Modified silica for efficient adsorption of oils and phospholipids, its preparation and application methods

Abstract

This invention discloses a modified silica for highly efficient adsorption of phospholipids in oils and fats, along with its preparation and application methods, belonging to the field of oil degumming technology. The specific process is as follows: silica with an average particle size of 10-50 μm is added to an aminosilane solution at 80-85℃ and reacted for 13-18 h. After the reaction, the mixture is filtered, and the solid product is dried to obtain amino-modified silica. This modified silica is then used to degumme oils and fats. The modified silica prepared by this invention exhibits stronger selective adsorption capacity for phospholipids and can remove phospholipids from oils and fats at relatively low temperatures (35-45℃), demonstrating excellent removal efficiency. Its maximum adsorption capacity can reach 1861.26 mg / g.

Description

Technical Field

[0001] This invention belongs to the field of oil degumming technology, specifically relating to a modified silica that efficiently adsorbs phospholipids from oils and its preparation and application methods. Background Technology

[0002] Vegetable oils, as important raw materials in the global food industry, bioenergy, and chemical industry, have become necessities for people's lives due to their rich content of nutrients such as phytosterols, vitamins, and carotenoids. After pressing or leaching, the unrefined pressed oil is called crude oil. Crude oil contains phospholipids, which are prone to flocculation, affecting the sensory quality and preservation of the oil. Furthermore, it easily foams and smokes during cooking, exacerbating the thermal instability of the oil and promoting its decomposition to produce unhealthy aldehydes and polycyclic aromatic hydrocarbons. Therefore, dephosphating and refining (also known as degumming) is an essential step in the production of edible oils. Typically, the phospholipid content in the refined oil is required to be less than 10 mg / kg (Journal of Oleo Science, 2022, 71(5): 721-733.).

[0003] Crude oil is classified into three types according to processing methods: cold-pressed, hot-pressed, and solvent-extracted crude oil. The phospholipid content varies depending on the processing method, ranging from 3-8 mg / g, 8-15 mg / g, and 15-25 mg / g, respectively. Phospholipids in crude oil are generally divided into hydrated phospholipids (HP) and non-hydrated phospholipids (NHP). Traditional dephosphating methods involve hydration and acidification, but these produce large amounts of oil residue and wastewater, resulting in reduced oil yield. Furthermore, traditional degumming methods cause significant loss of flavor and nutrients and are energy-intensive. In recent years, innovative methods such as enzymatic methods, membrane separation, and adsorption degumming have been developed. However, due to the high cost of enzymatic methods and the potential for membrane fouling in membrane separation, these two new technologies have not yet been industrialized.

[0004] Adsorption degumming technology has gradually emerged due to its advantages of high efficiency, low consumption, and environmental friendliness. Commonly used adsorbents in oil refining include attapulgite, kaolin, activated carbon, and silica. Silica (SiO2) is a common adsorbent material with a porous structure and has been applied in beer turbidity removal, salt anti-coagulation, and pigment adsorption. A study by Yao et al. reported the application of SiO2 in the degumming of rapeseed oil with a phospholipid content of 2.63 mg / g, finding that 85% of the phospholipids could be removed, with a dephosphorization amount per unit adsorbent (referred to as unit dephosphorization amount) of only 142.1 mg / g. ad. -1(Journal of Cleaner Production 268 (2020)122344). To improve the dephosphorization rate, Wang Weijun et al. modified silica and used phosphatidylethanolamine (PE) and SiO2 in a physical composite process to degumme rapeseed oil with a phosphorus content of 4.2 mg / g. Due to the weak interaction between SiO2 and PE, the dephosphorization rate was only 86.7% and the unit dephosphorization amount was only 483.1 mg / g under the optimized degumming process. ad. -1 (Chinese Journal of Oil Crops, 2021, 43(4)). Furthermore, R92, prepared by chemically modifying silica with citric acid, at an addition rate of 1.0% and an adsorption reaction at 45 °C for 30 min, resulted in a dephosphorization amount of 463.7 mg / g from rapeseed oil with a phosphorus content of 4.656 mg / g. ad. -1 Compared with conventional unmodified SiO2 (420.4 mg·g), ad. -1 The dephosphorization improvement rate was only 10% (Food Science, 2023, 44(16):1-7.). For hot-pressed rapeseed oil with an initial phosphorus content of 10.35 mg / g, the dephosphorization rate per unit of R92 was only 941.8 mg / g. ad. -1 (J. Oleo Sci.73, (1) 45-53 (2024)) reached saturation value, and it is also the modified adsorbent with the highest known adsorption capacity for phospholipids in oils.

[0005] In addition, the R92 surface contains strongly polar carboxyl groups (-COOH). The carboxyl groups of adjacent particles can reform aggregates through hydrogen bonds (-COOH…OHC-). These aggregates have irregular shapes. When used in the filtration process after phospholipid adsorption, these aggregates not only block the initial pores of the filter media, but also accumulate into a dense, mud-like filter cake on top of the filter media. This reduces the porosity of the filter bed, increases the pressure drop of the filter bed, reduces the filtration rate of oil through the filter cake layer, and increases production costs.

[0006] Akhmad used the silane coupling agent APTES to modify silica for the removal of phospholipids from waste oils. At an addition rate of 1.0% and an adsorption reaction at 80 °C for 60 min, the dephosphorization amount for waste oil with a low phosphorus content of 3.6 mg / g was only 359.496 mg / g. ad . -1 Compared to unmodified SiO2 (349.2 mg / g), ad . -1The improvement rate was only 2.9% (Chem. Eng. Sci., 2026, 320, 122565). The reasons are: 1) The modified silica is nanoscale, with thin pore walls and short channels. APTES molecules easily clog the channels under high temperatures (120 ℃) ​​and long-term (24 h) reflux, leading to a significant decrease in specific surface area (from 246 m²). 2 / g decreased to 46 m 2 / g), pore volume decreased significantly (from 0.39 cm⁻¹). 3 / g decreased to 0.17 cm 3 1) The adsorption sites are reduced; 2) Nanoscale silica has a high surface energy, and compared with micron-sized silica, it is easier for particles to agglomerate at higher modification and adsorption temperatures. When applied to adsorb and remove phospholipids from high-viscosity oils, it overcomes the difficulty of interphase diffusion mass transfer, and phospholipid molecules are restricted from entering the adsorbent pores and contacting the active centers, thus reducing the phospholipid removal rate. In addition, the agglomerated nanoscale silica during filtration also has the same problem as R92, namely, high pressure drop in the filter bed, resulting in low filtration rate and increased production costs.

[0007] In summary, existing reports lack modified silica degumming technologies for removing high concentrations of phospholipids from crude oils. There is an urgent need to develop a highly efficient adsorbent and degumming technology for oils with initial phospholipid concentrations of 15-25 mg / g. Therefore, to improve dephosphorization rates, further research is needed to develop new modified silica with high dephosphorization efficiency to meet the dephosphorization requirements of cold-pressed, hot-pressed, and leached crude oils with varying initial phospholipid contents. Summary of the Invention

[0008] In view of the above-mentioned shortcomings in the prior art, the present invention provides a modified silica for high-efficiency adsorption of phospholipids in oils and fats, and its preparation and use methods, which can effectively reduce the phospholipid content in oils and fats.

[0009] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is as follows: The purpose of this invention is to provide a method for preparing modified silica that can efficiently adsorb lipoproteins and phospholipids. Specifically, micron-sized silica is added to an aminosilane solution at 80-85 °C and reacted for 13-18 h. After the reaction is completed, the mixture is filtered and the solid product is dried to obtain amino-modified silica.

[0010] Furthermore, the average particle size of micron-sized silica is 10~50 μm.

[0011] Furthermore, the mass-to-volume ratio of micron-sized silica to aminosilane solution is 2:1~2, in g:mL.

[0012] Furthermore, the solvent used in the aminosilane solution is isopropanol.

[0013] Furthermore, the aminosilane is at least one of APTMS, APTES, and APMDES.

[0014] Furthermore, the reaction temperature was 85 °C and the reaction time was 15 h.

[0015] The advantages of the above-mentioned technical solution in this invention are as follows: Micron-sized silica, with its thick-walled porous structure formed by the high degree of cross-linking of silicon-oxygen tetrahedral networks, exhibits superior pore spatial stability. In contrast, the amino functional groups in aminosilanes are mainly grafted onto the inner walls of the pores and the outer surface of the particles. This excellent spatial stability provides a smooth diffusion path for the modifier molecules (aminosilanes), effectively avoiding pore blockage or structural collapse problems caused by amino grafting. Furthermore, as shown in Table 1, compared with ordinary micron-sized SiO2, the modified micron-sized SiO2 shows no significant changes in pore characteristics such as specific surface area and pore volume, retaining a high specific surface area and numerous open pores. This provides ample adsorption sites and efficient diffusion channels for phospholipid molecules, allowing the electrostatic interaction between amino functional groups and phospholipid molecules to function efficiently. Moreover, its micron-scale design avoids the problem of particle agglomeration obscuring adsorption sites, ensuring efficient adsorption processes.

[0016] This invention uses isopropanol as a solvent and aminosilane to modify micron-sized silica at 80-85 °C. The entire treatment condition is relatively mild, and the thick pore walls of micron-sized silica do not easily cause expansion of the silica's pore structure. Meanwhile, isopropanol has a low boiling point (82.4 °C), allowing for complete removal during subsequent drying at 90 °C, leaving no solvent residue.

[0017] Another objective of this invention is to provide a modified silica that efficiently adsorbs lipoproteins and phospholipids, which is prepared by the method described above.

[0018] Another objective of this invention is to provide a method for efficiently removing phospholipids from oils, specifically by using the modified silica described above to degumm the oils at a temperature of 35-45°C.

[0019] Furthermore, the degumming process can be either intermittent adsorption degumming or fixed-bed continuous flow degumming.

[0020] Furthermore, the intermittent adsorption degumming process is as follows: modified silica is added to the oil, adsorbed and refined at 35~45 ℃ for 25~30 min, then centrifuged at 4 ℃ and 10000 r / min for 20 min, and the supernatant is collected to obtain the treated oil.

[0021] Furthermore, in the intermittent adsorption degumming treatment, the mass-to-volume ratio of modified silica to oil is 1:80~100, in g:mL.

[0022] Furthermore, the mass-to-volume ratio of modified silica to oil is 1:100.

[0023] Furthermore, the degumming temperature is 35~45 ℃, and the degumming time is 25~30 min.

[0024] Furthermore, the fixed-bed continuous flow degumming process is as follows: at least two interconnected degumming reaction columns are prepared based on modified silica, and then the degumming temperature is controlled at 35~45 ℃. The grease is pumped into the degumming reaction columns for degumming to obtain the treated grease.

[0025] Furthermore, in the fixed-bed continuous flow degumming process, the mass-to-volume ratio of modified silica to oil is 1:20~30, in g:mL. Furthermore, when packing the modified silica into the column, it should be done in small batches, tapping the outer wall of the column as you pack to ensure the modified silica is evenly distributed and compacted within the column, preventing packing collapse during use. Two degumming reaction columns are packed with the packing material. After packing, both ends of the column packing are plugged with matching filter screens to prevent modified silica leakage. Then, a PVC hose is connected to a three-way valve, which in turn connects to a peristaltic pump and the inlet of the degumming reaction column. The peristaltic pump then pumps vegetable oil into the degumming reaction column.

[0026] Furthermore, the phospholipid concentration in the oil to be treated is 3~25 mg / g.

[0027] Furthermore, the oil to be processed is rapeseed oil, crude rapeseed oil, or compound rapeseed oil.

[0028] Furthermore, the oil to be processed is pressed rapeseed oil, crude pressed rapeseed oil, or 8:5 blended rapeseed oil, etc.

[0029] Another object of the present invention is to provide a low phospholipid content oil, which is prepared by the above method.

[0030] The beneficial effects of this invention are: This invention modifies silica with aminosilane. The -Si-OCH3 group in the aminosilane reacts with the -Si-OH group in silica, replacing the polar hydroxyl groups with alkyl-chain amino groups. Subsequently, the negatively charged phosphate group at the phospholipid head forms a strong Coulombic attraction with the protonated positively charged amino groups of the free fatty acids in crude oil, thereby improving the phospholipid removal rate. Then, based on the combination of amino-modified SiO2 and fixed-bed continuous flow / intermittent adsorption technology, a method for removing phospholipids from vegetable oils is constructed. This method can efficiently remove phospholipids from vegetable oils at relatively low temperatures (35~45 °C), exhibiting excellent removal efficiency. Its maximum adsorption capacity reaches 1861.26 mg / g, which significantly surpasses the adsorption performance of ordinary silica (1284.20 mg / g) and R92 adsorbent (1669.83 mg / g). For vegetable oil systems with phospholipid content less than 5 mg / g, modified silica can achieve complete removal of phospholipids; for vegetable oils with phospholipid content in the range of 5-10 mg / g, the residual phospholipid content in the system can be controlled below 10 mg / kg, meeting the stringent requirements of deep dephosphating processes.

[0031] The modified silica prepared in this invention incorporates amino groups containing alkyl chains, which avoids the aggregation problem caused by hydrogen bonding between hydroxyl groups in unmodified silica. This allows the modified SiO2 to maintain a relatively loose packing state during filtration, facilitating the flow of oil through the filter cake and effectively avoiding common problems in fixed-bed operations such as bed compaction, channeling, and localized clogging. This structural advantage enables the oil to flow uniformly through the adsorbent bed at a stable flow rate during continuous operation: on the one hand, it significantly reduces the flow resistance of oil within the bed, maintaining a high permeability; on the other hand, it ensures sufficient contact between the phospholipids in the crude oil and the active sites on the adsorbent surface, achieving efficient and stable adsorption and removal. Ultimately, these two aspects work synergistically to ensure the long-term stable operation of the fixed-bed continuous flow process, significantly improving the overall processing efficiency and feasibility for industrial application. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the present invention; Figure 2 Scanning electron microscope images of ordinary silica and the modified silica prepared according to the present invention; Figure 3 This is a standard curve for gallic acid. Detailed Implementation

[0033] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0034] Example 1 A method for efficiently removing phospholipids from oils includes the following steps: (1) Preparation of modified silica Weigh 2 g of SiO2 with an average particle size of 20 μm and dissolve it in 50 mL of isopropanol. Place the solution in a magnetic stirrer and reflux at 80 °C. After the temperature rises to 85 °C, add 1.5 mL of APTES solution dropwise. After the addition is complete, react at 80 °C for 18 h. After the reaction is complete, filter the solution and wash it 4 times with 20 mL of isopropanol. Place the solid material in a drying oven and dry it at 90 °C for 12 h to obtain amino-modified SiO2 (APTES-SiO2) powder.

[0035] (2) Degumming Weigh 1 g of modified SiO2 and add it to 100 mL of crude rapeseed oil. Adsorb and refine at 35 °C for 30 min, then centrifuge at 10000 r / min for 20 min at 4 °C. The resulting supernatant is the sample oil, which is then placed in a 4 °C refrigerator for 15 h for testing.

[0036] Example 2 A method for efficiently removing phospholipids from oils includes the following steps: (1) Preparation of modified silica Weigh 2 g of SiO2 with an average particle size of 10 μm and dissolve it in 50 mL of isopropanol. Place the solution in a magnetic stirrer and reflux at 85 °C. After the temperature reaches 85 °C, add 1.0 mL of APTMS solution dropwise. After the addition is complete, react at 85 °C for 15 h. After the reaction is complete, filter and wash 4 times with 20 mL of isopropanol. Place the solid material in a drying oven and dry at 90 °C for 12 h to obtain amino-modified SiO2 (APTMS-SiO2) powder.

[0037] (2) Continuous flow degumming Dry modified silica was filled into the reaction column, with each column containing 60 g of the modified silica. The filling was performed in small, multiple batches, with the outer wall of the column being tapped simultaneously during filling to ensure even distribution and compaction of the modified silica, preventing packing collapse during later use. After filling, both ends of the packing material in the reaction column were sealed with matching filter plates to prevent leakage of the modified silica during system operation. Subsequently, a PVC hose was used to connect a three-way valve, which was then used to connect to the peristaltic pump and the inlet of the degummed reaction column, completing the assembly of the entire reaction column and piping setup.

[0038] 1200 mL of vegetable oil was preheated to 40 °C in a water bath and then pumped into the degumming reaction column using a peristaltic pump. The degummed vegetable oil exited from the outlet of the first reaction column and entered the second reaction column to continue the degumming reaction. Finally, the oil was discharged from the outlet of the second reaction column. Degumming lasted for 100 minutes to obtain the processed oil. After each reaction, the three-way valve was turned to pump ultrapure water into the reaction column through the peristaltic pump to rinse the packing material, allowing the degumming reaction column to be reused.

[0039] Example 3 A method for efficiently removing phospholipids from oils includes the following steps: (1) Preparation of modified silica Weigh 2 g of SiO2 with an average particle size of 30 μm and dissolve it in 50 mL of isopropanol. Place the solution in a magnetic stirrer and reflux at 83 °C. After the temperature rises to 85 °C, add 1.5 mL of APTES solution dropwise. After the addition is complete, react at 83 °C for 13 h. After the reaction is complete, filter and wash 4 times with 20 mL of isopropanol. Place the solid material in a drying oven and dry at 90 °C for 12 h to obtain amino-modified SiO2 (APTES-SiO2) powder.

[0040] (2) Continuous flow degumming Dry modified silica was filled into the reaction column, with each column containing 60 g of the modified silica. The filling was performed in small, multiple batches, with the outer wall of the column being tapped simultaneously during filling to ensure even distribution and compaction of the modified silica, preventing packing collapse during later use. After filling, both ends of the packing material in the reaction column were sealed with matching filter plates to prevent leakage of the modified silica during system operation. Subsequently, a PVC hose was used to connect a three-way valve, which was then used to connect to the peristaltic pump and the inlet of the degummed reaction column, completing the assembly of the entire reaction column and piping setup.

[0041] 1800 mL of vegetable oil was preheated to 35 °C in a water bath and then pumped into the degumming reaction column by a peristaltic pump. The degummed vegetable oil was pumped out from the outlet of the first reaction column and entered the second reaction column to continue the degumming reaction. Finally, the oil was discharged from the outlet of the second reaction column. The degumming process lasted for 150 minutes to obtain the processed oil. After each reaction, the three-way valve was turned to pump ultrapure water into the reaction column through the peristaltic pump to rinse the packing material, allowing the degumming reaction column to be reused.

[0042] Example 4 A method for efficiently removing phospholipids from oils includes the following steps: (1) Preparation of modified silica Weigh 2 g of SiO2 with an average particle size of 50 μm and dissolve it in 50 mL of isopropanol. Place the solution in a magnetic stirrer and reflux at 85 °C. After the temperature reaches 85 °C, add 2 mL of APTES solution dropwise. After the addition is complete, react at 85 °C for 15 h. After the reaction is complete, filter and wash 4 times with 20 mL of isopropanol. Place the solid material in a drying oven and dry at 90 °C for 12 h to obtain amino-modified SiO2 (APTES-SiO2) powder.

[0043] (2) Degumming Weigh 1 g of modified SiO2 and add it to 100 mL of crude rapeseed oil. Adsorb and refine at 45 °C for 30 min, then centrifuge at 10000 r / min for 20 min at 4 °C. The resulting supernatant is the sample oil, which is then placed in a 4 °C refrigerator for 15 h for testing.

[0044] Example 5 A method for efficiently removing phospholipids from oils includes the following steps: (1) Preparation of modified silica Weigh 2 g of SiO2 with an average particle size of 28 μm and dissolve it in 50 mL of isopropanol. Place the solution in a magnetic stirrer and reflux at 80 °C. After the temperature rises to 85 °C, add 1.5 mL of APTES solution dropwise. After the addition is complete, react at 80 °C for 18 h. After the reaction is complete, filter the solution and wash it 4 times with 20 mL of isopropanol. Place the solid material in a drying oven and dry it at 90 °C for 12 h to obtain amino-modified SiO2 (APTES-SiO2) powder.

[0045] (2) Degumming Weigh 2.5 g of modified SiO2 and add it to 100 mL of crude rapeseed oil. Adsorb and refine at 45 °C for 30 min, then centrifuge at 10000 r / min for 20 min at 4 °C. The resulting supernatant is the sample oil, which is placed in a 4 °C refrigerator for 15 h for testing.

[0046] Comparative Example 1 The difference from Example 1 is that unmodified silica was used and the adsorption temperature was 45°C, while the rest of the process remained the same as in Example 1.

[0047] Comparative Example 2 The difference from Example 1 is that the amount of APTES solution used is 6 mL, while the rest of the process is the same as in Example 1.

[0048] Comparative Example 3 The difference from Example 1 is that the amount of APTES solution used is 10 mL, while the rest of the process is the same as in Example 1.

[0049] Comparative Example 4 The difference from Example 1 is that the amount of APTES solution used is 20 mL, while the rest of the process is the same as in Example 1.

[0050] Comparative Example 5 Referring to the article "Removal strategies for the undesirable components from the crude vegetable oils: A review", iminodiacetic acid (IDA)-silica described therein was used to degumm the oils at a degumming temperature of 60 °C and a degumming time of 10 h.

[0051] Comparative Example 6 Referring to the article "Removal strategies for the undesirable components from the crude vegetable oils: A review", iminodisuccinic acid (IDS)-silica described therein was used to degumm the oils at a degumming temperature of 60 °C and a degumming time of 10 h.

[0052] Comparative Example 7 Referring to the article "Mesoporous silica aerogels for sunflower oil refining and investigation of their adsorption performance", the bentonite + TSA described therein was used to degumm the sunflower seed oil. The degumming temperature was 90 ℃ and the degumming time was 30 min.

[0053] Comparative Example 8 Referring to the article "Mesoporous silica aerogels for sunflower oil refining and investigation of their adsorption performance", the bentonite + NTSA described therein was used to degumm the sunflower seed oil. The degumming temperature was 90 ℃ and the degumming time was 30 min.

[0054] Comparative Example 9 Referring to the article "Magnetic nanoparticles-immobilized phospholipase LM and phospholipase 3G: Preparation, characterization, and application on soybean crude oil degumming", the PLLM-MNPs-COOH described in the article was used to degumm the soybean oil under alkaline conditions (4% NaOH). The degumming temperature was 50 °C and the degumming time was 3 h.

[0055] Comparative Example 10 Referring to the article "Magnetic nanoparticles-immobilized phospholipase LM and phospholipase 3G: Preparation, characterization, and application on soybean crude oil degumming", soybean oil was degummed using PL3G-MNPs-COOH from the article under alkaline conditions (4% NaOH) at a degumming temperature of 50 °C for 3 h.

[0056] Comparative Example 11 The difference from Example 1 is that silica was replaced with quartz sand and 2 mL of APTES solution was used for modification, while the rest of the process remained the same as in Example 1.

[0057] Comparative Example 12 The difference from Example 1 is that kaolin was used instead of silica, and 2 mL of APTES solution was used for modification; the rest of the process was the same as in Example 1.

[0058] Comparative Example 13 The difference from Example 1 is that calcium silicate was used instead of silicon dioxide, and 2 mL of APTES solution was used for modification; the rest of the process was the same as in Example 1.

[0059] Test case 1. The morphology and surface characteristics of ordinary SiO2 and APTES-SiO2 prepared in Example 1 were analyzed using scanning electron microscopy (SEM) images. The results are shown in [Figure 1]. Figure 2 .Depend on Figure 2 It can be seen that both ordinary SiO2 and APTES-modified SiO2 (APTES-SiO2) belong to micron-sized silica materials. The ordinary SiO2 sample exhibits an irregular morphology overall. Figure 2 (a) The SiO2 sample prepared by APTES modification showed a significant reduction in surface roughness and a more uniform particle size distribution. Figure 2 (b)

[0060] 2. The pore structure characteristics of ordinary SiO2 and APTES-SiO2 materials prepared in Example 1 are shown in Table 1.

[0061] Table 1. Specific surface area, pore volume, and average pore diameter

[0062] As shown in Table 1, the average pore size of both ordinary SiO2 and APTES-modified SiO2 (APTES-SiO2) is around 18 nm. After APTES modification treatment developed in this application, the specific surface area, pore volume, and average pore size of the silica adsorbent did not change significantly, indicating that the grafting of organic functional groups did not occupy the pores.

[0063] 3. The filtration rates of the modified silica and R92 prepared in Examples 1-4 of this application were tested, with unmodified silica used as a control. The results are shown in Table 2. The specific processing procedure is as follows: Weigh 0.8 g of the above modifier and add it to 80 mL of crude rapeseed oil (phospholipid concentration of 13.746 mg / g). Adsorb at 45℃ for 30 min, and then use a vacuum filter with a filter paper pore size of 0.45 μm to perform vacuum filtration and time the process.

[0064] Table 2 Filtration rates of different adsorbents

[0065] According to the test results in Table 2, the filtration performance of the modified adsorbent prepared using the technical solution of this application is significantly better than that of R92 and unmodified silica.

[0066] 4. Rapeseed oil was treated using the methods described in Examples 1-4 and Comparative Examples 1-13, and its phospholipid removal rate was tested. The results are shown in Table 3.

[0067] Table 3 Phospholipid Removal Rate in Oils

[0068] According to the test data in Table 3, the phospholipids in the rapeseed oil treated with the technical solutions described in Examples 1-3 of this application can be completely removed. The phospholipid removal efficiency of Examples 4 and 5 is also significantly better than that of the comparative examples. This indicates that the adsorbent prepared by this invention has excellent removal efficiency for phospholipids in oils.

[0069] 5. The adsorption capacity per unit weight of the adsorbents obtained in Example 4 and Comparative Example 1 for oils (1 g) with different phospholipid contents was tested. The amount used was 1% of the oil mass, the adsorption time was 30 min, and the adsorption temperature was 45 ℃. The existing adsorbents SORBSIL® R92, S655, R92, and R40F, the article "2020. Journal of Cleaner Production. Silicon dioxide as an efficient adsorbent in the degumming of rapeseed oil (hereinafter referred to as Treatment 1)" and the article "Application of silicon dioxide in adsorption and dephosphorization of rapeseed oil and its effect on phenolic acids (hereinafter referred to as Treatment 2)" were used as controls. The increase in adsorption capacity per unit weight of each group compared to the unmodified silicon dioxide group (Comparative Example 1) was calculated. The results are shown in Tables 4 and 5.

[0070] Table 4. Unit adsorption capacity of adsorbent

[0071] Note: Residual phospholipid content refers to the amount of phospholipid remaining in each gram of oil after adsorption; unit adsorption capacity refers to the amount of phospholipid that each gram of adsorbent can adsorb.

[0072] Table 5. Increase in adsorption capacity per unit volume for different adsorbents

[0073] According to the test results in Tables 4 and 5, the modified adsorbent prepared in this invention exhibits excellent adsorption effect on oils. Compared with citric acid-modified silica (R92), the improvement rate of unit adsorption capacity is significantly higher than that of unmodified silica. In Table 5, Comparative Example 1 (ordinary silica) shows a significant difference in unit adsorption capacity for oils with initial phospholipid concentrations of 13.53 mg / g and 13.75 mg / g. This may be because the oil with an initial phospholipid concentration of 13.75 mg / g is a compound rapeseed oil, while the oil with an initial phospholipid concentration of 13.53 mg / g is an extracted rapeseed oil, resulting in a significant difference in the unit adsorption capacity for dephosphorization in Comparative Example 1. However, the modified adsorbent treated in this application did not exhibit the aforementioned problem when treating the two different types of oils, indicating that the modified adsorbent treated in this application also has excellent dephosphorization efficiency for compound rapeseed oil, and its applicability is wider.

[0074] Furthermore, compared with the existing S655 and R40F adsorbents, the citric acid-modified silica (R92) has an adsorption capacity improvement rate of only 10.3% and 12.5% ​​per unit of adsorption capacity, respectively, which is far lower than the improvement rate of this application.

[0075] 6. The changes in physicochemical properties of rapeseed oil before and after treatment as described in Example 1 and Comparative Example 1 were detected, and the results are shown in Table 6.

[0076] Table 6 Physicochemical properties of rapeseed oil before and after degumming

[0077] As shown in Table 6, after adsorption treatment by Comparative Example 1 and Example 1, the phospholipid content, peroxide value and acid value of crude rapeseed oil samples all decreased significantly, indicating that Comparative Example 1 and Example 1 can effectively adsorb impurities such as free fatty acids, peroxides and oxides in rapeseed oil, which is beneficial to oil storage and extends shelf life.

[0078] Using gallic acid as a standard, plot the equation of the standard curve ( Figure 3 The total phenol content in rapeseed oil after adsorption by ordinary SiO2 was 963.36 μg / g, while the total phenol content in rapeseed oil after adsorption by modified silica was higher, reaching 1070.28 μg / g.

[0079] Table 6 also records the color change parameters (L*, a*, b*) of rapeseed oil before and after adsorption by Comparative Example 1 and Example 1. L* represents brightness, a* value represents red-green, and b* value represents blue-yellow.

[0080] After adsorption treatment, the L* values ​​of rapeseed oil treated in Comparative Example 1 and Example 1 were higher than those of crude rapeseed oil. However, the L* value of the oil treated in Example 1 was significantly higher than that of Comparative Example 1, indicating that the oil sample treated with modified SiO2 was clearer and more transparent. Both the a* and b* values ​​were lower than those of crude rapeseed oil. The b* value of the oil sample treated with modified SiO2 was higher than that of ordinary SiO2, showing a green hue (-a*). The oil sample treated with modified SiO2 showed a yellow hue (+b*), indicating that adsorption treatment caused a color change in crude rapeseed oil. The results in Table 6 show that the rapeseed oil treated with this method exhibited an increase in L* value and a decrease in a* value, clearly demonstrating a significant improvement in quality, superior to Comparative Example 1.

[0081] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing modified silica for highly efficient adsorption of oils and phospholipids, characterized in that, Micron-sized silica was added to an aminosilane solution at 80-85 °C and reacted for 13-18 h. After the reaction was completed, the mixture was filtered and the solid product was dried to obtain amino-modified silica. The average particle size of the micron-sized silica is 10-50 μm, and its mass-to-volume ratio with the aminosilane solution is 2:1-2; the aminosilane is at least one of APTMS, APTES and APMDES.

2. A modified silica for highly efficient adsorption of oils and phospholipids, characterized in that, It is prepared by the method described in claim 1.

3. A method for efficiently removing phospholipids from oils, characterized in that, At 35~45 °C, the modified silica described in claim 2 is used to degumm the grease.

4. The method according to claim 3, characterized in that, The degumming process can be either intermittent adsorption degumming or fixed-bed continuous flow degumming.

5. The method according to claim 4, characterized in that, The intermittent adsorption degumming process is as follows: Modified silica and oil are mixed at a mass-volume ratio of 1:80~100, and the mixture is adsorbed and refined at 35~45 ℃ for 25~30 min. Then, the mixture is centrifuged and the oil is collected.

6. The method according to claim 4, characterized in that, The degumming temperature of the fixed-bed continuous flow degumming treatment is 35~45 ℃, and the mass-volume ratio of modified silica to oil is 1:20~30.

7. The method according to claim 3, characterized in that, The concentration of phospholipids in the oil to be treated is 3~25 mg / g.

8. The method according to claim 7, characterized in that, The oil to be processed is rapeseed oil.

9. The method according to claim 7, characterized in that, The oil to be processed is crude rapeseed oil.

10. The method according to claim 7, characterized in that, The oil to be processed is a blended rapeseed oil.

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