Synthesis method of dibromohydantoin
By employing electrochemical in-situ bromination and a three-stage cooling crystallization method, the safety hazards and purity issues associated with liquid bromine were resolved, enabling efficient and stable production of dibromohydantoin and improving product yield and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WEIFANGDONGYUAN LIANHAI ENVIRONMENTAL TECH CO LTD
- Filing Date
- 2026-04-21
- Publication Date
- 2026-05-26
AI Technical Summary
The traditional dibromohydantoin production process poses safety hazards due to the volatility, corrosiveness, and toxicity of liquid bromine, while the low utilization rate of bromine and the violent reaction result in unsatisfactory product purity.
An electrochemical in-situ bromination technique was adopted, using solid sodium bromide as the bromine source. Electrolysis was carried out in a microchannel reactor to generate active bromine, and a three-stage stepped cooling crystallization method was combined to control the reaction temperature and mixing process.
It improves the formation stability and product quality of dibromohydantoin, reduces safety risks, increases bromine utilization and product purity, and enhances crystal uniformity and separation efficiency.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of dibromohydantoin production technology, and more particularly to a method for synthesizing dibromohydantoin. Background Technology
[0002] Dibromohydantoin (1,3-dibromo-5,5-dimethylhydantoin) is a highly efficient bromine-based disinfectant and brominating agent. Due to its advantages such as slow-release properties, broad bactericidal spectrum, and good stability, it is widely used in water treatment, industrial circulating water, medical and health care, and organic synthesis.
[0003] Traditional dibromohydantoin production processes primarily utilize liquid bromine as the brominating agent, directly reacting it with dimethylhydantoin under alkaline conditions. However, this traditional process presents several pressing technical challenges: liquid bromine itself is highly volatile, corrosive, and toxic, posing significant safety and environmental hazards during its storage, transportation, and use, demanding extremely high safety standards for production equipment and operators. Secondly, the reaction of liquid bromine with dimethylhydantoin is prone to ineffective disproportionation, leading to reduced bromine utilization, wasted bromine resources, and difficulty in further improving the yield of the final product. Furthermore, the direct use of liquid bromine results in a vigorous reaction process, prone to localized overheating, potentially triggering a series of side reactions that generate brominated byproducts or bromate impurities, leading to unsatisfactory product purity. Summary of the Invention
[0004] To address the aforementioned shortcomings, this invention provides a method for synthesizing dibromohydantoin, which can improve the stability of dibromohydantoin production and product quality.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for synthesizing dibromohydantoin, comprising: S1. Preparation of raw material aqueous solution: Dimethylhydantoin, sodium bromide and liquid alkali NaOH are mixed with deionized water to form a dimethylhydantoin aqueous solution with a mass fraction of 15%-25%, a sodium bromide aqueous solution with a mass fraction of 20%-30%, and a liquid alkali NaOH aqueous solution with a mass fraction of 10%-20%. S2. Premixing of raw material aqueous solution: The aqueous solutions of dimethylhydantoin, sodium bromide and liquid alkali NaOH obtained in S1 are mixed in a molar ratio of 1:2.0~2.3:2.5~3.0 to obtain a premix. S3. Electrochemical in-situ bromination reaction: The premix is passed into a microchannel reactor equipped with electrolytic electrodes, and an electric current is applied to the premix to obtain dibromohydantoin initial solution. S4. Product crystallization, separation and drying: The product is crystallized by a three-stage stepped cooling method to obtain dibromohydantoin crystals. The product is then separated by centrifugation to obtain wet dibromohydantoin, and then dried to obtain the finished dibromohydantoin product.
[0006] As a further improvement of the present invention, the preparation temperature of the dimethylhydantoin aqueous solution in S1 is 40℃-50℃, and the preparation temperature of the sodium bromide aqueous solution is 20℃-30℃.
[0007] As a further improvement of the present invention, during the preparation of the sodium bromide aqueous solution, an inert gas is bubbled through it for 10-15 minutes.
[0008] As a further improvement of the present invention, the distance between the two electrodes of the electrolytic electrode in the microchannel reactor in S3 is controlled to be 1.0mm-2.0mm.
[0009] As a further improvement of the present invention, the premix in S3 is reacted at a temperature of 2℃-8℃ in a microchannel reactor, and the anode current density is 200A / m. 2 -400A / m 2 The reaction time is 5-10 minutes.
[0010] As a further improvement of the present invention, the three-stage stepped cooling method in S4 is specifically as follows: One cooling cycle: The temperature was reduced from 15℃ to 8℃ at a cooling rate of 0.08℃ / min, and the cooling and holding time was 90min. Secondary cooling: The temperature was reduced from 8℃ to 3℃ at a cooling rate of 0.08℃ / min, and the cooling and holding time was 65min. Three cooling cycles: The temperature was reduced from 3℃ to 1℃ at a rate of 0.07℃ / min, with a cooling and holding time of 30min.
[0011] As a further improvement of the present invention, in step S4, the temperature is lowered to 1°C and maintained for 60 minutes to grow crystals.
[0012] As a further improvement of the present invention, the drying temperature of the wet dibromohydantoin in S4 is 40℃-50℃, and the drying time is 20-40min.
[0013] The beneficial effects of this invention are: 1. This application employs electrochemical in-situ bromination technology, using safe and stable solid sodium bromide as the bromine source. Active bromine is generated on-site at the anode of a microchannel reactor and immediately participates in the reaction. This avoids the storage, transportation, and use of liquid bromine, fundamentally eliminating the safety risks and environmental hazards caused by liquid bromine volatilization and leakage, and ensuring the safety of the production process. Simultaneously, through electrochemical methods, the oxidation of bromide ions and the generation of active bromine are gradual. The generated active bromine is thoroughly and rapidly mixed with the reactants within the microchannel and immediately reacts with dimethylhydantoin, greatly reducing the ineffective disproportionation loss of bromine.
[0014] 2. By bubbling inert gas into the sodium bromide solution to remove dissolved oxygen, the competing side reaction of bromide ions being oxidized to bromate at the anode is effectively suppressed. Secondly, the microchannel reactor exhibits excellent mass and heat transfer efficiency, and combined with low-temperature reaction conditions, it can precisely control the reaction temperature, avoiding localized overheating, thereby effectively suppressing decomposition and bromination side reactions at high temperatures.
[0015] 3. A three-stage stepped cooling crystallization method is adopted. By controlling the slow cooling rate, it is beneficial to form large crystals with uniform particle size, complete crystal form, and few impurities. This optimized crystallization process not only further improves the final yield and purity of the product, but also produces crystal particles with uniformity and good flowability, which are easier to separate from solids, wash and dry, ensuring the low moisture content and excellent physical properties of the final product. Detailed Implementation
[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the scope of the invention.
[0017] This invention provides a method for synthesizing dibromohydantoin, comprising: S1. Preparation of the raw material aqueous solution, including: Preparation of S100 and dimethylhydantoin aqueous solution.
[0018] Solid dimethylhydantoin and deionized water are added to a reaction tank, the reaction temperature is controlled at 40℃-50℃, and the mixture is stirred continuously to form a dimethylhydantoin aqueous solution with a mass fraction of 15%-25%.
[0019] Preparation of S101 and sodium bromide aqueous solution.
[0020] Sodium bromide and deionized water are added to the reaction tank, and the reaction temperature is controlled at 20℃-30℃. The mixture is stirred continuously to form a sodium bromide aqueous solution with a mass fraction of 20%-30%. At the same time, an inert gas such as nitrogen or argon is bubbled into the solution for 10-15 minutes to remove dissolved oxygen.
[0021] As a further explanation of this embodiment, removing dissolved oxygen can reduce the competitive reaction of oxygen at the electrolytic anode, improve current efficiency, and prevent the formation of bromide ions (Br). - Oxidized by oxygen to bromate BrO 3- Byproducts.
[0022] S102, preparation of liquid alkali NaOH aqueous solution.
[0023] Add liquid alkali NaOH and deionized water into the reaction tank and stir continuously to form a liquid alkali NaOH aqueous solution with a mass fraction of 10%-20%.
[0024] S2, Premixing of raw material aqueous solution.
[0025] An aqueous solution of dimethylhydantoin, sodium bromide, and liquid alkali NaOH is introduced into a pipeline mixer at a molar ratio of 1:2.0~2.3:2.5~3.0 to premix and obtain a premix.
[0026] S3, electrochemical in-situ bromination reaction.
[0027] The premix is introduced into a microchannel reactor, which is equipped with electrolytic electrodes. The anode of the electrolytic electrodes is preferably a ruthenium-iridium coated titanium electrode, and the cathode is preferably 316L stainless steel. The distance between the two electrodes is precisely controlled between 1.0 mm and 2.0 mm.
[0028] The premix was reacted in a microchannel reactor at a temperature maintained between 2°C and 8°C, with an anode current density of 200 A / m. 2 -400 A / m 2 The reaction time is 5-10 minutes to obtain dibromohydantoin initial solution.
[0029] As a further explanation of this embodiment, under energized conditions, the bromide ions Br in the sodium bromide solution... - The bromine is efficiently and controllably oxidized to active bromine Br2 on the anode surface. The active bromine Br2 then comes into full contact with dimethylhydantoin and liquid alkali within the microchannel reactor, where it undergoes a bromination reaction.
[0030] S4. Product crystallization, separation and drying.
[0031] S400, crystallization. Crystallization is carried out through a three-stage stepped cooling method.
[0032] First cooling step: The initial dibromohydantoin solution was transferred to the crystallization vessel, and the initial temperature was maintained at 15°C. The temperature was then reduced to 8°C at a rate of 0.08°C / min, with the entire cooling and holding time lasting 90 minutes. This was intended to smoothly pass through the saturation point and induce the uniform formation of a large number of crystal nuclei.
[0033] Secondary cooling: The temperature was reduced from 8℃ to 3℃ at a rate of 0.08℃ / min, and the entire secondary cooling and holding time was 65 minutes. This is the core growth stage, promoting continuous and uniform crystal growth.
[0034] Three cooling cycles: The temperature was reduced from 3℃ to 1℃ at a rate of 0.07℃ / min, with the total cooling and holding time being 30 minutes. The cooling rate was further reduced near the endpoint temperature to complete the final growth, optimize crystal integrity, and reduce internal stress.
[0035] Maintain the temperature at 1℃ and continue crystal growth for 60 minutes to obtain dibromohydantoin crystals.
[0036] S402, Solid-liquid separation and drying.
[0037] After crystal growth is complete, the resulting dibromohydantoin crystal slurry is fed to a centrifuge for solid-liquid separation. The resulting wet dibromohydantoin is then transferred to a fluidized bed dryer. Drying is carried out in a drying medium at 40℃-50℃ for 20-40 minutes to finally obtain the finished dibromohydantoin product.
[0038] Example 1: S1. Preparation of the raw material aqueous solution, including: Preparation of S100 and dimethylhydantoin aqueous solution.
[0039] Solid dimethylhydantoin and deionized water are added to a reaction tank, the reaction temperature is controlled at 40°C, and the mixture is stirred continuously to form a 15% dimethylhydantoin aqueous solution.
[0040] Preparation of S101 and sodium bromide aqueous solution.
[0041] Sodium bromide and deionized water are added to the reaction tank, the reaction temperature is controlled at 20°C and the mixture is stirred continuously to form a 20% sodium bromide aqueous solution. At the same time, nitrogen gas is bubbled into the solution for 10 minutes.
[0042] S102, preparation of liquid alkali NaOH aqueous solution.
[0043] Liquid NaOH and deionized water are added to the reaction tank and stirred continuously to form a 10% (w / w) liquid NaOH aqueous solution.
[0044] S2, Premixing of raw material aqueous solution.
[0045] Dimethylhydantoin, sodium bromide, and liquid alkali NaOH are introduced into a pipeline mixer in a molar ratio of 1:2.0:2.5 to premix and obtain a premix, which is then introduced into a microchannel reactor.
[0046] S3, electrochemical in-situ bromination reaction.
[0047] The premix is introduced into a microchannel reactor, which is equipped with electrolytic electrodes. The anode of the electrolytic electrodes is preferably a ruthenium-iridium coated titanium electrode, and the cathode is preferably 316L stainless steel. The distance between the two electrodes is precisely controlled at 1 mm.
[0048] The premix was reacted in a microchannel reactor at a temperature maintained at 2°C, with an anode current density of 200 A / m. 2 The reaction time was 5 minutes, and dibromohydantoin initial solution was obtained.
[0049] S4. Product crystallization, separation and drying.
[0050] S400, crystallization. Crystallization is carried out through a three-stage stepped cooling method.
[0051] First cooling: Transfer the initial dibromohydantoin solution to the crystallization vessel, maintain the initial temperature at 15℃, and cool it down to 8℃ at a rate of 0.08℃ / min. The entire cooling and holding time is 90 minutes.
[0052] Secondary cooling: The temperature was reduced from 8℃ to 3℃ at a rate of 0.08℃ / min, and the entire secondary cooling and holding time was 65 minutes.
[0053] Three cooling cycles: The temperature was reduced from 3℃ to 1℃ at a rate of 0.07℃ / min, and the total cooling cycle and holding time was 30 minutes.
[0054] Maintain the temperature at 1℃ and continue crystal growth for 60 minutes to obtain dibromohydantoin crystals.
[0055] S402, Solid-liquid separation and drying.
[0056] After crystal growth, the resulting dibromohydantoin crystal slurry is fed to a centrifuge for solid-liquid separation. The resulting wet dibromohydantoin is then transferred to a fluidized bed dryer. Drying is carried out in a drying medium at 40°C for 20 minutes, ultimately yielding a finished dibromohydantoin product with a moisture content of less than 0.5%.
[0057] Example 2: S1. Preparation of the raw material aqueous solution, including: Preparation of S100 and dimethylhydantoin aqueous solution.
[0058] Solid dimethylhydantoin and deionized water are added to a reaction tank, the reaction temperature is controlled at 45°C, and the mixture is stirred continuously to form a 20% dimethylhydantoin aqueous solution.
[0059] Preparation of S101 and sodium bromide aqueous solution.
[0060] Sodium bromide and deionized water are added to the reaction tank, the reaction temperature is controlled at 25°C, and the mixture is stirred continuously to form a sodium bromide aqueous solution with a mass fraction of 25%. At the same time, nitrogen gas is bubbled into the solution for 13 minutes.
[0061] S102, preparation of liquid alkali NaOH aqueous solution.
[0062] Add liquid alkali NaOH and deionized water into the reaction tank and stir continuously to form a 15% (w / w) liquid alkali NaOH aqueous solution.
[0063] S2, Premixing of raw material aqueous solution.
[0064] Dimethylhydantoin, sodium bromide, and liquid alkali NaOH are introduced into a pipeline mixer in a molar ratio of 1:2.2:2.8 to premix and obtain a premix, which is then introduced into a microchannel reactor.
[0065] S3, electrochemical in-situ bromination reaction.
[0066] The premix is introduced into a microchannel reactor, which is equipped with electrolytic electrodes. The anode of the electrolytic electrodes is preferably a ruthenium-iridium coated titanium electrode, and the cathode is preferably 316L stainless steel. The distance between the two electrodes is precisely controlled at 1.5 mm.
[0067] The premix was reacted in a microchannel reactor at a temperature maintained at 5°C, with an anode current density of 300 A / m. 2 The reaction time was 8 minutes, and dibromohydantoin initial solution was obtained.
[0068] S4. Product crystallization, separation and drying.
[0069] S400, crystallization. Crystallization is carried out through a three-stage stepped cooling method.
[0070] First cooling: Transfer the initial dibromohydantoin solution to the crystallization vessel, maintain the initial temperature at 15℃, and cool it down to 8℃ at a rate of 0.08℃ / min. The entire cooling and holding time is 90 minutes.
[0071] Secondary cooling: The temperature was reduced from 8℃ to 3℃ at a rate of 0.08℃ / min, and the entire secondary cooling and holding time was 65 minutes.
[0072] Three cooling cycles: The temperature was reduced from 3℃ to 1℃ at a rate of 0.07℃ / min, and the total cooling cycle and holding time was 30 minutes.
[0073] Maintain the temperature at 1℃ and continue crystal growth for 60 minutes to obtain dibromohydantoin crystals.
[0074] S402, Solid-liquid separation and drying.
[0075] After crystal growth, the resulting dibromohydantoin crystal slurry is fed to a centrifuge for solid-liquid separation. The resulting wet dibromohydantoin is then transferred to a fluidized bed dryer. Drying is carried out in a drying medium at 45°C for 30 minutes, ultimately yielding a finished dibromohydantoin product with a moisture content of less than 0.5%.
[0076] Example 3: S1. Preparation of the raw material aqueous solution, including: Preparation of S100 and dimethylhydantoin aqueous solution.
[0077] Solid dimethylhydantoin and deionized water are added to a reaction tank, the reaction temperature is controlled at 50°C, and the mixture is stirred continuously to form a 25% dimethylhydantoin aqueous solution.
[0078] Preparation of S101 and sodium bromide aqueous solution.
[0079] Sodium bromide and deionized water are added to the reaction tank, the reaction temperature is controlled at 30°C and the mixture is stirred continuously to form a sodium bromide aqueous solution with a mass fraction of 25%. At the same time, nitrogen gas is bubbled into the solution for 15 minutes.
[0080] S102, preparation of liquid alkali NaOH aqueous solution.
[0081] Add liquid alkali NaOH and deionized water into the reaction tank and stir continuously to form a 20% (w / w) liquid alkali NaOH aqueous solution.
[0082] S2, Premixing of raw material aqueous solution.
[0083] Dimethylhydantoin, sodium bromide, and liquid alkali NaOH are introduced into a pipeline mixer in a molar ratio of 1:2.3:3.0 to premix and obtain a premix, which is then introduced into a microchannel reactor.
[0084] S3, electrochemical in-situ bromination reaction.
[0085] The premix is introduced into a microchannel reactor, which is equipped with electrolytic electrodes. The anode of the electrolytic electrodes is preferably a ruthenium-iridium coated titanium electrode, and the cathode is preferably 316L stainless steel. The distance between the two electrodes is precisely controlled at 2 mm.
[0086] The premix was reacted in a microchannel reactor at a temperature maintained at 8°C, with an anode current density of 400 A / m. 2 The reaction time was 10 min, and dibromohydantoin initial solution was obtained.
[0087] S4. Product crystallization, separation and drying.
[0088] S400, crystallization. Crystallization is carried out through a three-stage stepped cooling method.
[0089] First cooling: Transfer the initial dibromohydantoin solution to the crystallization vessel, maintain the initial temperature at 15℃, and cool it down to 8℃ at a rate of 0.08℃ / min. The entire cooling and holding time is 90 minutes.
[0090] Secondary cooling: The temperature was reduced from 8℃ to 3℃ at a rate of 0.08℃ / min, and the entire secondary cooling and holding time was 65 minutes.
[0091] Three cooling cycles: The temperature was reduced from 3℃ to 1℃ at a rate of 0.07℃ / min, and the total cooling cycle and holding time was 30 minutes.
[0092] Maintain the temperature at 1℃ and continue crystal growth for 60 minutes to obtain dibromohydantoin crystals.
[0093] S402, Solid-liquid separation and drying.
[0094] After crystal growth, the resulting dibromohydantoin crystal slurry is fed to a centrifuge for solid-liquid separation. The resulting wet dibromohydantoin is then transferred to a fluidized bed dryer. Drying is carried out at 50°C for 40 minutes to obtain a finished dibromohydantoin product with a moisture content of less than 0.5%.
[0095] Comparative Example 1 The traditional liquid bromine bromination process is adopted, and industrial-grade liquid bromine is directly used as the brominating agent to produce dibromohydantoin initial solution. The solution is then crystallized in the same manner as in Example 2, and then the same solid-liquid separation and drying are performed to obtain the dibromohydantoin finished product.
[0096] Comparative Example 2 Everything else is the same as in Example 2, except that: S400, Crystallization: The three-stage stepped cooling method is not used. The initial dibromohydantoin solution from the microchannel reactor is directly transferred to the crystallization vessel. Cooling is activated, and the solution temperature is directly reduced from 15°C to 1°C at a rate of 0.5°C / min, with a total cooling and holding time of 180 minutes. Then, it is maintained at 1°C for another 60 minutes of crystal growth, followed by the same solid-liquid separation and drying to obtain the final dibromohydantoin product.
[0097] The dibromohydantoin products prepared in the above examples and comparative examples were tested, and the results are shown in the following table:
[0098] As can be seen from the comparison of the above examples and comparative cases, under optimized process parameters, the product yield is significantly higher than that of the traditional liquid bromine method. This proves that the electrochemical method can achieve efficient and controllable conversion of bromide ions, avoiding the ineffective disproportionation and loss of bromine in the traditional process, and avoiding side reactions at high temperatures, resulting in higher purity.
[0099] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above-described embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. A process for the synthesis of dibromohydantoin, characterized in that, The application relates to a preparation method of dibromohydantoin, which comprises the following steps: S1, preparation of a raw material aqueous solution, dimethyl hydantoin, sodium bromide and liquid alkali NaOH are mixed with deionized water to form a dimethyl hydantoin aqueous solution with a mass fraction of 15%-25%, a sodium bromide aqueous solution with a mass fraction of 20%-30% and a liquid alkali NaOH aqueous solution with a mass fraction of 10%-20%; S2, premixing of the raw material aqueous solution, the dimethyl hydantoin, sodium bromide and liquid alkali NaOH aqueous solutions prepared in S1 are mixed according to a molar ratio of 1:2.0-2.3:2.5-3.0 to obtain a premix; S3, an electrochemical in-situ bromination reaction, the premix is introduced into a microchannel reactor provided with electrolytic electrodes, and an electric current is applied to the premix to obtain a dibromohydantoin initial solution; S4, product crystallization, separation and drying, a three-stage stepwise cooling method is used for cooling crystallization to obtain a dibromohydantoin crystal, centrifugal separation is carried out to obtain a dibromohydantoin wet product, and then drying is carried out to obtain a dibromohydantoin finished product.
2. The method of claim 1, wherein the dibromohydantoin is synthesized by the process comprising: The preparation temperature of the dimethyl hydantoin aqueous solution in S1 is 40-50 DEG C, and the preparation temperature of the sodium bromide aqueous solution is 20-30 DEG C.
3. The method of claim 2, wherein the dibromohydantoin is synthesized by the process comprising: In the process of mixing preparation of the sodium bromide aqueous solution, inert gas is introduced into the sodium bromide aqueous solution for 10-15 min for bubbling.
4. The method of claim 1, wherein the dibromohydantoin is synthesized by the process comprising: The electrolytic electrodes in the microchannel reactor in S3 are controlled to have a spacing of 1.0-2.0 mm between the two electrodes.
5. The method for synthesizing dibromohydantoin according to claim 4, characterized in that, The premix in S3 is reacted in a microchannel reactor at a temperature of 2-8°C and an anode current density of 200 A / m 2 -400 A / m 2 for a reaction time of 5-10 min.
6. The method of synthesis of dibromohydantoin according to claim 1, wherein, The three-stage stepwise cooling method in S4 is as follows: first-stage cooling: the temperature is decreased from 15 DEG C to 8 DEG C at a cooling rate of 0.08 DEG C / min, and the cooling and maintaining time is 90 min; second-stage cooling: the temperature is decreased from 8 DEG C to 3 DEG C at a cooling rate of 0.08 DEG C / min, and the cooling and maintaining time is 65 min; third-stage cooling: the temperature is decreased from 3 DEG C to 1 DEG C at a cooling rate of 0.07 DEG C / min, and the cooling and maintaining time is 30 min.
7. The method for synthesizing dibromohydantoin according to claim 6, characterized in that, The temperature is decreased to 1 DEG C and maintained for 60 min for crystal growth in S4.
8. The method of dibromohydantoin synthesis of claim 1, wherein, The drying temperature of the dibromohydantoin wet product in S4 is 40-50 DEG C, and the drying time is 20-40 min.