Method for co-producing dibromohydantoin and bromochlorohydantoin

Abstract

The invention discloses a co-production method of dibromohydantoin and bromochlorohydantoin, and belongs to the technical field of disinfectant production, mother liquor generated in the production process of dibromohydantoin is used as a raw material to be directly used for preparing bromochlorohydantoin, and collaborative production and resource recycling of two high-value disinfectants are achieved. Comprising the following steps: firstly, synthesizing dibromohydantoin by using 5, 5-dimethyl hydantoin as a raw material, and recovering mother liquor; mixing the treated active bromine mother liquor with 5, 5-dimethyl hydantoin, carrying out chlorination reaction to generate bromochlorohydantoin, and purifying and drying to obtain a finished product. By recycling the mother liquor, the consumption of bromine and chlorine is remarkably reduced, and efficient recovery and in-situ utilization of bromine resources in the mother liquor are realized; meanwhile, the problems of safety and environmental protection caused by organic solvent extraction are avoided, the process is green, the yield is high, large-scale production is easy, and the method is suitable for large-scale preparation of disinfectants.

Description

Technical Field

[0001] This invention belongs to the field of disinfectant production technology, and particularly relates to a method for the co-production of dibromohydantoin and bromochlorohydantoin. Background Technology

[0002] Bromochlorohydantoin, as a highly efficient and broad-spectrum disinfectant, is widely used in industrial circulating water treatment, swimming pool disinfection, agricultural irrigation, and daily hygiene disinfection. Its chemical structure is stable, its action is rapid, and it has a wide applicable pH range, giving it a promising market prospect. However, the traditional synthesis process of bromochlorohydantoin typically involves a stepwise reaction of 5,5-dimethylhydantoin with halogenating agents such as chlorine and bromine. This process suffers from problems such as a long process route, high raw material consumption, large amounts of waste, and unstable product purity, which hinders its industrial promotion and application.

[0003] Dibromohydantoin is an important bromination reagent and disinfectant, characterized by high active bromine content, good storage stability, and ease of use. It is commonly used in bromination reactions in chemical and pharmaceutical processes, as well as in disinfection of public places. However, dibromohydantoin has poor solubility and stability in water, limiting its direct application. Furthermore, the mother liquor generated during its production is typically discharged as wastewater, resulting in resource waste and environmental pollution.

[0004] In existing technologies, dibromohydantoin and bromochlorohydantoin are mostly produced in a stepwise, independent manner, lacking material recycling and synergistic utilization mechanisms. Although some studies have focused on product stability or clean synthesis, for example, CN117356574A discloses a dibromohydantoin disinfectant for wastewater treatment and its preparation process. By adding an environmentally friendly, oxidation-resistant thickener, an antioxidant, and a bismuth carboxylate catalyst, the stability of the disinfectant is improved. However, this method still needs further optimization of the thickener formulation to enhance its stability and thickening effect. In addition, CN118894806A proposes a clean synthesis method for bromochlorohydantoin using bromination + electrolysis + chlorination, achieving a high product yield without generating wastewater. However, this method relies on a complex electrolysis device, and optimizing the electrolysis reaction conditions to improve efficiency and yield remains a challenge.

[0005] While these existing technologies have improved product stability and reduced wastewater discharge to some extent, they have failed to fundamentally solve the problems of low resource utilization efficiency, unstable product quality, and poor wastewater recycling rates in the preparation of bromochlorohydantoin and dibromohydantoin. Therefore, developing an integrated green synthesis method that can achieve the co-production of two disinfectants, fully utilize the bromine resources in the by-product mother liquor, reduce the consumption of fresh bromine, lower wastewater discharge, and simplify the process has become a critical technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a method for the co-production of dibromohydantoin and bromochlorohydantoin, using the mother liquor generated during the production of dibromohydantoin as a direct raw material for the synthesis of bromochlorohydantoin, thereby solving the problems of low resource utilization, serious environmental pollution, high production costs and unstable product quality in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for the co-production of dibromohydantoin and bromochlorohydantoin includes the following steps: S1. Preparation of dibromohydantoin: 5,5-Dimethylhydantoin was mixed with a 15-25% sodium hydroxide aqueous solution and stirred at 20-25 °C until completely dissolved to form sodium hydantoin. Bromine was slowly added dropwise at 20-25 °C, and the reaction was continued with stirring for 2-3 hours. After the reaction was completed, the temperature was lowered to 5-10 °C to crystallize. The crude dibromohydantoin was obtained by vacuum filtration, and the filtrate was used as a bromine-containing mother liquor. S2, Activation treatment of bromine-containing mother liquor: The bromine-containing mother liquor obtained in step S1 is adjusted to pH 4.0-5.0 with acid to prevent bromine from undergoing disproportionation side reactions under alkaline conditions; chlorine gas is introduced at 25-30 °C to oxidize the bromide ions in the mother liquor to active bromine, forming an active bromine solution that can be used for subsequent reactions. The entire process is carried out in the aqueous phase and no organic solvents are used. S3. Preparation of bromochlorohydantoin using mother liquor: 5,5-Dimethylhydantoin was mixed with an aqueous sodium hydroxide solution to prepare a sodium salt, which was then added to the active bromine solution obtained in step S2. The reaction was carried out at 20-25 °C for 1 hour. Chlorine gas was introduced and the reaction was continued for 2 hours to generate bromochlorohydantoin. After the reaction was completed, the mixture was cooled and crystallized. The crude bromochlorohydantoin was obtained by solid-liquid separation. S4. Purification and drying of bromochlorohydantoin: The crude bromochlorohydantoin was dissolved in hot water, filtered while hot to remove insoluble impurities, decolorized with activated carbon, and then filtered again for precision. After cooling and crystallization, it was then filtered and dried under vacuum to obtain a high-purity bromochlorohydantoin product.

[0008] Preferably, the sodium hydroxide aqueous solution in step S1 has a mass fraction of 20-25%, and the molar ratio of bromine to 5,5-dimethylhydantoin is 2.0:1 to 2.1:1.

[0009] Preferably, the crystallization temperature in step S1 is 5-10 ℃ and the crystallization time is 0.5-1.5 hours; the filter cake is washed with cold deionized water after vacuum filtration.

[0010] Preferably, the acid in step S2 is dilute sulfuric acid or dilute hydrochloric acid with a concentration of 5-20%, and the amount of chlorine gas introduced is monitored by the ORP value to determine the reaction endpoint, with a target ORP of +400 to +500 mV.

[0011] Furthermore, the active bromine in step S2 is a Br2 or Br3⁻ complex, and the active bromine solution is prepared and used immediately without long-term storage or solvent extraction.

[0012] Preferably, the molar ratio of chlorine gas to 5,5-dimethylhydantoin in step S3 is 1.0:1 to 1.1:1, and the total reaction time is controlled within 2–3 hours.

[0013] Preferably, the hot water temperature in step S4 is 75-85 ℃, and the amount of activated carbon added is 1-2 wt% of the crude mass.

[0014] Preferably, in step S4, the cooling crystallization is slowly cooled from 60°C to room temperature, and then the crystals are grown in an ice bath at 5°C for 0.5-1 hour.

[0015] Furthermore, the exhaust gases generated in steps S2 and S3 are absorbed and treated using a 20% sodium hydroxide solution.

[0016] The method does not require the use of organic solvents for extraction, distillation, or recrystallization. All reactions and separations are completed in an aqueous system, making it suitable for continuous industrial production.

[0017] The beneficial effects of this invention compared to the prior art are: This invention utilizes the mother liquor generated during the production of dibromohydantoin as a raw material for the synthesis of bromochlorohydantoin, achieving the co-production of two disinfectants and the resource-based recycling of the mother liquor. This method significantly reduces the individual consumption of bromine and chlorine, lowering raw material costs. Simultaneously, it organically combines two independent production processes into a complete production system, simplifying operation steps and improving equipment utilization and production efficiency. This process effectively reduces the discharge of bromine-containing wastewater, lowering environmental pollution and meeting the requirements of green chemistry and clean production. Through the rational utilization of the mother liquor and optimization of process parameters, the purity and yield of bromochlorohydantoin are improved, product stability is enhanced, and its application range is expanded. This method is simple to operate, operates under mild conditions, and is easily implemented for continuous industrial production, demonstrating significant economic benefits and market competitiveness. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0019] A method for the co-production of dibromohydantoin and bromochlorohydantoin includes the following steps: 1800 kg of a 20% sodium hydroxide solution was added to the reactor, followed by slow addition of 400 kg of 5,5-dimethylhydantoin, stirring until completely dissolved. 940 kg of liquid bromine was added dropwise using a metering pump at 20-25 °C, controlling the dropping rate to ensure the reaction temperature did not exceed 30 °C. After the addition was complete, stirring continued for 2.5 hours, with TLC monitoring to ensure complete reaction. The solution was cooled to 5-10 °C and crystallized at this temperature for 1 hour. Solid-liquid separation was performed using a vacuum filtration device. The filter cake was washed twice with cold water, yielding approximately 820 kg of wet crude dibromohydantoin. After vacuum drying at 50-60 °C, 780 kg of a white crystalline product was obtained, with a yield of 94.2% and a purity ≥98.5%.

[0020] The resulting mother liquor, approximately 3200 kg, was analyzed by ion chromatography to have a Br⁻ concentration of 1.92 mol / L. This was transferred to a reactor, where 10% (w / w) dilute sulfuric acid was introduced to adjust the pH to 4.2. Then, 218 kg of chlorine gas was slowly introduced at 28 °C. Simultaneously, the ORP value was monitored online, rising to +460 mV, and the solution turned reddish-brown, indicating that Br⁻ had been largely converted to the Br₂ / Br₃⁻ active species. The chlorine introduction was stopped, and stirring continued for 30 minutes to obtain an active bromine solution.

[0021] The active bromine solution was transferred to another reactor, and a new batch of 345 kg of 5,5-dimethylhydantoin and 1500 kg of 20% NaOH solution were added. After stirring to form a salt, the mixture was reacted at 22 °C for 1 hour. Then, chlorine gas was introduced to carry out a chlorination reaction for 2 hours. After the reaction was completed, the mixture was cooled, crystallized, and filtered to obtain crude bromochlorohydantoin.

[0022] The crude bromochlorohydantoin was dissolved in hot water and heated to 80 °C until completely dissolved. The solution was filtered while hot to remove insoluble matter. 12 kg of activated carbon was added to the filtrate, and the mixture was stirred for decolorization for 30 minutes. After another precise filtration, the filtrate was slowly cooled to room temperature, and then further cooled in an ice bath to 5 °C for crystal growth for 1 hour. After crystallization, the solution was filtered, and the filter cake was vacuum dried at 50 °C to 60 °C for 5 hours to obtain 592 kg of white needle-like bromochlorohydantoin product. Example 2

[0023] Two parallel reaction systems were configured for continuous production. The first system was a dibromohydantoin synthesis unit, processing 50 kg of 5,5-dimethylhydantoin per batch. Following the method in Example 1, it was mixed with 180 kg of a 20% sodium hydroxide solution, and 110 kg of liquid bromine was added dropwise at 20-25°C, controlling the reaction temperature to not exceed 30°C. After reacting for 2.5 hours, the mixture was cooled and crystallized, yielding 113 kg of the finished dibromohydantoin product after filtration.

[0024] 460 kg of mother liquor was produced. This mother liquor was transferred to the oxidation reaction unit of the second system, which was equipped with an automatic pH control device. Dilute sulfuric acid was added to adjust the pH to 4.5, and chlorine gas was introduced at 26 °C. The reaction endpoint was monitored in real time using an ORP probe, with a target value of +440 mV. After oxidation, an active bromine solution was obtained and directly transferred to the bromochlorohydantoin synthesis reactor.

[0025] 43.5 kg of 5,5-dimethylhydantoin and 180 kg of sodium hydroxide solution were added to a synthesis reactor and stirred to form a sodium salt. Then, the aforementioned active bromine solution was added, and the reaction was carried out at 22 °C for 1 hour. Chlorine gas was then introduced, and the reaction continued for 2 hours. After the reaction was completed, the mixture was cooled and crystallized. The resulting crude bromochlorohydantoin was obtained by filtration and washing.

[0026] The crude product was dissolved in hot water, decolorized with activated carbon, and then filtered through a precision process followed by programmed cooling and crystallization to finally obtain 86.3 kg of bromochlorohydantoin. The system operated continuously for ten cycles, with stable product quality in each batch, a purity of no less than 98.6%, and an average yield of 85.7%. The system operated stably, with no signs of accelerated equipment corrosion, and no free halogens were detected in the exhaust gas after absorption by sodium hydroxide solution.

[0027] In summary, this invention utilizes dibromohydantoin mother liquor to prepare bromochlorohydantoin, achieving the co-production and resource recycling of two disinfectants. This significantly improves raw material utilization, reduces bromine and chlorine consumption, decreases wastewater discharge, and is energy-saving and environmentally friendly. Simultaneously, it simplifies the process, reduces production costs, and enhances product purity and stability, demonstrating good economic benefits and promising prospects for industrial application.

[0028] Many specific details have been set forth in the foregoing description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed above.

Claims

1. A method for the co-production of dibromohydantoin and bromochlorohydantoin, characterized in that: Includes the following steps: S1. Preparation of dibromohydantoin: 5,5-Dimethylhydantoin was mixed with a 15-25% sodium hydroxide aqueous solution and stirred at 20-25 °C until completely dissolved to form sodium hydantoin. Bromine was slowly added dropwise at 20-25 °C, and the reaction was continued with stirring for 2-3 hours. After the reaction was completed, the temperature was lowered to 5-10 °C to crystallize. The crude dibromohydantoin was obtained by vacuum filtration, and the filtrate was used as a bromine-containing mother liquor. S2, Activation treatment of bromine-containing mother liquor: The bromine-containing mother liquor obtained in step S1 is adjusted to pH 4.0-5.0 with acid to prevent bromine from undergoing disproportionation side reactions under alkaline conditions; chlorine gas is introduced at 25-30 °C to oxidize the bromide ions in the mother liquor to active bromine, forming an active bromine solution that can be used for subsequent reactions. The entire process is carried out in the aqueous phase and no organic solvents are used. S3. Preparation of bromochlorohydantoin using mother liquor: 5,5-Dimethylhydantoin was mixed with an aqueous sodium hydroxide solution to prepare a sodium salt, which was then added to the active bromine solution obtained in step S2. The reaction was carried out at 20-25 °C for 1 hour. Chlorine gas was introduced and the reaction was continued for 2 hours to generate bromochlorohydantoin. After the reaction was completed, the mixture was cooled and crystallized. The crude bromochlorohydantoin was obtained by solid-liquid separation. S4. Purification and drying of bromochlorohydantoin: The crude bromochlorohydantoin was dissolved in hot water, filtered while hot to remove insoluble impurities, decolorized with activated carbon, and then filtered again for precision. After cooling and crystallization, it was then filtered and dried under vacuum to obtain a high-purity bromochlorohydantoin product.

2. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: The sodium hydroxide aqueous solution in step S1 has a mass fraction of 20-25%, and the molar ratio of bromine to 5,5-dimethylhydantoin is 2.0:1 to 2.1:

1.

3. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: The crystallization temperature in step S1 is 5-10 ℃, the crystallization time is 0.5-1.5 hours, and the filter cake is washed with cold deionized water after vacuum filtration.

4. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: The acid mentioned in step S2 is dilute sulfuric acid or dilute hydrochloric acid with a concentration of 5-20%. The amount of chlorine gas introduced is monitored by the ORP value to determine the reaction endpoint, with a target ORP of +400 to +500 mV.

5. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: The active bromine in step S2 is a Br2 or Br3⁻ complex. The active bromine solution is prepared and used immediately, without long-term storage or solvent extraction.

6. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: In step S3, the molar ratio of chlorine gas to 5,5-dimethylhydantoin is 1.0:1 to 1.1:1, and the total reaction time is controlled within 2–3 hours.

7. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: The hot water temperature in step S4 is 75-85 ℃, and the amount of activated carbon added is 1-2 wt% of the crude mass.

8. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: In step S4, the cooling crystallization is performed by slowly cooling from 60 °C to room temperature, and then in an ice bath at 5 °C for 0.5-1 hour to grow crystals.

9. The method for co-producing dibromohydantoin and bromochlorohydantoin according to claim 1, characterized in that: The exhaust gases generated in steps S2 and S3 are absorbed and treated with a 20% sodium hydroxide solution.