A method and system for preparing a product of l-carnitine

Abstract

The application provides a preparation method and system of L-carnitine products. The method and system are used for preparing L-carnitine products, and have high production efficiency. The prepared L-carnitine products are not easy to be caked, the purity of the L-carnitine products is more than 96%, and the water content is less than 1 wt%. The prepared L-carnitine products are refined, and the refined L-carnitine products have high yield and high purity. The method and system are suitable for large-scale production.

Description

Technical Field

[0001] This application belongs to the field of health food raw material production, specifically involving a method and system for preparing L-carnitine products. Background Technology

[0002] L-carnitine, also known as L-carnitine or L-carnitine, is a compound with multiple physiological activities. Its main functions include promoting fatty acid β-oxidation, regulating the acyl ratio in mitochondria, and influencing energy metabolism. L-carnitine can also participate in the transport of branched-chain amino acid metabolites, thereby promoting the normal metabolism of branched-chain amino acids. L-carnitine also plays an important role in the elimination and utilization of ketone bodies. It can act as a biological antioxidant to scavenge free radicals, maintain membrane stability, and improve animal immunity and disease resistance and stress resistance. Therefore, L-carnitine products are widely used in the food, feed, pharmaceutical, and cosmetic industries. Summary of the Invention

[0003] L-carnitine readily absorbs moisture and liquefies, therefore, the moisture content is extremely critical during the preparation of L-carnitine products. Conventional drying equipment such as ovens and scraped-film dryers are insufficient to achieve the required drying conditions for L-carnitine aqueous solutions. Applying rake dryers, commonly used in the production of health food ingredients, to the drying of L-carnitine products typically requires over 16 hours to dry a single batch. This excessively long drying time not only reduces production efficiency but also increases the impurity content in the L-carnitine products, affecting their quality. Currently available technologies for drying L-carnitine solutions are highly complex and unsuitable for industrial production.

[0004] Therefore, there is an urgent need to develop an efficient method for preparing L-carnitine products suitable for industrial production.

[0005] This application aims to address at least one of the technical problems existing in the prior art to a certain extent. Therefore, this application provides a method and system for preparing L-carnitine products.

[0006] This application is based on the following discoveries of the inventors.

[0007] Currently, the industrial production of L-carnitine faces the following problems:

[0008] 1. The L-carnitine products prepared by industrial production have a drying loss of more than 1% and are extremely hygroscopic.

[0009] 2. In industrial production, the use of rake dryers to dry low-content L-carnitine solutions not only results in long drying times but also leads to products with very high impurity content.

[0010] 3. In industrial production, the yield of L-carnitine products with high water content is very low when using inexpensive anhydrous ethanol to refine them. Therefore, anhydrous ethanol and acetone are often mixed to refine L-carnitine products, which leads to higher production costs.

[0011] Existing technology CN209612224U discloses a method for directly feeding a low-content L-carnitine solution into a rake dryer for drying. The inventors found that drying a batch of material usually takes more than 16 hours, and the dried product has a high level of croton betaine impurities. Existing technology CN101912045B discloses a method for drying L-carnitine solution using a spray dryer. This method can only control the moisture content of L-carnitine products to be below 4%. Existing technology CN111233686A discloses a method for recrystallizing L-carnitine. When using inexpensive anhydrous ethanol to recrystallize L-carnitine products (crude L-carnitine, which is an oily substance), the yield of refined product is only 50.5%, and the purity is 90.0%. When using a mixture of ethanol and acetone (ethanol and acetone mass ratio of 1:1) to recrystallize L-carnitine products, 1 gram of crude product requires 8 grams of solvent, and the highest yield of refined product is 85.6%, and the highest purity is 99.53%.

[0012] In a first aspect, this application discloses a method for preparing L-carnitine products. According to an embodiment of this application, the specific steps for preparing the L-carnitine products are as follows: a solution with an L-carnitine content of 30-60 wt% is dried using a thin-film evaporator for only 3.5-6.5 hours to obtain an L-carnitine product with a purity of over 96% and a moisture content of less than 1 wt%.

[0013] According to the embodiments of this application, the heat transfer methods for drying the solution with a L-carnitine content of 30-60 wt% using the thin-film evaporator are, in order: steam heat transfer and water heat transfer.

[0014] According to an embodiment of this application, in order to achieve efficient drying while reducing the generation of by-products, when the thin-film evaporator uses steam to transfer heat to the solution, the temperature of the solution is controlled at 60-90°C, and the pressure inside the thin-film evaporator is controlled at -0.05--0.1 MPa.

[0015] According to an embodiment of this application, when the solvent content in the solution in the thin-film evaporator reaches 5-20 wt%, the heat transfer mode of the thin-film evaporator is adjusted to water heat transfer at 60-90°C.

[0016] When the moisture content of the material in the thin film evaporator is less than 1 wt%, adjust the heat transfer mode of the thin film evaporator to 20-30℃ water heat transfer, control the temperature inside the thin film evaporator to drop to 30-40℃, and then the material can be discharged.

[0017] In this application, by switching the above three heat transfer methods, precise temperature control can be achieved during the material drying process, further improving drying efficiency and ensuring that the purity of the prepared L-carnitine product is above 96% and the moisture content is below 1%.

[0018] This application achieves a high yield of L-carnitine products with high purity and a moisture content of less than 1 wt% in a short time by controlling the concentration of materials entering the thin-film evaporator. Furthermore, the inventors unexpectedly discovered that refining the L-carnitine products prepared in this application with anhydrous ethanol yields a high-quality L-carnitine product with a single-pass yield exceeding 90% and a purity exceeding 99.4%.

[0019] According to an embodiment of this application, the material with an L-carnitine content of 30-60 wt% is an aqueous solution with an L-carnitine content of 30-60 wt%. According to an embodiment of this application, the aqueous solution with an L-carnitine content of 30-60 wt% can be prepared by the following method:

[0020] (1) S-epoxychloropropane was amination and cyanation to obtain L-carnenitrile;

[0021] (2) L-carnitine hydrolyzes under acidic conditions to give L-carnitine hydrochloride;

[0022] (3) After dilution, L-carnitine hydrochloride is subjected to ion exchange or electrodialysis to remove impurities, resulting in a 5-20 wt% L-carnitine aqueous solution.

[0023] (4) The 5-20 wt% L-carnitine aqueous solution was concentrated to obtain an aqueous solution with an L-carnitine content of 30-60 wt%.

[0024] According to the embodiments of this application, there are no limitations on the method for concentrating a 5-20 wt% L-carnitine aqueous solution; it can be single-effect evaporation or multi-effect evaporation. After further concentrating the 5-20 wt% L-carnitine solution to a content of 30-60 wt%, it is then sent to a thin-film evaporator to evaporate the solvent, and the resulting product is the L-carnitine product.

[0025] According to the embodiments of this application, unless otherwise specified, the yield of recrystallization in one step refers to the ratio of the product mass obtained by recrystallization in only one step to the product mass contained in the feed.

[0026] According to the embodiments of this application, unless otherwise specified, refining refers to recrystallization.

[0027] In a second aspect of this application, a L-carnitine product prepared using the above method is proposed.

[0028] According to the embodiments of this application, the L-carnitine in the L-carnitine product has a purity of 96% and a moisture content of less than 1 wt%.

[0029] The L-carnitine product prepared in this application can be purified with anhydrous ethanol, achieving a yield of over 90% in a single step, with a product purity of over 99.4%. This high-quality L-carnitine product can be used in the food, pharmaceutical, and animal feed industries.

[0030] In a third aspect, this application provides a system for preparing the aforementioned L-carnitine product. According to an embodiment of this application, the system for preparing the L-carnitine product comprises:

[0031] Pretreatment unit, adjusts the L-carnitine content in L-carnitine solution to 30-60 wt%;

[0032] The drying unit removes the solvent from the pretreated L-carnitine solution, resulting in L-carnitine products with a purity of over 96% and a moisture content of less than 1 wt%.

[0033] According to an embodiment of this application, the drying unit is a thin-film evaporator, preferably a transfer film evaporator.

[0034] The pretreatment unit of this application is used to adjust the L-carnitine content in the L-carnitine-containing solution to 30-60%, and then the pretreated L-carnitine solution is sent to the drying unit to further remove the solvent. In this application, the pretreatment unit and the drying unit are used in combination. The pretreatment unit controls the concentration of the L-carnitine solution entering the drying unit, and the drying unit is used for further drying and discharging of the L-carnitine solution. The combination of the two can achieve a high yield of L-carnitine products with high purity and a moisture content of less than 1 wt% in a short time.

[0035] In this application, the drying unit can be a thin-film evaporator. To increase the heat transfer area of ​​the equipment and further improve the heat transfer efficiency, heat transfer sleeves and / or heat transfer coils can also be installed inside the thin-film evaporator.

[0036] In this application, the heat transfer coil in the thin-film evaporator can also be configured as a movable coil and equipped with a scraper. The movable heat transfer coil also has a stirring function, which can make the heat transfer between materials more uniform. The scraper equipped on the movable heat transfer coil can crush the materials, further increasing the heating area of ​​the materials and avoiding the phenomenon of solvent being trapped in the agglomerated materials due to material agglomeration.

[0037] In a fourth aspect of this application, a method for refining the above-mentioned L-carnitine product is proposed, specifically, the L-carnitine product is refined using anhydrous ethanol as a solvent.

[0038] According to the present invention, preferably, the mass ratio of the L-carnitine product to anhydrous ethanol is 1:3 to 1:6.

[0039] Using the system of this application, 30-60 wt% L-carnitine material is dried using a thin-film evaporator, yielding a high-purity L-carnitine product with a moisture content of less than 1 wt% within 3.5-6.5 hours. Furthermore, the inventors unexpectedly discovered that refining the L-carnitine product obtained in this application with anhydrous ethanol can achieve a single-pass yield of over 90% and a product purity of over 99.4%.

[0040] Compared with the prior art, this application has the following advantages:

[0041] 1. This application uses a thin-film evaporator to dry a 30-60 wt% L-carnitine solution, and an L-carnitine product with a purity of over 96% and a moisture content of less than 1% can be obtained within 3.5-6.5 hours. The process is simple and suitable for industrial production.

[0042] 2. The L-carnitine product prepared in this application does not require the use of acetone reagent. Only a small amount of anhydrous ethanol is needed to complete the purification of the product. The one-time yield of purification is as high as 90% or more, and the product purity can reach 99.4% or more. Using inexpensive anhydrous ethanol as a solvent can reduce the cost of industrial production. The purified L-carnitine can also be used directly in food, medicine and feed.

[0043] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application.

[0044] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this application but do not exclude other contents.

[0045] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0046] The present application's solution will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0047] Example 1: Preparation of aqueous solutions with L-carnitine contents of 10%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, and 70wt%.

[0048] The specific steps are as follows:

[0049] (1) S-epoxychloropropane was amination and cyanation to obtain L-carnenitrile;

[0050] (2) L-carnitine hydrochloride was obtained by hydrolysis with hydrochloric acid;

[0051] (3) After diluting L-carnitine hydrochloride with water, impurities were removed by electrodialysis and concentrated by double-effect evaporation to obtain aqueous solutions with L-carnitine contents of 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, and 70wt%, respectively.

[0052] Example 2: Preparation of L-carnitine products

[0053] The solutions obtained in Example 1 were pumped into 200L film-film evaporators. In the film-film evaporator, the solutions were first heated with steam, maintaining a temperature of 60–90°C and a pressure of -0.05–-0.1 MPa, until the moisture content reached 5–20 wt%. Then, the temperature was adjusted to 60–90°C for water heating until the moisture content was less than 1 wt%. Finally, the temperature was adjusted to 20–30°C for circulating water cooling until the material temperature in the film evaporator dropped to 30–40°C, at which point the material was discharged.

[0054] Table 1 lists the purity, feed rate, and theoretical output of the dried L-carnitine product for the seven different concentrations of L-carnitine concentrate before entering the transfer evaporator. Table 2 lists the drying time of the seven different concentrations of L-carnitine concentrate after entering the transfer evaporator, from the start of heating to evaporation until the moisture content is less than or close to 1%, as well as the actual output, moisture content, and purity of the dried material.

[0055] Table 1

[0056]

[0057]

[0058] Table 2

[0059]

[0060] According to the evaporation results in Table 2, when the feed concentration is 10 wt%, the evaporation time exceeds 22 hours, resulting in very high energy consumption, very low theoretical yield, and low production efficiency. Furthermore, due to the thick adhesion of the material to the walls during discharge, the actual purity of the discharged material is low, and the yield of L-carnitine products (actual yield * purity / theoretical yield) is also very low. When the feed concentration is 20 wt%, the evaporation time exceeds 6.5 hours, the theoretical yield is also very low, and the production efficiency is low. Again, due to the thick adhesion of the material to the walls during discharge, the actual purity of the discharged material is low, and the yield of L-carnitine products is also very low. When the feed concentration is 70 wt%, there is no dissolution process, leading to uneven moisture content in the discharged material. Additionally, due to the thick adhesion of the material to the walls during discharge, the actual yield is also low. Moreover, when the feed concentrations are 10 wt%, 20 wt%, and 70 wt%, the moisture content of the discharged material cannot be controlled below 1%. Considering the evaporation time, output rate, and output moisture content, the optimal feed concentration is 30wt% to 60wt%.

[0061] Example 3: Refining L-carnitine products using anhydrous ethanol

[0062] The seven different L-carnitine products obtained in Example 2 were purified using anhydrous ethanol. 10g of each of the seven L-carnitine products prepared in Example 2 was placed into seven different round-bottom flasks (100mL each), and each flask was numbered, corresponding to the discharge number in Example 2. Anhydrous ethanol (30g–60g) was added to each flask, and the mixture was heated while stirring until the sample was completely dissolved. Heating was then stopped, and the mixture was cooled in an ice bath to allow crystallization. After overnight filtration, the purified L-carnitine product was obtained, dried in an oven, weighed, and its purity was determined. The first-pass yield and product purity are shown in Table 3.

[0063] Table 3

[0064]

[0065] As shown in Table 3, after drying a 30wt% to 60wt% L-carnitine solution in a thin-film evaporator, L-carnitine products are obtained. Then, they are recrystallized with anhydrous ethanol. The weight ratio of L-carnitine products to anhydrous ethanol is 1:3 to 1:6. The yield of the first purification exceeds 90%, and the purity of the obtained product is higher than 99.4%.

[0066] Comparative example: Refining L-carnitine products using anhydrous ethanol and acetone.

[0067] The seven different L-carnitine products obtained in Example 2 were purified using anhydrous ethanol and acetone. 10g of each of the seven L-carnitine products prepared in Example 2 was placed into seven clean round-bottom flasks (100mL each), and each flask was numbered corresponding to the discharge number from Example 2. A mixed solvent of anhydrous ethanol and acetone (50g–80g) was added to each flask (mass ratio of anhydrous ethanol to acetone 1:1). The mixture was heated while stirring until the sample was completely dissolved. Heating was then stopped, and the mixture was cooled in an ice bath to allow crystallization. After overnight filtration, the purified L-carnitine product was obtained, dried in an oven, weighed, and its purity was determined. The first-pass yield and product purity are shown in Table 4.

[0068] Table 4

[0069]

[0070] As shown in Table 4, after drying a 30wt% to 60wt% L-carnitine solution in a thin-film evaporator, L-carnitine products are obtained. These products are then recrystallized using a mixed solvent of anhydrous ethanol and acetone. The weight ratio of L-carnitine products to anhydrous ethanol is 1:5 to 1:8. The yield of the purified product exceeds 95% in one step, and the purity of the obtained product is higher than 99.4%.

[0071] The L-carnitine products prepared by existing technologies, when recrystallized from crude L-carnitine (which is an oily substance) using inexpensive anhydrous ethanol, have a yield of only 50.5% and a purity of 90.0%. When recrystallized from L-carnitine using a mixture of ethanol and acetone (ethanol and acetone in a mass ratio of 1:1), 8 grams of solvent are required for 1 gram of crude product, and the highest yield of refined product is 85.6%, with a highest purity of 99.53%.

[0072] The L-carnitine products prepared using the methods and / or systems described in this application can achieve high yields of high-purity L-carnitine, regardless of whether recrystallization is performed using anhydrous ethanol or a mixture of ethanol and acetone. In industrial production, to save costs and reduce processes, recrystallization using anhydrous ethanol is most suitable after preparing the L-carnitine products using the methods and / or systems described in this application.

[0073] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing L-carnitine products, characterized in that, A solution containing 30–60 wt% L-carnitine was dried using a thin-film evaporator to obtain L-carnitine products with a purity of over 96% and a moisture content of less than 1%.

2. The method according to claim 1, characterized in that, The heat transfer methods for drying the solution with a L-carnitine content of 30-60 wt% using the thin-film evaporator are, in order: steam heat transfer and water heat transfer.

3. The method according to claim 2, characterized in that, When the thin-film evaporator uses steam to transfer heat to the solution, the temperature of the solution is controlled at 60-90°C, and the pressure inside the thin-film evaporator is controlled at -0.05--0.1 MPa.

4. The method according to claim 3, characterized in that, When the solvent content in the solution in the thin film evaporator reaches 5-20 wt%, the heat transfer mode of the thin film evaporator is adjusted to water heat transfer at 60-90°C. When the water content in the solution inside the thin-film evaporator is less than 1 wt%, the heat transfer mode of the thin-film evaporator is adjusted to water heat transfer at 20-30°C. When the temperature inside the thin-film evaporator drops to 30-40°C, the material can be discharged.

5. The method according to claim 2, characterized in that, The solution containing 30-60 wt% L-carnitine is an aqueous solution containing 30-60 wt% L-carnitine.

6. The L-carnitine product prepared by the method according to any one of claims 1-5, characterized in that, The L-carnitine in the L-carnitine product has a purity of not less than 96 wt% and a moisture content of not more than 1 wt%.

7. A system for preparing the L-carnitine product of claim 6, characterized in that, Include: Pretreatment unit, adjusts the L-carnitine content in L-carnitine solution to 30-60 wt%; The drying unit removes the solvent from the pretreated L-carnitine solution, resulting in L-carnitine products with a purity of over 96% and a moisture content of less than 1 wt%.

8. The system according to claim 7, characterized in that, The drying unit is a thin-film evaporator; preferably, the thin-film evaporator is a transfer film evaporator.

9. The system according to claim 8, characterized in that, The thin-film evaporator is equipped with a heat transfer jacket and / or a heat transfer coil. Preferably, the heat transfer coil is a movable coil and is equipped with a scraper.

10. A method for refining the L-carnitine product according to claim 6 or the L-carnitine product prepared according to any one of claims 7-9, characterized in that, The L-carnitine product was refined using anhydrous ethanol as a solvent; Preferably, the mass ratio of the L-carnitine product to anhydrous ethanol is 1:3 to 1:6.

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