Synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate

Abstract

The present invention relates to the technical field of organic synthesis, and specifically relates to a synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate, which includes Step 1: Dissolve MOPSO in process water to form a mixed solution, and heat it up to obtain a reaction solution; Step 2: Under an inert gas, dropwise add a sodium ion lye to the reaction solution, and then keep the temperature for reaction; Step 3: Control the pH value of the reaction system and continue to keep the temperature for reaction; Step 4: After filtration, cool down and centrifuge to obtain a crude product of MOPSO-Na; Step 5: Keep the temperature for decolorization to obtain a decolorized solution; Step 6: After filtering the decolorized solution, add a solvent, cool down to crystallize, centrifuge and dry to obtain the MOPSO-Na product; Step 7: After centrifugal concentration, cool down to crystallize; both the distilled solvent and the precipitated crystals can be recycled. The preparation process disclosed by the present invention is simple, can avoid the discharge of impurities and by-products caused by externally added auxiliaries, and is easy to realize the recycling of MOPSO.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and particularly relates to a synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate. Background Art

[0002] Sodium 3-(N-morpholino)-2-hydroxypropanesulfonate (MOPSO-Na) is an amphoteric ionic amino sulfonate biological buffer with a pH buffering range of 6.2 - 7.6 and a pKa (25°C) of 6.9, and can be applied in the following fields: (1) in vitro diagnosis: biochemical diagnostic kits, DNA / RNA extraction kits, and PCR diagnostic kits; (2) protein / nucleic acid separation and purification: separation in nucleic acid and protein electrophoresis, denaturing gel electrophoresis of RNA1, and protein purification in chromatography; (3) cell culture medium: the buffering system of the culture medium; (4) biosynthesis: used as a buffer in biosynthesis; (5) measuring absorption in ultraviolet / visible spectrophotometry and studying redox properties using cyclic voltammetry.

[0003] In the prior art, the preparation of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate mainly uses morpholine as the starting material. First, morpholine and an acid are reacted under an inert gas condition to generate 3-(N-morpholino) ionic liquid, and then the 3-(N-morpholino) ionic liquid is reacted with sodium bisulfite under the action of a catalyst to generate 3-(N-morpholino) sodium salt. When the obtained 3-(N-morpholino) sodium salt passes through a cation exchange resin column, an ion exchange reaction occurs between the 3-(N-morpholino) sodium salt and the resin to generate 3-(N-morpholino) propanesulfonic acid sodium salt. Under the action of a positioning agent, SO3 gas is introduced into the 3-(N-morpholino) propanesulfonic acid sodium salt at 100°C - 120°C to obtain the crude product of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate, and the crude product is refined to the finished product MOPSO-Na in an aqueous glycerol solution. This synthesis method of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate has the following problems: 1. The preparation process is cumbersome and complex, time-consuming, and the production efficiency is low; 2. There are many types of intermediate products, which not only easily introduce impurities but also are not conducive to the recycling of raw materials or intermediate products. Summary of the Invention

[0004] Aiming at the technical problems of low production efficiency of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate and difficult recycling of raw materials in the prior art, the present invention provides a synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate, which shortens the synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate and realizes the recycling of 3-(N-morpholino)-2-hydroxypropanesulfonic acid.

[0005] The technical solution of the present invention is as follows:

[0006] A synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate, and the reaction route is as follows:

[0007]

[0008] It includes the following steps:

[0009] Step 1: Dissolve 3-(N-morpholino)-2-hydroxypropanesulfonic acid (MOPSO) in process water to form a mixed solution. Under stirring, heat the mixed solution to 40 - 80 °C. After the MOPSO in the mixed solution is dissolved and clarified, keep stirring at a constant temperature for 15 - 30 min to obtain a reaction solution.

[0010] Step 2: Under the protection of an inert gas, add sodium ion lye dropwise to the reaction solution obtained in Step 1, control the temperature of the reaction system for reflux reaction to make the liquid in the reaction system show a slight reflux state, measure the pH value of the reaction system. When the pH value of the reaction system reaches the range of 7.8 - 8.5, stop adding sodium ion lye, and keep the reaction at a constant temperature for 20 - 40 min.

[0011] Step 3: After the reaction at a constant temperature ends, control the pH value of the reaction system to remain within the range of 7.8 - 8.5. When the pH of the reaction system is lower than 7.8, continue to add sodium ion lye to the reaction system until the pH of the reaction system reaches the range of 7.8 - 8.5 to increase the reaction rate of H + in the reaction system, and continue to keep the reaction at a constant temperature for 2 - 2.5 h to obtain a product solution.

[0012] Step 4: After the product solution obtained in Step 3 is filtered through a filter membrane, cool it to 5 - 10 °C and centrifuge to obtain the crude MOPSO-Na. The product solution is filtered through a filter membrane to separate insoluble impurities, and the insoluble impurities include but are not limited to solid bases precipitated from excessive sodium ion lye.

[0013] Step 5: Mix process water with the crude MOPSO-Na and heat it to 60 - 65 °C. After the crude MOPSO-Na is completely dissolved in process water, evenly disperse activated carbon in the process water solution of the crude MOPSO-Na, and keep the color removed at a constant temperature to obtain a decolorized solution. The activated carbon is preferably coconut shell activated carbon.

[0014] Step 6: After the decolorized solution obtained in Step 5 is precisely filtered, add a solvent, and perform stepwise cooling on the decolorized solution after adding the solvent. After cooling, keep the temperature constant for crystal precipitation, centrifuge and dry to obtain the MOPSO-Na product.

[0015] Step 7: Distill and concentrate the upper layer liquid obtained by centrifugation in Step 6, and then cool it to 5 - 10 °C for crystal precipitation; recover the distilled solvent and reuse it in Step 6 of the next round of synthesis, and recover the crystals precipitated by cooling and reuse them in Step 1 of the next round of synthesis.

[0016] Furthermore, the process water is pure water or deionized water.

[0017] Furthermore, the mass ratio of 3-(N-morpholino)-2-hydroxypropanesulfonic acid to process water in Step 1 is 1-3:1.

[0018] Furthermore, the inert gas in Step 2 includes any one of helium, neon, argon, krypton, and xenon.

[0019] Furthermore, the sodium ion lye includes aqueous sodium hydroxide solution, aqueous sodium bicarbonate solution, or aqueous sodium carbonate solution, preferably aqueous sodium hydroxide solution. The mass fraction of sodium hydroxide in the aqueous sodium hydroxide solution is 33%-50%. When the concentration of sodium hydroxide is lower than 33%, the reaction efficiency is relatively low, and the subsequent purification and purification workload is relatively large; when the concentration of sodium hydroxide is higher than 50%, sodium hydroxide is likely to precipitate during the reaction, which is not conducive to the progress of the reaction.

[0020] Furthermore, the temperature of the reaction system in Step 2 is 80-85°C. When the temperature of the reaction solution reaches 80°C, visible condensate droplets begin to appear in the reaction vessel; when the temperature of the reaction solution exceeds 85°C, the process water evaporates too quickly, which is not conducive to the progress of the reaction.

[0021] Furthermore, the temperature of the heat preservation reaction in Step 2 is 80-85°C.

[0022] Furthermore, the mass fraction of activated carbon in Step 5 is 0.5%. The mass fraction of activated carbon is the percentage of the mass of activated carbon to the crude MOPSO-Na.

[0023] Furthermore, the solvent in Step 6 includes any one of methanol, ethanol, and isopropanol, preferably ethanol. Ethanol is non-toxic and does not pose a threat to the environment and the health of operating workers, which is conducive to green production; the stepwise cooling in Step 6 is to first cool down to 20-30°C with cooling water and then slowly cool down to 5-10°C with a refrigerant; the temperature of heat preservation and crystallization is 5-10°C.

[0024] Furthermore, the precision filtration in Step 6 is to filter with a filter element with a pore size of 0.22-0.45 μm, and the pore size is preferably 0.22 μm. Precision filtration can separate coconut shell activated carbon.

[0025] The beneficial effects of the present invention are as follows:

[0026] First aspect, a synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate provided by the present invention uses MOPSO as the starting material. The MOPSO molecular structure contains a hydroxyl group with strong activity and a hydrophilic sulfonic acid group, and has a high solubility in process water. Dissolving MOPSO in process water is beneficial to improving the reaction efficiency. Heating the mixed solution to 40 - 80 °C with stirring can promote the dissolution of MOPSO in process water, and helps with the ionization of H + in MOPSO structure and the discharge of oxygen in process water.

[0027] Second aspect, dropping sodium ion lye under inert gas protection in the present invention can reduce the occurrence of side reactions and prevent MOPSO from reacting with oxygen during the reflux reaction process.

[0028] Third aspect, by cooling the product solution to 5 - 10 °C in the present invention, the solubility of MOPSO-Na in the product solution is reduced. After cooling, under the action of centrifugation, MOPSO-Na is more easily separated, and the recovery rate is relatively high.

[0029] Fourth aspect, the main reason for using activated carbon for decolorization in the present invention is that the activated carbon has a large specific surface area and can effectively adsorb insoluble impurities in the crude MOPSO-Na. Coconut shell activated carbon has the advantages of developed pores, can be regenerated multiple times after saturation, is economical and durable, and has low resistance.

[0030] Fifth aspect, the present invention conducts precision filtration on the decolorized solution to separate the activated carbon. When the activated carbon deposits at the filter element, it is beneficial to assist the filter element in intercepting fine impurities.

[0031] Sixth aspect, the solvents and reaction starting materials used in the present invention can all be recycled and reused, which is beneficial to saving costs, reducing raw material losses, and increasing the yield of finished products.

[0032] In summary, the present invention prepares the crude MOPSO-Na by dropping sodium ion lye into the MOPSO process aqueous solution; separates the impurities in the crude MOPSO-Na by sequentially using precision filtration and heat preservation decolorization with powdered activated carbon, and controls the temperature change for crystallization to further purify the MOPSO-Na product. The preparation process is simple. Only powdered activated carbon that is easy to separate and reuse is used in the process of separating impurities and purification, which can effectively avoid the discharge of impurities and by-products caused by introducing external additives, is easy to realize the recycling of MOPSO, increases the yield of the MOPSO-Na product, and meets the requirements of green environmental protection. Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is the infrared spectrogram of the MOPSO-Na product prepared in Example 1. Specific embodiments

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0036] Example 1

[0037] A synthesis process of 3-(N-morpholino)-2-hydroxypropanesulfonic acid sodium salt, comprising the following steps:

[0038] Step 1: Dissolve 200 g of MOPSO in 130 g of pure water in a 1 L three-necked flask to form a mixed solution. Under stirring, heat the mixed solution to 80 °C. After the MOPSO in the mixed solution is dissolved and clarified, keep stirring at a constant temperature for 20 min to obtain a reaction solution.

[0039] Step 2: Under argon protection, add 80 g of a 50% sodium carbonate aqueous solution dropwise to the reaction solution obtained in Step 1. The dropping time of the sodium carbonate aqueous solution is controlled within 1 - 2 h, and the temperature of the reaction system is controlled at 80 °C for reflux reaction to make the liquid in the reaction system show a slight reflux state. Monitor the pH value of the reaction system during the dropping of the sodium carbonate aqueous solution. After the dropping of the sodium carbonate aqueous solution is completed, the measured pH value of the reaction system is 8.3, and keep the reaction at a constant temperature of 80 °C for 30 min.

[0040] Step 3: After the constant-temperature reaction is completed, measure the pH value of the reaction system again. The pH value of the reaction system is 8.3. Continue to keep the reaction at a constant temperature of 80 °C for 2 h to obtain a product solution.

[0041] Step 4: The product solution obtained in Step 3 is filtered through a common filter membrane and then enters a cooling crystallization kettle, cooled to 7 °C, and centrifuged to obtain 210 g of crude MOPSO-Na.

[0042] Step 5: Add 105 g of process water and 210 g of crude MOPSO-Na obtained in Step 4 into a refining dissolution kettle for mixing and heat up to 60°C. After the crude MOPSO-Na is completely dissolved in the process water, disperse 0.5% (by mass) of coconut shell activated carbon evenly in the crude MOPSO-Na process aqueous solution, and keep it warm for decolorization at 60°C for 1 h to obtain a decolorized solution. Here, the mass fraction of activated carbon is the percentage of the mass of activated carbon to the crude MOPSO-Na.

[0043] Step 6: The decolorized solution obtained in Step 5 is precisely filtered through a filter with a pore size of 0.22 μm and then enters a crystallization kettle. Add 210 g of ethanol to the crystallization kettle. First, cool it to 25°C with cooling water, and then slowly cool it to 10°C with refrigerant. After cooling, keep it warm for crystal precipitation at 10°C for 2 h, and centrifuge to obtain 182 g of wet product, dry it at 50°C for 4 h, and obtain 175.2 g of MOPSO-Na product after drying. The infrared spectrum of the MOPSO-Na product is as Figure 1 shown. The content determined by potentiometric titration is 99.68%, and the yield is 80.0%. Ultraviolet (5% aqueous solution): 260 nm: 0.015; 280 nm: 0.010; pH (1% aqueous solution): 9.32.

[0044] Step 7: Distill and concentrate the upper-layer liquid obtained by centrifugation in Step 6, and then cool it to 6°C for crystal precipitation. Recover 10.5 g of the remaining MOPSO, and the distilled ethanol can be put into the next kettle for refining. A total of 184.7 g of MOPSO-Na is prepared, and the comprehensive yield is 84.7%.

[0045] Example 2

[0046] A synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate includes the following steps:

[0047] Step 1: Dissolve 200 g of MOPSO in 130 g of pure water in a 1-L three-necked flask to form a mixed solution. Under stirring, heat up the mixed solution to 80°C. After the MOPSO in the mixed solution is dissolved and clarified, keep it warm and stir for 20 min to obtain a reaction solution.

[0048] Step 2: Under argon protection, add 100 g of a 33% (by mass) aqueous sodium hydroxide solution dropwise to the reaction solution obtained in Step 1. The dropping time of the aqueous sodium hydroxide solution is controlled within 1 - 2 h, and the temperature of the reaction system is controlled at 85°C for reflux reaction to make the liquid in the reaction system show a slight reflux state. Monitor the pH value of the reaction system during the dropping of the aqueous sodium hydroxide solution. After the dropping of the aqueous sodium hydroxide solution is completed, the measured pH value of the reaction system is 7.9, and keep it warm for reaction at 85°C for 30 min.

[0049] Step 3: After the heat preservation reaction ended, measure the pH value of the reaction system again, which was 7.9. Continue the heat preservation reaction at 85 °C for 2 h to obtain the product solution.

[0050] Step 4: The product solution obtained in Step 3 was filtered through a common filter membrane and then entered the cooling crystallization kettle. It was cooled to 10 °C and centrifuged to obtain 224 g of crude MOPSO-Na.

[0051] Step 5: Add 112 g of process water and 224 g of the crude MOPSO-Na obtained in Step 4 to the refining dissolution kettle for mixing and heat up to 65 °C. After the crude MOPSO-Na was completely dissolved in the process water, 0.5% powdered coconut shell activated carbon by mass was evenly dispersed in the crude MOPSO-Na process aqueous solution, and heat preservation and decolorization were carried out at 65 °C for 1 h to obtain the decolorized solution. Herein, the mass fraction of activated carbon is the percentage of the mass of activated carbon to the crude MOPSO-Na.

[0052] Step 6: The decolorized solution obtained in Step 5 was precisely filtered through a filter element with a pore size of 0.22 μm and then entered the crystallization kettle. Add 224 g of ethanol to the crystallization kettle. First, cool it to 20 °C with cooling water, and then slowly cool it to 5 °C with refrigerant. After cooling, carry out heat preservation and crystal precipitation at 5 °C for 2 h, and centrifuge to obtain 182 g of wet product, and dry it at 50 °C for 4 h to obtain 185.5 g of MOPSO-Na product. The content by potentiometric titration was 99.40%, and the yield was 84.7%. Ultraviolet (5% aqueous solution): 260 nm: 0.017; 280 nm: 0.012; pH (1% aqueous solution): 9.35.

[0053] Step 7: Distill and concentrate the upper liquid obtained by centrifugation in Step 6, and then cool it to 5 °C for crystal precipitation. Recover the remaining 8.0 g of MOPSO, and the distilled ethanol can be put into the next kettle for refining. A total of 193.5 g of MOPSO-Na was prepared, and the comprehensive yield was 88.35%.

[0054] Example 3

[0055] This example provides a synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate, including the following steps:

[0056] Step 1: Dissolve 10.0 kg of MOPSO in 6.5 kg of pure water in a 50 L three-necked flask to form a mixed solution. Under stirring, heat up the mixed solution to 80 °C. After the MOPSO in the mixed solution was dissolved and clarified, keep stirring for 30 min to obtain the reaction solution.

[0057] Step 2: Under argon protection, 5.0 kg of 33% sodium hydroxide aqueous solution was added dropwise to the reaction solution obtained in Step 1. The dropping time of the sodium hydroxide aqueous solution was controlled within 1 - 2 h, and the temperature of the reaction system was controlled at 83 °C for reflux reaction to make the liquid in the reaction system show a slight reflux state. After the addition of the sodium hydroxide aqueous solution was completed, the pH value of the reaction system was measured to be 8.0, and the reaction was kept at 83 °C for 30 min for heat preservation reaction.

[0058] Step 3: After the heat preservation reaction ended, the pH value of the reaction system was measured again to be 8.0, and the reaction was continued to be kept at 83 °C for 2 h to obtain the product solution.

[0059] Step 4: The product solution obtained in Step 3 was filtered through a common filter membrane and then entered the cooling crystallization kettle, cooled to 8 °C, and centrifuged to obtain 10.5 kg of crude MOPSO-Na.

[0060] Step 5: 5.25 kg of process water and 10.5 kg of crude MOPSO-Na obtained in Step 4 were added to the refining dissolution kettle for mixing and heated to 65 °C. After the crude MOPSO-Na was completely dissolved in the process water, 0.5% coconut shell activated carbon by mass was evenly dispersed in the crude MOPSO-Na process aqueous solution, and the mixture was kept at 65 °C for 1 h for decolorization to obtain the decolorized solution. Herein, the mass fraction of activated carbon is the percentage of the mass of activated carbon to the crude MOPSO-Na.

[0061] Step 6: The decolorized solution obtained in Step 5 was precisely filtered through a filter element with a pore size of 0.22 μm and then entered the crystallization kettle. 10.5 kg of methanol was added to the crystallization kettle. First, it was cooled to 22 °C with cooling water, and then slowly cooled to 8 °C with refrigerant. After cooling, it was kept at 8 °C for 2 h for crystal precipitation, and then centrifuged to obtain 9.47 kg of wet product, which was dried at 50 °C for 4 h to obtain 9.1 kg of MOPSO-Na product. The content by potentiometric titration was 99.50%, and the yield was 83.1%. UV (5% aqueous solution): 260 nm: 0.016; 280 nm: 0.008; pH (1% aqueous solution): 9.52.

[0062] Step 7: The upper-layer liquid obtained by centrifugation in Step 6 was distilled and concentrated, and then cooled to 8 °C for crystal precipitation. 510 g of the remaining MOPSO was recovered, and the distilled methanol could be put into the next kettle for refining. A total of 9.61 kg of MOPSO-Na was prepared, and the comprehensive yield was 87.76%.

[0063] Although the present invention has been described in detail by referring to the accompanying drawings and in conjunction with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily conceive of changes or substitutions, and they should all be covered within the protection scope of the present invention.

Claims

1. A synthetic process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate, characterized in that, It includes the following steps: Step 1: Dissolve 3-(N-morpholino)-2-hydroxypropanesulfonic acid in process water to form a mixed solution. Under stirring, heat the mixed solution to 40 - 80 °C. After the mixed solution becomes clear, keep it warm and stir for 15 - 30 min to obtain a reaction solution; Step 2: Under the protection of an inert gas, dropwise add a sodium ion alkaline solution to the reaction solution obtained in Step 1, control the temperature of the reaction system for reflux reaction, measure the pH value of the reaction system. When the pH value of the reaction system reaches the range of 7.8 - 8.5, stop dropping the sodium ion alkaline solution, and keep the reaction warm for 20 - 40 min; Step 3: After the end of the heat preservation reaction, control the pH value of the reaction system to remain in the range of 7.8 - 8.5, and continue to keep the reaction warm for 2 - 2.5 h to obtain a product solution; Step 4: After the product solution obtained in Step 3 is filtered through a filter membrane, cool it down to 5 - 10 °C and centrifuge to obtain the crude MOPSO-Na; Step 5: Mix process water with the crude MOPSO-Na and heat it up to 60 - 65 °C. After the crude MOPSO-Na is completely dissolved in the process water, add activated carbon, keep it warm for decolorization to obtain a decolorized solution; Step 6: After the decolorized solution obtained in Step 5 is precisely filtered, add a solvent, and perform stepwise cooling on the decolorized solution after adding the solvent. After cooling, keep it warm for crystallization, and after centrifuging and drying, obtain the MOPSO-Na product; Step 7: Distill and concentrate the upper layer liquid obtained by centrifuging in Step 6, and then cool it down for crystallization; Recover the distilled solvent and use it again in Step 6, and recover the crystals precipitated by cooling and use them again in Step 1; The sodium ion alkaline solution includes an aqueous sodium hydroxide solution, an aqueous sodium bicarbonate solution, or an aqueous sodium carbonate solution; The temperature of the reaction system in Step 2 is 80 - 85 °C; The temperature of the heat preservation reaction in Step 2 is 80 - 85 °C.

2. The synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate according to claim 1, characterized in that, The process water is pure water or deionized water.

3. The synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate according to claim 1, characterized in that, The mass ratio of 3-(N-morpholino)-2-hydroxypropanesulfonic acid to process water in Step 1 is 1 - 3:

1.

4. The synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate according to claim 1, wherein The inert gas in Step 2 includes any one of helium, neon, argon, krypton, and xenon.

5. The synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate according to claim 1, characterized in that, The mass fraction of activated carbon in Step 5 is 0.5%.

6. The synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate according to claim 1, wherein The solvent in Step 6 includes any one of methanol, ethanol, and isopropanol; The stepwise cooling in Step 6 is to first cool it down to 20 - 30 °C with cooling water, and then cool it down to 5 - 10 °C with a refrigerant; The temperature for keeping warm and crystallizing is 5 - 10 °C.

7. The synthesis process of sodium 3-(N-morpholino)-2-hydroxypropanesulfonate according to claim 1, characterized in that, The precise filtration in Step 6 is to filter using a filter element with a pore size of 0.22 - 0.45 μm.

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