaturized split-flow reactor have the same structure, and from left to right, they include a first connecting part, a miniaturized liquid separator, a mixing reaction plate, and a second connecting part.

[0040] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediate, the first connecting part is provided with a first liquid inlet pipe and a second liquid inlet pipe.

[0041] The miniaturized liquid separator has two rows of rectangular microchannels on the left and right. The pointed ends of the rectangular microchannels in the two rows are staggered. The feed inlet of the left rectangular microchannel is connected to the first liquid inlet pipe, and the feed inlet of the right rectangular microchannel is connected to the second liquid inlet pipe.

[0042] The mixing reaction plate is provided with a mixing liquid reaction tank, and the mixing liquid reaction tank is tightly connected to the tail tip.

[0043] The outlet end of the liquid reaction tank is connected to the liquid outlet provided on the second connecting part.

[0044] Furthermore, in the above-mentioned continuous production method of ultraviolet absorber intermediates, the first microreactor or the second microreactor is a spiral reaction microtube.

[0045] The microreactor can be any type of microtube reactor including a microreaction tube. Preferably, the inner diameter of the microreaction tube is 0.5-10.0 mm, more preferably 1.0-4.5 mm, and even more preferably 1.0-3.0 mm; the outer diameter is 1.5-14.0 mm, more preferably 1.5-7.5 mm, even more preferably 1.5-5.0 mm, and even more preferably 10.0-50.0 m, even more preferably 10.0-30.0 m. The reaction time of the microreactor can be determined by changing the tube length.

[0046] The microreaction tube described in this application can be of various shapes, such as straight tubes, bent tubes, U-shaped tubes, loop tubes, spiral tubes, etc. Preferably, in order to save space and facilitate installation, the microreaction tube is a micro-spiral reaction tube.

[0047] The working principle of this system is as follows:

[0048] In continuous production, the constant temperature bath and thermostat are turned on. Once the system stabilizes at the required temperature, the pressure of each back pressure valve is adjusted to the desired value. Then, the first and second metering pumps are turned on to draw homogeneous solutions from the amine solution tank and sodium nitrite aqueous solution tank, respectively, and deliver them to the miniaturized split-flow reactor for uniform mixing and preliminary diazotization. The solutions are then transferred to the microreactor for further reaction. The completely reacted diazotized solution is then transferred to the diazonium salt solution buffer tank for storage. When the solution in the diazonium salt solution buffer tank reaches a certain value, the third and fourth metering pumps are turned on to draw homogeneous solutions from the phenol solution tank and diazonium salt solution buffer tank, respectively, and deliver them to the miniaturized split-flow reactor for uniform mixing and preliminary coupling. The solutions are then transferred to the microreactor for further reaction. Finally, the crude UV-234 intermediate obtained from the complete reaction is stored in the UV-234 intermediate storage tank. The crude UV-234 intermediate is then filtered, washed, and dried to obtain the final product, UV-234 intermediate.

[0049] The pressures of the first back pressure valve, the second back pressure valve, the third back pressure valve, and the fourth back pressure valve are 0.8 MPa to 10 MPa.

[0050] Preferably, the molar ratio of methanol to sodium hydroxide to 2,4-dicumylphenol is 500–1000:5.5–8:1, and 3–5 g of surfactant is added per 1 mol of 2,4-dicumylphenol.

[0051] Preferably, the added surfactant is sodium dodecylbenzenesulfonate.

[0052] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0053] 1. The technical solution provided by this invention employs a microreactor for the continuous synthesis of UV-234 intermediates. This effectively controls the reaction rate and reactant feed rate within the system, allowing the reaction liquid to be divided into dozens of fine streams in a miniaturized split-flow reactor for initial mixing and reaction. The mixture then enters a coil-type microreactor for complete reaction. Its compact structure, large specific surface area, and excellent heat transfer performance per unit volume enable rapid and effective removal of heat generated during the reaction through a heat exchange mechanism. This improves the feed rate while ensuring operational safety. Furthermore, the diazonium salt yield is high. In the coupling reaction stage, the efficient mixing ensures uniform distribution of the coupled components, effectively preventing precipitation and significantly improving the conversion rate of the coupled components, ultimately resulting in a significant improvement in the quality of the final product.

[0054] 2. The technical solution provided by this invention implements precise control over the raw material ratio, ensuring that the ratio of main raw materials is close to the theoretical optimal value, and strictly follows the preset optimal reaction conditions through an automatic control system, thereby improving reaction efficiency and product quality, reducing the generation of by-products, optimizing mass and heat transfer effects, and further promoting the accuracy of temperature control.

[0055] 3. The technical solution provided by this invention adjusts the composition ratio of raw materials, and the continuous synthesis raw material liquid is a homogeneous solution system. It does not require slurrying, and will not cause particle precipitation in the solution in the micro-reaction system, thereby clogging the microreactor and affecting subsequent production. Moreover, the whole set of equipment is easy to disassemble and assemble, which is beneficial for subsequent cleaning and maintenance after the reaction is stopped.

[0056] 4. The technical solution provided by this invention has low requirements for temperature control, requires no additional low-temperature cooling equipment, and is significantly energy-efficient. At the same time, it avoids excessive use of sodium nitrite and coupled phenolic components, saving raw materials and reducing the burden of wastewater treatment, making it environmentally friendly. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the process flow apparatus structure of the present invention;

[0058] Figure 2 This is a schematic diagram of the overall miniaturized segmented reactor device of the present invention;

[0059] Figure 3 This is a schematic diagram of the first connecting part of the miniaturized segmented reactor of the present invention;

[0060] Figure 4 This is a schematic diagram of the miniaturized liquid separation structure clip of the miniaturized segmented reactor of the present invention;

[0061] Figure 5 This is a schematic diagram of the mixing reaction plate of the miniaturized segmented reactor of the present invention;

[0062] Figure 6 This is a schematic diagram of the second connection part of the miniaturized segmented reactor of the present invention;

[0063] Figure 7 This is a liquid chromatogram of the UV-234 intermediate of the present invention.

[0064] The names of the components in the attached diagram are as follows:

[0065] 1. Amine solution storage tank; 2. Sodium nitrite aqueous solution storage tank; 3. First metering pump; 4. Second metering pump; 5. First back pressure valve; 6. Second back pressure valve; 7. First miniaturized split-flow reactor; 8. First microreactor; 9. First thermostatic bath; 10. Diazonium salt solution buffer storage tank; 11. Phenolic solution storage tank; 12. Third metering pump; 13. Fourth metering pump; 14. Third back pressure valve; 15. Fourth back pressure valve; 16. Second thermostatic bath; 17. Second miniaturized split-flow reactor; 18. Second microreactor; 19. UV-234 intermediate storage tank; 20. First pipeline; 21. Second pipeline; 22. Third pipeline; 23. Fourth pipeline; 24. Fifth pipeline; 24. First connection A; First inlet pipe A1; Second inlet pipe A2; Miniaturized liquid separator B; Mixing reaction plate C; Second connection D; Cuboid microchannel B1, with pointed end B11; Mixed liquid reaction tank C1, with outlet D1. Detailed Implementation

[0066] The present invention will be further illustrated by specific examples below. These examples and descriptions are intended to clearly demonstrate the concept of the present invention, rather than to limit the scope of application of the present invention.

[0067] Unless otherwise specified, all reagents and raw materials used in the following examples and comparative examples are commercially available products.

[0068] Example 1

[0069] This embodiment provides a continuous production system for ultraviolet absorber intermediates, see reference. Figures 1-6 This includes a continuous diazotization unit and a continuous coupled reaction unit;

[0070] The continuous diazotization device includes an amine solution storage tank 1, a sodium nitrite aqueous solution storage tank 2, a first metering pump 3, a second metering pump 4, a first miniaturized split-flow reactor 7, a first microreactor 8, a diazonium salt solution buffer storage tank 10, and a first constant temperature bath 9.

[0071] The amine solution storage tank 1, the first metering pump 3, and the first miniaturized split-flow reactor 7 are connected in series via a first pipeline 20; a first back pressure valve 5 is provided on the first pipeline 20, and the first back pressure valve 5 is located on the pipeline between the first metering pump 3 and the first miniaturized split-flow reactor 7.

[0072] The sodium nitrite aqueous solution storage tank 2, the second metering pump 4, and the first miniaturized split flow reactor 7 are connected in series via a second pipeline 21; a second back pressure valve 6 is provided on the second pipeline 21, and the second back pressure valve 6 is located on the pipeline between the second metering pump 4 and the first miniaturized split flow reactor 7.

[0073] The first miniaturized split-flow reactor 7 is connected to the first microreactor 8 of the spiral reaction microtube. The first microreactor 8 is connected to the diazonium salt solution buffer tank 10 through the third pipeline 22. The first miniaturized split-flow reactor 7 and the first microreactor 8 are placed in the first constant temperature bath 9.

[0074] The continuous coupled reaction device includes a diazonium salt solution buffer tank 10, a phenolic solution tank 11, a third metering pump 12, a fourth metering pump 13, a second miniaturized split-flow reactor 17, a second microreactor 18, a UV-234 intermediate tank 19, and a second constant temperature bath 16.

[0075] The phenolic solution storage tank 11, the third metering pump 12 and the second miniaturized split flow reactor 17 are connected in series through a fourth pipeline 23; a fourth back pressure valve 15 is provided on the fourth pipeline 23, and the fourth back pressure valve 15 is located on the pipeline between the fourth metering pump 13 and the second miniaturized split flow reactor 17.

[0076] The diazonium salt solution buffer tank 10, the fourth metering pump 13 and the second miniaturized split flow reactor 17 are connected in series through a third pipeline 22; a third back pressure valve 14 is provided on the third pipeline 22, and the third back pressure valve 14 is located on the pipeline between the third metering pump 12 and the second miniaturized split flow reactor 17.

[0077] The second miniaturized split-flow reactor 17 is connected to the second microreactor 18 of the spiral reaction microtube. The second microreactor 18 is connected to the UV-234 intermediate storage tank 19 through the fifth pipeline 24. The second miniaturized split-flow reactor 17 and the second microreactor 18 are placed in the second constant temperature bath 16.

[0078] More specifically, the first miniaturized split flow reactor 7 has the same structure as the first miniaturized split flow reactor 17, and from left to right includes a first connecting part A, a miniaturized liquid separator B, a mixing reaction plate C, and a second connecting part D, with each component sealed by a sealing gasket.

[0079] To facilitate liquid inlet, the first connecting part A is provided with a first liquid inlet pipe A1 and a second liquid inlet pipe A2;

[0080] The miniaturized liquid separator B has two rows of rectangular microchannels B1, with the pointed ends B11 of the two rows of rectangular microchannels B1 arranged alternately. The inlet of the left rectangular microchannel B1 is connected to the first liquid inlet pipe A1, and the inlet of the right rectangular microchannel B1 is connected to the second liquid inlet pipe A2. The mixing reaction plate C has a mixing liquid reaction tank C1, and the mixing liquid reaction tank C1 is tightly connected to the pointed ends B11. The outlet end of the mixing liquid reaction tank C1 is connected to the upper liquid outlet D1 provided in the second connecting part D.

[0081] When the system provided by this invention is in continuous production, the first constant temperature bath 9 and the second constant temperature bath 16 are turned on. When the system stabilizes to the required temperature, the back pressure valves of the first pipeline 20, the second pipeline 21, the third pipeline 22 and the fourth pipeline 23 are adjusted to the required pressure values. Then the first metering pump 3 and the second metering pump 4 are turned on to accurately draw the homogeneous solutions from the amine solution storage tank 1 and the sodium nitrite aqueous solution storage tank 2 and deliver them into the first miniaturized split flow reactor 7. The two raw material solutions are divided into dozens of fine fluids in the miniaturized liquid separator B and come into contact with each other. Then they enter the mixing reaction plate C for thorough mixing and preliminary diazotization. Then the diazotization reaction solution enters the first microreactor 8 to continue the reaction. Finally, the fully reacted diazotization solution is delivered into the diazonium salt solution buffer storage tank 10 for storage. When the solution in the diazonium salt buffer tank 10 reaches a certain value, the third metering pump 12 and the fourth metering pump 13 are activated to extract homogeneous solutions from the phenolic solution tank 11 and the diazonium salt buffer tank 10, respectively, and transport them into the second miniaturized split-flow reactor 17 for uniform mixing and initial coupling. The solutions are then transported into the second microreactor 18 for further reaction. The crude UV-234 intermediate obtained after complete reaction is stored in the UV-234 intermediate storage tank 19. Subsequently, the crude UV-234 intermediate is filtered, washed, and dried to obtain the final product, UV-234 intermediate.

[0082] This invention employs a metering pump to precisely control the raw material ratio, ensuring that the main raw material feed ratio is close to the theoretical optimal value of the chemical reaction. By automatically controlling the constant temperature bath and back pressure valve of the control system and strictly controlling the reaction temperature and reaction pressure, the reaction efficiency and product quality are improved, and the generation of by-products is reduced.

[0083] In the diazotization reaction carried out in the continuous diazotization unit, the miniaturized split-flow reactor used in this invention allows the amine solution and sodium nitrite solution to be separated into dozens of fine fluids in the miniaturized separator B, which then come into contact with each other and enter the mixing reaction plate C for preliminary reaction. Then, they enter the spiral reaction microtube for the next step of full reaction. With its small volume, large specific surface area and excellent heat transfer performance per unit volume, this technology can quickly and effectively remove the large amount of heat generated by the diazotization reaction during the reaction through the heat exchange mechanism, avoiding the decomposition and explosion of diazonium salts caused by high system temperature. Thus, while increasing the feeding rate, it ensures the safety of production operation and has a high diazonium salt yield.

[0084] In the coupled reaction carried out in the continuous diazotization device, the efficient mixing effect of the miniaturized split-flow reactor ensures the uniform distribution of the coupled components, effectively preventing component precipitation and thus significantly improving the conversion rate of the coupled components. Simultaneously, the system's large specific surface area and excellent heat transfer performance per unit volume allow for the rapid removal of the large amount of energy generated by the coupled reaction, avoiding the decomposition of the diazonium salt as a reactant. This improvement not only significantly enhances the quality of the final UV-234 intermediate product, but also, by connecting the continuous diazotization device and the continuous coupled reaction device, the easily decomposed diazonium salt can be coupled with phenols in a timely manner after generation. Compared with batch reactions, this invention greatly reduces the loss of diazonium salt.

[0085] Example 2

[0086] This embodiment provides a continuous production method for an ultraviolet absorber intermediate, which uses the system provided in Example 1. The specific method is as follows:

[0087] 1) At room temperature (25℃), take 34.52g of m-nitroaniline, 75g of water and 75g of 98% concentrated sulfuric acid and dissolve them in a 250ml beaker. Stir well to obtain a homogeneous amine solution.

[0088] 2) Dissolve 18.95g of sodium nitrite in 250g of water and stir until homogeneous sodium nitrite solution is obtained;

[0089] 3) Take 82.615g of 2,4-dicumylphenol, 61g of sodium hydroxide, 1.5g of sodium dodecylbenzenesulfonate and 750ml of methanol and stir them evenly in a 1000ml beaker to obtain a homogeneous phenolic solution.

[0090] 4) At room temperature, the metering pump is turned on to control the flow rate of the amine solution at 12 ml / min and the flow rate of the sodium nitrite solution at 20 ml / min. Both solutions are simultaneously and continuously introduced into the first miniaturized split-flow reactor 7 for rapid mixing and initial reaction to obtain mixed reaction solution A. Mixed reaction solution A then enters the first microreactor 8 for a residence time of 40 s, a reaction temperature of 20℃, and a reaction pressure of 3 MPa. Subsequently, the completely reacted diazotized solution is transferred to the diazonium salt solution buffer tank 10. Simultaneously, the metering pump is turned on to control the flow rate of the phenol solution at 64 ml / min and the flow rate of the diazonium salt solution at 32 ml / min. Both solutions are simultaneously and continuously introduced into the first microreactor 8. The mixture was initially reacted by rapid mixing in the second miniaturized split-flow reactor 17 to obtain mixed reaction solution B. Mixed reaction solution B was then re-entered into the second microreactor 18 for a residence time of 12 s, a reaction temperature of 20°C, and a reaction pressure of 5 MPa, yielding a solid-liquid mixture of crude UV-234 intermediate. After filtration, the crude UV-234 intermediate was obtained. The crude UV-234 intermediate was first washed and filtered three times with a 1:1 methanol:water mixture; then washed and filtered three times with pure water; finally, it was dried at 70°C for 12 h, yielding a yield of 90.94%. The chromatogram is shown in the figure. Figure 7 .

[0091] Example 3

[0092] This embodiment provides a continuous production method for an ultraviolet absorber intermediate, which uses the system provided in Example 1. The specific method is as follows:

[0093] 1) At room temperature (25℃), take 13.808g of m-nitroaniline, 30g of water and 30g of 98% concentrated sulfuric acid and dissolve them in a 100ml beaker. Stir well to obtain a homogeneous amine solution.

[0094] 2) Dissolve 7.38g of sodium nitrite in 100g of water and stir until homogeneous sodium nitrite solution is obtained;

[0095] 3) Take 33.046g of 2,4-dicumylphenol, 24.20g of sodium hydroxide, 0.6g of sodium dodecylbenzenesulfonate and 300ml of methanol and stir them evenly in a 500ml beaker to obtain a homogeneous phenolic solution.

[0096] 4) At room temperature, the metering pump is turned on to control the flow rate of the amine solution to 15 ml / min and the flow rate of the sodium nitrite solution to 25 ml / min. The two solutions are simultaneously and continuously introduced into the first miniaturized split-flow reactor 7 for rapid mixing and preliminary reaction to obtain mixed reaction solution A. Mixed reaction solution A enters the first microreactor 8 for a reaction residence time of 45 s, a reaction temperature of 20 ℃, and a reaction pressure of 3 MPa. Subsequently, the completely reacted diazotized solution is transported into the diazonium salt solution buffer storage tank 10. Simultaneously, the metering pump is turned on to control the flow rate of the phenolic solution to 64 ml / min and the flow rate of the diazonium salt solution to 32 ml / min. The two solutions are simultaneously and continuously introduced into the second miniaturized split-flow reactor (17) for rapid mixing and preliminary reaction to obtain mixed reaction solution B. Mixed reaction solution B enters the second microreactor 18 for a reaction residence time of 15 s, a reaction temperature of 20 ℃, and a reaction pressure of 5 MPa to obtain a solid-liquid mixture of UV-234 intermediate crude product. After filtration, the UV-234 intermediate crude product is obtained. First, the UV-234 intermediate crude product is washed and filtered with a methanol:water mixture of 1:1, repeated three times; then, the UV-234 intermediate crude product is washed and filtered with pure water, repeated three times; then, it is dried at 70 ℃ for 12 h to obtain a yield of 91.48%. Example

[0097] This embodiment provides a continuous production method for an ultraviolet absorber intermediate, which uses the system provided in Example 1. The specific method is as follows:

[0098] 1) At room temperature (25℃), take 20.112g of m-nitroaniline, 45g of water and 45g of 98% concentrated sulfuric acid and dissolve them in a 100ml beaker. Stir well to obtain a homogeneous amine solution.

[0099] 2) Dissolve 11.37g of sodium nitrite in 150g of water and stir until homogeneous sodium nitrite solution is obtained;

[0100] 3) Take 49.569g of 2,4-dicumylphenol, 36.60g of sodium hydroxide, 0.9g of sodium dodecylbenzenesulfonate and 450ml of methanol and stir them evenly in a 500ml beaker to obtain a homogeneous phenolic solution.

[0101] 4) At room temperature, the metering pump is turned on to control the flow rate of the amine solution to 20 ml / min and the flow rate of the sodium nitrite solution to 33.3 ml / min. The two solutions are simultaneously and continuously introduced into the first miniaturized split-flow reactor 7 for rapid mixing and initial reaction to mixed reaction solution A. Mixed reaction solution A enters the first microreactor 8 for a reaction residence time of 40 s, a reaction temperature of 20 ℃, and a reaction pressure of 3 MPa. Subsequently, the completely reacted diazotized solution is transported into the diazonium salt solution buffer storage tank 10. Simultaneously, the metering pump is activated to control the flow rate of the phenolic solution at 60 ml / min and the flow rate of the diazonium salt solution at 30 ml / min. Both solutions are simultaneously and continuously introduced into the second miniaturized split-flow reactor 17 for rapid mixing and initial reaction to a mixed reaction solution B. Mixed reaction solution B then enters the second microreactor 18, where the residence time is 14 s, the reaction temperature is 20℃, and the reaction pressure is 5 MPa, yielding a solid-liquid mixture of the crude UV-234 intermediate. After filtration, the crude UV-234 intermediate is washed and filtered three times using a 1:1 methanol:water mixture. Then, it is washed and filtered three times with pure water. Finally, it is dried at 70℃ for 12 h, yielding a yield of 92.29%.

[0102] Comparative Example 1

[0103] 1) The reaction was carried out using the existing batch reaction technology. At room temperature (25℃), 34.52g of m-nitroaniline, 75g of water and 75g of 98% concentrated sulfuric acid were dissolved in a 250ml three-necked flask and stirred until homogeneous amine solution was obtained.

[0104] 2) Dissolve 18.95g of sodium nitrite in 250g of water and stir until homogeneous sodium nitrite solution is obtained;

[0105] 3) Under continuous stirring, at a reaction temperature of 20°C and normal pressure, sodium nitrite solution was added dropwise to the amine solution in step 1 within 10 minutes, and the reaction time was 2 hours to obtain a diazonium salt solution;

[0106] 4) Take 82.615g of 2,4-dicumylphenol, 61g of sodium hydroxide, 1.5g of sodium dodecylbenzenesulfonate and 750ml of methanol and stir them evenly in a 1000ml beaker to obtain a homogeneous phenolic solution.

[0107] 5) Under continuous stirring, at a reaction temperature of 20℃ and normal pressure, the diazonium salt solution obtained in step 3 was added dropwise to the phenolic solution from step 4 within 1 hour. After the addition was complete, the reaction continued for another hour to obtain a solid-liquid mixture of the crude UV-234 intermediate. After filtration, the crude UV-234 intermediate was obtained. The crude UV-234 intermediate was first washed and filtered three times with a 1:1 methanol:water mixture; then washed and filtered three times with pure water; finally, it was dried at 70℃ for 12 hours, yielding a yield of 64.32%.

[0108] In the following examples and comparative examples:

[0109] UV-234 intermediate yield = UV-234 intermediate product solid content × concentration of UV-234 intermediate product detected by liquid chromatography / feed amount of m-nitroaniline × 100% (by mass).

[0110] The preferred implementation process conditions and methods of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above implementation process conditions and methods. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical process conditions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0111] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention and protected.

Claims

1. A continuous production method for an ultraviolet absorber intermediate, characterized in that: The system includes a continuous production system for ultraviolet absorber intermediates, which comprises a continuous diazotization unit and a continuous coupled reaction unit; the continuous diazotization unit comprises a first miniaturized split-flow reactor and a first microreactor, and the continuous coupled reaction unit comprises a second miniaturized split-flow reactor and a second microreactor; The first miniaturized split-flow reactor and the second miniaturized split-flow reactor have the same structure, and from left to right, they include a first connecting part (A), a miniaturized liquid separator (B), a mixing reaction plate (C), and a second connecting part (D). The first connecting part (A) is provided with a first liquid inlet pipe (A1) and a second liquid inlet pipe (A2). The miniaturized liquid dispensing clip (B) is provided with two rows of rectangular microchannels (B1) on the left and right sides. The pointed ends (B11) of the rectangular microchannels (B1) on the left and right sides are staggered. The feed inlet of the left rectangular microchannel (B1) is connected to the first liquid inlet pipe (A1); the feed inlet of the right rectangular microchannel (B1) is connected to the second liquid inlet pipe (A2). The mixing reaction plate (C) is provided with a mixing liquid reaction tank (C1), and the mixing liquid reaction tank (C1) is tightly connected to the tail tip (B11); The outlet end of the mixed liquid reaction tank (C1) is connected to the liquid outlet (D1) provided on the second connection part (D); The method includes the following steps: 1) The amine solution and the sodium nitrite solution are simultaneously and continuously introduced into the first miniaturized split flow reactor at a rate of 5 ml to 40 ml / min to mix and react initially to obtain a mixed reaction solution A. The mixed reaction solution A is then introduced into the first microreactor to react and obtain a diazonium salt solution. 2) Diazonium salt solution and phenolic solution are simultaneously and continuously introduced into the second miniaturized split flow reactor at a rate of 5 ml to 60 ml / min to mix and react initially to obtain mixed reaction solution B. Mixed reaction solution B is then introduced into the second microreactor for coupled reaction to generate crude UV-234 intermediate product. 3) The crude UV-234 intermediate product is filtered and washed to obtain the UV-234 intermediate product; Wherein: the amine solution is a homogeneous solution of concentrated sulfuric acid, m-nitroaniline and water; The phenolic solution is a homogeneous solution of methanol, surfactant, sodium hydroxide, and 2,4-dicumylphenol.

2. The continuous production method of the ultraviolet absorber intermediate according to claim 1, characterized in that: The molar ratio of concentrated sulfuric acid, water and m-nitroaniline in the amine solution is 1-4:100-400:

1.

3. The continuous production method of the ultraviolet absorber intermediate according to claim 1, characterized in that: The molar ratio of sodium nitrite to water in the sodium nitrite solution is 1:0.73 to 6.

05.

4. The continuous production method of the ultraviolet absorber intermediate according to claim 1, characterized in that: The molar ratio of methanol, sodium hydroxide, and 2,4-dicumylphenol is 250–1500:5.5–8:

1.

5. The continuous production method of the ultraviolet absorber intermediate according to claim 1, characterized in that: The surfactant is one of sodium dodecylbenzenesulfonate, polyethylene glycol, and hexadecyltrimethylammonium bromide, with 2 to 9 g of surfactant added per mole of 2,4-dicumylphenol.

6. The continuous production method of the ultraviolet absorber intermediate according to claim 1, characterized in that: The mixed reaction solution A is held at 5-50°C for 10-50 seconds in the first microreactor; the mixed reaction solution B is held at 5-50°C for 4-20 seconds in the second microreactor.

7. The continuous production method of the ultraviolet absorber intermediate according to claim 1, characterized in that: The continuous diazotization device includes an amine solution storage tank (1), a sodium nitrite aqueous solution storage tank (2), a first metering pump (3), a second metering pump (4), a first miniaturized split-flow reactor (7), a first microreactor (8), a diazonium salt solution buffer storage tank (10), and a first constant temperature bath (9). The amine solution storage tank (1), the first metering pump (3), and the first miniaturized split-flow reactor (7) are connected in series via the first pipeline (20); The sodium nitrite aqueous solution storage tank (2), the second metering pump (4), and the first miniaturized split flow reactor (7) are connected in series via the second pipeline (21); The first miniaturized split-flow reactor (7) is connected to the first microreactor (8). The first microreactor (8) is connected to the diazonium salt solution buffer tank (10) through the third pipeline (22). The first miniaturized split-flow reactor (7) and the first microreactor (8) are placed in the first constant temperature bath (9). The continuous coupled reaction device includes a diazonium salt solution buffer tank (10), a phenolic solution tank (11), a third metering pump (12), a fourth metering pump (13), a second miniaturized split-flow reactor (17), a second microreactor (18), a UV-234 intermediate tank (19), and a second constant temperature bath (16). The phenolic solution storage tank (11), the third metering pump (12), and the second miniaturized split-flow reactor (17) are connected in series via a fourth pipeline (23); The diazonium salt solution buffer tank (10), the fourth metering pump (13), and the second miniaturized split-flow reactor (17) are connected in series via a third pipeline (22); The second miniaturized split-flow reactor (17) is connected to the second microreactor (18). The second microreactor (18) is connected to the UV-234 intermediate storage tank (19) through the fifth pipeline (24). The second miniaturized split-flow reactor (17) and the second microreactor (18) are placed in the second constant temperature bath (16).

8. The continuous production method of the ultraviolet absorber intermediate according to claim 7, characterized in that: The first pipeline (20) is provided with a first back pressure valve (5), which is located on the pipeline between the first metering pump (3) and the first miniaturized split flow reactor (7); The second pipeline (21) is provided with a second back pressure valve (6), which is located on the pipeline between the second metering pump (4) and the first miniaturized split flow reactor (7). The third pipeline (22) is equipped with a third back pressure valve (14), which is located on the pipeline between the third metering pump (12) and the second miniaturized split flow reactor (17). The fourth pipeline (23) is equipped with a fourth back pressure valve (15), which is located on the pipeline between the fourth metering pump (13) and the second miniaturized split flow reactor (17).

9. The continuous production method of the ultraviolet absorber intermediate according to claim 6, characterized in that: The first microreactor (8) and the second microreactor (18) are both spiral reaction microtubes.

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