A method for separating natural vitamin e impurities

Abstract

This invention provides a method for separating impurities from natural vitamin E, comprising the following steps: S1, filling lipase into first and second stage fixed-bed reactors, and filling a mixture of activated carbon and kaolin into the third stage; S2, feeding the raw material solution into the first stage, causing the polyunsaturated free fatty acids and free sterols in the raw material solution to undergo esterification, and after the circulation reaction, feeding the reaction solution into the second stage; S3, simultaneously adding medium- and low-carbon chain fatty acids into the second stage, causing them to undergo esterification with the remaining free sterols, and after the circulation reaction, feeding the reaction solution into the third stage; S4, adsorbing benzo[a]pyrene and colloidal impurities to obtain a mixture containing medium- and low-carbon chain fatty acids, mixed fatty acid esters, and natural vitamin E; S5, feeding the mixture obtained in step S4 into a three-stage molecular distillation process to obtain the natural vitamin E product. This method is simple and can effectively remove free sterols and free fatty acids from crude natural vitamin E.

Description

Technical Field

[0001] This invention relates to the field of natural product separation and purification technology, and in particular to a method for separating natural vitamin E impurities. Background Technology

[0002] Natural vitamin E is a type of fat-soluble vitamin, mainly comprising two categories: tocopherols and tocotrienols. It possesses important physiological functions such as anti-oxidation, anti-aging, and cardiovascular protection. Natural vitamin E is primarily extracted from deodorizer distillates (DD) of vegetable oils and is an important byproduct of the oil refining process.

[0003] Purifying and concentrating natural vitamin E from soybean and other oilseed distillates can enhance the comprehensive utilization value of these crops while reducing environmental pollution from distillate emissions. Leveraging the vast domestic and international market for natural tocopherols and my country's resource advantages, developing this technology has significant economic and social benefits.

[0004] Currently, the natural vitamin E end-market is mainly dominated by mixed vitamin E series products with a content of 50%-90%. The series products required by the end-market need to be purified by one or more methods such as chromatography, extraction, and ion exchange. However, after using vegetable oil deodorized distillate as raw material and undergoing processes such as methyl esterification, cold precipitation, and solid-liquid separation, the solid and liquid are then subjected to molecular distillation to obtain crude natural vitamin E 50% concentrated oil. This crude product has problems such as many impurities, low specific rotation, and high levels of benzo[a]pyrene, which do not meet national standards and cannot be directly sold to end customers.

[0005] Various crude natural vitamin E products were extracted from deodorized distillates of various vegetable oils. These products contained free sterols (10%-30%), free fatty acids (1%-10%), triglycerides (10-40%), benzo[a]pyrene (approximately 1000 ppm), and colloids. The free fatty acids contained in these products are often polyunsaturated fatty acids, and their composition and physical properties are similar to those of natural vitamin E, making them difficult to separate effectively using conventional physical separation methods. Furthermore, due to their restricted spatial structure, polyunsaturated fatty acids often cannot be removed by conventional enzymatic esterification. Since vitamin E itself is easily oxidized, using conventional enzymatic esterification methods would result in vitamin E loss.

[0006] Traditional methods such as cold crystallization can leave significant residues of free sterols. Further purification of natural vitamin E will increase sterol concentration, ultimately affecting the quality of the vitamin E.

[0007] Conventional techniques typically involve separating impurities from crude natural vitamin E through one or more methods such as extraction, column chromatography, ion exchange, molecular distillation, or rectification. However, when using molecular distillation, the separation is incomplete because vitamin E has similar boiling points to sterols and polyunsaturated fatty acids. Column chromatography, extraction, and ion exchange all suffer from problems such as the use of large amounts of solvents, high energy consumption, and significant environmental impact. Furthermore, these methods can cause partial changes in the vitamin E composition during purification, resulting in incomplete separation.

[0008] CN103012351 discloses a method using alcohols and hydrocarbon solvents as extractants, mixing and dissolving crude natural vitamin E in a certain proportion at 40-60℃, cooling to 0-10℃ to allow solid precipitation, filtering, and then removing the solvent by vacuum distillation to obtain natural vitamin E. However, this method uses a large amount of organic solvent, generating a large amount of wastewater pollution, and the removal of impurities is incomplete.

[0009] CN1253951A discloses a method for extracting and concentrating natural vitamin E using supercritical CO2, including a multi-stage continuous separation process of extraction and distillation columns. However, the yield of this method is low, only 48%-65%, and the supercritical CO2 extraction method requires high-end equipment and is expensive.

[0010] CN115650943B involves adding urea to form a sterol-urea inclusion complex, leaving urea residue, and then removing impurities through methods such as cold precipitation. This method introduces new impurities, thus limiting the safety of the product.

[0011] CN103965155B combines molecular distillation technology with column chromatography to obtain high-purity natural vitamin E and high-quality natural vitamin E that meets quality standards. However, it has drawbacks such as the large amount of solvent used, the generation of a large amount of wastewater during silica gel recovery, and uneven quality of the produced vitamin E.

[0012] CN102584769B describes a process where crude vitamin E is dissolved in ethanol at a certain ratio, followed by cold precipitation and filtration to remove ethanol-insoluble matter. A second-stage adsorption process is then used to remove non-adsorbed impurities such as methyl esters. Vitamin E is then desorbed using a desorbing agent, and the eluent is cold-precipitated to a certain temperature and filtered. A specific desorbing agent is added to remove polycyclic aromatic hydrocarbons and adsorb other impurities. After filtration to remove the desorbing agent, the solution is concentrated and dissolved. Finally, qualified vitamin E is obtained through tertiary molecular distillation. This process is cumbersome and cannot be scaled up for continuous production.

[0013] Additionally, patent CN108299373B (prior document 1) discloses a method for extracting natural vitamin E from deodorized rice bran oil distillate. This method first uses high-vacuum continuous distillation to remove free fatty acids, then performs esterification with lipase, and finally separates and purifies the product to obtain natural vitamin E. The esterification step involves adding lipase as a catalyst and low-carbon alcohols to the material to convert the remaining free fatty acids, glycerides, and sterol esters into fatty acid monoesters, glycerol, and sterols. The lipase used is Novozym 435 or Lipozyme TL. IM; the mass addition amount of the lipase is 0.5%-10.0% of the mass of the deodorized rice bran oil distillate; the low-carbon alcohol is selected from methanol or ethanol; the mass addition amount of the low-carbon alcohol is 10%-30% of the mass of the deodorized rice bran oil distillate; the temperature of the esterification reaction is 40-60℃, and the time is 12-48h; the separation and purification includes centrifuging the mixture after the esterification reaction, recovering the lipase, then recovering the excess low-carbon alcohol under reduced pressure, and finally washing with water to remove glycerol; the temperature of the water washing is 70-90℃; the mixture after washing to remove glycerol is cooled and crystallized and filtered to remove sterols; the cooling, crystallization and filtration to remove sterols steps include: naturally cooling and crystallizing the mixture after the esterification reaction, and filtering to remove sterols after 6-10h.

[0014] Comparative document 1 first uses high-vacuum continuous distillation technology to remove some free fatty acids, then adds lipase catalyst and low-carbon alcohols. The remaining free fatty acids are removed by the low-carbon alcohols under the catalysis of lipase. Glycerol is then removed by washing with water, and sterols are removed by cooling crystallization and filtration. This method has the following disadvantages: ① Because the boiling points of natural vitamin E and free fatty acids are close, while using high vacuum continuous distillation technology to remove some free fatty acids, some natural vitamin E will be carried away, resulting in a decrease in the yield of natural vitamin E products. ② High-vacuum continuous distillation is carried out at high temperatures, which can easily lead to partial oxidation and degradation of natural vitamin E, affecting the yield and stability of natural vitamin E products; ③ After removing some free fatty acids by distillation, and then adding lipase catalyst and low alcohol to remove the remaining free fatty acids, glycerol needs to be removed by washing with water, and sterols need to be removed by cooling crystallization and filtration. This method is complicated. ④ Sterols cannot be completely removed by cooling crystallization and filtration. Summary of the Invention

[0015] Therefore, the present invention provides a simple method for separating impurities in crude natural vitamin E, which can effectively remove free sterols and free fatty acids.

[0016] The above method for separating natural vitamin E impurities includes the following steps: S1. Lipase is filled into the first and second stage fixed-bed reactors of the interconnected three-stage fixed-bed reactor, and a mixture of activated carbon and kaolin is filled into the third stage fixed-bed reactor. S2. The crude natural vitamin E raw material liquid is fed into the first-stage fixed-bed reactor, so that the polyunsaturated free fatty acids and free sterols in the raw material liquid undergo esterification under the catalysis of lipase. After the recycling reaction, the reaction liquid is sent into the second-stage fixed-bed reactor. S3. Simultaneously, medium and low carbon chain fatty acids are added to the second-stage fixed-bed reactor to allow them to undergo esterification with the remaining free sterols. After the cyclic reaction, the reaction solution is sent to the third-stage fixed-bed reactor. S4. The activated carbon and clay mixture in the third-stage fixed-bed reactor adsorbs benzo[a]pyrene and colloidal impurities to obtain a mixture containing medium and low carbon chain fatty acids, mixed fatty acid esters and natural vitamin E. S5. The mixture obtained in step S4 is sent to a tertiary molecular distillation process to obtain a natural vitamin E product.

[0017] Furthermore, in step S2, polyunsaturated free fatty acids and free sterols undergo esterification in a cyclic manner as follows: The upper end of the first-stage fixed-bed reactor is connected to a first container via a first pipeline, and a second container is connected to the first pipeline via a second pipeline. The second container is also connected to the lower end of the first-stage fixed-bed reactor via a third pipeline. A first valve is provided on the side of the first pipeline near the first container, a second valve is provided on the second pipeline, and a third valve is provided on the third pipeline; First, add crude natural vitamin E to the first container, then open the first valve to pump the crude natural vitamin E into the first-stage fixed-bed reactor. After the first-stage fixed-bed reactor is full of material, close the first valve and open the second and third valves to allow the material to circulate in the second container and the first-stage fixed-bed reactor, and a circulating reaction occurs.

[0018] Furthermore, in step S2, polyunsaturated free fatty acids and free sterols undergo esterification in a cyclic manner as follows: The upper end of the first-stage fixed-bed reactor is connected to the upper end of a fifth container through a first passage, and the lower end of the first-stage fixed-bed reactor is connected to the side end of the fifth container through a second passage. The first passage is equipped with a thirteenth valve; First, add crude natural vitamin E to the fifth container, then open the thirteenth valve to pump the crude natural vitamin E into the first-stage fixed-bed reactor, and circulate the material between the fifth container and the first-stage fixed-bed reactor, where a circulating reaction occurs.

[0019] Furthermore, in step S3, the medium- and low-chain fatty acids and the remaining free sterols undergo esterification in a cyclic manner as follows: The upper end of the second-stage fixed-bed reactor is connected to the second receiver via the fourth pipe. Next to the fourth pipe, a third container is connected via the fifth pipe. The third container is also connected to the lower end of the second-stage fixed-bed reactor via the sixth pipe. The first receiver is connected to the second receiver via the seventh pipe. The second receiver is also connected to the lower end of the first-stage fixed-bed reactor via the eighth pipe. The eighth pipeline is equipped with a fourth valve, the seventh pipeline is equipped with a fifth valve, the fourth pipeline is equipped with a sixth valve near the second receiver, the fifth pipeline is equipped with a seventh valve, and the sixth pipeline is equipped with an eighth valve. First, open the fourth valve to send the reaction liquid from the first-stage fixed-bed reactor, which has undergone circulation, into the second receiver. At the same time, add medium- and low-chain fatty acids into the first receiver. Then, open the fifth valve to pump the medium- and low-chain fatty acids from the first receiver into the second receiver. Then, close the fourth and fifth valves and open the sixth valve to pump the material from the second receiver into the second-stage fixed-bed reactor. After the second-stage fixed-bed reactor is full of material, close the sixth valve and open the seventh and eighth valves to circulate the material in the third container and the second-stage fixed-bed reactor, where a circulation reaction occurs.

[0020] Furthermore, in step S3, the medium- and low-chain fatty acids and the remaining free sterols undergo esterification in a cyclic manner as follows: The upper end of the second-stage fixed-bed reactor is connected to the upper end of a sixth container through a third passage, the lower end of the second-stage fixed-bed reactor is connected to the right end of the sixth container through a fourth passage, and the left end of the sixth container is connected to the first-stage fixed-bed reactor through a fifth passage. The third passage is equipped with a fourteenth valve, and the fifth passage is equipped with a fifteenth valve; First, open the fifteenth valve to send the reaction liquid that has undergone the circulating reaction in the first-stage fixed-bed reactor into the sixth container. At the same time, add medium- and low-carbon chain fatty acids into the sixth container. Then, close the fifteenth valve and open the fourteenth valve to pump the material in the sixth container into the second-stage fixed-bed reactor. The material is then circulated between the sixth container and the second-stage fixed-bed reactor, and a circulating reaction occurs.

[0021] Furthermore, the lipase is an alumina-immobilized lipase.

[0022] Furthermore, the first, second, and third stage fixed-bed reactors are all placed in a circulating water bath at 40-60℃.

[0023] Furthermore, the alumina-immobilized lipase is made by immobilizing lipase onto an alumina carrier; or, the alumina-immobilized lipase is a mixture of lipase and alumina.

[0024] Furthermore, when the alumina-immobilized lipase is a mixture of lipase and alumina, the mixing ratio of lipase to alumina is 1:5 to 1:10.

[0025] Furthermore, in step S, the reaction is considered complete when the acid value in the first-stage fixed-bed reactor is detected to be <0.2 mg / ml.

[0026] Furthermore, in step S, the reaction is considered complete when the free sterol content in the second-stage fixed-bed reactor is detected to be <0.2%.

[0027] Furthermore, medium- and low-carbon chain fatty acids are fatty acids with a carbon chain length of 8-18.

[0028] The method for separating natural vitamin E impurities according to the present invention has the following advantages: ① In the first-stage fixed-bed reactor, the polyunsaturated free fatty acids and free sterols in the feed liquid undergo esterification under the catalysis of lipase to generate polyunsaturated fatty acid esters. In the second-stage fixed-bed reactor, the medium- and low-carbon chain fatty acids and the remaining free sterols undergo esterification in a cyclic manner to generate medium- and low-carbon chain fatty acid esters. That is, both esterification reactions are carried out in a cyclic manner. Therefore, the method for separating impurities in natural vitamin E provided by this invention can fully remove free sterols and free fatty acids from crude natural vitamin E.

[0029] ② By adding lipase and medium- and low-chain fatty acids, free fatty acids and free sterols in crude natural vitamin E can be removed in one step, eliminating the need for cooling crystallization and filtration to remove sterols. This method is simpler and faster. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a three-stage fixed-bed reactor according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the structure of a three-stage fixed-bed reactor according to a variation of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0033] This invention provides a method for separating impurities from natural vitamin E, comprising the following steps: S1. Lipase is filled into the first and second stage fixed bed reactors 3 and 7 of the interconnected three-stage fixed bed reactor, and a mixture of activated carbon and kaolin is filled into the third stage fixed bed reactor 8. S2. The crude natural vitamin E raw material liquid is fed into the first-stage fixed-bed reactor 3, so that the polyunsaturated free fatty acids and free sterols in the raw material liquid undergo esterification under the catalysis of lipase. After the recycling reaction, the reaction liquid is sent into the second-stage fixed-bed reactor 7. S3. At the same time, medium and low carbon chain fatty acids are added to the second-stage fixed-bed reactor 7 to allow them to undergo esterification with the remaining free sterols. After the cyclic reaction, the reaction solution is sent to the third-stage fixed-bed reactor 8. S4. The activated carbon and clay mixture in the third-stage fixed-bed reactor 8 adsorbs benzo[a]pyrene and colloidal impurities to obtain a mixture containing medium and low carbon chain fatty acids, mixed fatty acid esters and natural vitamin E. S5. The mixture obtained in step S4 is sent to a tertiary molecular distillation process to obtain a natural vitamin E product.

[0034] The method for separating natural vitamin E impurities according to the present invention has the following advantages: ① In the first-stage fixed-bed reactor, the polyunsaturated free fatty acids and free sterols in the feed liquid undergo esterification under the catalysis of lipase to generate polyunsaturated fatty acid esters. In the second-stage fixed-bed reactor, the medium- and low-carbon chain fatty acids and the remaining free sterols undergo esterification in a cyclic manner to generate medium- and low-carbon chain fatty acid esters. That is, both esterification reactions are carried out in a cyclic manner. Therefore, the method for separating impurities in natural vitamin E provided by this invention can fully remove free sterols and free fatty acids from crude natural vitamin E.

[0035] ② By adding lipase and medium- and low-chain fatty acids, free fatty acids and free sterols in crude natural vitamin E can be removed in one step, eliminating the need for cooling crystallization and filtration to remove sterols. This method is simpler and faster.

[0036] In step S2, the esterification reaction of polyunsaturated free fatty acids and free sterols can occur in any way, but it is preferable to cyclically esterify them in the following manner: The upper end of the first-stage fixed-bed reactor 3 is connected to the first container 1 through the first pipeline, and the second container 2 is connected to the second pipeline through the second pipeline. The second container 2 is also connected to the lower end of the first-stage fixed-bed reactor 3 through the third pipeline. A first valve 11 is provided on the side of the first pipeline near the first container 1, a second valve 12 is provided on the second pipeline, and a third valve 13 is provided on the third pipeline; First, crude natural vitamin E is added to the first container 1. Then, the first valve 11 is opened to pump the crude natural vitamin E into the first-stage fixed-bed reactor 3. After the first-stage fixed-bed reactor 3 is filled with material, the first valve 11 is closed and the second valve 12 and the third valve 13 are opened to allow the material to circulate in the second container 2 and the first-stage fixed-bed reactor 3 and to undergo a circulating reaction.

[0037] In step S2, the polyunsaturated free fatty acids and free sterols can preferably undergo esterification in a cyclic manner as follows: The upper end of the first-stage fixed-bed reactor 3 is connected to the upper end of a fifth container 5a through a first passage, and the lower end of the first-stage fixed-bed reactor 3 is connected to the side end of the fifth container 5a through a second passage. The first passage is equipped with a thirteenth valve 23; First, crude natural vitamin E is added to the fifth container 5a. Then, the thirteenth valve 23 is opened to pump the crude natural vitamin E into the first-stage fixed-bed reactor 3, and the material circulates within the fifth container 5a and the first-stage fixed-bed reactor 3, where a circulating reaction occurs.

[0038] In step S3, the esterification reaction of medium- and low-chain fatty acids and the remaining free sterols is not limited in any way, but it can preferably be carried out through the following cyclic esterification reaction: The upper end of the second-stage fixed-bed reactor 7 is connected to the second receiver 5 through the fourth pipe. Next to the fourth pipe, the third container 6 is also connected to the third container 6 through the fifth pipe. The third container 6 is also connected to the lower end of the second-stage fixed-bed reactor 7 through the sixth pipe. The first receiver 4 is connected to the second receiver 5 through the seventh pipe. The second receiver 5 is also connected to the lower end of the first-stage fixed-bed reactor 3 through the eighth pipe. The eighth pipeline is equipped with a fourth valve 14, the seventh pipeline is equipped with a fifth valve 15, the fourth pipeline is equipped with a sixth valve 16 near the second receiver 5, the fifth pipeline is equipped with a seventh valve 17, and the sixth pipeline is equipped with an eighth valve 18. First, open the fourth valve 14 to send the reaction liquid from the first-stage fixed-bed reactor 3, which has undergone circulation, into the second receiver 5. At the same time, add medium- and low-carbon chain fatty acids into the first receiver 4. Then, open the fifth valve 15 to pump the medium- and low-carbon chain fatty acids from the first receiver 4 into the second receiver 5. Then, close the fourth valve 14 and the fifth valve 15, and open the sixth valve 16 to pump the material from the second receiver 5 into the second-stage fixed-bed reactor 7. After the second-stage fixed-bed reactor 7 is full of material, close the sixth valve 16 and open the seventh valve 17 and the eighth valve 18 to circulate the material in the third container 6 and the second-stage fixed-bed reactor 7, and a circulation reaction occurs.

[0039] In step S3, the medium- and low-chain fatty acids and the remaining free sterols can preferably undergo esterification via a cyclic process: The upper end of the second-stage fixed-bed reactor 7 is connected to the upper end of a sixth container 6a through a third passage, the lower end of the second-stage fixed-bed reactor 7 is connected to the right end of the sixth container 6a through a fourth passage, and the left end of the sixth container 6a is connected to the first-stage fixed-bed reactor 3 through a fifth passage. The three passages are equipped with the fourteenth valve 24, and the five passages are equipped with the fifteenth valve 25; First, open the fifteenth valve 25 to send the reaction liquid from the first-stage fixed-bed reactor 3, which has undergone a circulating reaction, into the sixth container 6a. At the same time, add medium- and low-carbon chain fatty acids into the sixth container 6a. Then, close the fifteenth valve 25 and open the fourteenth valve 24 to pump the material in the sixth container 6a into the second-stage fixed-bed reactor 7, and circulate the material between the sixth container 6a and the second-stage fixed-bed reactor 7, where a circulating reaction occurs.

[0040] The lipase is an alumina-immobilized lipase. Alumina, acting as an enzyme carrier, adsorbs the water generated during esterification, increasing the conversion rate and allowing for more complete removal of free sterols and free fatty acids from crude natural vitamin E.

[0041] The first, second, and third stage fixed-bed reactors are all placed in a circulating water bath at 40-60℃. Since the lipase is an alumina-immobilized lipase, it catalyzes the esterification reaction. The alumina absorbs the water generated during the esterification reaction to improve the conversion rate. Therefore, the method for separating impurities in natural vitamin E provided by this invention can be carried out under mild reaction conditions of 40-60℃, ensuring that vitamin E does not undergo oxidative decomposition at high temperatures, thereby improving the yield of natural vitamin E.

[0042] Alumina-immobilized lipase exists in two forms: either it can be made by immobilizing lipase onto an alumina carrier, or it can be a mixture of lipase and alumina.

[0043] The method for immobilizing lipases onto an alumina support may include the following steps: ① Dissolve the lipase in a pH 8.0 disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution to prepare an enzyme solution with a concentration of 10 mg / ml; ② Add 200g of ordered mesoporous alumina to 200mL of enzyme solution, sonicate for 15-25min, and then place in a shaker at 40℃ for 22-26h. ③ Discard the supernatant, wash the solid particles 2-3 times with 0.05mol / L citrate-phosphate buffer at pH 6.0, and dehydrate them under vacuum at 60℃ for 4h to obtain alumina-immobilized lipase.

[0044] When the immobilized lipase is a mixture of lipase and alumina, the mixing ratio of lipase to alumina is 1:5 to 1:10.

[0045] Because alumina is hygroscopic, water generated during the esterification reaction accumulates continuously. The surface of the alumina support becomes saturated with water, leading to a decrease in catalyst activity or even failure. The alumina support can be regenerated by vacuum dehydration at 60°C for 2 hours.

[0046] In step S2, whether the polyunsaturated free fatty acids and free sterols have reacted completely can be determined by the following method: when the acid value in the first-stage fixed-bed reactor is detected to be <0.2 mg / ml, the reaction is considered complete.

[0047] In step S3, whether the remaining free sterols and medium- and low-chain fatty acids have reacted completely can be determined by the following method: when the sterol content in the second-stage fixed-bed reactor is detected to be <0.2%, the reaction is considered complete.

[0048] Medium- and low-chain fatty acids are those with a carbon chain length of 8-18. The carbon chain length should not be too long, otherwise it will be difficult for the fatty acids to undergo a rapid and complete esterification reaction with free sterols; the carbon chain length should also not be too short, as the resulting fatty acid esters are unstable and will undergo hydrolysis, leading to an inability to effectively remove residual free sterols from crude vitamin E. A carbon chain length of 8-18 is ideal, as this allows the medium- and low-chain fatty acids to undergo a rapid and complete esterification reaction with free sterols, thus removing the remaining free sterols.

[0049] Furthermore, the molar ratio of free fatty acids to free sterols in the raw material solution of crude natural vitamin E is 1:1-5.

[0050] Furthermore, the molar ratio of medium- and low-chain fatty acids to the initial free sterols is 1-5:1.

[0051] The following five examples / one variation and four comparative examples are provided to illustrate in detail the method for separating natural vitamin E impurities provided by the present invention.

[0052] Example 1 like Figure 1 As shown, in a three-stage fixed-bed reactor (each stage id×L=5cm×20cm), the first two stages are filled with alumina-immobilized lipase, with a filling height of 15cm. The last stage is filled with a mixture of activated carbon and kaolin in a 1:1 ratio, with a filling height of 10cm. A circulating water bath maintains a constant temperature of 45℃ for all stages of the apparatus.

[0053] Crude soybean natural vitamin E (acid value 2.91 mg / ml, sterols 15.23%, VE content 48.45%, specific rotation +16°, benzo[a]pyrene 1524 ppm) was added to the first container 1. Then, the first valve 11 was opened, and the material was pumped into the first-stage fixed-bed reactor 3 at a flow rate of 10.0 mL / min. After the first-stage fixed-bed reactor 3 was filled with material, the first valve 11 was closed, and the second valve 12 and the third valve 13 were opened to allow the material to circulate in the second container 2 and the first-stage fixed-bed reactor 3 and to undergo a circulating reaction. After the reaction was carried out for about 4 hours, the acid value of the second container 2 was detected to be <0.2 mg / ml. Then, the second valve 12 and the third valve 13 were closed, and the fourth valve 14 was opened to transfer the reactants in the first-stage fixed-bed reactor 3 to the second receiver 5. Simultaneously, lauric acid is added to the first receiver 4, wherein the molar mass of lauric acid is 5 times the sterol content in the second receiver 5. After stirring evenly, the fifth valve 15 is opened, and the lauric acid in the first receiver 4 is pumped into the second receiver 5 at a flow rate of 10.0 mL / min. Then, the fourth valve 14 and the fifth valve 15 are closed, and the sixth valve 16 and the ninth valve 19 are opened, so that the material in the second receiver 5 is pumped into the second-stage fixed-bed reactor 7. After the second-stage fixed-bed reactor 7 is filled with material, the sixth valve 16 is closed, and the seventh valve 17 and the eighth valve 18 are opened, so that the material circulates in the third container 6 and the second-stage fixed-bed reactor 7 and a circulation reaction occurs. After the reaction is about 2 hours later, the sterol content in the third container 6 is detected to be <0.2%. Then, the seventh valve 17 and the eighth valve 18 are closed, and the tenth valve 20 and the eleventh valve 21 are opened, so that the reactants in the second-stage fixed-bed reactor 7 are transferred to the third-stage fixed-bed reactor 8 to remove colloids and benzo[a]pyrene impurities. Then close the ninth valve 19, the tenth valve 20, and the eleventh valve 21, and open the twelfth valve 22 to transfer the reactants in the third-stage fixed-bed reactor 8 into the fourth container 9. After molecular distillation to remove the light fraction (150-180℃ distillation range) of low-carbon chain fatty acids and the heavy fraction (>210℃ residue) of mixed fatty acid esters, the material in the fourth container 9 is obtained as a purified natural vitamin E with an acid value of 0.21 mg KOH / g, a sterol content of 0.47%, and a vitamin E yield of 95.98%.

[0054] Example 2 Based on Example 1, the raw materials were replaced with crude corn natural vitamin E (acid value 3.51 mg / ml, sterols 17.16%, VE content 26.53%, specific rotation +10°, benzo[a]pyrene 1365 ppm), lauric acid was replaced with oleic acid, and the water bath temperature was changed to 55°C. Example 3 Based on Example 1, the raw materials were changed to soybean natural vitamin E (acid value 2.57 mg / ml, sterol 2.58%, VE content 89.34%, specific rotation +29°, benzo[a]pyrene 243 ppm), and lauric acid was changed to a mixture of oleic acid and linoleic acid in a molar ratio of 1:1.

[0055] Example 4 Based on Example 1, the alumina-loaded lipase was replaced with a mixture of alumina and lipase in the same proportion, and the water bath temperature was changed to 40°C.

[0056] Example 5 Example 1: Feeding was performed 20 times, and the natural vitamin E index was tested on the 20th feed.

[0057] Variation Example 1 like Figure 2 As shown, in a three-stage fixed-bed reactor (each stage id×L=5cm×20cm), the first two stages are filled with alumina-immobilized lipase, with a filling height of 15cm. The last stage is filled with a mixture of activated carbon and kaolin in a 1:1 ratio, with a filling height of 10cm. A circulating water bath maintains a constant temperature of 45℃ for all stages of the apparatus.

[0058] First, crude soybean natural vitamin E (acid value 2.91 mg / ml, sterols 15.23%, VE content 48.45%, specific rotation +16°, benzo[a]pyrene 1524 ppm) was added to the fifth container 5a. Then, the thirteenth valve 23 was opened, and the crude natural vitamin E was pumped into the first-stage fixed-bed reactor 3 at a flow rate of 10.0 mL / min. The material was circulated between the fifth container 5a and the first-stage fixed-bed reactor 3, and a circulating reaction occurred. After about 4 hours of reaction, the acid value of the fifth container 5a was measured to be <0.2 mg / ml. Then, the thirteenth valve 23 was closed, and the fifteenth valve 25 was opened. The reaction solution that had undergone the circulating reaction in the first-stage fixed-bed reactor 3 was sent to the sixth container 6a. At the same time, the solution was added to the sixth container 6a. Add medium- and low-carbon chain fatty acids, then close the fifteenth valve 25 and open the fourteenth valve 24 to pump the material in the sixth container 6a into the second-stage fixed-bed reactor 7. The material circulates between the sixth container 6a and the second-stage fixed-bed reactor 7, undergoing a circulating reaction. After approximately 2 hours of reaction, if the sterol content in the sixth container 6a is detected to be <0.2%, close the fourteenth valve 24 and open the sixteenth valve 26 to transfer the reactants in the second-stage fixed-bed reactor 7 into the seventh container 7a. Then close the sixteenth valve 26 and open the seventeenth valve 27 to pump the material in the seventh container 7a into the third-stage fixed-bed reactor 8. The material circulates between the seventh container 7a and the third-stage fixed-bed reactor 8 to remove gum and benzo[a]pyrene impurities. Then close the seventeenth valve 27 and open the eighteenth valve 28 to transfer the reactants in the third-stage fixed-bed reactor 8 to the eighth container 8a. The material in the eighth container 8a is subjected to molecular distillation to remove the light fraction (150-180℃ distillation range) of low-carbon chain fatty acids and the heavy fraction (>210℃ residue) of mixed fatty acid esters, resulting in natural vitamin E with an acid value of 0.24 mgKOH / g, sterol content of 0.66%, and VE yield of 95.86% after purification.

[0059] Comparative Example 1 Lauric acid was added directly to container ① based on Example 1.

[0060] Comparative Example 2 Based on Example 1, lauric acid was replaced with docosahexaenoic acid (DHA).

[0061] Comparative Example 3 Based on Example 1, a non-circulating operation with continuous feeding is adopted.

[0062] Comparative Example 4 Based on Example 1, only aluminum oxide was used instead of lipase, and the esterification reaction of free fatty acids and free sterols was catalyzed at a suitable temperature (150-180℃).

[0063] The purified natural vitamin E indicators obtained from the various embodiments and comparative examples are shown in Tables 1 and 2 below.

[0064]

[0065] Table 1

[0066] Table 2 The following conclusions can be drawn from Tables 1 and 2: ① The purified natural vitamin E obtained from the five examples and one variation has good properties. The acid value of the purified natural vitamin E is below 0.5 mg KOH / g, the sterol content is below 0.7%, the benzo[a]pyrene content is less than 2 ppm, the specific rotation is above 25°, and the VE yield is above 94%. This confirms that the method for separating impurities from natural vitamin E provided by the present invention can effectively remove free sterols and free fatty acids from crude natural vitamin E.

[0067] ② For Comparative Example 1, since it is based on Example 1, lauric acid is directly added to container ①. In the first-stage fixed-bed reactor, lauric acid with a lower number of carbon atoms will undergo a cyclic esterification reaction with free sterols, while free fatty acids with a higher number of carbon atoms are difficult to undergo a cyclic esterification reaction with free sterols. Therefore, the free fatty acids in the crude natural vitamin E are difficult to remove. The acid value of the purified natural vitamin E obtained in Comparative Example 1 is 2.74 mg / ml, which is much higher than 0.21 mg / ml in Example 1. This also confirms the above inference.

[0068] ③ For Comparative Example 2, since it is based on Example 1, lauric acid is replaced with docosahexaenoic acid (DHA). Docosahexaenoic acid (DHA) has a higher number of carbon atoms than lauric acid. Therefore, docosahexaenoic acid (DHA) is difficult to undergo cyclic esterification reaction with free sterols under the action of a catalyst. As a result, the free sterols in the crude natural vitamin E are difficult to remove. The free sterol removal rate of the purified natural vitamin E obtained in Comparative Example 2 is 89.76%, which is lower than the 96.89% in Example 1. This also confirms the above inference.

[0069] ④ For Comparative Example 3, since it adopts a non-circulating operation and continuous feeding based on Example 1, without performing a cyclic esterification reaction, free fatty acids and free sterols, as well as medium and low carbon chain fatty acids and free sterols, cannot undergo sufficient chemical reaction. As a result, the free fatty acids and free sterols in the crude natural vitamin E cannot be effectively removed. The free sterol removal rate of the purified natural vitamin E obtained in Comparative Example 3 is 68.79%, which is much lower than the 96.89% of Example 1; the acid value is 1.32 mg / ml, which is much higher than the 0.21 mg / ml of Example 1. This also confirms the above inference.

[0070] ⑤ For Comparative Example 4, since it was based on Example 1, it used only alumina instead of lipase, and catalyzed the esterification reaction of free fatty acids and free sterols at a suitable temperature (150-180℃). Because no lipase was added, the cyclic esterification reaction of free fatty acids and free sterols, and medium and low carbon chain fatty acids and free sterols, needs to be carried out at a higher temperature. Natural vitamin E is a heat-sensitive component, so it will undergo oxidative decomposition at high temperature. The VE yield of the purified natural vitamin E obtained in Comparative Example 4 was 50.34%, which is much lower than the 95.98% of Example 1, which also confirms the above inference.

[0071] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for separating impurities from natural vitamin E, characterized in that, Includes the following steps: S1. Lipase is filled into the first and second stage fixed bed reactors (3, 7) of the interconnected three-stage fixed bed reactors, and a mixture of activated carbon and kaolin is filled into the third stage fixed bed reactor (8). S2. The crude natural vitamin E raw material liquid is fed into the first-stage fixed-bed reactor (3), so that the polyunsaturated free fatty acids and free sterols in the raw material liquid undergo esterification under the catalysis of lipase. After the cyclic reaction, the reaction liquid is sent into the second-stage fixed-bed reactor (7). S3. At the same time, medium and low carbon chain fatty acids are added to the second-stage fixed-bed reactor (7) to allow them to undergo esterification with the remaining free sterols. After the cyclic reaction, the reaction solution is sent to the third-stage fixed-bed reactor (8). S4. The activated carbon and clay mixture in the third-stage fixed-bed reactor (8) adsorbs benzo[a]pyrene and colloidal impurities to obtain a mixture containing medium and low carbon chain fatty acids, mixed fatty acid esters and natural vitamin E. S5. The mixture obtained in step S4 is sent to a tertiary molecular distillation process to obtain a natural vitamin E product.

2. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, In step S2, polyunsaturated free fatty acids and free sterols undergo esterification in a cyclic manner as follows: The upper end of the first-stage fixed-bed reactor (3) is connected to a first container (1) through a first pipeline, and a second container (2) is connected to the first pipeline through a second pipeline. The second container (2) is also connected to the lower end of the first-stage fixed-bed reactor (3) through a third pipeline. A first valve (11) is provided on the side of the first pipeline near the first container (1), a second valve (12) is provided on the second pipeline, and a third valve (13) is provided on the third pipeline. First, crude natural vitamin E is added to the first container (1), and then the first valve (11) is opened to pump the crude natural vitamin E into the first-stage fixed-bed reactor (3). After the first-stage fixed-bed reactor (3) is filled with material, the first valve (11) is closed, and the second valve (12) and the third valve (13) are opened to allow the material to circulate in the second container (2) and the first-stage fixed-bed reactor (3) and to undergo a circulating reaction.

3. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, In step S2, polyunsaturated free fatty acids and free sterols undergo esterification in a cyclic manner as follows: The upper end of the first-stage fixed-bed reactor (3) is connected to the upper end of a fifth container (5a) through a first passage, and the lower end of the first-stage fixed-bed reactor (3) is connected to the side end of the fifth container (5a) through a second passage. The first passage is equipped with a thirteenth valve (23); First, crude natural vitamin E is added to the fifth container (5a), then the thirteenth valve (23) is opened to pump the crude natural vitamin E into the first-stage fixed-bed reactor (3), and the material circulates in the fifth container (5a) and the first-stage fixed-bed reactor (3) and a circulating reaction occurs.

4. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, In step S3, the medium- and low-chain fatty acids and the remaining free sterols undergo esterification in a cyclic manner as follows: The upper end of the second-stage fixed-bed reactor (7) is connected to the second receiver (5) through the fourth pipeline. Next to the fourth pipeline, a third container (6) is also connected through the fifth pipeline. The third container (6) is also connected to the lower end of the second-stage fixed-bed reactor (7) through the sixth pipeline. The first receiver (4) is connected to the second receiver (5) through the seventh pipeline. The second receiver (5) is also connected to the lower end of the first-stage fixed-bed reactor (3) through the eighth pipeline. The eighth pipeline is provided with a fourth valve (14), the seventh pipeline is provided with a fifth valve (15), the fourth pipeline is provided with a sixth valve (16) on the side near the second receiver (5), the fifth pipeline is provided with a seventh valve (17), and the sixth pipeline is provided with an eighth valve (18). First, open the fourth valve (14) to send the reaction liquid that has undergone the circulating reaction in the first-stage fixed-bed reactor (3) into the second receiver (5). At the same time, add medium and low carbon chain fatty acids into the first receiver (4). Then open the fifth valve (15) to pump the medium and low carbon chain fatty acids in the first receiver (4) into the second receiver (5). Then close the fourth valve (14) and the fifth valve (15), and open the sixth valve (16) to pump the material in the second receiver (5) into the second-stage fixed-bed reactor (7). After the second-stage fixed-bed reactor (7) is filled with material, close the sixth valve (16) and open the seventh valve (17) and the eighth valve (18) to make the material circulate in the third container (6) and the second-stage fixed-bed reactor (7) and undergo a circulating reaction.

5. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, In step S3, the medium- and low-chain fatty acids and the remaining free sterols undergo esterification in a cyclic manner as follows: The upper end of the second-stage fixed-bed reactor (7) is connected to the upper end of a sixth container (6a) through a third passage, the lower end of the second-stage fixed-bed reactor (7) is connected to the right end of the sixth container (6a) through a fourth passage, and the left end of the sixth container (6a) is connected to the first-stage fixed-bed reactor (3) through a fifth passage. The third passage is provided with a fourteenth valve (24), and the fifth passage is provided with a fifteenth valve (25). First, open the fifteenth valve (25) to send the reaction liquid that has undergone the circulating reaction in the first-stage fixed-bed reactor (3) into the sixth container (6a). At the same time, add medium and low carbon chain fatty acids into the sixth container (6a). Then close the fifteenth valve (25), open the fourteenth valve (24), pump the material in the sixth container (6a) into the second-stage fixed-bed reactor (7), and make the material circulate in the sixth container (6a) and the second-stage fixed-bed reactor (7) and a circulating reaction occurs.

6. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, The lipase is an alumina-immobilized lipase.

7. The method for separating natural vitamin E impurities as described in claim 6, characterized in that, The first, second, and third stage fixed-bed reactors are all placed in a circulating water bath at 40-60℃.

8. The method for separating natural vitamin E impurities as described in claim 6, characterized in that, The alumina-immobilized lipase is made by immobilizing lipase onto an alumina carrier; or, the alumina-immobilized lipase is a mixture of lipase and alumina.

9. The method for separating natural vitamin E impurities as described in claim 8, characterized in that, When the alumina-immobilized lipase is a mixture of lipase and alumina, the mixing ratio of lipase to alumina is 1:5 to 1:

10.

10. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, In step S2, the reaction is considered complete when the acid value in the first-stage fixed-bed reactor is detected to be <0.2 mg / ml.

11. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, In step S3, the reaction is considered complete when the free sterol content in the second-stage fixed-bed reactor is detected to be <0.2%.

12. The method for separating natural vitamin E impurities as described in claim 1, characterized in that, The medium- and low-carbon chain fatty acids are fatty acids with a carbon chain length of 8-18.

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