CN114773421A

CN114773421A - Novel process for extracting high-purity phytosterol by utilizing biological polar resin and continuous counter-current liquid-solid extraction

Info

Publication number: CN114773421A
Application number: CN202210579668.0A
Authority: CN
Inventors: 王立; 金铁栓
Original assignee: Cangzhou Baolai Jinkang Biotechnology Co ltd
Current assignee: Cangzhou Baolai Jinkang Biotechnology Co ltd
Priority date: 2022-05-25
Filing date: 2022-05-25
Publication date: 2022-07-22
Anticipated expiration: 2042-05-25
Also published as: CN114773421B

Abstract

The invention describes a new process for extracting phytosterol from deodorized distillate (DD oil) of vegetable oil. The process comprises the steps of firstly, carrying out esterification reaction on methanol and free fatty acid under the catalysis of a biological positive resin to generate fatty acid methyl ester, then carrying out transesterification reaction on the methanol and triglyceride in the DD oil through the catalysis of the negative resin by the DD oil, converting the triglyceride into the fatty acid methyl ester, and separating crude sterol from mother liquor (crude methyl ester) through freezing fractionation after the esterification reaction is finished. And finally, separating high-purity phytosterol by utilizing a multistage continuous countercurrent liquid-solid extraction method.

Description

Novel process for extracting high-purity phytosterol by utilizing biological polar resin and continuous countercurrent liquid-solid extraction

Technical Field

The invention discloses a new process for extracting high-purity phytosterol by using deodorized distillate (DD for short) in vegetable oil refining as a raw material and utilizing a biological polar resin, belonging to the technology for separating grease compounds and purifying trace functional components in the grease compounds.

Background

The Deodorized Distillate (DD) in vegetable oil refining is an effective resource for extracting natural substances such as phytosterol. The sterol obtained by extracting plant with DD oil is a mixture of several sterols, and its main components are beta-sitosterol, stigmasterol, campesterol and brassicasterol. It has high nutritive value and high physiological activity, and can inhibit the absorption of cholesterol by human body in intestinal tract, promote the degradation and metabolism of cholesterol and inhibit the biochemical synthesis of cholesterol in liver, so that it is suitable for treating high cholesterol, hyperlipemia and other diseases. The phytosterol also has good antioxidant effect, and can be used as food additive (antioxidant and nutritional additive), and animal growth promoter material for promoting animal growth and promoting animal health. The phytosterol is also used for preventing and treating heart diseases of coronary atherosclerosis, and has obvious curative effects on ulcer, skin squamous carcinoma, cervical cancer and the like. Meanwhile, the product has wide application in the fields of medicine, cosmetics, paper processing, printing, textile, food and the like. Species range and requirements in the 3. 2010 bulletin of the ministry of health and planning committee of the people's republic of china, identified phytosterols as a new resource food. In addition, sterol is widely used for replacing diosgenin in the production process for fermentation pharmacy, is a pharmaceutical raw material, and meanwhile, phytosterol is an important production raw material of steroidal drugs and vitamin D3. Steroid drugs are a large variety of drugs with wide clinical application, are used for treating rheumatism, cardiovascular diseases, lymphatic leukemia, tumors, bacterial encephalitis, skin diseases, endocrine dyscrasia, senile diseases and the like, and are combined with antibiotics and the like to be one of the most extensive drug varieties in the treatment field and the largest drug variety in the market. In asia, china and india are the major producers of steroid ring drugs. Since the nineties, the sales of international market steroid ring drugs have increased at a rate of 10% to 15% every year, and have remained a rapid trend. With the enlargement of the fermentation scale of steroid drug intermediates, the demand of sterols is increasing day by day.

The traditional process for producing phytosterol is that DD oil is firstly catalyzed by concentrated sulfuric acid to carry out methyl esterification reaction with methanol, and water produced and redundant methanol and concentrated sulfuric acid are washed away after the reaction is finished. After vacuum dehydration, triglyceride is converted into fatty acid and glycerol under the catalysis of strong sodium hydroxide reduction, and the phytosterol is obtained through a series of processes.

Patent No. CN201710324735.3 "method for extracting refined phytosterol from deodorized distillate", this invention discloses a method for extracting refined phytosterol from deodorized distillate, it adopts a small amount of low-solubility alkali liquor to carry on pretreatment and remove impurity, then adds low proportion methanol under the condition of low temperature, carries on esterification reaction with biological enzyme method, obtains crude sterol after growing crystal to mother liquor, then passes many times rinsing, and grows crystal again, obtains refined sterol after filtering. The process is characterized in that a method of saponification and esterification is adopted, and the biological enzyme is used as a catalyst in the esterification process, so that the method has the defects of high processing cost, long reaction time and low production efficiency because the biological enzyme cannot be recovered.

Patent No. CN200910067652.6 "a method for extracting natural phytosterol from residue of deodorized distillate of vegetable oil" this invention describes a method for extracting natural phytosterol from residue of deodorized distillate of vegetable oil, which adopts catalytic decomposition to convert sterol ester and glyceride in residue into free sterol and fatty acid, then separates out natural phytosterol by cold separation and filtration, and a large amount of fatty acid contained in filtrate can still be used for preparing surfactant or biodiesel. The invention has the disadvantage that the method is only limited to a method for extracting the phytosterol by using the residual vegetable oil as the raw material.

Patent No. CN201710723449.4, a method for extracting phytosterol from plant oil deodorized distillate, the invention mainly comprises the steps of adding the plant oil deodorized distillate, alcohol and solid super acid in a mass ratio of 100:30:5 into a reaction kettle, and stirring and reacting for 4 hours at 75 ℃; filtering after the reaction is finished, and taking filtrate; transferring the filtrate obtained in the second step into a cold separation tower, cooling and cold separation crystallization is carried out at a gradient of 1 ℃/h, and heat is preserved for 48h when the temperature is reduced to 10 ℃; fourthly, performing filter pressing on the mixed liquid obtained after the step three of cold separation and crystallization to obtain a crude phytosterol product; fifthly, dissolving the crude plant sterol product obtained in the step four in an organic solvent with the weight 5 times that of the crude plant sterol product, heating to dissolve the crude plant sterol product fully, cooling to perform cold crystallization at the gradient of 1 ℃/h, keeping the temperature for 48h when the temperature is reduced to 10 ℃, performing pressure filtration and drying to obtain the plant sterol.

Patent No. CN201310132738.9, a method for extracting phytosterol from biodiesel residual oil, the invention discloses a method for extracting phytosterol from biodiesel residual oil, which comprises the steps of firstly, adding biodiesel residual oil and sodium methoxide aqueous solution into a reaction kettle for alcoholysis reaction; secondly, adding fatty acid methyl ester and concentrated sulfuric acid into the reaction kettle after the alcoholysis reaction to perform esterification reaction; thirdly, washing the materials after the esterification reaction with hot water of 60-80 ℃ to be neutral, and then filtering the materials while the materials are hot to obtain filtrate; fourthly, carrying out four-stage molecular distillation on the filtrate; fifthly, mixing the third distillation fraction and the fourth distillation fraction of the four-stage molecular distillation, adding fatty acid methyl ester into the mixed fraction, heating until the sterol is completely dissolved, performing condensation, and performing filter pressing to obtain crude sterol; sixthly, washing the crude sterol by using alcohol, and drying to obtain the refined phytosterol. The process of the invention adopts biodiesel residual oil as a raw material, and molecular distillation equipment is required to remove impurities in sterol, so as to further ensure the sterol purity.

The invention relates to a method for extracting and purifying phytosterol from corn stigma, which comprises the following steps of 1) adding 1g of pulverized and dried corn stigma into 2-6ml of saponification liquid, saponifying for 2-4 hours at 85 +/-10 ℃, then adding absolute ethyl alcohol, performing ultrasonic extraction for 0.5-1 hour, centrifuging after the ultrasonic extraction is finished, and taking supernatant to perform rotary evaporation to obtain a crude extract; the saponification liquid is a potassium hydroxide ethanol solution with the concentration of 2-5 mol/L; 2) extracting the crude extract with solvent, recrystallizing with ethyl acetate to obtain the final product

Patent No. CN201911062053.5, a method for extracting phytosterol from cottonseed acidified oil, the invention comprises (1) pre-treating, filtering raw oil to remove impurities, dehydrating, heating, mixing with phosphoric acid and water, passing through a reactor, and drying to obtain degummed oil; (2) distilling fatty acid, heating acidified oil, degassing, feeding into a main distillation tower, and distilling residue in a residue distillation tower; (3) performing distillation light phase esterification, namely mixing the molecular distillation light phase with methanol for esterification reaction, and mixing the molecular distillation light phase with the methanol for secondary esterification reaction to obtain an esterified liquid with an acid value lower than 8; (4) adding the esterified solution into a cold separation kettle, and performing primary cooling, deep cooling, crystal growing and filtering to obtain a crude sterol filter cake; (5) mixing and heating the crude sterol filter cake and ethanol, filtering impurities, carrying out primary cooling, carrying out deep cooling, stopping stirring, growing crystals to obtain phytosterol, crushing, and sieving to obtain finished sterol.

The invention relates to a method for producing phytosterol by microbial fermentation of deodorized distillate of vegetable fat, which is characterized in that the deodorized distillate of vegetable fat is fermented by microorganisms, free fatty acid in the deodorized distillate is directly metabolized and utilized as nutrient substances of the microorganisms, glyceride in the deodorized distillate is hydrolyzed into small molecular substances under the action of hydrolytic enzymes such as lipase, esterase and the like generated by the microorganisms, and then the small molecular substances are absorbed and utilized by microbial cells and converted into cell substances; because the phytosterol is insoluble in water, the phytosterol can be separated out by cold separation after the filtrate is concentrated. The microbial fermentation method is only suitable for producing the phytosterol with low content of 5-30%, has long processing time and is difficult to industrially produce.

The invention discloses a method for producing a mixture of plant sterol and vitamin E, which comprises the steps of taking an oil deodorized distillate as a raw material, preheating the deodorized distillate at the temperature of 200-240 ℃ under the vacuum of 13-600 Pa, removing most of free fatty acids, further purifying under the vacuum of 1-100 Pa at the temperature of 120-200 ℃, reducing the acid value to less than 0.1, and decolorizing and refining a semi-finished product. The process can only refine to obtain a mixed concentrated solution containing 10-40% of sterol and 10-30% of vitamin E. The method is far from the quality standard of the national sterol and the purity of the sterol outlet.

Patent numbers: CN201010104339.8 method for extracting natural vitamin E and phytosterol in full-continuous manner invented by Tianjin bioengineering (Tianjin) Co., Ltd

The method comprises (1) filtering off impurities from deodorized distillate of vegetable oil, and drying; (2) fully mixing the material treated in the step (1) with low-carbon monohydric alcohol, heating, and passing through a resin column; (3) removing low-carbon monohydric alcohol and water under reduced pressure; (4) mixing the material obtained in the step (3) with low-carbon monohydric alcohol containing alkali, heating, and continuously feeding into a reaction kettle to convert neutral oil into fatty acid ester; (5) adding acid for neutralization; (6) washing with water to neutrality; (7) crystallizing, filtering and separating to obtain solid-phase crude phytosterol and a liquid phase; the liquid phase is separated by molecular distillation to separate the fatty acid esters and the natural vitamin E. The process uses strong acid neutralization, strong base ester exchange reaction and multiple water washing. The waste water and the waste residue are effectively generated, and the environment is influenced to a certain extent.

Patent numbers: CN 201410445798A Phytosterol fatty acid ester and its catalytic synthesis method, the raw materials of the invention are phytosterol ester and fatty acid ester and its catalytic synthesis method, the method comprises the steps of catalyst preparation, reactant dissolution, catalytic reaction, evaporation and distillation, etc., the total sterol content in the finished product of the invention is not less than 59%, the acid value is less than 1.0mgKOH/g, the peroxide value is less than or equal to 5meq/kg, the color is yellow less than or equal to 15, and the red color is less than or equal to 1.5. Such indexes are difficult to reach the standard of the national standard purity requirement of more than 95.

Patent No. CN201010253358.7 "A method for preparing phytosterol ester", the invention adds phytosterol and fatty acid into a three-neck flask with a reflux condensing device, adds catalyst and water-carrying agent, and passes through nitrogen as protective gas to react for 8-72 hours at 80-120 ℃ to synthesize high-purity phytosterol ester (the purity is over 90%). The process is a process for synthesizing sterol ester from sterol.

The research on the various processes discovers that: the method has various characteristics, and has obvious advantages in the aspects of raw material source, processing environmental protection, catalyst cost, production efficiency and product quality.

Disclosure of Invention

The invention provides a new process for extracting phytosterol by using a biological polar resin by taking deodorized distillate (DD oil) in the refining process of vegetable oil as a raw material.

The vegetable oil of the invention mainly refers to deodorized distillate (DD oil) of rice bran oil, corn germ oil, peanut oil, sunflower seed oil and soybean oil, the technical process is that the DD oil and low alcohol are mixed by using a biological polar resin as a catalyst, the DD oil and the low alcohol respectively pass through a solidification bed respectively made of strong acid biological polar resin and strong polarity reducing resin twice, under the action of proper temperature and flow rate, the mixed oil and the low alcohol respectively undergo esterification and ester exchange reaction, and meanwhile, a small amount of phytosterol ester in the raw material is converted into free sterol. And then carrying out cold separation on the esterification mother liquor obtained by the reaction, and then continuously refining the high-purity phytosterol by using a multistage counter-current solid-liquid extraction device. The specific process content is as follows:

1. esterification reaction: adding low-carbon alcohol with the mole number being 12-20 times that of free fatty acid into deodorized distillate (DD oil) of vegetable oil, wherein the low-carbon alcohol is methanol or ethanol, and reacting for 2-4 hours at 40-55 ℃ by using a curing bed with the model of strong cation exchange resin C-25S as a base; the fatty acid in the raw oil and the low alcohol are subjected to esterification reaction to generate fatty acid methyl ester, and the acid value in the DD oil is qualified when the acid value is less than 3.0 mgKOH/g;

2. vacuum desolventizing and drying: after the step (1), carrying out vacuum desolventizing dehydration on the raw oil, wherein the vacuum degree is 20-80 mbar, the temperature is 80-100 ℃, and the water content is measured to be less than 0.005, and the raw oil is qualified:

3. ester exchange reaction: after the steps (1) and (2), supplementing 12-20 times of mol number of methanol or ethanol solution to qualified raw oil generated in the step (2), uniformly stirring, feeding the raw oil into a fluidized bed based on Ambersep900OH strong-base anion exchange resin, adjusting the pH value of the raw oil to 7-7.5 by using trace methanol alkali before the raw oil is subjected to reaction for 3-5 hours at 40-45 ℃ reflux temperature, performing ester exchange reaction on triglyceride and low alcohol in the raw oil to generate fatty acid methyl ester, measuring the content of sterol ester in the raw oil after the step (3) is finished, and proving that the sterol ester in the (DD oil) is converted into free sterol, so that the yield and yield of total sterol are improved, and then repeating the step (2) to remove excess methanol, wherein the treated raw oil is collectively called qualified mother liquor;

4. freezing and fractionation: transferring the qualified mother liquor treated in the steps (1), (2) and (3) into a special cold separation kettle, cooling at a cooling rate of 1 ℃ per hour under the condition of stirring speed of 5-10 revolutions per minute from the temperature of 40-45 ℃, starting to separate out solid sterol when the temperature of the qualified mother liquor is reduced to 25-30 ℃, and then continuously cooling at a cooling rate of 0.5-0.8 ℃ per hour by reducing the stirring speed to 3-6 revolutions per minute. When the temperature is reduced to 2-4 ℃, all the solid phase sterol is folded, and the solid plant matter is crude phytosterol with low content:

5. multistage countercurrent liquid-solid extraction: freezing and separating the low-content crude sterol in the step (3), and treating by using a special multistage countercurrent liquid-solid extraction device; dissolving the phase solvent of the extract into n-hexane, petroleum or ethanol; solid phase is low-content crude sterol, and the mass (g) of the solid phase is as follows: liquid phase solvent volume (ml): the liquid-solid volume ratio is 1: 15-25;

6. solid phase desolventizing: removing the solvent from the extraction solid phase in the step (4) through reduced pressure distillation, and obtaining a concentrated phytosterol product if the drying weight loss is less than 0.003;

7. and (3) recovering a liquid residual phase: and (4) carrying out cold precipitation on the raffinate phase in the step (4) at (-20 to-10 ℃) for 20-24 hours under certain conditions, and separating steroids. And then the raffinate is recycled by a decompression recovery tower to obtain a qualified liquid phase solvent, and the water content is less than 0.002, so that the raffinate is qualified.

Drawings

FIG. 1: the process route adopted by the invention is shown.

DD oil → esterification of strong alcoholic resin → cold separation of strong alkaline resin → crude sterol separation by cold separation → continuous reverse flow extraction of sterol → exsolution drying → 95 sterol

Detailed Description

Example 1

The soybean oil after dehydration and deslagging is used for deodorizing distillate 300g, the acid value is 180, and the total phytosterol is 9.5%. Wherein, the sterol ester accounts for 1.5 percent; 8% of free sterol; the content of brassicasterol is 4%, the content of campesterol is 24%, the content of stigmasterol is 25%, and the content of B-sitosterol is 47%.

The operation steps are as follows:

(1) 300g of pure raw materials are added into a flask with a condensing tube, 6000ml of methanol is added, the mixture is stirred and heated to 45 ℃, and a liquid separation bottle is used for titrating the mixture into a solidified bed resin column which takes strong cation exchange resin C-25S as a base. Detecting the acid value of the resin column effluent, wherein the qualified mother liquor is obtained when the acid value is less than 3.0 mgKOH/g; when the effluent is not qualified, the effluent is titrated to the upper port of the resin column by a liquid separation bottle until the effluent at the lower part is completely qualified;

(2) after the reaction is finished, the sample is transferred into an intermittent distillation device to be desolventized and dehydrated by a 2X-4A vacuum pump, the vacuum degree is 60mbar, the temperature is 100 ℃, and the moisture content is measured to be less than 0.005 percent after 1 hour and is qualified: at this point, the pH was measured to be 6, the total sterol content was measured to be 9.4%, and 315g of monomethyl esterified product was weighed out, giving an oil yield of 315/300-105%.

(3) Adding methyl ester sample into flask with condenser tube, adding 6000ml methanol, stirring and heating to 45 deg.C, adjusting pH to 7-7.5 with trace amount of sodium methoxide, and titrating with liquid separation bottle into upper port of resin column of solidified bed based on Ambersep900 strong base anion exchange resin 900 OH. Sampling from the lower port of the resin column, the end of the process was found to be 0.2% sterol ester in the mother liquor, and the pH was found to be 7.5.

(4) After the reaction is finished, transferring the sample into an intermittent distillation device, desolventizing and dehydrating by using a 2X-4A vacuum pump, wherein the vacuum degree is 60mbar, the temperature is 100 ℃, and the drying weight loss is measured to be less than 0.005 after 1 hour, and the sample is qualified: at this time, the pH value was measured to be 7, the total sterol content in the mother liquor was measured to be 9.4%, 295g of secondary methyl esterification sample was weighed, and the oil yield was 295/300-98.3%.

(5) Transferring the secondary esterification mother liquor into a beaker, sealing the opening with a plastic mold, putting the beaker into a temperature-controllable refrigerator, cooling the temperature at a cooling rate of 1 ℃ per hour from 40-45 ℃, and keeping the temperature of the qualified mother liquor for 24 hours until the temperature of the qualified mother liquor is reduced to 2-4 ℃ until all solid-phase sterol is separated out;

(6) vacuum-filtering twice with Buchner funnel, qualitative filter paper and 2X-4A vacuum pump to obtain crude sterol 45g, mother liquor 248g, and measuring crude sterol 45g content to be 59.8%; the total sterol content in the mother liquor is 0.1%. The crude sterol yield at this time is 94.42%;

(7) transferring 45g of the crude sterol sample to a multistage countercurrent liquid-solid extraction device, and slowly adding 900g of 99.8% ethanol extract; after extraction, discharging a mixture of ethanol and solid sterol from a lower outlet of the multistage counter-current liquid-solid extraction device, and then performing desolventizing and drying treatment on the mixture until the drying weight loss is less than 0.002; weighing to obtain 27g of fine sterol, wherein the total content is 98 percent: the content of brassicasterol is 4%, the content of campesterol is 24%, the content of stigmasterol is 25%, and the content of B-sitosterol is 47%. The total sterol yield was 27 × 98%/9.5% × 300 ═ 92.85%; the content purification is higher than 3 percent of the traditional process, and the yield is higher than 9 percent of the traditional process; and the percentage of the grouped parts is unchanged.

Example 2

300g of dehydrated and deslagged corn deodorizer distillate DD oil, 190 of acid value and 5.5 percent of total phytosterol. Wherein, the sterol ester accounts for 0.7%; 4.8 percent of free sterol; the content of brassicasterol is 0%, the content of campesterol is 30%, the content of stigmasterol is 10%, and the content of B-sitosterol is 60%.

The operation steps are as follows:

(1) 300g of the pure raw materials are added into a flask with a condenser tube, 6000ml of methanol is added, the mixture is stirred and heated to 45 ℃, and a liquid separation bottle is used for titrating the mixture and adding the mixture into a cationic resin column. Detecting the acid value of the resin column effluent, wherein the acid value is less than 1.5.0 mgKOH/g;

(2) when the reaction is finished, the sample is transferred, distilled, desolventized and dehydrated, and the water content is measured to be 0.003: measuring the pH value to be 6, measuring the total sterol content to be 50%, weighing to obtain 310g of monomethyl esterification sample, wherein the oil yield is 103%;

(3) putting the grease into a flask with a condensing tube, adding 6000ml of methanol, stirring and heating to 45 ℃, dripping 4-point sodium methoxide by using a burette, and measuring the PH value to be 7.5; then, the mouth of the curing bed is titrated by a liquid separation bottle. The mother liquor was sampled at the lower port of the resin column to determine that the sterol ester content in the mother liquor was 0.1%, and the pH was 7.5.

(4) When the dehydration was completed by vacuum desolventization, the loss on drying was measured after 1 hour to be 0.003: the pH value is measured to be 7, the total sterol content in the mother liquor is measured to be 5.4%, 290g of secondary methyl esterification samples are obtained by weighing, and the oil yield is 96.6%.

(5) Transferring the secondary esterification mother liquor into a beaker, sealing the opening with a plastic mold, putting the beaker into a temperature-controllable refrigerator, cooling the mother liquor at a cooling rate of 1 ℃ per hour from the temperature of 40-45 ℃, and keeping the mother liquor stationary for 24 hours until the temperature of the qualified mother liquor is reduced to 2 ℃ until all solid-phase sterol is separated out;

(6) vacuum filtering twice with Buchner funnel to obtain crude sterol 33g, mother liquor 255g, and measuring crude sterol content to 47.8%; the total sterol content in the mother liquor is 0.15%. Calculate crude first sterol yield 95.98%;

(7) transferring 33g of the crude sterol sample to a multistage countercurrent liquid-solid extraction device, and slowly adding 700g of extract liquor containing 99.8% of ethanol; after extraction, desolventizing and drying treatment is carried out, and the weight loss on drying is measured to be 0.002; weighing to obtain 15g of fine sterol, wherein the total content is 97 percent: the content of brassicasterol is 0%, the content of campesterol is 30%, the content of stigmasterol is 10%, and the content of B-sitosterol is 60%. The total yield of sterol is 89.44%; the content purification is higher than 3.5 percent of the traditional process, and the yield is higher than 7 percent of the traditional process.

The embodiment (1-2) can be obtained, the invention adopts the biological polar resin as the solid catalyst bed to carry out catalytic reaction, the quality is stable and reliable, the conversion rate is high, the reverse flow liquid-solid extraction process adopted in the crude sterol purification and refining process has the characteristics of good purification effect, high efficiency, practicability and low cost, the complete process flow can realize completely continuous industrial production, and the invention has obvious advantages compared with the traditional process.

Claims

1. The process for extracting the phytosterol by utilizing the biological polar resin is characterized by comprising the following steps of:

step 1, esterification reaction: adding 12-20 times of low-carbon alcohol of free fatty acid mole number into the deodorized distillate (DD oil) subjected to pretreatment, dehydration and deslagging, wherein the low-carbon alcohol is methanol or ethanol, and reacting for 2-4 hours at 40-55 ℃ under reflux temperature by using a curing bed based on strong cation exchange resin C-25S; so that the fatty acid in the raw oil and the lower alcohol are subjected to esterification reaction to generate fatty acid methyl ester, and the final test that the acid value in the DD oil is less than 3.0mgKOH/g is qualified.

Step 2, vacuum desolventizing and drying: after the step 1, the raw oil is subjected to vacuum desolventizing dehydration, the vacuum degree is 20-80 mbar, the temperature is 80-100 ℃, and the measured moisture content is less than 0.005, so that the raw oil is qualified.

Step 3, ester exchange reaction: after the steps 1 and 2, adding methanol or ethanol solution with the mole number being 12-20 times that of the qualified raw oil generated in the step 2, uniformly stirring, feeding the raw oil into a fluidized bed based on Ambersep900OH strong-base anion exchange resin, adjusting the pH value of the raw oil to 7-7.5 by using a trace composite catalyst, reacting for 3-5 hours at the reflux temperature of 40-45 ℃, and carrying out transesterification reaction on triglyceride and low alcohol in the raw oil to generate fatty acid methyl ester, wherein meanwhile, the sterol ester in the (DD) oil is converted into free sterol under the action of the composite catalyst, so that the yield and the yield of the total sterol are improved. And (4) after the step (3) is finished and the content of the sterol ester in the raw oil is measured to be less than 0.003, repeating the step (2) to remove the redundant methanol, wherein the treated raw oil is collectively called as qualified mother liquor.

Step 4, freezing and fractionation: transferring the qualified mother liquor processed in the steps 1, 2 and 3 into a special cold separation kettle, cooling at a cooling rate of 1 ℃ per hour under the condition of a stirring speed of 5-10 revolutions per minute from the temperature of 40-45 ℃, starting to separate out solid sterol when the temperature of the qualified mother liquor is reduced to 25-30 ℃, and continuously cooling at a cooling rate of 0.5-0.6 ℃ per hour when the stirring speed is reduced to 3-6 revolutions per minute. And when the temperature is reduced to 2-4 ℃, completely turning off the solid-phase sterol, wherein the solid-phase sterol is crude phytosterol with low content.

Step 5, multistage continuous countercurrent liquid-solid extraction: step 4, freezing and separating low-content crude sterol, and treating by using a multi-stage counter-current liquid-solid extraction device; dissolving the phase solvent of the extract into n-hexane, petroleum or ethanol; the solid phase is low-content crude sterol, and the mass (g) of the solid phase is 1: 10-20 of the volume (ml) of a liquid phase solvent.

Step 6, solid phase desolvation: and (5) removing redundant solvent from the extraction solid phase in the step (5) through reduced pressure distillation, and determining that the drying weight loss is less than 0.003 to be qualified, thus obtaining a concentrated phytosterol product.

And 7, recovering a liquid residual phase: and (5) performing phase cold separation on the raffinate obtained in the step (5) to separate the phytosterol, and then performing recovery in a reduced pressure recovery tower to obtain a qualified liquid phase solvent, wherein the water content is less than 0.002, and the product is qualified.

The raw materials are plant oil deodorized distillate, a secondary biological resin purification method is adopted, the solvent consumption is low, the production cost is low, the yield and the yield of the sterol are improved, the environmental pollution caused by concentrated sulfuric acid and liquid caustic soda is avoided, the production environment is clean, the environment is protected, the carbon is low, the time consumption is shorter, the production efficiency is higher, the purity of the purified refined sterol can reach more than 95-99%, and the refined sterol has high whiteness and few black spots and can completely reach the export quality standard.