A kind of synthetic method of DL-lysine

Abstract

The invention discloses a synthetic method of DL-Lysine, including: S10, DL-Lysine crude product preparation steps: L-Lysine hydrochloride is dissolved in a mixed solution of water and glacial acetic acid, heated and stirred for racemization, DL-Lysine crude product is obtained after racemization, DL-Lysine crude product is decolorized with activated carbon, and DL-Lysine crude product aqueous solution is obtained; S20, DL-Lysine finished product preparation steps: DL-Lysine crude product aqueous solution is desalted by electrodialysis equipment, cooled and crystallized, filtered and dried, and DL-Lysine finished product is obtained. The synthetic method of the present invention has the advantages of mild conditions, fast reaction speed, simple operation, high product purity, high yield, mother liquor can be recovered, required reagents are environmentally friendly, low price, etc., and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and in particular to a method for synthesizing DL-lysine. Background Art

[0002] DL-Lysine is called DL-Lysine in English, CAS No.: 70-54-2, and its structural formula is as follows:

[0003]

[0004] Lysine is a key substance that helps other nutrients to be fully absorbed and utilized by the human body. Only when the human body is supplemented with enough L-lysine can it improve the absorption and utilization of food protein, achieve balanced nutrition, and promote growth and development. The main raw material involved in the production process of Lysine Aspirin, a widely used antipyretic and analgesic drug on the market, is DL-lysine.

[0005] In the patent publication CN1680282A, the process is to dissolve an optically active amino acid or its salt in an alkaline or acidic solution, add aldehydes or ketones or metal ion catalysts under microwave radiation at 10°C to the reaction reflux temperature, and perform a racemization reaction. The disadvantage of this process is that the amount of racemized sample in the microwave device is too small, and the introduction of the metal catalyst leads to impure samples, which increases the harm to the human body and is not suitable for large-scale production.

[0006] In the patent publication CN1569815A, the process is to dissolve L-amino acid in an organic acid solvent, add organic acid anhydride, heat for acylation, generate racemic amidocarboxylic acid, and then deacylate to generate DL-amino acid. The disadvantages of this process are that more organic reagents are used, the reaction temperature is high, the steps are complicated, and it is not suitable for industrial production.

[0007] In the patent publication CN106674036B, the process is to fully react acetylsalicylic acid with an aqueous sodium bicarbonate solution to obtain sodium acetylsalicylic acid, then mix the aqueous sodium acetylsalicylic acid solution with an aqueous DL-lysine solution for reaction, evaporate the reaction solution in a 50-55°C water bath to remove water, place it at 0-5°C for 18-24h, crystallize and filter to obtain DL-lysine. The defect of this process is that acetylsalicylic acid and sodium bicarbonate will release heat and generate CO2, and acetylsalicylic acid is prone to hydrolysis in a high-temperature acidic system to generate salicylic acid that is more harmful to the human body. The temperature is too high when evaporating and removing water in a water bath, DL-lysine is easily decomposed, and the operation is cumbersome, which is not conducive to industrial production.

[0008] In the patent publication CN102993036A, the process is a method for preparing a sterile raw material of DL-lysine, which uses a large amount of anhydrous ethanol and removes bacteria and heat sources through microfiltration. The process is cumbersome, resulting in waste of resources, manpower and material resources, and is not conducive to large-scale production.

[0009] Therefore, it is particularly necessary to study a new synthesis method of DL-lysine. Summary of the invention

[0010] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for synthesizing DL-lysine, which has the advantages of mild conditions, fast reaction speed, simple operation, high product purity, high yield, mother liquor can be recovered, required reagents are environmentally friendly, low price, etc., and is suitable for large-scale production.

[0011] The purpose of the present invention is achieved by the following technical solutions:

[0012] A method for synthesizing DL-lysine, comprising:

[0013] S10, DL-lysine crude product preparation step: dissolving L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, heating and stirring for racemization, obtaining DL-lysine crude product after racemization, and decolorizing the DL-lysine crude product with activated carbon to obtain a DL-lysine crude product aqueous solution;

[0014] S20, DL-lysine finished product preparation step: the DL-lysine crude product aqueous solution is desalted by an electrodialysis device, cooled for crystallization, filtered and dried to obtain the DL-lysine finished product.

[0015] Further, the synthesis method of DL-Lysine comprises:

[0016] S10, a step of preparing a crude DL-lysine product: dissolving L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, heating and stirring to perform racemization, obtaining a crude DL-lysine product after racemization, and decolorizing the crude DL-lysine product with activated carbon to obtain a crude DL-lysine product aqueous solution;

[0017] S20, DL-lysine finished product preparation step: pumping the DL-lysine crude aqueous solution into the electrolytic cell of the electrodialysis device, applying power for 1-2 hours, collecting the DL-lysine finished aqueous solution from the fresh water phase, cooling and crystallizing, filtering and drying to obtain the DL-lysine finished product.

[0018] Further, in S10, in the step of preparing crude DL-lysine: dissolving L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, heating and stirring, obtaining crude DL-lysine after racemization, and decolorizing the crude DL-lysine with activated carbon to obtain a crude DL-lysine aqueous solution.

[0019] Furthermore, in S10, the step of preparing crude DL-lysine: the volume ratio of water to glacial acetic acid in the mixed solution of water and glacial acetic acid is 1:1.

[0020] Furthermore, in S10, the step of preparing crude DL-lysine: the mass volume ratio of the L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is 10: (20-30) kg / L, and the stirring and heating temperature is 80-100°C.

[0021] Furthermore, in S10, the step of preparing crude DL-lysine: the mass ratio of the activated carbon to the L-lysine hydrochloride is 1:5.

[0022] Furthermore, in S10, in the step of preparing crude DL-lysine: the racemization time is 60-90 min.

[0023] Furthermore, in S20, in the step of preparing the DL-lysine finished product: the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.30-0.36 mm; the electrodialysis equipment uses an alloy cathode membrane with a dry basis thickness of 0.34-0.40 mm.

[0024] Furthermore, in S20, in the step of preparing the DL-lysine finished product: the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.30 mm; the electrodialysis equipment uses an alloy cathode membrane with a dry basis thickness of 0.34 mm.

[0025] Furthermore, in S20, DL-lysine finished product preparation step: the cooling crystallization temperature is not greater than 10°C.

[0026] Furthermore, in S20, DL-lysine finished product preparation step: the cooling crystallization temperature is 5-10°C.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The synthesis method of the present invention is to dissolve L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, decolorize it with activated carbon after racemization, desalt the crude DL-lysine solution through an electrodialysis device, cool it for crystallization, and obtain the DL-lysine finished product after drying. The present invention avoids the use of microwave racemization, avoids the introduction of catalysts, avoids passing through ion exchange columns, improves the yield, and reduces the reaction time; the experimental conditions are easy to achieve, the operation steps are reduced, the amount of organic reagents used is reasonable, the process route is short, the reaction conditions are mild, the hydrolysis products are small, and it is suitable for large-scale production. The present invention adopts the method of desalination of electrodialysis equipment, which not only improves the speed and yield of DL-lysine hydrochloride desalination, but also can recycle and reuse the mother liquor.

[0029] 2. The present invention optimizes the parameters of each step. When preparing DL-lysine, if one of the parameters has a deviation of more than 10%, the optical rotation of DL-lysine is basically unqualified; in the step of preparing crude DL-lysine, if the mass volume ratio of L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is greater than 10:20 kg / L, and the stirring and heating temperature is lower than 80°C, the racemization time needs to be as long as 5 hours; if the mass volume ratio of L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is less than 10:30 kg / L, the stirring and heating temperature is lower than 80°C, and .... The mixing and heating temperature is greater than 100°C, which will not have any effect on the racemization result. Both situations will consume a lot of energy in industrial production. In the preparation step of crude DL-lysine, if the mass ratio of activated carbon to the L-lysine hydrochloride is less than 1:5, the decolorization is not thorough enough and does not meet the requirements of the properties of the DL-lysine finished product. DL-lysine is a white crystalline powder. If the mass ratio of activated carbon to the L-lysine hydrochloride is greater than 1:5, the decolorization effect is the same as that of 1:5, which increases the amount of activated carbon used and the production cost is high. If the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of less than 0.30 mm and an alloy anion membrane with a dry basis thickness of less than 0.34 mm, the desalination effect is poor, resulting in a decrease in content; if the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness greater than 0.36 mm and an alloy anion membrane with a dry basis thickness greater than 0.40 mm, the yield will be reduced; if the cooling crystallization temperature is greater than 10°C, the yield is relatively low; if the cooling crystallization temperature is less than 5°C, the yield is not greatly affected, but the energy consumption is relatively large; therefore, the present invention controls the above parameters and material ratios to obtain high-content, high-yield products, while also greatly reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The schematic diagram is a flow chart of the synthesis method of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment. Unless otherwise specified, the materials and equipment used in this embodiment can be purchased from the market.

[0032] Please refer to Figure 1 As shown, a method for synthesizing DL-lysine comprises:

[0033] S10, DL-lysine crude product preparation step: dissolving L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, heating and stirring for racemization, obtaining DL-lysine crude product after racemization, and decolorizing the DL-lysine crude product with activated carbon to obtain a DL-lysine crude product aqueous solution;

[0034] S20, DL-lysine finished product preparation step: the DL-lysine crude product aqueous solution is desalted by an electrodialysis device, cooled for crystallization, filtered and dried to obtain the DL-lysine finished product.

[0035] The synthetic route diagram of the present invention is as follows:

[0036]

[0037] As a preferred embodiment, the synthesis method of DL-Lysine comprises:

[0038] S10, a step of preparing a crude DL-lysine product: dissolving L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, heating and stirring to perform racemization, obtaining a crude DL-lysine product after racemization, and decolorizing the crude DL-lysine product with activated carbon to obtain a crude DL-lysine product aqueous solution;

[0039] S20, DL-lysine finished product preparation step: pumping the DL-lysine crude aqueous solution into the electrolytic cell of the electrodialysis device, applying power for 1-2 hours, collecting the DL-lysine finished aqueous solution from the fresh water phase, cooling and crystallizing, filtering and drying to obtain the DL-lysine finished product.

[0040] As a preferred embodiment, in S10, the step of preparing crude DL-lysine: the volume ratio of water to glacial acetic acid in the mixed solution of water and glacial acetic acid is 1:1.

[0041] As a preferred embodiment, in S10, the step of preparing crude DL-lysine: the mass volume ratio of the L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is 10: (20-30) kg / L, and the stirring and heating temperature is 80-100°C. If the mass volume ratio of the L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is greater than 10: 20 kg / L, and the stirring and heating temperature is lower than 80°C, the racemization time needs to be as long as 5 hours; if the mass volume ratio of the L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is less than 10: 30 kg / L, and the stirring and heating temperature is greater than 100°C, there will be no effect on the racemization result. Both of these situations will consume a lot of energy in industrial production.

[0042] As a preferred embodiment, in S10, the step of preparing crude DL-lysine, the mass ratio of the activated carbon to the L-lysine hydrochloride is 1:5. Thus, if the mass ratio of the activated carbon to the L-lysine hydrochloride is less than 1:5, the decolorization is not thorough enough and does not meet the requirements of the properties of the DL-lysine finished product. DL-lysine is a white crystalline powder. If the mass ratio of the activated carbon to the L-lysine hydrochloride is greater than 1:5, the decolorization effect is the same as that of 1:5, the amount of activated carbon used is increased, and the production cost is high.

[0043] As a preferred embodiment, in S10, the step of preparing crude DL-lysine: the racemization time is 60-90 min.

[0044] As a preferred embodiment, in S20, the step of preparing the DL-lysine finished product: the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.30-0.36 mm, and the electrodialysis equipment uses an alloy anion membrane with a dry basis thickness of 0.34-0.40 mm. If the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of less than 0.30 mm, and an alloy anion membrane with a dry basis thickness of less than 0.34 mm, the desalination effect is poor, resulting in a decrease in content; if the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness greater than 0.36 mm, and an alloy anion membrane with a dry basis thickness greater than 0.40 mm, the yield will be reduced.

[0045] As a preferred embodiment, in S20, DL-lysine finished product preparation step: the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.30 mm, and the electrodialysis equipment uses an alloy anion membrane with a dry basis thickness of 0.34 mm.

[0046] As a preferred embodiment, in S20, the step of preparing the DL-lysine finished product: the cooling and crystallization temperature is not greater than 10° C. If the cooling and crystallization temperature is greater than 10° C., the yield is low.

[0047] As a preferred embodiment, in S20, the DL-lysine finished product preparation step: the cooling crystallization temperature is 5-10° C. If the cooling crystallization temperature is greater than 10° C., the yield is low; if the cooling crystallization temperature is less than 5° C., the yield is not greatly affected, but the energy consumption is high.

[0048] Embodiment 1:

[0049] A method for synthesizing DL-lysine, comprising:

[0050] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 10 L of water and 10 L of glacial acetic acid, stirring and heating to 80° C., racemizing for 90 min to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 2 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0051] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device. The electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.30 mm and an alloy negative membrane with a dry basis thickness of 0.34 mm. The power is turned on for 1-2 hours, and the fresh water phase solution is collected, cooled to 5-10°C for crystallization, and dried to obtain 7.73 kg of DL-lysine finished product.

[0052] The content of DL-lysine in the finished product was determined by titration and was 99.5%.

[0053] The optical rotation of the finished DL-lysine product was 0 when tested by Autopol IV micropolarimeter.

[0054] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 7.73 ÷ 10 × 100% = 77.3%.

[0055] Embodiment 2:

[0056] A method for synthesizing DL-lysine, comprising:

[0057] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 15 L of water and 15 L of glacial acetic acid, stirring and heating to 100° C., racemizing for 60 min to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 2 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0058] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device, the electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.30 mm and an alloy negative membrane with a dry basis thickness of 0.34 mm, the power is turned on for 1-2 hours, the fresh water phase solution is collected, cooled to 5-10°C for crystallization, and dried to obtain 7.9 kg DL-lysine finished product.

[0059] The content of DL-lysine in the finished product was determined by titration and was 99.6%.

[0060] The optical rotation of the finished DL-lysine product was measured by Autopol IV micropolarimeter and was 0.01.

[0061] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 7.9÷10×100% = 79%.

[0062] Embodiment 3:

[0063] A method for synthesizing DL-lysine, comprising:

[0064] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 10 L of water and 10 L of glacial acetic acid, stirring and heating to 90° C., racemizing for 90 min to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 2 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0065] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device, the electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.30 mm and an alloy negative membrane with a dry basis thickness of 0.34 mm, the power is turned on for 1-2 hours, the fresh water phase solution is collected, cooled to 5-10°C for crystallization, and 8.07 kg of DL-lysine finished product is obtained after drying.

[0066] The content of DL-lysine in the finished product was determined by titration and was 99.2%

[0067] The optical rotation of the finished DL-lysine product was -0.02 as measured by Autopol IV micropolarimeter.

[0068] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 8.07÷10×100% = 80.7%.

[0069] Embodiment 4:

[0070] A method for synthesizing DL-lysine, comprising:

[0071] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 10 L of water and 10 L of glacial acetic acid, stirring and heating to 80° C., racemizing for 90 min to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 1.5 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0072] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device, the electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.30 mm and an alloy negative membrane with a dry basis thickness of 0.34 mm, the power is turned on for 1-2 hours, the fresh water phase solution is collected, cooled to 5-10°C for crystallization, and 8.35 kg of DL-lysine finished product is obtained after drying.

[0073] The content of DL-lysine in the finished product was determined by titration and was 99.2%.

[0074] The optical rotation of the finished DL-lysine product was -0.01 as measured by Autopol IV micropolarimeter.

[0075] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 8.35÷10×100% = 83.5%.

[0076] Embodiment 5:

[0077] A method for synthesizing DL-lysine, comprising:

[0078] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 8 L of water and 8 L of glacial acetic acid, stirring and heating to 70°C, racemizing for 5 hours to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 2 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0079] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device. The electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.30 mm and an alloy negative membrane with a dry basis thickness of 0.34 mm. The power is turned on for 1-2 hours, and the fresh water phase solution is collected, cooled to 18°C ​​for crystallization, and dried to obtain 7.56 kg of DL-lysine finished product.

[0080] The content of DL-lysine in the finished product was determined by titration and was 99.1%

[0081] The optical rotation of the finished DL-lysine product measured by Autopol IV micropolarimeter was 0.71, which did not meet the requirement (±0.50).

[0082] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 7.56 ÷ 10 × 100% = 75.6%.

[0083] It can be seen from this example that, since the mass volume ratio of L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is 10:16 kg / L, which is greater than 10:20 kg / L, and the stirring and heating temperature is 70°C, which is lower than 80°C, the racemization time needs to be as long as 5 hours. At the same time, since the cooling crystallization temperature is 18°C>10°C, the yield is low.

[0084] Embodiment 6:

[0085] A method for synthesizing DL-lysine, comprising:

[0086] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 10 L of water and 10 L of glacial acetic acid, stirring and heating to 90° C., racemizing for 90 min to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 2 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0087] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device, the electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.26 mm and an alloy negative membrane with a dry basis thickness of 0.30 mm, the power is turned on for 1-2 hours, the fresh water phase solution is collected, cooled to 5-10°C for crystallization, and 8.41 kg of DL-lysine finished product is obtained after drying.

[0088] The content of DL-lysine in the finished product was determined by titration method to be 98.1%, which did not meet the requirement (>98.5%).

[0089] The optical rotation of the finished DL-lysine product was -0.02 as measured by Autopol IV micropolarimeter.

[0090] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 8.41 ÷ 10 × 100% = 84.1%.

[0091] It can be seen from this embodiment that since the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.26mm less than 0.30mm and an alloy anion membrane with a dry basis thickness of 0.30mm less than 0.34mm, the desalination effect is poor, resulting in the content being reduced to 98.1%, which does not meet the requirements (>98.5%).

[0092] Embodiment 7:

[0093] A method for synthesizing DL-lysine, comprising:

[0094] S10, DL-lysine crude product preparation step: dissolving 10 kg of L-lysine hydrochloride in a mixed solution of 12 L of water and 12 L of glacial acetic acid, stirring and heating to 80° C., racemizing for 90 min to obtain DL-lysine crude product, decolorizing the DL-lysine crude product with 2 kg of activated carbon, and filtering to obtain a DL-lysine crude product aqueous solution;

[0095] S20, DL-lysine finished product preparation steps: DL-lysine crude aqueous solution is pumped into the electrolytic cell of the electrodialysis device, the electrodialysis equipment uses an alloy positive membrane with a dry basis thickness of 0.40 mm and an alloy negative membrane with a dry basis thickness of 0.44 mm, the power is turned on for 1-2 hours, the fresh water phase solution is collected, cooled to 5-10°C for crystallization, and dried to obtain 6.81 kg of DL-lysine finished product.

[0096] The content of DL-lysine in the finished product was determined by titration and was 99.3%

[0097] The optical rotation of the finished DL-lysine product was -0.02 as measured by Autopol IV micropolarimeter.

[0098] In this embodiment, DL-lysine yield = DL-lysine finished product weight / L-lysine weight × 100%; DL-lysine yield = 6.81 ÷ 10 × 100% = 68.1%.

[0099] It can be seen from this embodiment that the yield is reduced because the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.40 mm greater than 0.36 mm and an alloy anion membrane with a dry basis thickness of 0.44 mm greater than 0.40 mm.

[0100] The above implementation modes are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for synthesizing DL-lysine, characterized in that: include: S10, a step of preparing a crude DL-lysine product: dissolving L-lysine hydrochloride in a mixed solution of water and glacial acetic acid, heating and stirring to perform racemization, obtaining a crude DL-lysine product after racemization, and decolorizing the crude DL-lysine product with activated carbon to obtain a crude DL-lysine product aqueous solution; S20, DL-lysine finished product preparation step: pumping the DL-lysine crude aqueous solution into the electrolytic cell of the electrodialysis device, applying power for 1-2 hours, collecting the DL-lysine finished aqueous solution from the fresh water phase, cooling and crystallizing, filtering and drying to obtain the DL-lysine finished product; the electrodialysis equipment uses an alloy cation membrane with a dry basis thickness of 0.30 mm; the electrodialysis equipment uses an alloy anion membrane with a dry basis thickness of 0.34 mm.

2. The method for synthesizing DL-lysine according to claim 1, wherein S10, in the step of preparing crude DL-lysine: the volume ratio of water to glacial acetic acid in the mixed solution of water and glacial acetic acid is 1:

1.

3. The method for synthesizing DL-lysine according to claim 1, wherein S10, in the step of preparing crude DL-lysine: the mass volume ratio of the L-lysine hydrochloride to the mixed solution of water and glacial acetic acid is 10: (20-30) kg / L, and the stirring and heating temperature is 80-100°C.

4. The method for synthesizing DL-lysine according to claim 1, wherein S10, in the step of preparing crude DL-lysine: the mass ratio of the activated carbon to the L-lysine hydrochloride is 1:

5.

5. The method for synthesizing DL-lysine according to claim 1, wherein S10, in the step of preparing crude DL-lysine: the racemization time is 60-90 min.

6. The method for synthesizing DL-lysine according to claim 1, characterized in that: S20, in the step of preparing the DL-lysine finished product: the cooling crystallization temperature is not greater than 10°C.

7. The method for synthesizing DL-lysine according to claim 6, wherein S20, in the step of preparing the DL-lysine finished product: the cooling and crystallization temperature is 5-10°C.

Images