A method for continuous flow preparation of taurine
By preparing taurine from ethanolamine and carbon disulfide in a continuous flow reactor, the problems of low yield, long time and high risk in the existing technology have been solved, and efficient and safe taurine synthesis has been achieved, which is suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-23
- Publication Date
- 2026-03-10
AI Technical Summary
Existing methods for synthesizing taurine suffer from low yields, excessively long reaction times, and high risks, posing particular safety hazards in industrial production.
Ethanolamine and carbon disulfide are reacted in a continuous flow reactor to produce thiazole-2-thione, which is then oxidized and ring-opened with hydrogen peroxide and formic acid in the same reactor to produce taurine. The continuous flow reactor enables the reaction to be continuous and improves safety.
It significantly shortens reaction time, improves product yield and purity, reduces production costs, and features a simple, safe, and efficient process suitable for large-scale industrial production.
Smart Images
Figure CN118005540B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of taurine preparation, in particular to a method for preparing taurine by continuous flow. BACKGROUND
[0002] Taurine, also known as 2-aminoethane-1-sulfonic acid or beta-methylthioalanine, is a non-essential amino acid commonly used to improve human metabolism, liver function, and heart health. It exists in natural dietary sources, is biosynthesized in the body, and is widely used in food additives, health products, cosmetics, and pharmaceuticals. The global market size of taurine is estimated to be as high as 100,000 tons per year. There are more than 20 chemical synthesis methods for taurine, which differ in raw materials and processes.
[0003] In the prior art, due to limitations such as raw material sources, production costs, product yields, synthesis process conditions, and equipment requirements, only two types can be used for industrial production: oxirane method and ethanolamine method.
[0004] The key step of the oxirane method is the ammonolysis reaction of sodium hydroxyethyl sulfonate with liquid ammonia to prepare sodium taurate. CN112661674A proposes an optimized process for preparing taurine by the oxirane method. This method uses oxirane and sodium bisulfite to undergo ring-opening addition reaction to generate sodium hydroxyethyl sulfonate, which is then ammonolyzed to obtain sodium taurate aqueous solution. After acidification, the reaction solution is passed through cation exchange resin and anion exchange resin to remove sodium ions and sulfite ions to generate pure taurine. Oxirane is flammable, explosive, and toxic, and there are certain safety hazards in the operation process. In the step of generating sodium taurate, high temperature and high pressure conditions are required, and the use amount of liquid ammonia is large. In addition, there are many by-products, and the yield is usually less than 80%, resulting in high production cost.
[0005] The traditional method for synthesizing taurine using ethanolamine as raw material is a tank-type reaction, which has a long reaction time (usually overnight), requires high-temperature reflux, has low safety, and has certain limitations in industrial large-scale production, which can easily cause phenomena such as over-temperature, material overflow, and excessive pressure leading to reaction out of control. SUMMARY
[0006] The purpose of the present application is to overcome the above technical deficiencies and provide a method for preparing taurine by continuous flow, which solves the technical problems of low yield, long reaction time, and high risk in the prior art.
[0007] To achieve the above technical purpose, the technical solution provided by the present application is as follows:
[0008] In a first aspect, the present application provides a method for preparing taurine by continuous flow, comprising the following steps:
[0009] S1, feeding the ethanolamine alkali solution and carbon disulfide solution into a first continuous flow reactor under pressure to react, to obtain a first reaction liquid;
[0010] S2, cooling, filtering, washing and extracting the first reaction liquid to obtain thiazole-2-thione;
[0011] S3, dissolving the thiazole-2-thione in an organic acid to obtain a thiazole-2-thione solution; feeding the thiazole-2-thione solution and hydrogen peroxide solution into a second continuous flow reactor to react, to obtain a second reaction liquid, and treating the second reaction liquid to obtain taurine.
[0012] Preferably, in step S1, the molar ratio of ethanolamine to carbon disulfide is 1:(2.0-5.0).
[0013] Preferably, in step S1, the alkali solution is obtained by dissolving an alkali in water, and has a concentration of 0.8-1.6 mmol / mL; the alkali includes at least one of potassium hydroxide, sodium hydroxide and potassium carbonate, and the molar ratio of ethanolamine to alkali is 1:(2.0-5.0); the carbon disulfide solution is obtained by dissolving carbon disulfide in an organic solvent, and has a concentration of 0.8-1.6 mmol / mL; the organic solvent is tetrahydrofuran, methanol, ethanol or isopropanol.
[0014] Further preferably, the concentration of ethanolamine in the ethanolamine alkali solution is 0.3-0.5 mmol / mL.
[0015] Preferably, in step S1, the first continuous flow reactor is pressurized to 0.5-2.0 MPa; the flow rate of the raw materials into the first continuous flow reactor is 0.3-0.8 mL / min, the reaction temperature is 80-100°C, the reaction residence time is 25-67 min; and the oscillation frequency of the first continuous flow reactor is 2-8 Hz.
[0016] Preferably, step S2 specifically includes:
[0017] The first reaction liquid is cooled to room temperature, and filtered to obtain solid A and a filtrate A;
[0018] The obtained solid A is washed with cold water to obtain solid B and a filtrate B;
[0019] The filtrate A and the filtrate B are combined to obtain a filtrate C;
[0020] The filtrate C is pumped into a continuous extractor at a flow rate of 20-40 mL / min, and dichloromethane is extracted, and the organic phase is concentrated under reduced pressure to obtain solid C; the solid B and the solid C are combined to obtain thiazole-2-thione. The purity of the thiazole-2-thione obtained by the method of the present application is ≥99%.
[0021] Further preferably, the filtrate C and dichloromethane are both pumped into the continuous extractor at a flow rate of 20-40 mL / min.
[0022] Preferably, in step S3, the molar ratio of thiazole-2-thione to hydrogen peroxide is 1: (1.5-3.5).
[0023] Preferably, in step S3, the organic acid is formic acid; the concentration of the thiazole-2-thione solution is 0.3-1.1 mmol / mL.
[0024] The hydrogen peroxide solution is obtained by dissolving 30% hydrogen peroxide in a solvent, and the concentration of hydrogen peroxide is 1.6-5.0 mmol / mL; the solvent is water, methanol, ethanol or tetrahydrofuran.
[0025] Preferably, in step S3, the flow rate of the raw material into the second continuous flow reactor is 0.5-1.0 mL / min, the reaction temperature is 0-5°C, and the reaction residence time is 20-40 min; the oscillation frequency of the second continuous flow reactor is 2-8 Hz.
[0026] Preferably, in step S3, the post-treatment is to concentrate the second reaction liquid under reduced pressure to a saturated state, recrystallize with methanol or ethanol, and obtain taurine by cooling and precipitating the solid; the purity of the obtained taurine is ≥97%.
[0027] Compared with the prior art, the present application has the following advantages:
[0028] The method of the present application is to prepare taurine from ethanolamine and carbon disulfide in a continuous flow reactor. The free amino group in ethanolamine first reacts with carbon disulfide to perform N-acylation, then performs intramolecular sulfur nucleophilic substitution to generate thiazole-2-thione, and finally generates peroxymonocarbonate by hydrogen peroxide and formic acid to oxidize ring opening to generate the target product. The synthesis path of the present application is ideal, and by continuous flow reaction, the reaction time is short, the yield of the obtained taurine is high, the purity is good, and the cost is effectively reduced. The process flow is simple to operate, the reaction is safe and efficient, and it has great industrial application value, especially for realizing large-scale production in industry. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 is a process flow diagram of the present application;
[0030] Figure 2 is the 1H-NMR spectrum of taurine prepared in Example 1 of the present application. DETAILED DESCRIPTION
[0031] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.
[0032] The application provides a method for preparing taurine by using ethanolamine and carbon disulfide as raw materials in a continuous flow reactor, which can obviously shorten reaction time, improve product yield and purity, improve production safety, has simple process operation, safe and efficient reaction and high industrial application value.
[0033] The "first" and "second" mentioned in the application are only used to better distinguish the raw materials, equipment or obtained products in different steps, and are not limited to the amount or process.
[0034] The continuous flow reactor used in the application is a continuous multi-stage stirring reactor.
[0035] In the following examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.
[0036] The hydrogen peroxide used in the application is derived from 30% hydrogen peroxide, and the molar amount of hydrogen peroxide described in the following examples is the molar amount of pure H2O2; the formic acid concentration is 88% (solvent is water).
[0037] The method for preparing taurine by the continuous flow method of the application has the following synthesis route:
[0038]
[0039] The main action mechanism of the application is as follows: the free amino group in ethanolamine is first reacted with carbon disulfide to perform N-acylation, then performs intramolecular sulfur nucleophilic substitution reaction to generate thiazole-2-thione, and finally generates performic acid through hydrogen peroxide and formic acid, and the performic acid oxidizes the ring opening of thiazole-2-thione to generate 2-amino sulfonic acid, i.e. taurine. At the same time, the continuous flow reactor can effectively reduce the reaction danger of carbon disulfide; the performic acid has strong oxidizing property and strong volatility, and in the synthesis route of the application, the generation and consumption of performic acid are performed at the same time, so that the danger that may exist when directly using performic acid is avoided.
[0040] The application has the following advantages:
[0041] (1) The method for preparing taurine by using the continuous flow reactor has the characteristics of novel method, short reaction time, simple and practical operation, high product quality and yield, so that the production cost is reduced;
[0042] (2) This invention selects an ideal synthetic route, overcoming the problems of high temperature, high pressure, and long reaction time in previous preparation methods. The obtained product is easy to separate and process, and the process is simple to operate, safe and efficient, and has great industrial application value. The process of this invention can effectively avoid the disadvantages of existing reactions that cannot be mass-produced, which is more conducive to achieving the requirements of large-scale industrial production, while improving the quality and yield of taurine.
[0043] (3) The present invention adopts a continuous flow synthesis method to maintain a constant reaction temperature, avoiding phenomena such as temperature runaway, material overflow, excessive pressure and reaction runaway that occur in batch reaction, and greatly improving operability and safety.
[0044] Example 1
[0045] See Figure 1 The present invention discloses a method for preparing taurine by continuous flow, comprising the following steps:
[0046] S1, ethanolamine (244.9 mmol, 14.95 g) was dissolved in an aqueous solution of potassium hydroxide (734.7 mmol, 41.22 g) (550 mL) to form the first mixture, and carbon disulfide (734.7 mmol, 44.39 mL) was dissolved in tetrahydrofuran (505 mL) to form the second mixture. The first and second mixtures were fed into a first continuous flow reactor at a flow rate of 0.3 mL / min for reaction. The first continuous flow reactor was pressurized to 1.0 MPa, the reaction temperature was 90 °C, the reaction residence time was 67 min, and the reactor oscillation frequency was 6 Hz to obtain the first reaction solution.
[0047] S2, the first reaction solution was cooled to room temperature, and 18.11 g of white solid was filtered out. The solid was washed with water, and the filtrates were combined. The filtrate was then connected to a continuous extractor and extracted with dichloromethane. Both the filtrate and dichloromethane phases were pumped in at a flow rate of 30 mL / min. The organic phase was concentrated under reduced pressure to obtain 8.75 g of solid product.
[0048] The combined solids yielded a total of 26.86 g of thiazolyl-2-thione.
[0049] S3, thiazolium-2-thione (101.1 mmol, 12.05 g) was dissolved in formic acid (100 mL) to obtain a third mixture; 30% hydrogen peroxide (containing 160 mmol of H2O2) was dissolved in methanol (83.7 mL) to obtain a fourth mixture. The third and fourth mixtures were then introduced into a second continuous flow reactor at a flow rate of 0.5 mL / min for reaction. The reaction temperature was 0 °C, the residence time was 40 min, and the reactor oscillation frequency was 8 Hz to obtain a second reaction solution.
[0050] The second reaction solution was concentrated under reduced pressure to saturation, and recrystallized from methanol or ethanol. Upon cooling, 9.93 g of white solid precipitated. The mother liquor from recrystallization was recovered, and a second recrystallization yielded 1.42 g of white solid. The solids were combined to obtain a total of 11.35 g of taurine.
[0051] The target product prepared in this embodiment was subjected to nuclear magnetic resonance (NMR) testing, and the NMR spectrum is shown below. Figure 2 As shown, the data analysis is as follows: 1 ¹H NMR (400MHz, D₂O) δ 3.46 (t, J = 6.6Hz, 1H), 3.29 (t, J = 6.6Hz, 1H). This indicates that taurine was successfully synthesized.
[0052] Analysis revealed that the purity of the product thiazole-2-thione in this embodiment was 99.61%, with a yield of 92.01%; the purity of taurine was 97.46%, with a yield of 90.52%.
[0053] Example 2
[0054] S1, ethanolamine (245.6 mmol, 15.00 g) was dissolved in an aqueous solution of potassium hydroxide (736.8 mmol, 41.34 g) (550 mL) to form the first mixture, and carbon disulfide (736.8 mmol, 44.52 mL) was dissolved in tetrahydrofuran (505 mL) to form the second mixture. The first and second mixtures were fed into a first continuous flow reactor at a flow rate of 0.5 mL / min for reaction. The first continuous flow reactor was pressurized to 1.0 MPa, the reaction temperature was 90 °C, the reaction residence time was 40 min, and the reactor oscillation frequency was 6 Hz to obtain the first reaction solution.
[0055] S2, the first reaction solution was cooled to room temperature, and 17.60 g of white solid was filtered out. The solid was washed with water, and the filtrates were combined. The filtrate was then connected to a continuous extractor and extracted with dichloromethane. Both the filtrate and dichloromethane phases were pumped in at a flow rate of 30 mL / min. The organic phase was concentrated under reduced pressure to obtain 8.62 g of solid product.
[0056] The combined solids yielded a total of 26.22 g of thiazolyl-2-thione.
[0057] S3, thiazolium-2-thione (100.2 mmol, 11.94 g) was dissolved in formic acid (100 mL) to obtain a third mixture; 30% hydrogen peroxide (containing 160 mmol of H2O2) was dissolved in methanol (83.7 mL) to obtain a fourth mixture. The third and fourth mixtures were then introduced into a second continuous flow reactor at a flow rate of 1.0 mL / min for reaction at a temperature of 5 °C, a residence time of 20 min, and a reactor oscillation frequency of 8 Hz to obtain a second reaction solution.
[0058] The second reaction solution was concentrated under reduced pressure to saturation, and recrystallized with methanol or ethanol. Upon cooling, 8.91 g of white solid precipitated. The mother liquor from recrystallization was recovered, and a second recrystallization yielded 1.33 g of white solid. The solids were combined to obtain a total of 10.24 g of taurine.
[0059] Analysis revealed that the purity of the product thiazole-2-thione in this embodiment was 99.37%, with a yield of 89.57%; the purity of taurine was 97.35%, with a yield of 81.66%.
[0060] Comparative Example 1
[0061] The only difference from Example 1 is that the reaction residence time in the first reactor is adjusted to 20 min.
[0062] Comparative Example 2
[0063] The only difference from Example 1 is that the reaction residence time in the first reactor is adjusted to 80 min.
[0064] As observed in Examples 1, 1, and 2, different reaction residence times can lead to a decrease in yield to 56%, incomplete conversion of raw materials, or an increase in byproducts. Therefore, the present invention preferably sets the reaction residence time in the first reactor to 67 min.
[0065] Comparative Example 3
[0066] The only difference from Example 1 is that the reaction residence time in the second reactor is adjusted to 10 min.
[0067] Comparative Example 4
[0068] The only difference from Example 1 is that the reaction residence time in the second reactor is adjusted to 60 min.
[0069] As observed in Examples 1, 3, and 4, different reaction residence times can lead to a decrease in yield to 74%, incomplete conversion of raw materials, or an increase in byproducts. Therefore, the present invention preferably sets the reaction residence time in the second reactor to 40 min.
[0070] Comparative Example 5
[0071] The only difference from Example 1 is that the hydrogen peroxide solution concentration is 6.0 mmol / mL.
[0072] Comparative Example 6
[0073] The only difference from Example 1 is that the hydrogen peroxide solution concentration is 1.0 mmol / mL.
[0074] Examples 1, 5, and 6 show that excessively high hydrogen peroxide concentrations lead to direct oxidation to elemental sulfur, resulting in increased byproducts and a yield reduction of only 63%; while excessively low hydrogen peroxide concentrations result in incomplete conversion of the raw materials, reducing the yield by only 61%. Therefore, the preferred hydrogen peroxide solution concentration for the second step of the present invention is 1.9 mmol / mL.
[0075] This invention discloses a continuous flow method for preparing taurine, providing a chemical process for preparing taurine using a continuous flow reactor. In the continuous flow reactor, ethanolamine is used as the starting material, reacting with carbon disulfide in an alkaline solution to generate thiazole-2-thione. Then, taurine is obtained by ring-opening oxidation with hydrogen peroxide and formic acid to generate peroxyformic acid. This method features a simple process route and achieves continuous production. This invention overcomes the problems of high temperature, high pressure, and long reaction time in previous preparation methods. The obtained product is easy to separate and process, and the process is simple to operate, safe, and efficient, making it highly valuable for industrial applications.
[0076] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for the continuous flow production of taurine, characterized in that, The method comprises the following steps: S1, feeding an alkali solution of ethanolamine and a carbon disulfide solution into a first continuous flow reactor under pressure to react, to obtain a first reaction liquid; S2, cooling, filtering, washing and extracting the first reaction liquid to obtain thiazole-2-thione; S3, dissolving the thiazole-2-thione in an organic acid to obtain a thiazole-2-thione solution; feeding the thiazole-2-thione solution and a hydrogen peroxide solution into a second continuous flow reactor to react, to obtain a second reaction liquid, and performing post-treatment to obtain taurine; In step S1, the molar ratio of ethanolamine to carbon disulfide is 1: (2.0-5.0); In step S1, the alkali solution is obtained by dissolving an alkali in water, and the concentration is 0.8-1.6 mmol / mL; the alkali includes at least one of potassium hydroxide, sodium hydroxide and potassium carbonate, and the molar ratio of ethanolamine to alkali is 1: (2.0-5.0); The carbon disulfide solution is obtained by dissolving carbon disulfide in an organic solvent, and the concentration is 0.8-1.6 mmol / mL; the organic solvent is tetrahydrofuran, methanol, ethanol or isopropanol; In step S1, the first continuous flow reactor is pressurized to 0.5-2.0 MPa; the flow rate of the raw materials into the first continuous flow reactor is 0.3-0.8 mL / min, the reaction temperature is 80-100℃, and the reaction residence time is 25-67 min; the oscillation frequency of the first continuous flow reactor is 2-8 Hz; In step S3, the molar ratio of thiazole-2-thione to hydrogen peroxide is 1: (1.5-3.5); In step S3, the organic acid is formic acid; the concentration of the thiazole-2-thione solution is 0.3-1.1 mmol / mL; The hydrogen peroxide solution is obtained by dissolving 30% hydrogen peroxide in a solvent, and the hydrogen peroxide concentration is 1.6-5.0 mmol / mL; the solvent is water, methanol, ethanol or tetrahydrofuran; In step S3, the flow rate of the raw materials into the second continuous flow reactor is 0.5 mL / min-1.0 mL / min, the reaction temperature is 0℃-5℃, and the reaction residence time is 20-40 min; the oscillation frequency of the second continuous flow reactor is 2-8 Hz; Step S2 specifically comprises: The first reaction liquid is cooled to room temperature, and filtration is performed to obtain solid A and a filtrate A; The obtained solid A is washed with cold water to obtain solid B and a filtrate B; The filtrate A and the filtrate B are combined to obtain a filtrate C; The filtrate C is subjected to continuous extraction, and dichloromethane is used for extraction, and the organic phase is concentrated under reduced pressure to obtain solid C; the solid B and the solid C are combined to obtain thiazole-2-thione; The filtrate C and dichloromethane are both pumped into the continuous extractor at a flow rate of 20-40 mL / min; In step S3, the post-treatment is to concentrate the second reaction liquid under reduced pressure to a saturated state, and recrystallization is performed using methanol or ethanol, and solid is precipitated by cooling to obtain taurine.