Supercritical CO2 sunflower seed oil green low-temperature refining process

Abstract

The invention relates to the technical field of grease processing and refining, and discloses a supercritical CO2 sunflower seed oil green low-temperature refining process which comprises the following steps: performing continuous tube type mild degumming on sunflower seed crude oil to obtain degummed oil; in a continuous counter-current extraction tower, carrying out deacidification extraction by adopting supercritical carbon dioxide combined with a variable-frequency pulse injection entrainer; introducing the obtained homogeneous fluid into a high-pressure fixed bed at the same temperature and under the same pressure, and carrying out penetrating decoloration by using a spherical mesoporous composite adsorbent; carrying out stepped decompression separation on the decolorized fluid to obtain refined base oil, and carrying out continuous deodorization on the refined base oil to obtain finished refined oil; carrying out short-path molecular distillation on the deodorized distillate to separate free fatty acid and recover vitamin E and phytosterol; and carrying out in-situ desorption regeneration on the saturated adsorbent by utilizing transient stepped pressure relief. According to the method, grease saponification loss and waste white clay pollution caused by traditional chemical alkali refining are avoided, and heat-sensitive micronutrient adjuncts are effectively intercepted and enriched through low-temperature operation in the whole process.

Description

Technical Field

[0001] This invention relates to the field of oil processing and refining technology, specifically a supercritical CO2 sunflower seed oil green low-temperature refining process. Background Technology

[0002] Sunflower seed oil contains a large amount of unsaturated fatty acids, as well as micronutrients such as vitamin E and phytosterols. Currently, the industrial refining process of sunflower seed oil mainly relies on traditional processes such as chemical alkali refining, bleaching clay decolorization, and high-temperature deodorization. These conventional processes have obvious technical defects in terms of material yield, environmental protection, and product nutrient retention.

[0003] In the conventional deacidification process, chemical alkali solutions are usually added to neutralize the free fatty acids in crude oil. This operation is very likely to trigger the saponification reaction of neutral oils, resulting in the absolute loss of neutral oils and reducing the final yield of finished oil. At the same time, the neutralization reaction will produce a large amount of highly concentrated polluting soap residue, which will significantly increase the pressure on wastewater and solid waste treatment in the front-end processes of the factory.

[0004] In the subsequent decolorization stage, existing processes mostly use the direct addition of high-temperature activated clay for pigment adsorption. After the clay becomes saturated, its pore structure solidifies, making it difficult to effectively desorb and regenerate. A large amount of waste clay can only be treated directly as industrial solid waste, which not only brings a serious environmental burden, but also adsorbs and carries some oil in the waste clay, further aggravating the resource consumption in the overall processing.

[0005] In the deodorization stage at the end, conventional processes rely on high-temperature steam for low-pressure stripping. The continuous high-temperature thermal environment easily induces thermal oxidation and deterioration of lipids, leading to the formation of trans fatty acids. The heat-sensitive antioxidants naturally abundant in sunflower seed oil will be degraded and consumed in large quantities under the action of high temperature for a long time. Existing equipment is difficult to achieve the non-destructive separation and recycling of high-value-added nutrients in the distillate while separating volatile odor molecules. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a green low-temperature refining process for sunflower seed oil using supercritical CO2. This process solves the problems of neutral oil saponification loss and large-scale soap residue pollution caused by chemical alkali refining in traditional refining processes, solid waste burden caused by the non-renewable waste clay, and lipid thermal oxidation and deterioration and large-scale consumption of heat-sensitive nutrients caused by high-temperature operation.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A green low-temperature refining process for sunflower seed oil using supercritical CO2 includes the following steps:

[0009] Sunflower seed crude oil was subjected to continuous tubular gentle degumming, and the hydrated oil residue was separated by centrifugation to obtain degummed oil.

[0010] The degummed oil is fed into a continuous countercurrent extraction tower, supercritical carbon dioxide fluid is introduced, and an entrainer is injected in a periodic frequency-variable pulse mode to perform deacidification extraction and obtain a homogeneous fluid containing neutral oil and dissolved carbon dioxide.

[0011] The homogeneous fluid containing neutral oil and dissolved carbon dioxide is directly introduced into a high-pressure fixed bed filled with spherical mesoporous composite adsorbent under the same temperature and pressure conditions, and continuously penetrates the bed layer for decolorization to obtain the decolorized fluid.

[0012] The decolorized fluid is subjected to step decompression analysis to separate gaseous carbon dioxide and liquid refined base oil. The gaseous carbon dioxide is then compressed and recycled.

[0013] The liquid-phase refined base oil is continuously deodorized, the deodorized distillate obtained by condensation at the top of the column is collected, and the finished refined oil is collected at the bottom of the column;

[0014] The deodorized distillate was subjected to short-path molecular distillation to separate free fatty acids and recover the product enriched with vitamin E and phytosterols.

[0015] For spherical mesoporous composite adsorbents that have reached adsorption saturation, after static immersion in supercritical carbon dioxide fluid, transient step depressurization is implemented to carry out in-situ desorption and regeneration.

[0016] By adopting the above technical solution, since supercritical carbon dioxide is used as the extraction and decolorization medium, the oil system is in a low-temperature and oxygen-free environment throughout the deacidification and decolorization stages. The supercritical fluid has high solubility and high mass transfer coefficient, directly dissolving and separating free fatty acids, avoiding the saponification loss of oil caused by chemical strong alkali neutralization reaction. The degummed oil and the supercritical fluid containing the entrainer undergo mass transfer in the countercurrent extraction tower. The fluid after the removal of free fatty acids directly enters the high-pressure fixed bed at the same temperature and pressure, maintaining the continuity of the system's fluid dynamics and avoiding energy loss caused by intermediate pressure reduction. The saturated adsorbent undergoes physical desorption through in-situ transient step depressurization, using the volume expansion force generated by the fluid phase change to peel off impurities in the pores, restoring the internal pore structure of the material, avoiding the one-time waste problem of traditional decolorizing clay, and realizing closed-loop clean production of the entire refining process.

[0017] Preferably, the specific operation for continuous tubular gentle degumming of sunflower seed crude oil is as follows:

[0018] Crude sunflower seed oil is heated to 45-55℃ through a heat exchange system. An 85% phosphoric acid aqueous solution is injected along the pipeline, with the amount of phosphoric acid aqueous solution added controlled at 0.1-0.3% of the crude oil mass. The fluid remains in the pipeline for 15-30 minutes to react. Then, 1-3% of the crude oil mass of pure water is injected and the mixture is introduced into a stirred tank for hydration reaction at 40-60 rpm for 20-40 minutes. Finally, the hydrated oil residue is separated by continuous centrifugation using a disc centrifuge.

[0019] By adopting the above technical solution, the hydrogen ions ionized from the phosphoric acid aqueous solution replace the calcium or magnesium ions in the non-hydrated phospholipid molecules, converting them into hydrated phospholipids. The generated hydrated phospholipids have hydrophilic groups and absorb water and swell under the action of pure water and mechanical stirring to form micelle aggregates with a large specific gravity. Subsequently, the hydrated oil residue and degummed oil are physically separated by the action of centrifugal force field, removing the gum from the oil system.

[0020] Preferably, during deacidification extraction, the system pressure of the continuous countercurrent extraction tower is controlled at 15.0-28.0 MPa, the temperature is controlled at 35-55℃, and the gas-liquid mass ratio is maintained at 5-15:1.

[0021] The variable frequency pulse injection mode of the entrainer is as follows: a complete injection cycle is set to 3-5 minutes. During the first 30-35% of the cycle, the entrainer injection flow rate accounts for 4.0% of the total fluid mass, and during the remaining time period of the cycle, the entrainer injection flow rate accounts for 0-1.0% of the total fluid mass.

[0022] By adopting the above technical solution, the periodic variable frequency pulse injection mode breaks the steady-state concentration boundary layer on the liquid surface. During the high-concentration entrainer injection stage, a surface tension gradient is induced at the gas-liquid interface, which induces the Marangoni convection phenomenon at the interface and enhances local mass transfer turbulence. During the low-concentration injection stage, the system restores the normal concentration gradient diffusion, which improves the mass transfer flux of free fatty acids from the liquid phase to the supercritical fluid phase and improves the deacidification kinetic rate in the later stage of the reaction.

[0023] Preferably, the entrainer is a mixture of components comprising the following weight percentages:

[0024] Main solvent 88-95%;

[0025] Organic acids 2-2.5%;

[0026] Emulsifier 3-10%;

[0027] The main solvent is anhydrous ethanol or isopropanol, the organic acid is citric acid or ascorbic acid, and the emulsifier is glyceryl monostearate, polysorbate-80, or diglyceryl monostearate.

[0028] By employing the above technical solutions, anhydrous ethanol or isopropanol alters the overall polarity of the supercritical carbon dioxide system, increasing its dissolution capacity for polar free fatty acids. Organic acids, acting as metal chelating agents, passivate trace free metal ions in the lipid microenvironment, blocking the catalytic sites of lipid oxidation chain reactions. Emulsifiers reduce interphase tension, decrease the size of dispersed droplets, and increase the interphase mass transfer contact area.

[0029] Preferably, during decolorization, the residence time of the homogeneous fluid containing neutral oil and dissolved carbon dioxide in the high-pressure fixed bed filled with spherical mesoporous composite adsorbent is controlled to be 20-40 minutes.

[0030] By adopting the above technical solution, the required residence time is provided to allow macromolecular pigment groups to diffuse into the pores of the adsorbent and complete chemical site binding, thus ensuring the pigment removal rate after the fluid penetrates the adsorption bed.

[0031] Preferably, the preparation method of the spherical mesoporous composite adsorbent includes:

[0032] Chitosan with a degree of deacetylation of 85-95% is dissolved in an aqueous solution of glacial acetic acid with a volume concentration of 1.0-2.0% to prepare a chitosan gel solution with a mass concentration of 2-4%.

[0033] Tetraethyl orthosilicate and anhydrous ethanol were mixed at a volume ratio of 1:(1-3), and 20-30% of the volume of tetraethyl orthosilicate in deionized water was added. The pH of the system was adjusted to 2.0-3.0 by adding 0.1mol / L hydrochloric acid solution dropwise. The mixture was stirred at 300-500rpm for 1-2 hours at 40-50℃ to obtain silica sol.

[0034] The chitosan solution is added dropwise to the silica sol at a rate of 5-10 mL / min. Sodium alginate of 1-2% of the dry weight of chitosan is added, and genipin aqueous solution of 1-5% of the dry weight of chitosan and a mass concentration of 0.5-1.5% is added as a crosslinking agent. The mixture is stirred at 150-250 rpm at 50-60°C for 2-3 hours to form a semi-gel.

[0035] The semigel was dripped through a dropper with a diameter of 1-3 mm into a coagulation bath containing 2% anhydrous calcium chloride at 0-5°C and solidified to obtain spherical gel particles.

[0036] The spherical gel particles were aged at room temperature for 12-24 hours and repeatedly washed until neutral. They were then pre-frozen at -60°C to -40°C and subsequently freeze-dried under vacuum at an absolute pressure of 10-30 Pa for 24-48 hours to obtain the spherical mesoporous composite adsorbent.

[0037] By employing the above technical solution, the preparation process constructs an interpenetrating polymer network structure of chitosan and silica. The silica sol formed by the hydrolysis and condensation of tetraethyl orthosilicate provides a rigid inorganic framework, preventing volume deformation of the material under long-term scouring by high-pressure fluid. The natural small molecule genipin undergoes covalent cross-linking with the amino groups on the chitosan molecular chain, enhancing the chemical stability of the polymer network. Calcium chloride in the coagulation bath initiates ionic cross-linking and solidification of sodium alginate, maintaining the macroscopic morphology of the spheres. The vacuum freeze-drying step allows the solid ice inside the gel to sublimate directly, avoiding pore collapse caused by capillary contraction during conventional drying processes and preserving abundant internal mesopores. Pigment molecules enter the mesopores under the influence of the fluid and undergo hydrogen bonding association with the abundant hydroxyl and amino groups on the framework surface, completing adsorption and decolorization.

[0038] Preferably, the specific operation of performing step-depressurization analysis on the decolorized fluid is as follows:

[0039] The decolorized fluid enters the separation system. The pressure in the primary separation vessel is controlled at 8-12 MPa and the temperature at 40-50℃. The pressure in the secondary separation vessel is controlled at 4-6 MPa and the temperature at 30-40℃.

[0040] By adopting the above technical solution, the depressurization operation changes the fluid density of supercritical carbon dioxide, weakens its solubility, and the two-stage depressurization process causes the refined base oil to precipitate in the liquid phase due to a sharp decrease in solubility. After the gaseous carbon dioxide completes phase separation, its purity is improved, and after being repressurized by the compressor, it returns to the front end of the system to form a closed loop.

[0041] Preferably, during continuous deodorization, the absolute pressure inside the deodorization tower is maintained at 150-350 Pa, the temperature of the heat transfer oil in the heating section is controlled at 175-195℃, the stripping section of the deodorization tower is filled with corrugated structured packing with a specific surface area of ​​250-350 square meters per cubic meter, and direct steam at a dosage of 0.5-1.5% of the oil weight is introduced from the bottom of the tower. The total residence time of the oil in the tower is 60-100 minutes.

[0042] By adopting the above technical solution, operating under extremely low absolute vacuum pressure, the boiling point of small molecule odor volatiles is reduced. The corrugated and regular packing provides a high specific surface area, causing the liquid phase oil to be distributed downward in a thin film. The direct steam introduced in reverse at the bottom reduces the partial pressure of volatile components in the vapor phase, driving odor molecules to transfer from the liquid film boundary layer to the main gas phase. The upper limit of the deodorization temperature is controlled at 195℃. While meeting the physical separation requirements of stripping deodorization, it avoids the oil isomerization phenomenon and the pyrolysis consumption of antioxidants such as tocopherol caused by traditional high-temperature processes.

[0043] Preferably, the specific operation of short-path molecular distillation treatment of the deodorized distillate is as follows:

[0044] The deodorized distillate was pre-degassed for 10-20 minutes under a vacuum of 1-2 kPa and a temperature of 60-80°C.

[0045] The material enters a first-stage short-path molecular distillation, with an evaporation surface temperature of 120-140℃, a system vacuum of 5-20Pa, and a film-forming scraper speed of 200-350rpm, separating light components of free fatty acids.

[0046] The remaining heavy components enter a second-stage short-path molecular distillation process. The evaporation surface temperature is 180-210℃, the system vacuum is 0.1-1.0Pa, and the film-forming scraper speed is 250-400rpm. The light phase on the second-stage condenser surface is collected to obtain a product enriched with vitamin E and phytosterols.

[0047] By adopting the above technical solution, short-path molecular distillation separates different substances by utilizing the difference in the mean free path of molecular thermal motion. In the first stage, under a high vacuum, light components of free fatty acids with a large mean free path and a low boiling point are separated. In the second stage, the system enters an extremely high vacuum state, which further reduces the operating temperature of the material. Natural vitamin E and phytosterols in the heavy components are released from the evaporation surface by molecular thermal motion and liquefied and collected on the secondary condensation surface within a very short distance. The entire process maintains pure physical separation, avoids the introduction of chemical reagents, and protects the biological activity of trace high-value products.

[0048] Preferably, the specific operation for in-situ desorption and regeneration is as follows:

[0049] Introduce pure supercritical carbon dioxide fluid at a temperature of 50-60℃ and a pressure of 20-25MPa, and statically immerse the high-pressure fixed bed for 15-20 minutes.

[0050] Turn on the fixed bed jacket heat exchange system and introduce waste heat steam at 110-130℃;

[0051] Implement the first step pressure relief, adjust the pressure relief valve to reduce the fluid pressure inside the bed to 8-10 MPa within 1-2 minutes, and maintain the pressure for 1 minute;

[0052] Implement a second step-by-step depressurization, further reducing the pressure to 1.0-2.0 MPa within 2-3 minutes;

[0053] Repressurize to 20-25 MPa and repeat the above two-step depressurization operation 2-3 times;

[0054] Finally, waste heat steam at 110-130℃ is directly introduced into the fixed bed and purged for 30-60 minutes at atmospheric pressure.

[0055] By adopting the above technical solution, static soaking allows supercritical carbon dioxide fluid to fully penetrate the interconnected mesoporous network inside the composite adsorbent, contacting the adsorbed impurity molecules and establishing a preliminary dissolution equilibrium. After introducing waste heat steam to raise the bed temperature and implementing transient step-by-step depressurization, the fluid pressure drops below the critical point in a short time. The liquid carbon dioxide existing deep in the pores undergoes an instantaneous vaporization phase change, and its volume expands dramatically. The expansion backlash generates a mechanical stripping effect, destroying the intermolecular forces between the impurity macromolecules and the adsorption framework, forcibly expelling the impurities from the pores. Repeating the two-step depressurization operation removes the stubborn blockages deep in the pores, maintaining the long-term regeneration performance of the adsorbent material.

[0056] This invention provides a green, low-temperature refining process for sunflower seed oil using supercritical CO2. It offers the following advantages:

[0057] 1. This invention uses supercritical carbon dioxide combined with variable frequency pulse injection entrainer for deacidification extraction, replacing the traditional chemical alkali refining process. This avoids the saponification of neutral oils caused by the neutralization reaction of free fatty acids with alkali solution, reduces the absolute loss rate of neutral oils in the refining process, improves the yield of finished refined oil, cuts off the generation pathway of a large amount of polluting soap residue in the traditional hydration and alkali refining process, and reduces the pressure of subsequent wastewater and solid waste treatment.

[0058] 2. This invention uses a high-pressure fixed bed filled with spherical mesoporous composite adsorbent for continuous decolorization, and utilizes transient step depressurization of the fluid to implement in-situ desorption and regeneration. In-situ desorption utilizes the physical expansion and recoil force generated during the transient depressurization phase change of the supercritical fluid to peel off and remove pigment macromolecules and impurities from the deep pores of the adsorbent, restoring the effective pore volume of the material. This replaces the traditional high-temperature bleaching clay decolorization process, solves the problem of solid waste pollution caused by the difficulty in disposing of large amounts of waste bleaching clay, and realizes the long-term recycling of mesoporous decolorizing materials.

[0059] 3. This invention couples ultra-low pressure low-temperature deodorization with short-path molecular distillation to classify refined base oil and deodorized distillate. The mild thermal environment below 195°C combined with high-vacuum physical separation avoids the lipid thermal oxidation and deterioration and trans fatty acid formation caused by traditional high-temperature operations, protects and retains the natural heat-sensitive antioxidants in the finished oil, and utilizes the difference in the mean free path of molecular thermal motion to perform two-stage short-path molecular distillation on the distillate, achieving the non-destructive separation and centralized recovery of natural vitamin E and phytosterols. Attached Figure Description

[0060] Figure 1 This is a comparison graph showing the change in residual acid value with extraction time in Test Example 1 of the present invention;

[0061] Figure 2This is a comparison graph showing the change in free fatty acid removal rate with extraction time for Test Example 1 of the present invention;

[0062] Figure 3 This is a comparison graph showing the change in peroxide value over treatment time in Test Example 2 of the present invention;

[0063] Figure 4 This is a comparison graph showing the change in vitamin E retention rate over treatment time in Test Example 2 of the present invention;

[0064] Figure 5 This is a comparison graph showing the change in single-cycle desorption rate with the number of cycles in Test Example 3 of the present invention;

[0065] Figure 6 This is a comparison graph showing the change in adsorption capacity retention rate with the number of cycles in Test Example 3 of the present invention;

[0066] Figure 7 This is a bar chart comparing the absolute loss rate of neutral oil in Test Example 4 of the present invention;

[0067] Figure 8 This is a bar chart comparing the conventional physicochemical removal effects of Test Example 4 of the present invention.

[0068] Figure 9 This is a comparative bar chart showing the absolute total amount of nutrient companion substances in the finished oil of Test Example 5 of the present invention;

[0069] Figure 10 This is a comparative bar chart showing the retention rates of the nutrient companion system in Test Example 5 of the present invention. Detailed Implementation

[0070] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] Preparation Examples 1-3:

[0072] Preparation Example 1:

[0073] This preparation example provides a method for preparing a high-strength spherical mesoporous composite adsorbent, including the following steps:

[0074] Chitosan with a degree of deacetylation of 85% was dissolved in a 1.0% (v / v) aqueous solution of glacial acetic acid and stirred evenly at room temperature to prepare a 2% (w / w) chitosan gel solution.

[0075] Tetraethyl orthosilicate and anhydrous ethanol were mixed at a volume ratio of 1:1. Deionized water at a volume equal to 20% of the tetraethyl orthosilicate was added, and the pH of the system was adjusted to 2.0 by adding 0.1 mol / L hydrochloric acid solution dropwise. The mixture was stirred at 300 rpm for 1 hour at a constant temperature of 40°C to obtain silica sol.

[0076] The chitosan gel solution was added dropwise to the silica sol at a rate of 5 mL / min. After the addition was complete, sodium alginate (1% by weight of chitosan dry weight) was added to the mixture. After stirring evenly, a 0.5% genipin aqueous solution was added as a crosslinking agent, with the pure amount of the crosslinking agent added being 1% of the chitosan dry weight. The system was placed at 50°C and stirred at 150 rpm for 2 hours to form a semi-gel state.

[0077] The semigel was dripped uniformly through a 1mm orifice nozzle into an anhydrous ethanol coagulation bath containing 2% anhydrous calcium chloride. The temperature of the coagulation bath was controlled at 0℃, and spherical gel particles were obtained after solidification.

[0078] The collected spherical gels were allowed to age at room temperature for 12 hours. They were first washed twice with anhydrous ethanol to remove impurities, then repeatedly washed with deionized water until the pH of the washing solution was neutral, ensuring that the solvent inside the gel was completely replaced by water. The washed gel spheres were pre-frozen at -40°C, then transferred to a vacuum freeze dryer and dried for 24 hours under a system absolute pressure of 10 Pa to obtain the formed spherical mesoporous composite adsorbent.

[0079] Preparation Example 2:

[0080] This preparation example provides a method for preparing a high-strength spherical mesoporous composite adsorbent, including the following steps:

[0081] Chitosan with a degree of deacetylation of 90% was dissolved in a 1.5% (v / v) aqueous solution of glacial acetic acid and stirred evenly at room temperature to prepare a chitosan gel solution with a mass concentration of 3%.

[0082] Tetraethyl orthosilicate and anhydrous ethanol were mixed at a volume ratio of 1:2. Deionized water at a volume of 25% of the tetraethyl orthosilicate was added, and the pH of the system was adjusted to 2.5 by adding 0.1 mol / L hydrochloric acid solution dropwise. The mixture was stirred at 400 rpm for 1.5 hours at a constant temperature of 45°C to obtain silica sol.

[0083] The chitosan gel solution was added dropwise to the silica sol at a rate of 7.5 mL / min. After the addition was complete, sodium alginate (1.5% by weight of chitosan dry weight) was added to the mixture. After stirring evenly, a 1.0% genipin aqueous solution was added as a crosslinking agent, with the pure amount of the crosslinking agent being 3% of the chitosan dry weight. The system was placed at 55°C and stirred at 200 rpm for 2.5 hours to form a semi-gel state.

[0084] The semigel was dripped uniformly through a 2mm orifice nozzle into an anhydrous ethanol coagulation bath containing 2% anhydrous calcium chloride. The temperature of the coagulation bath was controlled at 2.5℃, and spherical gel particles were obtained after solidification.

[0085] The collected spherical gels were allowed to age at room temperature for 18 hours. They were first washed twice with anhydrous ethanol to remove impurities, then repeatedly washed with deionized water until the pH of the washing solution was neutral, ensuring that the solvent inside the gel was completely replaced by water. The washed gel spheres were pre-frozen at -50°C, then transferred to a vacuum freeze dryer and dried for 36 hours under a system absolute pressure of 20 Pa to obtain the formed spherical mesoporous composite adsorbent.

[0086] Preparation Example 3:

[0087] This preparation example provides a method for preparing a high-strength spherical mesoporous composite adsorbent, including the following steps:

[0088] Chitosan with a degree of deacetylation of 95% was dissolved in a 2.0% (v / v) aqueous solution of glacial acetic acid and stirred evenly at room temperature to prepare a chitosan gel solution with a mass concentration of 4%.

[0089] Tetraethyl orthosilicate and anhydrous ethanol were mixed at a volume ratio of 1:3. Deionized water at a volume equal to 30% of the tetraethyl orthosilicate was added, and the pH of the system was adjusted to 3.0 by adding 0.1 mol / L hydrochloric acid solution dropwise. The mixture was stirred at 500 rpm for 2 hours at a constant temperature of 50°C to obtain silica sol.

[0090] The chitosan solution was added dropwise to the silica sol at a rate of 10 mL / min. After the addition was complete, sodium alginate (2% by weight of chitosan dry weight) was added to the mixture. After stirring evenly, a 1.5% genipin aqueous solution was added as a crosslinking agent, with the pure amount of the crosslinking agent added being 5% of the chitosan dry weight. The system was placed at 60°C and stirred at 250 rpm for 3 hours to form a semi-gel state.

[0091] The semigel was dripped uniformly through a 3mm orifice nozzle into an anhydrous ethanol coagulation bath containing 2% anhydrous calcium chloride. The temperature of the coagulation bath was controlled at 5℃, and spherical gel particles were obtained after solidification.

[0092] The collected spherical gels were allowed to age at room temperature for 24 hours. They were first washed twice with anhydrous ethanol to remove impurities, then repeatedly washed with deionized water until the pH of the washing solution was neutral, ensuring that the solvent inside the gel was completely replaced by water. The washed gel spheres were pre-frozen at -60°C, then transferred to a vacuum freeze dryer and dried for 48 hours under a system absolute pressure of 30 Pa to obtain the formed spherical mesoporous composite adsorbent.

[0093] Examples 1-3:

[0094] Example 1:

[0095] This embodiment provides a green low-temperature refining process for sunflower seed oil using supercritical CO2, including the following steps:

[0096] Crude sunflower seed oil was continuously pumped into a tubular reactor and heated to 45°C via a heat exchange system. A phosphoric acid aqueous solution (85% concentration) at 0.1% of the crude oil's weight was injected along the pipeline, and the fluid remained in the tube for 15 minutes. Then, 1% of the crude oil's weight in pure water was injected into the pipeline, and the mixture was introduced into a stirred tank for hydration at 40 rpm for 20 minutes. The reaction solution was continuously centrifuged using a disc centrifuge to separate the hydrated oil residue; the liquid phase was the degummed oil.

[0097] An entrainer was prepared, consisting of 88% isopropanol, 2% citric acid, and 10% glyceryl monostearate by mass percentage. The degummed oil was pumped into the upper part of a continuous countercurrent extraction column, while supercritical carbon dioxide was pumped in from the bottom. The operating pressure of the extraction column was controlled at 15.0 MPa, the temperature at 35°C, and the gas-liquid mass ratio maintained at 5:1. The entrainer and carbon dioxide were introduced into the column together, and a variable frequency pump was used for periodic pulse injection, with a single pulse cycle set to 3 minutes. During the first 30-35% of the cycle, the entrainer was injected at a ratio of 4.0% of the total fluid mass; during the remaining time of the cycle, the entrainer injection ratio was reduced to 1.0%. The light phase, rich in free acid, escaped from the top of the extraction column, while the homogeneous fluid containing neutral oils and dissolved carbon dioxide flowed out from the bottom. The fluid was kept at a system pressure of 15.0 MPa and guided to continuously penetrate a high-pressure fixed bed filled with the spherical mesoporous composite adsorbent prepared in Example 1 from bottom to top. The residence time of the fluid in the empty tower in the fixed bed was 20 minutes.

[0098] After penetrating the fixed bed, the homogeneous fluid enters the separation system. The pressure in the primary separator is controlled at 8 MPa and the temperature at 40°C; the pressure in the secondary separator is controlled at 4 MPa and the temperature at 30°C. The vaporized carbon dioxide is recovered and recycled via a condenser, and the deacidified and decolorized refined oil is collected from the bottom of the secondary separator.

[0099] The deacidified and decolorized oil is continuously pumped into a continuous deodorization tower, and a vacuum pump unit is used to maintain the absolute pressure inside the deodorization tower at 150 Pa. The temperature of the heat transfer oil in the heating section of the deodorization tower is controlled at 175℃ for the oil system. The stripping section of the deodorization tower is filled with corrugated structured packing with a specific surface area of ​​250 square meters per cubic meter. Direct steam is uniformly introduced from the bottom of the tower at a rate of 0.5% of the oil weight, and the total residence time of the oil in the tower is 60 minutes. After deodorization, the oil is rapidly cooled to below 40℃ through a heat exchanger, and then the vacuum is released to obtain the finished refined sunflower seed oil.

[0100] The deodorized distillate obtained from the top condenser was collected and pre-degassed for 10 minutes under a vacuum of 1 kPa and a temperature of 60°C. The material then entered a first-stage short-path molecular distillation (evaporation surface temperature 120°C, system vacuum 5 Pa, and film-forming scraper rotation speed 200 rpm) to separate the light component, free fatty acids. The remaining heavy components entered a second-stage short-path molecular distillation (evaporation surface temperature 180°C, system vacuum 0.1 Pa, and film-forming scraper rotation speed 250 rpm), and the light phase on the second-stage condenser surface was collected to obtain a product enriched with vitamin E and phytosterols.

[0101] Once the fixed-bed adsorbent is saturated, disconnect the oil and fat material pipeline. Introduce pure supercritical carbon dioxide fluid at 50°C and 20MPa into the fixed bed and allow it to statically soak for 15 minutes. Turn on the fixed-bed jacket heat exchange system and introduce waste heat steam at 110°C. Adjust the pressure relief valve to gradually reduce the fluid pressure inside the bed from the initial pressure to 8MPa within 1 minute and maintain this pressure for 1 minute; then, continue to reduce the pressure to 1.0MPa over the next 2 minutes. Repeat the above cycle of repressurizing to 20MPa and depressurizing in two stages twice. After completely depressurizing, directly introduce 110°C waste heat steam into the fixed bed and purge at atmospheric pressure for 30 minutes to complete the in-situ regeneration of the adsorbent.

[0102] Example 2:

[0103] This embodiment provides a green low-temperature refining process for sunflower seed oil using supercritical CO2, including the following steps:

[0104] Crude sunflower seed oil was continuously pumped into a tubular reactor and heated to 50°C via a heat exchange system. A phosphoric acid aqueous solution (85% concentration) at 0.2% of the crude oil's weight was injected along the pipeline, and the fluid remained in the tube for 20 minutes. Then, 2% of the crude oil's weight in pure water was injected into the pipeline, and the mixture was introduced into a stirred tank for hydration at 50 rpm for 30 minutes. The reaction solution was continuously centrifuged using a disc centrifuge to separate the hydrated oil residue; the liquid phase was the degummed oil.

[0105] An entrainer was prepared, consisting of 91.5% anhydrous ethanol, 2.5% citric acid, and 6.0% polysorbate-80 by mass. The degummed oil was pumped into the upper part of a continuous countercurrent extraction column, while supercritical carbon dioxide was pumped in from the bottom. The operating pressure of the extraction column was controlled at 21.5 MPa, the temperature at 45°C, and the gas-liquid mass ratio maintained at 10:1. The entrainer and carbon dioxide were introduced into the column together, and a variable frequency pump was used for periodic pulse injection, with a single pulse cycle set to 4 minutes. During the first 30-35% of the cycle, the entrainer was injected at a ratio of 4.0% of the total fluid mass; during the remaining time of the cycle, the entrainer injection ratio was reduced to 1.0%. The light phase, rich in free acid, escaped from the top of the extraction column, while the homogeneous fluid containing neutral oils and dissolved carbon dioxide flowed out from the bottom. The fluid was kept at a system pressure of 21.5 MPa and guided to continuously penetrate the high-pressure fixed bed containing the spherical mesoporous composite adsorbent prepared in Example 2 from bottom to top. The residence time of the fluid in the empty tower in the fixed bed was 30 minutes.

[0106] After penetrating the fixed bed, the homogeneous fluid enters the separation system. The pressure in the primary separator is controlled at 10 MPa and the temperature at 45°C; the pressure in the secondary separator is controlled at 5 MPa and the temperature at 35°C. The vaporized carbon dioxide is recovered and recycled via a condenser, and the deacidified and decolorized refined oil is collected from the bottom of the secondary separator.

[0107] The deacidified and decolorized oil is continuously pumped into a continuous deodorization tower, and a vacuum pump unit is used to maintain the absolute pressure inside the deodorization tower at 250 Pa. The temperature of the heat transfer oil in the heating section of the deodorization tower is controlled at 185℃. The stripping section of the deodorization tower is filled with corrugated structured packing with a specific surface area of ​​300 square meters per cubic meter. Direct steam is uniformly introduced from the bottom of the tower at a rate of 1.0% of the oil weight, and the total residence time of the oil in the tower is 80 minutes. After deodorization, the oil is rapidly cooled to below 40℃ through a heat exchanger, and then the vacuum is released to obtain the finished refined sunflower seed oil.

[0108] The deodorized distillate obtained from the top condenser was collected and pre-degassed for 15 minutes under a vacuum of 1.5 kPa and a temperature of 70 °C. The material was then subjected to a first-stage short-path molecular distillation (evaporation surface temperature 130 °C, system vacuum 10 Pa, and film-forming scraper rotation speed 250 rpm) to separate the light component, free fatty acids. The remaining heavy component was subjected to a second-stage short-path molecular distillation (evaporation surface temperature 195 °C, system vacuum 0.5 Pa, and film-forming scraper rotation speed 300 rpm), and the light phase on the second-stage condenser was collected to obtain a product enriched with vitamin E and phytosterols.

[0109] Once the fixed-bed adsorbent is saturated, disconnect the oil and fat material pipeline. Introduce pure supercritical carbon dioxide fluid at 55°C and 22.5 MPa into the fixed bed and allow it to statically soak for 18 minutes. Turn on the fixed-bed jacket heat exchange system and introduce waste heat steam at 120°C. Adjust the pressure relief valve to gradually reduce the fluid pressure inside the bed from the initial pressure to 9 MPa within 1.5 minutes and maintain this pressure for 1 minute; then, continue to reduce the pressure to 1.5 MPa within the following 2.5 minutes. Repeat the above cycle of repressurizing to 22.5 MPa and the two-step pressure relief three times. After completely depressurizing, directly introduce 120°C waste heat steam into the fixed bed and purge at atmospheric pressure for 45 minutes to complete the in-situ regeneration of the adsorbent.

[0110] Example 3:

[0111] This embodiment provides a green low-temperature refining process for sunflower seed oil using supercritical CO2, including the following steps:

[0112] Crude sunflower seed oil was continuously pumped into a tubular reactor and heated to 55°C via a heat exchange system. A phosphoric acid aqueous solution (85% concentration) at 0.3% of the crude oil's weight was injected along the pipeline, and the fluid remained in the tube for 30 minutes. Then, 3% of the crude oil's weight in pure water was injected into the pipeline, and the mixture was introduced into a stirred tank for hydration at 60 rpm for 40 minutes. The reaction solution was continuously centrifuged using a disc centrifuge to separate the hydrated oil residue; the liquid phase was the degummed oil.

[0113] The entrainer was prepared with a composition of 95% anhydrous ethanol, 2% ascorbic acid, and 3% diglyceride monostearate by mass percentage. The degummed oil was pumped into the upper part of a continuous countercurrent extraction column, while supercritical carbon dioxide was pumped in from the bottom. The operating pressure of the extraction column was controlled at 28.0 MPa, the temperature at 55°C, and the gas-liquid mass ratio maintained at 15:1. The entrainer and carbon dioxide were introduced into the column together, and a variable frequency pump was used for periodic pulse injection, with a single pulse cycle set to 5 minutes. During the first 30-35% of the cycle, the entrainer was injected at a ratio of 4.0% of the total fluid mass; the injection was stopped for the remainder of the cycle. The light phase, rich in free acid, escaped from the top of the extraction column, while the homogeneous fluid containing neutral oils and dissolved carbon dioxide flowed out from the bottom. The fluid was kept at a system pressure of 28.0 MPa and guided to continuously penetrate the high-pressure fixed bed containing the spherical mesoporous composite adsorbent prepared in Example 3 from bottom to top. The empty tower residence time of the fluid in the fixed bed was 40 minutes.

[0114] After penetrating the fixed bed, the homogeneous fluid enters the separation system. The pressure in the primary separator is controlled at 12 MPa and the temperature at 50°C; the pressure in the secondary separator is controlled at 6 MPa and the temperature at 40°C. The vaporized carbon dioxide is recovered and recycled via a condenser, and the deacidified and decolorized refined oil is collected from the bottom of the secondary separator.

[0115] The deacidified and decolorized oil is continuously pumped into a continuous deodorization tower, and a vacuum pump unit is used to maintain the absolute pressure inside the deodorization tower at 350 Pa. The temperature of the heat transfer oil in the heating section of the deodorization tower is controlled at 195℃. The stripping section of the deodorization tower is filled with corrugated structured packing with a specific surface area of ​​350 square meters per cubic meter. Direct steam is uniformly introduced from the bottom of the tower at a rate of 1.5% of the oil weight, and the total residence time of the oil in the tower is 100 minutes. After deodorization, the oil is rapidly cooled to below 40℃ through a heat exchanger, and then the vacuum is released to obtain the finished refined sunflower seed oil.

[0116] The deodorized distillate obtained from the top condenser was collected and pre-degassed for 20 minutes under a vacuum of 2 kPa and a temperature of 80°C. The material then entered a first-stage short-path molecular distillation (evaporation surface temperature 140°C, system vacuum 20 Pa, and film-forming scraper rotation speed 350 rpm) to separate the light component, free fatty acids. The remaining heavy components entered a second-stage short-path molecular distillation (evaporation surface temperature 210°C, system vacuum 1.0 Pa, and film-forming scraper rotation speed 400 rpm), and the light phase on the second-stage condenser surface was collected to obtain a product enriched with vitamin E and phytosterols.

[0117] Once the fixed-bed adsorbent is saturated, disconnect the oil and fat material pipeline. Introduce pure supercritical carbon dioxide fluid at 60°C and 25MPa into the fixed bed and allow it to statically soak for 20 minutes. Turn on the fixed-bed jacket heat exchange system and introduce waste heat steam at 130°C. Adjust the pressure relief valve to gradually reduce the fluid pressure inside the bed from the initial pressure to 10MPa within 2 minutes and maintain this pressure for 1 minute; then, continue to reduce the pressure to 2.0MPa over the next 3 minutes. Repeat the above cycle of repressurizing to 25MPa and the two-step pressure relief three times. After completely depressurizing, directly introduce 130°C waste heat steam into the fixed bed and purge at atmospheric pressure for 60 minutes to complete the in-situ regeneration of the adsorbent.

[0118] Comparative Examples 1-5:

[0119] Comparative Example 1:

[0120] Compared with Example 2, the difference is that the variable frequency periodic pulse injection of the entrainer is cancelled. Instead, the entrainer of equal total volume (at an average ratio of 2.0% of the total fluid mass) is mixed with supercritical carbon dioxide fluid and then continuously injected at a constant concentration. All other aspects are the same.

[0121] Comparative Example 2:

[0122] Compared with Example 2, the difference is that the oil after supercritical deacidification is directly collected by depressurization and then a conventional mechanical stirring decolorization process is adopted, that is, 2% activated clay by weight of the oil is added to the deacidified oil, and mechanical stirring at 300 rpm for 30 minutes under vacuum of 1 kPa and temperature of 95°C is used for decolorization and filtration. Finally, a deodorization step is performed, and the rest is the same.

[0123] Comparative Example 3:

[0124] Compared with Example 2, the difference is that the zero-shear high-pressure fixed bed filled with spherical mesoporous composite adsorbent was replaced with a high-pressure dynamic stirred reactor containing the same mass of adsorbent, maintaining a high pressure of 21.5 MPa, but reacting for 30 minutes under high-speed mechanical shear stirring at 300 rpm, while the rest were the same.

[0125] Comparative Example 4:

[0126] Compared with Example 2, the difference is that the transient step-by-step pressure relief operation is cancelled. Instead, after the material is cut off and statically soaked, the pressure relief valve is slowly and evenly opened to linearly and uniformly reduce the internal pressure of the bed from 22.5 MPa to atmospheric pressure within 30 minutes (in order to destroy the micro-explosive physical reaction thrust generated by the instantaneous vaporization and volume expansion of supercritical carbon dioxide). All other aspects are the same.

[0127] Comparative Example 5:

[0128] Compared with Example 2, the difference is that it deviates from the full-chain integrated process framework of the present invention and adopts the traditional single-process linear cumulative refining method, that is, the crude oil is sequentially subjected to: phosphoric acid degumming, sodium hydroxide alkali refining deacidification and water washing centrifugation separation (removing free acid), vacuum drying, high temperature mechanical stirring decolorization with activated clay (95°C) and conventional high temperature bubbling deodorization (temperature 245°C, absolute pressure 250Pa), and the rest are the same.

[0129] Test Examples 1-5:

[0130] Test Example 1:

[0131] This test case aims to verify the feasibility and synergistic effect of the micro-gradient pulse injection mode compared with the constant steady-state continuous injection mode in inducing interfacial mass transfer disturbances and improving the kinetic efficiency of supercritical deacidification.

[0132] Take the continuous countercurrent extraction tower deacidification system set in Example 2 and Comparative Example 1, start the heat exchange and pressurization equipment, and wait for the internal operating pressure of the system to stabilize at 21.5 MPa and the temperature to stabilize at 45°C.

[0133] Sunflower seed degummed oil and supercritical carbon dioxide fluid are pumped into the extraction tower at a set gas-liquid total mass ratio of 10:1 to establish a countercurrent contact field.

[0134] Turn on the entrainer injection pump. In Example 2, inject according to the frequency conversion pulse program (4-minute cycle, 4.0% in the first 1 / 3 high ratio period and 1.0% in the last 2 / 3 low ratio period). In Comparative Example 1, inject continuously at a constant flow rate (average ratio 2.0%).

[0135] Once the fluid inside the tower reaches gas-liquid mass transfer equilibrium and produces a stable output material, this point is set as the zero point of the reaction and the timing begins.

[0136] A high-pressure sampling bypass is installed on the homogeneous fluid outlet pipeline at the bottom of the extraction tower, and a fluid sample is collected every 5 minutes under isobaric conditions through a back pressure valve.

[0137] The sampled fluid was subjected to a vacuum separation system to remove carbon dioxide gas, and the liquid phase oil was collected. The absolute acid value of the oil sample at each time point was determined using a conventional potassium hydroxide titration method, and the free fatty acid removal rate was calculated.

[0138] Table 1. Comparison of residual acid value and removal rate between pulse injection and steady-state injection at different extraction times.

[0139] Time (min) Example 2: Residual acid value (mgKOH / g) Example 2 Removal rate (%) Comparative Example 1: Residual acid value (mgKOH / g) Removal rate (%) of Comparative Example 1 0 1.83 0.0 1.78 0.0 5 1.15 37.1 1.41 20.7 10 0.72 60.6 1.16 34.8 15 0.33 81.9 0.82 53.9 20 0.12 93.4 0.55 69.1 25 0.09 95.0 0.36 79.7 30 0.06 96.7 0.28 84.2

[0140] Summary: Based on Figure 1 , Figure 2 Based on the data in Table 1, Example 2 and Comparative Example 1, under the same operating pressure, temperature, and average amount of macroscopic entrainer, exhibited different mass transfer rates. After 30 minutes of extraction, the residual acid value in Example 2 decreased to 0.06 mg KOH / g, achieving a removal rate of 96.7%; while Comparative Example 1, using steady-state continuous injection, still had a residual acid value of 0.28 mg KOH / g, exhibiting mass transfer decay characteristics in the later stages of the reaction, thus verifying the physical effects of pulsed periodic injection of fluid in supercritical systems.

[0141] In the constant injection mode of Comparative Example 1, the polar entrainer has a uniform concentration in the supercritical bulk, and the transfer of free fatty acids across the phase interface mainly relies on molecular diffusion. As the concentration of free fatty acids in the oil phase decreases, the concentration gradient decreases, the solute boundary layer at the gas-liquid interface thickens, and the mass transfer resistance increases, leading to a decrease in deacidification efficiency in the middle and late stages.

[0142] Example 2 constructed a transient concentration micro-gradient by changing the input frequency. Periodic high-low ratio inputs created entrainer concentration waves within the fluid along the flow direction. This concentration difference induced a surface tension gradient distribution at the two-phase interface, leading to spontaneous fluid flow and inducing Marangoni convection. The interfacial micro-perturbation applied by non-mechanical devices broke the static boundary layer, enhancing interphase mass transfer. Simultaneously, the local transient concentration changes adjusted the thermodynamic partition coefficient of the free fatty acids, maintaining a high interfacial transfer flux even in the later stages of the reaction when the overall concentration difference was small.

[0143] Test Example 2:

[0144] This test case aims to evaluate the mechanistic effects of a high-pressure zero-shear laminar microenvironment constructed with supercritical fluid, compared to a high-pressure mechanically stirred turbulent environment, in blocking mechanically shear-induced lipid oxidation and protecting antioxidants.

[0145] The homogeneous oil fluid containing supercritical carbon dioxide discharged from the deacidification process of the continuous countercurrent extraction tower was used as the test base material. The initial peroxide value, anisidine value and total vitamin E of this intermediate material were determined as the baseline control value.

[0146] The base material was divided into two streams. The first stream was maintained at a system pressure of 21.5 MPa and guided upwards through a high-pressure fixed bed filled with composite adsorbent. The residence time of the fluid in the empty tower within the bed was controlled to be 30 minutes, without applying any external mechanical stirring force. This is the test group for Example 2.

[0147] The second batch of material was introduced into a high-pressure dynamically stirred reactor containing an equal amount of the same batch of composite adsorbent. The system was sealed and maintained at a pressure of 21.5 MPa and a temperature of 45°C. The mechanical stirring system was activated and set to a speed of 300 rpm, allowing the material to react in a strong turbulent shear field for 30 minutes. After the reaction, the fluid was filtered through an online high-pressure microporous membrane to separate the adsorbent powder. This is the comparative example 3 test group.

[0148] Oil samples separated under reduced pressure after the above two reactions were collected. The peroxide value was determined by iodometric titration, the anisidine value was determined by spectrophotometry, and the tocopherol homologues extracted from the oil were quantitatively determined by high performance liquid chromatography. The total vitamin E content and relative retention rate of each sample were calculated.

[0149] Table 2. Data on oil oxidation and nutrient retention under fixed-bed laminar flow and stirred-tank turbulent shear conditions

[0150] Sample source Peroxide value (mmol / kg) Anisamine value Total vitamin E (mg / kg) Relative retention rate of vitamin E (%) Basic materials after deacidification 2.14 1.18 641.3 100.0 Example 2 Decolorizing Oil 1.87 1.05 627.5 97.8 Comparative Example 3: Decolorizing Oil 5.32 4.29 496.2 77.4

[0151] Summary: Based on Figure 3 , Figure 4 Based on the data in Table 2, under the same thermodynamic conditions, contact time, and amount of adsorbent material, Example 2 and Comparative Example 3 showed numerical differences in the degree of oxidative deterioration and the loss rate of antioxidant substances in the oils. The oil from Example 2, after fixed-bed decolorization, had lower peroxide and anisidine values ​​than the deacidified base material, demonstrating the retention effect of the adsorbent material on some polar oxidative primary and secondary products. The oil from Comparative Example 3, after high-pressure mechanical stirring decolorization, showed an increase in peroxide value to 5.32 mmol / kg and an anisidine value to 4.29, accompanied by a decrease in vitamin E content.

[0152] The data distribution corroborates the influence of the macroscopic fluid dynamics environment on the microscopic chemical reaction process of the system. Under the stirring conditions of Comparative Example 3, the dissolution of supercritical carbon dioxide reduced the viscosity of the system, but the high-frequency shear force of the mechanical impeller triggered local fluid shearing and microscopic cavitation in the gas-liquid-solid multiphase mixture. Mechanical work was converted into heat energy within the liquid phase, forming local hot spots, and physical fracturing forces caused the carbon-hydrogen bonds of some unsaturated fatty acids to break, inducing the generation of lipid free radicals.

[0153] Free radical chain reactions accelerate the oxidation process, consuming vitamin E with phenolic hydroxyl electron donor structures within the system. Example 2 utilizes the low viscosity of the high-pressure dissolving phase, allowing the oil to flow smoothly through the solid phase channels at a low Reynolds number laminar flow rate. This decolorization process eliminates mechanical kinetic energy input, removing frictional heat and shear-induced oxidation effects caused by flow velocity gradients. Target pigments and polar impurities are captured by adsorption sites through microporous diffusion driven by the concentration gradient, maintaining the system's chemical stability and preventing the loss of natural antioxidant components.

[0154] Test Example 3:

[0155] This test case aims to verify the feasibility of the fluid phase change expansion effect induced by transient step pressure relief in removing deep adsorbates from porous composite materials and extending the online regeneration cycle life compared to linear uniform pressure relief.

[0156] A fixed-bed adsorption device that is in continuous operation and has reached the endpoint of pigment adsorption penetration is used to expel free oily materials by pushing them out with low-pressure carbon dioxide fluid.

[0157] Seal the inlet and outlet liquid lines of the adsorption bed and introduce supercritical carbon dioxide fluid at a temperature of 55℃ and a pressure of 22.5MPa into the system. Maintain static soaking for 18 minutes to allow the supercritical fluid to penetrate into the internal pores of the mesoporous adsorption material. Simultaneously, open the fixed bed jacket and introduce 120℃ hot steam to maintain the bed temperature.

[0158] Example 2 test group performed transient step-down pressure relief operation: the pressure relief valve was adjusted to reduce the fluid pressure from 22.5 MPa to 9 MPa within 1.5 minutes, and held for 1 minute; then the pressure was reduced to 1.5 MPa within 2.5 minutes. After repressurization to 22.5 MPa, the above step-down operation was repeated 3 times.

[0159] Comparative Example 4 test group performed linear uniform pressure relief operation: the airflow discharge rate was controlled by the back pressure valve, so that the system pressure dropped from 22.5MPa to 1.5MPa at a uniform slope, and the total pressure relief time was set to 30 minutes.

[0160] The liquid-phase desorbate containing pigments and polar substances discharged with the gas flow is collected through a terminal condenser. After drying and solvent removal, the total mass of the desorbate is measured by gravimetric method, and the mass desorption rate relative to the theoretical saturated adsorption is calculated.

[0161] After purging the bed with atmospheric pressure hot steam, the initial oil to be decolorized is reintroduced for a second round of adsorption breakthrough testing. The real-time adsorption capacity is calculated based on the amount of oil processed at the critical point where the effluent color meets the standard. This process is repeated for five consecutive adsorption-regeneration cycles.

[0162] Table 3. Desorption rate and capacity retention rate under stepped transient and linear uniform pressure relief modes after multiple cycles

[0163] Loop count Example 2 Desorption rate (%) Example 2: Capacity retention rate (%) Comparative Example 4 Desorption rate (%) Comparative Example 4: Capacity retention rate (%) 1 89.3 96.4 42.1 58.7 2 86.1 91.2 35.6 41.2 3 84.7 88.5 31.8 32.5 4 85.2 84.1 28.4 24.9 5 82.8 81.6 21.9 17.3

[0164] Summary: Based on Figure 5 , Figure 6 Based on the data in Table 3, the regeneration effectiveness and adsorption lifetime of the porous materials in Example 2 and Comparative Example 4 differed after multiple cycles. In Example 2, after the first step-depressurization regeneration, the desorption rate reached 89.3%, and after 5 cycles, its adsorption capacity retention rate remained at 81.6%. In Comparative Example 4, which used uniform depressurization, the single-cycle desorption rate was only 42.1%, and the capacity retention rate decreased to 17.3% by the fifth cycle, indicating that the adsorption bed was essentially ineffective.

[0165] Data validated the mechanism of fluid phase transition kinetics in the pore cleaning process. Under the uniform pressure relief condition of Comparative Example 4, the supercritical fluid penetrating into the mesopores underwent a slow phase transition and diffusion mass transfer as the system pressure decreased. This steady-state process lacked the hydrodynamic scouring kinetic energy to overcome the electrostatic dipole forces and hydrogen bonding between pigment molecules and amino and silanol groups. Most of the macromolecular adsorbates remained deep within the pores, resulting in irreversible loss of specific surface area.

[0166] Example 2 employs a step-down depressurization process over an extremely short time, causing the carbon dioxide fluid deep within the pores to vaporize as it crosses the critical point. This phase change triggers a rapid expansion of the fluid's specific volume within milliseconds. Constrained by the pore space, this volume expansion generates a micro-explosive physical recoil force within the mesopores, pushing the adsorbate and active sites apart. This mechanical work breaks the bonds between the adsorbate and the active sites, displacing large molecular impurities from the micropores into the main fluid channel. This thermodynamic desorption mechanism overcomes the limitation of organic-inorganic hybrid adsorbents, which cannot be regenerated by high-temperature calcination due to their thermal limits.

[0167] Test Example 4:

[0168] This test case evaluates the differences between this integrated refining process and the traditional linear alkali refining-clay refining process in key engineering indicators such as conventional physicochemical removal effect and absolute loss rate of neutral oil.

[0169] The initial sunflower seed crude oil and the refined finished oil samples obtained by the processes of Example 1, Example 2, Example 3 and Comparative Example 5 were collected and stored at room temperature in the dark for later use.

[0170] Retrieve quality monitoring data from each refining test group at the feeding and output stages. Perform a full-process material balance based on the initial crude oil quality and the quality of intermediate by-products and deodorized oil collected at each stage. Deduct the theoretical mass of impurities such as free fatty acids, phospholipids, and moisture in the crude oil, calculate the absolute loss of triglycerides due to the process, and determine the neutral oil loss rate.

[0171] Weigh out each component oil sample and dissolve it in a mixed solvent of diethyl ether and isopropanol. Add phenolphthalein indicator and titrate with a 0.1 mol / L potassium hydroxide standard titration solution. Record the volume consumed and calculate the acid value.

[0172] Take a clear, transparent oil sample and pour it into a 133.4 mm standard colorimetric cell, then place it in a Lovibond colorimeter. Adjust the standard filter until the field color matches the oil sample color, and record the Lovibond yellow (Y) and red (R) values ​​for each sample.

[0173] Table 4. Determination of Physicochemical Properties and Neutral Oil Loss Rate for Different Refining Processes

[0174] Sample batch Acid value (mgKOH / g) Color (Lo Wei Peng Y) Color (Lowipon R) Neutral oil loss rate (%) initial crude oil 2.18 38.0 4.3 - Example 1 Finished Oil 0.13 11.0 1.1 1.54 Example 2 Finished Oil 0.07 9.0 0.9 1.36 Example 3 Finished Oil 0.05 8.0 0.6 1.61 Comparative Example 5: Refined Oil 0.11 10.0 1.0 5.82

[0175] Summary: Based on Figure 7 , Figure 8 According to the data in Table 4, after undergoing the integrated refining process, the acid value of the finished oil in Examples 1, 2, and 3 decreased to 0.13, 0.07, and 0.05 mgKOH / g, respectively. The color index met the conventional standards, and the treatment effect was comparable to that of Comparative Example 5, which uses the traditional alkali refining-clay refining process. While the physicochemical removal effects were similar, there were significant differences in the neutral oil loss rate.

[0176] The neutral oil loss rate of Comparative Example 5 reached 5.82%, while the neutral oil loss rates of Examples 1, 2, and 3 ranged from 1.36% to 1.61%. The decoupling of physicochemical properties and loss rates validated the underlying logic of the phase separation system. Comparative Example 5 employed chemical alkali refining for deacidification, where sodium hydroxide neutralized free fatty acids to generate sodium fatty acids. The byproducts exhibited strong surface activity, forming a complex emulsion phase that inevitably carried triglycerides into the soapstock during centrifugation. The porous structure of the large amount of powdered activated clay relied upon for the decolorization standard also physically adsorbed oils, leading to additional oil loss.

[0177] This process transforms physicochemical separation into thermodynamic phase separation. Supercritical fluid extraction for deacidification utilizes differences in molecular polarity and molecular weight to achieve selective mass transfer. Free fatty acids have higher solubility in supercritical fluids than triglycerides, and gas-liquid mass transfer based on the solubility gradient avoids chemical saponification reactions and soap residue entrainment effects. The decolorization stage relies on specific active sites immobilized in the framework and mesoporous exclusion effects for directional adsorption, avoiding disordered adsorption and retention of the liquid phase by the powdered adsorbent. The entire process eliminates multiphase emulsion entrainment and high-temperature degradation, achieving highly efficient retention of triglycerides while meeting the target removal rate.

[0178] Test Example 5:

[0179] This test case aims to determine the retention capacity of the entire system for micronutrient byproducts and to quantitatively compare it with a process system that includes traditional high-temperature clay treatment and high-temperature deodorization.

[0180] Extract the initial sunflower seed crude oil, the refined oil obtained in Examples 1 to 3, the refined oil obtained in Comparative Example 2, and the refined oil obtained in Comparative Example 5, and weigh 2.00g of each and evenly pack them into different saponification bottles.

[0181] Add 30 mL of 1M potassium hydroxide-ethanol solution and 0.2 g of ascorbic acid to each saponification flask, and connect the reflux condenser. Heat under reflux in a constant temperature water bath at 80°C for 45 minutes in the dark to induce saponification of the fats.

[0182] After cooling the reaction solution to room temperature, 50 mL of deionized water was added to stop the reaction. Then, 50 mL of n-hexane was added as extraction solvent for extraction. After standing and separating the layers, the organic phase was collected. The extraction was repeated three times, and the extracts were combined. The organic phase was washed with deionized water until neutral to remove the alkaline solution.

[0183] The organic phase was concentrated to near dryness using a rotary evaporator under a vacuum of 0.08 MPa and a temperature of 40 °C. The residue was dissolved in chromatographically pure methanol and diluted to 10 mL. The solution was then filtered through a 0.22 μm microporous membrane and used as the test solution.

[0184] The analyte was analyzed using a high-performance liquid chromatograph equipped with a UV detector. The chromatographic column was a C18 reversed-phase column; the mobile phase was a methanol-water gradient system; the column temperature was 30℃; and the detection wavelengths were set to 295 nm (tocopherol) and 205 nm (phytosterol).

[0185] The total mass of each component was determined by quantifying it using the standard working curve based on the external standard method. The retention rate was calculated by comparing the total amount measured in the finished oil with the total amount measured in the initial crude oil.

[0186] Table 5. Determination of Vitamin E and Phytosterol Retention Rates under Different Refining Processes

[0187] Sample batch Total vitamin E (mg / kg) Vitamin E retention rate (%) Total phytosterols (mg / kg) Phytosterol retention rate (%) initial crude oil 643.5 100.0 2841.2 100.0 Example 1 Finished Oil 553.1 85.9 2486.3 87.5 Example 2 Finished Oil 587.4 91.3 2571.8 90.5 Example 3 Finished Oil 569.2 88.4 2514.6 88.5 Comparative Example 2: Refined Oil 412.3 64.1 1904.5 67.0 Comparative Example 5: Refined Oil 294.6 45.8 1361.7 47.9

[0188] Summary: Based on Figure 9 , Figure 10 As shown in Table 5, the integrated process and the traditional process differ in their ability to retain trace amounts of byproducts when processing oils. The background values ​​of vitamin E and phytosterols in crude oil were 643.5 mg / kg and 2841.2 mg / kg, respectively. After treatments in Examples 1, 2, and 3, the retention rates of both remained in the ranges of 85.9%-91.3% and 87.5%-90.5%, respectively. In Comparative Example 5, which underwent traditional alkali refining, decolorization, and high-temperature deodorization, vitamin E decreased to 294.6 mg / kg, and phytosterols decreased to 1361.7 mg / kg. In Comparative Example 2, where the decolorization step was replaced with clay treatment, the retention rate also decreased to the 60% level.

[0189] The changes in physicochemical data reflect the mechanism by which the process environment disrupts the stability of molecular structures. In traditional processes, strong alkali neutralization produces a large amount of soap bundles. Free sterols and some polar vitamins, due to their hydrophilic ends, are easily solubilized by the surface-active soap bundles and discharged with the separated aqueous phase. During the decolorization stage of bleaching clay, Lewis acid centers are distributed on the surface of traditional activated clay. At the high-temperature reaction interface, solid acids catalytically oxidize and isomerize the hydroxyl groups and double bonds on tocopherol and sterol rings, converting them into inactive oxidative degradation products. The conventional high-temperature range for deodorization (240℃-260℃) exceeds the thermodynamic cracking activation energy threshold of the aforementioned molecules, inducing polymerization, and the rapid increase in saturated vapor pressure causes nutrients to be vaporized out of the system with water vapor.

[0190] The entire process in this embodiment eliminates contact between strong acid / base reagents and the high-temperature phase interface. The weak acid solvation effect of the supercritical fluid microenvironment shields the components; zero-shear decolorization relies on mesoporous exclusion effect for mass transfer interception, without providing catalytic centers for oxidation; the dual low-temperature deodorization parameters (175℃-195℃) are below the critical value of the cold end of the phase transition volatilization of heat-sensitive substances. The overall downward shift of the system's physical and thermodynamic environment reduces the free energy of side reactions and controls the transfer of nutrients from the main phase to the waste phase.

Claims

1. A green low-temperature refining process for sunflower seed oil using supercritical CO2, characterized in that, Includes the following steps: Sunflower seed crude oil was subjected to continuous tubular gentle degumming, and the hydrated oil residue was separated by centrifugation to obtain degummed oil. The degummed oil is fed into a continuous countercurrent extraction tower, supercritical carbon dioxide fluid is introduced, and an entrainer is injected in a periodic frequency-variable pulse mode to perform deacidification extraction and obtain a homogeneous fluid containing neutral oil and dissolved carbon dioxide. The homogeneous fluid containing neutral oil and dissolved carbon dioxide is directly introduced into a high-pressure fixed bed filled with spherical mesoporous composite adsorbent under the same temperature and pressure conditions, and continuously penetrates the bed layer for decolorization to obtain the decolorized fluid. The decolorized fluid is subjected to step decompression analysis to separate gaseous carbon dioxide and liquid refined base oil. The gaseous carbon dioxide is recovered and recycled via a condenser. The liquid-phase refined base oil is continuously deodorized, the deodorized distillate obtained by condensation at the top of the column is collected, and the finished refined oil is collected at the bottom of the column; The deodorized distillate was subjected to short-path molecular distillation to separate free fatty acids and recover the product enriched with vitamin E and phytosterols. For spherical mesoporous composite adsorbents that have reached adsorption saturation, after static immersion in supercritical carbon dioxide fluid, step-wise depressurization is implemented to carry out in-situ desorption and regeneration.

2. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, The specific operation for continuous tubular gentle degumming of crude sunflower seed oil is as follows: Crude sunflower seed oil is heated to 45-55℃ through a heat exchange system. An 85% phosphoric acid aqueous solution is injected along the pipeline, with the amount of phosphoric acid aqueous solution added controlled at 0.1-0.3% of the crude oil mass. The fluid remains in the pipeline for 15-30 minutes to react. Then, 1-3% of the crude oil mass of pure water is injected and the mixture is introduced into a stirred tank for hydration reaction at 40-60 rpm for 20-40 minutes. Finally, the hydrated oil residue is separated by continuous centrifugation using a disc centrifuge.

3. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, During deacidification extraction, the system pressure of the continuous countercurrent extraction tower is controlled at 15.0-28.0 MPa, the temperature is controlled at 35-55℃, and the gas-liquid mass ratio is maintained at (5-15):

1. The variable frequency pulse injection mode of the entrainer is as follows: a complete injection cycle is set to 3-5 minutes. During the first 30-35% of the cycle, the entrainer injection flow rate accounts for 4.0% of the total fluid mass, and during the remaining time period of the cycle, the entrainer injection flow rate accounts for 0-1.0% of the total fluid mass.

4. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 3, characterized in that, The entrainer is a mixture of components comprising the following weight percentages: Main solvent 88-95%; Organic acids 2-2.5%; Emulsifier 3-10%; The main solvent is anhydrous ethanol or isopropanol, the organic acid is citric acid or ascorbic acid, and the emulsifier is glyceryl monostearate, polysorbate-80, or diglyceryl monostearate.

5. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, During decolorization, the residence time of the homogeneous fluid containing neutral oil and dissolved carbon dioxide in the high-pressure fixed bed filled with spherical mesoporous composite adsorbent is controlled to be 20-40 minutes.

6. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 5, characterized in that, The preparation method of the spherical mesoporous composite adsorbent includes: Chitosan with a degree of deacetylation of 85-95% is dissolved in an aqueous solution of glacial acetic acid with a volume concentration of 1.0-2.0% to prepare a chitosan gel solution with a mass concentration of 2-4%. Tetraethyl orthosilicate and anhydrous ethanol were mixed at a volume ratio of 1:(1-3), and 20-30% of the volume of tetraethyl orthosilicate in deionized water was added. The pH of the system was adjusted to 2.0-3.0 by adding 0.1mol / L hydrochloric acid solution dropwise. The mixture was stirred at 300-500rpm for 1-2 hours at 40-50℃ to obtain silica sol. The chitosan solution is added dropwise to the silica sol at a rate of 5-10 mL / min. Sodium alginate of 1-2% of the dry weight of chitosan is added, and genipin aqueous solution of 1-5% of the dry weight of chitosan and a mass concentration of 0.5-1.5% is added as a crosslinking agent. The mixture is stirred at 150-250 rpm at 50-60°C for 2-3 hours to form a semi-gel. The semigel was dripped through a dropper with a diameter of 1-3 mm into a coagulation bath containing 2% anhydrous calcium chloride at 0-5°C and solidified to obtain spherical gel particles. The spherical gel particles were aged at room temperature for 12-24 hours and repeatedly washed until neutral. They were then pre-frozen at -60°C to -40°C and subsequently freeze-dried under vacuum at an absolute pressure of 10-30 Pa for 24-48 hours to obtain the spherical mesoporous composite adsorbent.

7. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, The specific steps for performing stepped decompression analysis on the decolorized fluid are as follows: The decolorized fluid enters the separation system. The pressure in the primary separation vessel is controlled at 8-12 MPa and the temperature at 40-50℃. The pressure in the secondary separation vessel is controlled at 4-6 MPa and the temperature at 30-40℃.

8. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, During continuous deodorization, the absolute pressure inside the deodorization tower is maintained at 150-350 Pa, the temperature of the heat transfer oil in the heating section is controlled at 175-195℃, the stripping section of the deodorization tower is filled with corrugated structured packing with a specific surface area of ​​250-350 square meters per cubic meter, and direct steam at a rate of 0.5-1.5% of the oil weight is introduced from the bottom of the tower. The total residence time of the oil in the tower is 60-100 minutes.

9. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, The specific operation of short-path molecular distillation treatment of the deodorized distillate is as follows: The deodorized distillate was pre-degassed for 10-20 minutes under a vacuum of 1-2 kPa and a temperature of 60-80°C. The material enters a first-stage short-path molecular distillation, with an evaporation surface temperature of 120-140℃, a system vacuum of 5-20Pa, and a film-forming scraper speed of 200-350rpm, separating light components of free fatty acids. The remaining heavy components enter a second-stage short-path molecular distillation process. The evaporation surface temperature is 180-210℃, the system vacuum is 0.1-1.0Pa, and the film-forming scraper speed is 250-400rpm. The light phase on the second-stage condenser surface is collected to obtain a product enriched with vitamin E and phytosterols.

10. The supercritical CO2 sunflower seed oil green low-temperature refining process according to claim 1, characterized in that, The specific operation for in-situ desorption and regeneration is as follows: Introduce pure supercritical carbon dioxide fluid at a temperature of 50-60℃ and a pressure of 20-25MPa, and statically immerse the high-pressure fixed bed for 15-20 minutes. Turn on the fixed bed jacket heat exchange system and introduce waste heat steam at 110-130℃; Implement the first step pressure relief, adjust the pressure relief valve to reduce the fluid pressure inside the bed to 8-10 MPa within 1-2 minutes, and maintain the pressure for 1 minute; Implement a second step-by-step depressurization, further reducing the pressure to 1.0-2.0 MPa within 2-3 minutes; Repressurize to 20-25 MPa and repeat the above two-step depressurization operation 2-3 times; Finally, waste heat steam at 110-130℃ is directly introduced into the fixed bed and purged for 30-60 minutes at atmospheric pressure.

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