Method for efficiently and circularly preparing taurine

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to a method for efficiently and circularly preparing taurine. The method comprises the steps of esterification, electrochemical sulfonation, hydrogen value-added utilization, multi-stage membrane separation and sulfuric acid circulation, and taurine crystallization and drying. In the esterification section, concentrated sulfuric acid is used for first operation, and after the system is stable, the concentrated sulfuric acid is replaced with recycled concentrated sulfuric acid to react with ethanolamine to generate esterification liquid; an IrO2 / Ti net electrode coated with a CeO2-MoO3 cocatalyst is adopted as an anode of the electrochemical sulfonation, a Pt / C electrode is adopted as a cathode of the electrochemical sulfonation, and a mixed solution containing taurine is generated; hydrogen generated by the cathode is divided into two paths which are respectively used for regenerating sodium sulfite and supplying power to the fuel cell; performing primary nanofiltration and secondary reverse osmosis treatment on the mixed solution to realize sulfuric acid circulation and water recovery; and finally crystallizing and drying to obtain taurine crystals, and partially circulating mother liquor.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to an efficient method for the cyclic preparation of taurine. Background Technology

[0002] Taurine, a sulfur-containing amino acid, plays a vital physiological role in the human and animal bodies. It participates in various physiological processes, including regulating nerve conduction, promoting brain development in infants and young children, maintaining visual function, regulating osmotic pressure, and enhancing immunity. For these reasons, taurine is widely used in food additives, pharmaceutical intermediates, and feed additives. In the food industry, it is often added to dairy products, beverages, and infant formula to enhance their nutritional value. In the pharmaceutical field, it can be used to prepare drugs for treating liver and gallbladder diseases, cardiovascular diseases, and other ailments.

[0003] With the continuous growth of market demand for taurine, research on its preparation methods has been a focus of industry attention. Currently, the main methods for preparing taurine include natural extraction and chemical synthesis. Natural extraction primarily extracts taurine from natural raw materials such as bovine bile; however, this method is limited by the availability of raw materials, resulting in low yields, complex extraction processes, and high costs, making it difficult to meet the needs of large-scale industrial production. Chemical synthesis generates numerous byproducts during the reaction process, leading to reduced product purity and making subsequent separation and purification difficult. Furthermore, the raw material ethylene oxide is highly toxic, flammable, and explosive, requiring sophisticated production equipment and operating conditions, posing certain safety hazards. Therefore, developing an efficient, environmentally friendly, low-cost taurine preparation method that enables material recycling is of significant practical importance for meeting market demand and promoting the sustainable development of the industry. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a highly efficient method for the cyclical preparation of taurine. This method includes an esterification stage, electrochemical sulfonation, hydrogen value-added utilization, multi-stage membrane separation and sulfuric acid recycling, and taurine crystallization and drying steps. In the esterification stage, concentrated sulfuric acid is used initially, and after system stabilization, it is replaced with recovered concentrated sulfuric acid, which reacts with ethanolamine to generate an esterification solution. Electrochemical sulfonation is carried out in a PEM electrolytic cell, with an IrO2 / Ti mesh electrode coated with a CeO2-MoO3 cocatalyst at the anode and a Pt / C electrode at the cathode, generating a mixture containing taurine. The hydrogen generated at the cathode is divided into two paths, used for regenerating sodium sulfite and powering a fuel cell, respectively. The mixture undergoes primary nanofiltration and secondary reverse osmosis treatment to achieve sulfuric acid recycling and water recovery. Finally, taurine is obtained through crystallization and drying, with part of the mother liquor recycled. This method, through the synergistic effect of each step, achieves low-temperature reaction, full material recycling, and energy self-sufficiency, reducing energy and material consumption and improving product purity and yield.

[0005] This invention provides a method for efficiently and cyclically preparing taurine, which specifically includes the following steps: S1, Esterification Section: Ethanolamine and concentrated sulfuric acid are added to the esterification reactor equipped with a stirring device at a molar ratio of 1:1.05. The reaction conditions are controlled as follows: Concentrated sulfuric acid is used during the first run. After the system is running stably, all sulfuric acid used is replaced with recovered concentrated sulfuric acid. The amount added is monitored and adjusted to maintain the molar ratio. The reaction temperature is controlled at 80-90℃ and the reaction is carried out for 2-3 hours to form an esterification liquid. Reaction equation: HOCH2CH2NH2 + H2SO4 → HOCH2CH2NH3 + HSO4 - +H2O; S2, Electrochemical Sulfonation: The esterification solution is fed into a PEM electrolytic cell for electrochemical sulfonation. The anode is an IrO2 / Ti mesh electrode coated with a co-catalyst, and the cathode is a Pt / C electrode. Deionized water is circulated through the cathode chamber, and the two chambers are separated by a perfluorosulfonic acid proton exchange membrane. The electrolysis parameters are set as follows: current density 300-400 A / m³. 2 The temperature is 40-50℃, the cell voltage is 1.8-2.2V, the reaction time is 2-3 h, hydrogen gas is generated at the cathode, and a mixture containing taurine, a small amount of sulfuric acid and reaction water is obtained at the anode. Anode reaction: HOCH2CH2NH3 + HSO4 - →H₂NCH₂CH₂SO₃H + H₂O + H + +2e - ; Cathode reaction (hydrogen evolution): 2H + +2e - →H2↑; S3, Hydrogen Value-Added Utilization: The hydrogen produced at the cathode in step S2 is cooled to 20°C and dehydrated by a cooler, then further purified by an activated carbon filter with a pore size of 0.1 μm, and finally divided into two equal streams for utilization by a flow meter: ①50% hydrogen is used to regenerate sodium sulfite: 20% sodium hydroxide solution and 10% nickel catalyst with a particle size of 3-5 mm are added to a stirred reactor. The nickel catalyst is loaded into a gas distributor in the reactor. SO2 gas and hydrogen are introduced and the temperature is controlled at 80℃ and atmospheric pressure. The reaction is carried out for 2 hours to generate sodium sulfite solution, which is then pumped to the raw material tank for chemical sulfonation and replenishment. Reaction equation: SO2 + H2 + 2NaOH → Na2SO3 + 2H2O; ② Another 50% of the hydrogen is used to power the fuel cell: A 5 kW proton exchange membrane fuel cell is used, equipped with a hydrogen buffer tank. The working pressure is 0.5 MPa. The hydrogen is reduced to 0.1 MPa before entering the proton exchange membrane fuel cell to generate electricity. The generated DC power is converted into 220V AC power by an inverter and directly fed back to the PEM electrolyzer, which can meet 30%-40% of the electrolyzer's power demand. S4, Multi-stage membrane separation and sulfuric acid circulation: The mixture undergoes primary nanofiltration separation using an acid-resistant nanofiltration membrane made of polyvinylidene fluoride with a molecular weight cutoff of 50-100 Da. The feed pump pressure is controlled at 0.6-0.8 MPa, the temperature at 30℃, and the feed flow rate at 100 L / h. This achieves the fractional separation of taurine and sulfuric acid in the mixture, yielding a permeate containing taurine and a retentate containing sulfuric acid, with a concentration factor of 5. The permeate is sent to an intermediate storage tank, while the retentate retained by the membrane is pumped into a secondary reverse osmosis system for concentration to obtain a concentrated solution with a sulfuric acid concentration ≥50%. This concentrated solution is then returned to the esterification section's raw material tank for recycling via an insulated pipeline. Simultaneously, permeate water is obtained and recycled. After treatment by an ion exchange column, the permeate water is reused as makeup water for the cathode chamber of the PEM electrolyzer or as dilution water for the esterification section. S5, Taurine Crystallization and Drying: A double-effect evaporator crystallizer is used with a vacuum of 0.08-0.09 MPa, a first-effect temperature of 70℃, and a second-effect temperature of 60℃. The permeate is pumped into the crystallizer and then transferred to a cooling crystallizer. The temperature is reduced to 10-15℃ at a rate of 5℃ / h, and the crystallizer is stirred for 4-6 hours to obtain the crystallized product. The product is then centrifuged for 10 minutes, washed, and wet crystals are obtained. The wet crystals are then vacuum dried for 3 hours to obtain taurine. 80-95% of the mother liquor generated during centrifugation is returned to the evaporator crystallizer for circulation, and 10% is pumped back to the esterification section to mix with the esterification liquid to avoid the accumulation of impurities.

[0006] Further, the co-catalyst is CeO2-MoO3, comprising the following raw materials in the following mass ratio: Ce(NO3)3·6H2O:(NH4)6Mo7O 24 ·4H₂O = 1-1.5:1; The preparation method of CeO2-MoO3 includes the following steps: i. React Ce(NO3)3·6H2O with (NH4)6Mo7O 24 ·4H2O dissolves in an ethanol-water mixture to form mixture A; ii. Add citric acid to mixture A, with a mass ratio of citric acid to mixture A of 1.5:1, and stir at 80°C to form a gel; iii. The gel was dried at 120°C to obtain a powder, and then the powder was calcined in air at 500°C for 2 h to obtain CeO2-MoO3.

[0007] Furthermore, the ratio of the ethanol-water mixture to Ce(NO3)3·6H2O is 1 g:10 mL, and the volume ratio of ethanol to water is 1:1.

[0008] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention presents a highly efficient and cyclical method for preparing taurine, achieving a comprehensive upgrade to the taurine preparation process. The combination of the esterification stage and the electrochemical sulfonation stage creates a significant energy-saving and consumption-reducing effect. Traditional processes require high-temperature sulfonation reactions, while this invention, with the aid of a co-catalyst-based electrochemical system, can complete the reaction at a mild temperature, significantly reducing energy consumption. Simultaneously, sulfuric acid is completely recycled through two-stage membrane separation, and reaction water can be efficiently recovered and reused, greatly reducing the input of fresh raw materials and lowering material costs from the source. In terms of environmental protection and safety, the combination of a hydrogen value-added system and membrane separation technology constructs a green closed loop. Part of the hydrogen generated at the cathode is used to regenerate the sodium sulfite required for the reaction, avoiding the emission of sulfide waste gas in traditional processes; the other part powers the system through a fuel cell, reducing dependence on purchased electricity and lowering carbon emissions. The zero emission of sulfuric acid and the ambient temperature and low-pressure reaction conditions not only significantly reduce the cost of treating waste gas, wastewater, and solid waste but also improve the safety level of the production process, achieving dual protection for environmental protection and safety. From an efficiency and economic perspective, the synergistic effect of the composite co-catalyst and the multi-stage separation system significantly improved the overall efficiency. The co-catalyst reduced the reaction overpotential, increased current efficiency, and shortened the sulfonation reaction time; the multi-stage separation and mother liquor recycling design improved the total yield of taurine. The interaction between each stage produced a breakthrough effect. The hydrogen generated by electrochemical sulfonation serves both as an energy recovery system and participates in raw material regeneration, forming a cycle of elements and energy; the sulfuric acid back-esterification chemical stage recovered by membrane separation achieves closed-loop utilization of raw materials. This cross-stage synergy enables the system to achieve optimal performance in terms of raw material input and energy self-sufficiency, far exceeding the effect of optimizing a single stage. This method reconstructs the taurine preparation pathway through multi-dimensional innovation, transforming byproducts into resources and turning disposable raw materials into recycling media. It not only improves the efficiency of taurine preparation but also constructs a green and low-carbon production paradigm that can be extended to the synthesis of other amino acids, providing a powerful reference for the sustainable development of the fine chemical industry. Attached Figure Description

[0009] Figure 1 This is a flowchart of the method for efficient cyclic preparation of taurine according to the present invention; Figure 2 This is a schematic diagram of the operation of the PEM electrolytic cell of the present invention. Detailed Implementation

[0010] To enable those skilled in the art to better understand the technical solutions of the present invention and to make the above-mentioned features, objectives, and advantages of the present invention clearer and easier to understand, the present invention will be further described below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0011] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0012] Unless otherwise specified, all methods described in the following embodiments are conventional. Unless otherwise specified, all materials used in the following embodiments are new materials purchased from the market.

[0013] according to Figure 1 The flowchart of the method for efficient cyclic preparation of taurine according to the present invention is illustrated in the following examples: Example 1: This example provides a method for the efficient recycling of taurine, which specifically includes the following steps: S1, Esterification reaction: Ethanolamine and concentrated sulfuric acid are added to an esterification reactor equipped with a stirrer at a molar ratio of 1:1.05. The reaction conditions are controlled as follows: Concentrated sulfuric acid is used during the first run. After the system is running stably, all sulfuric acid used is replaced with recovered concentrated sulfuric acid. The amount added is monitored and adjusted to maintain a molar ratio of ethanolamine to sulfuric acid of 1:1.05. The reaction temperature is controlled at 80 °C, the stirring rate is 300 r / min, and the reaction is carried out for 2-3 h to form an esterification liquid. Reaction equation: HOCH2CH2NH2 + H2SO4 → HOCH2CH2NH3 + HSO4 - +H2O; S2, Electrochemical Sulfonation: The esterification solution is fed into a PEM electrolytic cell for electrochemical sulfonation. The anode is an IrO2 / Ti mesh electrode coated with a co-catalyst, and the cathode is a Pt / C electrode. Deionized water is circulated through the cathode chamber, and the two chambers are separated by a perfluorosulfonic acid proton exchange membrane. The electrolysis parameters are set to a current density of 300 A / m². 2 The temperature was 40℃, the cell voltage was 1.8V, and the reaction time was 2 h until the conversion rate of 2-hydroxyethylamine sulfate in the anode chamber was ≥98%, resulting in a mixture containing taurine, a small amount of sulfuric acid and reaction water, and hydrogen was obtained at the cathode. Anode reaction: HOCH2CH2NH3 + HSO4 - →H₂NCH₂CH₂SO₃H + H₂O + H + +2e- ; Cathode reaction (hydrogen evolution): 2H + +2e - →H2↑; S3, Hydrogen Value-Added Utilization: The hydrogen generated at the cathode in step S2, with a flow rate of 10 L / min and a purity ≥99.9%, is cooled to 20℃ and dehydrated by a cooler. It then enters an activated carbon filter with a pore size of 0.1 μm for further impurity removal. Finally, it is divided into two streams by a flow meter and utilized in equal quantities. ①50% hydrogen is used to regenerate sodium sulfite: A stirred reactor with a gas distributor is used, with a built-in nickel catalyst with a loading of 10% and a particle size of 3 mm. 20% sodium hydroxide solution is added to the stirred reactor, and hydrogen and SO2 gas are introduced at a flow rate of 5 L / min. The temperature is controlled at 80 ℃ and the pressure is normal. The reaction is carried out for 2 h to generate sodium sulfite solution, which is pumped to the raw material tank for chemical sulfonation and supplementation. Reaction equation: SO2 + H2 + 2NaOH → Na2SO3 + 2H2O; ② Another 50% of the hydrogen is used to power the fuel cell: After being depressurized to 0.1 MPa, the hydrogen enters the 5 kW proton exchange membrane fuel cell to generate electricity. The power generation efficiency is ≥60%. It is equipped with a hydrogen buffer tank with a working pressure of 0.5 MPa. The generated DC power is converted into 220V AC power by an inverter and directly fed back to the PEM electrolyzer, which can meet 30%-40% of the electrolyzer's power demand. S4, Multistage Membrane Separation and Sulfuric Acid Circulation: The electrochemically sulfonated mixture undergoes primary nanofiltration separation. Four 8-inch acid-resistant nanofiltration membranes, made of polyvinylidene fluoride (PVDF), with a molecular weight cutoff of 50 Da, are used. The membranes have a rejection rate of 90% for sulfuric acid and 10% for taurine. They are arranged in series, with the feed pump pressure controlled at 0.6 MPa, the temperature at 30°C, and the feed flow rate at 100 mL / min. L / h, with a concentration factor of 5, yields permeate containing taurine and retentate containing sulfuric acid. The permeate enters an intermediate storage tank, while the retentate is pumped into a secondary reverse osmosis system. The secondary reverse osmosis system uses three 8-inch seawater desalination reverse osmosis membranes made of aromatic polyamide, acid-resistant type, operating at a pressure of 1.2-1.5 MPa and a temperature of 30℃. The system concentrates the permeate to obtain a sulfuric acid concentration ≥50%, which is then returned to the feed tank of the esterification section for recycling through a 50℃ insulated pipeline. Permeate water is also obtained and is recycled. After treatment by an ion exchange column, the permeate water is preferentially reused as makeup water in the cathode chamber of the PEM electrolyzer, with the remainder used as dilution water in the esterification section. S5, Taurine Crystallization and Drying: A double-effect evaporator crystallizer was used with a vacuum of 0.08 MPa, a first-effect temperature of 70℃, and a second-effect temperature of 60℃. The first-stage nanofiltration permeate was pumped into the crystallizer and then transferred to a cooling crystallization tank. The temperature was lowered to 10℃ at a rate of 5℃ / h, and the crystals were stirred and crystallized for 4 hours at a stirring rate of 100 r / min to obtain the crystalline product. Then, a flat plate centrifuge with a diameter of 1200 mm and a rotation speed of 3000 r / min was used for centrifugation for 10 min. The product was washed twice with deionized water to remove residual sulfuric acid on the surface, resulting in wet crystals. The wet crystals were placed in a vacuum drying oven with a temperature of 80℃ and a vacuum of 0.09 MPa and dried for 3 hours to obtain taurine. 80% of the mother liquor generated by centrifugation was returned to the double-effect evaporator crystallizer for recycling, and 10% was pumped back to the esterification section to mix with the esterification liquid to avoid the accumulation of impurities.

[0014] The co-catalyst is CeO2-MoO3, comprising the following raw materials in the following mass ratio: Ce(NO3)3·6H2O:(NH4)6Mo7O 24 ·4H2O=1:1; The preparation method of CeO2-MoO3 includes the following steps: i. React Ce(NO3)3·6H2O with (NH4)6Mo7O 24 ·4H2O, dissolved in an ethanol-water mixture, with the ratio of the ethanol-water mixture to Ce(NO3)3·6H2O being 1 g:10 mL, and the volume ratio of ethanol to water being 1:1, forming mixture A; ii. Add citric acid to mixture A, with a mass ratio of citric acid to mixture A of 1.5:1, and stir at 80°C to form a gel; iii. The gel was dried at 120°C to obtain a powder, which was then calcined at room temperature by heating to 500°C at a rate of 5°C / min and calcining at that temperature for 2 h to obtain CeO2-MoO3.

[0015] Example 2: This example provides a highly efficient method for the cyclic preparation of taurine, which specifically includes the following steps: S1, Esterification reaction: Ethanolamine and concentrated sulfuric acid are added to an esterification reactor equipped with a stirrer at a molar ratio of 1:1.05. The reaction conditions are controlled as follows: Concentrated sulfuric acid is used during the first run. After the system is running stably, all sulfuric acid used is replaced with recovered concentrated sulfuric acid. The amount added is monitored and adjusted to maintain a molar ratio of ethanolamine to sulfuric acid of 1:1.05. The reaction temperature is controlled at 90℃, the stirring rate is 300 r / min, and the reaction is carried out for 2.5 h to form an esterification liquid. Reaction equation: HOCH2CH2NH2 + H2SO4 → HOCH2CH2NH3 +HSO4 - +H2O; S2, Electrochemical Sulfonation: The esterification solution is fed into a PEM electrolytic cell for electrochemical sulfonation. The anode is an IrO2 / Ti mesh electrode coated with a co-catalyst, and the cathode is a Pt / C electrode. Deionized water is circulated through the cathode chamber, and the two chambers are separated by a perfluorosulfonic acid proton exchange membrane. The electrolysis parameters are set to a current density of 350 A / m². 2 The temperature was 45 ℃, the cell voltage was 2V, and the reaction time was 2.5 h until the conversion rate of 2-hydroxyethylamine sulfate in the anode chamber was ≥98%, resulting in a mixture containing taurine, a small amount of sulfuric acid and reaction water, and hydrogen gas was generated at the cathode. Anode reaction: HOCH2CH2NH3 + HSO4 - →H₂NCH₂CH₂SO₃H + H₂O + H + +2e - ; Cathode reaction (hydrogen evolution): 2H + +2e - →H2↑; S3, Hydrogen Value-Added Utilization: The hydrogen generated at the cathode in step S2, with a flow rate of 12 L / min and a purity ≥99.9%, is cooled to 20°C and dehydrated by a cooler. It then enters an activated carbon filter with a pore size of 0.1 μm for further impurity removal. Finally, it is divided into two streams by a flow meter and utilized in equal quantities. ①50% hydrogen is used to regenerate sodium sulfite: A stirred reactor with a gas distributor is used, with a built-in nickel catalyst with a loading of 10% and a particle size of 5 mm. 20% sodium hydroxide solution is added to the stirred reactor, and hydrogen and SO2 gas are introduced at a flow rate of 5 L / min. The temperature is controlled at 80℃ and the pressure is normal. The reaction is carried out for 2 hours to generate sodium sulfite solution, which is then pumped to the raw material tank for chemical sulfonation to supplement the use. Reaction equation: SO2 + H2 + 2NaOH → Na2SO3 + 2H2O; ② Another 50% of the hydrogen is used to power the fuel cell: After being depressurized to 0.1MPa, the hydrogen enters the 5 kW proton exchange membrane fuel cell to generate electricity. The power generation efficiency is ≥60%. It is equipped with a hydrogen buffer tank with a working pressure of 0.5MPa. The generated DC power is converted into 220V AC power by an inverter and directly fed back to the PEM electrolyzer, which can meet 30%-40% of the electrolyzer's power demand. S4, Multi-stage membrane separation and sulfuric acid circulation: The electrochemically sulfonated mixture undergoes primary nanofiltration separation: Four 8-inch acid-resistant nanofiltration membranes, made of polyvinylidene fluoride, with a molecular weight cutoff of 100 Da, are used. The rejection rates are 90% for sulfuric acid and 10% for taurine. They are arranged in series, with the feed pump pressure controlled at 0.8 MPa, the temperature at 30°C, the feed flow rate at 100 L / h, and the concentration factor at 5 times. This yields permeate containing taurine and retentate containing sulfuric acid. The permeate enters an intermediate storage tank, and the retentate is pumped into a secondary reverse osmosis system. The secondary reverse osmosis system uses three 8-inch seawater desalination reverse osmosis membranes, made of aromatic polyamide, acid-resistant, with an operating pressure of 1.5 MPa and a temperature of 30°C. This concentrate yields a sulfuric acid concentration ≥50%, which is returned to the esterification section feed tank for recycling through a 50°C insulated pipeline. Permeate water is also obtained and recycled. After treatment by an ion exchange column, the permeate water is preferentially reused as makeup water in the cathode chamber of the PEM electrolyzer, and the remainder is used for dilution water in the esterification section. S5, Taurine Crystallization and Drying: A double-effect evaporator crystallizer was used with a vacuum of 0.09 MPa, a first-effect temperature of 70℃, and a second-effect temperature of 60℃. The first-stage nanofiltration permeate was pumped into the crystallizer and then transferred to a cooling crystallization tank. The temperature was lowered to 12℃ at a rate of 5℃ / h, and the crystals were stirred and crystallized for 5 hours at a stirring rate of 100 r / min to obtain the crystalline product. Then, a flat plate centrifuge with a diameter of 1200 mm and a speed of 3000 r / min was used for centrifugation for 10 minutes. The product was washed twice with deionized water to remove residual sulfuric acid on the surface, resulting in wet crystals. The wet crystals were placed in a vacuum drying oven with a temperature of 80℃ and a vacuum of 0.09 MPa and dried for 3 hours to obtain taurine. 90% of the mother liquor generated by centrifugation was returned to the double-effect evaporator crystallizer for recycling, and 10% was pumped back to the esterification section to mix with the esterification liquid to avoid the accumulation of impurities.

[0016] The co-catalyst is CeO2-MoO3, comprising the following raw materials in the following mass ratio: Ce(NO3)3·6H2O:(NH4)6Mo7O 24 ·4H₂O = 1-1.2:1; The preparation method of CeO2-MoO3 includes the following steps: i. React Ce(NO3)3·6H2O with (NH4)6Mo7O 24 ·4H2O, dissolved in an ethanol-water mixture, with the ratio of the ethanol-water mixture to Ce(NO3)3·6H2O being 1 g:10 mL, and the volume ratio of ethanol to water being 1:1, forming mixture A; ii. Add citric acid to mixture A, with a mass ratio of citric acid to mixture A of 1.5:1, and stir at 80°C to form a gel; iii. The gel was dried at 120°C to obtain a powder, which was then calcined at room temperature by heating to 500°C at a rate of 5°C / min and calcining at that temperature for 2 h to obtain CeO2-MoO3.

[0017] Example 3: This example provides a highly efficient method for the cyclic preparation of taurine, which specifically includes the following steps: S1, Esterification reaction: Ethanolamine and concentrated sulfuric acid are added to an esterification reactor equipped with a stirrer at a molar ratio of 1:1.05. The reaction conditions are controlled as follows: Concentrated sulfuric acid is used during the first run. After the system is running stably, all sulfuric acid used is replaced with recovered concentrated sulfuric acid. The amount added is monitored and adjusted to maintain a molar ratio of ethanolamine to sulfuric acid of 1:1.05. The reaction temperature is controlled at 90℃, the stirring rate is 300 r / min, and the reaction is carried out for 2-3 h to form an esterification liquid. Reaction equation: HOCH2CH2NH2 + H2SO4 → HOCH2CH2NH3 + HSO4 - +H2O; S2, Electrochemical Sulfonation: The esterification solution is fed into a PEM electrolytic cell for electrochemical sulfonation. The anode is an IrO2 / Ti mesh electrode coated with a co-catalyst, and the cathode is a Pt / C electrode. Deionized water is circulated through the cathode chamber, and the two chambers are separated by a perfluorosulfonic acid proton exchange membrane. The electrolysis parameters are set to a current density of 400 A / m². 2 The temperature was 50℃, the cell voltage was 2.2V, and the reaction time was 3 h until the conversion rate of 2-hydroxyethylamine sulfate in the anode chamber was ≥98%, resulting in a mixture containing taurine, a small amount of sulfuric acid and reaction water, and hydrogen gas was generated at the cathode. Anode reaction: HOCH2CH2NH3 + HSO4 - →H₂NCH₂CH₂SO₃H + H₂O + H + +2e - Cathode reaction (hydrogen evolution): 2H + +2e - →H2↑; S3, Hydrogen Value-Added Utilization: The hydrogen generated at the cathode in step S2, with a flow rate of 15 L / min and a purity ≥99.9%, is cooled to 20°C and dehydrated by a cooler. It then enters an activated carbon filter with a pore size of 0.1 μm for further impurity removal. Finally, it is divided into two streams by a flow meter and utilized in equal quantities. ①50% hydrogen is used to regenerate sodium sulfite: A stirred reactor with a gas distributor is used, with a built-in nickel catalyst with a loading of 10% and a particle size of 5 mm. 20% sodium hydroxide solution is added to the stirred reactor, and hydrogen and SO2 gas are introduced at a flow rate of 5 L / min. The temperature is controlled at 80℃ and the pressure is normal. The reaction is carried out for 2 hours to generate sodium sulfite solution, which is then pumped to the raw material tank for chemical sulfonation to supplement the use. Reaction equation: SO2 + H2 + 2NaOH → Na2SO3 + 2H2O ② Another 50% of the hydrogen is used to power the fuel cell: After being depressurized to 0.1 MPa, the hydrogen enters the 5 kW proton exchange membrane fuel cell to generate electricity. The power generation efficiency is ≥60%. It is equipped with a hydrogen buffer tank with a working pressure of 0.5 MPa. The generated DC power is converted into 220 V AC power by an inverter and directly fed back to the PEM electrolyzer, which can meet 30%-40% of the electrolyzer's power demand. S4, Multistage Membrane Separation and Sulfuric Acid Circulation: The electrochemically sulfonated mixture undergoes primary nanofiltration separation. Four 8-inch acid-resistant nanofiltration membranes, made of polyvinylidene fluoride (PVDF), with a molecular weight cutoff of 100 Da, are used. The membranes have a rejection rate of 90% for sulfuric acid and 10% for taurine. They are arranged in series, with the feed pump pressure controlled at 0.8 MPa, the temperature at 30 °C, and the feed flow rate at 100 mL / min. L / h, with a concentration factor of 5, yields permeate containing taurine and retentate containing sulfuric acid. The permeate enters an intermediate storage tank, while the retentate is pumped into a secondary reverse osmosis system. The secondary reverse osmosis system uses three 8-inch seawater desalination reverse osmosis membranes made of aromatic polyamide, acid-resistant type, operating at a pressure of 1.5 MPa and a temperature of 30°C. The system concentrates the permeate to obtain a sulfuric acid concentration ≥50%, which is then returned to the feed tank of the esterification section for recycling through a 50°C insulated pipeline. Simultaneously, permeate water is obtained and recycled. After treatment by an ion exchange column, the permeate water is preferentially reused as makeup water in the cathode chamber of the PEM electrolyzer, with the remainder used as dilution water in the esterification section. S5, Taurine Crystallization and Drying: A double-effect evaporator crystallizer was used with a vacuum of 0.09 MPa, a first-effect temperature of 70℃, and a second-effect temperature of 60℃. The first-stage nanofiltration permeate was pumped into the crystallizer and then transferred to a cooling crystallization tank. The temperature was lowered to 15℃ at a rate of 5℃ / h, and the crystals were stirred and crystallized for 6 hours at a stirring rate of 100 r / min to obtain the crystalline product. Then, a flat plate centrifuge with a diameter of 1200 mm and a speed of 3000 r / min was used for centrifugation for 10 minutes. The product was washed twice with deionized water to remove residual sulfuric acid on the surface, resulting in wet crystals. The wet crystals were placed in a vacuum drying oven with a temperature of 80℃ and a vacuum of 0.09 MPa and dried for 3 hours to obtain taurine. 95% of the mother liquor generated by centrifugation was returned to the evaporator crystallizer for circulation, and 10% was pumped back to the esterification section to mix with the esterification liquid to avoid the accumulation of impurities.

[0018] The co-catalyst is CeO2-MoO3, comprising the following raw materials in the following mass ratio: Ce(NO3)3·6H2O:(NH4)6Mo7O 24 ·4H2O=1.5:1; The preparation method of CeO2-MoO3 includes the following steps: i. React Ce(NO3)3·6H2O with (NH4)6Mo7O 24 ·4H2O, dissolved in an ethanol-water mixture, with the ratio of the ethanol-water mixture to Ce(NO3)3·6H2O being 1 g:10 mL, and the volume ratio of ethanol to water being 1:1, forming mixture A; ii. Add citric acid to mixture A, with a mass ratio of citric acid to mixture A of 1.5:1, and stir at 80°C to form a gel; iii. The gel was dried at 120°C to obtain a powder, which was then calcined at room temperature by heating to 500°C at a rate of 5°C / min and calcining at that temperature for 2 h to obtain CeO2-MoO3.

[0019] The difference between Comparative Example 1 and Example 2 is that the sulfonation was carried out at 200 °C at high temperature; the rest of the process was exactly the same as in Example 2.

[0020] The difference between Comparative Example 2 and Example 2 is that the co-catalyst was omitted; otherwise, they are exactly the same as Example 2.

[0021] The difference between Comparative Example 3 and Example 2 is that the mother liquor is discharged directly, while the rest is exactly the same as in Example 2.

[0022] Experimental example: 1. Taurine Purity Test: Taurine prepared using the efficient cyclic taurine preparation method of Examples 1-3 and Comparative Examples 1-3 of this invention was used as the sample. An appropriate amount of sample was weighed and dissolved in ultrapure water to a final volume. HPLC was used for detection: a Discovery C18 column was used, the mobile phase was 0.1% phosphoric acid aqueous solution (pH 2.5), the flow rate was 1.0 mL / min, the detection wavelength was 210 nm, and the determination was performed at room temperature. An external standard method was used, and a standard curve was plotted with taurine standard (purity ≥ 99.9%) to calculate the sample purity. The purity of taurine was calculated using the following formula: Purity (%) = (A... 样品 / A 标准品 ×C 标准品 / C 样品 () × 100%, where A is the peak area and C is the concentration. The results are recorded in Table 1.

[0023] 2. Overall Yield Test: Calculate the overall conversion efficiency from raw material ethanolamine to the final taurine product; accurately weigh the initial mass of ethanolamine m0, the molar ratio of taurine (M=125.15g / mol) to ethanolamine (M=61.08g / mol) is 1:1, and the theoretical constant is: m 理论 =m0×125.15 / 61.08, actual yield determination, collect the dried taurine product and weigh it as m. 实际 Total yield (%) = (m 实际 / m 理论 () × 100%, and the results are recorded in Table 1.

[0024] 3. Water reuse rate test: The water reuse rate was tested using the efficient recycling method for taurine preparation in Examples 1-3 and Comparative Examples 1-3 of this invention. The conductivity of the recycled water was measured using a conductivity meter, and the instrument was calibrated before the measurement. Water recovery rate calculation: The amount of water to be treated and the amount of water recovered were recorded. The water reuse rate (%) was calculated as follows: Water recovery rate (%) = Recovered water volume / Total water consumption × 100%. The results are recorded in Table 1.

[0025] 4. Sulfuric Acid Circulation Efficiency Test: The efficient circulation method for preparing taurine using Examples 1-3 and Comparative Examples 1-3 of this invention was tested. Following GB / T11198.1-1989, acid-base titration was performed using a standard sodium hydroxide solution to calculate the concentration of concentrated sulfuric acid. The amount of concentrated sulfuric acid input and loss during the production cycle was recorded. Circulating sulfuric acid was input into the esterification section, and after 10 cycles, the esterification reaction efficiency was tested. Circulation efficiency (%) = Input - Loss / Input × 100%. The results are recorded in Table 1.

[0026] Table 1

[0027] Table 1 shows the results. The taurine prepared in Examples 1-3 maintained a stable purity of 99.4%-99.6%, a total yield of 95%-97%, a water reuse rate of 94%-96%, and a recycling efficiency of 97%-99%. All indicators were at a high level, demonstrating the stability and superiority of this process in terms of product purity, resource recycling, and production efficiency. In Comparative Example 1, the use of 200℃ high-temperature sulfonation instead of electrochemical sulfonation resulted in a decrease in taurine purity to 98.8%, a sharp drop in water reuse rate from 96% to 30%, and a recycling efficiency of 0. This indicates that room-temperature electrochemical sulfonation is crucial for ensuring product quality, yield, and resource recycling. High-temperature processes not only consume a lot of energy but also damage the water recycling system, leading to ineffective sulfuric acid recovery. The addition of a co-catalyst significantly improved the total yield, indicating that the CeO2-MoO3 composite co-catalyst is crucial for improving reaction efficiency. By reducing overpotential and increasing current efficiency, it directly promotes raw material conversion and product formation.

[0028] Figure 2This is a schematic diagram of a PEM electrolyzer. The anode uses an IrO2 / Ti mesh electrode coated with a CeO2-MoO3 cocatalyst to meet the requirements of the electrochemical sulfonation reaction. The cathode uses a Pt / C electrode to facilitate the hydrogen evolution reaction.

[0029] In summary, the closed-loop process based on membrane separation-electrochemical coupling provided by this invention achieves efficient cyclic preparation of taurine through the organic combination of steps such as esterification, electrochemical sulfonation, hydrogen value-added utilization, multi-stage membrane separation and sulfuric acid recycling, and taurine crystallization and drying. The application of the CeO2-MoO3 composite cocatalyst effectively improves the efficiency of electrochemical sulfonation, room-temperature electrochemical sulfonation significantly reduces energy consumption by replacing high-temperature sulfonation, and the multi-stage membrane separation and mother liquor recycling design achieves efficient recovery of sulfuric acid and water resources. The synergistic effect of electrochemical sulfonation, composite cocatalyst, and mother liquor recycling in this invention not only ensures product quality and yield but also achieves efficient resource recycling, reducing energy consumption and environmental costs. It provides a scalable process paradigm for the green and low-carbon production of taurine and other amino acids, demonstrating significant technological innovation and economic value.

[0030] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for efficiently preparing taurine in a cyclic manner, characterized in that, Specifically, the following steps are included: S1, Esterification Section: Ethanolamine and concentrated sulfuric acid are added to the esterification reactor, the reaction conditions are controlled, the esterification reaction is carried out, and the esterification liquid is formed. S2, Electrochemical sulfonation: The esterification solution is fed into the anode chamber of the PEM electrolytic cell, and deionized water is introduced into the cathode chamber to carry out electrochemical sulfonation. Hydrogen gas is generated at the cathode, and a mixed solution is obtained at the anode. S3, Hydrogen Value-Added Utilization: The hydrogen produced at the cathode in step S2 is processed and then divided into two uses: 50% of the hydrogen is used to regenerate sodium sulfite; the other 50% of the hydrogen is used to power the fuel cell. S4, Multi-stage membrane separation and sulfuric acid recycling: The mixture is separated by a first-stage nanofiltration to obtain a permeate containing taurine and a retentate containing sulfuric acid. The retentate is concentrated by a second-stage reverse osmosis to obtain concentrated sulfuric acid, which is returned to the esterification section for recycling. At the same time, permeate water is generated. The permeate water is treated by ion exchange and then reused in the cathode chamber of the PEM electrolyzer or the esterification section. S5, Taurine Crystallization and Drying: The permeate containing taurine is evaporated and concentrated, cooled and crystallized to obtain a crystalline product. The crystalline product is centrifuged and vacuum dried to obtain taurine. The mother liquor generated during centrifugation is returned to the evaporation and concentration process for recycling.

2. The method for efficient recycling of taurine according to claim 1, characterized in that, In step S1, the molar ratio of ethanolamine to concentrated sulfuric acid is 1:1.05; the reaction conditions are as follows: concentrated sulfuric acid is used during the first run, and after the system is running stably, all the sulfuric acid used is replaced with recovered concentrated sulfuric acid, the reaction temperature is controlled at 80-90℃, and the reaction time is 2-3 h.

3. The method for efficient cyclic preparation of taurine according to claim 1, characterized in that, In step S2, the parameters for the electrochemical sulfonation are a current density of 300-400 A / m. 2 Temperature 40-50℃, cell voltage 1.8-2.2V, reaction time 2-3h.

4. The method for efficient cyclic preparation of taurine according to claim 1, characterized in that, In step S2, in the PEM electrolytic cell, the anode is an IrO2 / Ti mesh electrode coated with a co-catalyst, and the cathode is a Pt / C electrode; the co-catalyst is CeO2-MoO3, comprising the following raw materials in the following mass ratio: Ce(NO3)3·6H2O:(NH4)6Mo7O 24 ·4H₂O = 1-1.5:1; The preparation method of CeO2-MoO3 includes the following steps: i. React Ce(NO3)3·6H2O with (NH4)6Mo7O 24 ·4H2O dissolves in an ethanol-water mixture to form mixture A; ii. Add citric acid to mixture A and stir to form a gel; iii. The gel is dried to obtain a powder, and then the powder is calcined to obtain CeO2-MoO3.

5. The method for efficient recycling of taurine according to claim 4, characterized in that, In step i, the ratio of the amount of ethanol-water mixture to Ce(NO3)3·6H2O is 1 g:10 mL, and the volume ratio of ethanol to water is 1:1; in step ii, the mass ratio of citric acid to mixture A is 1.5:

1.

6. The method for efficient recycling of taurine according to claim 1, characterized in that, In step S4, the primary nanofiltration uses an acid-resistant nanofiltration membrane made of polyvinylidene fluoride with a molecular weight cutoff of 50-100 Da, an operating pressure of 0.6-0.8 MPa, and a temperature of 30°C; the secondary reverse osmosis concentration operates at an operating pressure of 1.2-1.5 MPa and a temperature of 30°C.

7. The method for efficient recycling of taurine according to claim 1, characterized in that, In step S5, the vacuum degree of the evaporation and concentration is 0.08-0.09 MPa; the cooling and crystallization temperature is 10-15°C; and the mother liquor recycling ratio is 80-95%.

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