CN111943837B - Process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography - Google Patents

Process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography Download PDF

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CN111943837B
CN111943837B CN202010717420.7A CN202010717420A CN111943837B CN 111943837 B CN111943837 B CN 111943837B CN 202010717420 A CN202010717420 A CN 202010717420A CN 111943837 B CN111943837 B CN 111943837B
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ethyl ester
dha
epa
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molecular distillation
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CN111943837A (en
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孙继鹏
周晓娇
谢枫才
杨会成
周宇芳
王家星
廖妙飞
陈敏嫣
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Zhejiang Marine Development Research Institute
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Abstract

The invention relates to the technical field of purification processes, and discloses a process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography, aiming at the problems of low purity and serious environmental pollution in the preparation process of EPA or DHA ethyl ester in the prior art, wherein the process comprises the following steps: (1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA or DHA crude product to remove ethanol, thus obtaining low-purity ethyl ester type EPA or DHA; (2) performing the first molecular distillation and the second molecular distillation to obtain a medium-purity ethyl ester type EPA or DHA sample; (3) two-dimensional DAC refining and the third step of molecular distillation or rectification are carried out to prepare the high-purity ethyl ester type EPA or DHA. The invention adopts molecular distillation combined with dynamic axial chromatography for gradual purification and enzyme-base combined ultrasonic transesterification, in the preparation process, the ethyl esterification rate is high, the time is short, no pollution is guaranteed, and the effects of decoloring and deodorizing can be achieved while the purity is improved.

Description

Process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography
Technical Field
The invention relates to the technical field of purification processes, in particular to a process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography.
Background
The demand for health care products and medicaments related to omega-3 polyunsaturated fatty acids continues to increase rapidly at home and abroad. However, at present, the domestic high-end market is seriously impacted by products of countries such as Europe, America, Japan and the like, and the acceptance of consumers on imported products is high. In Japan, etc., the omega-3 polyunsaturated fatty acid ethyl ester has been developed as a drug for treating hyperlipidemia. The high-quality omega-3 polyunsaturated fatty acid raw material is a key restriction link of the industrial chain, the development of a key engineering technology of the high-purity omega-3 polyunsaturated fatty acid industry is imminent, and the research and development of the key technology have great practical significance for promoting the technical upgrade of marine-source health care products and medicines manufactured in China, particularly improving the product quality and the enterprise competitiveness and further occupying huge domestic markets. The market scale of omega-3 polyunsaturated fatty acids reaches billions of dollars, and the asia-pacific region gradually becomes the leading sheep of the global market, which is controlled by some major foreign enterprises. The development of the marine organism source high-purity omega-3 polyunsaturated fatty acid engineering technology is beneficial to improving the quality of related products in China and promoting the development of marine health care products and medicines in China, and the technology has wide market prospect and has positive significance for cultivating and strengthening the new marine industry and developing marine economy in China.
The omega-3 polyunsaturated fatty acid transesterification process mainly comprises a chemical method and an enzymatic method, the alkali catalysis reaction condition is mild, the reaction speed is high, and the defect is that the process is not suitable for the oil reaction with high acid value. The acid catalysis method can treat the raw material with high acid value, but the acid catalysis transesterification reaction speed is lower, higher reaction temperature and alcohol-oil ratio are required, and more byproducts are generated; compared with a chemical method, the method has mild enzyme reaction conditions, avoids adverse reactions such as oxidation, polymerization and isomerization of double bonds of polyunsaturated fatty acids, but has higher cost and unsatisfactory esterification yield.
The patent number CN201810394068.0, the patent name "a production method of omega-3 polyenoic fatty acid ethyl ester", the invention relates to a production method of omega-3 polyenoic fatty acid ethyl ester, and belongs to the technical field of medicines. The invention adopts omega-3 polyene fatty acid triglyceride as raw material, and the raw material is subjected to saponification reaction, acidification reaction and esterification reaction to obtain a crude omega-3 polyene fatty acid ethyl ester product; and then carrying out molecular distillation and urea inclusion on the coarse omega-3 polyenoic fatty acid ethyl ester product to obtain a mixture containing eicosapentaenoic acid ethyl ester and docosahexaenoic acid ethyl ester. The content of omega-3 polyenoic fatty acid of the product obtained by the invention reaches 90%, the content of harmful substances such as acid value, peroxide value, oligomer, cholesterol and the like is far lower than that specified by pharmacopoeia, the problems of high acid value, high peroxide value and excessive heavy metal and pesticide residue in the prior art are solved, the method is simple, the operation is easy, and the method is suitable for large-scale industrial production of the product.
The defects are that the acid method esterification and urea inclusion purification are adopted in the patent, the dosage of the used chemical reagent is large, and the final prepared mixture of EPA and DHA only has the total content of 90%.
Disclosure of Invention
The invention provides a process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography in order to overcome the problems of low purity and serious environmental pollution in the preparation process of EPA or DHA ethyl ester in the prior art, the invention adopts the combination of molecular distillation with dynamic axial chromatography for gradual purification, and the transesterification process adopts enzyme-base combined ultrasonic transesterification; the purification process adopts two-step molecular distillation and a physical method, is environment-friendly and pollution-free, and can achieve the effects of decoloring and deodorization while improving the purity.
In order to achieve the purpose, the invention adopts the following technical scheme:
the process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography comprises the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA or DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type EPA or DHA;
(2) sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester EPA or DHA to obtain a medium-purity ethyl ester EPA or DHA sample;
(3) and (3) sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and third-step molecular distillation or rectification on the medium-purity ethyl ester type EPA or DHA sample to obtain the high-purity ethyl ester type EPA or DHA.
The principle of molecular distillation is to separate molecules of different molecular weights by adjusting the temperature and pressure to obtain a mean free range of molecular motion. The distillation is carried out under the vacuum condition, the average free path of molecular motion is relatively large, so the distillation temperature is reduced, and the polyene fatty acid is effectively prevented from being oxidized and decomposed by heating. During molecular distillation, the smaller molecular weight will flow out of the light phase and the larger molecular weight will flow out of the recombinant phase. Molecular distillation methods also have disadvantages: the method can not separate impurity components with similar molecular weight, similar boiling point and extremely low content, so the method additionally introduces a two-dimensional DAC refining (two-dimensional dynamic axial refining) step to make up the defect, the separation effect of a dynamic axial compression preparation column system with different diameters is equivalent to that of an analysis column, the analysis column is used for screening fillers and amplifying the fillers to DAC, and two groups of DAC columns are used for realizing continuous sample loading and impurity removal to achieve the refining purpose. The high-purity ethyl ester type EPA or DHA is prepared by adopting a method of combining tertiary distillation with two-dimensional DAC refining or combining secondary distillation with two-dimensional DAC refining and rectification.
Preferably, the preparation process of the step (1) is as follows: adding EPA or DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, performing ultrasonic heating reflux at 40-60 ℃, performing transesterification for 4-10h, and concentrating reaction liquid at 48-52 ℃ under the vacuum degree of 0.09-0.1mbar to remove ethanol to obtain low-purity ethyl ester type EPA or DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the added EPA or DHA crude product to the absolute ethanol is 1: 1-4, sodium hydroxide accounts for 0.05-0.3% of the weight of the EPA or DHA crude product, and lipase accounts for 0.5-3% of the weight of the EPA or DHA crude product.
The step avoids the situation that a large amount of enzyme preparation is consumed by single lipase catalysis, so that the production cost of the product is too high, and the enzyme-base combined ultrasonic transesterification is adopted, so that the characteristics of high reaction speed, high esterification rate and good product quality of the base catalysis method can be better exerted under the situation of catalyzing high acid value oil to reduce the acid value, the cost is reduced, and the yield and the quality of the product can be improved.
Preferably, the first molecular distillation process in step (2) is as follows: deodorizing and deodorizing low-purity ethyl ester type EPA or DHA by using pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerance temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3mbar-1×10-1mbar, material flow rate of 0.5-1.5kg/h, film scraping speed of 100-160r/min, material temperature of 30-32 deg.C, external condensation temperature of 30-32 deg.C, evaporation temperature of 90-130 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature.
When the sample flows along the heating plate and is heated, light and heavy molecules can escape from the liquid surface and enter a gas phase, the gas phase molecules of different substances move at different intervals due to different free paths of the light and heavy molecules, and the odor fraction and the fishy smell fraction in the sample are low-boiling-point components with short carbon chains, firstly obtain enough energy to evaporate from the surface of the liquid film, and are condensed and discharged until the sample reaches the condensing plate.
Preferably, the second molecular distillation process in step (2) is as follows: decolorizing EPA or DHA ethyl ester sample after the first step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3mbar-1×10-1Under mbar, the material flow rate is 1.0-3.0kg/h, the film scraping speed is 100-160r/min, the material temperature is 30-32 ℃, the external condensation temperature is 30-32 ℃, the evaporation temperature is 130-180 ℃, the internal condensation temperature is 50 ℃ lower than the evaporation temperature, and two-step molecular distillation is carried out to obtain the medium-purity product with the purity of more than or equal to 70 percentEthyl ester EPA and DHA samples.
Some pigments in the sample are mainly high-boiling-point long carbon chain saturated fatty acids, and when the sample flows along the heating plate and is heated, high-boiling-point heavy molecular components are difficult to escape from the liquid surface and enter a gas phase, so that the high-boiling-point heavy molecular components are discharged along the mixed liquid, and the decoloration effect is realized.
Preferably, the two-dimensional DAC refining process in step (3) is as follows: refining a medium-purity ethyl ester type EPA or DHA sample by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 10-50um particle size; the sample loading amount accounts for 0.5-5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0-85: 15(v/v), the flow rate is 120-; the mobile phase alcohol is methanol or ethanol.
Preferably, the molecular distillation process in the third step in the step (3) is as follows: refining two-dimensional DAC to obtain refined DHA or EPA ethyl ester, removing residual solvent with pilot scale short-range molecular distillation equipment, evaporating to obtain solvent with evaporation area of 0.1 square meter, maximum tolerance temperature of 350 deg.C, and vacuum degree of 1 × 10-3mbar-1×10-1mbar, material flow rate of 2.0-3.0kg/h, film scraping speed of 100-160r/min, material temperature of 30-32 ℃, external condensation temperature of 30-32 ℃, evaporation temperature of 60-90 ℃, and internal condensation temperature of 30 ℃ lower than the evaporation temperature, so as to obtain high-purity ethyl ester type EPA or DHA, namely, the purity is more than or equal to 98%.
After the sample is refined by DAC, although the mobile phase organic solvent is removed by reduced pressure distillation, the organic solvent and a small amount of water remain in the product, which affects the safety and stability of the product. When the conventional distillation method is used to remove the solvent, the danger of decomposition or polymerization of the product at high temperature due to high operation temperature and long heating time is faced, thus causing difficulty in removing the residual solvent. The process can completely remove the organic residual solvent and water in the product at lower temperature in shorter time by the evaporation characteristic of molecular distillation reduced pressure film formation.
Preferably, the rectification process in step (3) is as follows: refining by two-dimensional DAC to obtain refined DHA or EPA ethyl ester fraction, preheating to 50-54 deg.C, feeding into a rectifying tower for separation, collecting solvent and water at the tower top, and collecting high-purity EPA or DHA at the tower bottom; the reflux ratio of the top of the rectifying tower is 0.5-2.5, the operating pressure is 0.12-0.14Mpa, the temperature of the top of the tower is 40-60 ℃, and the temperature of the bottom of the tower is 90-110 ℃.
Preferably, the rectification column used in the rectification process is filled with aerogel-filled hollow porous silica adsorbent, and the preparation steps are as follows:
A. preparing hollow porous silica: placing 0.1-0.2% by mass of hexadecyl trimethyl ammonium bromide solution into a container, adding 28-30wt% by mass of concentrated ammonia water into the solution, continuously stirring for 20-30min, then dripping a mixture of n-hexane and tetraethyl orthosilicate at the speed of 1.0-1.2mL/min, after dripping, continuously stirring for reacting for 10-12h, and after the reaction system gradually turns white; centrifuging, washing with absolute ethyl alcohol, and drying to obtain hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres; ultrasonically dispersing the composite microspheres in a mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol with the mass fraction of 50-60%, refluxing for 4-5 hours under magnetic stirring, extracting with acetone to remove hexadecyl trimethyl ammonium bromide, washing with ethyl alcohol, filtering, and drying the obtained white sample in a vacuum oven at the temperature of 60-80 ℃ for 10-12 hours to finally obtain hollow porous silicon dioxide microspheres;
B. activating hollow porous silica: dispersing the silicon dioxide microspheres into dimethylformamide, adding hexamethylene diisocyanate, stirring and reacting for 4-6h at 60-80 ℃, adding 3-triethoxysilyl-1-propylamine, continuously stirring and reacting for 2-4h at 60-70 ℃, centrifuging, and alternately cleaning with absolute ethyl alcohol and ultrapure water to obtain activated hollow porous silicon dioxide;
C. preparing filling gel liquid: mixing the composite carbon sol and titanium dioxide according to the mass ratio of 40-60: 1-3 to obtain composite sol, aging the composite sol for 20-36h, then carrying out solvent replacement on the composite sol for 12-16h by using excessive absolute ethyl alcohol, and then removing the absolute ethyl alcohol to obtain filling gel;
D. aerogel-filled hollow porous silica: and C, adding the hollow porous silica microspheres activated in the step B into the filling gel liquid prepared in the step C, stirring for 4-5 hours to enable the gel liquid to be filled into the filling hollow porous silica microspheres, separating the gel liquid from the hollow porous silica microspheres again, drying the filling hollow porous silica microspheres at 60-80 ℃ for 20-30min, carbonizing at 300-600 ℃ to obtain carbonized aerogel filling hollow porous silica, and cleaning and drying to obtain the finished product.
The adsorbent is prepared by preparing hollow porous silica microspheres which have good adsorption performance and large pore adsorption capacity, the prepared hollow porous silica microspheres have hollow inner surfaces and tiny hollow pores besides the outer surfaces, and the adsorption surface area of the hollow porous silica microspheres can be multiplied, has positive effect on improving the adsorption capacity of the hollow porous silica microspheres and obviously increases the adsorption capacity of the hollow porous silica microspheres, but due to the hollow porous structure of the shell layer and the hollow structure inside the shell layer, the specific surface area is increased, meanwhile, a wide channel is provided for the passage of fluid, and when the gas or liquid purified in the rectifying tower is filled, the gas or liquid is easy to pass through the hollow porous silica microspheres, so that the purification is insufficient; therefore, the invention takes the hollow porous silica microspheres as a frame structure, and composite gel filling is carried out on the hollow part in the hollow porous silica microspheres, and the aerogel structure formed after the filled composite gel is dried has stronger adsorption capacity, thus improving the complexity of the path of purified EPA or DHA ethyl ester passing through the microspheres, improving the contact time of EPA or DHA ethyl ester and the microsphere material, finally improving the purification effect and shortening the preparation period.
In the step A, white hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres are synthesized, and hexadecyl trimethyl ammonium bromide components in the microspheres are removed to form a hollow porous structure so as to increase the specific surface area; b, performing activation grafting on the amino structure on the hollow porous silica microspheres in order to increase the surface activity of the hollow porous silica microspheres, promote the better integrity of the combination with the composite gel added later and prolong the service cycle of the high-efficiency adsorbent; step C, preparing the composite sol, so that the prepared sol has a good pore-forming effect, the specific surface area and the adsorption and purification effect of the finally prepared aerogel are increased, the composite sol is prepared to be neutral, and the adsorption rate of the adsorbent to EPA or DHA ethyl ester can be reduced; and D, filling the composite gel into the hollow porous silica microspheres, and carrying out carbonization and shaping on the composite gel to finally prepare the high-efficiency adsorbent with good integrity, good formability and good adsorption effect.
Preferably, the volume ratio of the hexadecyl trimethyl ammonium bromide solution, the concentrated ammonia water, the mixed solution of normal hexane and tetraethyl orthosilicate and the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol in the step A is 140-160: 3-5: 24-28: 100-; wherein the volume ratio of the normal hexane to the tetraethyl orthosilicate in the mixed solution of the normal hexane and the tetraethyl orthosilicate is 4-5: 1-1.5; the volume ratio of concentrated hydrochloric acid to absolute ethyl alcohol in the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol is 1: 98-102; in the step B, the mass ratio of the silicon dioxide microspheres to the hexamethylene diisocyanate to the 3-triethoxysilyl-1-propylamine is 10: 0.2-0.4: 0.8-1.2.
In the step B, 3-triethoxysilyl-1-propylamine is adopted to graft the hollow porous silica, so that the grafting efficiency is better, more active sites can be provided for the inner surface and the outer surface of the hollow porous silica, and a solid foundation is laid for the subsequent preparation of the composite gel filled hollow porous silica with good integrity and high binding degree.
Preferably, the preparation method of the composite carbon sol in the step C comprises the following steps: 2-furfural, water-soluble phenolic resin, carbon nano tubes, methyl cellulose, brucite fibers, sodium bicarbonate and water are mixed according to the mass ratio of 5-7: 1: 0.5-0.7: 0.3-0.5: 0.05-0.08: 0.01-0.03: 100, uniformly stirring to obtain a mixed solution, dropwise adding ammonia water with the concentration of 0.25-0.75mol/L into the mixed solution at the speed of 10-20mL/min under the stirring condition, and adjusting the pH value to be neutral; then reacting for 8-10h at 65-75 ℃ to prepare composite carbon sol; and D, the carbonization process of the filled hollow porous silica microspheres comprises the following steps: heating the filled hollow porous silica microspheres to 300-500 ℃ at the speed of 6-10 ℃/min for pre-carbonization for 30-40 min; then heating to 500-600 ℃ at the rate of 18-22 ℃ and carbonizing for 50-60min
The carbon nano tube is in a hollow tubular shape and has a pore canal with a nano size, the strength of the material can be improved on the premise that the porosity of the composite carbon sol is not influenced as much as possible, the tenacity of the material can be improved by the brucite fiber, and the sodium bicarbonate has better pore-forming efficiency.
The compound gel that fills adopts progressively heating, and the carbomorphism is accomplished to the form of carbomorphism gradually, and the carbomorphism here is a process step by step, and it is more even to make the inside hole that forms of carbomorphism aerogel, improves the porosity for the carbomorphism is more abundant, promotes its adsorption efficiency, can strengthen the intensity of result again, makes the inside aperture wall of aerogel difficult collapse, and the guarantor type effect is better.
Therefore, the invention has the following beneficial effects:
(1) the invention provides a process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography, the invention adopts the combination of molecular distillation with dynamic axial chromatography for gradual purification, and adopts an enzyme-base combined ultrasonic transesterification process;
(2) the purification process adopts two-step molecular distillation and a physical method, is environment-friendly and pollution-free, can achieve the effects of decoloring and deodorization while improving the purity, and can further improve the purity of EPA or DHA ethyl ester by separating impurity components with similar boiling points and very low contents with EPA or DHA ethyl ester through combining a two-dimensional DAC refining process;
(3) the method has the advantages that the hollow porous silica adsorbent is filled with the gas gel in the rectifying tower of the rectification, so that EPA or DHA ethyl ester is purified, the adsorption of the adsorbent to the EPA or DHA ethyl ester is reduced, and the solvent and the water in the EPA or DHA ethyl ester are removed to promote the final preparation of high-purity EPA or DHA ethyl ester.
Drawings
FIG. 1 is a schematic diagram of the reaction scheme of the present invention.
FIG. 2 is a gas chromatogram of pure DHA ethyl ester in two-step molecular distillation according to the present invention.
FIG. 3 is a gas chromatogram of EPA ethyl ester of purity in two-step molecular distillation according to the present invention.
FIG. 4 is a schematic diagram of a two-step molecular distillation DHA ethyl ester of the present invention (4.1 is two-step molecular distillation DHA ethyl ester pigment; and 4.2 is two-step molecular distillation decolorized DHA ethyl ester).
Fig. 5 is a gas chromatogram of high purity DHA ethyl ester according to the invention.
FIG. 6 is a gas chromatogram of high purity EPA ethyl ester of the present invention.
Fig. 7 is a gas chromatogram of high purity DHA ethyl ester according to the invention.
FIG. 8 is a gas chromatogram of high purity EPA ethyl ester of the present invention.
Detailed Description
The present invention will be further described with reference to the following embodiments.
Example 1
The process for preparing high-purity EPA ethyl ester by combining molecular distillation with dynamic axial chromatography comprises the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA crude product to remove ethanol so as to obtain low-purity ethyl ester EPA;
the preparation process comprises the following steps: adding EPA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, performing ultrasonic heating reflux at 50 ℃ for transesterification reaction for 8h, and concentrating the reaction liquid at 50 ℃ under the vacuum degree of 0.095mbar to remove ethanol to obtain low-purity ethyl ester type EPA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the added EPA crude product to the absolute ethanol is 1: 2.5, the sodium hydroxide accounts for 0.2 percent of the weight of the EPA crude product, and the lipase accounts for 1.5 percent of the weight of the EPA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester EPA to obtain a medium-purity ethyl ester EPA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type EPA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2mbar, material flow rate of 1kg/h, film scraping speed of 130r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second step of molecular distillation process is as follows: decolorizing the EPA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2Under the mbar, the material flow rate is 2kg/h, the film scraping speed is 130r/min, the material temperature is 31 ℃, the external condensation temperature is 30-32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, thus obtaining the medium-purity ethyl ester EPA sample with the purity of more than or equal to 70 percent.
(3) Sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and third-step molecular distillation on the medium-purity ethyl ester EPA sample to prepare high-purity ethyl ester EPA;
the two-dimensional DAC refining process comprises the following steps: refining a medium-purity ethyl ester EPA sample by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and a particle size of 30 mu m; the sample loading amount accounts for 3% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 50: 15(v/v), the flow rate is 160ml/min, the detection wavelength is 204nm, EPA ethyl ester fraction is collected, and the mobile phase is removed by adopting the concentration of 0.095mbar and 50 ℃; the mobile phase alcohol is methanol or ethanol;
the third step of molecular distillation comprises the following steps: refining by two-dimensional DAC to obtain refined EPA ethyl ester, removing residual solvent by using pilot scale short-range molecular distillation equipment, evaporating to obtain EPA ethyl ester with evaporation area of 0.1 square meter and maximum tolerance temperature of 350 deg.CIs 1 x 10- 2mbar, material flow rate of 2.5kg/h, film scraping rate of 130r/min, material temperature of 31 deg.C, external condensation temperature of 31 deg.C, evaporation temperature of 75 deg.C, and internal condensation temperature 30 deg.C lower than evaporation temperature to obtain high purity ethyl ester EPA with purity of 98% or more.
Example 2
The difference from the example 1 lies in that the molecular distillation is combined with the dynamic axial chromatography to prepare the high-purity DHA ethyl ester, and the process steps are as follows:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type DHA;
the preparation process comprises the following steps: adding a DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, performing ultrasonic heating reflux at 50 ℃ for transesterification reaction for 8 hours, and concentrating the reaction solution at 50 ℃ under the vacuum degree of 0.09mbar to remove ethanol to obtain low-purity ethyl ester type DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the mass ratio of the added DHA crude product to the absolute ethanol is 1: 1-4, the sodium hydroxide accounts for 0.05 percent of the mass of the DHA crude product, and the lipase accounts for 0.5 percent of the mass of the DHA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester DHA to obtain a medium-purity ethyl ester DHA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type DHA by using pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerance temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3mbar, material flow rate of 0.5kg/h, film scraping speed of 100r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second molecular distillation process comprises the following steps: decolorizing the DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3At mbar, material flow rate is 1.0kg/h, film scraping speed is 100r/min, material temperature is 31 deg.C, external condensation temperature is 30 deg.C, and steaming is performedThe temperature is 150 ℃, the internal condensation temperature is 50 ℃ lower than the evaporation temperature, and then the medium-purity ethyl ester type DHA sample with the purity more than or equal to 70% is obtained.
(3) Sequentially carrying out two-dimensional DAC refining and third-step molecular distillation on the medium-purity ethyl ester type DHA sample to prepare high-purity ethyl ester type DHA;
the two-dimensional DAC refining process comprises the following steps: refining a medium-purity ethyl ester type DHA sample by adopting a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 10 mu m of particle size; the sample loading amount accounts for 0.5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0: 15(v/v), the flow rate is 120ml/min, the detection wavelength is 204nm, DHA ethyl ester fraction is collected, and the mobile phase is removed by adopting the vacuum degree of 0.09mbar and the concentration at 50 ℃; the mobile phase alcohol is methanol or ethanol;
the third step of molecular distillation comprises the following steps: axially refining by two-dimensional DAC to obtain refined DHA ethyl ester, removing residual solvent by using pilot scale short-range molecular distillation equipment, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 x 10-3mbar, material flow rate of 2.0kg/h, film scraping speed of 100r/min, material temperature of 30 ℃, external condensation temperature of 31 ℃, evaporation temperature of 75 ℃, and internal condensation temperature of 30 ℃ lower than the evaporation temperature, so as to obtain high-purity ethyl ester type DHA, namely, the purity is more than or equal to 98%.
Example 3
The difference from the example 1 lies in that the molecular distillation and dynamic axial chromatography are combined to prepare the high-purity DHA ethyl ester, and the process steps are as follows:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type DHA;
the preparation process comprises the following steps: adding a DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 50 ℃, refluxing for transesterification reaction for 8 hours, and concentrating the reaction solution at 50 ℃ under the vacuum degree of 0.1mbar to remove ethanol, thereby obtaining low-purity ethyl ester type DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the mass ratio of the added DHA crude product to the absolute ethanol is 1: 4, the sodium hydroxide accounts for 0.3 percent of the mass of the DHA crude product, and the lipase accounts for 3 percent of the mass of the DHA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester type DHA to obtain a medium-purity ethyl ester type DHA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type DHA by using pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerance temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-1mbar, material flow rate of 1.5kg/h, film scraping speed of 160r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second molecular distillation process comprises the following steps: decolorizing the DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-1Under mbar, the material flow rate is 3.0kg/h, the film scraping rate is 160r/min, the material temperature is 31 ℃, the external condensation temperature is 32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, so that the medium-purity ethyl ester type DHA sample with the purity of more than or equal to 70% is obtained.
(3) Sequentially carrying out two-dimensional DAC refining and third-step molecular distillation on the medium-purity ethyl ester type DHA sample to prepare high-purity ethyl ester type DHA;
the two-dimensional DAC refining process comprises the following steps: refining the ethyl ester type DHA sample with medium purity by adopting a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and a particle size of 50 um; the sample loading amount accounts for 5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 85: 15(v/v), the flow rate is 200ml/min, the detection wavelength is 204nm, the DHA ethyl ester fraction is collected, and the mobile phase is removed by adopting the vacuum degree of 0.1mbar and the concentration at 50 ℃; the mobile phase alcohol is methanol or ethanol;
the third step of molecular distillation comprises the following steps: refining with two-dimensional DAC to obtain refined DHA ethyl ester, removing residual solvent with pilot scale short-range molecular distillation equipment having evaporation area of 0.1 square meter, maximum tolerance temperature of 350 deg.C, and vacuum degree of 1 × 10- 1mbar, material flow rate of 3.0kg/h, film scraping speed of 160r/min, and material temperature of 32The external condensation temperature is 31 ℃, the evaporation temperature is 75 ℃, and the internal condensation temperature is 30 ℃ lower than the evaporation temperature, so that the high-purity ethyl ester type DHA is obtained, namely the purity is more than or equal to 98%.
Example 4
The difference with the embodiment 1 is that the molecular distillation is combined with the dynamic axial chromatography to prepare the high-purity EPA ethyl ester, and the process steps are as follows:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA crude product to remove ethanol so as to obtain low-purity ethyl ester EPA;
the preparation process comprises the following steps: adding EPA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, performing ultrasonic heating reflux at 50 ℃ for transesterification reaction for 8h, and concentrating the reaction liquid at 50 ℃ by adopting a vacuum degree of 0.092mbar to remove ethanol, thereby obtaining low-purity ethyl ester type EPA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the added EPA crude product to the absolute ethanol is 1: 2, the sodium hydroxide accounts for 0.015 percent of the weight of the EPA crude product, and the lipase accounts for 2.2 percent of the weight of the EPA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester EPA to obtain a medium-purity ethyl ester EPA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type EPA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 5 multiplied by 10-2mbar, material flow rate of 1.2kg/h, film scraping speed of 120r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second step of molecular distillation process is as follows: decolorizing the EPA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 9 multiplied by 10-3Under mbar, the material flow rate is 2.2kg/h, the film scraping speed is 110r/min, the material temperature is 31 deg.C, the external condensation temperature is 31 deg.C, the evaporation temperature is 150 deg.C, and the internal condensation temperature is 50 deg.C lower than the evaporation temperature, to obtain medium-purity ethyl with purity of 70% or moreEster EPA samples.
(3) Sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and third-step molecular distillation on the medium-purity ethyl ester EPA sample to prepare high-purity ethyl ester EPA;
the two-dimensional DAC refining process comprises the following steps: refining a medium-purity ethyl ester EPA sample by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 20 mu m of particle size; the sample loading amount accounts for 3.5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 65: 15(v/v), the flow rate is 180ml/min, the detection wavelength is 204nm, EPA ethyl ester fraction is collected, and the mobile phase is removed by adopting the concentration of 0.98mbar and 50 ℃; the mobile phase alcohol is methanol or ethanol;
the third step of molecular distillation comprises the following steps: refining two-dimensional DAC to obtain refined EPA ethyl ester, removing residual solvent by using pilot scale short-range molecular distillation equipment, evaporating to obtain EPA ethyl ester with evaporation area of 0.1 square meter, maximum tolerable temperature of 350 deg.C and vacuum degree of 0.2 × 10- 1mbar, material flow rate of 2.8kg/h, film scraping rate of 150r/min, material temperature of 30.5 deg.C, external condensation temperature of 31 deg.C, evaporation temperature of 75 deg.C, and internal condensation temperature of 30 deg.C lower than evaporation temperature to obtain high purity ethyl ester type EPA, i.e. purity greater than or equal to 98%.
Example 5
The process for preparing the high-purity DHA ethyl ester by combining molecular distillation with dynamic axial chromatography comprises the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type DHA;
the preparation process comprises the following steps: adding a DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, performing reflux at 50 ℃ by ultrasonic heating for transesterification reaction for 8 hours, and concentrating the reaction solution at 50 ℃ under the vacuum degree of 0.095mbar to remove ethanol to obtain low-purity ethyl ester type DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the mass ratio of the added DHA crude product to the absolute ethanol is 1: 2.5, the sodium hydroxide accounts for 0.2 percent of the mass of the DHA crude product, and the lipase accounts for 1.5 percent of the mass of the DHA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester type DHA to obtain a medium-purity ethyl ester type DHA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type DHA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2mbar, material flow rate of 1kg/h, film scraping speed of 130r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second step of molecular distillation process is as follows: decolorizing the DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2Under the mbar, the material flow rate is 2kg/h, the film scraping speed is 130r/min, the material temperature is 31 ℃, the external condensation temperature is 30-32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, so that the medium-purity ethyl ester type DHA sample with the purity of more than or equal to 70% is obtained.
(3) Sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and rectification on the medium-purity ethyl ester type DHA sample to prepare high-purity ethyl ester type DHA;
the two-dimensional DAC refining process comprises the following steps: refining the ethyl ester type DHA sample with medium purity by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 10-50um particle size; the sample loading amount accounts for 0.5-5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0-85: 15(v/v), the flow rate is 120-200ml/min, the detection wavelength is 204nm, and the DHA ethyl ester fraction is collected; the mobile phase alcohol is methanol or ethanol;
the rectification process comprises the following steps: refining through a two-dimensional DAC to obtain refined DHA ethyl ester fraction, preheating to 52 ℃, feeding to a rectifying tower for separation, extracting solvent and water from the tower top, and extracting high-purity DHA from the tower kettle; the reflux ratio of the top of the rectifying tower is 1.5, the operating pressure is 0.13Mpa, the temperature of the top of the tower is 50 ℃, and the temperature of the bottom of the tower is 100 ℃.
The method is characterized in that a rectifying tower used in the rectifying process is filled with aerogel filled hollow porous silica adsorbent, and the preparation steps are as follows:
A. preparing hollow porous silicon dioxide: placing 0.15 mass percent of hexadecyl trimethyl ammonium bromide solution into a container, adding 29 mass percent of strong ammonia water into the solution, continuously stirring for 25min, then, dripping a mixture of n-hexane and tetraethyl orthosilicate at the speed of 1.1mL/min, continuously stirring for reacting for 11h after dripping is finished, and after the reaction system gradually turns white; centrifuging, washing with absolute ethyl alcohol, and drying to obtain hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres; ultrasonically dispersing the composite microspheres in a mixed solution of 55 mass percent of concentrated hydrochloric acid and absolute ethyl alcohol, refluxing for 4.5 hours under magnetic stirring, extracting with acetone to remove hexadecyl trimethyl ammonium bromide, washing with ethyl alcohol, filtering, and drying the obtained white sample in a vacuum oven at 70 ℃ for 11 hours to finally obtain hollow porous silicon dioxide microspheres; in the step A, the volume ratio of the cetyl trimethyl ammonium bromide solution, the strong ammonia water, the mixed solution of normal hexane and tetraethyl orthosilicate and the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol is 150: 4: 26: 105; wherein the volume ratio of the normal hexane to the tetraethyl orthosilicate in the mixed solution of the normal hexane and the tetraethyl orthosilicate is 4.5: 1.2; the volume ratio of concentrated hydrochloric acid to absolute ethyl alcohol in the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol is 1: 100; in the step B, the mass ratio of the silicon dioxide microspheres to the hexamethylene diisocyanate to the 3-triethoxysilyl-1-propylamine is 10: 0.3: 1.0;
B. activation of hollow porous silica: dispersing the silicon dioxide microspheres into dimethylformamide, adding hexamethylene diisocyanate, stirring and reacting for 5 hours at 70 ℃, adding 3-triethoxysilyl-1-propylamine, continuously stirring and reacting for 3 hours at 65 ℃, centrifuging, and alternately cleaning with absolute ethyl alcohol and ultrapure water to obtain activated hollow porous silicon dioxide;
C. preparing a filling gel liquid: mixing the composite carbon sol and titanium dioxide according to the mass ratio of 50: 2, uniformly mixing to obtain composite sol, aging the composite sol for 28 hours, then performing solvent replacement on the composite sol for 14 hours by using excessive absolute ethyl alcohol, and then removing the absolute ethyl alcohol to obtain filling gel; the preparation method of the composite carbon sol in the step C comprises the following steps: mixing 2-furaldehyde, water-soluble phenolic resin, carbon nano tubes, methyl cellulose, brucite fibers, sodium bicarbonate and water according to a mass ratio of 6: 1: 0.6: 0.4: 0.06: 0.02: 100, uniformly stirring to obtain a mixed solution, dropwise adding 0.5mol/L ammonia water into the mixed solution at the speed of 15mL/min under the stirring condition, and adjusting the pH value to be neutral; then reacting for 9 hours at 70 ℃ to prepare composite carbon sol;
D. aerogel-filled hollow porous silica: c, adding the activated hollow porous silica microspheres obtained in the step B into the filling gel liquid obtained in the step C, stirring for 4.5 hours to enable the gel liquid to be filled into the filled hollow porous silica microspheres, separating the gel liquid from the hollow porous silica microspheres again, drying the filled hollow porous silica microspheres at 70 ℃ for 25min, carbonizing at 450 ℃ to obtain carbonized aerogel filled hollow porous silica, and cleaning and drying the carbonized aerogel filled hollow porous silica to obtain a finished product; and D, the carbonization process of the filled mesoporous silica microspheres comprises the following steps: heating the filled mesoporous silica microspheres to 400 ℃ at the speed of 8 ℃/min for pre-carbonization for 35 min; then the temperature is raised to 550 ℃ at the rate of 20 ℃ and carbonized for 55 min.
Example 6
The process for preparing high-purity EPA ethyl ester by combining molecular distillation with dynamic axial chromatography comprises the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA crude product to remove ethanol so as to obtain low-purity ethyl ester EPA;
the preparation process comprises the following steps: adding EPA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, performing ultrasonic heating reflux at 50 ℃ for transesterification reaction for 8h, and concentrating the reaction liquid at 50 ℃ by adopting a vacuum degree of 0.09mbar to remove ethanol, thus obtaining low-purity ethyl ester type EPA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the added EPA crude product to the absolute ethanol is 1: 1-4, the sodium hydroxide accounts for 0.05 percent of the weight of the EPA crude product, and the lipase accounts for 0.5 percent of the weight of the EPA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester EPA to obtain a medium-purity ethyl ester EPA sample;
the first step of molecular distillation process is as follows: adopting pilot scale shortThe low-purity ethyl ester EPA is deodorized and deodorized by the molecular distillation equipment to remove low-boiling-point fatty acid impurities, the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3mbar, material flow rate of 0.5kg/h, film scraping speed of 100r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second molecular distillation process comprises the following steps: decolorizing EPA ethyl ester sample after first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurity, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3Under mbar, the material flow rate is 1.0kg/h, the film scraping speed is 100r/min, the material temperature is 31 ℃, the external condensation temperature is 30 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, thus obtaining the medium-purity ethyl ester EPA sample with the purity of more than or equal to 70 percent.
(3) Sequentially carrying out two-dimensional DAC refining rectification on the medium-purity ethyl ester EPA sample to prepare high-purity ethyl ester EPA; the two-dimensional DAC refining process comprises the following steps: refining the ethyl ester EPA sample with medium purity by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 10-50um particle size; the sample loading amount accounts for 0.5-5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0-85: 15(v/v), the flow rate is 120-; the mobile phase alcohol is methanol or ethanol;
the rectification process comprises the following steps: refining by a two-dimensional DAC to obtain refined EPA ethyl ester fraction, preheating to 50 ℃, feeding the refined EPA ethyl ester fraction into a rectifying tower for separation, extracting solvent and water from the tower top, and extracting high-purity EPA from the tower kettle; the reflux ratio of the top of the rectifying tower is 0.5, the operating pressure is 0.12Mpa, the temperature of the top of the tower is 40 ℃, and the temperature of the bottom of the tower is 110 ℃.
The rectification column used in the rectification process is filled with aerogel filled hollow porous silica adsorbent, and the preparation steps are as follows:
A. preparing hollow porous silicon dioxide: placing 0.1% by mass of hexadecyl trimethyl ammonium bromide solution into a container, adding 28 wt% by mass of strong ammonia water into the solution, continuously stirring for 25min, then, dripping a mixture of n-hexane and tetraethyl orthosilicate at a speed of 1.0mL/min, continuously stirring for reaction for 10h after dripping is finished, and after a reaction system gradually turns white; centrifuging, washing with absolute ethyl alcohol, and drying to obtain hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres; ultrasonically dispersing the composite microspheres in a mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol with the mass fraction of 50%, refluxing for 4.5 hours under magnetic stirring, extracting with acetone to remove hexadecyl trimethyl ammonium bromide, washing with ethyl alcohol, filtering, and drying the obtained white sample in a vacuum oven at 70 ℃ for 11 hours to finally obtain hollow porous silicon dioxide microspheres; in the step A, the volume ratio of the hexadecyl trimethyl ammonium bromide solution, the strong ammonia water, the mixed solution of normal hexane and tetraethyl orthosilicate and the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol is 140: 5: 24: 110; wherein the volume ratio of the normal hexane to the tetraethyl orthosilicate in the mixed solution of the normal hexane and the tetraethyl orthosilicate is 5: 1; the volume ratio of the concentrated hydrochloric acid to the absolute ethyl alcohol in the mixed solution of the concentrated hydrochloric acid and the absolute ethyl alcohol is 1: 98, respectively; in the step B, the mass ratio of the silicon dioxide microspheres to the hexamethylene diisocyanate to the 3-triethoxysilyl-1-propylamine is 10: 0.4: 0.8;
B. activation of hollow porous silica: dispersing the silicon dioxide microspheres into dimethylformamide, adding hexamethylene diisocyanate, stirring and reacting for 5 hours at 70 ℃, adding 3-triethoxysilyl-1-propylamine, continuously stirring and reacting for 3 hours at 65 ℃, centrifuging, and alternately cleaning with absolute ethyl alcohol and ultrapure water to obtain activated hollow porous silicon dioxide;
C. preparing a filling gel liquid: mixing the composite carbon sol and titanium dioxide according to the mass ratio of 40: 3, uniformly mixing to obtain composite sol, aging the composite sol for 28 hours, then carrying out solvent replacement on the composite sol for 12 hours by using excessive absolute ethyl alcohol, and then removing the absolute ethyl alcohol to obtain filling gel; the preparation method of the composite carbon sol in the step C comprises the following steps: mixing 2-furaldehyde, water-soluble phenolic resin, carbon nano tubes, methyl cellulose, brucite fibers, sodium bicarbonate and water according to a mass ratio of 5: 1: 0.5: 0.5: 0.05: 0.01: 100, uniformly stirring to obtain a mixed solution, dropwise adding ammonia water with the concentration of 0.25mol/L into the mixed solution at the speed of 15mL/min under the stirring condition, and adjusting the pH value to be neutral; then reacting for 9 hours at 70 ℃ to prepare composite carbon sol;
D. aerogel-filled hollow porous silica: c, adding the activated hollow porous silica microspheres obtained in the step B into the filling gel liquid obtained in the step C, stirring for 4.5 hours to enable the gel liquid to be filled into the filling hollow porous silica microspheres, separating the gel liquid from the hollow porous silica microspheres again, drying the filling hollow porous silica microspheres at 70 ℃ for 25min, then carbonizing at 300 ℃ to obtain carbonized aerogel filling hollow porous silica, and cleaning and drying the carbonized aerogel filling hollow porous silica to obtain a finished product; and D, the carbonization process of the filled mesoporous silica microspheres comprises the following steps: heating the filled mesoporous silica microspheres to 400 ℃ at the speed of 6 ℃/min, and pre-carbonizing for 35 min; then the temperature is raised to 500 ℃ at the rate of 20 ℃ and carbonized for 55 min.
Example 7
The difference from the example 1 lies in that the molecular distillation is combined with the dynamic axial chromatography to prepare the high-purity DHA ethyl ester, and the process steps are as follows:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type DHA;
the preparation process comprises the following steps: adding a DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 50 ℃, refluxing for transesterification reaction for 8 hours, and concentrating the reaction solution at 50 ℃ under the vacuum degree of 0.1mbar to remove ethanol to obtain low-purity ethyl ester type DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the mass ratio of the added DHA crude product to the absolute ethanol is 1: 4, the sodium hydroxide accounts for 0.3 percent of the mass of the DHA crude product, and the lipase accounts for 3 percent of the mass of the DHA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester type DHA to obtain a medium-purity ethyl ester type DHA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type DHA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is1×10-1mbar, material flow rate of 1.5kg/h, film scraping speed of 160r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second step of molecular distillation process is as follows: decolorizing the DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-1Under mbar, the material flow rate is 3.0kg/h, the film scraping speed is 160r/min, the material temperature is 31 ℃, the external condensation temperature is 32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, thus obtaining the medium-purity ethyl ester type DHA sample with the purity of more than or equal to 70%.
(3) Sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and rectification on the medium-purity ethyl ester type DHA sample to prepare high-purity ethyl ester type DHA;
the two-dimensional DAC refining process comprises the following steps: refining a medium-purity ethyl ester type DHA sample by adopting a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and a particle size of 50 mu m; the sample loading amount accounts for 5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 85: 15(v/v), the flow rate is 200ml/min, the detection wavelength is 204nm, and DHA ethyl ester fraction is collected; the mobile phase alcohol is methanol or ethanol;
the rectification process comprises the following steps: obtaining refined DHA ethyl ester fraction axially through two-dimensional DAC refining, preheating to 54 ℃, feeding into a rectifying tower for separation, extracting solvent and water from the tower top, and extracting high-purity DHA from the tower kettle; the reflux ratio of the top of the rectifying tower is 2.5, the operating pressure is 0.12Mpa, the temperature of the top of the tower is 60 ℃, and the temperature of the bottom of the tower is 90 ℃.
The method is characterized in that a rectifying tower used in the rectifying process is filled with aerogel filled hollow porous silica adsorbent, and the preparation steps are as follows:
A. preparing hollow porous silicon dioxide: placing 0.2% by mass of hexadecyl trimethyl ammonium bromide solution into a container, adding 30wt% by mass of strong ammonia water into the solution, continuously stirring for 25min, then, dripping a mixture of n-hexane and tetraethyl orthosilicate at a speed of 1.0mL/min, continuously stirring for reaction for 12h after dripping is finished, and after a reaction system gradually turns white; centrifuging, washing with absolute ethyl alcohol, and drying to obtain hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres; ultrasonically dispersing the composite microspheres in a mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol with the mass fraction of 60%, refluxing for 4.5 hours under magnetic stirring, extracting with acetone to remove hexadecyl trimethyl ammonium bromide, washing with ethyl alcohol, filtering, and drying the obtained white sample in a vacuum oven at 70 ℃ for 11 hours to finally obtain hollow porous silicon dioxide microspheres; in the step A, the volume ratio of the cetyl trimethyl ammonium bromide solution, the strong ammonia water, the mixed solution of normal hexane and tetraethyl orthosilicate and the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol is 160: 3: 28: 100, respectively; wherein the volume ratio of the normal hexane to the tetraethyl orthosilicate in the mixed solution of the normal hexane and the tetraethyl orthosilicate is 4-5: 1-1.5; the volume ratio of the concentrated hydrochloric acid to the absolute ethyl alcohol in the mixed solution of the concentrated hydrochloric acid and the absolute ethyl alcohol is 1: 102, and (b); in the step B, the mass ratio of the silicon dioxide microspheres to the hexamethylene diisocyanate to the 3-triethoxysilyl-1-propylamine is 10: 0.4: 0.8;
B. activation of hollow porous silica: dispersing the silicon dioxide microspheres into dimethylformamide, adding hexamethylene diisocyanate, stirring and reacting for 5 hours at 70 ℃, adding 3-triethoxysilyl-1-propylamine, continuously stirring and reacting for 3 hours at 65 ℃, centrifuging, and alternately cleaning with absolute ethyl alcohol and ultrapure water to obtain activated hollow porous silicon dioxide;
C. preparing filling gel liquid: mixing the composite carbon sol and titanium dioxide according to a mass ratio of 60: 1, uniformly mixing to obtain composite sol, aging the composite sol for 28 hours, then performing solvent replacement on the composite sol for 16 hours by using excessive absolute ethyl alcohol, and then removing the absolute ethyl alcohol to obtain filling gel; the preparation method of the composite carbon sol in the step C comprises the following steps: 2-furfural, water-soluble phenolic resin, carbon nano tubes, methyl cellulose, brucite fibers, sodium bicarbonate and water are mixed according to a mass ratio of 7: 1: 0.5: 0.5: 0.05: 0.03: 100, uniformly stirring to obtain a mixed solution, dropwise adding ammonia water with the concentration of 0.75mol/L into the mixed solution at the speed of 15mL/min under the stirring condition, and adjusting the pH value to be neutral; then reacting for 9 hours at 70 ℃ to prepare composite carbon sol;
D. aerogel-filled hollow porous silica: c, adding the activated hollow porous silica microspheres obtained in the step B into the filling gel liquid obtained in the step C, stirring for 4.5 hours to enable the gel liquid to be filled into the filled hollow porous silica microspheres, separating the gel liquid from the hollow porous silica microspheres again, drying the filled hollow porous silica microspheres at 70 ℃ for 25min, then carbonizing at 600 ℃ to obtain carbonized aerogel filled hollow porous silica, and cleaning and drying the carbonized aerogel filled hollow porous silica to obtain a finished product; and D, the carbonization process of the filled mesoporous silica microspheres comprises the following steps: heating the filled mesoporous silica microspheres to 400 ℃ at the speed of 6 ℃/min for pre-carbonization for 35 min; then the temperature is raised to 600 ℃ at the rate of 20 ℃ and carbonized for 55 min.
COMPARATIVE EXAMPLE 1 (omitting two-dimensional DAC refining step)
The difference from the example 1 is that the molecular distillation is combined with the dynamic axial chromatography to prepare the high-purity EPA ethyl ester, and the process steps are as follows:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA crude product to remove ethanol so as to obtain low-purity ethyl ester EPA;
the preparation process comprises the following steps: adding EPA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 50 ℃, refluxing for transesterification reaction for 8h, and concentrating the reaction solution at 50 ℃ under the vacuum degree of 0.095mbar to remove ethanol to obtain low-purity ethyl ester type EPA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the added EPA crude product to the absolute ethanol is 1: 2.5, the sodium hydroxide accounts for 0.2 percent of the weight of the EPA crude product, and the lipase accounts for 1.5 percent of the weight of the EPA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester EPA to obtain a medium-purity ethyl ester EPA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type EPA by using pilot scale short-range molecular distillation equipment to remove low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2mbar, material flow rate of 1kg/h, film scraping speed of 130r/min, material temperature of 31 ℃,The external condensation temperature is 30 ℃, the evaporation temperature is 110 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature;
the second step of molecular distillation process is as follows: decolorizing EPA ethyl ester sample after first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurity, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2Under mbar, the material flow rate is 2kg/h, the film scraping speed is 130r/min, the material temperature is 31 ℃, the external condensation temperature is 30-32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature.
(3) Carrying out third-step molecular distillation on the medium-purity ethyl ester EPA sample to prepare high-purity ethyl ester EPA;
the third step of molecular distillation comprises the following steps: the EPA ethyl ester is obtained by the second step of molecular distillation, the residual solvent is removed by adopting pilot scale short-range molecular distillation equipment, the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10- 2mbar, material flow rate of 2.5kg/h, film scraping rate of 130r/min, material temperature of 31 deg.C, external condensation temperature of 31 deg.C, evaporation temperature of 75 deg.C, and internal condensation temperature 30 deg.C lower than evaporation temperature to obtain high purity ethyl ester EPA with purity of 98% or more.
Comparative example 2 (omitting the second molecular distillation step)
The difference from the example 1 is that the molecular distillation is combined with the dynamic axial chromatography to prepare the high-purity EPA ethyl ester, and the process steps are as follows:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA crude product to remove ethanol so as to obtain low-purity ethyl ester type EPA;
the preparation process comprises the following steps: adding EPA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 50 ℃, refluxing for transesterification reaction for 8 hours, and concentrating reaction liquid at 50 ℃ under the vacuum degree of 0.095mbar to remove ethanol to obtain low-purity ethyl ester type EPA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the added EPA crude product to the absolute ethanol is 1: 2.5, the sodium hydroxide accounts for 0.2 percent of the weight of the EPA crude product, and the lipase accounts for 1.5 percent of the weight of the EPA crude product.
(2) Carrying out first-step molecular distillation on the low-purity ethyl ester EPA to obtain a medium-purity ethyl ester EPA sample; the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type EPA by using pilot scale short-range molecular distillation equipment to remove low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2mbar, material flow rate of 1kg/h, film scraping rate of 130r/min, material temperature of 31 ℃, external condensation temperature of 30 ℃, evaporation temperature of 110 ℃, and internal condensation temperature of 50 ℃ lower than the evaporation temperature, thus obtaining the medium-purity ethyl ester EPA sample with purity more than or equal to 70%.
(3) Sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and third-step molecular distillation on the medium-purity ethyl ester EPA sample to prepare high-purity ethyl ester EPA;
the two-dimensional DAC refining process comprises the following steps: refining a medium-purity ethyl ester EPA sample by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and a particle size of 30 mu m; the sample loading amount accounts for 3% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 50: 15(v/v), the flow rate is 160ml/min, the detection wavelength is 204nm, the EPA ethyl ester fraction is collected, and the mobile phase is removed by adopting the concentration at 50 ℃ and the vacuum degree of 0.095 mbar; the mobile phase alcohol is methanol or ethanol;
the third step of molecular distillation comprises the following steps: axially obtaining refined EPA ethyl ester by two-dimensional DAC refining, and removing residual solvent by using pilot scale short-range molecular distillation equipment, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 x 10-2mbar, material flow rate of 2.5kg/h, film scraping rate of 130r/min, material temperature of 31 deg.C, external condensation temperature of 31 deg.C, evaporation temperature of 75 deg.C, and internal condensation temperature 30 deg.C lower than evaporation temperature to obtain high purity ethyl ester EPA with purity of 98% or more.
Comparative example 3 (different from example 5 in that the volume of the high-performance adsorbent filled in the rectifying column was changed to that of activated carbon equivalent)
Comparative example 4 (difference from example 5 in that the adsorbent is not filled with the composite gel)
The process for preparing the high-purity DHA ethyl ester by combining molecular distillation with dynamic axial chromatography comprises the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type DHA;
the preparation process comprises the following steps: adding a DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 50 ℃, refluxing for transesterification reaction for 8 hours, and concentrating the reaction solution at 50 ℃ by adopting a vacuum degree of 0.095mbar to remove ethanol, thereby obtaining low-purity ethyl ester type DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the mass ratio of the added DHA crude product to the absolute ethanol is 1: 2.5, the sodium hydroxide accounts for 0.2 percent of the mass of the DHA crude product, and the lipase accounts for 1.5 percent of the mass of the DHA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester type DHA to obtain a medium-purity ethyl ester type DHA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type DHA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-2mbar, material flow rate of 1kg/h, film scraping speed of 130r/min, material temperature of 31 deg.C, external condensation temperature of 30 deg.C, evaporation temperature of 110 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature;
the second molecular distillation process comprises the following steps: and (2) decolorizing the DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the highest tolerance temperature is 350 ℃, the vacuum degree is 1 multiplied by 10 < -2 > mbar, the material flow rate is 2kg/h, the film scraping speed is 130r/min, the material temperature is 31 ℃, the external condensation temperature is 30-32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, so that the medium-purity ethyl ester type DHA sample with the purity of more than or equal to 70% is obtained.
(3) Sequentially performing two-dimensional DAC (digital-to-analog converter) refining and rectification on the medium-purity ethyl ester type DHA sample to prepare high-purity ethyl ester type DHA;
the two-dimensional DAC refining process comprises the following steps: refining the ethyl ester type DHA sample with medium purity by using a two-dimensional dynamic axial column DAC80, preparing 8cm ID by 25cm by 2 columns in a dynamic axial manner, and performing reverse silica gel alkyl modification on a filler with the particle size of 10-50 um; the sample loading amount accounts for 0.5-5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0-85: 15(v/v), the flow rate is 120-; the mobile phase alcohol is methanol or ethanol;
the rectification process comprises the following steps: obtaining refined DHA ethyl ester fraction axially through two-dimensional DAC refining, preheating to 52 ℃, then feeding into a rectifying tower for separation, extracting solvent and water from the tower top, and extracting high-purity DHA from the tower kettle; the reflux ratio of the top of the rectifying tower is 1.5, the operating pressure is 0.13Mpa, the temperature of the top of the tower is 50 ℃, and the temperature of the bottom of the tower is 100 ℃.
The method is characterized in that a rectifying tower used in the rectifying process is filled with aerogel filled hollow porous silica adsorbent, and the preparation steps are as follows:
A. preparing hollow porous silicon dioxide: placing 0.15 mass percent of hexadecyl trimethyl ammonium bromide solution into a container, adding 29 mass percent of strong ammonia water into the solution, continuously stirring for 25min, then, dripping a mixture of n-hexane and tetraethyl orthosilicate at a speed of 1.1mL/min, continuously stirring for reacting for 11h after dripping is finished, and after a reaction system gradually turns white; centrifuging, washing with absolute ethyl alcohol, and drying to obtain hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres; ultrasonically dispersing the composite microspheres in a mixed solution of 55 mass percent of concentrated hydrochloric acid and absolute ethyl alcohol, refluxing for 4.5 hours under magnetic stirring, extracting with acetone to remove hexadecyl trimethyl ammonium bromide, washing with ethyl alcohol, filtering, and drying the obtained white sample in a vacuum oven at 70 ℃ for 11 hours to finally obtain hollow porous silicon dioxide microspheres; in the step A, the volume ratio of the cetyl trimethyl ammonium bromide solution, the strong ammonia water, the mixed solution of normal hexane and tetraethyl orthosilicate and the mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol is 150: 4: 26: 105; wherein the volume ratio of the normal hexane to the tetraethyl orthosilicate in the mixed solution of the normal hexane and the tetraethyl orthosilicate is 4.5: 1.2; the volume ratio of the concentrated hydrochloric acid to the absolute ethyl alcohol in the mixed solution of the concentrated hydrochloric acid and the absolute ethyl alcohol is 1: 100; in the step B, the mass ratio of the silicon dioxide microspheres to the hexamethylene diisocyanate to the 3-triethoxysilyl-1-propylamine is 10: 0.3: 1.0;
B. activation of hollow porous silica: dispersing the silicon dioxide microspheres into dimethylformamide, adding hexamethylene diisocyanate, stirring and reacting for 5 hours at 70 ℃, adding 3-triethoxysilyl-1-propylamine, continuously stirring and reacting for 3 hours at 65 ℃, centrifuging, and alternately cleaning with absolute ethyl alcohol and ultrapure water to obtain activated hollow porous silicon dioxide;
comparative example 5 (the difference from example 5 is that the high-efficiency adsorbent filled in the rectifying tower is composite carbonized aerogel)
The process for preparing the high-purity DHA ethyl ester by combining molecular distillation with dynamic axial chromatography comprises the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the DHA crude product to remove ethanol so as to obtain low-purity ethyl ester type DHA;
the preparation process comprises the following steps: adding a DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 50 ℃, refluxing for transesterification reaction for 8 hours, and concentrating the reaction solution at 50 ℃ under the vacuum degree of 0.095mbar to remove ethanol, thereby obtaining low-purity ethyl ester type DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the mass ratio of the added DHA crude product to the absolute ethanol is 1: 2.5, the sodium hydroxide accounts for 0.2 percent of the mass of the DHA crude product, and the lipase accounts for 1.5 percent of the mass of the DHA crude product.
(2) Sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester type DHA to obtain a medium-purity ethyl ester type DHA sample;
the first step of molecular distillation process is as follows: deodorizing and deodorizing low-purity ethyl ester type DHA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, the vacuum degree is 1 x 10 < -2 > mbar, the material flow rate is 1kg/h, the film scraping speed is 130r/min, the material temperature is 31 ℃, the external condensation temperature is 30 ℃, the evaporation temperature is 110 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature;
the second molecular distillation process comprises the following steps: and (2) decolorizing the DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the highest tolerance temperature is 350 ℃, the vacuum degree is 1 multiplied by 10 < -2 > mbar, the material flow rate is 2kg/h, the film scraping speed is 130r/min, the material temperature is 31 ℃, the external condensation temperature is 30-32 ℃, the evaporation temperature is 150 ℃, and the internal condensation temperature is 50 ℃ lower than the evaporation temperature, so that the medium-purity ethyl ester type DHA sample with the purity of more than or equal to 70% is obtained.
(3) Sequentially carrying out two-dimensional DAC (digital-to-analog converter) refining and rectification on the medium-purity ethyl ester type DHA sample to prepare high-purity ethyl ester type DHA;
the two-dimensional DAC refining process comprises the following steps: refining the ethyl ester type DHA sample with medium purity by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 10-50um particle size; the sample loading amount accounts for 0.5-5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0-85: 15(v/v), the flow rate is 120-; the mobile phase alcohol is methanol or ethanol;
the rectification process comprises the following steps: obtaining refined DHA ethyl ester fraction axially through two-dimensional DAC refining, preheating to 52 ℃, then feeding into a rectifying tower for separation, extracting solvent and water from the tower top, and extracting high-purity DHA from the tower kettle; the reflux ratio of the top of the rectifying tower is 1.5, the operating pressure is 0.13Mpa, the temperature of the top of the tower is 50 ℃, and the temperature of the bottom of the tower is 100 ℃.
The distillation column used in the distillation process is filled with composite carbonized aerogel, and the preparation steps are as follows:
A. preparing a filling gel liquid: mixing the composite carbon sol and titanium dioxide according to the mass ratio of 50: 2, uniformly mixing to obtain composite sol, aging the composite sol for 28 hours, then performing solvent replacement on the composite sol for 14 hours by using excessive absolute ethyl alcohol, and then removing the absolute ethyl alcohol to obtain filling gel; the preparation method of the composite carbon sol in the step C comprises the following steps: mixing 2-furaldehyde, water-soluble phenolic resin, carbon nano tubes, methyl cellulose, brucite fibers, sodium bicarbonate and water according to a mass ratio of 6: 1: 0.6: 0.4: 0.06: 0.02: 100, uniformly stirring to obtain a mixed solution, dropwise adding 0.5mol/L ammonia water into the mixed solution at the speed of 15mL/min under the stirring condition, and adjusting the pH value to be neutral; then reacting for 9 hours at 70 ℃ to prepare composite carbon sol;
B. carbonizing the aerogel: preparing adsorption microspheres from the composite carbon sol gel, drying the adsorption microspheres at 70 ℃ for 25min, carbonizing the adsorption microspheres at 450 ℃ to obtain carbonized aerogel, and cleaning and drying the carbonized aerogel to obtain a finished product; the carbonization process of the adsorption microspheres comprises the following steps: heating the adsorption microspheres to 400 ℃ at the speed of 8 ℃/min for pre-carbonization for 35 min; then the temperature is raised to 550 ℃ at the rate of 20 ℃ and carbonized for 55 min.
The indexes of relevant performance evaluation parameters of the processes for preparing high-purity EPA or DHA ethyl ester according to examples 1-7 and comparative examples 1-5 are shown in Table 1.
Table 1 shows the performance evaluation indexes of the items related to the process for preparing high-purity EPA or DHA ethyl ester
Figure BDA0002598730500000211
And (4) conclusion: the preparation process for preparing high-purity EPA or DHA ethyl ester with good impurity removal effect can be prepared only when the components and component contents added in the embodiments 1-7 are within the scope of the invention, and the preparation process has the advantages of high conversion efficiency, low energy consumption of reaction equipment and short reaction period.
The difference between the comparative example 1 and the example 1 is that a two-dimensional DAC refining step is omitted, fatty acids with similar molecular weights or similar boiling points can be separated and purified through polarity intensity in the two-dimensional DAC refining process, and if the step is omitted, the purity of the finally obtained product is greatly reduced.
Comparative example 2 differs from example 1 in that the second molecular distillation step is omitted; the product flows along the heating plate and is heated by the process steps and parameters of the step, when the high-boiling-point heavy molecular components of the sample hardly escape from the liquid surface and enter a gas phase, the high-boiling-point pigment in the sample is mainly long-carbon-chain saturated fatty acid, so that the pigment is discharged along the mixed liquid, the decoloration effect is realized, the purity of the prepared product is improved, and if the step is omitted, the purity and the recovery rate of the finally obtained product are greatly reduced.
Comparative example 3 is different from example 5 in that the high performance adsorbent filled in the rectifying tower was changed to activated carbon of the same volume; the adsorption pores of the activated carbon are in the shape of holes, and the adsorption capacity of the activated carbon to a target product is higher than that of the high-efficiency adsorbent in the invention, so that the recovery rate of a finally prepared reaction product is reduced.
Comparative example 4 differs from example 5 in that the composite gel is not filled; due to the hollow porous structure and the hollow structure inside the hollow porous silica shell, the specific surface area is increased, and meanwhile, a wide channel is provided for the fluid to pass through, when the hollow porous silica shell is filled in a rectifying tower for purifying gas or liquid, the hollow porous silica shell can easily penetrate through the inside of the hollow porous silica microspheres, so that the purification is insufficient, the residual solvent is used for recording moisture, and the product purity is reduced.
The difference between the comparative example 5 and the example 5 is that the high-efficiency adsorbent filled in the rectifying tower is composite carbonized aerogel; the form of compound carbomorphism aerogel can be harmd because the extrusion to compound carbomorphism aerogel at the in-process that the molecular sieve was filled, especially after adsorbing moisture and impurity, can make the structural properties variation of compound carbomorphism aerogel, the wall around the hole easily softens under the mutual extruded effect of external force and collapses for the hole blocks up the destruction, reduces the adsorption capacity of compound carbomorphism aerogel, and the adsorption performance variation of adsorbent.
FIG. 1 is a schematic diagram of the reaction scheme of the present invention, which specifies the specific preparation steps and preparation processes of the present invention; FIG. 2 is a gas chromatogram of DHA ethyl ester with purity greater than 76% in two-step molecular distillation; FIG. 3 is a gas chromatogram of EPA ethyl ester with purity of more than 78% in two-step molecular distillation; FIG. 4.1 shows that DHA ethyl ester pigment obtained by two-step molecular distillation is black brown and viscous, and FIG. 4.2 shows that DHA ethyl ester obtained by two-step molecular distillation and decolorization is light yellow and clear; FIG. 5 is a gas chromatogram of high-purity DHA ethyl ester after residual solvent is removed by two-dimensional DAC refining and pilot-scale short-range molecular distillation equipment, wherein the purity of the DHA ethyl ester is as high as 99.2%; FIG. 6 is a gas chromatogram of high-purity EPA ethyl ester after removal of residual solvent by two-dimensional DAC refining and pilot-scale short-range molecular distillation equipment, wherein the EPA ethyl ester purity is as high as 98.4%; FIG. 7 is a gas chromatogram of high-purity DHA ethyl ester after residual solvent removal by two-dimensional DAC refining and pilot-scale short-range molecular distillation equipment, wherein the purity of the DHA ethyl ester is as high as 99.5%; FIG. 8 is a gas chromatogram of high-purity EPA ethyl ester after removal of residual solvent by two-dimensional DAC refining and pilot-scale short-range molecular distillation equipment, wherein the EPA ethyl ester purity is as high as 99.6%.
The elements and equipment used in the invention are common elements and equipment in the field unless otherwise specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.

Claims (7)

1. The process for preparing high-purity EPA ethyl ester or DHA ethyl ester by combining molecular distillation with dynamic axial chromatography is characterized by comprising the following process steps:
(1) carrying out enzyme-base combined ultrasonic transesterification and concentration on the EPA or DHA crude product to remove ethanol, thus obtaining low-purity ethyl ester type EPA or DHA;
(2) sequentially carrying out first-step molecular distillation and second-step molecular distillation on the low-purity ethyl ester EPA or DHA to obtain a medium-purity ethyl ester EPA or DHA sample;
(3) sequentially carrying out two-dimensional dynamic axial column DAC (digital-to-analog converter) refining and rectification on the medium-purity ethyl ester type EPA or DHA sample to prepare high-purity ethyl ester type EPA or DHA;
the method is characterized in that a rectifying tower used in the rectifying process is filled with aerogel filled hollow porous silica adsorbent, and the preparation steps are as follows:
A. preparing hollow porous silica: placing 0.1-0.2% by mass of hexadecyl trimethyl ammonium bromide solution into a container, adding 28-30wt% by mass of concentrated ammonia water into the solution, continuously stirring for 20-30min, then dripping a mixture of n-hexane and tetraethyl orthosilicate at the speed of 1.0-1.2mL/min, after dripping, continuously stirring for reacting for 10-12h, and after the reaction system gradually turns white; centrifuging, washing with absolute ethyl alcohol, and drying to obtain hexadecyl trimethyl ammonium bromide-silicon dioxide composite microspheres; ultrasonically dispersing the composite microspheres in a mixed solution of concentrated hydrochloric acid and absolute ethyl alcohol with the mass fraction of 50-60%, refluxing for 4-5h under magnetic stirring, extracting with acetone to remove hexadecyl trimethyl ammonium bromide, washing with ethyl alcohol, filtering, and drying the obtained white sample in a vacuum oven at the temperature of 60-80 ℃ for 10-12h to finally obtain hollow porous silicon dioxide microspheres;
B. activating hollow porous silica: dispersing the silicon dioxide microspheres into dimethylformamide, adding hexamethylene diisocyanate, stirring and reacting for 4-6h at 60-80 ℃, adding 3-triethoxysilyl-1-propylamine, continuously stirring and reacting for 2-4h at 60-70 ℃, centrifuging, and alternately cleaning with absolute ethyl alcohol and ultrapure water to obtain activated hollow porous silicon dioxide;
C. preparing filling gel liquid: mixing the composite carbon sol and titanium dioxide according to the mass ratio of 40-60: 1-3 to obtain composite sol, aging the composite sol for 20-36h, then carrying out solvent replacement on the composite sol for 12-16h by using excessive absolute ethyl alcohol, and then removing the absolute ethyl alcohol to obtain filling gel; the preparation method of the composite carbon sol comprises the following steps: 2-furfural, water-soluble phenolic resin, carbon nano tubes, methyl cellulose, brucite fibers, sodium bicarbonate and water are mixed according to the mass ratio of 5-7: 1: 0.5-0.7: 0.3-0.5: 0.05-0.08: 0.01-0.03: 100, uniformly stirring to obtain a mixed solution, dropwise adding ammonia water with the concentration of 0.25-0.75mol/L into the mixed solution at the speed of 10-20mL/min under the stirring condition, and adjusting the pH value to be neutral; then reacting for 8-10h at 65-75 ℃ to prepare composite carbon sol; and D, the carbonization process of the filled hollow porous silica microspheres comprises the following steps: heating the filled hollow porous silica microspheres to 300-500 ℃ at the speed of 6-10 ℃/min for pre-carbonization for 30-40 min; then heating to 500-600 ℃ at the rate of 18-22 ℃ and carbonizing for 50-60 min;
D. aerogel-filled hollow porous silica: and C, adding the hollow porous silica microspheres activated in the step B into the filling gel liquid prepared in the step C, stirring for 4-5 hours to enable the gel liquid to be filled into the filled hollow porous silica microspheres, separating the gel liquid from the hollow porous silica microspheres again, drying the filled hollow porous silica microspheres at 60-80 ℃ for 20-30min, carbonizing at 300-600 ℃ to obtain carbonized aerogel filled hollow porous silica, and cleaning and drying the carbonized aerogel filled hollow porous silica to obtain a finished product.
2. The process for preparing high-purity EPA ethyl ester or DHA ethyl ester by combining molecular distillation and dynamic axial chromatography according to claim 1, wherein the preparation process in step (1) is as follows: adding EPA or DHA crude product into a reaction kettle equipped with an ultrasonic generator, adding alkaline ethanol and lipase, ultrasonically heating to 40-60 ℃, refluxing for transesterification reaction for 4-10h, and concentrating the reaction solution at 48-52 ℃ under the vacuum degree of 0.09-0.1mbar to remove ethanol to obtain low-purity ethyl ester type EPA or DHA; the substrate alkaline ethanol is a mixture of absolute ethanol and sodium hydroxide, and the weight ratio of the EPA or DHA crude product to the absolute ethanol is 1: 1-4, sodium hydroxide accounts for 0.05-0.3% of the weight of the EPA or DHA crude product, and lipase accounts for 0.5-3% of the weight of the EPA or DHA crude product.
3. The process for preparing high-purity EPA ethyl ester or DHA ethyl ester by combining molecular distillation and dynamic axial chromatography according to claim 1, wherein the first molecular distillation process in the step (2) is as follows: deodorizing and deodorizing low-purity ethyl ester type EPA or DHA by adopting pilot scale short-range molecular distillation equipment, removing low-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3 mbar-1×10-1 mbar, material flow rate of 0.5-1.5kg/h, film scraping speed of 100-160r/min, material temperature of 30-32 deg.C, external condensation temperature of 30-32 deg.C, evaporation temperature of 90-130 deg.C, and internal condensation temperature 50 deg.C lower than evaporation temperature.
4. The process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation and dynamic axial chromatography according to claim 1, wherein the second molecular distillation process in step (2) is as follows: decolorizing the EPA ethyl ester or DHA ethyl ester sample subjected to the first-step molecular distillation by adopting pilot-scale short-range molecular distillation equipment to remove high-boiling-point fatty acid impurities, wherein the evaporation area of the equipment is 0.1 square meter, the maximum tolerant temperature is 350 ℃, and the vacuum degree is 1 multiplied by 10-3 mbar-1×10-1 At mbar, the material flow rate is 1.0-3.0kg/h, and the film scraping speed is100-160r/min, material temperature 30-32 ℃, external condensation temperature 30-32 ℃, evaporation temperature 130-180 ℃, and internal condensation temperature 50 ℃ lower than evaporation temperature.
5. The process for preparing high-purity EPA ethyl ester or DHA ethyl ester by combining molecular distillation and dynamic axial chromatography according to claim 1, wherein the two-dimensional DAC refining process in the step (3) is as follows: refining a medium-purity ethyl ester type EPA or DHA sample by using a two-dimensional dynamic axial column DAC80, dynamically and axially preparing 8cm ID 25cm 2 columns, reverse silica gel alkyl modified filler and 10-50um particle size; the sample loading amount accounts for 0.5-5% of the modified filler, and the ratio of the mobile phase alcohol to the water is 100: 0-85: 15 v/v, flow rate of 120ml/min and detection wavelength of 204nm, collecting EPA ethyl ester or DHA ethyl ester fraction, and removing mobile phase by concentration at 48-52 ℃ and vacuum degree of 0.09-0.1mbar to obtain a medium-purity ethyl ester type EPA or DHA sample with purity of more than or equal to 70%; the mobile phase alcohol is methanol or ethanol.
6. The process for preparing high-purity EPA or DHA ethyl ester by combining molecular distillation and dynamic axial chromatography according to claim 1, wherein the rectification process in step (3) is as follows: refining by two-dimensional DAC to obtain refined DHA/EPA ethyl ester fraction, preheating to 50-54 deg.C, feeding into a rectifying tower for separation, collecting solvent and water at the tower top, and collecting high-purity EPA ethyl ester or DHA ethyl ester at the tower bottom; the reflux ratio of the top of the rectifying tower is 0.5-2.5, the operating pressure is 0.12-0.14MPa, the temperature of the top of the tower is 40-60 ℃, and the temperature of the bottom of the tower is 90-110 ℃.
7. The process for preparing high-purity EPA ethyl ester or DHA ethyl ester by combining molecular distillation and dynamic axial chromatography according to claim 1, wherein the volume ratio of the cetyl trimethyl ammonium bromide solution, the strong ammonia water, the mixed solution of n-hexane and tetraethyl orthosilicate and the mixed solution of concentrated hydrochloric acid and absolute ethanol in step A is 140-160: 3-5: 24-28: 100-110; wherein the volume ratio of the normal hexane to the tetraethyl orthosilicate in the mixed solution of the normal hexane and the tetraethyl orthosilicate is 4-5: 1-1.5; the volume ratio of the concentrated hydrochloric acid to the absolute ethyl alcohol in the mixed solution of the concentrated hydrochloric acid and the absolute ethyl alcohol is 1: 98-102; in the step B, the mass ratio of the silicon dioxide microspheres to the hexamethylene diisocyanate to the 3-triethoxysilyl-1-propylamine is 10: 0.2-0.4: 0.8-1.2.
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