Preparation and purification method of diolein

Abstract

The invention provides a preparation and purification method of glyceryl dioleate, which adopts a synergistic catalysis system consisting of immobilized lipase and a mild chemical catalyst to catalyze esterification reaction of glycerol and oleic acid at medium and low temperature (50-70 DEG C). According to the invention, through organic combination of a low-temperature concerted catalytic reaction and a combined purification process, the proportion and reaction parameters of the composite catalyst are adjusted, so that the proportion of 1, 2-isomer to 1, 3-isomer in the product can be accurately regulated and controlled in a specific range; the flexibility is difficult to realize by an existing purification chemical method (uncontrollable isomerization caused by high temperature) or a pure enzyme method (generally fixed bias to 1, 3-site), and the requirements of different downstream applications on specific isomers are met.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical and chemical engineering, and more specifically relates to a method for the preparation and purification of dioleoglyceride. Background Technology

[0002] Glyceryl glycerol is a functional lipid compound formed by the esterification reaction of glycerol and two oleic acid molecules. Based on the position of fatty acids on the glycerol backbone, it mainly exists in two isomers: 1,2-dioleyl glycerol and 1,3-dioleyl glycerol. These two isomers exhibit significant differences in biological activity, metabolic pathways, and applications: 1,2-dioleyl glycerol acts as an intracellular second messenger, participating in the regulation of cellular stimulus-response mechanisms and controlling cellular life activities; it is a precursor for the synthesis of phospholipids and triglycerides in the body. In contrast, 1,3-dioleyl glycerol, due to its unique metabolic pathway, does not accumulate in the human body like ordinary fats and has physiological functions such as reducing visceral fat, lowering blood lipids, alleviating diabetes, and inhibiting weight gain.

[0003] Currently, the main methods for preparing dioleoglycerides fall into two categories: chemical synthesis and enzymatic synthesis.

[0004] Chemical synthesis typically involves the direct esterification of glycerol with oleic acid at high temperatures (175–185°C) using tin-containing catalysts (such as tin oxide, stannous chloride, and stannous oxalate). The crude dioleoglycerate is then obtained by molecular distillation. While this method can achieve high reaction rates, it requires high temperatures, which can lead to intramolecular acyl migration of the thermally unstable 1,2-isomer, transforming it into the more stable 1,3-isomer. This negatively impacts the yield and purity of the target product.

[0005] Enzymatic synthesis utilizes lipases (such as Lipozyme 435, Lipozyme RM IM, etc.) to catalyze the alcoholysis or esterification of fats and oils under mild conditions (50-70℃) to synthesize dioleoglycerates. While enzymatic methods offer advantages such as mild reaction conditions and good position selectivity, they generally suffer from high catalyst costs, slow reaction rates, and enzyme inactivation during long-term operation, posing economic and efficiency challenges for large-scale industrial production. Existing technologies report the use of 8% Lipozyme RM IM as a catalyst, reacting at 30℃ for 8 hours, achieving a 1,3-dioleoglycerate content of 87.6% in the crude reaction mixture. Subsequent purification yields 1,3-dioleoglycerates with a purity >97%, a yield of 74.7%. This method demonstrates the regional selectivity advantage of enzymatic methods at low temperatures, but it still suffers from problems such as long reaction time and high enzyme dosage. Furthermore, its process focuses on pure enzyme catalysis and does not involve synergistic effects with chemical catalysts, nor does it provide a means to flexibly control the ratio of 1,2-isomers to 1,3-isomers in the product.

[0006] In terms of purification techniques, existing methods mainly include silica gel column chromatography, solvent crystallization, and molecular distillation. Silica gel column chromatography typically uses hexane-ethyl acetate as the eluent, achieving product purity of at least 95%, but it suffers from complex operation, high solvent consumption, and difficulty in large-scale application. Solvent crystallization employs a two-step method: first, a non-polar solvent (such as hexane) is used to remove impurities such as triglycerides and fatty acid esters; then, a polar solvent (such as methanol) is used to remove impurities such as monoglycerides and glycerol. Although it can obtain 1,2-diglycerides with a purity close to 100%, the crystallization conditions are harsh (e.g., -40°C) and the crystallization time is long (up to 18 hours), which is not conducive to industrial operation. Molecular distillation can purify dioleoglycerides under high vacuum and high temperature (200~220°C), but the high temperature environment may exacerbate isomer conversion, and the product yield is low (approximately 69%).

[0007] Therefore, developing a technology for the preparation and purification of dioleoglycerides that can inhibit acyl migration, improve product purity, and is suitable for industrial production has become a pressing technical challenge in this field. Summary of the Invention

[0008] This invention proposes a method for the preparation and purification of dioleoglycerate. By organically combining low-temperature synergistic catalytic reaction with combined purification processes, and by adjusting the ratio of composite catalysts and reaction parameters, the ratio of 1,2-isomers to 1,3-isomers in the product can be precisely controlled within a specific range while ensuring high yield and high purity. This flexibility is difficult to achieve with existing chemical purification methods (which lead to uncontrollable isomerization due to high temperature) or pure enzymatic methods (which usually fix the bias towards the 1,3-position), thus meeting the needs of different downstream applications for specific isomers.

[0009] The technical solution of this invention is implemented as follows: A method for preparing dioleoglycerate involves catalyzing the esterification reaction of glycerol and oleic acid in a synergistic catalytic system composed of an enzyme catalyst and a chemical catalyst.

[0010] Preferably, the molar ratio of glycerol to oleic acid is 1:2.0 to 1:2.5, the mass ratio of enzyme catalyst to chemical catalyst is 3:1 to 8:1, the amount of enzyme catalyst is 0.5% to 5% of the total mass, and the amount of chemical catalyst is 0.1% to 1% of the total mass.

[0011] Preferably, the molar ratio of glycerol to oleic acid is 1:2.1 to 1:2.2, the mass ratio of enzyme catalyst to chemical catalyst is 4:1 to 6:1, the amount of enzyme catalyst is 2% to 4% of the total mass, and the amount of chemical catalyst is 0.3% to 0.6% of the total mass.

[0012] Preferably, under vacuum conditions, the reaction temperature is 50~70℃ and the reaction time is 2~4 hours.

[0013] Preferably, the vacuum degree is 0.5~2.0 kPa, the reaction temperature is 55~65℃, and the reaction time is 2.5~3.5 hours.

[0014] Preferably, the enzyme catalyst is selected from immobilized lipases, including one or more of Lipozyme RM IM, Novozyme 435, and Lipozyme TL IM.

[0015] Preferably, the chemical catalyst is selected from organotin compounds.

[0016] Preferably, the chemical catalyst is stannous oxalate.

[0017] A method for purifying dioleoglycerides involves subjecting a mixture containing dioleoglycerides obtained by the above preparation method to two-stage molecular distillation: a first-stage distillation at 150-170°C and a second-stage distillation at 180-200°C, to remove impurities from the reaction mixture; and then using multi-stage melt crystallization technology to separate and purify 1,2-dioleoglycerides and 1,3-dioleoglycerides.

[0018] Preferably, the two-stage molecular distillation conditions are: first-stage distillation temperature of 155~165℃, second-stage distillation temperature of 185~195℃, and vacuum pressure of 0.1×10⁻⁶. -2 ~ 1.0×10 -2 mbar, feed rate: 1.5~2.5 mL / min.

[0019] Compared with the prior art, the advantages of this invention are: (1) Compared with existing literature on pure enzymatic methods: Pure enzymatic method (8% Lipozyme RM IM, 30℃, 8 hours, 1,3-isomer content in crude product 87.6%, total yield 74.7%), the synergistic catalytic system of the present invention can be carried out at a shorter reaction time (3 hours), a lower enzyme dosage (3.0 wt%), and a reaction temperature (60℃) more conducive to industrialization. Although the 1,3-isomer content in the mixture after the reaction (71.2%) is slightly lower than that of the crude product from the pure enzymatic method, higher product purity (98.7%) and a significantly improved total yield (86%) were finally obtained through subsequent efficient combined purification processes. This reflects the comprehensive advantages of the present invention in balancing reaction efficiency, catalyst cost and final product economic benefits. This proves the comprehensive advantages of the "enzyme-chemical synergistic catalysis" strategy in improving overall process efficiency, reducing catalyst cost and maintaining high-quality product output, rather than a simple additive effect; (2) By adjusting the ratio of the composite catalyst and reaction parameters, this invention can achieve continuous and precise control of the ratio of 1,2-dioleoylglycerol to 1,3-dioleoylglycerol in the product within the range of 1:10 to 1:4 (i.e., 0.1 to 0.25) without significantly reducing the total yield and purity of the product (see Examples 1, 2, and 4). This control range fills the gap between the pure enzymatic method (the ratio tends to be above 1:9, i.e., the 1,3 isomer is absolutely dominant) and the pure chemical method (the ratio is usually around 2:5, i.e., the proportion of 1,2 isomer is significantly increased), and meets the differentiated needs of different downstream applications for the specific isomer ratio. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is the liquid chromatogram of the crude oleic acid glyceride of the present invention. Detailed Implementation

[0022] Catalytic Mechanism Explanation: In this invention, the immobilized lipase (such as Lipozyme RM IM) exhibits a clear 1,3-site regioselectivity, tending to catalyze the formation of 1,3-dioleoyl glycerol. Meanwhile, the specific chemical catalyst, stannous oxalate, acts as a mild esterification reaction promoter, effectively inhibiting the acyl migration of 1,2-dioleoyl glycerol to 1,3-dioleoyl glycerol during the reaction, while simultaneously increasing the overall reaction rate. This synergistic effect allows for the maintenance of high reaction efficiency and enzyme regioselectivity under mild conditions, while also enabling flexible and controllable adjustment of the ratio of the two isomers in the final product by regulating the catalyst ratio.

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for preparing dioleoglycerate, employing a synergistic catalytic system consisting of an enzyme catalyst and a mild chemical catalyst to catalyze the esterification reaction of glycerol and oleic acid under medium-low temperature conditions (50-70°C). The enzyme catalyst, selected from immobilized lipases, provides regioselectivity, primarily catalyzing the formation of 1,3-dioleoglycerate; the chemical catalyst promotes the rapid attainment of reaction equilibrium. By adjusting the ratio of the two catalysts and reaction parameters, precise control of the isomer ratio in the product within the range of 0.1 to 0.25 can be achieved. This flexibility is difficult to achieve with existing purely chemical methods (where high temperatures lead to uncontrollable isomerization) or purely enzymatic methods (which typically immobilize a bias towards the 1,3-isomer), thus meeting the specific isomer requirements of various downstream applications.

[0025] The synergistic catalytic system consists of: an enzyme catalyst selected from immobilized lipases, including but not limited to one or more of Lipozyme RMIM, Novozym 435, and Lipozyme TLIM, preferably Lipozyme RMIM. The amount used ranges from 0.5% to 5% of the total substrate mass, preferably 2% to 4%. The chemical catalyst is selected from stannous oxalate. Extensive experiments have shown that not all organotin compounds can produce good synergistic effects with the specified lipase, effectively inhibiting acyl migration and improving the selectivity and yield of the target product. For example, under the same reaction conditions, the synergistic effect of dibutyltin dilaurate and dibutyltin diacetate with lipases is far less than that of stannous oxalate. Therefore, this invention preferably and specifically uses stannous oxalate as the chemical catalyst, with an amount ranging from 0.1% to 1% of the total substrate mass, preferably 0.3% to 0.6%.

[0026] Reaction ratios and conditions: Molar ratio of glycerol to oleic acid: controlled within the range of 1:2.0 ~ 1:2.5, preferably 1:2.1 ~ 1:2.2; Mass ratio of immobilized lipase to stannous oxalate: controlled within the range of (3:1) ~ (8:1), preferably (4:1) ~ (6:1); Reaction temperature: 50 ~ 70℃, preferably 55 ~ 65℃; Reaction time: 2 ~ 4 hours, preferably 2.5 ~ 3.5 hours; Reaction pressure: carried out under vacuum conditions, with the vacuum degree maintained at 0.5 ~ 2.0 kPa, to remove the water generated in the reaction. Under these preferred reaction conditions, the content of 1,3-dioleoglycerate in the mixture after the reaction can reach up to 71.2%.

[0027] In another aspect, this invention provides a method for purifying dioleoglycerides, creatively combining molecular distillation with melt crystallization technology to form a highly efficient purification process. First, the reaction mixture is subjected to two-stage molecular distillation under mild conditions to remove free fatty acids, monoglycerides, and some triglycerides. Then, using multi-stage melt crystallization technology, through precise control of the cooling process and crystal separation, the efficient separation and purification of 1,2- and 1,3-dioleoglycerides are achieved. Two-stage molecular distillation: First-stage distillation temperature: 150~170℃, preferably 155~165℃; Second-stage distillation temperature: 180~200℃, preferably 185~195℃; Vacuum pressure: 0.1×10⁻⁶ -2 ~ 1.0×10 -2 mbar; feed rate: 1.5~2.5 mL / min. After preliminary purification by two-stage molecular distillation, the content of 1,3-dioleoylglycerol in the fraction can be as high as 98.7%.

[0028] This invention combines low-temperature synergistic catalytic reaction with a combined purification process, reducing the reaction temperature from 175-185℃ in traditional chemical methods to 50-70℃. This not only reduces energy consumption but also suppresses side reactions and isomerization, while extending catalyst lifespan. The purity of 1,3-dioleoylglycerol ester in the final product is no less than 98%, significantly higher than the 95% purity achieved through traditional chemical purification. Because the purification process avoids the use of large amounts of organic solvents, the final product contains no solvent residue, meeting the stringent standards for pharmaceutical and food applications. Furthermore, the low-temperature operating conditions reduce oxidative decomposition byproducts of the glycerol ester, improving product stability and safety.

[0029] Example 1: Preparation of high-purity 1,3-dioleoylglycerol

[0030] Glycerol (92.1 g, 1.0 mol) and oleic acid (710 g, 2.5 mol, molar ratio 1:2.1) were added to the reactor. Lipozyme RM IM (24.1 g, 3.0 wt%) and stannous oxalate (4.0 g, 0.5 wt%) were added at a mass ratio of 6:1. The mixture was stirred (250 rpm) and subjected to vacuum (1.0 kPa), and the temperature was raised to 60 °C for 3 hours. After the reaction was complete, a small amount of the reaction mixture was filtered and directly analyzed by HPLC.

[0031] Primary purification: After the reaction, the catalyst was recovered by filtration (it can be reused). The reaction mixture was then subjected to two-stage molecular distillation. The first-stage distillation conditions were: temperature 160℃, feed rate 2 mL / min, scraper speed 100 r / min, and vacuum pressure 0.5 × 10⁻⁶. -2 mbar; Secondary distillation conditions: temperature 190℃, other parameters the same as the first stage. Collect the heavy phase from the distillation to obtain crude dioleoyl glycerol.

[0032] Melt crystallization separation: The crude dioleoglycerate was heated to 70°C to completely melt it, and then cooled to -5°C at a rate of 0.3°C / min. Crystals were grown at this temperature for 2 hours. The crystals (mainly 1,3-dioleoglycerate) and the mother liquor (rich in 1,2-dioleoglycerate) were separated by filtration. The crystals were washed with a small amount of n-hexane and then vacuum dried to obtain the final product.

[0033] Product analysis, performed by high-performance liquid chromatography (HPLC), revealed the following composition of the post-reaction mixture: 1,3-dioleoglycerate: 71.2%; 1,2-dioleoglycerate: 8.5%; monooleoglycerate: 5.3%; trioleoglycerate: 13.1%; free fatty acids: 2.0%. The final product contained 98.7% pure 1,3-dioleoglycerate with an overall yield of 86%. The ratio of the 1,2-isomer to the 1,3-isomer was 0.119 (approximately 1:8.4).

[0034] Example 2: Changing the catalyst ratio

[0035] Same as in Example 1, with other conditions unchanged, but the catalyst ratio was adjusted to Lipozyme RM IM (20.1 g, 2.5 wt%) and stannous oxalate (6.0 g, 0.75 wt%), with a mass ratio of approximately 3.3:1.

[0036] Product Analysis: HPLC analysis revealed the following composition of the post-reaction mixture: 1,3-dioleoglycerate: 68.5%; 1,2-dioleoglycerate: 10.1%; monooleoglycerate: 6.2%; trioleoglycerate: 13.5%; free fatty acids: 1.7%. The purity of 1,3-dioleoglycerate in the final product was 98.1%, with an overall yield of 82%. The ratio of the 1,2-isomer to the 1,3-isomer was 0.147 (approximately 1:6.8).

[0037] Example 3: Changing the substrate molar ratio

[0038] Same as Example 1, with other conditions unchanged, but the molar ratio of glycerol to oleic acid was adjusted to 1:2.4.

[0039] Product Analysis: HPLC analysis revealed the following composition of the post-reaction mixture: 1,3-dioleoglycerate: 69.8%; 1,2-dioleoglycerate: 9.2%; monooleoglycerate: 8.1%; trioleoglycerate: 8.5%; free fatty acids: 4.4%. Final Product Purity: 1,3-dioleoglycerate purity 98.3%, overall yield 80%. The ratio of 1,2-isomer to 1,3-isomer was 0.132 (approximately 1:7.6).

[0040] Example 4: Isomer regulation under different catalyst ratios while controlling other conditions as in Example 1

[0041] The above data show that, under the synergistic catalytic system and preferred reaction conditions described in this invention, the ratio of 1,2- to 1,3- isomers in the product can be systematically controlled and continuously varied within the range of 0.1 to 0.23 by adjusting the mass ratio of the enzyme catalyst to stannous oxalate. With increasing proportion of the chemical catalyst (stannous oxalate), its effect of inhibiting acyl migration and retaining the 1,2- isomer is enhanced, leading to a gradual increase in the 1,2- isomer content and a corresponding decrease in the 1,3- isomer content, thus achieving effective control over the isomer composition.

[0042] Comparative Example 1: Using only enzyme catalysts

[0043] Same as Example 1, with other conditions unchanged, but only Lipozyme RM IM (28.1 g, 3.5 wt%) was added, and stannous oxalate was not added.

[0044] Product Analysis: Composition of the post-reaction mixture: 1,3-dioleoglycerate: 65.3%; 1,2-dioleoglycerate: 6.8%; monooleoglycerate: 12.5%; trioleoglycerate: 8.9%; free fatty acids: 6.5%. Final product purity: 1,3-dioleoglycerate purity 98.0%, overall yield 75%. The ratio of 1,2-isomer to 1,3-isomer was 0.104 (approximately 1:9.6).

[0045] Comparative Example 2: Using only chemical catalysts

[0046] Same as Example 1, with other conditions unchanged, but only stannous oxalate (8.0 g, 1.0 wt%) was added, and lipase was not added.

[0047] Product Analysis: Composition of the post-reaction mixture: 1,3-dioleoglycerate: 58.1%; 1,2-dioleoglycerate: 25.3% (partially isomerized); monooleoglycerate: 4.1%; trioleoglycerate: 10.2%; free fatty acids: 2.3%. Final product purity: 1,3-dioleoglycerate purity 97.5%, overall yield 78%. The ratio of 1,2-isomer to 1,3-isomer was 0.435 (approximately 2:4.6).

[0048] Comparative Example 3: High-Temperature Chemical Method (Simulating Existing Technology)

[0049] The method disclosed in CN 117623921 A was adopted, with a molar ratio of glycerol to oleic acid of 1:2.5, and stannous chloride (6.4 g, 0.8 wt%) was added. The reaction was carried out at 180 °C for 3 hours.

[0050] Product Analysis: Composition of the post-reaction mixture: 1,3-dioleoglycerate: 62.5%; 1,2-dioleoglycerate: 18.8% (severe isomerization due to high temperature); monooleoglycerate: 3.5%; trioleoglycerate: 13.5%; free fatty acids: 1.7%. Final product purity: 1,3-dioleoglycerate purity 96.2%, overall yield 72%. The content ratio of 1,2-isomer to 1,3-isomer is 0.301 (approximately 3:10).

[0051] Comparative Example 4: Using dibutyltin dilaurate as a chemical catalyst

[0052] Same as in Example 1, with other conditions unchanged, but stannous oxalate (4.0 g, 0.5 wt%) was replaced with an equal mass of dibutyltin dilaurate (4.0 g, 0.5 wt%), and a synergistic catalytic system was formed with Lipozyme RM IM (24.1 g, 3.0 wt%) (mass ratio still 6:1).

[0053] Product Analysis: HPLC analysis revealed the following composition of the post-reaction mixture: 1,3-dioleoglycerate: 64.8%; 1,2-dioleoglycerate: 20.5% (indicating poor inhibition of acyl migration); monooleoglycerate: 6.0%; trioleoglycerate: 6.3%; free fatty acids: 2.4%. The purity of 1,3-dioleoglycerate in the final product was 97.8%, with an overall yield of 76%. The ratio of 1,2-isomer to 1,3-isomer was 0.316 (approximately 1:3.2). These results indicate that while using dibutyltin dilaurate resulted in a higher proportion of 1,2-isomers in the post-reaction mixture, seemingly indicating stronger inhibition of acyl migration, the absolute content and overall yield of the 1,3-isomer were significantly lower than in Example 1 using stannous oxalate. This indicates that the synergistic effect between dibutyltin dilaurate and lipase is poor. While inhibiting migration, it fails to work well with the regioselectivity of the enzyme to maintain high reaction efficiency and high-value 1,3-isomer yield.

[0054] Comparative Example 5: Using dibutyltin diacetate as a chemical catalyst

[0055] Same as in Example 1, with other conditions unchanged, but stannous oxalate (4.0 g, 0.5 wt%) was replaced with an equal mass of dibutyltin diacetate (4.0 g, 0.5 wt%).

[0056] Product Analysis: HPLC analysis revealed the following composition of the post-reaction mixture: 1,3-dioleoglycerate: 62.1%; 1,2-dioleoglycerate: 22.8%; monooleoglycerate: 7.2%; trioleoglycerate: 5.5%; free fatty acids: 2.4%. The final product contained 97.5% pure 1,3-dioleoglycerate with an overall yield of 74%. The ratio of the 1,2-isomer to the 1,3-isomer was 0.367 (approximately 1:2.7). This result further confirms the significant differences in the synergistic effects of different organotin catalysts. The synergistic effect of dibutyltin diacetate with lipase was also weaker than that with stannous oxalate, leading to a decrease in reaction selectivity, target product content, and overall yield.

[0057] Comparative Examples 4 and 5 illustrate that not all organotin compounds can form effective synergistic catalytic systems with the specified lipases. While dibutyltin dilaurate and dibutyltin diacetate exhibit some ability to inhibit acyl migration (manifested as a higher proportion of the 1,2-isomer), their synergistic effect with the lipase Lipozyme RM IM is far inferior to that of stannous oxalate. This is reflected in the significantly lower absolute content of the 1,3-isomer, the purity of the final product, and the overall yield after the reaction. This highlights the irreplaceable role of stannous oxalate in the synergistic system of this invention. It not only effectively inhibits unfavorable acyl migration but also synergizes with the regioselectivity of lipases, achieving high yield, high purity, and controllable adjustment of isomer ratios under mild conditions.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing dioleoylglycerol, characterized in that, The esterification reaction of glycerol and oleic acid was catalyzed using a synergistic catalytic system composed of an enzyme catalyst and a chemical catalyst.

2. The preparation method according to claim 1, characterized in that, The molar ratio of glycerol to oleic acid is 1:2.0 to 1:2.5, the mass ratio of enzyme catalyst to chemical catalyst is 3:1 to 8:1, the amount of enzyme catalyst is 0.5% to 5% of the total mass, and the amount of chemical catalyst is 0.1% to 1% of the total mass.

3. The preparation method according to claim 2, characterized in that, The molar ratio of glycerol to oleic acid is 1:2.1 to 1:2.2, the mass ratio of enzyme catalyst to chemical catalyst is 4:1 to 6:1, the amount of enzyme catalyst is 2% to 4% of the total mass, and the amount of chemical catalyst is 0.3% to 0.6% of the total mass.

4. The preparation method according to claim 1, characterized in that, Under vacuum conditions, the reaction temperature is 50~70℃ and the reaction time is 2~4 hours.

5. The preparation method according to claim 4, characterized in that, The vacuum degree is 0.5~2.0 KPa, the reaction temperature is 55~65℃, and the reaction time is 2.5~3.5 hours.

6. The preparation method according to claim 1, characterized in that, The enzyme catalyst is selected from immobilized lipases, including one or more of Lipozyme RM IM, Novozyme 435, and Lipozyme TL IM.

7. The preparation method according to claim 1, characterized in that, The chemical catalyst is selected from organotin compounds.

8. The preparation method according to claim 7, characterized in that, The chemical catalyst is stannous oxalate.

9. A method for purifying dioleoyl glyceride, characterized in that, The mixture containing dioleoglycerate obtained by the preparation method described in claims 1-8 is subjected to two-stage molecular distillation: first-stage distillation at 150-170°C and second-stage distillation at 180-200°C to remove impurities from the reaction mixture; then, multi-stage melt crystallization technology is used to separate and purify 1,2-dioleoglycerate and 1,3-dioleoglycerate.

10. The purification method according to claim 9, characterized in that, The two-stage molecular distillation conditions are: the first-stage distillation temperature is 155-165 °C, the second-stage distillation temperature is 185-195 °C, the vacuum pressure is 0.1-0.5 x 10 -2 ~ 1.0 x 10 -2 mbar, and the feeding rate is 1.5-2.5 mL / min.

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