Method for preparing lithium p-styrenesulfonate

Abstract

The invention discloses a method for preparing lithium p-styrenesulfonate, which comprises the following steps: reacting styrene with acyl chloride to generate p-styrenesulfonyl chloride, then reacting the p-styrenesulfonyl chloride with alcohol to generate p-styrenesulfonate, and finally hydrolyzing the p-styrenesulfonate and lithium hydroxide to obtain the lithium p-styrenesulfonate. As long as the operation environment reaches the standard, impurity metal ions in the product obtained in the previous step can be treated to a ppm level or a near ppm level before salification in the last step, meanwhile, only lithium hydroxide is introduced in the last step, alcohol is added to promote complete reaction of insufficient lithium hydroxide, and finally, an organic solvent is used for pulping and extraction, so that the product is obtained. Organic impurities and trace salts are separated and removed, lithium p-styrenesulfonate is obtained through filtration, the content of impurity metal salts is very low, treatment is very convenient, and the requirement for lower metal ion residues in the subsequent process can be met.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for synthesizing lithium p-styrene sulfonate. Background Technology

[0002] Lithium p-styrene sulfonate (C8H7LiO3S) is a multifunctional organic sulfonate monomer, mainly used in the field of new energy battery materials. As a key component of lithium battery binders, it improves the cycle stability of silicon-based anodes and constructs lithium-ion transport channels in solid electrolytes to improve conductivity. It can also be used in the chemical industry as an emulsion polymerization stabilizer and a polymer functional monomer for the synthesis of hydrophilic resins and ion exchange membranes. In addition, it can be used in special applications such as organic conductive materials (e.g., solar cells), photosensitive resin crosslinking agents, and surfactant synthesis.

[0003] Currently, the mainstream preparation method for lithium p-styrene sulfonate is based on halophenylethane as raw material. The process route is as follows: β-bromophenylethane is sulfonated with sulfur trioxide to generate β-bromoethylbenzenesulfonic acid, which is then reacted with sodium hydroxide aqueous solution to generate sodium p-vinylbenzenesulfonate. This is further acidified to prepare p-vinylbenzenesulfonic acid, and finally, p-ethylbenzenesulfonic acid is reacted with lithium hydroxide to prepare lithium p-styrene sulfonate.

[0004] However, this preparation method has the following problems: First, the sodium bromide and sodium p-vinylbenzenesulfonate produced when β-bromoethylbenzenesulfonic acid reacts with an aqueous sodium hydroxide solution are both readily soluble in water and precipitate simultaneously during cooling crystallization, making them difficult to separate. Complete removal of the sodium bromide is extremely challenging. Second, during the reaction of p-vinylbenzenesulfonic acid with lithium hydroxide, other inorganic acids present in the acidified p-styrenesulfonic acid also react with lithium hydroxide to generate impurity lithium salts (generally around 3.5%), thus affecting the content of the final product and the metal ion content. Although this preparation method is a relatively low-cost synthesis method, for electronic chemicals with high requirements for metal ions, the cost of removing metal ions in the later stages is not low, and the technology is challenging.

[0005] In response, Chinese invention patent application CN 116987016 A discloses an improved preparation process for lithium p-styrene sulfonate, specifically as follows: β-bromophenylethane is sulfonated with sulfur trioxide to prepare p-bromoethylbenzenesulfonic acid; a solution of p-bromoethylbenzenesulfonic acid is neutralized and eliminated with sodium hydroxide solution to prepare sodium p-vinylbenzenesulfonate; a solution of sodium p-vinylbenzenesulfonate is reacted with zinc chloride to prepare zinc p-styrene sulfonate; and zinc p-styrene sulfonate is added to water and reacted with lithium carbonate to prepare lithium p-styrene sulfonate. This improved process uses the zinc p-styrene sulfonate intermediate to react with lithium carbonate, utilizing the poor solubility of zinc salts to reduce inorganic salt residue, thereby increasing the dry weight content of the product and reducing the lithium salt content. However, the salt exchange reaction used in this preparation process is a heterogeneous reaction, where the sparingly soluble zinc sulfonate salt is converted into a sparingly soluble zinc carbonate salt in the aqueous phase to remove the zinc salt. This process is difficult to complete, and salt-encapsulation phenomena similar to lithium sulfonate salt encapsulating zinc sulfonate salt can occur. The particle size of the salts significantly affects the results, further increasing the difficulty of removing impurity metal salts in the later stages. Moreover, this preparation process still uses β-bromophenylethane as a raw material, generating a large amount of bromine-containing waste salts (such as NaBr) as byproducts, resulting in high treatment costs and severe environmental pollution. Furthermore, the price of the bromine-containing raw material fluctuates greatly, making it difficult to control production costs. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing lithium p-styrene sulfonate, which can obtain high-purity lithium p-styrene sulfonate with very low content of impurity metal salts, thus meeting the requirements for lower impurity metal ion residues in subsequent processes.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing lithium p-styrene sulfonate, comprising:

[0009] Step S1: Styrene reacts with acyl chloride to produce p-styrenesulfonyl chloride;

[0010] Step S2: p-Styrene sulfonyl chloride reacts with an alcohol to produce p-Styrene sulfonate;

[0011] Step S3: Hydrolyze styrene sulfonate with lithium hydroxide to generate lithium p-styrene sulfonate.

[0012] In some specific embodiments of the present invention, step S1 includes: adding a first reaction solvent and acyl chloride to a first reaction vessel and stirring thoroughly, then adding styrene and a polymerization inhibitor thereto, and while continuing to stir, heating to 60-90°C and refluxing for 2-10 hours to obtain a first reaction solution; the first reaction solution undergoes a first post-treatment to obtain p-styrenesulfonyl chloride.

[0013] In certain specific embodiments of the present invention, the first reaction solvent is selected from N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetonitrile, tetrahydrofuran, n-heptane, and n-octane.

[0014] In certain specific embodiments of the present invention, the acyl chloride is a sulfonyl chloride or an oxalyl chloride.

[0015] In certain specific embodiments of the present invention, the polymerization inhibitor is selected from phenthiazide, p-methoxyphenol, p-tert-butylcatechol, and phenol.

[0016] In some specific embodiments of the present invention, the molar ratio of styrene to acyl chloride is 1:(0.5~2), preferably 1:(0.8~2).

[0017] In certain specific embodiments of the present invention, the molar ratio of styrene to the polymerization inhibitor is 1:(0.001 to 0.005).

[0018] In some specific embodiments of the present invention, the mass ratio of the first reaction solvent to the styrene is 1:(0.2 to 1).

[0019] In some specific embodiments of the present invention, the first post-processing process includes the following steps: pouring the first reaction solution into ice water and stirring evenly, then filtering under reduced pressure to obtain crude S1; adding the crude S1 to water and slurrying, then filtering under reduced pressure again and drying to obtain S1 product as styrene sulfonyl chloride.

[0020] In some specific embodiments of the present invention, the pulping time in the first post-processing is 0.5 to 2 hours, preferably 0.5 to 1 hour.

[0021] In some specific embodiments of the present invention, in the first post-processing, the drying is performed under reduced pressure at 30~50°C.

[0022] In certain specific embodiments of the present invention, step S2 includes: adding a second reaction solvent and the product of S1 (p-styrene sulfonyl chloride) to a second reaction vessel, continuously stirring while controlling the temperature at 0±5°C, adding a mixture of triethylamine and alcohol dropwise, continuing to stir at 0±5°C for 0.5 to 5 hours after the addition is complete, then raising the temperature to 10 to 60°C and reacting with stirring, monitoring the reaction progress with liquid chromatography, and ending the reaction when the remaining amount of p-styrene sulfonyl chloride is <0.5%, to obtain a second reaction solution; the second reaction solution undergoes a second post-treatment to obtain p-styrene sulfonate.

[0023] In some specific embodiments of the present invention, in step S2, the second reaction solvent is at least one selected from DMF, DMA, dichloromethane, acetonitrile, tetrahydrofuran, n-heptane, and n-octane.

[0024] In some specific embodiments of the present invention, in step S2, the alcohol is methanol or ethanol.

[0025] In some specific embodiments of the present invention, in step S2, the molar ratio of styrenesulfonyl chloride, triethylamine, and alcohol is 1:(0.8-4):(0.8-8).

[0026] In some specific examples of the present invention, in step S2, the mass ratio of the second reaction solvent to p-styrenesulfonyl chloride is (3-8):1.

[0027] In some specific embodiments of the present invention, the second post-processing includes the following steps: pouring the second reaction solution into deionized water and stirring and washing for 0.5 to 2 hours, allowing it to stand and separate, retaining the lower organic phase; washing the separated organic phase again with deionized water and then separating the organic phase; repeating the washing and separation of the organic phase with deionized water several times, and concentrating the final organic phase under reduced pressure at 20 to 40°C to obtain the S2 product as p-styrene sulfonate.

[0028] In some specific embodiments of the present invention, step S3 includes: adding alcohol and product S2 (p-styrene sulfonate) to a third reaction vessel and stirring to dissolve; heating to an internal temperature of 25-80°C and continuously stirring while adding lithium hydroxide aqueous solution dropwise; after the addition is complete, maintaining the internal temperature at 25-80°C and continuously stirring the reaction, monitoring the pH value, and stopping the reaction when the pH is 6-7 to obtain a third reaction solution; the third reaction solution undergoes a third post-treatment to obtain the final product.

[0029] In some specific embodiments of the present invention, in step S3, the alcohol is methanol or ethanol.

[0030] In some specific embodiments of the present invention, in step S3, the molar ratio of styrene sulfonate to lithium hydroxide is 1:(0.7~0.95), preferably 1:(0.85~0.95).

[0031] In some specific examples of the present invention, in step S3, the mass ratio of styrene sulfonate to alcohol is 1:(2-20), preferably 1:(2-10).

[0032] In some specific embodiments of the present invention, in step S3, the mass percentage concentration of lithium hydroxide in the lithium hydroxide aqueous solution is 1% to 30%.

[0033] In some specific embodiments of the present invention, the third post-processing includes the following steps: the third reaction solution is rotary evaporated under reduced pressure at 40-70°C to obtain crude S3; an extraction solvent is added to the crude S3, the temperature is raised to 25-80°C, and the mixture is stirred and slurried for 1-10 hours; then, after cooling to room temperature, it is filtered under reduced pressure, and the resulting filter cake is dried under reduced pressure at 30-60°C to obtain the final product, which is p-styrene sulfonate.

[0034] In some specific embodiments of the present invention, in the third post-processing, the extraction solvent is at least one of acetonitrile, methanol, isopropanol, and tetrahydrofuran.

[0035] In some specific embodiments of the present invention, the extraction solvent is pre-distilled before use.

[0036] The present invention also provides lithium p-styrene sulfonate prepared by the above preparation method.

[0037] In this invention, room temperature refers to 20–30°C.

[0038] In this invention, in the first post-processing, the volume of the ice water is 2 to 6 times the volume of the first reaction solution, and the mass of the water used in the pulping is 1 to 5 times the mass of the crude S1 product.

[0039] In this invention, styrene is first reacted with acyl chloride to generate p-styrenesulfonyl chloride (step S1), then p-styrenesulfonyl chloride is reacted with an alcohol to generate p-styrenesulfonate (step S2), and finally, p-styrenesulfonate is hydrolyzed with lithium hydroxide to obtain lithium p-styrenesulfonate (step S3). Since the p-styrenesulfonate obtained in step S2 is an organic compound, in the post-treatment of the reaction solution in step S2 to separate and purify the p-styrenesulfonate, an organic compound and a deionized water phase can be used, allowing metal ions in the organic phase to enter the aqueous phase. This results in the organic phase being almost free of metal ions in the p-styrenesulfonate after separation from the aqueous phase. In other words, as long as the operating environment meets the standards, this invention can reduce the impurity metal ions in the product of S2 to the ppm level (or near the ppm level) in the post-treatment of step S2, or before the final salt formation step. Meanwhile, in the final step of this invention, only lithium hydroxide is introduced. The solubility of alcohol in lithium hydroxide increases the reactivity, and the temperature is increased to promote complete conversion of lithium hydroxide. Finally, an organic solvent is used to slurry and extract the lithium styrene sulfonate salt, separating and removing organic impurities and trace salts. Filtration yields high-purity lithium p-styrene sulfonate. Compared to other synthesis methods, the final product of this invention has a very low content of impurity metal salts and is very easy to process, meeting the requirement for lower metal ion residues in subsequent processes.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects:

[0041] (1) In this invention, all substances before the final salt formation step are organic. As long as the operating environment meets the standards, impurity metal ions can be effectively removed, reducing the impurity metal ion content in the final product to ppm or near ppm levels. Only a single lithium hydroxide of less than 1 equivalent is introduced in the final step, utilizing the solubility of lithium hydroxide in alcohol to increase the reactivity. Compared with other synthesis methods, the content of impurity metal salts in the final product of this invention is very low and it is also very easy to process, which can meet the requirement of lower metal ion residues in subsequent processes.

[0042] (2) Unlike traditional processes, which use β-bromophenyl ethane as a raw material and easily generate a large amount of bromine-containing waste salt (such as NaBr) byproducts, resulting in high treatment costs and serious environmental pollution, and whose production costs are difficult to control due to large fluctuations in the price of bromine raw materials, this invention effectively avoids the formation of bromide salts. By washing vinylbenzene sulfonate with deionized water multiple times, the separation effect from inorganic salts is achieved. The addition of less than 1 equivalent of lithium hydroxide can ensure the full use and complete conversion of lithium hydroxide.

[0043] (3) Unlike existing methods where inorganic salts often remain in the product, affecting electrochemical performance, the preparation method of this invention yields lithium styrene sulfonate with an HPLC purity greater than 99%, a dry matter content greater than 98.5%, and a common impurity metal ion content as low as 10%. -5 This meets the stringent requirements for monomer purity in electronic chemicals, such as new energy battery materials. Attached Figure Description

[0044] Figure 1 This is the 1H NMR spectrum of the product (p-styrenesulfonyl chloride) obtained in step S1 of Example 1.

[0045] Figure 2 The image shows the 1H NMR spectrum of the product (methyl styrene sulfonyl ester) obtained in step S2 of Example 1.

[0046] Figure 3 This is the 1H NMR spectrum of the product (ethyl p-styrenesulfonyl ester) obtained in step S2 of Example 2.

[0047] Figure 4 The image shows the 1H NMR spectrum of the product (lithium p-styrene sulfonate) obtained in step S3 of Example 1. Detailed Implementation

[0048] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and do not represent or limit the scope of protection of the present invention; the scope of protection of the present invention is defined by the claims.

[0049] Unless otherwise specified, all reagents or instruments used in the following examples and comparative examples are commercially available products.

[0050] In the following embodiments, the room temperature is approximately 25±5°C.

[0051] Example 1

[0052]

[0053] Step S1: Preparation of p-styrenesulfonyl chloride

[0054] Add 140 g of sulfonyl chloride to a reaction flask containing 90 g of N,N-dimethylformamide (DMF), stir for 1 hour, then add 65 g of styrene and 0.25 g of p-tert-butylcatechol, and continue stirring while heating to 90 °C and refluxing for 6 hours to obtain the first reaction solution.

[0055] The first reaction solution was poured into 800 ml of ice water and stirred for 30 minutes. The mixture was then filtered under reduced pressure at room temperature to obtain crude S1, which was a light red solid powder. Crude S1 was added to 100 ml of water and stirred for 1 hour. The mixture was then filtered again under reduced pressure at room temperature. The resulting solid was dried under reduced pressure at 40°C for 2 hours to obtain product S1, which was a pink solid weighing 80 g.

[0056] H-NMR of S1 product as follows Figure 1 H-NMR analysis revealed that the obtained product S1 was p-styrenesulfonyl chloride. HPLC analysis of the S1 product showed a purity of 97%, with a calculated yield of 63%.

[0057] Step S2: Preparation of methyl styrene sulfonate

[0058] Add 400 ml of dichloromethane (DCM) and 80 g of the product S1 (p-styrenesulfonyl chloride) obtained in step S1 above to a four-necked flask. Maintain the temperature at 0±5℃ and add dropwise a mixture of 80 g of triethylamine (TEA) and 57 g of methanol with stirring, completing the addition in approximately 1 h. After the addition is complete, continue stirring at 0±5℃ for 0.5 h, then raise the temperature to room temperature and continue stirring for approximately 2 h. When HPLC monitoring shows that the remaining amount of p-styrenesulfonyl chloride is <0.5%, the reaction is terminated, yielding the second reaction solution.

[0059] The second reaction solution was poured into 300 ml of deionized water, stirred and washed for 0.5 h, then allowed to stand and separated, retaining the lower organic phase; the organic phase was washed again with 150 ml of deionized water for 0.5 h, allowed to stand and separated again, retaining the lower organic phase; the separated organic phase was washed again with 150 ml of deionized water for 0.5 h, allowed to stand and separated a third time, retaining the lower organic phase; the finally separated organic phase was concentrated under reduced pressure at 40 °C to remove the solvent, yielding product S2, a slightly reddish oily substance, weighing approximately 52 g.

[0060] The S2 product was subjected to H-NMR analysis, and the results are as follows: Figure 2 As shown, analysis revealed that the obtained product S2 was methyl p-styrene sulfonate. HPLC analysis of the S2 product showed a purity of approximately 95%, with a calculated yield of 66%.

[0061] Step S3: Preparation of lithium styrene sulfonate

[0062] Add 260 ml of methanol and 52 g of the S2 product (ethyl p-styrene sulfonate) to a four-necked flask, and stir until the S2 product is fully dissolved. Then, heat the flask to 50 °C, and while stirring continuously, add an aqueous lithium hydroxide solution (composed of 9.4 g of LiOH·H2O and 40 ml of deionized water) dropwise to the flask using a dropping funnel. The addition is completed in about 0.5 h, during which the temperature inside the flask rises slightly. After the addition is complete, continue stirring the reaction at 50 °C, while monitoring the pH value with a pH meter. Stop the reaction when the pH value is approximately 7 (reaction time is approximately 5 h), and obtain the third reaction solution.

[0063] The third reaction solution was removed by rotary evaporation under reduced pressure at 40 °C to remove the solvent and water, yielding approximately 40.6 g of a yellow solid. 90 ml of isopropanol (as an extraction solvent for impurities) was added to the container containing this yellow solid, and the mixture was heated to 50 °C and stirred for 1 h. After cooling to room temperature, the mixture was filtered under reduced pressure, and the resulting filter cake was dried under reduced pressure at 50 °C to obtain 36 g of a white solid (the final product).

[0064] The obtained white solid was analyzed by HPLC and H-NMR. The results showed that the H-NMR was as follows: Figure 4 As shown, analysis of the H-NMR spectrum revealed that the final product was lithium p-styrene sulfonate. HPLC > 99%. The calculated yield was 72%. Further analysis of the final product revealed a moisture content of 1.3%, a dry matter content > 98.5%, and the following common metal ion contents: Na ions 0.004%, K ions 0.008%, Ca ions 0.009%, and Fe ions 0.008%.

[0065] Example 2

[0066]

[0067] Step S1: Preparation of p-styrenesulfonyl chloride

[0068] 126 g of sulfonyl chloride was added to a reaction flask containing 90 g of N,N-dimethylformamide (DMF), and the mixture was stirred for 1 hour. Then, 65 g of styrene and 0.25 g of p-methoxyphenol were added. The mixture was stirred continuously, heated to 90 °C, and refluxed for 2 hours to complete the reaction and obtain the first reaction solution.

[0069] The first reaction solution was poured into 800 ml of ice water and stirred for 30 minutes. The mixture was then filtered under reduced pressure at room temperature to obtain crude S1, which was a light red solid powder. Crude S1 was added to 100 ml of water and stirred for 0.5 hours. The mixture was then filtered again under reduced pressure at room temperature. The resulting solid was dried under reduced pressure at 30°C for 2 hours to obtain product S1, which was a pink solid weighing 82 g.

[0070] The obtained product S1 was identified as p-styrenesulfonyl chloride by ¹H-NMR analysis. The HPLC purity was 97%, and the calculated yield was 65%.

[0071] Step S2: Preparation of ethyl p-styrene sulfonate

[0072] Add 410 ml of dichloromethane (DCM) and 82 g of the product S1 (p-styrenesulfonyl chloride) obtained in step S1 above to a four-necked flask. Maintain the temperature at 0 ± 5 °C and add dropwise a mixture of 49 g of triethylamine and 37 g of ethanol with stirring, completing the addition in approximately 1 h. After the addition is complete, continue stirring at 0 ± 5 °C for 0.5 h, then raise the temperature to 50 °C and continue stirring for approximately 1 h. When HPLC monitoring shows that the remaining amount of p-styrenesulfonyl chloride is <0.5%, the reaction is terminated, yielding the second reaction solution.

[0073] The second reaction solution was poured into 300 ml of deionized water, stirred and washed for 0.5 h, then allowed to stand and separated, retaining the lower organic phase; the organic phase was washed again with 150 ml of deionized water for 0.5 h, allowed to stand and separated again, retaining the lower organic phase; the separated organic phase was washed again with 150 ml of deionized water for 0.5 h, allowed to stand and separated a third time, retaining the lower organic phase; the finally separated organic phase was concentrated under reduced pressure at 40 °C to remove the solvent, yielding product S2, a slightly reddish oily substance, weighing approximately 73 g.

[0074] The S2 product was subjected to H-NMR analysis, and the results are as follows: Figure 3 As shown, analysis revealed that the obtained product S2 was ethyl p-styrene sulfonate. HPLC analysis of the S2 product showed a purity of approximately 96%, resulting in a calculated yield of 85%.

[0075] Step S3: Preparation of lithium styrene sulfonate

[0076] Add 365 ml of ethanol and 73 g of S2 product (ethyl p-styrene sulfonate) to a four-necked flask and stir until the S2 product is fully dissolved. Then, heat the flask to 65°C and, while stirring continuously, add an aqueous lithium hydroxide solution (composed of 13.0 g of LiOH·H2O and 65 ml of deionized water) dropwise using a dropping funnel. The addition is completed in about 0.5 h, during which the temperature inside the flask rises slightly. After the addition is complete, continue stirring the reaction at 65°C while monitoring the pH value with a pH meter. Stop the reaction when the pH value is approximately 7 (reaction time is approximately 3 h), to obtain the third reaction solution.

[0077] The third reaction solution was removed by rotary evaporation under reduced pressure at 40 °C to remove the solvent and water, yielding approximately 60 g of a yellow solid. 90 ml of isopropanol was added to the container containing this yellow solid, and the mixture was heated to 50 °C and stirred for 1 h. After cooling to room temperature, the mixture was filtered under reduced pressure, and the resulting filter cake was dried under reduced pressure at 50 °C to obtain 49 g of a white solid (the final product).

[0078] The obtained white solid was analyzed by ¹H-NMR, which revealed that the final product was lithium p-styrene sulfonate. HPLC analysis of the white solid showed an HPLC resolution >99%, with a calculated yield of 75%. Further analysis of the final product revealed a moisture content of 3%, a dry matter content >98.5%, and the following common metal ion contents: Na ions 0.004%, K ions 0.008%, Ca ions 0.003%, and Fe ions 0.003%.

[0079] Example 3

[0080]

[0081] Step S1: Preparation of p-styrenesulfonyl chloride

[0082] 115 g of sulfonyl chloride was added to a reaction flask containing 90 g of N,N-dimethylformamide (DMF), and the mixture was stirred for 1 hour. Then, 65 g of styrene and 0.25 g of p-methoxyphenol were added while stirring. The mixture was heated to 90 °C and refluxed for 4 hours while stirring. The reaction was then stopped to obtain the first reaction solution.

[0083] The first reaction solution was poured into 800 ml of ice water and stirred for 30 minutes. The mixture was then filtered under reduced pressure at room temperature to obtain crude S1, which was a light red solid powder. Crude S1 was added to 100 ml of water and stirred for 0.5 hours. The mixture was then filtered again under reduced pressure at room temperature. The resulting solid was dried under reduced pressure at 30°C for 2 hours to obtain product S1, which was a pink solid weighing 98 g.

[0084] The obtained product S1 was identified as p-styrene sulfonyl chloride by ¹H-NMR analysis. The HPLC purity was 97%, and the calculated yield was 77%.

[0085] Step S2: Preparation of ethyl p-styrene sulfonate

[0086] Add 490 ml of dichloromethane (DCM) and 98 g of the product S1 (p-styrenesulfonyl chloride) obtained in step S1 above to a four-necked flask. Maintain the temperature at 0 ± 5 °C and add dropwise a mixture of 59 g of triethylamine and 47 g of ethanol with stirring, completing the addition in approximately 1 h. After the addition is complete, continue stirring at 0 ± 5 °C for 0.5 h, then raise the temperature to 50 °C and continue stirring for approximately 1 h. When HPLC monitoring shows that the remaining amount of p-styrenesulfonyl chloride is <0.5%, the reaction is terminated, yielding the second reaction solution.

[0087] The second reaction solution was poured into 300 ml of deionized water, stirred and washed for 0.5 h, then allowed to stand and separated, retaining the lower organic phase; the organic phase was washed again with 150 ml of deionized water for 0.5 h, allowed to stand and separated again, retaining the lower organic phase; the separated organic phase was washed again with 150 ml of deionized water for 0.5 h, allowed to stand and separated a third time, retaining the lower organic phase; the finally separated organic phase was concentrated under reduced pressure at 40 °C to remove the solvent, yielding product S2, a slightly reddish oily substance, weighing approximately 85 g.

[0088] ¹H-NMR analysis of the S2 product revealed it to be ethyl p-styrene sulfonate. HPLC analysis showed a purity of approximately 95%, resulting in a yield of 83%.

[0089] Step S3: Preparation of lithium styrene sulfonate

[0090] Add 425 ml of ethanol and 85 g of the S2 product (ethyl p-styrene sulfonate) to a four-necked flask and stir until the S2 product is fully dissolved. Then, heat the flask to 75°C and, while stirring continuously, add an aqueous lithium hydroxide solution (composed of 15.1 g of LiOH·H2O and 70 ml of deionized water) dropwise using a dropping funnel. The addition is completed in about 0.5 h, during which the temperature inside the flask rises slightly. After the addition is complete, continue stirring the reaction at 75°C while monitoring the pH value with a pH meter. Stop the reaction when the pH value is approximately 7 (reaction time is approximately 4 h), to obtain the third reaction solution.

[0091] The solvent and water in the third reaction solution were removed by rotary evaporation under reduced pressure at 40 °C, yielding approximately 66 g of a yellow solid. 90 ml of acetonitrile was added to the container containing this yellow solid, and the mixture was heated to 50 °C and stirred for 1 h. After cooling to room temperature, the mixture was filtered under reduced pressure, and the resulting filter cake was dried under reduced pressure at 50 °C to obtain 60 g of a white solid (the final product).

[0092] The obtained white solid was analyzed by ¹H-NMR, which revealed that the final product was lithium p-styrene sulfonate. HPLC analysis of the white solid showed an HPLC yield >99%, with a calculated yield of 79%. Further analysis of the final product revealed a moisture content of 3%, a dry matter content >98.5%, and the following common metal ion contents: Na ions 0.005%, K ions 0.008%, Ca ions 0.006%, and Fe ions 0.006%.

[0093] In all the above embodiments, the solvent used in step S3 is pre-distilled before use to remove metal ions from the solvent; the water used in steps S2 and S3 is deionized water.

[0094] In this invention, styrene is first reacted with acyl chloride to generate p-styrenesulfonyl chloride (step S1), then p-styrenesulfonyl chloride is reacted with an alcohol to generate p-styrenesulfonate (step S2), and finally, p-styrenesulfonate is hydrolyzed with lithium hydroxide to obtain lithium p-styrenesulfonate (step S3). Since the p-styrenesulfonate obtained in step S2 is an organic compound, in the post-treatment of the reaction solution in step S2 to separate and purify the p-styrenesulfonate, an organic compound and a deionized water phase can be used, allowing metal ions in the organic phase to enter the aqueous phase. This results in the organic phase being almost free of metal ions in the p-styrenesulfonate after separation from the aqueous phase. In other words, as long as the operating environment meets the standards, this invention can reduce the impurity metal ions in the product of S2 to the ppm level (or near the ppm level) in the post-treatment of step S2, or before the final salt formation step. Meanwhile, in the final step of this invention, only lithium hydroxide is introduced. The solubility of alcohol in lithium hydroxide increases the reactivity, and the temperature is increased to promote complete conversion of lithium hydroxide. Finally, an organic solvent is used to slurry and extract the lithium styrene sulfonate salt, separating and removing organic impurities and trace salts. Filtration yields high-purity lithium p-styrene sulfonate. Compared to other synthesis methods, the final product of this invention has a very low content of impurity metal salts and is very easy to process, meeting the requirement for lower metal ion residues in subsequent processes.

[0095] Therefore, it is evident that the objective of this invention has been fully and effectively achieved. The function and structural principles of this invention have been demonstrated and explained in the embodiments. Any modifications can be made to the implementation methods without departing from these principles. Therefore, this invention includes all modified embodiments based on the spirit and scope of the claims.

Claims

1. A method for preparing lithium p-styrenesulfonate, comprising: Step S1: reacting styrene with acyl chloride to generate p-styrenesulfonyl chloride; Step S2: reacting p-styrenesulfonyl chloride with alcohol to generate p-styrenesulfonate; Step S3: hydrolyzing p-styrenesulfonate with lithium hydroxide to generate lithium p-styrenesulfonate.

2. The method of preparing lithium p-styrenesulfonate according to claim 1, wherein, comprising Step S1: adding a first reaction solvent and acyl chloride into a first reaction container and stirring thoroughly, then adding styrene and polymerization inhibitor into the first reaction container, continuously stirring, and heating to 60-90℃, and refluxing for 2-10 hours to obtain a first reaction liquid; the first reaction liquid is treated to obtain p-styrenesulfonyl chloride; Step S2: adding a second reaction solvent and p-styrenesulfonyl chloride into a second reaction container, continuously stirring, and controlling the temperature at 0±5℃, then adding a mixture of triethylamine and alcohol dropwise into the second reaction container, continuously stirring at 0±5℃ for 0.5-5 hours after the dropwise addition is completed, then heating to 10-60℃, and reacting with stirring, monitoring the reaction process by liquid chromatography, and ending the reaction when the residual amount of p-styrenesulfonyl chloride is less than 0.5% to obtain a second reaction liquid; the second reaction liquid is treated to obtain p-styrenesulfonate; Step S3: adding alcohol and p-styrenesulfonate into a third reaction container, dissolving with stirring, heating to an internal temperature of 25-80℃, continuously stirring, then adding aqueous lithium hydroxide dropwise into the third reaction container, continuously stirring at an internal temperature of 25-80℃ after the dropwise addition is completed, monitoring the pH value, and ending the reaction when the pH value is 6-7 to obtain a third reaction liquid, wherein the molar ratio of p-styrenesulfonate to lithium hydroxide is 1:(0.7-0.95); the third reaction liquid is treated to obtain lithium p-styrenesulfonate.

3. The method of preparing lithium p-styrenesulfonate according to claim 2, wherein, In step S1, the first reaction solvent is one selected from N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, tetrahydrofuran, n-heptane, and n-octane; the acyl chloride is sulfuryl chloride or oxalyl chloride; and the polymerization inhibitor is one selected from phenothiazine, p-methoxyphenol, p-tert-butylcatechol, and phenol; in step S2, the second reaction solvent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, acetonitrile, tetrahydrofuran, n-heptane, and n-octane; and the alcohol is methanol or ethanol; in step S3, the alcohol is methanol or ethanol.

4. The method of preparing lithium p-styrenesulfonate according to claim 2, wherein In step S1, the molar ratio of styrene to acyl chloride is 1:(0.5-2), and the mass ratio of the first reaction solvent to styrene is 1:(0.2-1).

5. The method of preparing lithium p-styrenesulfonate according to claim 2, wherein The first treatment process comprises the following steps: pouring the first reaction liquid into ice water and stirring uniformly, then filtering under reduced pressure to obtain S1 crude product; adding the S1 crude product into water and beating, then filtering under reduced pressure again, and drying to obtain S1 product, which is styrene sulfonyl chloride.

6. The method of preparing lithium p-styrenesulfonate according to claim 2, wherein In step S2, the molar ratio of p-styrenesulfonyl chloride, triethylamine, and alcohol is 1:(0.8-4):(0.8-8), and the mass ratio of the second reaction solvent to p-styrenesulfonyl chloride is (3-8):

1.

7. The method for preparing lithium p-styrene sulfonate according to claim 2, characterized in that, The second post-treatment process comprises the following steps: pouring the second reaction solution into deionized water, stirring and washing for 0.5-2 hours, standing and separating, and retaining the lower organic phase; stirring and washing the separated organic phase with deionized water again, and separating the organic phase; repeating the deionized water washing and organic phase separation for several times, and concentrating the last obtained organic phase at 20-40°C under reduced pressure to obtain the S2 product, which is p-styrene sulfonate.

8. The method for preparing lithium p-styrene sulfonate according to claim 2, characterized in that, In step S3, the mass ratio of p-styrene sulfonate to alcohol is 1: (2-20).

9. The method of preparing lithium p-styrenesulfonate according to claim 2, wherein The third post-treatment process comprises the following steps: rotary evaporation of the third reaction solution at 40-70°C under reduced pressure to obtain S3 crude product; adding an extraction solvent to the S3 crude product, heating to 25-80°C, and stirring and beating for 1-10 hours; then, cooling to room temperature, filtering under reduced pressure, drying the filter cake at 30-60°C under reduced pressure, and obtaining the final product, which is lithium p-styrene sulfonate.

10. Lithium p-styrene sulfonate prepared by the method of any one of claims 1-9.

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