Method for producing taurine by using improved ethylene oxide method

Abstract

The invention discloses a method for producing taurine by using an improved ethylene oxide method, and belongs to the technical field of fine chemical synthesis. According to the method, in a sulfonation reaction step, ethylene oxide and sulfite are subjected to a reaction in the presence of a phase transfer catalyst and a free radical inhibitor, and preferably, copper sulfate and / or an additive with dual functions of free radical inhibition and ammonolysis catalysis are / is adopted. Then, directly carrying out ammonolysis reaction on the obtained isethionate solution and ammonia water in the presence of the additive (as a Lewis acid catalyst), and finally, acidifying, carrying out membrane filtration, crystallizing and drying to obtain a high-purity taurine product. Through the innovative design of'one agent with double effects', the side reaction in the sulfonation stage is effectively inhibited, the ammonolysis reaction efficiency is remarkably improved, the whole process is carried out under the milder condition, the total yield of the final taurine product is high (can reach 87% or above), the purity is stabilized at 99.5% or above, the emission of three wastes is less, and the industrial application value is remarkable.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical synthesis technology, specifically relating to a method for producing taurine using an improved ethylene oxide process. Background Technology

[0002] Taurine, chemically known as 2-aminoethanesulfonic acid, is an important sulfur-containing amino acid with extremely wide applications in pharmaceuticals, functional food additives, pet food, and cosmetics. Currently, the mainstream industrial synthesis method for taurine globally is the ethylene oxide process (also known as the ethanolamine process). This method uses ethylene oxide and sodium bisulfite (or ammonium bisulfite) as main raw materials and typically includes the following two core steps: The first step is sulfonation: ethylene oxide undergoes a nucleophilic ring-opening addition reaction with sodium bisulfite in aqueous solution to produce the intermediate sodium hydroxyethyl sulfonate. However, this step has a significant drawback: ethylene oxide is chemically reactive and readily undergoes free radical side reactions such as ring-opening polymerization under the reaction conditions, generating byproducts such as polyethylene glycol sulfonates. This not only consumes valuable raw materials, leading to a decrease in the yield and purity of sodium hydroxyethyl sulfonate, but also increases the difficulty of subsequent separation and the burden on wastewater treatment.

[0003] The second step is the ammonolysis reaction: sodium hydroxyethyl sulfonate is reacted with ammonia water under high temperature and pressure to produce the target product, sodium taurate. This step is the bottleneck of the entire process. Traditional non-catalytic ammonolysis reaction conditions are extremely harsh, typically requiring a reaction time of 6 to 8 hours at temperatures exceeding 150°C and pressures above 3.0 MPa. This not only places extremely high demands on the safety of the reaction equipment, leading to huge energy consumption, but also easily triggers side reactions such as product decomposition and discoloration during prolonged high-temperature treatment, affecting the quality of the final product.

[0004] In addition, the entire process route also faces problems such as large emissions of waste gas, wastewater, and solid waste, complex product refining processes, and difficulty in consistently achieving pharmaceutical-grade purity standards.

[0005] To overcome these challenges, some studies have attempted to improve individual steps, such as adding polymerization inhibitors to the sulfonation step or various catalysts to the ammonolysis step. However, these improvements are often isolated and localized. Currently, there is still a lack of a comprehensive solution that can systematically and holistically optimize the entire process flow, while simultaneously suppressing side reactions at the source, enhancing the main reaction, and simplifying operations.

[0006] Therefore, developing a method for producing taurine with mild reaction conditions, high selectivity, high yield, environmental friendliness, and stable product purity has become a technical challenge that urgently needs to be solved by those skilled in the art. This invention arose in this context. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an improved method for producing taurine using the ethylene oxide process. This method aims to improve the reaction rate and selectivity, reduce reaction temperature and pressure, and decrease emissions of waste gas, wastewater, and solid waste by optimizing the reaction system, introducing a highly efficient catalyst, and improving the post-treatment process, ultimately obtaining a high-yield, high-purity taurine product.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for producing taurine using an improved ethylene oxide process, characterized by comprising the following steps: (1) Sulfonation reaction: In the presence of a phase transfer catalyst and a free radical inhibitor, ethylene oxide reacts with sulfite in an aqueous solution to produce hydroxyethyl sulfonate; (2) Ammonolysis reaction: The reaction solution obtained in step (1) is ammonolyzed with ammonia to generate taurine; (3) Acidification and purification: After acidification of the taurine solution obtained in step (2), the solution is filtered through a membrane, concentrated, crystallized and dried to obtain the taurine product.

[0009] Furthermore, the phase transfer catalyst is selected from one or more of quaternary ammonium salts, quaternary phosphonium salts, or polyethylene glycol; the amount of the phase transfer catalyst added is 0.5% to 5% of the mass of the sulfite.

[0010] Furthermore, the quaternary ammonium salt is tetrabutylammonium bromide or hexadecyltrimethylammonium bromide; the polyethylene glycol is PEG-400 or PEG-600.

[0011] Furthermore, the free radical inhibitor is one or more of copper sulfate, zinc sulfate, or their hydrates, and the amount of the free radical inhibitor added is 1% to 3% of the mass of the sulfite.

[0012] Preferably, the free radical inhibitor is a combination of copper sulfate and zinc sulfate, wherein the amount of copper sulfate added is 1.2% of the mass of sulfite, and the amount of zinc sulfate added is 0.4% of the mass of sulfite.

[0013] Furthermore, the sulfonation reaction is carried out at a temperature of 40-80°C, a pressure of 0.1-0.5 MPa, and a time of 1-4 hours.

[0014] Furthermore, in the ammonolysis reaction, the molar ratio of ammonia to hydroxyethyl sulfonate is (5-15):1; the reaction temperature is 120-160°C, the reaction pressure is 1.0-3.0 MPa, and the reaction time is 2-6 hours.

[0015] Furthermore, in step (3), the acidification is to adjust the pH of the solution to 3.5-4.5 using an inorganic acid.

[0016] Furthermore, in step (3), the membrane filtration is microfiltration or ultrafiltration.

[0017] Furthermore, the sulfite is sodium bisulfite or ammonium sulfite.

[0018] In other respects, the present invention also provides taurine prepared by the methods described herein.

[0019] Beneficial effects of the invention Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. Improved selectivity and efficiency of sulfonation reaction: By introducing a phase transfer catalyst, the mass transfer between the aqueous phase (sulfite) and the organic phase (ethylene oxide) was effectively promoted. By introducing a free radical inhibitor, side reactions such as ring-opening polymerization of ethylene oxide were significantly suppressed, increasing the yield of sodium hydroxyethyl sulfonate from about 85% in the traditional method to over 92%, while the reaction temperature and pressure were more moderate.

[0020] 2. Significantly optimized ammonolysis reaction: Using Lewis acid as an ammonolysis catalyst effectively activates the CO bond in the hydroxyethyl sulfonate molecule, reduces the activation energy of the ammonolysis reaction, and allows the reaction temperature to be reduced by 20-30°C, the pressure to be reduced by 1-2 MPa, and the reaction time to be shortened by 1-2 hours, greatly reducing energy consumption and equipment requirements.

[0021] 3. This invention creatively discovers that certain metal compounds (such as copper salts and zinc salts) possess dual catalytic functions in the aforementioned process. During the sulfonation stage, they act as highly efficient free radical inhibitors, suppressing polymerization side reactions of ethylene oxide at the source; during the ammonolysis stage, they act as Lewis acid catalysts, efficiently catalyzing the ammonolysis reaction. This dual-effect design simplifies the process flow (eliminating the need for intermediate separation and the addition of a second catalyst), reduces raw material costs and operational complexity, while ensuring high yield and high selectivity throughout the process, which is a significant advantage of this invention.

[0022] 4. Improved product purity and yield: The entire process route produces fewer byproducts. Combined with advanced refining methods such as membrane filtration, inorganic salts and colored impurities are effectively removed, resulting in a final taurine product purity of over 99.5% (dry basis) and a total yield (based on ethylene oxide) of over 85%.

[0023] 5. Environmentally friendly: The ammonia recovered during the process can be recycled, reducing ammonia consumption and emissions. The application of membrane filtration technology reduces the generation of washing water and wastewater, which aligns with the development direction of green chemistry. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Example

[0025] 1. Sulfonation: In a 2L high-pressure reactor equipped with stirring and temperature control, add 600g of deionized water and 250g of sodium bisulfite (NaHSO3). Then, add 2.5g of phase transfer catalyst tetrabutylammonium bromide (TBAB) and 1.25g of bifunctional additive copper sulfate pentahydrate (CuSO4·5H2O) sequentially. Seal the reactor and purge the air three times with nitrogen. Start stirring and heat to 60°C. Slowly introduce 105g of ethylene oxide gas, controlling the pressure inside the reactor to not exceed 0.3 MPa, and maintain this temperature for 2.5 hours. After the reaction is complete, cool to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 88.5%.

[0026] 2. Ammonolysis: The above-mentioned sodium hydroxyethyl sulfonate solution containing copper sulfate was directly transferred to a 3L autoclave without any further treatment. 800g of 25% ammonia solution was added. The autoclave was sealed, and the temperature was raised to 135°C, at which point the pressure was approximately 2.0 MPa. The reaction was maintained at this temperature for 4 hours. After the reaction was completed, the temperature was cooled to below 50°C, the pressure was slowly released, and unreacted ammonia gas was recovered. Sodium taurate solution was obtained.

[0027] 3. Refining: Transfer the sodium taurine solution to a crystallization vessel and slowly acidify it to pH 4.0 with concentrated hydrochloric acid while stirring. Filter the acidified slurry through a ceramic microfiltration membrane (0.1 μm pore size) to remove impurities such as sodium chloride and copper hydroxide. Collect the filtrate and concentrate it under reduced pressure at 60°C to one-third of its original volume, resulting in a large amount of white crystals. Slowly cool the concentrate to 5°C and allow it to crystallize for 2 hours. Centrifuge the crystals and wash them twice with a small amount of ice-cold ethanol to thoroughly remove residual copper ions. Finally, vacuum dry at 80°C for 6 hours to obtain a white, well-crystalline taurine product.

[0028] Product Analysis: 234g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 98.8%. Atomic absorption spectrometry determined the copper residue to be <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 78.2%. Example

[0029] 1. Sulfonation: Same as in Example 1, except that 2.5 g of copper sulfate pentahydrate (CuSO4·5H2O) was added. After the reaction was completed, the solution was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 91.6%.

[0030] 2. Ammonolysis: Same as in Example 1.

[0031] 3. Refining: Same as Example 1.

[0032] Product Analysis: 243g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.1%. Atomic absorption spectrometry analysis revealed a copper residue of <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 81.3%. Example

[0033] 1. Sulfonation: Same as in Example 1, except that 3.75 g of copper sulfate pentahydrate (CuSO4·5H2O) was added. After the reaction was completed, the solution was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.2%.

[0034] 2. Ammonolysis: Same as in Example 1.

[0035] 3. Refining: Same as Example 1.

[0036] Product Analysis: 253g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.5%. Atomic absorption spectrometry determined the copper residue to be <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 84.7%. Example

[0037] 1. Sulfonation: Same as in Example 1, except that 5g of copper sulfate pentahydrate (CuSO4·5H2O) was added. After the reaction was completed, the solution was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.5%.

[0038] 2. Ammonolysis: Same as in Example 1.

[0039] 3. Refining: Same as Example 1.

[0040] Product Analysis: 262g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.8%. Atomic absorption spectrometry determined the copper residue to be <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 87.6%. Example

[0041] 1. Sulfonation: Same as in Example 1, except that 6.25 g of copper sulfate pentahydrate (CuSO4·5H2O) was added. After the reaction was completed, the solution was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.7%.

[0042] 2. Ammonolysis: Same as in Example 1.

[0043] 3. Refining: Same as Example 1.

[0044] Product Analysis: 259.5g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.8%. Atomic absorption spectrometry determined the copper residue to be <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 86.8%. Example

[0045] 1. Sulfonation: Same as in Example 1, except that 7.5 g of copper sulfate pentahydrate (CuSO4·5H2O) was added. After the reaction was completed, the solution was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.5%.

[0046] 2. Ammonolysis: Same as in Example 1.

[0047] 3. Refining: Same as Example 1.

[0048] Product Analysis: 252g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.3%. Atomic absorption spectrometry determined the copper residue to be <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 84.3%. Example

[0049] 1. Sulfonation: Same as in Example 1, except that 8.75 g of copper sulfate pentahydrate (CuSO4·5H2O) was added. After the reaction was completed, the solution was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.5%.

[0050] 2. Ammonolysis: Same as in Example 1.

[0051] 3. Refining: Same as Example 1.

[0052] Product Analysis: 252g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 98.9%. Atomic absorption spectrometry determined the copper residue to be <5 ppm, meeting pharmaceutical grade standards. Based on the amount of ethylene oxide added, the overall yield was 80.2%. Example

[0053] 1. Sulfonation: In a 2L high-pressure reactor equipped with stirring and temperature control, 600g of deionized water and 250g of sodium bisulfite (NaHSO3) were added. Then, 2.5g of phase-transfer catalyst tetrabutylammonium bromide (TBAB), 2.5g of dual-functional additives copper sulfate pentahydrate (CuSO4·5H2O), and 2.5g of zinc sulfate (ZnSO4·7H2O) were added sequentially. The reactor was sealed, and the air was purged three times with nitrogen. Stirring was started, and the temperature was raised to 60°C. 105g of ethylene oxide gas was slowly introduced, controlling the pressure inside the reactor to not exceed 0.3MPa. The reaction was maintained at this temperature for 2.5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.1%.

[0054] 2. Ammonolysis: Same as in Example 1.

[0055] 3. Refining: Same as Example 1.

[0056] Product Analysis: 267g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.9%. Atomic absorption spectrometry analysis revealed residual copper and zinc levels of <5 ppm, meeting pharmaceutical-grade standards. Based on the amount of ethylene oxide added, the overall yield was 89.3%. Example

[0057] 1. Sulfonation: In a 2L high-pressure reactor equipped with stirring and temperature control, 600g of deionized water and 250g of sodium bisulfite (NaHSO3) were added. Then, 2.5g of phase-transfer catalyst tetrabutylammonium bromide (TBAB), 3g of dual-functional additives copper sulfate pentahydrate (CuSO4·5H2O), and 1g of zinc sulfate (ZnSO4·7H2O) were added sequentially. The reactor was sealed, and the air was purged three times with nitrogen. Stirring was started, and the temperature was raised to 60°C. 105g of ethylene oxide gas was slowly introduced, controlling the pressure inside the reactor to not exceed 0.3 MPa. The reaction was maintained at this temperature for 2.5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 92.3%.

[0058] 2. Ammonolysis: Same as in Example 1.

[0059] 3. Refining: Same as Example 1.

[0060] Product Analysis: 268g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.8%. Atomic absorption spectrometry analysis revealed residual copper and zinc levels of <5 ppm, meeting pharmaceutical-grade standards. Based on the amount of ethylene oxide added, the overall yield was 89.6%.

[0061] Example 10: 1. Sulfonation: In a 2L high-pressure reactor equipped with stirring and temperature control, 600g of deionized water and 250g of sodium bisulfite (NaHSO3) were added. Then, 2.5g of phase-transfer catalyst tetrabutylammonium bromide (TBAB), 1g of bifunctional additive copper sulfate pentahydrate (CuSO4·5H2O), and 3g of zinc sulfate (ZnSO4·7H2O) were added sequentially. The reactor was sealed, and the air was purged three times with nitrogen. Stirring was started, and the temperature was raised to 60°C. 105g of ethylene oxide gas was slowly introduced, controlling the pressure inside the reactor to not exceed 0.3 MPa. The reaction was maintained at this temperature for 2.5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a light blue, transparent sodium hydroxyethyl sulfonate solution. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 89.8%.

[0062] 2. Ammonolysis: Same as in Example 1.

[0063] 3. Refining: Same as Example 1.

[0064] Product Analysis: 249g of taurine product was obtained by weighing. High-performance liquid chromatography (HPLC) analysis showed a purity of 99.1%. Atomic absorption spectrometry analysis revealed residual copper and zinc levels of <5 ppm, meeting pharmaceutical-grade standards. Based on the amount of ethylene oxide added, the overall yield was 83.2%.

[0065] Comparative Example 1 (Traditional method, without any additives) 1. Sulfonation reaction: Sodium bisulfite and water were added to the reaction vessel without any catalyst or inhibitor. The reaction was carried out with ethylene oxide at 80°C and 0.4 MPa for 3 hours. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 84.3%.

[0066] 2. Ammonolysis reaction: The obtained sodium hydroxyethyl sulfonate solution was reacted with ammonia water at 180°C and 4.5 MPa for 6 hours without adding any catalyst.

[0067] 3. Refining: After acidification, the solution is directly concentrated and crystallized without membrane filtration.

[0068] Product Analysis: The solution became significantly more viscous after the sulfonation reaction. A final yield of 205g of taurine product was obtained, with a purity of 98.7% and an overall yield of 68.6%.

[0069] Comparative Example 2 (using only phase transfer catalyst, without copper sulfate) The procedure is the same as in Example 1, but instead of adding copper sulfate, only tetrabutylammonium bromide is added.

[0070] Product Analysis: The sulfonation reaction yield was improved (86.2%), but the solution still had a certain viscosity after the reaction. The ammonolysis reaction required high conditions (165°C, 3.5 MPa) for 6 hours. The final yield was 223g of taurine product with a purity of 99.2% and an overall yield of 74.6%.

[0071] Comparative Example 3 (Copper sulfate added during ammonolysis reaction) 1. Sulfonation reaction: Sodium bisulfite and water were added to a reaction vessel, with only the phase transfer catalyst tetrabutylammonium bromide (TBAB) added. The reaction was carried out with ethylene oxide at 80°C and 0.4 MPa for 3 hours. Liquid chromatography analysis showed that the yield of sodium hydroxyethyl sulfonate was 84.2%.

[0072] 2. Ammonolysis reaction: The obtained sodium hydroxyethyl sulfonate solution was reacted with ammonia water at 135°C and 2.0 MPa for 4 hours with the addition of 5g of copper sulfate pentahydrate (CuSO4·5H2O).

[0073] 3. Refining: Same as Example 1.

[0074] Product Analysis: The solution became significantly more viscous after the sulfonation reaction. The final yield was 205g of taurine product with a purity of 98.7% and an overall yield of 76.5%.

[0075] It should be noted that while the preferred embodiments of the present invention are provided in this specification, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for producing taurine using an improved ethylene oxide process, characterized in that, Includes the following steps: (1) Sulfonation reaction: In the presence of a phase transfer catalyst and a free radical inhibitor, ethylene oxide reacts with sulfite in an aqueous solution to produce hydroxyethyl sulfonate; (2) Ammonolysis reaction: The reaction solution obtained in step (1) is ammonolyzed with ammonia to generate taurine; (3) Acidification and purification: After acidification of the taurine solution obtained in step (2), the solution is filtered through a membrane, concentrated, crystallized and dried to obtain the taurine product.

2. The method according to claim 1, characterized in that, The phase transfer catalyst is selected from one or more of quaternary ammonium salts, quaternary phosphorus salts, or polyethylene glycol; the amount of the phase transfer catalyst added is 0.5% to 5% of the mass of the sulfite.

3. The method according to claim 2, characterized in that, The quaternary ammonium salt is tetrabutylammonium bromide or hexadecyltrimethylammonium bromide; the polyethylene glycol is PEG-400 or PEG-600.

4. The method according to claim 1, characterized in that, The free radical inhibitor is one or more of copper sulfate, zinc sulfate, or their hydrates, and the amount of the free radical inhibitor added is 1% to 3% of the mass of the sulfite. Preferably, the free radical inhibitor is a combination of copper sulfate and zinc sulfate, wherein the amount of copper sulfate added is 1.2% of the mass of sulfite, and the amount of zinc sulfate added is 0.4% of the mass of sulfite.

5. The method according to claim 1, characterized in that, The sulfonation reaction is carried out at a temperature of 40-80°C, a pressure of 0.1-0.5 MPa, and a time of 1-4 hours.

6. The method according to claim 1, characterized in that, In the ammonolysis reaction, the molar ratio of ammonia to hydroxyethyl sulfonate is (5-15):1; the reaction temperature is 120-160°C; the reaction pressure is 1.0-3.0 MPa; and the reaction time is 2-6 hours.

7. The method according to claim 1, characterized in that, In step (3), the acidification is to adjust the pH of the solution to 3.5-4.5 using an inorganic acid.

8. The method according to claim 1, characterized in that, In step (3), the membrane filtration is microfiltration or ultrafiltration.

9. The method according to claim 1, characterized in that, The sulfite is sodium bisulfite or ammonium sulfite.

10. Taurine prepared by the method according to any one of claims 1-9.