A method for purifying natural vitamin E

Abstract

The application provides a natural vitamin E purification method. The purification method comprises the following steps: S1, dissolving natural vitamin E in anhydrous ethanol to obtain a vitamin E solution; S2, adding an antioxidant to the vitamin E solution, and then slowly adding a potassium hydroxide solution to perform a saponification reaction to obtain a mixed solution; S3, performing acid neutralization, salt water washing, liquid cyclone separation and dehydration on the mixed solution to obtain crude vitamin E oil; and S4, performing falling film evaporation and short path molecular distillation on the crude vitamin E oil to obtain high-purity natural vitamin E. Through process optimization of a traditional purification process, the process of low-temperature saponification combined with salt water washing and molecular distillation after thin film evaporation is adopted, no residual plasticizer is detected in the purified vitamin E, the content of total tocopherol is higher than 95%, and the proportion of d-alpha tocopherol with high activity in the total tocopherol is more than 50%.

Description

Technical Field

[0001] This invention relates to the field of separation and purification technology, specifically a method for purifying natural vitamin E. Background Technology

[0002] Vitamin E (VE), typically referring to a mixture of four tocopherols (α, β, γ, and δ) and four tocotrienols, is a fat-soluble vitamin with significant antioxidant activity and physiological health benefits. It is widely used in food, pharmaceuticals, and cosmetics, leading to a continuous increase in market demand for natural vitamin E. However, during vitamin E production, especially in the extraction and concentration from vegetable oil refining byproducts, it is highly susceptible to contamination by phthalate compounds. Phthalate compounds are widely used as plasticizers in industrial production, and due to their potential carcinogenic, teratogenic, and endocrine-disrupting toxicity, they are subject to strict control.

[0003] To reduce the plasticizer content in natural vitamin E, existing purification technologies are mainly divided into two categories: physical adsorption and chemical treatment. Physical adsorption primarily uses porous materials such as activated carbon, bentonite, and eucalyptus oil for physical adsorption. However, during the physical adsorption of natural vitamin E, because both plasticizers and vitamin E are fat-soluble, weakly polar organic compounds with similar physicochemical properties, conventional adsorbents struggle to selectively identify and separate them. This results in the adsorption of vitamin E along with plasticizers, leading to a significant decrease in yield. Furthermore, traditional physical adsorption is easily affected by the batch of raw materials, temperature, and concentration, making it difficult to consistently reduce plasticizer levels below safe standards. Therefore, currently used purification processes mainly focus on chemical treatment methods. For example, Chinese patent CN103588744B discloses a method for removing plasticizers from natural vitamin E, which removes plasticizers from natural vitamin E through a saponification-acid washing-water washing-distillation process. However, this method uses strong alkali saponification treatment at 60~100℃ for 0.5~3 hours, which carries the risk of side reactions such as ester bond hydrolysis and benzodihydropyran ring opening, and also leads to a darker color and off-odor of vitamin E. Therefore, the existing chemical treatment methods need further optimization to obtain a purification process with high yield, high vitamin E activity, and good quality. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for purifying natural vitamin E, which solves the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a method for purifying natural vitamin E is provided, comprising the following steps: S1. Dissolve natural vitamin E in anhydrous ethanol to obtain a vitamin E solution; S2. Add an antioxidant to the vitamin E solution, and then slowly add potassium hydroxide solution to carry out a saponification reaction to obtain a mixed solution; S3. The mixed solution is neutralized with acid, washed with brine, separated by hydrocyclone, and dehydrated to obtain crude vitamin E oil; S4. The crude vitamin E oil is subjected to falling film evaporation and short-path molecular distillation to obtain high-purity natural vitamin E.

[0006] This invention involves acid neutralization followed by brine washing to reduce the solubility of vitamin E in water, allowing for complete separation of the lower aqueous phase and obtaining crude vitamin E oil. Before short-path molecular distillation, the crude vitamin E oil undergoes falling film evaporation to efficiently remove free fatty acids, sterols, pigments, and odor substances. Combined with short-path molecular distillation, this achieves efficient separation of vitamin E at a relatively lower temperature, resulting in a higher purity of the distilled light phase.

[0007] The dissolution of natural vitamin E must be carried out under a nitrogen-protected atmosphere at 50-60°C. Preferably, in step S1, the volume ratio of natural vitamin E to anhydrous ethanol is 1:3-4.

[0008] Preferably, in step S2, the antioxidant is selected from L-ascorbic acid, and the amount of L-ascorbic acid added is 0.5-1% of the natural vitamin E. Adding the antioxidant before the saponification reaction protects the process from excessive saponification.

[0009] Preferably, in step S2, the concentration of potassium hydroxide is 30%; The saponification reaction is carried out under the following conditions: at 60-70°C, the potassium hydroxide solution is slowly added dropwise to the reaction system over 1-1.5 hours while stirring simultaneously until the pH reaches 8.5-9.5 and is maintained for 30 minutes to complete the saponification reaction.

[0010] During the saponification reaction, a 30% potassium hydroxide solution is the optimal saponifying agent, as it produces a more soluble saponifying agent that is easier to separate later. A low-temperature saponification process should be adopted, and the potassium hydroxide should be added slowly with simultaneous stirring. After the pH reaches 8.5-9.5, the saponification time should not exceed 30 minutes to prevent over-saponification.

[0011] Preferably, in step S3, the acid neutralization conditions are as follows: under stirring, at 40~50°C, dilute hydrochloric acid is added dropwise to the mixed solution until the pH reaches 6.0~6.5.

[0012] In the process of acid neutralization, this invention needs to avoid the use of sulfuric acid to prevent inorganic salt crystallization. This application chooses dilute hydrochloric acid to neutralize to a weak acidity, which makes the acid neutralization conditions milder.

[0013] Preferably, in step S3, the conditions for washing with brine are as follows: at 50~60℃, a 2% sodium chloride solution is added to the mixed solution, stirred for 10~15 minutes, allowed to stand and separated, and repeated 2~3 times.

[0014] Since the existing washing methods mainly use hot water, not only will a large amount of wastewater be generated, but vitamin E is also easily emulsified and lost. Washing with salt water can reduce the solubility of vitamin E in water, increase the yield of vitamin E, and significantly reduce the number of washing cycles.

[0015] Preferably, in step S3, the feed pressure for the hydrocyclone separator is 0.3~0.5MPa and the temperature is 45~50℃.

[0016] Preferably, in step S3, the dehydration temperature is 80~90℃.

[0017] Preferably, in step S4, the temperature of the falling film evaporation is 130~150℃, the vacuum degree is ≤10Pa, and the time is 10~15s.

[0018] In existing technologies, the vitamin E oil layer contains trace amounts of water and solvents before molecular distillation, which increases the initial reaction time and the thermal explosion time of vitamin E. Therefore, in order to reduce the residence time of vitamin E at high temperatures, a falling film thin-film evaporation process is added before molecular distillation to gently and efficiently remove trace amounts of high-boiling-point impurities and pigments, thereby improving the purity of the product.

[0019] Preferably, in step S4, the short-range molecular distillation includes a single-stage distillation and a two-stage distillation; The temperature of the first distillation stage is 160~170℃; The temperature of the second-stage distillation is 170~180℃.

[0020] This invention provides a method for purifying natural vitamin E. It has the following beneficial effects: (1) The method for purifying natural vitamin E provided in this solution optimizes the traditional purification process by using a combination of low-temperature saponification, brine washing, and molecular distillation after thin-film evaporation. This method can efficiently and thoroughly remove plasticizers from natural vitamin E while maximizing the protection of the chemical structural stability of highly bioactive d-α-tocopherol in vitamin E during the removal process. At the same time, it significantly reduces the amount of high-salt organic wastewater generated.

[0021] (2) The method provided in this scheme is a purification method for natural vitamin E. No residual plasticizers were detected in the purified vitamin E, and the total tocopherol content was higher than 95%, of which highly active d-α tocopherol accounted for more than 50% of the total tocopherol. Detailed Implementation

[0022] 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, and 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.

[0023] The purified crude natural vitamin E in the various embodiments and comparative examples of this invention is a natural vitamin E concentrate obtained by preliminary esterification and freeze crystallization of soybean oil deodorization effluent. Its total tocopherol content is 55%, and d-α tocopherol accounts for 42% of the total tocopherol. The crude natural vitamin E contains 2.1 mg / kg of dibutyl phthalate.

[0024] Example 1 Step 1: Under nitrogen protection, place 1000g of crude natural vitamin E in a 2000L reactor equipped with a stirrer and jacket, add 3000L of anhydrous ethanol, and stir at 55℃ until completely dissolved to obtain a vitamin E solution. Step 2: Add 8g of L-ascorbic acid to the vitamin E solution, and at a constant temperature of 65℃, start the metering pump to add 450L of 30% potassium hydroxide ethanol solution dropwise into the reaction system uniformly and slowly over 1.2h while maintaining vigorous stirring. The pH of the system is 9.2 after the addition is completed by online pH monitoring. Continue stirring for 30min to obtain a mixed solution. Step 3: Cool the mixed solution to 45℃, slowly add 10% dilute hydrochloric acid aqueous solution with stirring, and precisely adjust the pH of the system to 6.3. Then add 1000L of 2% sodium chloride aqueous solution preheated to 55℃, stir for 12min, let it stand and separate into layers, and then discharge the lower aqueous phase. Repeat the brine washing twice and collect the upper oil phase. Pump the washed upper oil phase into a hydrocyclone separator, control the feed pressure to 0.4MPa and the material temperature to 48℃. The separated oil phase enters a vacuum dehydration tank and is dehydrated for 1.5h at 85℃ and -0.096MPa to obtain crude vitamin E oil. Step 4: Preheat the crude vitamin E oil to 95°C and send it into a falling film evaporator. Control the temperature of the heating surface of the evaporator at 140°C and the system vacuum at 8Pa. After 12 seconds, collect the distillate. Finally, send the distillate into a short-path molecular distillation apparatus. First, distill it in a primary distillation apparatus at 165°C and 0.005Pa. Then, distill it again in a secondary distillation apparatus at 175°C and 0.003Pa. Collect the light phase fraction to obtain high-purity natural vitamin E.

[0025] Phthalate esters in high-purity natural vitamin E were tested according to the detection method in GB / T 21911-2008, and the result was not detected. The total tocopherol content was determined by HPLC to be 96.8%, with d-α-tocopherol accounting for 51.5%. Based on the total tocopherol content of the raw material, the tocopherol yield in the obtained product was 98.2%.

[0026] Comparative Example 1 The purification method of this comparative example is the same as that of Example 1, except that the saponification step in step 2 involves adding 450L of 30% potassium hydroxide ethanol solution at 85°C in one go.

[0027] Tests showed that no phthalates were detected in the purified natural vitamin E, but the total tocopherol content was 95.2%, and the proportion of d-α tocopherol was 44.7%.

[0028] Comparative Example 2 The purification method in this comparative example is the same as that in Example 1, except that the warm brine washing in step 3 is replaced with an equal amount of pure water at the same temperature.

[0029] Tests showed that no phthalates were detected in the purified natural vitamin E, but the total tocopherol content was 94.4%, and the proportion of d-α tocopherol was 49.7%.

[0030] Comparative Example 3 The purification method used in this comparative example is the same as that in Example 1, except that the falling film thin-film evaporation process in step 4 is omitted, and short-path molecular distillation is performed directly.

[0031] The natural vitamin E obtained was darker in color than the high-purity natural vitamin E obtained in Example 1.

[0032] Comparative Example 4 The purification method of this comparative example is the same as that of Example 1, except that the short-range molecular distillation in step 4 is carried out only at 175°C and 0.003 Pa.

[0033] Tests showed that no phthalates were detected in the purified natural vitamin E, but the total tocopherol content was 94.8%, and the proportion of d-α tocopherol was 48.9%.

[0034] As can be seen from the comparison between Example 1 and Comparative Example 1, the high temperature and local strong alkaline environment significantly damage the highly active d-α tocopherol structure, causing it to degrade into other homologues with lower activity. In Example 1, the slow drop-addition at a low temperature of 65°C can effectively avoid local overdose and thermal shock, and retain the d-α tocopherol structure to the greatest extent. As can be seen from the comparison between Example 1 and Comparative Example 2, since vitamin E has a certain solubility in water, using 2% warm salt water to reduce the solubility of vitamin E in the aqueous phase by utilizing the "salting-out effect" can reduce the dissolution loss during the washing process and thus increase the content of total tocopherols. According to the comparison between Example 1 and Comparative Example 3, falling film thin-film evaporation effectively removes pigments, some free fatty acids and heat-sensitive polymer impurities from the raw materials under mild and short-time conditions. If these impurities are directly introduced into the molecular distillation apparatus, they may be carbonized or the reaction may be intensified at higher temperatures, resulting in a darker product color, a decrease in purity, and an increase in the burden of molecular distillation. As can be seen from the comparison between Example 1 and Comparative Example 4, the two-stage gradient distillation reduces the residence time and total amount of material at high temperature. However, Comparative Example 4, which involves single distillation at 175°C, has a concentrated heat load and a longer duration, resulting in damage to vitamin E and affecting its purity and the proportion of active ingredients.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for purifying natural vitamin E, characterized in that: Includes the following steps: S1. Dissolve natural vitamin E in anhydrous ethanol to obtain a vitamin E solution; S2. Add an antioxidant to the vitamin E solution, and then slowly add potassium hydroxide solution to carry out a saponification reaction to obtain a mixed solution; S3. The mixed solution is neutralized with acid, washed with brine, separated by hydrocyclone, and dehydrated to obtain crude vitamin E oil; S4. The crude vitamin E oil is subjected to falling film evaporation and short-path molecular distillation to obtain high-purity natural vitamin E.

2. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S1, the volume ratio of the natural vitamin E to anhydrous ethanol is 1:3~4.

3. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S2, the antioxidant is selected from L-ascorbic acid, and the amount of L-ascorbic acid added is 0.5~1% of the natural vitamin E.

4. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S2, the concentration of potassium hydroxide is 30%; The saponification reaction is carried out under the following conditions: at 60-70°C, the potassium hydroxide solution is slowly added dropwise to the reaction system over 1-1.5 hours while stirring simultaneously until the pH reaches 8.5-9.5 and is maintained for 30 minutes to complete the saponification reaction.

5. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S3, the acid neutralization conditions are as follows: under stirring, dilute hydrochloric acid is added dropwise to the mixed solution at 40~50°C until the pH reaches 6.0~6.

5.

6. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S3, the conditions for washing with brine are as follows: at 50~60℃, a 2% sodium chloride solution is added to the mixed solution, stirred for 10~15 minutes, allowed to stand and separated, and repeated 2~3 times.

7. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S3, the feed pressure for the hydrocyclone separator is 0.3~0.5MPa and the temperature is 45~50℃.

8. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S3, the dehydration temperature is 80~90℃.

9. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S4, the temperature of the falling film evaporation is 130~150℃, the vacuum degree is ≤10Pa, and the time is 10~15s.

10. The method for purifying natural vitamin E according to claim 1, characterized in that: In step S4, the short-range molecular distillation includes a single-stage distillation and a two-stage distillation; The temperature of the first distillation stage is 160~170℃; The temperature of the second-stage distillation is 170~180℃.