Purification method of caprolactone and finished caprolactone purified by the method

Abstract

The present application belongs to the technical field of caprolactone purification, and particularly relates to a caprolactone purification method and a finished caprolactone purified by the method. The method comprises the following steps: mixing a caprolactone-containing material to be purified with a first extractant to perform first extraction to obtain a first extraction material; removing oxides from the first extraction material to obtain a primary purified material; performing first concentration on the primary purified material to obtain a concentrated material; mixing the concentrated material with a second extractant to perform second extraction to obtain a second extraction material; mixing the second extraction material with a third extractant to perform third extraction to obtain a third extraction material; and performing second concentration on the third extraction material to obtain a finished caprolactone. The caprolactone purified by the purification method has the advantages of simple process and low equipment investment. The finished caprolactone has high yield, and the purity of the finished caprolactone is greatly improved compared with the existing process.

Description

Technical Field

[0001] This invention belongs to the field of caprolactone purification technology, specifically relating to a method for purifying caprolactone and the finished caprolactone product obtained by the method. Background Technology

[0002] Caprolactone is an important non-toxic organic synthetic intermediate and a reactive polar solvent. As a synthetic intermediate, caprolactone can be used to produce thermoplastic polycaprolactone, polycaprolactone polyols, caprolactone-lactide copolymers, caprolactone-type polyurethanes, and other fully biodegradable materials. As a solvent, it can dissolve a variety of polymers and is reactive. Caprolactone is widely used in the production of biodegradable plastics, medical polymer materials, synthetic leather, adhesives, coatings, and other products.

[0003] Currently, caprolactone is mainly purified worldwide through vacuum distillation. However, when preparing caprolactone, directly heating the crude product for vacuum distillation or distillation can lead to side reactions, generating more complex byproducts (such as 6-hydroxyhexanoic acid and adipic acid). Therefore, it is necessary to first purify the crude product to remove impurities and avoid these side reactions. However, when the purified product is subjected to vacuum distillation, caprolactone in the bottom of the column easily polymerizes to form oligomers, producing a brownish-black viscous liquid. Cyclohexanone is distilled off first, followed by caprolactone and the byproduct adipic acid, failing to achieve the desired purification effect.

[0004] CN203319903U employs a separation tower to separate and purify mixed acids and fats. The mixture of caprolactone and mixed acids is fed into the caprolactone separation tower via a conveying device. The temperature of the caprolactone separation tower is adjusted to 95°C and the pressure to -0.09MPa. The caprolactone vapor overflows from the caprolactone outlet on the separation tower and is recovered for later use.

[0005] CN109400574A discloses a method for purifying crude lactide, comprising the following steps: A) mixing crude lactide with a solvent at 60-150°C to obtain a mixed solution; wherein the solvent is selected from one or more of ε-caprolactone, δ-valerolactone and γ-valerolactone; B) cooling the mixed solution to crystallize, and centrifuging to obtain purified lactide.

[0006] While distillation can separate caprolactone, its process is lengthy, the equipment is complex, and the investment is large. In addition, other by-products are easily generated during the distillation process, and it can also cause the self-polymerization of caprolactone, ultimately resulting in low purity of the finished caprolactone, which is difficult to meet the needs of some industries.

[0007] Therefore, it is of great significance to develop a new process for the separation and purification of caprolactone that is safer, simpler, and produces a high purity finished product. Summary of the Invention

[0008] The purpose of this invention is to overcome the aforementioned technical problems in the prior art and provide a method for purifying caprolactone and the finished caprolactone product obtained by this method. The purification method of this invention not only has a simple process and low equipment investment, but also eliminates side reactions during the purification process. The finished caprolactone product not only has a high yield, but also exhibits a significantly improved purity compared to existing processes.

[0009] To achieve the above objectives, the first aspect of the present invention provides a method for purifying caprolactone, characterized in that the method comprises the following steps:

[0010] (1) The material to be purified containing caprolactone is mixed with the first extractant and subjected to the first extraction to obtain the first extract material;

[0011] (2) Remove oxides from the first extracted material to obtain the first purified material;

[0012] (3) The initially purified material is first concentrated to obtain concentrated material;

[0013] (4) The concentrated material is mixed with the second extractant and subjected to a second extraction to obtain the second extracted material;

[0014] (5) Mix the second extractant with the third extractant and perform a third extraction to obtain the third extractant;

[0015] (6) The third extract material is concentrated in the second stage to obtain the finished product caprolactone.

[0016] A second aspect of the present invention provides a finished product of caprolactone obtained by the above purification method.

[0017] Through the above technical solution, the present invention provides a method for purifying caprolactone and the finished caprolactone product obtained by the method, which achieves the following beneficial effects:

[0018] The method for purifying caprolactone in this invention not only simplifies the purification process but also significantly reduces investment in purification equipment, and no side reactions occur during the purification process. The resulting caprolactone product not only has a high yield but also a significantly improved purity.

[0019] As a preferred embodiment of the present invention, when the first extractant is selected from haloalkanes, and the mass ratio of caprolactone in the material to be purified to the first extractant is 1:5-8; and in conjunction with a specific type of second extractant as defined in the present invention, the water, C5-C content in the second extractant is adjusted... 12The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is within the range of 10-15:8-12:1; and the mass ratio of caprolactone to the third extractant in the second extractant is further adjusted to 1:8-12. This invention, by selecting three specific types of extractants and employing the above-mentioned ratios, leverages the synergistic effect between the components to obtain caprolactone products with yields not less than 83% and purity reaching 99%. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the purification method of the present invention;

[0021] Figure 2 The infrared spectra of caprolactone purified in Example 1 and standard caprolactone are shown.

[0022] Figure 3 The chromatogram of caprolactone purified in Example 1 is shown.

[0023] Figure 4 The image shows the GC-MS analysis results of caprolactone obtained from the purification in Example 1. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] To achieve the above objectives, the first aspect of the present invention provides a method for purifying caprolactone, characterized in that the method comprises the following steps:

[0026] (1) The material to be purified containing caprolactone is mixed with the first extractant and subjected to the first extraction to obtain the first extract material;

[0027] (2) Remove oxides from the first extracted material to obtain the first purified material;

[0028] (3) The initially purified material is first concentrated to obtain concentrated material;

[0029] (4) The concentrated material is mixed with the second extractant and subjected to a second extraction to obtain the second extracted material;

[0030] (5) Mix the second extractant with the third extractant and perform a third extraction to obtain the third extractant;

[0031] (6) The third extract material is concentrated in the second stage to obtain the finished product caprolactone.

[0032] According to the present invention, the first extractant is selected from at least one of haloalkanes, benzene compounds and halobenzenes.

[0033] According to the present invention, the first extractant is selected from at least one of chloroform, dichloromethane, dichloroethane, toluene, and chlorobenzene.

[0034] As a preferred technical solution in this invention, the first extractant is selected from chloroform, dichloromethane, and dichloroethane.

[0035] According to the present invention, the mass ratio of caprolactone to the first extractant in the material to be purified is 1:3-10.

[0036] Furthermore, the mass ratio of caprolactone to the first extractant in the material to be purified is 1:4-8.

[0037] According to the present invention, the first extraction is performed 2-5 times.

[0038] According to the present invention, the content of the oxide in the primary purified material is less than 100 ppm by weight.

[0039] In this invention, by controlling the content of oxides in the initial purified material to be less than 100 ppm, the purity of caprolactone can be improved, the separation cost can be reduced, and the oxidation of the extractant can be avoided, which would generate harmful substances and increase the separation cost.

[0040] In this invention, there are no particular limitations on the method for removing oxides from the initial purified material, as long as the oxide content in the initial purified material can be controlled to be less than 100 ppm. For example, a reducing agent can be used to remove oxides from the initial purified material. Preferably, the reducing agent is selected from at least one of sodium bisulfite, sulfurous acid, sodium sulfite, and ammonium sulfite. A solid reducing agent can be used directly, but a solution of the reducing agent is preferred to increase the mixing effect. The specific removal process is as follows: (a) adding a set amount of reducing agent to the first extracted material; (b) detecting the degree of oxide reduction; (c) repeating steps (a) and (b) until the oxides are removed.

[0041] Preferably, the method further includes cooling the first extract during the oxide removal process. The degree of oxide reduction can be detected using a detection instrument or an indicator; this invention does not impose any particular limitation. For example, after adding a predetermined amount of reducing agent, a small amount of liquid is taken out, and an indicator (10wt% potassium iodide and starch solution) is added to the taken-out solution. The phenomenon is observed; if the indicator turns black, it proves that hydrogen peroxide is still present in the system. This process is repeated until the indicator no longer changes color, indicating that the hydrogen peroxide has been completely removed, and the initially purified material is obtained.

[0042] According to the present invention, the first concentration is selected from at least one of evaporation concentration, rotary evaporation concentration and distillation concentration.

[0043] According to the present invention, the temperature of the first concentration is 50-100°C.

[0044] Furthermore, the temperature of the first concentration is 60-80°C.

[0045] In this invention, the concentration time is determined according to the concentration conditions. Taking a rotary evaporator as an example, the rotary evaporation is stopped when liquid no longer collects at the mouth of the flask on the rotary evaporator. Preferably, the first concentration time is 30-180 minutes.

[0046] Furthermore, the first concentration time is 40-60 minutes.

[0047] According to the present invention, the second extractant comprises water, C5-C 12 Hydrocarbon solvents and C2-C8 ester solvents.

[0048] Furthermore, the C5-C 12 The hydrocarbon solvent is selected from at least one of n-hexane, n-pentane, n-heptane, and cyclohexane.

[0049] Furthermore, the C2-C8 ester solvent is selected from at least one of ethyl acetate, propyl acetate, propyl propionate, and methyl acetate.

[0050] Furthermore, the second extractant contains water, C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 10-20:6-14:1.

[0051] Furthermore, the second extractant contains water, C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 10-15:8-12:1.

[0052] According to the present invention, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:5-20.

[0053] Furthermore, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:8-12.

[0054] According to the present invention, the second extraction is performed 3-10 times.

[0055] According to the present invention, the third extractant is selected from at least one of chloroform, chloromethane, dichloromethane and carbon tetrachloride.

[0056] According to the present invention, the mass ratio of caprolactone in the second extractant to the third extractant is 1:5-20.

[0057] Furthermore, the mass ratio of caprolactone in the second extract to the third extractant is 1:8-12.

[0058] In this invention, by selecting specific first, second, and third extractants, and by adjusting the amounts of these extractants, the purification process is simplified, and no side reactions occur during purification. The resulting caprolactone product not only has a high yield, but also exhibits significantly improved purity compared to existing processes.

[0059] According to the present invention, the second concentration is selected from at least one of evaporation concentration, rotary evaporation concentration and distillation concentration.

[0060] According to the present invention, the temperature of the second concentration is 35-70°C.

[0061] Furthermore, the temperature for the second concentration is 40-60°C.

[0062] In this invention, the conditions for determining the end of the second concentration are similar to those for the first concentration, and will not be repeated here. Preferably, the time for the second concentration is 20-120 minutes.

[0063] According to the present invention, the material to be purified containing caprolactone is subjected to solid-liquid separation, and the resulting solid-liquid separation liquid is subjected to the first extraction.

[0064] In this invention, the material to be purified containing caprolactone is not limited to the product directly discharged from the caprolactone synthesis device. For example, the purification method of this invention can also process the material to be purified containing caprolactone after simple purification treatment. Depending on the type and content of impurities in the material to be purified containing caprolactone, solid-liquid separation can be performed on the material to be purified containing caprolactone before mixing with the first extractant to remove some of the solid impurities.

[0065] Furthermore, the solid-liquid separation method is selected from vacuum filtration and / or needle filtration.

[0066] In this invention, based on the total weight of the initially purified material, the water content of the initially purified material is ≤2wt%. The material to be purified containing caprolactone may contain a certain amount of residual water. If the water content is too high, the initially purified material can be dehydrated before the first concentration, according to the requirements of the process conditions. If the water content in the material to be purified containing caprolactone is not high, the dehydration treatment can be omitted, and the residual water can be removed in subsequent processing, for example, by adjusting the concentration conditions during the first concentration process to separate the water and solvent together with the caprolactone. Further, the dehydration treatment includes a water-absorbing process using a desiccant and a desiccant separation process. Even further, the desiccant is selected from at least one of anhydrous magnesium sulfate, anhydrous calcium chloride, and color-changing silica gel. Further, the weight ratio of caprolactone to the desiccant in the initially purified material is 1:1-3.

[0067] A second aspect of the present invention provides a finished product of caprolactone obtained by the above purification method.

[0068] Furthermore, the purity of the finished caprolactone is greater than 85%.

[0069] Furthermore, the purity of the finished caprolactone is greater than 97%.

[0070] The finished caprolactone from Example 1 was detected by gas chromatography and analyzed by GC-MS. The results are as follows: Figure 3 and Figure 4 As shown. Figure 3 This is the gas chromatogram of the finished product, caprolactone. Figure 3 The chromatographic peak with a retention time of 8.675 min can be seen to be the caprolactone peak, indicating that the separation process has excellent separation effect. Figure 4 (b) is the mass spectrum of the separated product caprolactone. Figure 4 (c) and (d) are mass spectra of caprolactone from the spectral library. Figure 4 (e) is the mass spectrum of 3-methyl-1-pentene in the spectral library. The mass spectrum of the isolated caprolactone was compared with that of the spectral library. The similarity between the mass spectrum of the isolated product and that of caprolactone was 91%, while the similarity between the mass spectrum of the isolated product and that of 3-methyl-1-pentene was only 30%. This indicates that the separation and purification process used in this invention can obtain high-purity caprolactone.

[0071] Combination Figure 1 One specific embodiment of the present invention:

[0072] The material to be purified, containing caprolactone, is subjected to solid-liquid separation. The resulting solid-liquid separation is subjected to a first extraction to obtain a first extract. A reducing agent is added to the first extract to remove oxides. During the addition of the reducing agent, an indicator is used to detect the degree of oxide removal. Once the oxide content is reduced to a predetermined level, a primary purified material is obtained. A desiccant is added to the primary purified material. After the system becomes clear, the desiccant is removed by filtration to obtain a filtrate. The filtrate is first concentrated to obtain a concentrated material. The concentrated material is mixed with a second extractant and subjected to a second extraction to obtain a second extract. The second extract is mixed with a third extractant and subjected to a third extraction to obtain a third extract. The third extract is then second concentrated to obtain the final product, caprolactone.

[0073] In this invention, the first and second extraction processes can be performed multiple times as needed to fully utilize caprolactone. After absorbing water, the desiccant in this invention is calcined at a high temperature to remove the water, allowing it to be reused.

[0074] In the following embodiments, unless otherwise specified, all raw materials used are commercially available.

[0075] Composition of the material to be purified containing caprolactone: acetonitrile (21 wt%), hydrogen peroxide (54 wt%), water (15 wt%), caprolactone (10 wt%).

[0076] The following are the testing methods for performance parameters in embodiments of the present invention:

[0077] (1) Yield % = Mass of finished caprolactone / Mass of theoretical caprolactone × 100%.

[0078] (2) Purity % = Mass of caprolactone in finished caprolactone / Mass of finished caprolactone × 100%.

[0079] Example 1

[0080] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0081] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0082] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0083] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0084] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0085] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0086] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0087] (S6) Add the concentrated material into the separatory funnel;

[0088] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:10:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0089] (S6b) Repeat (S6a) twice to obtain the second extract;

[0090] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:10, and perform a third extraction to obtain the third extract.

[0091] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0092] Example 2

[0093] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0094] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0095] (S2a) Add the first extractant toluene to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0096] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0097] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0098] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:3. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate to obtain the filtrate.

[0099] (S5) Add the filtrate to the rotary evaporator and rotate it at 65°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0100] (S6) Add the concentrated material into the separatory funnel;

[0101] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 10:8:1, and the mass ratio of caprolactone to the second extractant in the concentrated material is 1:8; the separated aqueous layer is added to a separatory funnel.

[0102] (S6b) Repeat (S6a) twice to obtain the second extract;

[0103] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:8, and perform a third extraction to obtain the third extract.

[0104] (S8) Add the third extract material to the rotary evaporator and rotate it at 60°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0105] Example 3

[0106] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0107] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0108] (S2a) Add the first extractant chlorobenzene to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0109] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0110] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0111] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1. After the system is clarified, filter to remove the anhydrous magnesium sulfate after water absorption to obtain the filtrate.

[0112] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0113] (S6) Add the concentrated material into the separatory funnel;

[0114] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:12:1, and the mass ratio of caprolactone to the second extractant in the concentrated material is 1:12; the separated aqueous layer is added to a separatory funnel.

[0115] (S6b) Repeat (S6a) twice to obtain the second extract;

[0116] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:12, and perform a third extraction to obtain the third extract.

[0117] (S8) Add the third extract material to the rotary evaporator and rotate it at 40°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0118] Example 4

[0119] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0120] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0121] (S2a) Add the first extractant dichloromethane to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0122] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0123] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0124] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0125] (S5) Add the filtrate to the rotary evaporator and rotate it at 60°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0126] (S6) Add the concentrated material into the separatory funnel;

[0127] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:10:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0128] (S6b) Repeat (S6a) twice to obtain the second extract;

[0129] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:9, and perform a third extraction to obtain the third extract.

[0130] (S8) Add the third extract material to the rotary evaporator and rotate it at 60°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0131] Example 5

[0132] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0133] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0134] (S2a) Add the first extractant, dichloroethane, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0135] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0136] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0137] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate to obtain the filtrate.

[0138] (S5) Add the filtrate to the rotary evaporator and rotate it at 60°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0139] (S6) Add the concentrated material into a separating funnel;

[0140] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:8:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0141] (S6b) Repeat (S6a) twice to obtain the second extract;

[0142] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:12, and perform a third extraction to obtain the third extract.

[0143] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0144] Example 6

[0145] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0146] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0147] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:4. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0148] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0149] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0150] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:2. After the system is clarified, filter to remove the anhydrous magnesium sulfate after water absorption to obtain the filtrate.

[0151] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0152] (S6) Add the concentrated material into the separatory funnel;

[0153] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:10:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0154] (S6b) Repeat (S6a) twice to obtain the second extract;

[0155] (S7) The second extract material and chloromethane are added to a separatory funnel, wherein the mass ratio of caprolactone to chloromethane in the second extract material is 1:10, and a third extraction is performed to obtain the third extract material.

[0156] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0157] Example 7

[0158] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0159] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0160] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0161] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0162] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0163] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:2. After the system is clarified, filter to remove the anhydrous magnesium sulfate after water absorption to obtain the filtrate.

[0164] (S5) Add the filtrate to the rotary evaporator and rotate it at 60°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0165] (S6) Add the concentrated material into the separatory funnel;

[0166] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 20:14:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0167] (S6b) Repeat (S6a) twice to obtain the second extract;

[0168] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:6, and perform a third extraction to obtain the third extract.

[0169] (S8) Add the third extract material to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0170] Example 8

[0171] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0172] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0173] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0174] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0175] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0176] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0177] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0178] (S6) Add the concentrated material into the separatory funnel;

[0179] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents and C2-C8 ester solvents is 10:6:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0180] (S6b) Repeat (S6a) twice to obtain the second extract;

[0181] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:20, and perform a third extraction to obtain the third extract.

[0182] (S8) Add the third extract material to the rotary evaporator and rotate it at 60°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0183] Example 9

[0184] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0185] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0186] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:2. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0187] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0188] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0189] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0190] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0191] (S6) Add the concentrated material into the separatory funnel;

[0192] (S6a) Add 450 mL of the second extraction solvent to the separatory funnel, wherein the second extraction solvent contains water and C5-C 12The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:10:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0193] (S6b) Repeat (S6a) twice to obtain the second extract;

[0194] (S7) Add the second extract and 125 mL of chloroform into a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:10, and perform a third extraction to obtain the third extract.

[0195] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0196] Example 10

[0197] (S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0198] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0199] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0200] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0201] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0202] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0203] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0204] (S6) Add the concentrated material into the separatory funnel;

[0205] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 8:16:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0206] (S6b) Repeat (S6a) twice to obtain the second extract;

[0207] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:10, and perform a third extraction to obtain the third extract.

[0208] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0209] Example 11

[0210] S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0211] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0212] (S2a) Add the first extractant acetonitrile to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0213] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0214] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0215] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0216] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0217] (S6) Add the concentrated material into the separatory funnel;

[0218] (S6a) Add a second extractant to the separatory funnel, wherein the second extractant contains water and C5-C 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 15:10:1, the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10, and the separated aqueous layer is added to a separatory funnel.

[0219] (S6b) Repeat (S6a) twice to obtain the second extract;

[0220] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:10, and perform a third extraction to obtain the third extract.

[0221] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0222] Example 12

[0223] S1) The material to be purified containing caprolactone is filtered three times by vacuum filtration and twice by needle filtration to obtain a solid-liquid separation liquid.

[0224] (S2) Add the solid-liquid separated liquid to the separatory funnel.

[0225] (S2a) Add the first extractant, chloroform, to the separatory funnel, wherein the mass ratio of caprolactone in the material to be purified to the first extractant is 1:6. Allow the mixture to stand and separate into layers, then add the extracted oil phase to the separatory funnel.

[0226] (S2b) Repeat (S2a) 3 times to obtain the first extract;

[0227] (S3) Add the first extract to a beaker and place the beaker in a 0°C ice-water bath. Add saturated sodium bisulfite solution dropwise to the beaker, 10 drops at a time. Take a small amount of the solution from the beaker and add an indicator (10wt% potassium iodide and starch solution) to the taken-out solution. Observe the phenomenon. If the indicator turns black, it proves that hydrogen peroxide is still present in the system. Repeat this process until the indicator does not change color, then the hydrogen peroxide is completely removed, and the initially purified material is obtained.

[0228] (S4) Add anhydrous magnesium sulfate to the primary purified material. The weight ratio of caprolactone to anhydrous magnesium sulfate in the primary purified material is 1:1.5. After the system is clarified, filter to remove the water-absorbed anhydrous magnesium sulfate and obtain the filtrate.

[0229] (S5) Add the filtrate to the rotary evaporator and rotate it at 70°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the concentrated material.

[0230] (S6) Add the concentrated material into the separatory funnel;

[0231] (S6a) Add a second extractant to the separatory funnel, wherein the ratio of water to acetonitrile in the second extractant is 12:1, and the mass ratio of caprolactone to the second extractant in the concentrated material is 1:10. Add the separated water layer to the separatory funnel.

[0232] (S6b) Repeat (S6a) twice to obtain the second extract;

[0233] (S7) Add the second extract and chloroform to a separatory funnel, wherein the mass ratio of caprolactone to chloroform in the second extract is 1:10, and perform a third extraction to obtain the third extract.

[0234] (S8) Add the third extract material to the rotary evaporator and rotate it at 50°C. Stop the rotary evaporation when the liquid no longer collects at the mouth of the flask on the rotary evaporator to obtain the finished product caprolactone.

[0235] Comparative Example 1

[0236] The second extract from Example 1 was separated using a distillation column with 24 trays, the feed position being the 15th tray, a molar reflux ratio of 1.2, and an operating temperature of 80°C. The column pressure was 0.05 MPa, yielding caprolactone in 78% yield with a purity of 69%.

[0237] Table 1

[0238]

[0239]

[0240] Continued from Table 1

[0241]

[0242]

[0243] Note:

[0244] YLB1 is the mass ratio of caprolactone to the first extractant in the material to be purified.

[0245] YLB2 is the mass ratio of caprolactone to the second extractant in the concentrated material.

[0246] YLB3 represents the mass ratio of caprolactone to the third extractant in the second extractant.

[0247] As can be seen from the results of the embodiments of the present invention, by selecting specific first, second and third extractants and by adjusting their dosages, the yield of the finished caprolactone is not only high, but the purity of the finished caprolactone is also significantly improved compared with the existing process.

[0248] The embodiments of the present invention provide data to support the above-mentioned effects. For example, acetonitrile is a commonly used extractant. In Example 11, the first extractant was replaced with acetonitrile, and in Example 12, the second extractant was replaced with a mixture of water and acetonitrile. As can be seen from the effects in Table 1, the yield and purity of the finished caprolactone obtained in Examples 11 and 12 were reduced by more than 10% compared with the finished caprolactone obtained in Example 1. The above data proves that the selection of solvent based on the specific technical solution of the present invention will significantly affect the purity and yield of the finished caprolactone.

[0249] In this invention, although specific types of extractants were used in Examples 1, 7, 8, 9, and 10, the purity and yield of the final caprolactone obtained from these examples still showed significant differences by adjusting the amount of extractant used. This demonstrates that a better extraction effect can only be achieved through the synergistic effect of the various solvents. For example, in Example 9, the mass ratio of caprolactone to the first extractant in the material to be purified was 1:2, and in Example 10, the mass ratio of caprolactone to the second extractant in the concentrated material was 8:16:1. The purity and yield of the final caprolactone obtained from both were below 90%. Based on the above examples, by adopting the optimized technical solution of this invention, in Examples 7 and 8, by adjusting the amounts of the second and third extractants and synergizing them with the first extractant, the purity and yield of the final caprolactone were significantly improved compared to Examples 9 and 10. Examples 1 and 4-6 represent further optimized technical solutions in this invention. Through synergistic extraction with three extractants, the purity of the finished caprolactone is greater than 97%, and the yield is greater than 83%.

[0250] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for purifying caprolactone, characterized in that, The method includes the following steps: (1) The material to be purified containing caprolactone is mixed with the first extractant and subjected to the first extraction to obtain the first extract material; (2) Remove oxides from the first extracted material to obtain the first purified material; (3) The initially purified material is concentrated to obtain concentrated material; (4) The concentrated material is mixed with the second extractant and subjected to a second extraction to obtain the second extracted material; (5) The second extractant is mixed with the third extractant and subjected to a third extraction to obtain the third extractant; (6) The third extract material is concentrated in the second stage to obtain the finished product caprolactone; The first extractant is selected from at least one of chloroform, dichloromethane, and dichloroethane; the mass ratio of caprolactone in the material to be purified to the first extractant is 1:5-8. The second extractant is water and C5-C. 12 Hydrocarbon solvents and C2-C8 ester solvents; the C5-C 12 The hydrocarbon solvent is selected from at least one of n-hexane, n-pentane, n-heptane, and cyclohexane; the C2-C8 ester solvent is selected from at least one of ethyl acetate, propyl acetate, propyl propionate, and methyl acetate; the second extractant contains water, C5-C... 12 The mass ratio of hydrocarbon solvents to C2-C8 ester solvents is 10-15:8-12:1; the mass ratio of caprolactone to the second extractant in the concentrated material is 1:8-12; The third extractant is selected from at least one of chloroform, chloromethane, dichloromethane, and carbon tetrachloride; the mass ratio of caprolactone in the second extractant to the third extractant is 1:8-12.

2. The method according to claim 1, wherein, The first extraction is performed 2-5 times.

3. The method according to claim 1 or 2, wherein, The first concentration is selected from at least one of evaporation concentration, rotary evaporation concentration and distillation concentration.

4. The method according to claim 1 or 2, wherein, The temperature of the first concentration is 50-100℃.

5. The method according to claim 4, wherein, The temperature of the first concentration is 60-80℃.

6. The method according to claim 1 or 2, wherein, The second extraction is performed 3-10 times.

7. The method according to claim 1 or 2, wherein, The second concentration is selected from at least one of evaporation concentration, rotary evaporation concentration and distillation concentration.

8. The method according to claim 1 or 2, wherein, The second concentration temperature is 35-70℃.

9. The method according to claim 8, wherein, The second concentration temperature is 40-60℃.

10. The method according to claim 1 or 2, wherein, The method further includes the following steps: The material to be purified, containing caprolactone, is subjected to solid-liquid separation, and the resulting solid-liquid separation is subjected to the first extraction.

11. The method according to claim 10, wherein, The solid-liquid separation method is selected from vacuum filtration and / or needle filtration.

12. The method according to claim 1 or 2, wherein, Based on the total weight of the primary purified material, the moisture content of the primary purified material is ≤2wt%.

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