Double-zero double-low deodorization and efficient byproduct recovery method for sunflower seed oil

Abstract

The invention relates to the technical field of edible oil and fat processing, and discloses a sunflower seed oil double-zero double-low deodorization and by-product efficient recovery method, which comprises the following steps: carrying out degumming pretreatment on sunflower seed crude oil, pumping the sunflower seed crude oil into an extraction tower, and carrying out supercritical extraction on the sunflower seed crude oil and high-pressure carbon dioxide fluid. The extraction phase sequentially passes through a multi-stage analysis system; a refined sunflower seed oil finished product is separated by depressurizing and cooling in a first-stage analysis kettle; converting into a subcritical state in a second-stage desorption kettle, and selectively intercepting and separating out the phytosterol by utilizing beta-CD-PU porous cross-linked microspheres filled in the second-stage desorption kettle; depressurizing and separating out vitamin E in a third-stage desorption kettle; and finally entering a flash tank to gasify the carbon dioxide, and separating free fatty acid and small molecule leftovers with peculiar smell. According to the invention, nutritional ingredient loss and trans-fatty acid generation caused by high-temperature deodorization are avoided, and grease deodorization and step-by-step accurate separation and independent recovery of multiple byproducts are realized.

Description

Technical Field

[0001] This invention relates to the field of edible oil processing technology, specifically to a method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products. Background Technology

[0002] Sunflower seed oil contains nutrients such as vitamin E and phytosterols, but during processing and refining, free fatty acids and volatile odor substances need to be removed to ensure oil quality. Traditional deodorization processes mainly employ vacuum high-temperature steam deodorization. This method is typically carried out at high temperatures, and prolonged exposure to high temperatures can easily trigger isomerization reactions within the oil system, leading to the formation of harmful substances such as trans fatty acids or polycyclic aromatic hydrocarbons. Simultaneously, the high-temperature environment can destroy heat-sensitive micronutrients, causing these valuable components to decompose in large quantities or volatilize into the deodorized distillate along with the steam, thus reducing the nutritional value of the finished oil.

[0003] To avoid the deterioration of oil quality caused by high temperatures, non-high-temperature deodorization technologies, such as supercritical carbon dioxide fluid extraction, are gaining increasing attention. However, when processing sunflower seed oil systems containing multiple minor components, existing supercritical fluid extraction and analysis processes struggle to achieve precise, stepwise separation of each component. The solubility variations of high-value byproducts such as phytosterols and vitamin E in supercritical fluids are quite similar.

[0004] In conventional fluid depressurization and cooling desorption processes, due to the lack of selective retention mechanisms for specific molecules, substances with similar molecular weights and polarities often co-precipitate, resulting in a mixture of various byproducts separated from the desorption vessel. Extracting high-purity phytosterols or vitamin E from such mixed distillates requires additional complex secondary separation or chemical purification processes. This not only increases the operational steps and equipment costs for industrial production but also reduces the overall recovery efficiency of byproducts. Therefore, how to achieve low-temperature deodorization of oils while simultaneously and independently separating and extracting high-value byproducts mixed in the fluid within a continuous process is a practical problem that needs to be solved in this field. Summary of the Invention

[0005] The technical problem solved by this invention is that traditional high-temperature steam deodorization processes for sunflower seed oil often result in the loss of heat-sensitive nutrients and even the generation of harmful substances such as trans fatty acids. In addition, existing technologies also struggle to achieve precise, stepwise separation and independent recovery of phytosterols, vitamin E, and free fatty acids in the byproduct system generated during deodorization.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products, employing the following technical solution:

[0008] A method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts, includes the following steps:

[0009] The degummed pretreated crude oil is continuously pumped into the middle of the extraction tower, and high-pressure pure carbon dioxide fluid is pumped in from the bottom of the extraction tower for supercritical extraction. The supercritical extract phase discharged from the top of the extraction tower is collected.

[0010] The supercritical extract phase discharged from the top of the extraction tower is introduced into the first-stage desorption vessel for depressurization and cooling, and the refined sunflower seed oil product separated from the bottom of the first-stage desorption vessel is collected.

[0011] The carbon dioxide fluid containing byproducts discharged from the top of the first-stage desorption vessel is introduced into the second-stage desorption vessel, which is filled with β-CD-PU porous cross-linked microspheres. The pressure and temperature are reduced to convert the carbon dioxide fluid containing byproducts into a subcritical fluid. The phytosterols enriched from the bottom of the second-stage desorption vessel are collected.

[0012] The subcritical fluid flowing out of the second-stage analytical vessel is introduced into the third-stage analytical vessel to reduce the pressure and collect the vitamin E concentrate precipitated from the bottom of the third-stage analytical vessel.

[0013] The fluid flowing out of the third-stage analytical vessel is introduced into a flash tank, where it is depressurized and cooled to vaporize carbon dioxide. Free fatty acids and odorous small molecule wastes precipitated from the bottom of the flash tank are collected.

[0014] By employing the above technical solution, supercritical carbon dioxide fluid is used instead of traditional vacuum high-temperature steam for deodorization, avoiding isomerization reactions in oils at high temperatures that generate trans fatty acids or polycyclic aromatic hydrocarbons, while preserving heat-sensitive micronutrients in the oils. The multi-stage desorption process separates substances step-by-step based on the changes in solubility of different components in carbon dioxide fluid with temperature and pressure. The state adjustment within the first-stage desorption vessel preferentially precipitates the main triglyceride component. The fluid enters the second-stage desorption vessel and transitions to a subcritical state, subsequently decreasing the system's density and solvation capacity, thus increasing the tendency for phytosterol precipitation.

[0015] In this stage, β-CD-PU porous cross-linked microspheres in the fixed bed play a separation role. The β-cyclodextrin units in the microspheres have a three-dimensional ring-shaped cavity structure with a hydrophilic outer side and a hydrophobic inner side. The spatial size and polarity distribution of the rigid steroidal ring backbone of the phytosterol molecule match this cavity structure, and the two form a host-guest inclusion complex through van der Waals forces and hydrophobic interactions. The polyurethane cross-linked backbone ensures uniform distribution of the fluid within the bed to increase the contact area, achieving the retention and enrichment of phytosterols. After a third-stage depressurization and flash evaporation process, vitamin E and small molecule volatile components are separated by solubility differences.

[0016] Preferably, the step of degumming pretreatment of the crude sunflower seed oil obtained by physical pressing before pumping it into the extraction tower specifically includes:

[0017] Heat the sunflower seed crude oil obtained by physical pressing to 45-55℃, add 1.5-2.5% of deionized water (equivalent to 1.5-2.5% of the mass of the pressed sunflower seed crude oil) and 0.05-0.15% of citric acid aqueous solution (equivalent to 0.05-0.15% of the mass of the pressed sunflower seed crude oil), and mechanically stir for 25-35 minutes.

[0018] The stirred sunflower seed crude oil was sent to a centrifuge for centrifugal separation to remove the heavy phase gum, thus obtaining degummed pretreated crude oil.

[0019] By employing the above technical solution, citric acid aqueous solution is added to promote the conversion of non-hydrated phospholipids in the oil to hydrated phospholipids. Combined with deionized water, this promotes hydration, causing colloidal impurities such as phospholipids to absorb water, swell, and coagulate. Mechanical stirring increases the probability of particle collision to promote floc growth, and centrifugation is used to remove the colloids. Pre-removal of colloids prevents the decline in mass transfer efficiency caused by colloids adhering to the inner wall of the equipment or the surface of the extraction tower packing during subsequent supercritical fluid extraction.

[0020] Preferably, the conditions for controlling supercritical extraction are as follows:

[0021] The pressure inside the extraction tower is 30-35 MPa, the temperature is 45-55℃, and the mass ratio of high-pressure pure carbon dioxide fluid to degummed pretreated crude oil is 25-35:1.

[0022] By adopting the above technical solution, the carbon dioxide fluid within this parameter range is in a supercritical state. At this time, the fluid has the characteristics of high density, low viscosity and high diffusion coefficient, which can dissolve triglyceride and volatile by-product molecules, and realize the phase separation of oil phase and insoluble impurities.

[0023] Preferably, in the first-stage analytical vessel, the pressure inside the first-stage analytical vessel is controlled to drop to 20-25 MPa and the temperature is adjusted to 45-50℃;

[0024] In the second-stage analytical vessel, the pressure inside is controlled to drop to 12-15 MPa and the temperature to 25-30℃;

[0025] In the third-stage desorption vessel, the pressure inside the vessel is controlled to drop to 8.0-10 MPa and the temperature is maintained at 25-30℃.

[0026] In the flash tank, the pressure inside the flash tank is controlled to drop to 3.0-4.0 MPa and the temperature is adjusted to 35-40℃.

[0027] By employing the above technical solution, the system establishes a stepped pressure and temperature reduction mechanism. The first-stage pressure drop alters the compatibility balance of triglycerides in carbon dioxide, causing the oil product to precipitate. The second-stage temperature and pressure reduction shifts the system into the subcritical range, facilitating the extraction of sterols in conjunction with adsorption materials. The third-stage pressure reduction decreases the fluid density, promoting the precipitation and settling of vitamin E. In the flash evaporator, the pressure drops below the critical point while the temperature rises, carbon dioxide vaporizes, and residual light components such as free fatty acids are separated.

[0028] Preferably, the process further includes the following steps: condensing the gaseous carbon dioxide discharged from the top of the flash tank, sending it to a compressor unit to be pressurized to 30-35 MPa and heated to 45-55°C, and then returning it to the bottom of the extraction tower for recycling.

[0029] By adopting the above technical solution, a closed-loop circulation of the extraction solvent is established. Gaseous carbon dioxide undergoes a state transition under pressure and heating to re-achieve supercritical conditions, reducing fluid consumption and material emissions during process operation.

[0030] Secondly, the present invention provides a method for preparing β-CD-PU porous crosslinked microspheres, using the following technical solution:

[0031] A method for preparing β-CD-PU porous crosslinked microspheres, wherein the β-CD-PU porous crosslinked microspheres are prepared by a crosslinking reaction of raw materials comprising the following parts by weight:

[0032] 100 parts anhydrous β-cyclodextrin; 15-20 parts polyethylene glycol; 45-55 parts hexamethylene diisocyanate; 0.5-1.0 parts dibutyltin dilaurate; the particle size of the β-CD-PU porous cross-linked microspheres is 100-200 mesh;

[0033] The specific preparation steps include:

[0034] Anhydrous β-cyclodextrin that has been thoroughly dried under vacuum is dissolved in anhydrous N,N-dimethylformamide. Nitrogen gas is introduced for protection, the temperature is raised to 65-70℃, and mechanical stirring is performed until the solution is completely dissolved to obtain the dissolved system.

[0035] After adding polyethylene glycol to the dissolving system and mixing it evenly, dibutyltin dilaurate is added dropwise; hexamethylene diisocyanate is dissolved in anhydrous N,N-dimethylformamide and slowly added dropwise to the dissolving system, and the reaction is continued at 65-70℃ to obtain cross-linked polymer gel.

[0036] The obtained cross-linked polymer gel was cooled to room temperature, broken up, and then extracted and washed with anhydrous ethanol and acetone respectively.

[0037] After washing, the washing product was vacuum dried, ground and sieved to obtain β-CD-PU porous cross-linked microspheres.

[0038] By employing the above technical solution, the material synthesis process is based on the chemical crosslinking mechanism of polyurethane. In the reaction system, hexamethylene diisocyanate has isocyanate groups at both ends. Under the catalysis of dibutyltin dilaurate, the isocyanate groups undergo nucleophilic addition reactions with the hydroxyl groups of anhydrous β-cyclodextrin and the hydroxyl groups of the polyethylene glycol end groups, generating a carbamate bond network. Hexamethylene diisocyanate acts as a rigid crosslinking agent, connecting the β-cyclodextrin monomers to form a three-dimensional structure. Polyethylene glycol, as a flexible polymer segment, is embedded in this network, increasing the flexibility of the network skeleton and expanding the crosslinking pore size.

[0039] The introduction of flexible segments alleviates the steric hindrance effect caused by the rigid cross-linking of simple cyclodextrin, allowing phytosterol molecules to pass through the pores and penetrate into the material's interior to bind with the cyclodextrin cavities. An anhydrous reaction environment prevents the isocyanate groups from reacting with water to generate carbon dioxide bubbles, thus avoiding structural defects. Washing and extraction with anhydrous ethanol and acetone removes unreacted small molecules and solvents from the pores, followed by vacuum drying and curing to obtain porous microspheres. The 100-200 mesh particle size ensures its fluid permeability in the fixed bed of the analytical reactor.

[0040] Preferably, the dripping time of hexamethylene diisocyanate is controlled to be 1.5-2.0 h, and the reaction time is controlled to be 6-8 h; the extraction and washing method is Soxhlet extraction for 10-14 h, and the vacuum drying conditions are vacuum drying at 55-65℃ for 20-28 h.

[0041] By employing the above technical solutions, extending the dropping time of the crosslinking agent controls the local concentration of active groups in the system, preventing excessively rapid reaction rates that could lead to self-polymerization and localized over-crosslinking, resulting in a crosslinked network with a uniform pore distribution. Soxhlet extraction, through heating and reflux of pure solvent, elutes unreacted monomers and catalyst residues embedded in the pores of the gel, improving the safety of the extracted material for use in edible oil processing systems.

[0042] This invention provides a method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts. It has the following beneficial effects:

[0043] 1. This invention employs supercritical carbon dioxide fluid for deodorization and combines it with a multi-stage desorption system to establish a gradient cooling and depressurization mechanism. Fluid deodorization operates under relatively mild temperature conditions, eliminating the reaction conditions for trans fatty acid formation found in traditional vacuum high-temperature steam deodorization systems, while retaining heat-sensitive nutrients within the system. Utilizing the differences in solubility of different components in carbon dioxide fluid with varying state parameters, the system continuously depressurizes and cools each stage of the desorption vessel and flash tank, causing the main components—triglycerides, phytosterols, vitamin E, and free fatty acids—to precipitate sequentially, thus achieving deodorization of oils and the independent, graded recovery of multiple byproducts.

[0044] 2. This invention incorporates β-CD-PU porous cross-linked microspheres within the second-stage analytical reactor. These microspheres introduce polyethylene glycol as a flexible segment into the polyurethane cross-linking system, expanding the pore size of the cross-linking network and mitigating steric hindrance, allowing phytosterol molecules to penetrate into the microspheres. Utilizing the hydrophobic cavity structure of β-cyclodextrin, which matches the spatial size and polarity distribution of phytosterol molecules, the material binds to sterol molecules to form inclusion complexes. This solves the problem of co-precipitation of components with similar molecular weights during subcritical fluid depressurization, achieving highly selective retention of phytosterols.

[0045] 3. This invention incorporates a dedicated degumming pretreatment step for sunflower seed crude oil before the fluid extraction process. By controlling the temperature and adding citric acid aqueous solution and deionized water, non-hydrated phospholipids are converted into hydrated phospholipids, which then absorb water and coagulate. Combined with mechanical stirring and centrifugation, the heavy phase colloids are removed in advance. This pretreatment eliminates the risk of colloidal impurities precipitating and adhering to the packing material or inner walls of the extraction tower or equipment pipelines in the subsequent high-pressure system, ensuring the mass transfer area between the supercritical fluid and the oil phase, and maintaining the operational stability of the entire continuous extraction and desorption system. Attached Figure Description

[0046] Figure 1 This is a comprehensive test chart of the physicochemical properties of the main product of this invention, refined sunflower seed oil.

[0047] Figure 2 Line graph showing the targeted enrichment verification of phytosterols and vitamin E, byproducts of this invention;

[0048] Figure 3 A bar chart comparing the mixing rates for verifying the step-down phase transition mechanism of this invention;

[0049] Figure 4 A comparison chart for the targeted affinity test of the custom polymer filler of this invention;

[0050] Figure 5 This is a comparative distribution diagram of the dynamic performance evolution test of the separation system of the present invention during continuous operation cycles, wherein, Figure 5(a) is a distribution diagram of the dynamic evolution test results of the pressure drop in the packing bed during a continuous operating cycle. Figure 5 (b) is a distribution diagram of the evolution test results of the single-pass rejection rate of phytosterols at the corresponding time points. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely 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.

[0052] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0053] Crude sunflower seed oil is commercially available pressed crude oil with an initial acid value of 2.5-3.5 mg KOH / g, a phosphorus content of 150-250 mg / kg, a moisture and volatile matter content of 0.15-0.25 wt%, an initial phytosterol content of 2500-3500 mg / kg, and an initial vitamin E content of 600-800 mg / kg.

[0054] Carbon dioxide is a commercially available high-purity gas with a purity of ≥99.99% and CAS number 124-38-9.

[0055] Anhydrous β-cyclodextrin is a commercially available biochemical reagent with a purity of ≥98.0% and a moisture content of ≤1.0%. Its CAS number is 7585-39-9.

[0056] Hexamethylene diisocyanate is a commercially available analytical grade reagent with a purity of ≥99.0% and CAS number 822-06-0.

[0057] Polyethylene glycol is a commercially available chemically pure reagent with a number average molecular weight range of 380-420, a hydroxyl value range of 268-294 mgKOH / g, and a CAS number of 25322-68-3.

[0058] N,N-Dimethylformamide is a commercially available anhydrous analytical grade reagent with a purity of ≥99.8% and a moisture content of ≤0.005%. Its CAS number is 68-12-2.

[0059] Dibutyltin dilaurate is a commercially available analytical grade reagent with a purity of ≥95.0% and CAS number 77-58-7.

[0060] Preparation Examples 1-3:

[0061] Preparation Example 1:

[0062] This preparation example provides a method for preparing β-CD-PU porous crosslinked microspheres, including the following steps:

[0063] Dissolve 100g of fully vacuum-dried anhydrous β-cyclodextrin in 350g of anhydrous N,N-dimethylformamide, purge with nitrogen for protection, heat to 68℃, and mechanically stir until completely dissolved.

[0064] After adding 18g of polyethylene glycol and mixing evenly, 0.8g of dibutyltin dilaurate was added dropwise; 50g of hexamethylene diisocyanate was dissolved in 50g of anhydrous N,N-dimethylformamide and slowly added dropwise to the above reaction system through a constant pressure dropping funnel, controlling the dropping time to 1.8h, and maintaining the system temperature at 68℃ to continue the reaction for 7h to obtain cross-linked polymer gel;

[0065] The obtained cross-linked polymer gel was cooled to room temperature, crushed, and then subjected to Soxhlet extraction with anhydrous ethanol and acetone for 10 h each.

[0066] After washing, the product was placed in a vacuum dryer at 60°C for 24 hours, and then ground and sieved to collect particles with a particle size of 100-200 mesh, thus obtaining β-CD-PU porous cross-linked microspheres.

[0067] Preparation Example 2:

[0068] This preparation example provides a method for preparing β-CD-PU porous crosslinked microspheres, including the following steps:

[0069] Dissolve 100g of fully vacuum-dried anhydrous β-cyclodextrin in 300g of anhydrous N,N-dimethylformamide, purge with nitrogen for protection, heat to 65℃, and mechanically stir until completely dissolved;

[0070] After adding 15g of polyethylene glycol and mixing thoroughly, add 0.5g of dibutyltin dilaurate dropwise.

[0071] 45g of hexamethylene diisocyanate was dissolved in 50g of anhydrous N,N-dimethylformamide and slowly added dropwise to the above reaction system through a constant pressure dropping funnel. The dropping time was controlled at 1.5h, and the system temperature was maintained at 65℃ for another 6h to obtain a cross-linked polymer gel.

[0072] The obtained cross-linked polymer gel was cooled to room temperature, crushed, and then subjected to Soxhlet extraction with anhydrous ethanol and acetone for 14 h each.

[0073] After washing, the product was placed in a vacuum dryer at 60°C for 24 hours, and then ground and sieved to collect particles with a particle size of 100-200 mesh, thus obtaining β-CD-PU porous cross-linked microspheres.

[0074] Preparation Example 3:

[0075] This preparation example provides a method for preparing β-CD-PU porous crosslinked microspheres, including the following steps:

[0076] Dissolve 100g of fully vacuum-dried anhydrous β-cyclodextrin in 400g of anhydrous N,N-dimethylformamide, purge with nitrogen for protection, heat to 70℃, and mechanically stir until completely dissolved;

[0077] After adding 20g of polyethylene glycol and mixing evenly, 1.0g of dibutyltin dilaurate was added dropwise; 55g of hexamethylene diisocyanate was dissolved in 50g of anhydrous N,N-dimethylformamide and slowly added dropwise to the above reaction system through a constant pressure dropping funnel, controlling the dropping time to 2.0h, and maintaining the system temperature at 70℃ to continue the reaction for 8h to obtain cross-linked polymer gel;

[0078] The obtained cross-linked polymer gel was cooled to room temperature, crushed, and then subjected to Soxhlet extraction with anhydrous ethanol and acetone for 10-14 h respectively. After washing, the product was placed in vacuum drying at 60℃ for 24 h, ground and sieved to collect particles with a particle size of 100-200 mesh, thus obtaining β-CD-PU porous cross-linked microspheres.

[0079] Examples 1-4:

[0080] Example 1:

[0081] This embodiment provides a method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts, including the following steps:

[0082] The pressed sunflower seed crude oil is pumped into a preheating tank and heated to 50°C.

[0083] Add 2.0% by weight of deionized water and 0.10% by weight of crude oil of 45wt% citric acid aqueous solution, and mechanically stir at 70 r / min for 30 min.

[0084] The treated crude oil was centrifuged at 4000 r / min using a horizontal screw centrifuge to remove the heavy phase colloids, yielding degummed pretreated crude oil. The obtained pretreated crude oil was then continuously pumped into the middle of the extraction tower using a high-pressure plunger pump at a flow rate of 65 L / h.

[0085] High-pressure pure carbon dioxide fluid is pumped into the bottom of the extraction tower, and the pressure inside the extraction tower is controlled at 32.5 MPa and the temperature at 50°C. The mass ratio of carbon dioxide to crude oil is 30:1. The supercritical extract phase discharged from the top of the tower is collected.

[0086] Insoluble impurities are discharged from the bottom of the column. The supercritical extraction phase overflowing from the top of the column is introduced into the first-stage desorption vessel. The pressure inside the vessel is controlled to decrease to 22.5 MPa and the temperature is adjusted to 48°C by using a back pressure valve. The liquid separated from the bottom of the first-stage desorption vessel is collected, which is the refined sunflower seed oil product. The carbon dioxide fluid containing by-products discharged from the top of the first-stage desorption vessel is introduced into the second-stage desorption vessel, which is filled with β-CD-PU porous cross-linked microspheres obtained in Preparation Example 1, through a heat exchange and pressure reduction valve group. The pressure inside the vessel is controlled to decrease to 13.5 MPa and the temperature is adjusted to 28°C, and the fluid is converted to a subcritical state. The phytosterol enrichment precipitated from the bottom of the vessel is collected.

[0087] The subcritical fluid exiting the second-stage desorption vessel is introduced into the third-stage desorption vessel. The pressure inside the vessel is controlled to drop to 9.0 MPa, and the temperature is maintained at 28°C. The vitamin E concentrate precipitated at the bottom of the vessel is collected. The fluid exiting the third-stage desorption vessel is introduced into a flash evaporator. The pressure inside the flash evaporator is controlled to drop to 3.5 MPa, and the temperature is adjusted to 38°C to allow the carbon dioxide to completely vaporize. The free fatty acids and off-odor small molecule byproducts precipitated at the bottom of the flash evaporator are collected. The gaseous carbon dioxide at the top of the flash evaporator is condensed and sent to the compressor unit, pressurized to 32.5 MPa, and heated to 50°C. It is then returned to the bottom of the extraction tower for recycling.

[0088] Example 2:

[0089] This embodiment provides a method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts, including the following steps:

[0090] The pressed sunflower seed crude oil is pumped into a preheating tank and heated to 45°C.

[0091] Add 1.5% (by weight of crude oil) of deionized water and 0.05% (by weight of crude oil) of a 55wt% citric acid aqueous solution, and mechanically stir at 60 r / min for 25 min.

[0092] The treated crude oil was centrifuged at 3500 r / min using a horizontal screw centrifuge to remove the heavy phase colloids, yielding degummed pretreated crude oil. The obtained pretreated crude oil was then continuously pumped into the middle of the extraction tower using a high-pressure plunger pump at a flow rate of 50 L / h.

[0093] High-pressure pure carbon dioxide fluid is pumped into the bottom of the extraction tower, and the pressure inside the extraction tower is controlled at 30 MPa and the temperature at 45°C. The mass ratio of carbon dioxide to crude oil is 25:1. The supercritical extract phase discharged from the top of the tower is collected.

[0094] Insoluble impurities are discharged from the bottom of the column. The supercritical extraction phase overflowing from the top of the column is introduced into the first-stage desorption vessel. The pressure inside the vessel is reduced to 20 MPa and the temperature is adjusted to 45°C by using a back pressure valve. The liquid separated from the bottom of the first-stage desorption vessel is collected, which is the refined sunflower seed oil product. The carbon dioxide fluid containing by-products discharged from the top of the first-stage desorption vessel is introduced into the second-stage desorption vessel, which is filled with β-CD-PU porous cross-linked microspheres obtained in Preparation Example 2, through a heat exchange and pressure reduction valve group. The pressure inside the vessel is reduced to 12 MPa and the temperature is reduced to 25°C, and the fluid is converted to a subcritical state. The phytosterol enrichment precipitated from the bottom of the vessel is collected.

[0095] The subcritical fluid exiting the second-stage analytical vessel is introduced into the third-stage analytical vessel. The pressure inside the vessel is controlled to drop to 8.0 MPa and the temperature is maintained at 25°C. The vitamin E concentrate precipitated at the bottom of the vessel is collected. The fluid exiting the third-stage analytical vessel is introduced into a flash evaporator. The pressure inside the flash evaporator is controlled to drop to 3.0 MPa and the temperature is adjusted to 35°C to completely vaporize the carbon dioxide. The free fatty acids and odorous small molecule waste precipitated at the bottom of the flash evaporator are collected.

[0096] The gaseous carbon dioxide at the top of the flash tank is condensed and sent to the compressor unit, pressurized to 30MPa and heated to 45℃, and then returned to the bottom of the extraction tower for recycling.

[0097] Example 3:

[0098] This embodiment provides a method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts, including the following steps:

[0099] The pressed sunflower seed crude oil is pumped into a preheating tank and heated to 55°C.

[0100] Add 2.5% by weight of deionized water and 0.15% by weight of crude oil of citric acid aqueous solution with a concentration of 45-55wt%, and mechanically stir at 80 r / min for 35 min.

[0101] The treated crude oil was centrifuged at 4500 r / min using a horizontal screw centrifuge to remove the heavy phase colloids, yielding degummed pretreated crude oil. The obtained pretreated crude oil was then continuously pumped into the middle of the extraction tower using a high-pressure plunger pump at a flow rate of 80 L / h.

[0102] High-pressure pure carbon dioxide fluid is pumped into the bottom of the extraction tower, and the pressure inside the extraction tower is controlled at 35 MPa and the temperature at 55 °C. The mass ratio of carbon dioxide to crude oil is 35:1. The supercritical extract phase discharged from the top of the tower is collected.

[0103] Insoluble impurities are discharged from the bottom of the column. The supercritical extraction phase overflowing from the top of the column is introduced into the first-stage desorption vessel. The pressure inside the vessel is reduced to 25 MPa and the temperature is adjusted to 50°C by a back pressure valve. The liquid separated from the bottom of the first-stage desorption vessel is collected, which is the refined sunflower seed oil product. The carbon dioxide fluid containing by-products discharged from the top of the first-stage desorption vessel is introduced into the second-stage desorption vessel, which is filled with β-CD-PU porous cross-linked microspheres obtained in Preparation Example 3, through a heat exchange and pressure reduction valve group. The pressure inside the vessel is reduced to 15 MPa and the temperature is reduced to 30°C, and the fluid is converted to a subcritical state. The phytosterol enrichment precipitated from the bottom of the vessel is collected.

[0104] The subcritical fluid exiting the second-stage analytical vessel is introduced into the third-stage analytical vessel. The pressure inside the vessel is controlled to drop to 10 MPa and the temperature is maintained at 30°C. The vitamin E concentrate precipitated at the bottom of the vessel is collected. The fluid exiting the third-stage analytical vessel is introduced into a flash evaporator. The pressure inside the flash evaporator is controlled to drop to 4.0 MPa and the temperature is adjusted to 40°C to allow carbon dioxide to completely vaporize. The free fatty acids and off-odor small molecule waste precipitated at the bottom of the flash evaporator are collected.

[0105] The gaseous carbon dioxide at the top of the flash tank is condensed and sent to the compressor unit, pressurized to 35MPa and heated to 55℃, and then returned to the bottom of the extraction tower for recycling.

[0106] Example 4:

[0107] This embodiment provides a method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts, including the following steps:

[0108] The pressed sunflower seed crude oil is pumped into a preheating tank and heated to 50°C.

[0109] Add 2.0% (by weight of crude oil) of deionized water and 0.10% (by weight of crude oil) of a 45-55 wt% citric acid aqueous solution, and mechanically stir at 70 r / min for 30 min.

[0110] The treated crude oil was centrifuged at 4000 r / min using a horizontal screw centrifuge to remove the heavy phase colloids, yielding degummed pretreated crude oil. The obtained pretreated crude oil was then continuously pumped into the middle of the extraction tower using a high-pressure plunger pump at a flow rate of 60 L / h.

[0111] High-pressure pure carbon dioxide fluid is pumped into the bottom of the extraction tower, and the pressure inside the extraction tower is controlled at 33 MPa and the temperature at 48°C. The mass ratio of carbon dioxide to crude oil is 32:1. The supercritical extract phase discharged from the top of the tower is collected.

[0112] Insoluble impurities are discharged from the bottom of the column. The supercritical extraction phase overflowing from the top of the column is introduced into the first-stage desorption vessel. The pressure inside the vessel is reduced to 23 MPa and the temperature is adjusted to 46°C by a back pressure valve. The liquid separated from the bottom of the first-stage desorption vessel is collected, which is the refined sunflower seed oil product. The carbon dioxide fluid containing by-products discharged from the top of the first-stage desorption vessel is introduced into the second-stage desorption vessel, which is filled with β-CD-PU porous cross-linked microspheres obtained in Preparation Example 1, through a heat exchange and pressure reduction valve group. The pressure inside the vessel is reduced to 13 MPa and the temperature is reduced to 26°C, and the fluid is converted to a subcritical state. The phytosterol enrichment precipitated from the bottom of the vessel is collected.

[0113] The subcritical fluid exiting the second-stage analytical vessel is introduced into the third-stage analytical vessel. The pressure inside the vessel is controlled to drop to 9.5 MPa and the temperature is maintained at 26°C. The vitamin E concentrate precipitated at the bottom of the vessel is collected. The fluid exiting the third-stage analytical vessel is introduced into a flash evaporator. The pressure inside the flash evaporator is controlled to drop to 3.8 MPa and the temperature is adjusted to 38°C to completely vaporize the carbon dioxide. The free fatty acids and odorous small molecule waste precipitated at the bottom of the flash evaporator are collected.

[0114] The gaseous carbon dioxide at the top of the flash tank is condensed and sent to the compressor unit, pressurized to 33MPa and heated to 48℃, and then returned to the bottom of the extraction tower for recycling.

[0115] Comparative Examples 1-5:

[0116] Comparative Example 1:

[0117] Compared with Example 1, the difference is that the subcritical step-by-step desorption process of the second and third stage desorption vessels is omitted. The carbon dioxide fluid containing by-products discharged from the top of the first stage desorption vessel is directly introduced into the flash tank. The pressure inside the tank is controlled to be reduced to 3.5 MPa and the temperature is adjusted to 38°C to completely vaporize the carbon dioxide and collect the mixed by-products at the bottom of the tank. All other aspects are the same.

[0118] Comparative Example 2:

[0119] Compared with Example 1, the difference is that the second-stage desorption vessel was not filled with β-CD-PU porous cross-linked microspheres, but was used as an empty vessel for direct subcritical decompression desorption of the fluid; all other aspects were the same.

[0120] Comparative Example 3:

[0121] Compared with Example 1, the difference is that the pressure parameters of the step-down pressure reduction are changed, and the pressure of the first-stage desorption vessel is directly reduced to 13.5 MPa and the temperature is reduced to 28°C, skipping the first-stage micro-pressure reduction precipitation step of 22.5 MPa in Example 1. All other aspects are the same.

[0122] Comparative Example 4:

[0123] Compared with Example 1, the difference is that the β-CD-PU porous cross-linked microspheres packed in the second-stage analytical vessel were replaced with an equal weight of ordinary commercially available uncross-linked β-cyclodextrin powder, while all other aspects were the same.

[0124] Comparative Example 5:

[0125] Compared with Example 1, the difference is that the β-CD-PU porous cross-linked microspheres packed in the second-stage analytical vessel are replaced with an equal weight of commercially available conventional coarse-porous silica gel, while all other aspects are the same.

[0126] Test Examples 1-5:

[0127] Test Example 1:

[0128] Take 500g of each of the crude sunflower seed oil concentrate, the finished oil after treatment in Comparative Example 1, and the refined sunflower seed oil separated from the bottom of the first-stage analytical vessel in Examples 1 to 4. Place them in a clean, brown, light-proof glass bottle as independent test objects, fill with an appropriate amount of nitrogen to purge the air from the top, seal and store in a cool place for later use.

[0129] To determine the residual free fatty acid content, i.e., acid value, accurately weigh 5.0 g of each test sample and place it in an Erlenmeyer flask. Add 50 mL of pre-neutralized isopropanol-ethyl ether mixed solvent (volume ratio 1:1) and gently shake to dissolve the oil in the solvent phase. Add 3 to 5 drops of phenolphthalein indicator and perform manual titration using a 0.1 mol / L potassium hydroxide standard titration solution. During the operation, keep the Erlenmeyer flask continuously swirling until the system turns a faint pink color that does not fade within a 30-second time span. Record the volume of titrant consumed and calculate the acid value of the sample.

[0130] For the analysis of the purity of the main product, i.e., the relative content of triglycerides, 0.1 g of each oil sample was weighed and dissolved in 10 mL of chromatographic grade n-hexane. The distribution of macromolecular lipids in the mixture was detected using a high-performance gas chromatograph equipped with a flame ionization detector. A high-temperature resistant DB-5HT capillary column was used for the separation channel. The injection port temperature was set at 360℃, and the detector temperature was set at 370℃ to ensure component vaporization. A predetermined temperature gradient curve was run, and after acquiring the chromatograms, the relative mass fraction of triglycerides in the total lipids was calculated using the area normalization algorithm of the chromatography workstation.

[0131] For targeted quantification of odor-causing molecules, 2.0 g of each sample was placed in a 20 mL standard headspace extraction bottle. Headspace solid-phase microextraction (HSP) was used to continuously expose the adsorption fiber head to the system at a constant temperature of 60 °C for 40 min, enriching trace odor molecules volatilized from the top of the system. Immediately after adsorption, the fiber head was punctured and introduced into the high-temperature injection port of a gas chromatography-mass spectrometry (GC-MS) instrument, where it was thermally desorbed at 250 °C for 5 min. Hexanal, a representative substance of common bean odor, was used as the characteristic detection target for targeted quantification on the mass spectrometer. A working curve was plotted using an external standard reference of known concentration, and the residual amount of hexanal in each test sample was calculated.

[0132] Table 1. Test data of basic physicochemical properties of main products for each group of test samples.

[0133] Test object Acid value (mgKOH / g) Triglyceride purity (%) Hexanal residue (mg / kg) Sunflower seed crude oil 3.14 92.61 16.48 Comparative Example 1: Refined Oil 0.12 98.24 0.15 Example 1 Finished Oil 0.16 99.13 0.38 Example 2 Finished Oil 0.29 98.47 0.86 Example 3 Finished Oil 0.19 98.82 0.44 Example 4 Finished Oil 0.17 99.01 0.41

[0134] Figure 1 The data distribution of triglyceride purity on the left vertical axis is presented as a bar chart, and the data distribution of acid value and residual amount of hexanal, a characteristic odor-causing substance, on the right vertical axis is presented as a line chart; the test objects corresponding to the horizontal axis from left to right are sunflower seed crude oil, comparative example 1, example 1, example 2, example 3, and example 4.

[0135] According to Table 1, sunflower seed crude oil exhibits the physicochemical characteristics of conventional crude oil before intervention, containing a relatively high amount of free fatty acids and off-flavor molecules. After treatment with the monotonically decreasing pressure phase change system configured in Examples 1 to 4, the acid value of the main product collected in the first-stage desorption vessel decreased to below 0.3 mg KOH / g, the hexanal residue also showed a decreasing trend, and the triglyceride purity of the oil increased to over 98%. This change in macroscopic data reflects the role of the fluid phase change repulsion mechanism in the actual process.

[0136] When supercritical carbon dioxide fluid carries the full-component extract into a slightly depressurized environment, the decrease in medium density alters the original solvation equilibrium, thereby physically repelling the larger triglycerides in the system.

[0137] According to Chrastil's solubility rule in thermodynamic systems, larger molecules are more sensitive to changes in solvent density, causing triglycerides to preferentially precipitate from their dissolved state. In contrast, free fatty acids and volatile aldehydes and ketones, due to their smaller size and polarity, remain in the depressurized fluid medium. This separation mechanism based on differences in physical properties avoids the intervention of an external thermal field.

[0138] Analysis of the data from the thermal deodorization technology used in Comparative Example 1 shows that, under the synergistic effect of conventional high temperature and vacuum, acid value and odor substances were indeed removed; however, the purity of the main component, triglycerides, decreased slightly. The sustained high-temperature environment easily induces trace thermal polymerization and isomerization of unsaturated lipid molecules, indicating that this conventional process can affect the intact configuration of oil molecules when removing impurities.

[0139] This scheme achieves equivalent deodorization and deacidification effects through density phase balance adjustment. Combined with the specific retention level of triglycerides in the examples, it confirms that the extraction using low-temperature supercritical media has mild operation and reduces common thermal degradation side reactions in the process from the process operation stage.

[0140] Test Example 2:

[0141] Take 100g of each of the solid-liquid mixtures continuously collected from the bottom of the second-stage and third-stage analytical vessels under stable system operation conditions in Examples 1 to 4. Place the obtained materials in a light-proof fume hood for natural air drying. After the residual carbon dioxide gas has completely dissipated, store them in a freezer at -18°C for later use as test samples for subsequent chromatographic analysis.

[0142] Quantitative analysis of phytosterols in the product of the second-stage analytical reactor was performed. 0.05 g of the sample was accurately weighed and dissolved in 25 mL of chromatographic grade isopropanol, then filtered through a 0.22 μm polytetrafluoroethylene microporous membrane to prepare the injection solution. The injection solution was separated and determined using a high-performance liquid chromatograph equipped with a variable wavelength ultraviolet detector. A C18 reversed-phase column was used, with a mobile phase of methanol and water at a volume ratio of 98:2, and the detection wavelength was set at 205 nm. An external standard calibration curve was established based on a pre-prepared mixture of phytosterol standards with known concentration gradients. The absolute mass fraction of phytosterols in the sample was calculated, and the recovery rate for the entire cycle was calculated based on the total weight of the material.

[0143] For the determination of vitamin E content in the product from the third-stage analytical reactor, an equal mass of the sample to be tested was dissolved in hexane. The instrument's detection end was switched to a fluorescence detector, the excitation wavelength was set to 295 nm, and the emission wavelength was adjusted to 330 nm. A 99:1 mixture of hexane and isopropanol was used as the elution mobile phase. Based on the peak area integral results of the tocopherol standard, the purity of vitamin E in different batches of product and the corresponding retention and recovery rates were derived.

[0144] Table 2. Test data on purity and recovery rate of by-products from each stage of the analytical reactor in the examples.

[0145] Test object Phytosterol purity (%) Phytosterol recovery rate (%) Vitamin E purity (%) Vitamin E recovery rate (%) Example 1 82.41 89.15 68.32 81.04 Example 2 75.63 78.42 61.15 70.83 Example 3 76.98 80.27 64.29 74.56 Example 4 80.14 85.36 66.81 79.22

[0146] Figure 2The diagram shows the purity and recovery rate of the products collected in the second and third stage analytical reactors for each embodiment. The left vertical axis corresponds to the purity of phytosterols and vitamin E, and the right vertical axis corresponds to the recovery rate of the two substances; the test objects on the horizontal axis, from left to right, are Example 1, Example 2, Example 3, and Example 4.

[0147] Based on the quantitative chromatographic data presented in Table 2, the target byproducts were enriched in the corresponding collection vessels in all four examples under specific pressure gradient parameters. In previous oil processing procedures, the extraction of trace amounts of sterols and tocopherols from complex distillates often relied on thermal separation methods such as esterification or multiple vacuum distillations.

[0148] This invention employs a set stepwise pressure reduction parameter to induce a shift in the physicochemical properties of a supercritical fluid as it crosses the critical point and enters the subcritical state. When the system pressure is reduced to 12-15 MPa in the second-stage desorption vessel, the decrease in fluid density disrupts the dissolution equilibrium of phytosterols. Utilizing the crystallization-friendly properties of the large molecular rigid framework and the spatial envelopment effect of the affinity packing pores, phytosterols reach local supersaturation at this thermodynamic node and crystallize and precipitate. As the fluid continues to flow, the system pressure decreases further to 8-10 MPa before entering the third-stage desorption vessel. At this point, vitamin E, with its more flexible molecular structure and certain vapor pressure, loses the density support required to maintain its dissolved state, resulting in phase separation. This density difference response mechanism, dependent on pressure fine-tuning, constitutes the fundamental pathway for substance separation in this scheme.

[0149] Comparison of the test groups reveals that Example 1, as a middle-range combination within the parameter range, exhibits relatively balanced product purity and recovery rates. When Example 2 and Example 3 operate with altered pressure boundary conditions, the operational shifts between the low-pressure and high-pressure sides cause fluctuations in product purity data, and the overall recovery rate also decreases. This phenomenon indicates that the forward or backward shift of the phase transition node can lead to cross-dissolution and precipitation of some lipid components at unsuitable density stages. The precision of controlling the pressure drop threshold in engineering operations directly affects the clarity of the phase equilibrium separation boundary. Through the orderly switching of thermodynamic states, micronutrients are stripped without altering their original configuration, verifying the applicability of the multi-stage phase transition mechanism in continuous fluid separation processes.

[0150] Test Example 3:

[0151] Measure 200g of the liquid phase product continuously collected from the bottom of the first-stage analytical vessel in Example 1 and the first-stage analytical vessel in Comparative Example 3, and dispense them into glass containers as samples for the mixing rate comparison test.

[0152] To determine the contamination of free fatty acids in the main product, 10.0 g of each test sample was weighed and placed in an Erlenmeyer flask. 50 mL of neutral isopropanol-ethyl ether mixture was added to dissolve the sample. Titration was performed using a standardized potassium hydroxide solution. The volume of titrant consumed when the solution changed color and remained unchanged for a set time was recorded. The mass fraction of free fatty acids was obtained through chemical conversion, serving as a quantitative indicator for evaluating the removal status of free fatty acids.

[0153] To assess the contamination levels of phytosterols and vitamin E in the main oil body, 2.0 g of each test sample was weighed and saponified in a prepared potassium hydroxide-ethanol solution. Unsaponifiable matter was extracted multiple times using n-hexane. The combined extracts were concentrated by nitrogen purging, diluted to volume using a mobile phase, and filtered through a microporous membrane to prepare the chromatographic injection solution. A high-performance liquid chromatography (HPLC) system was started and a preset separation method was loaded. The absolute content of trace substances in the product was calculated based on retention time and peak area response values, thereby obtaining data on the contamination of phytosterols and vitamin E.

[0154] Table 3. Comparative Test Data for Verification of Stepped Voltage Drop Phase Transition Mechanism

[0155] Test object Free fatty acid inclusion rate (%) Phytosterol contamination rate (mg / kg) Vitamin E inclusion rate (mg / kg) Example 1 0.08 12.4 18.7 Comparative Example 1 1.56 2845.6 712.3 Comparative Example 3 0.42 2156.8 305.2

[0156] Figure 3 The left vertical axis corresponds to the data on the free fatty acid contamination rate, presented as a line graph; the right vertical axis, using a logarithmic coordinate system to accommodate the data span, corresponds to the data on the contamination rates of phytosterols and vitamin E, presented as a side-by-side bar chart. The horizontal axis covers the test objects from left to right as Example 1 and Comparative Example 3.

[0157] According to the data in Table 3, the main oil collected at the first desorption node in Example 1 exhibited a low impurity loading. In engineering practice, controlling the step-down pressure reduction range forms the basis for establishing the separation path. The data feedback from Comparative Example 3 shows the intervention results after changing the operational variables. When the first-stage desorption pressure was directly reduced to 13.5 MPa, bypassing the set buffer zone, the decrease in fluid density caused triglycerides to exit the dissolved state, disrupting the dissolution critical point of sterols. The bypass-stage decompression operation induced a co-precipitation effect between different components, manifested as most phytosterols and some vitamin E being retained in the main product oil phase.

[0158] Fluid density exhibits a non-linear variation with pressure, and lipids of different molecular weights and spatial configurations precipitate sequentially according to their solubility curves in this physical environment. Setting a small, gradual pressure reduction range ensures that triglycerides are preferentially separated while maintaining controllable impurity levels. Segmented thermodynamic parameters establish physical isolation zones for material screening within the fluid network, transforming the complex mixed oil system into a purified product that can be recovered stepwise.

[0159] Test Example 4:

[0160] Lipids were collected from the bottom of the second-stage and third-stage analytical reactors during continuous and stable operation of Examples 1, 2, and 4. These materials were placed in a low-temperature vacuum drying oven to remove residual moisture and encapsulated gas, and stored as experimental analytical samples for evaluating the targeted affinity separation effect.

[0161] To determine the capture purity and crystallization rate of phytosterols in the second-stage analytical vessel, 0.1 g of each group of second-stage product samples were accurately weighed and dissolved ultrasonically using a mixed solvent of chloroform and methanol. The supernatant was extracted by centrifugation, filtered through a polytetrafluoroethylene (PTFE) membrane, and injected into a liquid chromatography system. The chromatographic response signal was read using a UV detector at the set absorption wavelength. The mass percentage of phytosterols in the mixture was calculated based on a pre-recorded standard calibration curve to determine the capture purity, and the overall crystallization rate was calculated by combining this with the total amount of feed to the system.

[0162] To address the cross-contamination of vitamin E in the third-stage products, samples collected from each group's third-stage analytical vessel were diluted to volume with chromatographic-grade n-hexane. The elution gradient of the liquid chromatography mobile phase was adjusted, and the response values ​​of the delayed-eluting sterol components in the eluent were recorded to quantify their mass fraction in the total lipid collection of the third stage. This value reflects the flow of phytosterols that should have precipitated in the previous stage into the next stage system, thus defining the cross-contamination rate of sterols to vitamin E products.

[0163] Table 4. Comparative Test Data on Targeted Affinity of Custom Polymer Fillers

[0164] Test object Secondary sterol crystallization rate (%) Secondary sterol capture purity (%) Sterol cross-contamination rate (%) of third-level vitamin E products Example 1 89.15 82.41 1.25 Comparative Example 2 34.27 41.52 28.94 Comparative Example 4 58.63 62.18 15.42

[0165] Figure 4 The vertical axis uses percentage data and corresponds to the three sets of test indicators mentioned above. The presentation format is a grouped bar chart under the same coordinate system. The horizontal axis covers the test objects from left to right as Example 1, Comparative Example 2, and Comparative Example 4.

[0166] According to the data in Table 4, in Example 1, within a system environment packed with β-CD-PU porous cross-linked microspheres, the precipitation rate and capture purity of phytosterols in the second-stage desorption vessel both reached levels exceeding 80%, while the cross-contamination rate of the third-stage products was controlled at 1.25%. The acquisition of this separation data is related to the gradient setting of the system pressure and also to the physical environment of the internal pores of the packing microspheres. When the subcritical fluid passes through the packing bed, the hydrophobic cavity size of β-cyclodextrin matches the spatial configuration of the sterol molecules, resulting in non-covalent host-guest affinity. The local concentration changes within the pores and exceeds the saturation limit, promoting the crystallization of sterol molecules on the packing surface and in the interstices.

[0167] Comparative Example 2, using an empty reactor without packing material and performing the same depressurization process, showed a sterol precipitation rate reduced to 34.27%. Without a porous medium to provide nucleation sites and envelope fixation, the decrease in fluid density alone was insufficient to remove sterols from their dissolved state within the set residence time. The delay in the phase transition process caused uncrystallized sterols to migrate downstream with the carbon dioxide medium, co-precipitating with vitamin E in the third-stage desorption reactor, resulting in 28.94% cross-contamination. Observations during the experiment indicate that the morphological retention state of the powder material in the high-pressure fluid interferes with the contact efficiency of the gas-liquid-solid three-phase system.

[0168] Comparative Example 4 used ordinary uncrosslinked β-cyclodextrin powder for testing, reflecting the influence of the material's physical structure. The powder without polyurethane crosslinking modification agglomerated under high-pressure fluid scouring, and the reduced specific surface area weakened its ability to capture target molecules. Conventional powders could not maintain uniform dispersion under dynamic fluid pressure differentials, limiting the effectiveness of the affinity mechanism. Combining the component distribution of each group of test objects, it can be found that polyurethane crosslinking treatment endows porous microspheres with structural stability against fluid shear, ensuring the exposure of affinity sites and establishing the basic conditions for targeted retention of trace components in subcritical fluid continuous separation systems.

[0169] Test Example 5:

[0170] The supercritical extraction separation systems of Examples 1, 4, and 5 were started and subjected to continuous fluid processing for a total duration of 80 hours while maintaining constant feed input rate and pressure gradient parameters. At the 20th, 40th, 60th, and 80th hour intervals, the fluid pressure difference data across the second-stage analytical vessel was read, and the solid-liquid mixture discharged from the bottom valve during these time periods was collected simultaneously for analysis.

[0171] To obtain the pressure drop variation of the packed bed, high-precision micro differential pressure transmitters located at the fluid inlet and outlet sides of the second-stage desorption reactor were used to record the dynamic pressure drop values ​​at corresponding time points. This data is used to evaluate the resistance change when high-pressure fluid continuously passes through the media layer, thereby reflecting the structural stability and anti-clogging performance of the separation packing under dynamic operating conditions.

[0172] In determining the single-pass rejection rate of the target by-products, the eluent collected at each time point was vacuum dried to remove residual carbon dioxide solvent, and 0.2 g was weighed and dissolved in the pre-prepared liquid chromatography mobile phase. The absolute content of phytosterols in the injection solution was quantitatively integrated using high-performance liquid chromatography (HPLC), and compared with the theoretical total amount of phytosterols input from the feedstock during that time period. This was used to calculate the dynamic single-pass rejection rate, which measures the activity retention status of the separation medium during long-term service.

[0173] Table 5. Test data on the evolution of bed pressure drop and single-pass retention rate during continuous operation cycles.

[0174] Test object Running time (h) Bed pressure drop (MPa) Sterol single-pass retention rate (%) Example 1 20 0.12 88.42 Example 1 40 0.14 87.16 Example 1 60 0.17 85.39 Example 1 80 0.19 83.91 Comparative Example 4 20 0.25 55.28 Comparative Example 4 40 0.58 31.45 Comparative Example 4 60 1.12 18.73 Comparative Example 4 80 1.67 12.14 Comparative Example 5 20 0.15 72.54 Comparative Example 5 40 0.28 54.37 Comparative Example 5 60 0.44 38.62 Comparative Example 5 80 0.61 26.48

[0175] Figure 5 The horizontal axis of both subplot (a) and subplot (b) represents continuous operating time, corresponding to test time nodes of 20h, 40h, 60h, and 80h. The vertical axis of subplot (a) corresponds to the bed pressure drop value, and the vertical axis of subplot (b) corresponds to the sterol single-pass rejection rate. Both are presented as line graphs in the same coordinate system.

[0176] According to the data in Table 5, during the 80-hour continuous operation test cycle in Example 1, the pressure drop of the packing bed in the second-stage desorption vessel remained stable below 0.2 MPa, and the single-pass retention rate of phytosterols showed a slight decrease. In the industrial continuous extraction process of supercritical fluids, physical compaction of the separation medium and pore blockage are often the main causes of system shutdown and maintenance. Powder materials undergo irreversible physical compaction when subjected to continuous high-pressure fluid scouring. The dynamic monitoring data of Comparative Example 4 reflects the actual impact of this process. Due to the lack of external cross-linking framework support, ordinary β-cyclodextrin powder experienced bed caking in the early stage of operation, causing the fluid penetration resistance to rise to 1.67 MPa. With the occurrence of channel blockage and channeling phenomena, the contact area between the medium and the target product was reduced, and its retention capacity for sterol molecules dropped to 12.1% after 80 hours, losing its effectiveness in maintaining separation operation.

[0177] Comparative Example 5 used conventional coarse-porous silica gel as the control separation medium. Although its silica framework possessed initial structural strength, when processing complex mixed lipid systems containing free fatty acids, triglycerides, and trace amounts of concomitant substances, non-specific surface adsorption easily led to saturation of the packing pores. As non-target impurities accumulated inside the pores, the bed pressure drop showed an upward trend, and the single-pass rejection rate also dropped to 26.4% due to the consumption of surface area.

[0178] Based on continuous operation conditions at the experimental site, it was found that the porous microspheres constructed using a polyurethane cross-linked network exhibited shear and compaction resistance at the hydrodynamic level. This rigid cross-linked framework resisted high-density fluid pressure while maintaining the unobstructed flow of the internal network channels; the stable spatial structure ensured the continuous targeted affinity recognition between the host microspheres and guest sterol molecules. After undergoing long-term phase change extraction, the microsphere material maintained dual stability in morphology and separation activity, providing engineering application support for the continuous extraction of value-added trace components from crude oils.

Claims

1. A method for deodorizing sunflower seed oil with zero emissions and low water content, and for efficiently recovering byproducts, characterized in that... Includes the following steps: The degummed pretreated crude oil is continuously pumped into the middle of the extraction tower, and high-pressure pure carbon dioxide fluid is pumped in from the bottom of the extraction tower for supercritical extraction. The supercritical extract phase discharged from the top of the extraction tower is collected. The supercritical extract phase discharged from the top of the extraction tower is introduced into the first-stage desorption vessel for depressurization and cooling, and the refined sunflower seed oil product separated from the bottom of the first-stage desorption vessel is collected. The carbon dioxide fluid containing byproducts discharged from the top of the first-stage desorption vessel is introduced into the second-stage desorption vessel, which is filled with β-CD-PU porous cross-linked microspheres. The pressure and temperature are reduced to convert the carbon dioxide fluid containing byproducts into a subcritical fluid. The phytosterols enriched from the bottom of the second-stage desorption vessel are collected. The subcritical fluid flowing out of the second-stage analytical vessel is introduced into the third-stage analytical vessel to reduce the pressure and collect the vitamin E concentrate precipitated from the bottom of the third-stage analytical vessel. The fluid flowing out of the third-stage analytical vessel is introduced into a flash tank, where it is depressurized and cooled to vaporize carbon dioxide. Free fatty acids and odorous small molecule wastes precipitated from the bottom of the flash tank are collected.

2. The method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products according to claim 1, characterized in that, The degumming pretreatment step of the sunflower seed crude oil obtained by pressing before pumping it into the extraction tower specifically includes: Heat the pressed sunflower seed crude oil to 45-55℃, add 1.5-2.5% of deionized water (equivalent to 1.5-2.5% of the mass of the pressed sunflower seed crude oil) and 0.05-0.15% of citric acid aqueous solution (equivalent to 0.05-0.15% of the mass of the pressed sunflower seed crude oil), and mechanically stir for 25-35 minutes. The stirred sunflower seed crude oil was sent to a centrifuge for centrifugal separation to remove the heavy phase gum, thus obtaining degummed pretreated crude oil.

3. The method for deodorizing sunflower seed oil with zero emissions and low water content and efficiently recovering by-products according to claim 1, characterized in that, The conditions for controlling supercritical fluid extraction are: The pressure inside the extraction tower is 30-35 MPa, the temperature is 45-55℃, and the mass ratio of high-pressure pure carbon dioxide fluid to degummed crude oil is (25-35):

1.

4. The method for deodorizing sunflower seed oil with zero and low odor levels and efficiently recovering by-products according to claim 1, characterized in that, In the first-stage analytical vessel, the pressure inside the first-stage analytical vessel is controlled to drop to 20-25 MPa and the temperature is adjusted to 45-50℃; In the second-stage analysis vessel, the pressure inside the vessel is controlled to drop to 12-15 MPa and the temperature to 25-30℃.

5. The method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products according to claim 1, characterized in that, In the third-stage desorption vessel, the pressure inside the vessel is controlled to drop to 8.0-10 MPa and the temperature is maintained at 25-30℃. In the flash tank, the pressure inside the flash tank is controlled to drop to 3.0-4.0 MPa and the temperature is adjusted to 35-40℃.

6. The method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products according to claim 1, characterized in that, It also includes the following steps: The gaseous carbon dioxide discharged from the top of the flash tank is condensed, sent to the compressor unit to be pressurized to 30-35MPa and heated to 45-55℃, and then returned to the bottom of the extraction tower for recycling.

7. The method for deodorizing sunflower seed oil with zero emissions and low water content and efficiently recovering by-products according to claim 1, characterized in that, The β-CD-PU porous cross-linked microspheres are prepared by cross-linking reaction of the following raw materials in parts by weight: 100 parts of anhydrous β-cyclodextrin; 15-20 parts of polyethylene glycol; 45-55 parts of hexamethylene diisocyanate; 0.5-1.0 parts of dibutyltin dilaurate.

8. The method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products according to claim 7, characterized in that, The β-CD-PU porous cross-linked microspheres have a particle size of 100-200 mesh.

9. The method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products according to claim 7, characterized in that, The preparation steps of the β-CD-PU porous crosslinked microspheres include: Anhydrous β-cyclodextrin that has been thoroughly dried under vacuum is dissolved in anhydrous N,N-dimethylformamide. Nitrogen gas is introduced for protection, the temperature is raised to 65-70℃, and mechanical stirring is performed until the solution is completely dissolved to obtain the dissolved system. After adding polyethylene glycol to the solution and mixing thoroughly, dibutyltin dilaurate is added dropwise. Hexamethylene diisocyanate was dissolved in anhydrous N,N-dimethylformamide and slowly added dropwise to the solution system. The reaction was continued at 65-70℃ to obtain a cross-linked polymer gel. The obtained cross-linked polymer gel was cooled to room temperature, broken up, and then extracted and washed with anhydrous ethanol and acetone respectively. After washing, the washing product was vacuum dried, ground and sieved to obtain β-CD-PU porous cross-linked microspheres.

10. The method for deodorizing sunflower seed oil with zero and low odor levels and efficient recovery of by-products according to claim 9, characterized in that, The addition time of hexamethylene diisocyanate was controlled to be 1.5-2.0 h, and the reaction time was controlled to be 6-8 h. The extraction and washing process involves Soxhlet extraction for 10-14 hours, followed by vacuum drying at 55-65℃ for 20-28 hours.

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