Preparation method of sodium pyrrolidone carboxylate

Abstract

The invention provides a preparation method of sodium pyrrolidone carboxylate, and belongs to the technical field of chemical synthesis. The preparation method of the sodium pyrrolidone carboxylate comprises the following steps: 1) mixing sodium glutamate, ultrapure water and a catalyst, and adjusting the pH value to weak acidity to obtain a mixed solution; and 2) transferring the mixed solution into a micro-channel reactor, and reacting to obtain the sodium pyrrolidone carboxylate. The sodium pyrrolidone carboxylate prepared by the method provided by the invention is high in yield and purity, and the preparation method is simple and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and in particular relates to a method for preparing sodium pyrrolidonecarboxylate. Background Art

[0002] In recent years, the market size of sodium pyrrolidonecarboxylic acid (PCA) has continued to expand, thanks to the improvement of the prosperity of downstream industries, especially the growth of demand for sodium PCA in the cosmetics industry. As an amino acid derivative, sodium PCA has the characteristics of good chemical stability and good moisturizing properties. It is widely used in the cosmetics field and is one of the important moisturizing ingredients in cosmetics. With the improvement of consumers' requirements for cosmetics quality and the continuous development of the cosmetics industry, the market demand for sodium PCA will further increase.

[0003] Although the Chinese market started late, a number of small and medium-sized enterprises have emerged, such as Chengdu Zhenwotong Technology Co., Ltd., Hubei Mackays Refining Technology Co., Ltd., Sichuan Jisheng Biopharmaceutical Co., Ltd., etc. While continuously improving product quality and technical level, these companies are also actively seeking market expansion and cooperation opportunities.

[0004] The solubility of glutamic acid in water is relatively low (100°C, 14g / 100g). If glutamic acid is used as a raw material for wet pyrolysis, not only will the concentration of the reactants be limited, but it will also be difficult to concentrate and crystallize the product. At the same time, the low pH (about 2.5) will also cause equipment corrosion problems.

[0005] Dry pyrolysis using sodium glutamate as raw material is not only simple in process, but also can obtain solid products. However, since sodium L-glutamate and sodium L-pyrrolidonecarboxylate are prone to racemization and lose their physiological activity when heated, the appropriate pyrolysis temperature is very critical. At present, the synthesis of sodium PCA is completed in a reactor, which not only takes a long time to react, but also produces a large number of side reactions due to insufficient reaction or different local concentrations, which hinders the efficient production of sodium PCA products. Therefore, how to improve the yield and purity of sodium PCA products has become a problem that needs to be solved urgently. Summary of the invention

[0006] The invention provides a method for preparing sodium pyrrolidonecarboxylate. The method provided by the invention has high yield and good purity in preparing sodium pyrrolidonecarboxylate, and the preparation method is simple and efficient.

[0007] In order to achieve the above object, the present invention provides a method for preparing sodium pyrrolidonecarboxylate, comprising the following steps:

[0008] 1) mixing sodium glutamate, ultrapure water and a catalyst, adjusting the pH to 3-4, and obtaining a mixed solution;

[0009] 2) transferring the mixed solution into a microchannel reactor for reaction to obtain sodium pyrrolidonecarboxylate.

[0010] Preferably, after obtaining the mixed solution in step 1), the method further comprises subjecting the obtained mixed solution to ultrasonic treatment.

[0011] Preferably, the ultrasonic treatment lasts for 10 to 20 minutes and has a frequency of 60 to 80 kHz.

[0012] Preferably, the mass ratio of sodium glutamate to ultrapure water in step 1) is 1 kg: 0.8-1.5 kg.

[0013] Preferably, the catalyst in step 1) is a ruthenium-based catalyst, and the mass ratio of sodium glutamate to the catalyst is 1 kg: 0.1 to 1 g.

[0014] Preferably, phosphoric acid is used to adjust the pH in step 1).

[0015] Preferably, during the reaction in step 2), the pressure in the microchannel reactor is 2-5 MPa, the temperature in the microchannel reactor is 150-200° C., and the reaction time is 30-60 min.

[0016] Preferably, the feed rate of the mixed solution when it is transferred into the microchannel reactor in step 2) is 70-100 mL / min.

[0017] Preferably, after the reaction in step 2) is completed, the reaction solution is purified, and the purification method includes: performing activated carbon decolorization treatment on the reaction solution while it is hot, centrifugation, and suction filtration.

[0018] Preferably, the mesh size of the activated carbon is 100 to 500 meshes; the centrifugal speed is 600 to 1200 r / min, and the centrifugal time is 5 to 20 min.

[0019] Compared with the prior art, the advantages and positive effects of the present invention are:

[0020] The method for preparing sodium pyrrolidone carboxylate provided by the present invention is to carry out cyclization reaction of sodium glutamate in the form of aqueous solution in a microchannel reactor. On the one hand, the reaction is carried out in a microchannel reactor, which can not only reduce the reaction temperature, but also prevent sodium glutamate and pyrrolidone from losing physiological activity due to high temperature heating and racemization, and the product has low synthesis temperature, and the side reaction is relatively reduced, thereby improving the product quality; while shortening the reaction time, the conversion rate of the product can be greatly improved by using a microchannel reactor, and then the yield is improved. At the same time, the full progress of the reaction and the smaller reaction space can well suppress the generation of side reactions and improve the purity of the product. On the other hand, the method provided by the present invention not only does not need to dehydrate sodium glutamate before the cyclization reaction, but also saves time and energy, and also adds a large amount of water to prepare an aqueous solution for reaction. Through the protection of the aqueous solution, the control of cyclization and optical rotation will be more controllable.

[0021] At the same time, the raw materials of this reaction system are simple, and the subsequent cleaning will be easier and more labor-saving, and only requires rinsing with clean water.

[0022] Furthermore, the present invention adds a catalyst during the preparation process to further accelerate the reaction rate, save time and energy, and is more conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the infrared test spectrum of the product prepared in Example 1;

[0024] Figure 2 This is the infrared spectrum of standard PCA sodium. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a method for preparing sodium pyrrolidonecarboxylate, comprising the following steps:

[0027] 1) mixing sodium glutamate, ultrapure water and a catalyst, adjusting the pH to 3-4, and obtaining a mixed solution;

[0028] 2) transferring the mixed solution into a microchannel reactor for reaction to obtain sodium pyrrolidonecarboxylate.

[0029] The present invention mixes sodium glutamate, ultrapure water and a catalyst, and adjusts the pH to 3-4 to obtain a mixed solution. In the present invention, the mass ratio of the sodium glutamate to the ultrapure water is preferably 1Kg:0.8-1.5Kg. In the present invention, the mass ratio of the sodium glutamate to the catalyst is preferably 1Kg:0.1-1g. In the present invention, the catalyst is preferably a ruthenium catalyst, more preferably ruthenium trichloride. In the present invention, phosphoric acid is preferably used to adjust the pH. In the present invention, adjusting the pH to weak acidity can promote the cyclization of sodium glutamate, because sodium glutamate is an acidic amino acid, and alkalinity will destroy its structure, thereby promoting the progress of the entire reaction.

[0030] After obtaining the mixed solution, the present invention transfers the mixed solution into a microchannel reactor to react and obtain sodium pyrrolidone carboxylate. In the present invention, after obtaining the mixed solution, in order to fully dissolve sodium glutamate, it is preferably further included to ultrasonically treat the obtained mixed solution. In the present invention, the time of the ultrasonic treatment is preferably 10 to 20 minutes, and the frequency is preferably 60 to 80 kHZ. In the present invention, when reacting, the pressure in the microchannel reactor is preferably 2 to 5 MPa, the temperature in the microchannel reactor is preferably 150 to 200 ° C, and the reaction time is preferably 30 to 60 minutes. The feed rate when the mixed solution is transferred to the microchannel reactor is preferably 70 to 100 mL / min. In the present invention, the manufacturing material of the microchannel reactor is preferably selected from materials with high corrosion resistance and high strength, such as silicon carbide. These materials can withstand high temperature, high pressure and erosion by corrosive substances, and can ensure the long-term stable operation of the reactor.

[0031] In the prior art, when sodium glutamate is used as raw material to prepare sodium pyrrolidone carboxylate, the general operation is: sodium glutamate is first dehydrated to remove the crystal water in sodium glutamate, and then a cyclization reaction is performed to prepare sodium pyrrolidone carboxylate. Sodium glutamate is first dehydrated because the boiling point of water at normal pressure is 100 ° C, and when the cyclization reaction is carried out in an autoclave reactor, the reaction temperature generally needs to be above 200 ° C to activate the reaction activity. If sodium glutamate contains crystal water, during the cyclization process, the residual water will affect the temperature of the entire system and cause the cyclization reaction to be uncontrollable. Therefore, the traditional reaction needs to be dehydrated at low temperature in advance to avoid uncontrollable cyclization, and then the sodium glutamate with crystal water removed is used to carry out subsequent cyclization. However, dehydration treatment is not only time-consuming and laborious, but also consumes a lot of energy, and is prepared in a traditional autoclave reactor without atmosphere protection, and is extremely easy to oxidize, and in the case of high temperature, by-products are serious, and optical activity is difficult to control, while increasing the amount of activated carbon used in post-treatment decolorization, and increasing costs. The light transmittance of the product will be correspondingly lower, and there will be many disadvantages such as the kettle residue is difficult to handle, resulting in a certain degree of high cleaning costs.

[0032] The method provided by the present invention adopts a microchannel reactor for reaction. The microchannel reactor has a micron-level flow channel. This design makes the mass transfer and heat transfer very fast, thereby effectively avoiding the "flying temperature" phenomenon, that is, the reaction is controlled to be stably carried out within the explosion limit. While shortening the reaction time, the conversion rate of the product can be greatly improved, and then the yield can be improved. At the same time, the full progress of the reaction and the smaller reaction space can well suppress the generation of side reactions and improve the purity of the product. In addition, the reaction activity of the microchannel reactor itself is 10 to 20 times that of the traditional kettle reactor, and the cyclization of sodium glutamate can be promoted without high temperature, which provides a strong guarantee for the protection of the aqueous solution to make the whole reaction more uniform. Therefore, in the early stage, it is not only unnecessary to remove the crystal water in sodium glutamate, but also sodium glutamate can be dissolved in water to prepare an aqueous solution for reaction. At the same time, through the protection of the aqueous solution, the control of cyclization and optical rotation will be more controllable, and the product will have a low synthesis temperature, and the side reactions will be relatively reduced, while improving the product quality, it will also save more energy. At the same time, the raw materials of this reaction system are simple, and the subsequent cleaning will be more trouble-free and labor-saving, and it can be rinsed with clean water. The kettle residue and other water-insoluble substances produced by the traditional reactor need to be washed with alkali, so the present invention has more advantages.

[0033] The reaction for preparing sodium pyrrolidonecarboxylate provided by the present invention is specifically shown in Formula I:

[0034]

[0035] In the present invention, after the mixed solution is transferred into the microchannel reactor and the reaction is completed, it is preferred to further purify the reaction solution. In the present invention, the purification method preferably includes: decolorizing the reaction solution with activated carbon while it is hot, centrifuging, and filtering. In the present invention, the mesh size of the activated carbon is preferably 100 to 500 meshes; the rotation speed of the centrifuge is preferably 600 to 1200 r / min, and the centrifugation time is preferably 5 to 20 min.

[0036] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0037] Example 1

[0038] Mix 1 kg of sodium glutamate with 1 kg of ultrapure water, then add 0.5 g of ruthenium trichloride to mix, add 4 g of phosphoric acid to adjust the pH to weak acidity, and then ultrasonicate at a frequency of 80 KHZ for 15 minutes to obtain a mixed solution. After the ultrasonication is completed, use high-purity nitrogen to purge the inside of the microchannel reactor, then start heating, control the temperature in the reactor at 160 ° C, start the boosting program, and maintain the internal pressure at 3 MPa. After the temperature reaches the specified temperature, add the mixed solution to the microchannel reactor at a speed of 80 mL / min using a plunger pump, and carry out high-temperature and high-pressure reaction for 30 minutes. After the reaction is completed, use 200 mesh activated carbon for decolorization while hot, and then centrifuge the mixture at a speed of 1000 r / min for 10 minutes. After the centrifugation is completed, cool to room temperature, and filter to remove the residue to obtain the finished product of sodium PCA. Take samples for various performance tests. After qualitative testing, the product is a sodium PCA product. The specific infrared test spectrum of the product is as follows Figure 1 The purity of the final sample was 99.8%, the yield was 98%, the optical rotation was -9.8°, and the transmittance was 97%.

[0039] Example 2

[0040] 0.8 kg sodium glutamate was mixed with 1 kg ultrapure water, and then 0.5 g ruthenium trichloride was added for mixing, and 3 g phosphoric acid was added for pH adjustment to weak acidity, and then ultrasonicated at a frequency of 60 kHz for 10 min to obtain a mixed solution. After the ultrasonication, high-purity nitrogen was used to purge the inside of the microchannel reactor, and then the temperature was turned on, the temperature in the reactor was controlled at 180 ° C, and the boosting program was started to maintain the internal pressure at 5 MPa. After the temperature reached the specified temperature, the mixed solution was added to the microchannel reactor at a speed of 100 mL / min by a plunger pump, and the high-temperature and high-pressure reaction was carried out for 1 hour. After the reaction was completed, it was decolorized with 400 mesh activated carbon while hot, and then the mixture was centrifuged at a speed of 600 r / min for 20 min. After the centrifugation was completed and cooled to room temperature, the residue was removed by suction filtration to obtain a PCA sodium finished product, and samples were taken for various performance tests. After qualitative testing, the product was a PCA sodium product. The purity of the final sample was 99.5%, the yield was 96%, the optical rotation was -9.4°, and the transmittance was 95%.

[0041] Example 3

[0042] First, 1.5Kg sodium glutamate is mixed with 1Kg ultrapure water, then 1g ruthenium trichloride is added for mixing, 5g phosphoric acid is added for pH adjustment to weak acidity, then ultrasonic 20min at a frequency of 60kHZ to obtain a mixed solution. After the completion of the ultrasound, high-purity nitrogen is used to purge the inside of the microchannel reactor, and then the temperature is turned on and heated up, and the temperature in the reactor is controlled at 200°C, and the boost program is started to keep the internal pressure at 2Mpa. After the temperature reaches the specified temperature, the mixed solution is added to the microchannel reactor at a speed of 70mL / min using a plunger pump, and high temperature and high pressure reaction is carried out for 40min. After the reaction is completed, 500 mesh activated carbon is used for decolorization while hot, and then the mixture is centrifuged at a speed of 1200r / min for 10min. After the centrifugation is completed and cooled to room temperature, the residue is removed by suction filtration to obtain a PCA sodium finished product, and a sample is taken for the detection of various performances. After qualitative testing, the product is a PCA sodium product. The purity of the final sample is 99%, the yield is 92%, the optical rotation is -10°, and the transmittance is 93%.

[0043] Comparative Example 1

[0044] 200g of sodium glutamate is added to a three-necked flask, connected to a condenser, and heated in an oil bath. After the material temperature rises to 140°C, the temperature is kept rising by 8°C per hour. After the material temperature reaches 220°C, no water is distilled out. After the material temperature is cooled to 100°C, 200g of pure water is added, heated and stirred to dissolve, and an external circulation pump is used to assist dissolution if necessary. The material liquid is cooled to 60°C and flows through an activated carbon column, the decolorizing liquid is collected, the pH value is adjusted to neutral with phosphoric acid, 35g is dehydrated under reduced pressure, and adjusted to an aqueous solution containing 50% of sodium L-pyrrolidonecarboxylate. Finally, 320g of product can be obtained. After qualitative analysis, the product is sodium PCA. The purity of the comparative example of the final sample is 95%, the yield is 99.3%, the optical rotation is -10.2, and the transmittance is 90%.

[0045] Comparative Example 2

[0046] 1Kg of sodium glutamate was mixed with 1Kg of ultrapure water, and then 0.5g of ruthenium trichloride was added for mixing, and 4g of phosphoric acid was added for pH adjustment to weak acidity, followed by ultrasonication at a frequency of 70Khz for 15min to obtain a mixed solution. After the ultrasonication, a high pressure reactor was used, 160°C, 3Mpa for 90min of reaction, and after the reaction was completed, 200 mesh activated carbon was used for decolorization while hot, and then the mixture was centrifuged at a speed of 1000r / min for 10min, and after the centrifugation was completed and cooled to room temperature, the residue was removed by suction filtration to obtain a finished product of sodium PCA, and samples were taken for testing of various properties. After qualitative testing, the product was a sodium PCA product. The purity of the final sample was 92%, the yield was 90%, the optical rotation was -9.8°, and the transmittance was 92%.

[0047] Comparative Example 3

[0048] 1Kg sodium glutamate is mixed with 1Kg ultrapure water, and then 4g phosphoric acid is added to adjust pH to weak acidity, and then ultrasonic 15min at a frequency of 80Khz is used to obtain a mixed solution. After the ultrasonic is completed, high-purity nitrogen is used to purge the inside of the microchannel reactor, and then the temperature is turned on and the temperature in the reactor is controlled at 160°C. The boost program is started, and the internal pressure is kept at 3Mpa. After the temperature reaches the specified temperature, the mixed solution is added to the microchannel reactor at a speed of 80mL / min using a plunger pump, and high temperature and high pressure reaction is carried out for 90min. After the reaction is completed, 200 mesh activated carbon is used for decolorization while hot, and then the mixture is centrifuged at a speed of 1000r / min for 10min. After centrifugation is completed and cooled to room temperature, the residue is removed by suction filtration, and the PCA sodium finished product is obtained. Samples are taken for the detection of various performances. After qualitative testing, the product is a PCA sodium product. The purity of the final sample is 99.1%, the yield is 92%, the optical rotation is -9.6°, and the transmittance is 93%.

[0049] Wherein: The index testing method of the products in each embodiment and comparative example is as follows:

[0050] Qualitative identification: The substance was characterized by infrared spectroscopy and compared with the standard PCA sodium standard product, and it was identified as PCA sodium product. The standard sample spectrum is as follows Figure 2 As shown:

[0051] Specific rotation:

[0052] Accurately weigh a sample and place 13 g (accurate to 0.0001 g) in a 100 mL volumetric flask. Add distilled water to make up the volume and bring the temperature to (20 ± 0.5°C). Inspect according to the method specified in GB / T613.

[0053] Transmittance:

[0054] Turn on the spectrophotometer, adjust the wavelength to 430nm, pour the PCA-sodium sample into a 1cm cuvette, use distilled water as the reference solution, put it into the instrument, and directly read the transmittance of PCA-sodium. Take the arithmetic mean of the two parallel determination results as the determination result, and the difference between the two parallel determination results shall not exceed 0.5%.

[0055] purity:

[0056] With reference to GB / T 35799-2018 "High Performance Liquid Chromatography for the Determination of Sodium Pyrrolidonecarboxylate in Cosmetics", the purity of the product was calibrated by liquid chromatography using standard sample comparison and area normalization method.

[0057] Yield:

[0058] Since PCA-NA contains only one nitrogen atom, weigh 0.5 g (accurate to 0.0001 g) of sample and measure it according to GB11891 or using an automatic nitrogen analyzer to obtain the nitrogen content.

[0059] Result calculation

[0060]

[0061] Where:

[0062] N is nitrogen content, %;

[0063] 14.01 is the relative atomic weight of nitrogen;

[0064] 151.10 is the molecular weight of PCA sodium;

[0065] The arithmetic mean of the results of two parallel determinations was taken as the determination result. The difference between the two parallel determination results was no more than 0.5%. The mass was then converted according to the content of the sodium PCA aqueous solution to obtain the molar number, and the final yield was converted according to the generated molar ratio.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing sodium pyrrolidonecarboxylate, characterized in that: The steps include: 1) mixing sodium glutamate, ultrapure water and a catalyst, adjusting the pH to 3-4, and obtaining a mixed solution; 2) transferring the mixed solution into a microchannel reactor for reaction to obtain sodium pyrrolidonecarboxylate.

2. The preparation method according to claim 1, characterized in that: After the mixed solution is obtained in step 1), the mixed solution is further subjected to ultrasonic treatment.

3. The preparation method according to claim 2, characterized in that: The ultrasonic treatment time is 10 to 20 minutes, and the frequency is 60 to 80 kHz.

4. The preparation method according to claim 1, characterized in that: The mass ratio of sodium glutamate to ultrapure water in step 1) is 1 kg: 0.8-1.5 kg.

5. The preparation method according to claim 1, characterized in that: In step 1), the catalyst is a ruthenium-based catalyst, and the mass ratio of sodium glutamate to the catalyst is 1 kg: 0.1 to 1 g.

6. The preparation method according to claim 1, characterized in that: In step 1), phosphoric acid is used to adjust the pH.

7. The preparation method according to claim 1, characterized in that: During the reaction in step 2), the pressure in the microchannel reactor is 2-5 MPa, the temperature in the microchannel reactor is 150-200° C., and the reaction time is 30-60 min.

8. The preparation method according to claim 1, characterized in that: The feed rate of the mixed solution when it is transferred into the microchannel reactor in step 2) is 70-100 mL / min.

9. The preparation method according to claim 1, characterized in that: After the reaction in step 2) is completed, the reaction solution is purified, and the purification method includes: performing activated carbon decolorization treatment on the reaction solution while it is hot, centrifugation, and suction filtration.

10. The preparation method according to claim 9, characterized in that: The mesh number of the activated carbon is 100 to 500 meshes; the rotation speed of the centrifuge is 600 to 1200 r / min, and the centrifugation time is 5 to 20 min.

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