A method for preparing carbon fiber grade dimethyl sulfoxide

Abstract

This invention belongs to the field of dimethyl sulfoxide (DMSO) preparation technology, and relates to a method for preparing carbon fiber-grade DMSO. Using industrial-grade DMSO as raw material, the insoluble impurities in the raw material are first filtered out. Metal ion impurities and acidic impurities are then removed by column chromatography. Distillation dehydration is then performed, followed by cooling and crystallization to remove soluble impurities. Finally, volatile impurities are removed by gas stripping, thus preparing carbon fiber-grade DMSO. The column chromatography uses a zwitterionic exchange resin. This resin uses organosilicon-modified γ-Fe₂O₃ magnetic nanoparticles as the core, copolymerized with styrene and divinylbenzene to obtain composite microspheres. The surface of the microspheres is acetylated and amination-treated to introduce dithiocarbamate and quaternary ammonium groups, resulting in a zwitterionic exchange resin capable of adsorbing metal ions and acidic impurities. The mechanical strength of the microspheres meets the requirements of continuous industrial production. The two functional groups on the surface of the microspheres do not interfere with each other, allowing for simultaneous removal of impurities and achieving rapid dynamic adsorption.

Description

Technical Field

[0001] This invention relates to the field of dimethyl sulfoxide purification technology, and more particularly to a method for preparing carbon fiber grade dimethyl sulfoxide. Background Technology

[0002] In carbon fiber production, dimethyl sulfoxide (DMSO) is a crucial solvent. Its purity directly affects various stages of the carbon fiber preparation process (such as polymerization, spinning, and precursor fiber quality), ultimately determining the performance of the final carbon fiber. For example, residual metal ions in DMSO can participate in the reaction, triggering side reactions and causing a broadening of the polymer molecular weight distribution and instability in the degree of polymerization. Acidic (such as sulfonic acids) or basic (such as amines) impurities can alter the pH of the polymerization system, interfering with the efficiency of the initiator and leading to incomplete polymerization or structural defects in the product.

[0003] The purity of dimethyl sulfoxide (DMSO) used in the preparation of carbon fibers must be above 99.5%, with a water content below 0.1% and a total metal ion content below 1 ppm. Existing DMSO purification technologies have significant limitations. Traditional distillation methods utilize the boiling point differences between DMSO and miscible impurities such as water and methanol for separation, but this is insufficient to remove azeotropic impurities. Furthermore, for heat-sensitive impurities, such as some polymers, distillation may lead to side reactions with DMSO. Crystallization methods utilize the difference in freezing points between DMSO and impurities through cooling crystallization, but this method is ineffective for separating low-melting-point impurities such as methanol and ethanol, and easily forms solid-liquid eutectic systems. Adsorption methods utilize molecular sieves, activated carbon, and ion exchange resins to remove water, metal ions, and organic impurities, but adsorbents have low selectivity for impurities with similar polarities, are easily saturated, and are difficult to regenerate; activated carbon and other adsorbents may introduce new impurities. Ion exchange resins, on the other hand, can precisely remove metal ions, acidic and alkaline impurities, and polar organic compounds, offering high selectivity, high efficiency, and regeneration.

[0004] Chinese patent application CN 113461579 A discloses a method for preparing pharmaceutical-grade dimethyl sulfoxide (DMSO). This method involves mixing industrial-grade DMSO and distilled water in a specific ratio, followed by distillation, dehydration, membrane filtration, and resin exchange to obtain pharmaceutical-grade DMSO. This method employs a process of first distillation and dehydration, then filtration and adsorption. During distillation and dehydration, some impurities, such as metal ions and polar organic compounds, are difficult to completely separate and may decompose or undergo side reactions at high temperatures. Filtering insoluble impurities first and selectively removing some impurities using ion exchange resin before subsequent operations reduces the workload, improves overall purification efficiency, and yields a product with higher purity. Summary of the Invention

[0005] This invention aims to provide a system and method for preparing carbon fiber-grade dimethyl sulfoxide. The technical solution involves filtering, column chromatography, distillation, crystallization, and gas stripping of industrial-grade dimethyl sulfoxide to progressively remove impurities, thereby preparing carbon fiber-grade dimethyl sulfoxide. The column chromatography uses a zwitterionic ion exchange resin to simultaneously remove acidic impurities and metal ions from the industrial-grade dimethyl sulfoxide. The reaction is fast, allows for continuous processing in a column apparatus, does not introduce new impurities, and the resin is regenerable and reusable.

[0006] To achieve the above objectives, this application provides a method for preparing carbon fiber-grade dimethyl sulfoxide, comprising:

[0007] Step S1: Industrial-grade dimethyl sulfoxide is fed into a filter tower for filtration to remove insoluble impurities and obtain primary purified dimethyl sulfoxide.

[0008] Step S2: The filtrate enters a column chromatography tower and is purified by column chromatography to remove acidic substances and metal ions, yielding secondary purified dimethyl sulfoxide.

[0009] Step S3: Primary purified dimethyl sulfoxide is dehydrated by distillation and then cooled and crystallized to remove soluble impurities, yielding intermediate purified dimethyl sulfoxide.

[0010] Step S4: Add intermediate purified dimethyl sulfoxide into the gas stripping device, introduce a gas source for gas stripping, and obtain carbon fiber grade dimethyl sulfoxide.

[0011] Preferably, in step S2, the column chromatography column is filled with zwitterionic resin, and the flow rate of dimethyl sulfoxide entering the column chromatography column is 0.5~2 BV / h. Before use, the zwitterionic resin is alternately rinsed with a 2% hydrochloric acid aqueous solution and a 2% sodium chloride solution, and then soaked in a dimethyl sulfoxide aqueous solution for 10~12 h, with a water to dimethyl sulfoxide mass ratio of 1:(6~9). The 2% hydrochloric acid rinsing is to activate the quaternary ammonium groups and remove residual amine impurities from the resin synthesis, while the 2% sodium chloride solution rinsing is to convert the resin to Cl... - To avoid introducing other anions, soaking the resin in dimethyl sulfoxide aqueous solution is to swell the resin, open the porous structure, and improve subsequent adsorption efficiency.

[0012] Preferably, in step S3, the distillation step is as follows: heating to 120~150℃ under normal pressure and holding for 5~10 min; the cooling crystallization operation is as follows: cooling to 5~10℃ at a rate of 10~15℃ / h, and cooling to -5~-10℃ at a rate of 5~10℃ / h.

[0013] Preferably, in step S4, the gas source is any one or more of nitrogen and air; the flow rate of the gas source is (0.1~1 L / min). m3 (Liquid).

[0014] This application provides a method for preparing the zwitterionic ion exchange resin described in step S2, comprising:

[0015] Step A1: Disperse γ-Fe2O3 magnetic nanoparticles in an ethanol aqueous solution, adjust the pH to 4-5 with acetic acid, add 3-(triethoxysilyl)-N-vinylpropylamine, and react under inert gas protection to obtain organosilicon-modified γ-Fe2O3;

[0016] Step A2: Organosilicon-modified γ-Fe2O3, styrene and divinylbenzene are dispersed in ethanol to form a uniform dispersion. The dispersant is dissolved in water to obtain an aqueous phase. The dispersion is added to the aqueous phase, and an initiator is added to react and obtain composite microspheres.

[0017] Step A3: Disperse the composite microspheres in dichloromethane, add pyridine and acylation reagent, and react to obtain acetylated composite microspheres;

[0018] Step A4: Disperse the acetylated composite microspheres in ethanol, add an amination reagent, and after the first reaction, obtain imine-treated composite microspheres. Add sodium borohydride and after the second reaction, obtain amination-treated composite microspheres.

[0019] Step A5: Disperse the amination composite microspheres in ethanol, adjust the pH to 8-10, add carbon disulfide, and react to obtain dithiocarbamate composite microspheres.

[0020] Step A6: Disperse dithiocarbamate composite microspheres in dichloromethane, add formaldehyde, concentrated hydrochloric acid and aluminum trichloride, and after the first reaction, obtain an intermediate. Adjust the pH to 10, add trimethylamine aqueous solution, and after the second reaction, obtain zwitterionic exchange resin.

[0021] Preferably, in step A1, the mass ratio of ethanol to water in the ethanol-water solution is 1:(1~1.5).

[0022] Preferably, in step A1, the mass ratio of the γ-Fe2O3 magnetic nanoparticles, the aqueous ethanol solution, and 3-(triethoxysilyl)-N-vinylpropylamine is 1:(10~15):(0.15~0.35).

[0023] Preferably, in step A1, the reaction temperature is 50~60℃ and the reaction time is 8~10 h.

[0024] Preferably, in step A2, the initiator is any one or more of benzoyl peroxide and azobisisobutyronitrile.

[0025] Preferably, in step A2, the dispersant is any one or more of polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone.

[0026] Preferably, in step A2, the reaction temperature is 60~80℃ and the reaction time is 4~6 h.

[0027] Preferably, in step A2, the mass ratio of the organosilicon-modified γ-Fe2O3, styrene, divinylbenzene and ethanol is 1:(1.5~3.5):(1.15~2.5):(5~10).

[0028] Preferably, in step A2, the mass ratio of water to dispersant is 1:(0.01~0.03); the mass ratio of aqueous phase, dispersion and initiator is 1:(0.1~0.5):(0.005~0.012).

[0029] Preferably, in step A3, the acylation reagent is any one or more of acetic anhydride and acetyl chloride.

[0030] Preferably, in step A3, the reaction temperature is 60~90℃ and the reaction time is 4~6 h.

[0031] Preferably, in step A3, the mass ratio of the composite microspheres, solvent, acylation reagent, and pyridine is 1:(3~5):(0.1~0.3):(0.003~0.01).

[0032] Preferably, in step A4, the amination reagent is any one or more of ethylenediamine and pentanediamine.

[0033] Preferably, in step A4, the temperature of the first reaction is 50~70℃, and the reaction time is 3~6 h.

[0034] Preferably, in step A4, the second reaction takes 1 to 2 hours.

[0035] Preferably, in step A4, the mass ratio of the acetylated composite microspheres, ethanol, amination reagent, and sodium borohydride is 1:(5~10):(1.2~1.5):(0.1~0.3).

[0036] Preferably, in step A5, the reaction time is 2-4 h; the mass ratio of the amination composite microspheres, ethanol, and carbon disulfide is 1:(3-5):(1.5-2).

[0037] Preferably, in step A6, the temperature of the first reaction is 40~60℃, and the reaction time is 3~5 h.

[0038] Preferably, in step A6, the second reaction takes 4 to 6 hours.

[0039] Preferably, in step A6, the mass ratio of trimethylamine to water in the trimethylamine aqueous solution is 1:(3~5).

[0040] Preferably, in step A6, the mass ratio of the dithiocarbamate composite microspheres, solvent, formaldehyde, concentrated hydrochloric acid, aluminum trichloride, and trimethylamine aqueous solution is 1: (5~10): (0.005~0.011): (0.001~0.0015): (0.005~0.0075): (0.75~1.2).

[0041] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0042] (1) This technical solution uses industrial-grade dimethyl sulfoxide as the starting material. First, it is filtered to remove insoluble impurities and oligomers from the raw material to prevent clogging of the pipeline and affect subsequent purification. The filtered dimethyl sulfoxide is purified by zwitterionic exchange resin column chromatography. The resin adsorbs metal ions and acidic impurities in the raw material at room temperature to avoid side reactions between impurities and dimethyl sulfoxide at high temperature. Then, it is distilled to remove a large amount of water from the raw material. Then, it is cooled to allow soluble impurities in the raw material to precipitate in the form of crystals, further purifying dimethyl sulfoxide. Finally, it is stripped by gas to remove volatile impurities from dimethyl sulfoxide to obtain high-purity dimethyl sulfoxide. The above technical solution is complete, covers the impurities present in industrial-grade dimethyl sulfoxide, and has a continuous purification process. The purification method is mild and can greatly reduce the loss of raw materials and equipment wear during the purification process.

[0043] (2) In this technical solution, the column chromatography tower is filled with zwitterionic exchange resin. The resin uses organosilicon-modified γ-Fe2O3 magnetic nanoparticles as the core, and copolymerizes them with styrene and divinylbenzene to obtain composite microspheres. The surface of the microspheres is acetylated and amination treated to introduce dithiocarbamate groups. After chloromethylation, quaternary ammonium groups are introduced to prepare zwitterionic exchange resin that can simultaneously adsorb metal ions and acidic impurities. The porous structure of composite microspheres formed by styrene-divinylbenzene copolymerization provides a large specific surface area, shortens the mass transfer distance, and accelerates the adsorption kinetics process. The dithiocarbamate groups introduced on the surface of the microspheres chelate with metal ions, resulting in a high density of binding sites and a large adsorption capacity. The quaternary ammonium groups, as strong basic groups, can quickly neutralize acidic impurities in dimethyl sulfoxide and achieve efficient removal through ion exchange. The two functional groups do not interfere with each other and can remove two types of impurities simultaneously. At the same time, the spherical structure and mechanical strength of the microspheres are suitable for filling column chromatography towers, with uniform fluid resistance, and can withstand high flow rate operation, meeting the needs of continuous industrial production. Organosilicon-modified γ-Fe2O3 magnetic nanoparticles can be rapidly enriched or dispersed under an external magnetic field, facilitating solid-liquid separation and avoiding the clogging problem caused by small particles in traditional filtration. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the preparation process of a zwitterionic ion exchange resin.

[0045] Figure 2 This is a flowchart illustrating the preparation process of carbon fiber grade dimethyl sulfoxide. Detailed Implementation

[0046] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0047] Unless otherwise specified, all reagents and equipment used in the following examples were purchased from commercial channels.

[0048] Example 1

[0049] like Figure 1 As shown, a zwitterionic ion exchange resin is prepared by means of:

[0050] Step A1: Disperse 10 g of γ-Fe2O3 magnetic nanoparticles in 100 g of ethanol aqueous solution (50 g of ethanol and 50 g of water), adjust the pH to 4-5 with acetic acid, add 1.5 g of 3-(triethoxysilyl)-N-vinylpropylamine, and react at 50 °C for 10 h under inert gas protection to obtain organosilicon modified γ-Fe2O3.

[0051] Step A2: Disperse 10 g of organosilicon-modified γ-Fe2O3, 15 g of styrene and 11.5 g of divinylbenzene in 50 g of ethanol to form a uniform dispersion. Dissolve 1 g of polyvinyl alcohol in 100 g of water to obtain an aqueous phase. Add 10 g of the dispersion to 100 g of the aqueous phase and add 0.5 g of benzoyl peroxide. React at 60 °C for 6 h to obtain composite microspheres.

[0052] Step A3: Disperse 10 g of composite microspheres in 30 g of dichloromethane, add 0.03 g of pyridine and 1 g of acetic anhydride, and react at 60 °C for 6 h to obtain acetylated composite microspheres.

[0053] Step A4: Disperse 10 g of acetylated composite microspheres in 50 g of ethanol, add 12 g of ethylenediamine, react at 50 °C for 6 h to obtain imide composite microspheres, add 1 g of sodium borohydride, react at room temperature for 2 h to obtain amination composite microspheres.

[0054] Step A5: Disperse 10 g of amination composite microspheres in 30 g of ethanol, adjust the pH to 8-10, add 15 g of carbon disulfide, and react at room temperature for 4 h to obtain dithiocarbamate composite microspheres.

[0055] Step A6: Disperse 10 g of dithiocarbamate composite microspheres in 50 g of dichloromethane, add 0.05 g of formaldehyde, 0.01 g of concentrated hydrochloric acid, and 0.05 g of aluminum trichloride, react at 40 °C for 5 h to obtain an intermediate. Adjust the pH to 10, add 7.5 g of trimethylamine aqueous solution (1.9 g of trimethylamine and 5.6 g of water), react at room temperature for 6 h to obtain a zwitterionic exchange resin, as shown below. Figure 2 As shown.

[0056] Example 2

[0057] like Figure 1 As shown, a zwitterionic ion exchange resin is prepared by means of:

[0058] Step A1: 10 g of γ-Fe2O3 magnetic nanoparticles were dispersed in 120 g of ethanol aqueous solution (53 g of ethanol and 67 g of water). The pH was adjusted to 4-5 with acetic acid. 2.5 g of 3-(triethoxysilyl)-N-vinylpropylamine was added. The reaction was carried out at 55 °C for 9 h under inert gas protection to obtain organosilicon-modified γ-Fe2O3.

[0059] Step A2: Disperse 10 g of organosilicon-modified γ-Fe2O3, 35 g of styrene and 15 g of divinylbenzene in 75 g of ethanol to form a uniform dispersion. Dissolve 2 g of polyethylene glycol in 100 g of water to obtain an aqueous phase. Add 30 g of the dispersion to 100 g of the aqueous phase and add 1 g of azobisisobutyronitrile. React at 70 °C for 5 h to obtain composite microspheres.

[0060] Step A3: Disperse 10 g of composite microspheres in 40 g of dichloromethane, add 0.07 g of pyridine and 2 g of acetyl chloride, and react at 80 °C for 5 h to obtain acetylated composite microspheres.

[0061] Step A4: Disperse 10 g of acetylated composite microspheres in 75 g of ethanol, add 13 g of pentanediamine, react at 60 °C for 5 h to obtain imide composite microspheres, add 2 g of sodium borohydride, react at room temperature for 1.5 h to obtain amination composite microspheres.

[0062] Step A5: Disperse 10 g of amination composite microspheres in 40 g of ethanol, adjust the pH to 8-10, add 17 g of carbon disulfide, and react at room temperature for 3 h to obtain dithiocarbamate composite microspheres.

[0063] Step A6: Disperse 10 g of dithiocarbamate composite microspheres in 75 g of dichloromethane, add 0.075 g of formaldehyde, 0.013 g of concentrated hydrochloric acid, and 0.06 g of aluminum trichloride, react at 50 °C for 4 h to obtain an intermediate. Adjust the pH to 10, add 9 g of trimethylamine aqueous solution (1.8 g of trimethylamine and 7.2 g of water), react at room temperature for 5 h to obtain a zwitterionic exchange resin, as shown below. Figure 2 As shown.

[0064] Example 3

[0065] like Figure 1 As shown, a zwitterionic ion exchange resin is prepared by means of:

[0066] Step A1: Disperse 10 g of γ-Fe2O3 magnetic nanoparticles in 200 g of ethanol aqueous solution (60 g of ethanol and 90 g of water), adjust the pH to 4-5 with acetic acid, add 3.5 g of 3-(triethoxysilyl)-N-vinylpropylamine, and react at 60 °C for 8 h under inert gas protection to obtain organosilicon modified γ-Fe2O3.

[0067] Step A2: Disperse 10 g of organosilicon-modified γ-Fe2O3, 35 g of styrene and 25 g of divinylbenzene in 100 g of ethanol to form a uniform dispersion. Dissolve 3 g of polyvinylpyrrolidone in 100 g of water to obtain an aqueous phase. Add 50 g of the dispersion to the 100 g aqueous phase and add 1.2 g of azobisisobutyronitrile. React at 80 °C for 4 h to obtain composite microspheres.

[0068] Step A3: Disperse 10 g of composite microspheres in 50 g of dichloromethane, add 0.1 g of pyridine and 3 g of acetic anhydride, and react at 90 °C for 4 h to obtain acetylated composite microspheres.

[0069] Step A4: Disperse 10 g of acetylated composite microspheres in 100 g of ethanol, add 15 g of pentanediamine, react at 70 °C for 3 h to obtain imide composite microspheres, add 3 g of sodium borohydride, react at room temperature for 1 h to obtain amination composite microspheres.

[0070] Step A5: Disperse 10 g of amination composite microspheres in 50 g of ethanol, adjust the pH to 8-10, add 20 g of carbon disulfide, and react at room temperature for 2 h to obtain dithiocarbamate composite microspheres.

[0071] Step A6: Disperse 10 g of dithiocarbamate composite microspheres in 100 g of dichloromethane, add 0.11 g of formaldehyde, 0.015 g of concentrated hydrochloric acid, and 0.075 g of aluminum trichloride, react at 60 °C for 3 h to obtain an intermediate. Adjust the pH to 10, add 12 g of trimethylamine aqueous solution (2 g of trimethylamine and 10 g of water), react at room temperature for 4 h to obtain a zwitterionic exchange resin, as shown below. Figure 2 As shown.

[0072] Example 4

[0073] like Figure 2 As shown, a method for preparing carbon fiber grade dimethyl sulfoxide includes:

[0074] Step S1: Industrial-grade dimethyl sulfoxide is fed into a filter tower for filtration to remove insoluble impurities and obtain primary purified dimethyl sulfoxide.

[0075] Step S2: The column chromatography column is filled with zwitterionic exchange resin. Before use, the zwitterionic exchange resin column is alternately rinsed with 2% hydrochloric acid aqueous solution and 2% sodium chloride solution, and then soaked in dimethyl sulfoxide aqueous solution (water and dimethyl sulfoxide mass ratio of 1:6) for 12 h. The primary purified dimethyl sulfoxide is introduced into the column chromatography column at a flow rate of 0.5 BV / h. Through column chromatography purification, acidic substances and metal ions are removed to obtain secondary purified dimethyl sulfoxide.

[0076] Step S3: Secondary purified dimethyl sulfoxide is distilled at 120℃ for 10 min to remove water, and then cooled to 10℃ at a rate of 5℃ / h, and then cooled to -5℃ at a rate of 5℃ / h to remove soluble impurities, thus obtaining intermediate purified dimethyl sulfoxide.

[0077] Step S4: Add the intermediate purified dimethyl sulfoxide into the stripping device at a rate of 0.1 L / min. m 3 Nitrogen gas is introduced at a rate of 100% to strip volatile impurities and obtain carbon fiber grade dimethyl sulfoxide.

[0078] Example 5

[0079] like Figure 2 As shown, a method for preparing carbon fiber grade dimethyl sulfoxide includes:

[0080] Step S1: Industrial-grade dimethyl sulfoxide is fed into a filter tower for filtration to remove insoluble impurities and obtain primary purified dimethyl sulfoxide.

[0081] Step S2: The column chromatography column is filled with zwitterionic exchange resin. Before use, the zwitterionic exchange resin column is alternately rinsed with 2% hydrochloric acid aqueous solution and 2% sodium chloride solution, and then soaked in dimethyl sulfoxide aqueous solution (water to dimethyl sulfoxide mass ratio of 1:7.5) for 11 h. The primary purified dimethyl sulfoxide is introduced into the column chromatography column at a flow rate of 1 BV / h. Through column chromatography purification, acidic substances and metal ions are removed to obtain secondary purified dimethyl sulfoxide.

[0082] Step S3: Secondary purified dimethyl sulfoxide is distilled at 130℃ for 5 min to remove water, and then cooled to 10℃ at a rate of 10℃ / h, and then cooled to -5℃ at a rate of 5℃ / h to remove soluble impurities, thus obtaining intermediate purified dimethyl sulfoxide.

[0083] Step S4: Add the intermediate purified dimethyl sulfoxide into the stripping device at a rate of 0.5 L / min. m 3 Air is introduced at a rate of 100% to remove volatile impurities and obtain carbon fiber grade dimethyl sulfoxide.

[0084] Example 6

[0085] like Figure 2 As shown, a method for preparing carbon fiber grade dimethyl sulfoxide includes:

[0086] Step S1: Industrial-grade dimethyl sulfoxide is fed into a filter tower for filtration to remove insoluble impurities and obtain primary purified dimethyl sulfoxide.

[0087] Step S2: The column chromatography column is filled with zwitterionic exchange resin. Before use, the zwitterionic exchange resin column is alternately rinsed with 2% hydrochloric acid aqueous solution and 2% sodium chloride solution, and then soaked in dimethyl sulfoxide aqueous solution (water and dimethyl sulfoxide mass ratio of 1:9) for 10 h. The primary purified dimethyl sulfoxide is introduced into the column chromatography column at a flow rate of 2 BV / h. Through column chromatography purification, acidic substances and metal ions are removed to obtain secondary purified dimethyl sulfoxide.

[0088] Step S3: Secondary purified dimethyl sulfoxide is distilled at 150℃ for 5 min to remove water, and then cooled to 5℃ at a rate of 10℃ / h, and then cooled to -10℃ at a rate of 5℃ / h to remove soluble impurities, thus obtaining intermediate purified dimethyl sulfoxide.

[0089] Step S4: Add the intermediate purified dimethyl sulfoxide into the stripping device at a rate of 1 L / min. m 3 Nitrogen gas is introduced at a rate of 100% to strip volatile impurities and obtain carbon fiber grade dimethyl sulfoxide.

[0090] Comparative Example 1

[0091] A method for preparing carbon fiber grade dimethyl sulfoxide, which differs from Example 6 in that industrial grade dimethyl sulfoxide is purified only by distillation.

[0092] Comparative Example 2

[0093] A method for preparing carbon fiber grade dimethyl sulfoxide, which differs from Example 6 in that the primary purified dimethyl sulfoxide is purified by column chromatography using a single cation exchange resin and a single anion exchange resin in series for purification.

[0094] (1) Acidity determination: Weigh 50 g of sample, accurate to 0.01 g, and place it in an Erlenmeyer flask containing 100 mL of water. Add 2-3 drops of phenolphthalein indicator solution and titrate with potassium hydroxide standard solution until a pink color appears and remains unchanged for 1 min. The free acid in the sample undergoes a neutralization reaction with potassium hydroxide. The free acid value can be calculated based on the amount of potassium hydroxide standard solution consumed.

[0095] (2) Moisture content determination: The moisture content in carbon fiber grade dimethyl sulfoxide was determined by the Karl Fischer method (GB / T 6283-2008, Determination of moisture content in chemical products by Karl Fischer method (general method)).

[0096] (3) Determination of metal ion content: Inductively coupled plasma atomic emission spectrometry is used. Under the selected working conditions, the sample is converted into an aerosol by an atomizer and introduced into the inductively coupled plasma by argon gas. The dimethyl sulfoxide component in the sample evaporates, the metal element is atomized, excited to a high energy state, and emits the characteristic spectrum of the metal element. The intensity of the characteristic spectral line is detected by a spectrometer, and the content of the target metal ion in the sample is calculated by combining the concentration-intensity standard curve.

[0097] (4) Absorbance determination: Take an appropriate amount of carbon fiber grade dimethyl sulfoxide sample to be tested, pass dry nitrogen gas for 15 min to remove moisture, use deionized water as solvent, and measure the absorbance at 270~400 nm using a UV-Vis spectrophotometer, with deionized water as the blank control.

[0098] Table 1. Results of determination of purity, acidity, water content and total metal ion content of carbon fiber grade dimethyl sulfoxide

[0099]

[0100] Note: Acidity, the volume of 0.01 mol / L potassium hydroxide titrant consumed shall not exceed 1.0 mL; non-volatile residues shall not exceed 0.001%; ​​water content shall not exceed 0.1%; total metal ions shall not exceed 1 ppm.

[0101] According to the data in Table 1, the carbon fiber grade dimethyl sulfoxide prepared by the methods in Examples 4 to 6 all had a purity of over 99%, a water content of less than 0.1%, and a total metal ion content of less than 1 ppm. In Comparative Example 1, the industrial grade dimethyl sulfoxide was only distilled, i.e., only dehydrated and some volatile impurities were removed, but soluble impurities, acidic impurities, and metal ions were still present in large quantities. Therefore, the total metal ion content was >2 ppm, and the purity was the lowest.

[0102] In Comparative Example 2, the primary purified dimethyl sulfoxide (DMSO) was purified by column chromatography using a single cation exchange resin and a single anion exchange resin in series. The resulting carbon fiber-grade DMSO contained a total metal ion concentration >1 ppm but <2 ppm, with acidity and water content similar to the example. The series purification with a single resin is complex, as the two steps involve different operations and parameters, resulting in a cumbersome process and a lower recovery rate. Furthermore, the two resin packings use different eluents for activation before use, requiring neutralization of the eluent after series purification, which may introduce new metal impurities. Therefore, the carbon fiber-grade DMSO obtained in Comparative Example 2 contained a relatively high amount of residual metal ions.

[0103] Experiments have shown that by adopting this technical solution, which involves filtration and column chromatography followed by distillation, crystallization, and gas stripping, insoluble and ionic impurities are removed first, then volatile and soluble impurities are removed. This staged impurity removal avoids cross-contamination, protects the equipment used for distillation, crystallization, and gas extraction, and ensures thorough impurity removal, resulting in high-purity dimethyl sulfoxide.

[0104] Table 2 Absorbance data of carbon fiber grade dimethyl sulfoxide

[0105]

[0106] Note: Absorbance at 270 nm ≤ 1.00, absorbance at 280 nm ≤ 0.30, absorbance at 295 nm ≤ 0.10, absorbance at 330 nm ≤ 0.02, absorbance at 350~400 nm ≤ 0.01.

[0107] According to the data in Table 2, the absorbance of the dimethyl sulfoxide prepared in Examples 4-6 and Comparative Examples 1 and 2 at 270 nm was all less than 1.00. The experiment proved that the dimethyl sulfoxide prepared in Examples 4-6 and Comparative Examples 1 and 2 contained very little aromatic or unsaturated organic compounds with strong ultraviolet absorption.

[0108] The dimethyl sulfoxides prepared in Examples 4 to 6 all had absorbances below 0.30 at 280 nm, while the dimethyl sulfoxides prepared in Comparative Examples 1 and 2 all had absorbances above 0.30 at 280 nm. The experiment shows that the dimethyl sulfoxides prepared in Examples 4 to 6 contained very few nitrogen-containing heterocyclic compounds, while the dimethyl sulfoxides prepared in Comparative Examples 1 and 2 still contained nitrogen-containing heterocyclic compound impurities.

[0109] The dimethyl sulfoxides prepared in Examples 4-6 all had absorbance below 0.10 at 295 nm, while the dimethyl sulfoxides prepared in Comparative Examples 1 and 2 all had absorbance above 0.10 at 295 nm. The experiment shows that the dimethyl sulfoxides prepared in Examples 4-6 contain only a very small amount of highly conjugated substances such as polycyclic aromatic hydrocarbons, while the dimethyl sulfoxides prepared in Comparative Examples 1 and 2 have significantly higher impurity contents of highly conjugated substances such as polycyclic aromatic hydrocarbons than those prepared in Examples 4-6.

[0110] The dimethyl sulfoxides prepared in Examples 4 to 6 all had absorbances below 0.02 at 330 nm, while the dimethyl sulfoxides prepared in Comparative Examples 1 and 2 all had absorbances above 0.02 at 330 nm. The experiment shows that the dimethyl sulfoxides prepared in Examples 4 to 6 have much lower content of impurities such as metal complexes and polymers than those prepared in Comparative Examples 1 and 2.

[0111] The dimethyl sulfoxides prepared in Examples 4 to 6 all had absorbance of less than 0.01 in the 350–400 nm wavelength range. The dimethyl sulfoxides prepared in Comparative Examples 1 and 2 had significantly higher absorbance in this wavelength range than those prepared in Examples 4 to 6. This region is the visible light region, and there was no significant absorption in this wavelength range, which proves that the dimethyl sulfoxide has high purity. The experiment shows that the dimethyl sulfoxides prepared in Examples 4 to 6 have significantly higher purity than those prepared in Comparative Examples 1 and 2.

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of carbon fiber grade dimethyl sulfoxide, characterized by, include: Step S1: Industrial-grade dimethyl sulfoxide is fed into a filter tower for filtration to remove insoluble impurities and obtain primary purified dimethyl sulfoxide. Step S2: The primary purified dimethyl sulfoxide enters the column chromatography column and is purified by column chromatography to remove acidic substances and metal ions, thereby obtaining secondary purified dimethyl sulfoxide. Step S3: Primary purified dimethyl sulfoxide is dehydrated by distillation and soluble impurities are removed by cooling crystallization to obtain intermediate purified dimethyl sulfoxide. Step S4: Put the intermediate purified dimethyl sulfoxide into the gas stripping device, introduce a gas source for gas stripping, remove volatile impurities, and obtain carbon fiber grade dimethyl sulfoxide. The method for preparing the column chromatography column filled with zwitterionic ion exchange resin includes: Step A1: Disperse γ-Fe2O3 magnetic nanoparticles in an ethanol aqueous solution, adjust the pH to 4-5 with acetic acid, add 3-(triethoxysilyl)-N-vinylpropylamine, and react under inert gas protection to obtain organosilicon-modified γ-Fe2O3; Step A2: Organosilicon-modified γ-Fe2O3, styrene and divinylbenzene are dispersed in ethanol to form a uniform dispersion. The dispersant is dissolved in water to obtain an aqueous phase. The dispersion is added to the aqueous phase, and an initiator is added to react and obtain composite microspheres. Step A3: Disperse the composite microspheres in dichloromethane, add pyridine and acylation reagent, and react to obtain acetylated composite microspheres; Step A4: Disperse the acetylated composite microspheres in ethanol, add an amination reagent, and after the first reaction, obtain imine-treated composite microspheres. Add sodium borohydride and after the second reaction, obtain amination-treated composite microspheres. Step A5: Disperse the amination composite microspheres in ethanol, adjust the pH to 8-10, add carbon disulfide, and react to obtain dithiocarbamate composite microspheres. Step A6: Disperse dithiocarbamate composite microspheres in dichloromethane, add formaldehyde, concentrated hydrochloric acid and aluminum trichloride, and after the first reaction, obtain an intermediate. Adjust the pH to 10, add trimethylamine aqueous solution, and after the second reaction, obtain zwitterionic exchange resin. In step A3, the acylation reagent is any one or more of acetic anhydride and acetyl chloride; the reaction temperature is 60~90℃, and the reaction time is 4~6 h; the mass ratio of the composite microspheres, solvent, acylation reagent, and pyridine is 1:(3~5):(0.1~0.3):(0.003~0.01). In step A4, the amination reagent is any one or more of ethylenediamine and pentanediamine.

2. The process for the preparation of carbon fiber grade dimethyl sulfoxide according to claim 1, characterized in that, In step A1, the mass ratio of ethanol to water in the ethanol-water solution is 1:(1~1.5); the mass ratio of γ-Fe2O3 magnetic nanoparticles, ethanol-water solution, and 3-(triethoxysilyl)-N-vinylpropylamine is 1:(10~15):(0.15~0.35); the reaction temperature is 50~60℃, and the reaction time is 8~10 h.

3. The process for the preparation of carbon fiber grade dimethyl sulfoxide as claimed in claim 1 wherein, In the step A2, the initiator is any one or more of benzoyl peroxide and azobisisobutyronitrile; the dispersant is any one or more of polyvinyl alcohol, polyethylene glycol and polyvinylpyrrolidone; the reaction temperature is 60-80℃, and the reaction time is 4-6 h; the mass ratio of the silicone-modified γ-Fe2O3, styrene, p-divinylbenzene and ethanol is 1:(1.5-3.5):(1.15-2.5):(5-10); the mass ratio of the water and the dispersant is 1:(0.01-0.03); and the mass ratio of the aqueous phase, the dispersion and the initiator is 1:(0.1-0.5):(0.005-0.012).

4. The process for the preparation of carbon fiber grade dimethyl sulfoxide as claimed in claim 1, wherein, In the step A4, the temperature of the first reaction is 50-70℃, and the first reaction time is 3-6 h; the second reaction time is 1-2 h; and the mass ratio of the acetylated composite microspheres, ethanol, aminating reagent and sodium borohydride is 1:(5-10):(1.2-1.5):(0.1-0.3).

5. The process for the preparation of carbon fiber grade dimethyl sulfoxide as claimed in claim 1 wherein, In the step A5, the reaction time is 2-4 h; the mass ratio of the aminated composite microspheres, ethanol and carbon disulfide is 1:(3-5):(1.5-2); in the step A6, the temperature of the first reaction is 40-60℃, and the first reaction time is 3-5 h; the second reaction time is 4-6 h; in the aqueous trimethylamine solution, the mass ratio of trimethylamine and water is 1:(3-5); and the mass ratio of the dithiocarbamic acidized composite microspheres, solvent, formaldehyde, concentrated hydrochloric acid, aluminum trichloride, aqueous trimethylamine solution is 1:(5-10):(0.005-0.011):(0.001-0.0015):(0.005-0.0075):(0.75-1.2).

6. The process for the preparation of carbon fiber grade dimethyl sulfoxide as claimed in claim 1, wherein, In the step S2, the column chromatography tower is filled with a zwitterionic exchange resin, and the flow rate of the primary purified dimethyl sulfoxide into the column chromatography tower is 0.5-2 BV / h; before use, the zwitterionic exchange resin is alternately flushed with 2% hydrochloric acid aqueous solution and 2% sodium chloride solution, and then soaked in dimethyl sulfoxide aqueous solution for 10-12 h, and the mass ratio of water and dimethyl sulfoxide is 1:(6-9).

7. The process for the preparation of carbon fiber grade dimethyl sulfoxide as claimed in claim 1, wherein, In the step S3, the distillation step is: heating to 120-150℃ under normal pressure for 5-10 min; and the cooling crystallization operation is: cooling at a rate of 10-15℃ / h to 5-10℃, and then cooling at a rate of 5-10℃ / h to -5--10℃.

8. The process for the preparation of carbon fiber grade dimethyl sulfoxide as claimed in claim 1, wherein, In the step S4, the gas source is any one or more of nitrogen and air; the flow rate of the gas source is 0.1-1 L / min·m 3 feed liquid.

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