A method for purifying high acid value OPO mixed oil

Abstract

The present invention provides a method for purifying a high-acid-value OPO mixed oil, wherein the high-acid-value OPO mixed oil is subjected to a first-stage molecular distillation to obtain a heavy component, the heavy component is mixed with an extracting agent, and then a second-stage molecular distillation is performed to obtain purified OPO after decolorization and deodorization. Compared with the traditional process, the present invention can significantly reduce the acid value of the purified OPO, and can also reduce the distillation temperature required for the second-stage molecular distillation, effectively control the generation of 3-chloropropanol esters and glycidyl esters during the purification process, prevent the rapid increase of peroxide value and color, and inhibit the acyl transfer phenomenon of the OPO glycerol skeleton to ensure the high content of purified OPO, and the extracting agent provided by the present invention does not introduce other exogenous substances on the basis of the OPO ester exchange system, and further ensures the content and safety of the product.

Description

Technical Field

[0001] The invention relates to the technical field of molecular distillation separation, to the field of functional oil biosynthesis technology, and more specifically to a method for purifying high-acid-value OPO mixed oil. Background Art

[0002] 1,3-Dioleoyl-2-palmitoyl triglyceride (OPO for short) is a functional oil with a natural breast milk structure and is an important nutrient in breast milk and infant formula. The special molecular structure of OPO is that the SN-1 and 3 positions of the glycerol skeleton are connected to unsaturated fatty acids (oleic acid) and the SN-2 position is connected to saturated fatty acids (palmitic acid), which is similar to the structure of fats in breast milk. Studies have shown that adding OPO to infant formula can help promote digestion and absorption, protect the intestines, relieve constipation, and is beneficial to the bone growth and strength of infants and young children.

[0003] The mixed oil with high acid value OPO is the intermediate product derived from the acidolysis reaction of palm stearin and oleic acid under the bio-enzyme catalysis process. The main components include glycerides mainly composed of OPO, oleic acid, palmitic acid, stearic acid, linoleic acid, linolenic acid, mono(di)glycerides, glycerol and other impurities. Since the acid value of this type of mixed oil is often too high and the composition is complex, it needs to be further purified by molecular distillation process to obtain high-quality OPO.

[0004] In the field of structural fats, considering the need for food safety, people do not want to reduce the acid value of OPO produced during the production process by adding alkali solution, and mainly use one or more molecular distillation processes for separation. This method can ensure that the product has less loss during the refining process, but it also brings some problems, which affect the production of high-quality OPO, mainly including the following points:

[0005] (1) The purification effect is poor, and the acid value of purified OPO is high. The C14-C18 straight-chain fatty acids contained in the molecular structure of fatty acids, glycerides, mono(di)glycerides and other impurities in the mixed oils are all linear structures, which are easy to be "entangled" with OPO, forming wrapping and adhesion, so the impurities cannot be completely separated and removed, resulting in a high acid value of OPO.

[0006] (2) The quality of purified OPO is poor. The traditional molecular distillation purification process relies on a high temperature environment, which can easily increase the rapid increase in the content of peroxides, color, 3-chloropropanol esters and glycidyl esters in oils and fats, affecting the appearance and safety of OPO. High temperature environments can also intensify the "acyl transfer" of oils and fats, leading to a decrease in OPO content.

[0007] (3) Traditional catalysts are not suitable for OPO systems, and catalysts specific to OPO systems need to be developed. Summary of the invention

[0008] Purpose of the invention: The purpose of the present invention is to provide a method for purifying high-acid-value mixed oils and fats formed in the OPO production process, thereby improving the molecular distillation purification effect and reducing the generation of harmful substances without introducing other exogenous substances.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides a method for purifying a high-acid-value OPO mixed oil, which comprises subjecting the high-acid-value OPO mixed oil to a first-stage molecular distillation to obtain a heavy component, mixing the heavy component with an extracting agent, and then subjecting the heavy component to a second-stage molecular distillation to obtain purified OPO after decolorization and deodorization;

[0010] The acid value of the high-acid-value OPO mixed oil is not less than 170 mg KOH / g; the amount of the extracting agent added is 1-8 wt% of the heavy component, and the extracting agent contains not less than 50 wt% of glycerol.

[0011] As a further optimization of the present invention, the extraction promoter includes 80-95 wt % of glycerol, 0.1-10 wt % of stabilizer and 0.1-10 wt % of water.

[0012] As a further optimization of the present invention, the stabilizer is 5-10wt% of the mass of the extracting agent, including but not limited to any one or more combinations of monopalmitin, monostearate, monooleate, and monolinoleate. As an optimal solution of the present invention, the extracting agent is composed of 90wt% glycerol, 3.5wt% monostearate, 2.5wt% monopalmitin, and 4wt% water.

[0013] The present invention provides an OPO extracting agent for cooperating with a molecular distillation process, which is mixed with the heavy component and can effectively disperse and dilute the wrapping and adhesion effects caused by long-chain fatty acids in the heavy component during the second-stage molecular distillation process, thereby improving the molecular distillation purification effect, and achieving the effect of reducing the second-stage molecular distillation temperature and significantly reducing the acid value. In particular, when the extracting agent includes a mixture of glycerol esters esterified with single-chain fatty acids and water in an amount of no more than 10 wt% in addition to glycerol, the generation of 3-chloropropanol esters and glycidyl esters during the purification process can also be effectively controlled, the rapid increase of peroxide value and color can be prevented, and the acyl transfer phenomenon of the OPO glycerol skeleton can be inhibited, thereby ensuring a high content of purified OPO.

[0014] As a further optimization of the present invention, the amount of the extracting agent added is 2-6 wt % of the heavy component.

[0015] As a preferred method of adding the extracting agent, the heavy component and the extracting agent are mixed evenly in a container and then subjected to the second stage molecular distillation. The container can be a mixing tank with a mechanical stirring component or a static suspension.

[0016] Furthermore, the distillation temperature of the first stage molecular distillation is 150-160°C, the condensation temperature is 30-40°C, and the vacuum degree is ≤10 Pa; the preferred vacuum degree is 5-10 Pa, and the more preferred vacuum degree is 7-8 Pa.

[0017] Furthermore, the distillation temperature of the second-stage molecular distillation is 160-170 ° C, the condensation temperature is 30-40 ° C, and the vacuum degree is ≤1 Pa. In order to remove the remaining fatty acids and impurities in the second-stage molecular distillation, the distillation temperature is controlled not to exceed 170 ° C, and this is achieved by further increasing the vacuum degree of the second-stage molecular distillation. The control of the distillation temperature is very critical and will directly affect the content of harmful substances and refining losses. It is preferred to reduce the vacuum degree of the second-stage molecular distillation to below 0.5 Pa, and the distillation temperature is controlled at 160-165 ° C to achieve the desired effect.

[0018] It should be noted that the method provided by the present invention does not include any alkali refining process or chemical methods similar to alkali refining process to adjust pH, so as to avoid the residue of harmful substances caused by alkaline substances. It is also worth noting that the extracting agent provided by the present application is mainly glycerol, and no other exogenous substances are introduced on the basis of the OPO transesterification system, which further ensures the content and safety of the product.

[0019] Furthermore, the decolorization process includes adding a decolorization adsorbent to the heavy component after the second stage molecular distillation, and filtering out the decolorization adsorbent after heating and stirring. As a preferred embodiment, the heavy component after the second stage molecular distillation is pumped into a decolorization tank, 0.5-1.0 wt% of the second stage molecular distillation heavy component of kaolin and 0.1-0.5 wt% of activated carbon are added to the decolorization tank, fully stirred at 80 ° C, and filtered out the kaolin and activated carbon after mixing for 30 minutes.

[0020] Furthermore, the deodorization process is carried out in a deodorization tower, and at least includes high-temperature deodorization and steam stripping. As a preferred embodiment, the deodorization process is to pump the decolorized oil into the deodorization tower, the deodorization temperature is 220-230 ° C, the deodorization time is 30 minutes, and the odor in the oil is removed by steam stripping.

[0021] It should be understood that those skilled in the art can make adaptive improvements to the deodorization process and the decolorization process within a limited range based on the above technical solutions without departing from the inventive principles of the present application, and all of these are within the protection scope of the present application.

[0022] The quality of the purified OPO produced and prepared by the purification method provided by the present invention is significantly improved. Specifically, the purified OPO has the following characteristics:

[0023] Acid value ≤ 0.20 mg KOH / g;

[0024] OPO content ≥ 53 wt%;

[0025] 3-chloropropanol ester ≤ 0.4 mg / kg;

[0026] Glycidyl ester ≤ 0.2 mg / kg.

[0027] Peroxide value ≤ 0.5 mmol / kg;

[0028] Color (Lovibond colorimetric trough 133.4 mm) ≤ 2.0R / 20Y;

[0029] Among them, acid value refers to the content of free acid in OPO. The lower the acid value, the lower the content of free acid such as residual fatty acid in OPO. High acid value will affect the content of OPO and also affect the stability of OPO. National standard GB 30604-2015 stipulates that the acid value of OPO is ≤3.0 mg KOH / g.

[0030] OPO content refers to the content of 1,3-dioleo-2-palmitoyl triglyceride (calculated as C52 triglyceride). The national standard GB 30604-2015 stipulates that the OPO content is ≥40 wt%.

[0031] 3-MCP and glycidyl esters are food safety contaminants of concern internationally. Toxicology research shows that 3-MCP has kidney, reproductive, and non-genotoxic effects, while glycidyl esters are genotoxic carcinogens. European Commission Regulation (EU) 2020 / 1322 stipulates that the limit of 3-MCP (calculated as 3-MCP) in vegetable oils and fats used in the production of infant food and infant cereal processed foods is not more than 750 μg / kg, and the limit of glycidyl ester (calculated as glycidol) in fish oil and marine oil used in the production of infant food and infant cereal processed foods is not more than 500 μg / kg.

[0032] Peroxide value is an important indicator of oil stability. The lower the peroxide value, the better the oil stability and the longer the storage time. The national standard GB 30604-2015 stipulates that the peroxide value of OPO is ≤0.5 mmol / kg. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific examples. Unless otherwise specified, all percentages, parts and ratios are by weight.

[0034] Example 1

[0035] The high acid value mixed oil (acid value 174 mg KOH / g) containing OPO is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155 ° C, the vacuum degree in the tower is 8 Pa, and the condenser temperature is 35 ° C. The heavy components of the distillation at the bottom of the tower are collected to obtain the concentrated OPO mixture. Glycerol, monostearate, monopalmitate and water are mixed and stored at a mass ratio of 90: 3.5: 2.5: 4, and the promoter is added in an amount of 2 wt% of the heavy components and mixed evenly with the concentrated OPO mixture in a static mixer, and then fed into the second-stage molecular distillation feed port, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160 ° C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35. The purified OPO obtained after decolorization and deodorization. It has been determined that the purified OPO obtained in this embodiment has the following qualities:

[0036] Table 1 Quality indicators of purified OPO obtained in Example 1

[0037] project Quality indicators Acid value, mg KOH / g 0.18 OPO content, % 53.84 3-Chloropropanol ester, mg / kg 0.40 Glycidyl ester, mg / kg 0.18 Peroxide value, mmol / kg 0.43 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0038] Among them, the determination method of acid value refers to the national standard GB 5009.229-2016; the determination method of OPO content refers to Appendix A.3 of the national standard GB30604-2015; the determination method of 3-chloropropanol ester and glycidyl ester refers to the national standard GB5009.191-2024; the determination method of peroxide value refers to the national standard GB 5009.227-2023; the determination of color (Lovibond colorimetric trough 133.4 mm) refers to the national standard GB / T 22460-2008. Unless otherwise specified, the quality indicators of purified OPO obtained in the following examples are all tested according to the above methods.

[0039] In this embodiment, the decolorization process is to pump the heavy component obtained after the second stage molecular distillation into a decolorization tank, add 0.5-1.0 wt% of the heavy component of the second stage molecular distillation into the decolorization tank, and add 0.1-0.5 wt% of activated carbon to the decolorization tank, fully stir and mix at a temperature of 80°C for 30 minutes, and then filter out the white clay and activated carbon. Unless otherwise specified, the following embodiments all use the same decolorization process as this embodiment.

[0040] In this embodiment, the deodorization process is to pump the decolorized oil into a deodorization tower, the deodorization temperature is 220-230°C, the deodorization time is 30 minutes, and the odor in the oil is removed by steam stripping. Unless otherwise specified, the following embodiments all use the same deodorization process as this embodiment.

[0041] Example 2

[0042] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155°C, the vacuum degree in the tower is 8 Pa, and the condenser temperature is 35°C. The heavy components distilled at the bottom of the tower are collected to obtain the concentrated OPO mixture. Glycerol, monostearate, monopalmitate and water are mixed and stored in a mass ratio of 90: 3.5: 2.5: 4, and the promoter is added in an amount of 4 wt% of the heavy components and mixed with the concentrated OPO mixture in a static mixer, and then fed into the second-stage molecular distillation feed port, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160°C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35°C. After decolorization and deodorization, purified OPO is obtained, having the following qualities:

[0043] Table 2 Quality indicators of purified OPO obtained in Example 2

[0044] project Quality indicators Acid value, mg KOH / g 0.13 OPO content, % 53.61 3-Chloropropanol ester, mg / kg 0.30 Glycidyl ester, mg / kg 0.13 Peroxide value, mmol / kg 0.40 Color (Lovibond colorimetric trough 133.4mm) < 2.0R / 20Y

[0045] Example 3

[0046] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155 ° C, the vacuum degree in the tower is 8 Pa, and the condenser temperature is 35 ° C. The heavy components of the distillation at the bottom of the tower are collected to obtain the concentrated OPO mixture. Glycerol, monostearate, monopalmitoyl glyceride, and water are mixed and stored at a mass ratio of 90: 3.5: 2.5: 4, and the promoter is added in an amount of 6 wt% of the heavy components and mixed with the concentrated OPO mixture in a static mixer, and then fed into the second-stage molecular distillation feed port, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160 ° C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35 ° C. After decolorization and deodorization, purified OPO is obtained, having the following qualities:

[0047] Table 3 Quality indicators of purified OPO obtained in Example 3

[0048] project Quality indicators Acid value, mg KOH / g 0.13 OPO content, % 53.36 3-Chloropropanol ester, mg / kg 0.30 Glycidyl ester, mg / kg 0.12 Peroxide value, mmol / kg 0.39 Color (Lovibond colorimetric trough 133.4mm) < 2.0R / 20Y

[0049] Example 4

[0050] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155 ° C, the vacuum degree in the tower is 8 Pa, and the condenser temperature is 35 ° C. The heavy components of the distillation at the bottom of the tower are collected to obtain the concentrated OPO mixture. Glycerol, monostearate, monopalmitoyl glyceride, and water are mixed and stored at a mass ratio of 90: 3.5: 2.5: 4, and the promoter is added in an amount of 8 wt% of the heavy components and the concentrated OPO mixture is mixed in a static mixer, and then fed into the feed port of the second-stage molecular distillation, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160 ° C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35 ° C. After decolorization and deodorization, purified OPO is obtained, having the following qualities:

[0051] Table 4 Quality indicators of purified OPO obtained in Example 4

[0052] project Quality indicators Acid value, mg KOH / g 0.10 OPO content, % 53.02 3-Chloropropanol ester, mg / kg 0.30 Glycidyl ester, mg / kg 0.14 Peroxide value, mmol / kg 0.37 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0053] Example 5

[0054] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155 ° C, the vacuum degree in the tower is 8 Pa, and the condenser temperature is 35 ° C. The heavy component of the distillation at the bottom of the tower is collected to obtain the concentrated OPO mixture. Glycerol, monostearate, and water are mixed and stored at a mass ratio of 90: 6: 4, and the promoter is mixed with the concentrated OPO mixture in a static mixer at an addition amount of 4 wt% of the heavy component, and then fed into the second-stage molecular distillation feed port, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160 ° C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35 ° C. After decolorization and deodorization, purified OPO is obtained, having the following qualities:

[0055] Table 5 Quality indicators of purified OPO obtained in Example 5

[0056] project Quality indicators Acid value, mg KOH / g 0.15 OPO content, % 53.04 3-Chloropropanol ester, mg / kg 0.35 Glycidyl ester, mg / kg 0.18 Peroxide value, mmol / kg 0.41 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0057] Example 6

[0058] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155 ° C, the vacuum degree in the tower is 8 Pa, and the condenser temperature is 35 ° C. The heavy components of the distillation at the bottom of the tower are collected to obtain the concentrated OPO mixture. Glycerol, monopalmitoyl glyceride, monostearate glyceride, monooleyl glyceride, monolinoleyl glyceride, and water are mixed and stored in a mass ratio of 88: 2.5: 2.5: 2.5: 2.5: 2.5: 2.5. The promoter is added in an amount of 4 wt% of the heavy component and mixed evenly with the concentrated OPO mixture in a static mixer, and then fed into the second-stage molecular distillation feed port, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160 ° C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35 ° C. After decolorization and deodorization, purified OPO is obtained, having the following qualities:

[0059] Table 6 Quality indicators of purified OPO obtained in Example 6

[0060] project Quality indicators Acid value, mg KOH / g 0.13 OPO content, % 53.55 3-Chloropropanol ester, mg / kg 0.32 Glycidyl ester, mg / kg 0.14 Peroxide value, mmol / kg 0.40 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0061] Comparative Example 1

[0062] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The temperature of the first-stage molecular distillation is controlled to be 200°C, the vacuum degree in the tower is 8 Pa, and the temperature of the condenser is 35°C. The heavy components distilled at the bottom of the tower are collected to obtain a concentrated OPO mixture. It is fed into the feed port of the second-stage molecular distillation, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 220°C, the vacuum degree in the tower is 0.1 Pa, and the temperature of the condenser is 35°C. The purified OPO obtained after decolorization and deodorization is tested according to the method described in Example 1, and has the following quality:

[0063] Table 7 Quality indicators of purified OPO obtained in Comparative Example 1

[0064] project Quality indicators Acid value, mg KOH / g 0.20 OPO content, % 46.67 3-Chloropropanol ester, mg / kg 0.92 Glycidyl ester, mg / kg 0.39 Peroxide value, mmol / kg 0.30 Color (Lovibond colorimetric trough 133.4mm) 1.4R / 22Y

[0065] Comparative Example 2

[0066] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The temperature of the first-stage molecular distillation is controlled to be 155°C, the vacuum degree in the tower is 8 Pa, and the temperature of the condenser is 35°C. The heavy components distilled at the bottom of the tower are collected to obtain a concentrated OPO mixture. It is fed into the feed port of the second-stage molecular distillation, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160°C, the vacuum degree in the tower is 0.1 Pa, and the temperature of the condenser is 35°C. After decolorization and deodorization, purified OPO is obtained, and the detection is carried out according to the method described in Example 1, and the quality is as follows:

[0067] Table 8 Quality indicators of purified OPO obtained in Comparative Example 2

[0068] project Quality indicators Acid value, mg KOH / g 1.82 OPO content, % 52.35 3-Chloropropanol ester, mg / kg 0.52 Glycidyl ester, mg / kg 0.25 Peroxide value, mmol / kg 0.40 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0069] Comparative Example 3

[0070] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The temperature of the first-stage molecular distillation is controlled to be 155 ° C, the vacuum degree in the tower is 8 Pa, and the temperature of the condenser is 35 ° C. The heavy component distilled at the bottom of the tower is collected to obtain a concentrated OPO mixture. Glycerol is used as a promoter and is added in an amount of 4 wt% of the heavy component to mix the concentrated OPO mixture in a static mixer, and then fed into the feed port of the second-stage molecular distillation. The remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 160 ° C, the vacuum degree in the tower is 0.1 Pa, and the temperature of the condenser is 35 ° C. After decolorization and deodorization, purified OPO is obtained, and the detection is carried out according to the method described in Example 1, and the following quality is obtained:

[0071] Table 9 Quality indicators of purified OPO obtained in Comparative Example 3

[0072] project Quality indicators Acid value, mg KOH / g 0.16 OPO content, % 53.13 3-Chloropropanol ester, mg / kg 0.50 Glycidyl ester, mg / kg 0.22 Peroxide value, mmol / kg 0.40 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0073] Comparative Example 4

[0074] In this embodiment, the mixed oil with the same acid value as that in Example 1 is fed into the feed port of the first-stage molecular distillation device, and most of the fatty acids, low-boiling components and impurities are evaporated by the first-stage molecular distillation. The first-stage molecular distillation temperature is controlled to be 155°C, the vacuum degree in the tower is 8Pa, and the condenser temperature is 35°C. The heavy components distilled at the bottom of the tower are collected to obtain the concentrated OPO mixture. Glycerol, monostearate, monopalmitoyl glyceride, and water are mixed and stored at 90:3.5:2.5:4, and the promoter is added in an amount of 10 wt% of the heavy components and the concentrated OPO mixture is mixed in a static mixer, and then fed into the second-stage molecular distillation feed port, and the remaining fatty acids and impurities are evaporated by the second-stage molecular distillation. The temperature of the second-stage molecular distillation is controlled to be 155°C, the vacuum degree in the tower is 0.1 Pa, and the condenser temperature is 35°C. After decolorization and deodorization, purified OPO is obtained, and the detection method described in Example 1 is carried out, and the quality is as follows:

[0075] Table 10 Quality indicators of purified OPO obtained in Comparative Example 4

[0076] project Quality indicators Acid value, mg KOH / g 0.42 OPO content, % 53.07 3-Chloropropanol ester, mg / kg 0.28 Glycidyl ester, mg / kg 0.13 Peroxide value, mmol / kg 0.42 Color (Lovibond colorimetric trough 133.4mm) <2.0R / 20Y

[0077] Experimental conclusion

[0078] From the comparison of the test data of Examples 1-6 and Comparative Examples 1-2, it can be seen that without adding a promoter, it is impossible to simultaneously ensure that the acid value of the purified OPO is ≤0.20 mg KOH / g, the OPO content is ≥53 wt%, 3-chloropropanol ester is ≤0.4 mg / kg, glycidyl ester is ≤0.2 mg / kg, the peroxide value is ≤0.5 mmol / kg, and the color (Lovibond colorimetric trough 133.4 mm) is ≤2.0R / 20Y. Although Comparative Example 1 significantly improves the acid value by simultaneously increasing the molecular distillation temperature twice, it also leads to a significant increase in the content of harmful substances 3-chloropropanol ester and glycidyl ester, and an increase in OPO refining loss. However, if no promoter is added in the second-stage molecular distillation and the distillation temperature is not increased, the acid value of the purified OPO cannot be significantly reduced.

[0079] From the comparison between Comparative Example 3 and Example 2, it can be seen that the addition of glycerol can improve the acid value to a certain extent, but the overall effect brought by the addition of glycerol alone is still inferior to that of Example 2, especially the addition of glycerol in Comparative Example 3 affects the content of OPO to a certain extent.

[0080] It can be seen from Comparative Example 4 that after adding too much extracting agent containing a mixture of glycerol, stabilizer and water, the temperature required for molecular distillation cannot be further reduced. When the molecular distillation temperature is too low, the free path of the distilled light component is less than the distance between the evaporation surface and the condensation surface, resulting in the inability to completely separate the light component, which increases the acid value.

[0081] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for purifying high acid value OPO mixed oil, characterized in that include: The high acid value OPO mixed oil is subjected to the first stage molecular distillation to obtain a heavy component, the heavy component is mixed with an extracting agent, and then subjected to the second stage molecular distillation to obtain purified OPO after decolorization and deodorization; The acid value of the high acid value OPO mixed oil is not less than 170 mg KOH / g; the amount of the extracting agent added is 1-8 wt % of the heavy component, and the extracting agent is composed of glycerol, monostearate glyceryl, monopalmitate glyceryl, and water in a mass ratio of 90:3.5:2.5:4; The distillation temperature of the first stage molecular distillation is 150-160°C, the condensation temperature is 30-40°C, and the vacuum degree is ≤10Pa; the distillation temperature of the second stage molecular distillation is 160-170°C, the condensation temperature is 30-40°C, and the vacuum degree is ≤1Pa.

2. A method for purifying a high acid value OPO mixed oil according to claim 1, characterized in that: The extracting agent comprises 80-95 wt% of glycerol, 0.1-10 wt% of a stabilizer and 0.1-10 wt% of water.

3. A method for purifying a high acid value OPO mixed oil according to claim 2, characterized in that: The stabilizers include glyceryl monopalmitate and glyceryl monostearate.

4. A method for purifying a high acid value OPO mixed oil according to any one of claims 1 to 3, characterized in that: The amount of the extracting agent added is 2-6 wt % of the heavy component.

5. A method for purifying a high acid value OPO mixed oil according to claim 1, characterized in that: The heavy component and the extracting agent are mixed evenly in a container and then subjected to a second stage molecular distillation.

6. A method for purifying a high acid value OPO mixed oil according to claim 1, characterized in that: The decolorization process comprises adding a decolorization adsorbent to the heavy component after the second-stage molecular distillation, and filtering out the decolorization adsorbent after heating and stirring.

7. A method for purifying a high acid value OPO mixed oil according to claim 1, characterized in that: The deodorization process is carried out in a deodorization tower and at least includes high-temperature deodorization and water vapor stripping.

8. A method for purifying a high acid value OPO mixed oil according to any one of claims 1-3, 5-6, characterized in that: The purified OPO also has the following characteristics: Acid value <0.20mg KOH / g; OPO content ≥53wt%; 3-chloropropanol ester ≤ 0.4 mg / kg; Glycidyl ester ≤ 0.2 mg / kg; Peroxide value ≤ 0.5mmol / kg; Color (Lovibond colorimetric trough 133.4mm) ≤2.0R / 20Y.