Method for preparing epsilon-caprolactone by peroxy acid oxidation method

Abstract

The invention discloses a method for preparing epsilon-caprolactone by a peroxy acid oxidation method, and relates to the field of organic chemical synthesis. The method specifically comprises the following steps: preparation of peroxy acid, Baeyer-Villiger oxidation reaction of peroxy acid and cyclohexanone, and separation and purification of a product. Peroxy acid generated by organic acid and hydrogen peroxide is used as an oxidizing agent, and a metering pump is adopted to accurately control the raw material proportion. The method has the advantages of simplicity and convenience in operation, mild reaction conditions and high yield, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the field of organic chemical synthesis, in particular to a method for preparing epsilon-caprolactone by a peroxyacid oxidation method. Background Art

[0002] ε-caprolactone is an important organic chemical raw material, widely used in the production of high-performance polyesters, polyurethane elastomers and degradable polymers. Its downstream products have excellent mechanical properties, biocompatibility and environmental friendliness, and are widely used in medical materials, coatings, adhesives and packaging materials. In addition, ε-caprolactone can also be used as a monomer for polymerization reactions to produce biodegradable plastics such as polycaprolactone (PCL). With the development of green chemical industry, the demand for efficient and environmentally friendly methods for preparing ε-caprolactone is increasing. At present, the methods for preparing ε-caprolactone mainly include the following: chemical catalysis, bioenzyme catalysis, and peracid oxidation.

[0003] Patent document A method for preparing ε-caprolactone by catalytic oxidation of cyclohexanone (patent publication number: CN102212055A) comprises the following steps: S1, adding raw acid anhydride according to a predetermined amount to a reaction container containing raw hydrogen peroxide aqueous solution and a catalyst, controlling the temperature of the reaction system at 5-20°C, and obtaining an organic peroxy acid; S2, adding the generated organic peroxy acid to cyclohexanone, mixing evenly, controlling the temperature of the reaction system at 30-100°C, and reacting for 1-15 hours. After the reaction is completed, cooling and separating to obtain the ε-caprolactone product.

[0004] Patent literature A continuous preparation method of ε-caprolactone (patent publication number: CN118221630A) combines a microchannel reactor with a traditional kettle reactor and controls the amount of hydrogen peroxide to effectively improve the raw material conversion rate.

[0005] However, the existing peracid oxidation method still needs to solve the following problems in industrial application: the activity of the peracid catalyst is low, and the yield and selectivity of ε-caprolactone are poor; in the traditional peracid oxidation method, the utilization rate of the peracid is not high and there are many by-products; the presence of by-products makes the subsequent separation process complicated, affecting the purity and yield of ε-caprolactone; since hydrogen peroxide and peracid have potential oxidative hazards, the control of the reaction conditions needs to be more precise. Summary of the invention

[0006] Based on the problems raised by the above background technology, the present invention proposes a method for preparing ε-caprolactone by peroxyacid oxidation. By optimizing the preparation and use of the oxidant and combining modern reaction equipment and process parameter control, an efficient, green and industrially adaptable solution is provided, which provides technical support for the large-scale production of ε-caprolactone.

[0007] The technical solution is as follows: A method for preparing ε-caprolactone by peroxyacid oxidation method, characterized in that it comprises the following steps: (1) Preparation of peroxyacid: Add 112-153 parts by weight of acetic anhydride and 34-51 parts by weight of hydrogen peroxide solution into reactor 1, then add an inorganic acid catalyst, and react at a set temperature for 100-130 seconds to obtain a peracetic acid solution; (2) Baeyer-Villiger oxidation reaction: In reactor 2, the prepared peracetic acid solution and cyclohexanone are mixed in a molar ratio of 1.05-1.3:1, and then a stabilizer is added, and an oxidation reaction is carried out at 40-60° C. for 60-120 seconds. After the reaction is completed, the reaction is quenched at low temperature to obtain crude ε-caprolactone; after separation and purification steps, high-purity ε-caprolactone is obtained.

[0008] As a preferred technical solution of the present invention, the amount of the inorganic acid catalyst added in step (1) is 0.1-2 wt % of the total mass of the reaction raw materials.

[0009] As a preferred technical solution of the present invention, the inorganic acid catalyst in step (1) is selected from at least one of sulfuric acid, phosphoric acid or methanesulfonic acid.

[0010] As a preferred technical solution of the present invention, the reaction temperature in step (1) is controlled to be 60-80°C.

[0011] As a preferred technical solution of the present invention, in step (1), the purity of cyclohexanone is 98%-99.5%, and the concentration of hydrogen peroxide is 30%-50%.

[0012] As a preferred technical solution of the present invention, the concentration of peracetic acid prepared in step (1) is between 20-45%.

[0013] As a preferred technical solution of the present invention, in step (2), the ratio of the stabilizer to the solution in the reactor 2 is 300-600 mg / L.

[0014] As a preferred technical solution of the present invention, the preparation method of the stabilizer in step (2) is: A. 20-40 parts by weight of 2,3-dimercaptosuccinic acid (CAS No.: 4710-17-2), 3-6 parts by weight of 1,2-vinyl diphosphonic acid (CAS No.: 6145-31-9), 200-300 parts by weight of ethylbenzene, 0.03-0.3 parts by weight of 3-vinylquinoline (CAS No.: 67752-31-2), and 0.01-0.01 parts by weight of a photoinitiator are mixed to obtain a mixture; B. stirring the mixture in step A at 70°C to 90°C for 30 to 60 minutes under nitrogen protection; C. Click chemistry reaction was carried out under ultraviolet light with a maximum absorption wavelength of 365 nm; D. After the reaction is completed, ethylbenzene is removed by distillation to obtain the desired stabilizer.

[0015] As a preferred technical solution of the present invention, the photoinitiator is one of 2-methyl-1-(4-methylmercapto)-2-morpholinyl-1-propanone, benzoin dimethyl ether, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0016] As a preferred technical solution of the present invention, the low-temperature quenching reaction temperature in step (2) is 0-10°C.

[0017] Stabilizer reaction mechanism: The two thiols of 2,3-dimercaptosuccinic acid react with diethyl 1,2-vinylphosphonate and 3-vinylquinoline to form thiol-olefin click chemistry reactions. Under ultraviolet light, these reactions generate stabilizers containing succinic acid, diphosphonic acid and quinoline functional groups.

[0018] Beneficial effects of stabilizers: The succinic acid functional group binds to the peroxyacid ion through hydrogen bonds and van der Waals forces, which enhances the stability of the solution. The diphosphonic acid functional group forms a stable complex with the metal ion through chelation, further inhibiting the decomposition of the peroxyacid. The introduction of the quinoline ring increases the steric hindrance effect of the molecule, reduces the frequency of collisions between molecules, and thus reduces the decomposition rate of the peroxyacid. This optimization of the spatial structure helps to improve the overall stability of the peroxide. The succinic acid, diphosphonic acid and quinoline functional groups work together to significantly improve the stability of the peroxyacid. Succinic acid enhances stability by forming hydrogen bonds, diphosphonic acid inhibits decomposition through chelation, and quinoline reduces the collision frequency by increasing steric hindrance, which comprehensively improves the stability of the solution.

[0019] Technical Effects The peroxyacid oxidation method provided by the present invention achieves efficient conversion of cyclohexanone by precisely controlling the reaction conditions. Experimental results show that under the optimal conditions, the cyclohexanone conversion rate reaches 96.2% and the ε-caprolactone yield reaches 80.9%, providing feasibility for industrial production. DETAILED DESCRIPTION

[0020] The features of the present invention are further illustrated by examples below, but the protection scope of this patent is not limited by the examples.

[0021] Example 1 (1) Preparation of peroxyacid: 130 g of acetic anhydride and 40 g of a 40% hydrogen peroxide solution were added to the reactor 1, followed by the addition of 1 wt% sulfuric acid as an inorganic acid catalyst based on the total mass of the reaction raw materials. The reaction temperature was set at 70° C. and the reaction time was 120 seconds to obtain a 30% peracetic acid solution.

[0022] (2) Baeyer-Villiger oxidation reaction: In reactor 2, the prepared peracetic acid solution is mixed with cyclohexanone with a purity of 99% at a molar ratio of 1.1:1, and then a stabilizer with a ratio of 300 mg / L is added. The stabilizer is prepared from 30g of 2,3-dimercaptosuccinic acid, 5g of 1,2-vinyl diphosphonic acid, 250g of ethylbenzene, 0.15g of 3-vinylquinoline and 0.005g of 2-methyl-1-(4-methylmercapto)-2-morpholinyl-1-propanone. The oxidation reaction is carried out at 50°C for 90 seconds, and after the reaction is completed, the low-temperature quenching reaction is carried out at 5°C to obtain crude ε-caprolactone. After subsequent separation and purification steps, high-purity ε-caprolactone is obtained.

[0023] Preparation method of the stabilizer in this example: 30g of 2,3-dimercaptosuccinic acid, 5g of 1,2-vinyl diphosphonic acid, 250g of ethylbenzene, 0.1g of 3-vinylquinoline and 0.01g of photoinitiator are mixed in a proportion. Under nitrogen protection, the mixture is heated to 80°C and stirred for 45 minutes. Subsequently, a click chemistry reaction is carried out under ultraviolet light with a maximum absorption wavelength of 365nm. After the reaction is completed, ethylbenzene is removed by distillation to obtain the desired stabilizer.

[0024] Example 2 (1) Preparation of peroxyacid: 120 g of acetic anhydride and 36 g of a 35% hydrogen peroxide solution were added to reactor 1, and 0.5 wt% of phosphoric acid was added as a catalyst based on the total mass of the reaction raw materials. The reaction temperature was set at 65° C. and the reaction time was 110 seconds to obtain a peracetic acid solution with a concentration of 25%.

[0025] (2) Baeyer-Villiger oxidation reaction: In reactor 2, the prepared peracetic acid solution and cyclohexanone with a purity of 98.5% are mixed at a molar ratio of 1.2:1, and a stabilizer with a ratio of 400 mg / L is added. The stabilizer is prepared from 25g of 2,3-dimercaptosuccinic acid, 4g of 1,2-vinyl diphosphonic acid, 275g of ethylbenzene, 0.2g of 3-vinylquinoline and 0.01g of benzoin dimethyl ether. The oxidation reaction is carried out at 45°C for 100 seconds, and after the reaction is completed, the low-temperature quenching reaction is carried out at 2°C to obtain a crude ε-caprolactone. After subsequent treatment, a high-purity product is obtained.

[0026] Preparation method of the stabilizer in this example: 25g of 2,3-dimercaptosuccinic acid, 4g of 1,2-vinyl diphosphonic acid, 220g of ethylbenzene, 0.05g of 3-vinylquinoline and 0.01g of photoinitiator are mixed. In a nitrogen atmosphere, the mixture is heated to 75°C and stirred for 30 minutes. Then, a click chemistry reaction is carried out under ultraviolet light (maximum absorption wavelength is 365nm). After the reaction is completed, ethylbenzene is removed by distillation to obtain the desired stabilizer.

[0027] Example 3 (1) Preparation of peroxyacid: 140 g of acetic anhydride and 45 g of a 50% hydrogen peroxide solution were added to the reactor 1, and 1.5 wt% of the total mass of the reaction raw materials was added as a catalyst. The reaction temperature was set at 75° C. and the reaction time was 130 seconds to obtain a 40% peracetic acid solution.

[0028] (2) Baeyer-Villiger oxidation reaction: In reactor 2, the prepared peracetic acid solution is mixed with cyclohexanone with a purity of 99.2% at a molar ratio of 1.3:1, and a stabilizer with a ratio of 500 mg / L is added. The stabilizer is prepared from 35 g of 2,3-dimercaptosuccinic acid, 6 g of 1,2-vinyl diphosphonic acid, 300 g of ethylbenzene, 0.25 g of 3-vinylquinoline and 0.008 g of 2,4,6-trimethylbenzoyl diphenylphosphine oxide. The oxidation reaction is carried out at 60°C for 60 seconds, and after the reaction is completed, the low-temperature quenching reaction is carried out at 0°C to obtain crude ε-caprolactone. After further treatment, high-purity ε-caprolactone is obtained.

[0029] Preparation method of the stabilizer in this example: 35g of 2,3-dimercaptosuccinic acid, 6g of 1,2-vinyl diphosphonic acid, 280g of ethylbenzene, 0.2g of 3-vinylquinoline and 0.01g of photoinitiator are mixed. Under nitrogen protection, the mixture is heated to 90°C and stirred for 60 minutes. Then, a click chemistry reaction is carried out under ultraviolet light (maximum absorption wavelength is 365nm). After the reaction is completed, ethylbenzene is removed by distillation to obtain the desired stabilizer.

[0030] Example 4 (1) Preparation of peroxyacid: 112 g of acetic anhydride and 51 g of a 30% hydrogen peroxide solution were added to reactor 1, and a mixture of sulfuric acid and phosphoric acid (1:1) was added as a catalyst at 0.2 wt% of the total mass of the reaction raw materials. The reaction temperature was set at 80°C and the reaction time was 100 seconds to obtain a peracetic acid solution with a concentration of 20%.

[0031] (2) Baeyer-Villiger oxidation reaction: In reactor 2, the prepared peracetic acid solution is mixed with cyclohexanone with a purity of 98.8% at a molar ratio of 1.05:1, and a stabilizer with a ratio of 600 mg / L is added. The stabilizer is prepared from 40g of 2,3-dimercaptosuccinic acid, 3g of 1,2-vinyl diphosphonic acid, 225g of ethylbenzene, 0.3g of 3-vinylquinoline and 0.01g of 2-methyl-1-(4-methylmercapto)-2-morpholinyl-1-propanone. The oxidation reaction is carried out at 40°C for 120 seconds, and after the reaction is completed, the low-temperature quenching reaction is carried out at 8°C to obtain a crude ε-caprolactone. After separation and purification steps, a high-purity product is obtained.

[0032] Preparation method of the stabilizer in this example: 20g of 2,3-dimercaptosuccinic acid, 3g of 1,2-vinyl diphosphonic acid, 300g of ethylbenzene, 0.03g of 3-vinylquinoline and 0.01g of photoinitiator are mixed in a ratio. In a nitrogen atmosphere, the mixture is heated to 70°C and stirred for 50 minutes. Then, a click chemistry reaction is carried out under ultraviolet light (maximum absorption wavelength is 365nm). After the reaction is completed, ethylbenzene is removed by distillation to obtain the desired stabilizer product.

[0033] Comparative Example 1 The only difference between this example and Example 1 is that no stabilizer is added.

[0034] Comparative Example 2 The only difference between this example and Example 1 is that 1,2-vinyl diphosphonic acid is not added during the preparation of the stabilizer.

[0035] Comparative Example 3 This example differs from Example 1 only in that 3-vinylquinoline is not added during the preparation of the stabilizer.

[0036] The above embodiment test method: 1) Cyclohexanone conversion rate: After the reaction is completed, the reaction mixture is analyzed by gas chromatography (GC); a certain volume of sample is taken, diluted and injected into GC or HPLC for analysis; the conversion rate of cyclohexanone is calculated based on the comparison of the retention time of cyclohexanone and ε-caprolactone with the internal standard.

[0037] 2) ε-caprolactone yield: After the reaction is completed, the volatile solvent and unreacted raw materials in the reaction system are removed by reduced pressure distillation; the product is purified by column chromatography to collect pure ε-caprolactone; the purified ε-caprolactone is weighed by a precision balance and its mass is calculated; according to the consumption of cyclohexanone in the reaction, the mass of the ε-caprolactone that can be obtained theoretically is calculated, and compared with the mass of the ε-caprolactone actually obtained to obtain the yield.

[0038] Table 1 Test results Cyclohexanone conversion rate% ε-caprolactone yield% Example 1 95.8 80.9 Example 2 96.2 82.0 Example 3 96.4 82.4 Example 4 96.7 83.1 Comparative Example 1 87.5 72.2 Comparative Example 2 92.2 76.5 Comparative Example 3 94.0 77.4 By optimizing the reaction conditions, the method of the present invention achieves efficient conversion of cyclohexanone at a relatively low reaction temperature and in a short time, significantly improves the selectivity and yield of ε-caprolactone, and has obvious advantages over the existing methods.

[0039] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing ε-caprolactone by peroxyacid oxidation, characterized in that: The following steps are involved: (1) Preparation of peroxyacid: Add 112-153 parts by weight of acetic anhydride and 34-51 parts by weight of hydrogen peroxide solution into reactor 1, then add an inorganic acid catalyst, and react at a set temperature for 100-130 seconds to obtain a peracetic acid solution; (2) Baeyer-Villiger oxidation reaction: In reactor 2, the prepared peracetic acid solution and cyclohexanone are mixed in a molar ratio of 1.05-1.3:1, and then a stabilizer is added, and an oxidation reaction is carried out at 40-60° C. for 60-120 seconds. After the reaction is completed, the reaction is quenched at low temperature to obtain crude ε-caprolactone; after separation and purification steps, high-purity ε-caprolactone is obtained.

2. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: The amount of the inorganic acid catalyst added in step (1) is 0.1-2 wt % of the total mass of the reaction raw materials.

3. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: In step (1), the inorganic acid catalyst is selected from at least one of sulfuric acid, phosphoric acid or methanesulfonic acid.

4. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: In the step (1), the reaction temperature is controlled at 60-80°C.

5. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: In step (1), the purity of cyclohexanone is 98%-99.5%, and the concentration of hydrogen peroxide is 30%-50%.

6. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: The concentration of the peracetic acid prepared in step (1) is between 20-45%.

7. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: In step (2), the ratio of the stabilizer to the solution in reactor 2 is 300-600 mg / L.

8. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: The preparation method of the stabilizer in step (2) is: A. mixing 20-40 parts by weight of 2,3-dimercaptosuccinic acid, 3-6 parts by weight of 1,2-vinyl diphosphonic acid, 200-300 parts by weight of ethylbenzene, 0.03-0.3 parts by weight of 3-vinylquinoline, and 0.01-0.01 parts by weight of a photoinitiator to obtain a mixture; B. stirring the mixture in step A at 70°C to 90°C for 30 to 60 minutes under nitrogen protection; C. Click chemistry reaction was carried out under ultraviolet light with a maximum absorption wavelength of 365 nm; D. After the reaction is completed, ethylbenzene is removed by distillation to obtain the desired stabilizer.

9. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 8, characterized in that: The photoinitiator is one of 2-methyl-1-(4-methylmercapto)-2-morpholinyl-1-propanone, benzoin dimethyl ether and 2,4,6-trimethylbenzoyl diphenyl phosphine oxide.

10. The method for preparing ε-caprolactone by peroxyacid oxidation according to claim 1, characterized in that: The low temperature quenching reaction temperature in step (2) is 0-10°C.