A preparation method of DHA-EE and EPA-EE

Abstract

The present invention relates to a method for preparing DHA-EE and EPA-EE, which requires first subjecting fish oil and deionized water to a high-temperature and high-pressure heat exchange reaction, so that the fish oil can be fully hydrolyzed to generate EPA, DHA and other small-molecule fatty acids, etc., and the primary mixture obtained by hydrolysis is then reacted with a potassium hydroxide ethanol solution to obtain a saponified secondary mixture, and the secondary mixture can be catalyzed by a perfluorosulfonic acid resin to allow free EPA and DHA to fully react with anhydrous ethanol to obtain a tertiary mixture, and the tertiary mixture can be separated into high-purity EPA-EE and DHA-EE after secondary molecular distillation and tertiary molecular distillation. In the preparation method of the present invention, the water used for the hydrolysis reaction and the perfluorosulfonic acid resin used for the catalyst can be recycled, which greatly reduces the industrial cost of preparing DHA-EE and EPA-EE, and has high sustainability.

Description

Technical Field

[0001] The invention relates to the technical field of fish oil fatty acid derivative processing, and in particular to a method for preparing DHA-EE and EPA-EE. Background Art

[0002] Deep-sea fish oil is rich in omega-3 polyunsaturated fatty acids, the main components of which are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Naturally derived EPA and DHA exist mainly in the form of triglyceride molecules. These fatty acids are essential fatty acids that cannot be synthesized by the human body but are essential for maintaining life activities. EPA and DHA have multiple biological activities, including inhibiting platelet aggregation, anti-thrombosis, vasodilation, regulating blood lipids, increasing high-density lipoprotein cholesterol (HDL-C), reducing low-density lipoprotein cholesterol (LDL-C), and improving the liquid state of biological membranes. EPA and DHA also show good therapeutic effects in the treatment and prevention of cardiovascular and cerebrovascular diseases, diabetes, inflammation, colorectal ulcers, and tumor inhibition. For healthy people, supplementing these two fatty acids can also help maintain the normal function of the heart, lungs, blood vessels, and immune system.

[0003] The total content of EPA and DHA in natural marine fish oil is between 20% and 30%, and it also contains a large amount of saturated and monounsaturated fatty acids, which are inefficient ingredients or impurities. Not only do they have no therapeutic effect, but they also easily increase the body's calorie intake. At the same time, there are certain differences in the physiological functions of EPA and DHA. EPA helps lower blood lipids and has a relieving and regulating effect on cardiovascular diseases, three highs, and joint inflammation (commonly known as the "blood vessel scavenger"); while DHA helps promote nerve regeneration, improves cognitive function, and enhances memory and concentration (commonly known as "brain gold").

[0004] In recent years, Amarin, an internationally renowned chemical pharmaceutical giant, has conducted more than a decade of clinical research on the efficacy of EPA in lowering blood lipids, and found that high-purity EPA-EE (eicosapentaenoic acid ethyl ester, EPA ethyl ester) has good compatibility with statins. The combination of the two can significantly reduce the risk of cardiovascular events, and was eventually approved by the FDA for marketing under the trade name Vascepa. The evidence-based medicine REDUCE-IT (Eicosapentaenoic Acid Ethyl Reduction Cardiovascular Event Intervention Trial) study showed that high-purity EPA-EE has multiple beneficial mechanisms such as anti-oxidation, anti-inflammatory, anti-thrombotic and plaque stabilization, which can act on the entire process of atherosclerosis and bring benefits to the primary and secondary prevention of cardiovascular disease. The "Guidelines for Blood Lipid Management in China (2023)" also made a positive Class II a recommendation for the use of EPA-EE for residual risk management, which suggests that patients with atherosclerotic cardiovascular disease (ASCVD) and high-risk groups should consider giving high-dose EPA-EE (2g, twice a day) to reduce the risk of ASCVD after receiving moderate-dose statin therapy, if triglycerides (TG) are greater than 2.3mmol / L. However, it should be noted that if DHA and EPA are mixed, the anti-thrombotic effect of EPA may be weakened.

[0005] At present, most of the patents in the related field are mainly based on methods for preparing EPA and DHA at the same time, or separating EPA and DHA at the same time. However, since the structures and polarities of these two polyunsaturated fatty acids are similar, it is difficult to separate them efficiently and completely. For example, China Invention Patent Application Publication No. CN 102964249A discloses a method for obtaining EPA ethyl ester and DHA ethyl ester by separating fish oil that has been esterified by base catalysis and urea inclusion by supercritical technology. The method needs to first remove free fatty acids, small molecule fatty acid ethyl esters and glycerides in fish oil by supercritical extraction and supercritical countercurrent extraction respectively, and the enriched omega-3 ethyl ester mixture is separated by supercritical distillation. The method has many separation and purification steps and is difficult to industrialize. Chinese invention patent application publication number CN 107162910A discloses a method for preparing high-purity EPA-EE by molecular distillation, column chromatography, and silver ion complexation. First, ethyl esterified crude fish oil is distilled by a secondary molecular distillation method to obtain a mixture of EPA-EE and DHA-EE; secondly, the product obtained by molecular distillation in step 1) is purified by column chromatography to prepare a crude EPA-EE product, wherein the crude EPA-EE product contains very little DHA-EE or no DHA-EE; finally, the crude EPA-EE purified by column chromatography is purified by a silver nitrate complexation method, and impurities are removed by temperature difference to obtain an EPA-EE product. This method is simple to operate, but silver nitrate is relatively expensive, and the residual value of silver ions as heavy metals in the product is not detected. China Invention Patent Application Publication No. CN110257446A discloses a method for preparing high-purity EPA glyceride and DHA glyceride, wherein the fish oil is first subjected to enzymatic hydrolysis and then the fish oil fatty acids are separated and purified by a thin film evaporator and a distillation tower to obtain high-purity EPA and DHA; then EPA and glycerol are synthesized into EPA glyceride by lipase, and finally DHA and glycerol are synthesized into DHA glyceride by lipase. The enzyme used in this method cannot be recycled and the preparation cost is high. Therefore, it is necessary to develop an efficient, sustainable and suitable separation and purification technology for industrial production of EPA-EE and DHA-EE. Summary of the invention

[0006] The invention provides a method for preparing DHA-EE and EPA-EE.

[0007] To achieve the above object, the technical solution of the present invention is specifically implemented as follows:

[0008] A method for preparing DHA-EE and EPA-EE is carried out according to the following steps:

[0009] Step S1: Deionized water and fish oil are pumped into the upper and lower parts of the reaction tower at the same time, and high-pressure steam with a pressure of not less than 10 MPa is input into the upper, middle and lower parts of the reaction tower, and the temperature of the high-pressure steam is 120-260° C., and a primary mixture is obtained from the liquid outlet at the top of the reaction tower;

[0010] Step S2: mixing the primary mixture with potassium hydroxide ethanol solution in a mass ratio of 1-3:8-10, heating and reflux under helium protection for 1-3 hours, adding the hot solution to 1-3 times the volume of dilute sulfuric acid solution and shaking for 0.5-1.5 minutes, letting it stand for stratification and taking the upper phase to obtain a secondary mixture;

[0011] Step S3: mixing the secondary mixture with anhydrous ethanol at a volume ratio of 1:1 to 3, adding perfluorosulfonic acid resin, filtering out the perfluorosulfonic acid resin after ultrasonic microwave treatment for 30 to 60 minutes, and then rotary evaporating to recover ethanol to obtain a tertiary mixture;

[0012] Step S4: subjecting the tertiary mixture to primary molecular distillation, collecting the primary heavy phase for secondary molecular distillation, separating and collecting the secondary light phase and the secondary heavy phase, subjecting the secondary heavy phase to tertiary molecular distillation, and collecting the tertiary heavy phase; wherein the secondary light phase contains EPA-EE, and the tertiary heavy phase contains DHA-EE.

[0013] In the step S1, deionized water and fish oil are input into the reaction tower, and the high-pressure steam input from the upper and lower parts of the reaction tower can be injected into the deionized water and the fish oil to heat the deionized water and the fish oil respectively, so that the water temperature of the deionized water is not less than 95°C, and the temperature of the fish oil is not less than 215°C, thereby increasing the collision pressure between the deionized water and the fish oil so that the hot deionized water and the fish oil are in full contact. The high-pressure steam input into the middle part of the reaction tower can maintain the reaction temperature in the reaction tower. Due to the different specific gravities of the fish oil and the deionized water, when the fish oil and the deionized water are mixed, the fish oil moves upward and the deionized water moves downward, and heat exchange continuously occurs between the two. An emulsified state is formed under the action of pressure, so that the fish oil can be fully hydrolyzed to generate EPA, DHA, other small molecular fatty acids and glycerol, etc. As the water and fish oil in the reaction tower continue to increase, EPA, DHA and other small molecular fatty acids continue to move upward and are washed out from the liquid outlet at the top of the reaction tower, while the water dissolved with glycerol moves downward and flows out from the liquid outlet at the bottom of the tower.

[0014] It is worth mentioning that the liquid inlet and outlet of the reaction tower are connected to pipes, and a one-way valve is installed on the pipes to ensure that backflow does not occur.

[0015] As a preferred solution, in step S1, an ultrasonic generator is installed on the reaction tower, and the deionized water and fish oil are ultrasonically treated in the reaction tower, with an ultrasonic frequency of 100 to 120 kHz and a power of 650 W. Under the action of ultrasonic waves, the deionized water and fish oil will undergo cavitation and mechanical vibration effects, generating a large number of bubbles, which will rapidly expand and contract under the action of ultrasonic waves, forming shock waves and microjets, so that the deionized water and fish oil form particles that are fully mixed, thereby increasing the rate of heat exchange between the deionized water and the fish oil.

[0016] As a preferred solution, in step S1, the reaction pressure of the reaction tower is 10-20 MPa, the input flow rate of deionized water is 150-200 kg / h, and the input flow rate of fish oil is 100-150 kg / h. By controlling the input flow rates of deionized water and fish oil, it can be ensured that water and fish oil can fully exchange heat.

[0017] As a preferred solution, in step S1, the input flow rate of the high-pressure steam in the upper part is 100-150 kg / h, and the temperature is 120-180°C, the input flow rate of the high-pressure steam in the middle part is 80-100 kg / h, and the temperature is 200-260°C, and the input flow rate of the high-pressure steam in the lower part is 100-150 kg / h, and the temperature is 220-260°C. By controlling the input flow rate of the high-pressure steam, it can be ensured that the water and fish oil can be fully heated.

[0018] As a more detailed scheme, in step S1, the input pressure of the high-pressure steam in the upper part is 12-15 MPa, the input pressure of the high-pressure steam in the middle part is 10-12 MPa, and the input pressure of the high-pressure steam in the lower part is 12-15 MPa. By controlling the input pressure of the high-pressure steam, the collision pressure of the deionized water and the fish oil can be controlled.

[0019] As a more detailed scheme, in step S2, the mass ratio of potassium hydroxide to ethanol in the potassium hydroxide ethanol solution is 10-15:1000-1500; the concentration of the dilute sulfuric acid solution is 10%-20%.

[0020] In step S2, the primary mixture and the potassium hydroxide ethanol solution mixture can be placed in a condensation reflux reactor for heating and reflux. The protective gas can also be nitrogen or argon. Under the catalysis of potassium hydroxide, fatty acids such as EPA and DHA are saponified with ethanol. After the reaction is completed, it is acidified with a dilute sulfuric acid solution to obtain a secondary mixture with high EPA-EE and DHA-EE content.

[0021] As a more detailed solution, in step S3, the amount of perfluorosulfonic acid resin added is 1-5wt%. The perfluorosulfonic acid resin can be selected from any one of Nafion-H perfluorosulfonic acid resin, Nafion-501 perfluorosulfonic acid resin, Nafion-xr perfluorosulfonic acid resin, Nafion-425 perfluorosulfonic acid resin or Nafion-xr500 perfluorosulfonic acid resin, or a combination of at least two thereof.

[0022] As a more detailed solution, in step S3, the ultrasonic frequency is 60-80kHz, the power is 500-750W; the microwave power is 500-800W.

[0023] As a more detailed scheme, in step S4, the primary molecular distillation conditions are: pre-degassing temperature is 60°C, pre-degassing pressure is 80Pa, operating pressure is 0.1Pa, feed rate is 0.3L / min, distillation temperature is 100°C, and thin film distillation scraper speed is 250r / min.

[0024] As a more detailed scheme, in step S4, the secondary molecular distillation conditions are: distillation temperature 150° C., thin film distillation scraper speed 220 r / min.

[0025] As a more detailed scheme, in step S4, the three-stage molecular distillation conditions are: distillation temperature 180° C., thin film distillation scraper speed 200 r / min.

[0026] The beneficial effects of the present invention are:

[0027] (1) The preparation method of DHA-EE and EPA-EE of the present invention requires first subjecting fish oil and deionized water to a high-temperature and high-pressure heat exchange reaction so that the fish oil can be fully hydrolyzed to generate EPA, DHA and other small molecular fatty acids, etc., and the primary mixture obtained by hydrolysis is then reacted with a potassium hydroxide ethanol solution to obtain a saponified secondary mixture. Under the catalysis of perfluorosulfonic acid resin, the secondary mixture can allow free EPA and DHA to fully react with anhydrous ethanol to obtain a tertiary mixture with high EPA-EE and DHA-EE content. After the tertiary mixture is subjected to secondary molecular distillation and tertiary molecular distillation, high-purity EPA-EE and DHA-EE can be separated.

[0028] (2) In the preparation method of DHA-EE and EPA-EE of the present invention, the water used in the hydrolysis reaction and the perfluorosulfonic acid resin used as the catalyst can be recycled, which greatly reduces the industrial cost of preparing DHA-EE and EPA-EE and has high sustainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of EPA-EE of Example 1 of the present invention;

[0030] Figure 2 This is the carbon-1NMR spectrum of EPA-EE of Example 1 of the present invention;

[0031] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of DHA-EE of Example 1 of the present invention;

[0032] Figure 4 This is the carbon-NMR spectrum of DHA-EE of Example 1 of the present invention;

[0033] Figure 5 This is the gas chromatogram of DHA-EE of Example 1 of the present invention;

[0034] Figure 6 This is the gas chromatogram of DHA-EE in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are conventional commercially available raw materials in the art, and the equipment used is conventional equipment in the art.

[0036] Example 1

[0037] A method for preparing DHA-EE and EPA-EE is carried out according to the following steps:

[0038] Step S1: Deionized water and fish oil are pumped into the upper and lower parts of the reaction tower at the same time, and high-pressure steam with a pressure of not less than 10MPa is input into the upper, middle and lower parts of the reaction tower. The input flow rate of the high-pressure steam in the upper part is 120kg / h, the input pressure is 12MPa, and the temperature is 120°C. The input flow rate of the high-pressure steam in the middle part is 80kg / h, the input pressure is 10MPa, and the temperature is 235°C. The input flow rate of the high-pressure steam in the lower part is 150kg / h, the input pressure is 12MPa, and the temperature of the high-pressure steam is 235°C. The reaction pressure of the reaction tower is 18MPa, the input flow rate of deionized water is 150kg / h, and the input flow rate of fish oil is 150kg / h. The deionized water and fish oil are subjected to ultrasonic treatment in the reaction tower, and the ultrasonic frequency is 100kHz and the power is 650W, and a primary mixture is obtained from the liquid outlet at the top of the reaction tower;

[0039] Step S2: mixing the primary mixture with a potassium hydroxide ethanol solution at a mass ratio of 1:8, wherein the mass ratio of potassium hydroxide to ethanol in the potassium hydroxide ethanol solution is 10:1000, heating and reflux for 3 hours under helium protection, adding the hot solution to a 2-fold volume of a 10% dilute sulfuric acid solution and shaking for 1 minute, allowing to stand for stratification and taking the upper phase to obtain a secondary mixture;

[0040] Step S3: the secondary mixture is mixed with anhydrous ethanol at a volume ratio of 1:3, Nafion-H perfluorosulfonic acid resin is added, and ultrasonic microwave treatment is performed for 60 minutes, with an ultrasonic frequency of 80 kHz and a power of 550 W; the microwave power is 600 W, the perfluorosulfonic acid resin is filtered out, and the ethanol is recovered by rotary evaporation to obtain a tertiary mixture;

[0041] Step S4: subjecting the three-stage mixture to a first-stage molecular distillation, the first-stage molecular distillation conditions are: pre-degassing temperature of 60°C, pre-degassing pressure of 80Pa, operating pressure of 0.1Pa, feed rate of 0.3L / min, distillation temperature of 100°C, and thin film distillation scraper speed of 250r / min, collecting the first-stage heavy phase for a second-stage molecular distillation, the second-stage molecular distillation conditions are: distillation temperature of 150°C, and thin film distillation scraper speed of 220r / min, separating and collecting the second-stage light phase and the second-stage heavy phase, subjecting the second-stage heavy phase to a third-stage molecular distillation, the third-stage molecular distillation conditions are: distillation temperature of 180°C, and thin film distillation scraper speed of 200r / min, and collecting the third-stage heavy phase; wherein the second-stage light phase contains EPA-EE, and the third-stage heavy phase contains DHA-EE.

[0042] Product quality inspection:

[0043] (1) Identification of the structure and purity of EPA-EE in the secondary light phase and DHA-EE in the tertiary heavy phase by nuclear magnetic resonance spectrometry: 10 mg of the secondary light phase and 10 mg of the tertiary heavy phase in Example 1 were taken as samples, 5 mL of deuterated chloroform was added to dissolve the samples, and the dissolved samples were subjected to hydrogen and carbon spectrum determination by a 500 MHz nuclear magnetic resonance spectrometer.

[0044] (2) Gas chromatography was used to determine the mass fraction of EPA-EE in the secondary light phase and DHA-EE in the tertiary heavy phase:

[0045] Take 1 μL of the secondary light phase and 1 μL of the tertiary heavy phase in Example 1 as samples, respectively, and use a CP-sil88 (100m×0.25mm id, 0.2μm) capillary column at a constant flow pressure of 30.8psi, with N2 as the carrier gas, and the flow rate is set to 4.41mL / min. Inject 1 μL of sample with a split ratio of 40:1, the injection port temperature is 250°C, and the detector temperature is set to 270°C. The heating program is: initial temperature 80°C, then rise to 220°C at 4°C / min and hold for 5 minutes, then rise to 240°C at 4°C / min and hold for 10 minutes. Use the area normalization method to process the chromatographic data to determine the mass fractions of EPA-EE in the secondary light phase and DHA-EE in the tertiary heavy phase.

[0046] Test results: Figure 1 to Figure 6 As shown, the EPA-EE and DHA-EE obtained by this method, after being detected by nuclear magnetic resonance spectrometer and gas chromatograph, have a purity of 98.3% and 98.5%.

[0047] Example 2

[0048] A method for preparing DHA-EE and EPA-EE is carried out according to the following steps:

[0049] Step S1: Deionized water and fish oil are pumped into the upper and lower parts of the reaction tower at the same time, and high-pressure steam with a pressure of not less than 10MPa is input into the upper, middle and lower parts of the reaction tower. The input flow rate of the high-pressure steam in the upper part is 100kg / h, the input pressure is 10MPa, and the temperature is 150°C. The input flow rate of the high-pressure steam in the middle part is 100kg / h, the input pressure is 12MPa, and the temperature is 220°C. The input flow rate of the high-pressure steam in the lower part is 100kg / h, the input pressure is 10MPa, and the temperature of the high-pressure steam is 260°C. The reaction pressure of the reaction tower is 20MPa, the input flow rate of deionized water is 160kg / h, and the input flow rate of fish oil is 120kg / h. The deionized water and fish oil are subjected to ultrasonic treatment in the reaction tower, and the ultrasonic frequency is 100kHz and the power is 650W, and a primary mixture is obtained from the liquid outlet at the top of the reaction tower;

[0050] Step S2: mixing the primary mixture with a potassium hydroxide ethanol solution at a mass ratio of 1:10, wherein the mass ratio of potassium hydroxide to ethanol in the potassium hydroxide ethanol solution is 15:1200, heating and reflux for 2.5 hours under helium protection, adding the hot solution to 1 volume of a 15% dilute sulfuric acid solution and shaking for 1 minute, standing and stratifying, and taking the upper phase to obtain a secondary mixture;

[0051] Step S3: the secondary mixture is mixed with anhydrous ethanol at a volume ratio of 1:2, Nafion-H perfluorosulfonic acid resin is added, and ultrasonic microwave treatment is performed for 45 minutes, with an ultrasonic frequency of 65 kHz and a power of 650 W; the microwave power is 550 W, the perfluorosulfonic acid resin is filtered out, and the ethanol is recovered by rotary evaporation to obtain a tertiary mixture;

[0052] Step S4: subjecting the three-stage mixture to a first-stage molecular distillation, the first-stage molecular distillation conditions are: pre-degassing temperature of 60°C, pre-degassing pressure of 80Pa, operating pressure of 0.1Pa, feed rate of 0.3L / min, distillation temperature of 100°C, and thin film distillation scraper speed of 250r / min, collecting the first-stage heavy phase for a second-stage molecular distillation, the second-stage molecular distillation conditions are: distillation temperature of 150°C, and thin film distillation scraper speed of 220r / min, separating and collecting the second-stage light phase and the second-stage heavy phase, subjecting the second-stage heavy phase to a third-stage molecular distillation, the third-stage molecular distillation conditions are: distillation temperature of 180°C, and thin film distillation scraper speed of 200r / min, and collecting the third-stage heavy phase; wherein the second-stage light phase contains EPA-EE, and the third-stage heavy phase contains DHA-EE.

[0053] Product quality inspection: refer to Example 1 for the inspection process.

[0054] Test results: The EPA-EE and DHA-EE obtained by this method were tested by nuclear magnetic resonance spectrometer and gas chromatograph, and the purity reached 98.5% and 98.4%. The test results are highly similar to those in Example 1, and the test spectra are not further displayed.

[0055] Example 3

[0056] A method for preparing DHA-EE and EPA-EE is carried out according to the following steps:

[0057] Step S1: Deionized water and fish oil are pumped into the upper and lower parts of the reaction tower at the same time, and high-pressure steam with a pressure of not less than 10MPa is input into the upper, middle and lower parts of the reaction tower. The input flow rate of the high-pressure steam in the upper part is 150kg / h, the input pressure is 13MPa, and the temperature is 160°C. The input flow rate of the high-pressure steam in the middle part is 90kg / h, the input pressure is 11MPa, and the temperature is 230°C. The input flow rate of the high-pressure steam in the lower part is 150kg / h, the input pressure is 13MPa, and the temperature of the high-pressure steam is 250°C. The reaction pressure of the reaction tower is 16MPa, the input flow rate of deionized water is 150kg / h, and the input flow rate of fish oil is 130kg / h. The deionized water and fish oil are subjected to ultrasonic treatment in the reaction tower, and the ultrasonic frequency is 100kHz and the power is 650W, and a primary mixture is obtained from the liquid outlet at the top of the reaction tower;

[0058] Step S2: mixing the primary mixture with a potassium hydroxide ethanol solution at a mass ratio of 2:9, wherein the mass ratio of potassium hydroxide to ethanol in the potassium hydroxide ethanol solution is 14:1500, heating and reflux for 2 hours under helium protection, adding the hot solution to 3 times the volume of a 10% dilute sulfuric acid solution and shaking for 1 minute, allowing it to stand for stratification and taking the upper phase to obtain a secondary mixture;

[0059] Step S3: the secondary mixture is mixed with anhydrous ethanol at a volume ratio of 1:3, Nafion-H perfluorosulfonic acid resin is added, and ultrasonic microwave treatment is performed for 50 min, with an ultrasonic frequency of 80 kHz and a power of 500 W; the microwave power is 700 W, the perfluorosulfonic acid resin is filtered out, and ethanol is recovered by rotary evaporation to obtain a tertiary mixture;

[0060] Step S4: subjecting the three-stage mixture to a first-stage molecular distillation, the first-stage molecular distillation conditions are: pre-degassing temperature of 60°C, pre-degassing pressure of 80Pa, operating pressure of 0.1Pa, feed rate of 0.3L / min, distillation temperature of 100°C, and thin film distillation scraper speed of 250r / min, collecting the first-stage heavy phase for a second-stage molecular distillation, the second-stage molecular distillation conditions are: distillation temperature of 150°C, and thin film distillation scraper speed of 220r / min, separating and collecting the second-stage light phase and the second-stage heavy phase, subjecting the second-stage heavy phase to a third-stage molecular distillation, the third-stage molecular distillation conditions are: distillation temperature of 180°C, and thin film distillation scraper speed of 200r / min, and collecting the third-stage heavy phase; wherein the second-stage light phase contains EPA-EE, and the third-stage heavy phase contains DHA-EE.

[0061] Product quality inspection: refer to Example 1 for the inspection process.

[0062] Test results: The EPA-EE and DHA-EE obtained by this method were tested by nuclear magnetic resonance spectrometer and gas chromatograph, and the purity reached 98.4% and 98.7%. The test results are highly similar to those in Example 1, and the test spectra are not further displayed.

[0063] The applicant declares that the present invention illustrates a method for preparing DHA-EE and EPA-EE through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0064] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0065] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing DHA-EE and EPA-EE, characterized in that: Follow these steps: Step S1: Deionized water and fish oil are pumped into the upper and lower parts of the reaction tower at the same time, the input flow rate of the deionized water is 150-200 kg / h, the input flow rate of the fish oil is 100-150 kg / h, the reaction pressure of the reaction tower is 10-20 MPa, high-pressure steam with a pressure of not less than 10 MPa is input into the upper, middle and lower parts of the reaction tower, the temperature of the high-pressure steam is 120-260° C., the input flow rate of the high-pressure steam in the upper part is 100-150 kg / h, the input flow rate of the high-pressure steam in the middle part is 80-100 kg / h, and the input flow rate of the high-pressure steam in the lower part is 100-150 kg / h, the deionized water and the fish oil are subjected to ultrasonic treatment in the reaction tower, the ultrasonic frequency is 100-120 kHz, the power is 650 W, and a primary mixture is obtained from the liquid outlet at the top of the reaction tower; Step S2: mixing the primary mixture with potassium hydroxide ethanol solution in a mass ratio of 1-3:8-10, heating and reflux under helium protection for 1-3 hours, adding the hot solution to 1-3 times the volume of dilute sulfuric acid solution and shaking for 0.5-1.5 minutes, letting it stand for stratification and taking the upper phase to obtain a secondary mixture; Step S3: mixing the secondary mixture with anhydrous ethanol at a volume ratio of 1:1 to 3, adding perfluorosulfonic acid resin, filtering out the perfluorosulfonic acid resin after ultrasonic microwave treatment for 30 to 60 minutes, and then rotary evaporating to recover ethanol to obtain a tertiary mixture; Step S4: subjecting the tertiary mixture to primary molecular distillation, collecting the primary heavy phase for secondary molecular distillation, separating and collecting the secondary light phase and the secondary heavy phase, subjecting the secondary heavy phase to tertiary molecular distillation, and collecting the tertiary heavy phase; wherein the secondary light phase contains EPA-EE, and the tertiary heavy phase contains DHA-EE.

2. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In step S1, the temperature of the high-pressure steam in the upper part is 120-180°C, the temperature of the high-pressure steam in the middle part is 200-260°C, and the temperature of the high-pressure steam in the lower part is 220-260°C.

3. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In the step S1, the input pressure of the high-pressure steam in the upper part is 12-15 MPa, the input pressure of the high-pressure steam in the middle part is 10-12 MPa, and the input pressure of the high-pressure steam in the lower part is 12-15 MPa.

4. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In step S2, the mass ratio of potassium hydroxide to ethanol in the potassium hydroxide ethanol solution is 10-15:1000-1500; and the concentration of the dilute sulfuric acid solution is 10%-20%.

5. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In the step S3, the amount of perfluorosulfonic acid resin added is 1 to 5 wt %.

6. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In step S3, the ultrasonic frequency is 60-80kHz, the power is 500-750W; the microwave power is 500-800W.

7. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In step S4, the primary molecular distillation conditions are: pre-degassing temperature of 60°C, pre-degassing pressure of 80Pa, operating pressure of 0.1Pa, feed rate of 0.3L / min, distillation temperature of 100°C, and thin film distillation scraper speed of 250r / min.

8. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In step S4, the secondary molecular distillation conditions are: distillation temperature 150° C., thin film distillation scraper speed 220 r / min.

9. The method for preparing DHA-EE and EPA-EE according to claim 1, characterized in that: In step S4, the three-stage molecular distillation conditions are: distillation temperature 180° C., thin film distillation scraper speed 200 r / min.

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