A method for purifying chromatographically pure 1,4-dioxane

Abstract

This invention belongs to the field of chemical reagents and relates to a purification method for chromatographically pure 1,4-dioxane. The invention is scientifically and rationally designed, using 99.5% pure 1,4-dioxane as raw material. Impurities are removed by adsorption using a chitosan-graphene oxide composite adsorbent. Ultraviolet light at a wavelength of 235 nm is used to irradiate the oxidant, generating hydroxyl radicals. The strong oxidizing properties of these hydroxyl radicals are used to oxidize and decompose organic impurities. The resulting 1,4-dioxane is produced through drying, dehydration, and membrane filtration, achieving the required chromatographically pure 1,4-dioxane quality and application standards. Compared with existing methods, this method produces a product of superior quality, better batch stability, and a recovery rate exceeding 93%, enabling industrial-scale production.

Description

Technical Field

[0001] This invention belongs to the field of chemical reagents and relates to purification technology, especially a purification method for chromatographically pure 1,4-dioxane. Background Technology

[0002] 1,4-Dioxane, also known as 1,4-dioxane, has two ether bond oxygen atoms in its molecule. It is miscible with water and most organic solvents. It is mainly used as a solvent for nitrocellulose, cellulose resin, and oil-soluble dyes, and is widely used in pharmaceuticals, petrochemicals, paint manufacturing, and other industries.

[0003] The existing technology for producing 1,4-dioxane mainly involves the dehydration of ethylene glycol under sulfuric acid catalysis, with ethylene oxide being a commonly used catalyst. However, this process generates numerous impurities, such as acids, ethers, aldehydes, and alcohols. Furthermore, conventional processing methods cannot achieve the quality standard of chromatographically pure 1,4-dioxane. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a purification method for chromatographically pure 1,4-dioxane. The 1,4-dioxane prepared by this method can remove aldehydes, alcohols, acids, and ethers, which are difficult to remove and present in low concentrations, thus achieving the chromatographically pure 1,4-dioxane standard and application requirements. The 1,4-dioxane product obtained through this purification process has a purity greater than 99.95% and a moisture content below 0.005%.

[0005] The technical problem solved by this invention is achieved through the following technical solution:

[0006] A purification method for chromatographically pure 1,4-dioxane, the specific steps of which are as follows:

[0007] (1) Oxidation: 95% pure 1,4-dioxane raw material is fed into a UV-irradiated reactor, and hydrogen peroxide liquid oxidant is added at 1.0%-2.0% of the mass ratio of 1,4-dioxane raw material. The reaction is carried out by irradiation with 235nm UV light for 0.5-1.0h.

[0008] (2) Adsorption: The oxidized 1,4-dioxane sample solution was injected into the chitosan-graphene oxide composite material for adsorption and impurity removal;

[0009] (3) Drying: The 1,4-dioxane solution after adsorption in the above steps is dried by passing it through a drying column;

[0010] (4) Distillation: The dried 1,4-dioxane sample solution is fed into a distillation kettle, and 0.5-1.5% calcium hydride is added according to the mass ratio of the 1,4-dioxane sample solution. The temperature inside the kettle is controlled at 110℃-150℃ using heat transfer oil, and the top temperature of the distillation kettle is 95℃-100℃ to remove light components, low-boiling-point ethers and peroxide impurities.

[0011] (5) Filtration: The 1,4-dioxane sample solution, after preliminary drying and deetherification, is injected into the filter membrane module for adsorption and filtration;

[0012] (6) Vaporization: The 1,4-dioxane sample solution that has been filtered and purified by membrane filtration is pumped into the vaporization distillation kettle, heated by heat transfer oil, and the heating temperature of the distillation kettle is controlled at 110℃-150℃ and the bottom temperature of the distillation kettle is 101.1-101.5℃. The gaseous 1,4-dioxane in the tower kettle is introduced into the pervaporation membrane module for the next step of processing.

[0013] (7) Dehydration treatment: The pervaporation membrane module described in step (6) above is subjected to decompression treatment using a vacuum pump, and the chromatographically pure 1,4-dioxane product is obtained after condensation by the condenser set in the pervaporation membrane module.

[0014] Furthermore, the preparation method of the chitosan-graphene oxide composite material includes: adding 20g of graphene oxide to 10L of water, ultrasonically dispersing for 120min to obtain a graphene oxide suspension, then adding 10g of chitosan to 3% glacial acetic acid, stirring until dissolved, adding to the above graphene oxide suspension, ultrasonicating the mixture for another 60min, adding 500mL of epichlorohydrin, stirring at 50℃ for 1h, adding sodium hydroxide to adjust the pH to 11, and continuing to stir for another 4h. After centrifugation, the product is repeatedly washed with water until the supernatant is neutral, centrifuged again, and the solid product is vacuum dried at 60℃ to obtain the chitosan-graphene oxide composite material.

[0015] Moreover, in the drying step (3), the desiccant is anhydrous calcium oxide, the volume of anhydrous calcium oxide is 2 / 3 of the drying column, the flow rate of the desiccant is 50-100 mL / min, and the drying column is 1.0 m high and 10 cm in diameter.

[0016] Moreover, the membrane material in the filter membrane assembly described in step (5) is PF5A ion-reinforced composite membrane material, which is phenolic resin, with a membrane diameter of 150 mm and a membrane thickness of 0.05 μm.

[0017] Furthermore, the membrane material in the pervaporation membrane module is a polydimethylsiloxane membrane material with a thickness of 0.5 μm.

[0018] The advantages and positive effects of this invention are:

[0019] 1. The method of this invention utilizes a composite adsorbent material synthesized from chitosan and graphene oxide via chemical cross-linking. Graphene oxide, with its single-atom thickness and honeycomb structure, possesses a very high specific surface area. The composite material, after composite modification, exhibits significantly increased pore size, increased specific surface area, and enhanced polarity. The modified graphene material surface contains numerous oxygen-containing functional groups, which enhance its selective adsorption of the oxidation products of impurities in 1,4-dioxane. Extensive experiments demonstrate that this adsorbent material is highly effective in removing carboxyl acids. Furthermore, due to the abundance of hydroxyl, carboxyl, and epoxy radicals in both chitosan and graphene oxide, the composite adsorbent material combines the advantages of both materials, exhibiting good adsorption performance for oxidized carboxylic acid impurities.

[0020] 2. The method of this invention employs ultraviolet photocatalytic oxidation technology, utilizing ultraviolet light at a specific wavelength to irradiate the oxidant, generating hydroxyl radicals. The strong oxidizing power of these hydroxyl radicals is used to oxidize and decompose organic impurities, and to oxidize alcohols and aldehydes that affect ultraviolet absorption. This method offers advantages such as high oxidation efficiency, fast rate, and short cycle time. Compared with traditional oxidants such as concentrated sulfuric acid and potassium permanganate, it has advantages such as less environmental pollution, higher safety, and better oxidation effect. This oxidation technology overcomes the shortcomings of conventional oxidants, such as limited oxidizing power and incomplete oxidation.

[0021] 3. The method of this invention employs membrane separation technology to dehydrate and remove impurities from 1,4-dioxane products, offering significant advantages such as high efficiency, energy saving, environmental friendliness, and ease of operation. This invention utilizes two different membrane materials; the dehydration vaporization membrane boasts high flux and high stability, allowing the raw material to contact the membrane in the form of steam, eliminating the influence of solid impurities and greatly extending the membrane's lifespan. Furthermore, the use of membrane materials for impurity removal instead of extractive distillation significantly reduces energy consumption, a major highlight. This method features high separation efficiency, simple operation, no pollution, and low energy consumption.

[0022] 4. This invention is scientifically and rationally designed. Using 1,4-dioxane with a purity of 99.5% as raw material, it removes impurities through adsorption using a chitosan-graphene oxide composite adsorbent. Ultraviolet light at a wavelength of 235 nm is then used to irradiate the oxidant, generating hydroxyl radicals. These hydroxyl radicals, with their strong oxidizing properties, oxidize and decompose organic impurities. The resulting 1,4-dioxane is produced through drying, dehydration, and membrane filtration, achieving chromatographic purity and meeting application requirements. Compared to existing methods, this method produces a product with superior quality, better batch stability, and a recovery rate exceeding 93%, enabling industrial-scale production. Detailed Implementation

[0023] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0024] A purification method for chromatographically pure 1,4-dioxane, the specific steps of which are as follows:

[0025] (1) Oxidation: 95% pure 1,4-dioxane raw material is fed into a UV-irradiated reactor, and hydrogen peroxide liquid oxidant is added at 1.0%-2.0% of the mass ratio of 1,4-dioxane raw material. The reaction is carried out by irradiation with 235nm UV light for 0.5-1.0h.

[0026] (2) Adsorption: The oxidized 1,4-dioxane sample solution was injected into the chitosan-graphene oxide composite material for adsorption and impurity removal. The preparation method of the chitosan-graphene oxide composite material is as follows: 20g of graphene oxide is added to 10L of water and ultrasonically dispersed for 120min to obtain a graphene oxide suspension. Then, 10g of chitosan is added to 3% glacial acetic acid and stirred until dissolved. Then, it is added to the above graphene oxide suspension. The mixture is ultrasonically stirred for 60min. 500mL of epichlorohydrin is added and stirred at 50℃ for 1h. Then, a certain amount of sodium hydroxide is added to adjust the pH to 11 and stirred for 4h. After centrifugation, the product is washed repeatedly with water until the supernatant is neutral. After centrifugation, the solid product is vacuum dried at 60℃ to obtain the chitosan-graphene oxide composite material.

[0027] (3) Drying: The 1,4-dioxane solution after adsorption in the above steps is dried by passing it through a drying column at a flow rate of 50-100 mL / min. The drying column is 1.0 m high and 10 cm in diameter. Anhydrous calcium oxide is used as a desiccant inside the column, and the desiccant occupies 2 / 3 of the drying column. The calcium oxide used is analytical grade calcium oxide.

[0028] (4) Distillation: The dried 1,4-dioxane sample solution is fed into a distillation kettle, and 0.5-1.5% calcium hydride is added according to the mass ratio of the 1,4-dioxane sample solution. The temperature inside the kettle is controlled at 110℃-150℃ using heat transfer oil, and the top temperature of the distillation kettle is 95℃-100℃ to remove light components, low-boiling-point ethers and peroxide impurities.

[0029] (5) Filtration: The 1,4-dioxane sample solution after preliminary drying and deetherification is fed into a filter membrane module for adsorption filtration. The membrane material in the filter membrane module is PF5A ion composite membrane material, which has good permeability and selectivity for 1,4-dioxane. During the filtration process, 1,4-dioxane can pass through the membrane material, while the macromolecular acid impurities in the 1,4-dioxane sample solution cannot pass through. The method of removing impurities from the 1,4-dioxane sample solution is very effective.

[0030] PF5A ion exchange composite membrane material is made of phenolic resin, a thermosetting plastic membrane with good resistance to deformation, falling between that of fiber and rubber. It is composed of synthetic resin, fillers, stabilizers, and other additives. The membrane thickness is 0.05 μm, and the membrane material diameter is 150 mm. This membrane material has good acid resistance and good permeability and selectivity to 1,4-dioxane. 1,4-dioxane can pass through this membrane material, while large molecular weight acid impurities generated by oxidation cannot pass through.

[0031] (6) Vaporization: The 1,4-dioxane sample solution that has been filtered and purified by membrane filtration is pumped into the vaporization distillation kettle, heated by heat transfer oil, and the heating temperature of the distillation kettle is controlled at 110℃-150℃ and the bottom temperature of the distillation kettle is 101.1-101.5℃. The gaseous 1,4-dioxane in the tower kettle is introduced into the pervaporation membrane module for the next step of processing.

[0032] (7) Dehydration treatment: A vacuum pump is used inside the membrane module to reduce pressure, creating a pressure difference across the membrane. Smaller water molecules can permeate and vaporize the membrane material, while larger 1,4-dioxane molecules cannot pass through. The 1,4-dioxane product is condensed by a condenser inside the membrane module to obtain chromatographically pure 1,4-dioxane. The membrane material is polydimethylsiloxane, which has good hydrophobicity. The main chain is composed of repeating silicon-oxygen bonds, and the chains have a large free volume, which is conducive to the preferential diffusion of organic matter in the membrane. This achieves the separation of 1,4-dioxane from water.

[0033] Polydimethylsiloxane (PDMS) membranes are organosilicon materials with excellent heat resistance and chemical corrosion resistance. They remain stable in high-temperature, strong acid, and strong alkali environments. With a thickness of 0.5 μm, these membranes exhibit high water vapor permeability and selectivity. The membrane material also possesses good hydrophobicity, with its main chain composed of repeating silicon-oxygen bonds and a large free volume between the chains, facilitating preferential diffusion of organic matter within the membrane. While smaller water molecules can permeate and vaporize the membrane, larger 1,4-dioxane molecules cannot pass through.

[0034] The method of this invention uses chitosan-graphene oxide composite adsorbent material to remove impurities. This composite material, through modification of graphene oxide, reduces the aggregation of graphene oxide, increases the specific surface area, and greatly improves its adsorption performance.

[0035] This invention utilizes ultraviolet light at a wavelength of 235 nm to irradiate the oxidant, generating hydroxyl radicals. The strong oxidizing properties of these hydroxyl radicals are then used to oxidize and decompose organic impurities. This method offers advantages such as high oxidation efficiency, rapid rate, and short cycle time.

[0036] The 1,4-dioxane prepared by the method of this invention can remove aldehydes, alcohols, acids, and ethers that are difficult to remove and have low content, achieving the chromatographic purity of 1,4-dioxane and meeting application requirements. The 1,4-dioxane product obtained by this purification process has a purity greater than 99.95% and a moisture content less than 0.005%. Example 1

[0037] A purification method for chromatographically pure 1,4-dioxane, the specific purification steps of which are as follows:

[0038] 1) Oxidation: 1,4-Dioxane raw material is fed into a UV-irradiated reactor, and hydrogen peroxide liquid oxidant is added at 1.0%-2.0% of the mass ratio of 1,4-dioxane raw material. The reaction is carried out by irradiation with 235nm UV light for 0.5-1.0h.

[0039] 2) Adsorption: The oxidized 1,4-dioxane sample solution was injected into the chitosan-graphene oxide composite material for adsorption and impurity removal, and the adsorption rate was controlled at 100-500 mL / min.

[0040] 3) Drying: The 1,4-dioxane solution after adsorption in the above steps is dried by passing it through a drying column at a flow rate of 50-100 mL / min.

[0041] 4) Distillation: Pour the dried 1,4-dioxane sample solution into a distillation vessel, add 0.5-1.5% calcium hydride according to the mass ratio of the 1,4-dioxane sample solution, control the temperature inside the vessel at 110℃-150℃ using heat transfer oil, and keep the top temperature of the distillation vessel at 95℃-100℃; remove light components, low-boiling-point ethers and peroxide impurities.

[0042] 5) Filtration: The 1,4-dioxane sample solution, after preliminary drying and deetherification, is fed into the filter membrane module for adsorption and filtration.

[0043] 6) Vaporization: The 1,4-dioxane sample solution, after being filtered and purified by membrane filtration, is pumped into a vaporization distillation vessel. Heat is applied using heat transfer oil, and the heating temperature of the distillation vessel is controlled at 110℃-150℃, while the bottom temperature of the distillation vessel is 101.1-101.5℃. The vapor phase of 1,4-dioxane in the vessel is then introduced into the pervaporation membrane module for further processing.

[0044] 7) Dehydration treatment: A vacuum pump is used to reduce the pressure inside the membrane module, creating a pressure difference across the membrane. Smaller water molecules can permeate and vaporize the membrane material, while larger 1,4-dioxane molecules cannot pass through the membrane material. The 1,4-dioxane product is obtained by condensation through a condenser inside the membrane module.

[0045] 8) Nitrogen Filling: The product is automatically filled with nitrogen to obtain 4L of chromatographic 1,4-dioxane. The purity of the obtained product is 99.96%, and the moisture content is 0.0035%. All test results meet the requirements. This product can meet the needs of customers requiring chromatographically pure 1,4-dioxane. The test results of this product are shown in Table 1.

[0046]

[0047] Example 2

[0048] A purification method for chromatographically pure 1,4-dioxane, the specific purification steps are as follows:

[0049] 1) Oxidation: 1,4-Dioxane raw material is fed into a UV-irradiated reactor, and hydrogen peroxide liquid oxidant is added at 1.0%-1.5% of the mass ratio of 1,4-dioxane raw material. The reaction is carried out by irradiation with 235nm UV light for 0.5-1.0h.

[0050] 2) Adsorption: The oxidized 1,4-dioxane sample solution was injected into the chitosan-graphene oxide composite material for adsorption and impurity removal, and the adsorption rate was controlled at 100-500 mL / min.

[0051] 3) Drying: The 1,4-dioxane solution after adsorption in the above steps is dried by passing it through a drying column at a flow rate of 80-100 mL / min.

[0052] 4) Distillation: Pour the dried 1,4-dioxane sample solution into a distillation vessel, add 0.5-1.0% calcium hydride according to the mass ratio of the 1,4-dioxane sample solution, and use heat transfer oil to control the temperature inside the vessel at 110℃-150℃, and the top temperature of the distillation vessel at 95℃-100℃.

[0053] 5) Filtration: The 1,4-dioxane sample solution, after preliminary drying and deetherification, is fed into the filter membrane module for adsorption and filtration.

[0054] 6) Vaporization: The 1,4-dioxane sample solution, after being filtered and purified by membrane filtration, is pumped into a vaporization distillation vessel. Heat is applied using heat transfer oil, and the heating temperature of the distillation vessel is controlled at 110℃-150℃, while the bottom temperature of the distillation vessel is 101.1-101.5℃. The vapor phase of 1,4-dioxane in the vessel is then introduced into the pervaporation membrane module for further processing.

[0055] 7) Dehydration treatment: A vacuum pump is used to reduce the pressure inside the membrane module, creating a pressure difference across the membrane. Smaller water molecules can permeate and vaporize the membrane material, while larger 1,4-dioxane molecules cannot pass through the membrane material. The 1,4-dioxane product is obtained by condensation through a condenser inside the membrane module.

[0056] 8) Nitrogen-filled filling: After nitrogen filling, the product is filled to obtain 4L of chromatographic 1,4-dioxane. The purity of the obtained product is 99.95%, and the moisture content is 0.0030%. All test results meet the requirements. This product can meet the needs of customers requiring chromatographically pure 1,4-dioxane. The test results of this product are shown in Table 2.

[0057]

[0058] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for purifying chromatographically pure 1,4-dioxane, characterized by: The specific method steps are as follows: (1) oxidation: the 1,4-dioxane raw material with a purity of 95% is put into the ultraviolet irradiation reactor, and 1.0%-2.0% of the 1,4-dioxane raw material is added according to the mass ratio of hydrogen peroxide liquid oxidant, and the reaction is irradiated for 0.5-1.0h by using 235nm ultraviolet light; (2) adsorption: the oxidized 1,4-dioxane sample solution is put into the chitosan-oxidized graphene composite material to remove impurities; (3) drying: the 1,4-dioxane solution after adsorption in the above step is dried by a drying column; (4) distillation: the dried 1,4-dioxane sample solution is put into a distillation kettle, 0.5-1.5% of calcium hydride is added according to the mass ratio of the 1,4-dioxane sample solution, the temperature in the kettle is controlled at 110-150℃ by using conductive oil, the top temperature of the rectification kettle is 95-100℃, and light components, low-boiling-point ethers and peroxide impurities are removed; (5) filtration: the 1,4-dioxane sample solution after preliminary drying and ether removal is put into a filtration membrane assembly for adsorption and filtration; (6) vaporization: the 1,4-dioxane sample solution after membrane filtration and impurity removal is put into a vaporization distillation kettle, heated by using conductive oil, and the heating temperature of the rectification kettle is controlled at 110-150℃, the bottom temperature of the rectification kettle is 101.1-101.5℃, and the gas phase 1,4-dioxane in the kettle is introduced into a permeation gasification membrane assembly for further processing; (7) dehydration treatment: the permeation gasification membrane assembly in step (6) is subjected to vacuum treatment by using a vacuum pump, and the chromatographically pure 1,4-dioxane product is obtained after condensation by a condenser arranged in the permeation gasification membrane assembly, The membrane material in the filtration membrane assembly in step (5) is PF5A ion composite membrane material, the PF5A ion composite membrane material is phenolic resin, the membrane material has a diameter of 150mm and a thickness of 0.05μm, The membrane material in the permeation gasification membrane assembly is polydimethylsiloxane membrane material, the polydimethylsiloxane membrane material has a thickness of 0.5μm, The preparation method of the chitosan-oxidized graphene composite material comprises the following steps: 20g of oxidized graphene is added to 10L of water, ultrasonic dispersion is performed for 120min to obtain an oxidized graphene suspension, 10g of chitosan is added to 3% of glacial acetic acid, stirring is performed until the chitosan is dissolved, then the above-mentioned oxidized graphene suspension is added, the mixed solution is continuously ultrasonically dispersed for 60min, 500mL of epoxy chloropropane is added, stirring is performed at 50℃ for 1h, sodium hydroxide is added, the pH value is adjusted to 11, and stirring is continuously performed for 4h, the product is centrifuged, washed with water until the supernatant is neutral, then centrifuged again, and the solid product is dried at 60℃ under vacuum to obtain the chitosan-oxidized graphene composite material.

2. The method of purifying 1,4-dioxane according to claim 1, wherein: The drying agent in step (3) is anhydrous calcium oxide, the filling volume of the anhydrous calcium oxide is 2 / 3 of the drying column, and the flow rate of the drying agent is 50-100mL / min.

3. The method of purifying 1,4-dioxane according to claim 2, wherein: The drying column has a height of 1.0m and a diameter of 10cm.

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