Preparation method of high-purity oleic acid
The urea inclusion method and solvent crystallization method were used in combination with ester solvents for low temperature crystallization and pressurized filtration, which solved the problem of large amount of urea and low yield in the preparation of high-purity oleic acid, and achieved the preparation of high-purity oleic acid.
Patent Information
- Application Number
- CN202510769545.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-10
- Publication Date
- 2025-08-05
AI Technical Summary
In the prior art, the preparation of high purity oleic acid has problems such as large amount of urea, low yield and urea residue in the product, which affects product quality and application.
The urea inclusion method and solvent crystallization method are used in combination with ester solvents for low-temperature crystallization and pressurized filtration, and the process steps are optimized to reduce the amount of urea and increase the yield of oleic acid.
The preparation of high-purity oleic acid is achieved, with a purity of more than 99%, solving the problems of urea residue and low yield and improving product quality.
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Figure CN120423949A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of oleic acid purification, in particular to a method for preparing high-purity oleic acid. Background Art
[0002] Oleic acid (chemical formula: C 18 H 34 Oleic acid (O2) is a biologically important ω-9 monounsaturated fatty acid (MUFA), systematically named (Z)-9-octadecenoic acid. As one of the most widely distributed unsaturated fatty acids in nature, its molecular structure contains a cis-configured C=C double bond (located at the Δ9 position). High-purity oleic acid appears as a colorless, transparent, oily liquid under standard conditions (25°C, 1atm) with extremely low volatility and no noticeable odor. The chemical stability of the unsaturated double bond in its molecular structure is significantly better than that of polyunsaturated fatty acids, and it exhibits excellent antioxidant and thermal stability, while also possessing good biocompatibility and safety. These properties make it an ideal industrial raw material and functional additive, with a wide range of applications in medicine, cosmetics, and food.
[0003] Currently, common oleic acid has a purity of 60-90%, often containing small amounts of other fatty acids such as stearic acid and linoleic acid. Due to the structural and physical properties of oleic acid being similar to those of stearic and linoleic acids, further separation from these fatty acids to obtain high-purity oleic acid presents significant challenges. Known methods for isolating high-purity oleic acid include urea adduct, solvent crystallization, supercritical extraction, molecular distillation, liquid chromatography, and enzymatic methods. Urea adduct and solvent crystallization have attracted attention due to their simple equipment and ease of operation, and their potential for industrial production. However, the urea adduct method reported so far suffers from issues such as high urea dosage, low oleic acid yield, and high levels of residual urea in the oleic acid product. Urea residue can darken the product color when synthesizing oleate emulsifiers, affecting product quality. While solvent crystallization avoids urea residue, it also suffers from low yield and purity.
[0004] Therefore, the preparation of oleic acid with a purity ≥99% still faces great challenges. How to obtain oleic acid at low cost, high purity and high yield is a key factor limiting the application of high-quality oleic acid. Summary of the Invention
[0005] The purpose of the present invention is to provide a method for preparing high-purity oleic acid in order to overcome the deficiencies of the prior art.
[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0007] The present invention provides a method for preparing high-purity oleic acid, comprising the following steps:
[0008] 1) mixing an oleic acid raw material, urea, and a solvent, and heating the mixture under reflux, cooling the refluxed product and subjecting the mixture to low-temperature crystallization to obtain a mixture;
[0009] 2) The mixture is filtered, the solvent is removed from the filtrate, and the filtrate is mixed with water. The pH value is adjusted to 2-4 with dilute acid, and then heated to separate the oil phase and the aqueous phase. The oil phase is separated while hot, and the aqueous phase is extracted. The organic phases are combined and dried, and the organic solvent is removed by distillation under reduced pressure to obtain an oily liquid;
[0010] 3) mixing the oily liquid with a solvent, and then performing low-temperature crystallization and pressure filtration to obtain high-purity oleic acid;
[0011] Step 3) The solvent is a short-chain ester solvent.
[0012] Preferably, the oleic acid raw material in step 1) is a free fatty acid with an oleic acid purity of ≤80%, and the solvent is a low-boiling point alcohol solvent.
[0013] Preferably, in step 1), the mass volume ratio of the oleic acid raw material, urea and solvent is 1 g: 1-2 g: 6-15 mL.
[0014] Preferably, the reflux temperature in step 1) is 70-100°C, the reflux product is cooled to room temperature, and the low-temperature crystallization temperature is -20-0°C.
[0015] Preferably, the solvent is removed from the filtrate in step 2) by distillation under reduced pressure, the volume ratio of water to the solvent in step 1) is 1:9 to 11, and the dilute acid comprises one or more of hydrochloric acid, sulfuric acid, phosphoric acid solution and citric acid solution.
[0016] Preferably, in step 3), the mass ratio of the oily liquid to the solvent is 1:0.5-2.
[0017] Preferably, the low-boiling point alcohol solvent is methanol and / or anhydrous ethanol, and the short-chain ester solvent comprises one or more of ethyl acetate, ethyl formate, methyl acetate, methyl formate, methyl propionate, ethyl propionate and propyl formate.
[0018] Preferably, the temperature of the low-temperature crystallization in step 3) is -20 to 0°C.
[0019] Preferably, the purity of the high-purity oleic acid is ≥99%.
[0020] The beneficial effects of the present invention include:
[0021] The present invention combines the urea inclusion method with the solvent crystallization method to reduce the amount of urea used, uses an ester solvent for the first time in key steps such as solvent crystallization, and achieves the preparation of oleic acid with a purity of ≥99%. The method of the present invention can effectively solve the problems of urea residue and low oleic acid yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is the gas chromatogram of the oleic acid standard sample (Hubei Ruitai Pharmaceutical Technology Co., Ltd., batch number N20240301);
[0023] Figure 2 This is a gas chromatogram of the high-purity oleic acid prepared in Example 1;
[0024] Figure 3 This is a gas chromatogram of the high-purity oleic acid prepared in Example 2;
[0025] Figure 4 This is the gas chromatogram of the high-purity oleic acid prepared in Example 3. DETAILED DESCRIPTION
[0026] The present invention provides a method for preparing high-purity oleic acid, comprising the following steps:
[0027] 1) mixing an oleic acid raw material, urea, and a solvent, and heating the mixture under reflux, cooling the refluxed product and subjecting the mixture to low-temperature crystallization to obtain a mixture;
[0028] 2) The mixture is filtered, the solvent is removed from the filtrate, and the filtrate is mixed with water. The pH value is adjusted to 2-4 with dilute acid, and then heated to separate the oil phase and the aqueous phase. The oil phase is separated while hot, and the aqueous phase is extracted. The organic phases are combined and dried to obtain an oily liquid;
[0029] 3) mixing the oily liquid with a solvent, and then performing low-temperature crystallization and pressure filtration to obtain high-purity oleic acid;
[0030] Step 3) The solvent is a short-chain ester solvent.
[0031] In the present invention, the oleic acid raw material in step 1) is preferably a free fatty acid with an oleic acid purity of ≤80%, and the solvent is preferably a low-boiling point alcohol solvent, and the low-boiling point alcohol solvent is preferably methanol and / or anhydrous ethanol.
[0032] In the present invention, the mass volume ratio of the oleic acid raw material, urea and solvent in step 1) is preferably 1 g: 1-2 g: 6-15 mL, more preferably 1 g: 1.2-1.8 g: 8-13 mL, and more preferably 1 g: 1.5-1.6 g: 10-12 mL.
[0033] In the present invention, the reflux temperature in step 1) is preferably 70 to 100°C, more preferably 80 to 90°C, and more preferably 85°C. The reflux product is preferably cooled to room temperature, and the temperature for low-temperature crystallization is preferably -20 to 0°C, more preferably -15 to -5°C, and more preferably -10°C.
[0034] In the present invention, step 1) is heated to reflux until the oleic acid raw material and urea are completely dissolved and then continued to stir and reflux to obtain a reflux product; the stirring and reflux time is preferably 0.3 to 1 hour, more preferably 0.5 hour, and the stirring and reflux rate is preferably 500 to 1000 r / min, more preferably 600 to 900 r / min, and more preferably 700 to 800 r / min.
[0035] In the present invention, the pressure of the suction filtration in step 2) is preferably -0.08 to -0.06 MPa, more preferably -0.07 MPa, and the filtrate is preferably distilled under reduced pressure to remove the solvent. The pressure of the distillation under reduced pressure is preferably -0.09 to -0.07 MPa, more preferably -0.08 MPa, and the temperature is preferably 45 to 55°C, more preferably 50°C. The volume ratio of the water to the solvent in step 1) is preferably 1:9 to 11, more preferably 1:9.5 to 10.5, and more preferably 1:10. The dilute acid preferably comprises one or more of hydrochloric acid, sulfuric acid, phosphoric acid solution, and citric acid solution. The concentration of the dilute acid is preferably 0.4 to 0.6 mol / L, more preferably 0.45 to 0.55 mol / L, and more preferably 0.5 mol / L. The heating temperature is preferably 60 to 80°C, more preferably 70°C. The solid is completely dissolved by heating, stirring is stopped, and the oil phase and the aqueous phase are separated.
[0036] In the present invention, the organic phase obtained by extracting the aqueous phase in step 2) is combined with petroleum ether and then dried. The number of times the aqueous phase is extracted is preferably 2 to 4 times, more preferably 3 times. The reagent used for extraction is preferably petroleum ether, and the reagent used for drying is preferably anhydrous sodium sulfate.
[0037] In the present invention, the short-chain ester solvent in step 3) preferably comprises one or more of ethyl acetate, ethyl formate, methyl acetate, methyl formate, methyl propionate, ethyl propionate and propyl formate.
[0038] In the present invention, the mass ratio of the oily liquid to the solvent in step 3) is preferably 1:0.5-2, more preferably 1:0.8-1.6, and even more preferably 1:1-1.3.
[0039] In the present invention, the temperature of the low-temperature crystallization in step 3) is preferably -20 to 0°C, more preferably -15 to -5°C, and more preferably -10°C; the time of low-temperature crystallization is preferably 11 to 13 hours, more preferably 12 hours; the temperature of the pressurized filtration is preferably -15 to -5°C, more preferably -10°C, and the pressure is preferably 0.05 to 0.2 MPa, more preferably 0.1 to 0.15 MPa.
[0040] In the present invention, the pressure filtration in step 3) obtains solid crystals, which are then warmed to above 10° C. to obtain high-purity oleic acid.
[0041] In the present invention, the purity of the high-purity oleic acid is preferably ≥99%, more preferably ≥99.2%, and even more preferably ≥99.5%.
[0042] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0043] Example 1
[0044] Add 50 g of free fatty acid (oleic acid purity is 78%) and 100 g of urea to 500 mL of anhydrous ethanol, heat and reflux at 80°C, heat and reflux until the free fatty acid and urea are completely dissolved, continue stirring (speed is 800 r / min) and reflux for 0.5 h, then pour into a beaker and cool naturally to room temperature, and place at -10°C for low-temperature crystallization.
[0045] The mixture after crystallization was filtered (pressure of -0.06 MPa), and the filtrate obtained by filtration was subjected to reduced pressure distillation (-0.08 MPa, heating at 50°C) to remove anhydrous ethanol, and then 50 mL of water was added, and phosphoric acid solution (0.5 mol / L) was added to adjust the pH value of the system to 4. After that, the solid was heated at 70°C to completely dissolve. Stirring was stopped, and the oil phase and the aqueous phase were separated. The upper oil phase was separated while hot, and the remaining aqueous phase was extracted three times with petroleum ether. The upper oil phase was combined with petroleum ether, dried over anhydrous sodium sulfate, filtered, and distilled under reduced pressure (-0.08 MPa) to remove petroleum ether to obtain 42.29 g of a light yellow oily liquid.
[0046] The obtained 42.29 g oily liquid was mixed with 42.29 g ethyl acetate and placed at -15°C for low-temperature crystallization for 12 h. The mixture was filtered under pressure at -15°C and 0.1 MPa to obtain solid crystals. The mixture was warmed to above 10°C to obtain 24.77 g colorless and odorless oily liquid.
[0047] The colorless and odorless oily liquid in this embodiment is high-purity oleic acid, and its purity is 99.19% as determined by gas chromatography (GC).
[0048] Example 2
[0049] Add 50 g of free fatty acid (oleic acid purity is 76%) and 75 g of urea to 500 mL of anhydrous ethanol, heat and reflux at 80°C, heat and reflux until the free fatty acid and urea are completely dissolved, continue stirring (speed is 700 r / min) and reflux for 0.5 h, then pour into a beaker and cool naturally to room temperature, and place at -15°C for low-temperature crystallization.
[0050] The mixture after crystallization was filtered, and the filtrate obtained by filtration (pressure of -0.07 MPa) was subjected to reduced pressure distillation (-0.08 MPa, heating at 50°C) to remove anhydrous ethanol, and then 50 mL of water was added, and citric acid solution (0.5 mol / L) was added to adjust the pH value of the system to 4. After that, the solid was heated at 65°C to completely dissolve. Stirring was stopped, and the oil phase and the aqueous phase were separated. The upper oil phase was separated while hot, and the remaining aqueous phase was extracted three times with petroleum ether. The upper oil phase was combined with petroleum ether, dried over anhydrous sodium sulfate, filtered, and distilled under reduced pressure (-0.08 MPa) to remove petroleum ether to obtain 42.98 g of a light yellow oily liquid.
[0051] The obtained 42.98 g oily liquid was mixed with 42.98 g ethyl formate, placed at -5°C for low-temperature crystallization for 12 h, and pressure filtered at -5°C and 0.08 MPa to obtain solid crystals. The mixture was warmed to above 10°C to obtain 27.38 g colorless and odorless oily liquid.
[0052] The colorless and odorless oily liquid in this embodiment is high-purity oleic acid, and its purity is 99.36% as determined by GC.
[0053] Example 3
[0054] Add 50 g of free fatty acid (oleic acid purity is 78%) and 75 g of urea to 500 mL of anhydrous ethanol, heat and reflux at 75°C, heat and reflux until the free fatty acid and urea are completely dissolved, continue stirring (speed is 900 r / min) and reflux for 0.5 h, then pour into a beaker and cool naturally to room temperature, and place at -15°C for low-temperature crystallization.
[0055] The mixture after crystallization was filtered, and the filtrate obtained by filtration (pressure of -0.08 MPa) was subjected to reduced pressure distillation (-0.08 MPa, heating at 50°C) to remove anhydrous ethanol, and then 50 mL of water was added, and a dilute hydrochloric acid solution (0.5 mol / L) was added to adjust the pH value of the system to 4. After that, the solid was heated at 75°C to completely dissolve. Stirring was stopped, and the oil phase and the aqueous phase were separated. The upper oil phase was separated while hot, and the remaining aqueous phase was extracted three times with petroleum ether. The upper oil phase was combined with petroleum ether, dried over anhydrous sodium sulfate, filtered, and distilled under reduced pressure (-0.08 MPa) to obtain 41.78 g of a light yellow oily liquid.
[0056] The obtained 41.78 g oily liquid was mixed with 41.78 g methyl acetate, placed at -10°C for low-temperature crystallization for 12 h, and pressure filtered at -10°C and 0.15 MPa to obtain solid crystals. The mixture was warmed to above 10°C to obtain 24.35 g colorless and odorless oily liquid.
[0057] The colorless and odorless oily liquid in this embodiment is high-purity oleic acid, and its purity is 99.21% as determined by GC.
[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.
Claims
1. A method for preparing high-purity oleic acid, characterized in that: The following steps are included: 1) mixing an oleic acid raw material, urea, and a solvent, and heating the mixture under reflux, cooling the refluxed product and subjecting the mixture to low-temperature crystallization to obtain a mixture; 2) The mixture is filtered, the solvent is removed from the filtrate, and the filtrate is mixed with water. The pH value is adjusted to 2-4 with dilute acid, and then heated to separate the oil phase and the aqueous phase. The oil phase is separated while hot, and the aqueous phase is extracted. The organic phases are combined and dried, and the organic solvent is removed by distillation under reduced pressure to obtain an oily liquid; 3) mixing the oily liquid with a solvent, and then performing low-temperature crystallization and pressure filtration to obtain high-purity oleic acid; Step 3) The solvent is a short-chain ester solvent.
2. The preparation method according to claim 1, characterized in that In step 1), the oleic acid raw material is free fatty acid with an oleic acid purity of ≤80%, and the solvent is a low-boiling point alcohol solvent.
3. The preparation method according to claim 1 or 2, characterized in that In step 1), the mass volume ratio of the oleic acid raw material, urea and solvent is 1 g: 1-2 g: 6-15 mL.
4. The preparation method according to claim 3, characterized in that In step 1), the reflux temperature is 70-100° C., the reflux product is cooled to room temperature, and the low-temperature crystallization temperature is -20-0° C.
5. The preparation method according to claim 4, characterized in that Step 2) The filtrate is subjected to reduced pressure distillation to remove the solvent, the volume ratio of the water to the solvent in step 1) is 1:9-11, and the dilute acid comprises one or more of hydrochloric acid, sulfuric acid, phosphoric acid solution and citric acid solution.
6. The preparation method according to claim 4 or 5, characterized in that Step 3) The mass ratio of the oily liquid to the solvent is 1:0.5-2.
7. The preparation method according to claim 6, characterized in that The low-boiling point alcohol solvent is methanol and / or anhydrous ethanol, and the short-chain ester solvent includes one or more of ethyl acetate, ethyl formate, methyl acetate, methyl formate, methyl propionate, ethyl propionate and propyl formate.
8. The preparation method according to claim 7, characterized in that Step 3) The temperature of the low-temperature crystallization is -20 to 0°C.
9. The preparation method according to claim 1 or 8, characterized in that The purity of the high-purity oleic acid is ≥99%.