A method for preparing cottonseed-based insulating oil by using nanoporous material

Abstract

The application discloses a preparation method of cottonseed-based insulating oil by using a bifunctional nanoporous material. The method comprises the following steps: first, a multi-metal silicate nanoporous material with adsorption and seed induction functions is prepared; then, the material is added into cottonseed oil at a certain proportion; through a specific stirring, programmed cooling and crystal growing process, adsorption of polar impurities in the cottonseed oil and crystallization separation of high-condensation-point components are simultaneously completed in one step; and finally, refined insulating oil is obtained through solid-liquid separation. The application also relates to cottonseed-based insulating oil prepared by the method. The method integrates a traditional multi-step process into one step, significantly simplifies the process and shortens the production cycle, and the obtained insulating oil product has excellent comprehensive performances such as low pour point, low acid value and low dielectric loss factor.

Description

Technical Field

[0001] This invention relates to the field of natural ester insulating oils, and more particularly to a method for preparing cottonseed-based insulating oils using nanoporous materials. Background Technology

[0002] Vegetable insulating oils, especially natural ester insulating oils, are gradually becoming a good alternative to mineral insulating oils due to their advantages such as high flash point, biodegradability, and environmental friendliness. Cottonseed oil, due to its abundant resources and similar performance characteristics to existing insulating oils, is considered a promising raw material. However, using unprocessed cottonseed oil directly as an insulating oil has significant drawbacks: First, it contains a large amount of high-melting-point saturated fatty acid glycerides, resulting in a high pour point (usually around -3°C) and poor low-temperature fluidity, limiting its application in cold regions; second, cottonseed oil has a high content of naturally occurring polar impurities such as free fatty acids, gossypol, and phospholipids, leading to a high dielectric loss factor (tanδ) and unsatisfactory electrical insulation performance, making it difficult to meet the high requirements of high-voltage electrical equipment for insulating media.

[0003] Existing technologies for improving the insulation properties of cottonseed oil typically employ processes such as physical adsorption, chemical modification, or crystallization separation (wintering). For example, adsorbents like activated clay and silica gel are used to remove impurities, or the pour point is lowered through prolonged low-temperature crystallization, the addition of seed crystals, and subsequent filtration. These methods often suffer from lengthy processes, cumbersome steps, high energy consumption, low production efficiency, or difficulties in simultaneously optimizing both pour point and dielectric properties while improving one specific property. Therefore, developing a method that can efficiently and simultaneously improve the low-temperature and electrical properties of cottonseed-based insulating oil, while also being simple and easily industrialized, is of significant practical importance. Summary of the Invention

[0004] In view of this, the present invention proposes a one-step method for preparing cottonseed-based insulating oil using bifunctional nanoporous materials, aiming to solve the technical problems of complex processes and difficulty in synergistically optimizing oil performance in existing technologies.

[0005] The technical solution of this invention is implemented as follows: On one hand, the present invention provides a method for preparing cottonseed-based insulating oil, comprising the following steps: Silicon source, aluminum salt, calcium salt and magnesium salt are dissolved in ethanol solvent, a structure directing agent and a slow-release alkali source are added, and ultrasonic dispersion is performed to form a sol. After hydrothermal reaction, washing, drying and calcination, a bifunctional nanoporous material is obtained. The bifunctional nanoporous material is added to cottonseed oil and refined to obtain cottonseed-based insulating oil.

[0006] Based on the above technical solutions, preferably, the refining process includes the following steps: S1. Heat cottonseed oil to 50~120℃, add the bifunctional nanoporous material, and stir at 150~300r / min for 0.5-3h; S2. Adjust the speed to 100~200r / min, cool the cottonseed oil to 10~50℃, and continue stirring for 0.5-3h; S3. Adjust the rotation speed to 5~80r / min, cool the cottonseed oil to 0~25℃, and control the cooling rate at 1~10℃ / h; S4. Adjust the rotation speed to 1~20r / min and cool the cottonseed oil to the crystal growth temperature of -15~5℃, with the cooling rate controlled at 1~5℃ / h; continue crystal growth for 10-50h and then perform negative pressure filtration.

[0007] More preferably, in step S1, the amount of the bifunctional nanoporous material added is 0.3~5.0 wt% of the cottonseed oil mass. The bifunctional nanoporous material, on the one hand, physically traps impurities through its porous structure with a high specific surface area and adsorbs acidic substances such as free fatty acids through hydrogen bonding via surface functional groups, thereby achieving a purification function; on the other hand, as a heterogeneous nucleation site, this material can adsorb and enrich high-condensation-point components, inducing their directional alignment, effectively reducing the nucleation energy barrier, and promoting crystallization.

[0008] More preferably, in the aluminum salt, calcium salt, and magnesium salt, the molar ratio of Al:Ca is (2.5~5):1, and the molar ratio of Al:Mg is (5~15):1. The aluminum salt includes aluminum nitrate nonahydrate; the calcium salt includes calcium chloride; and the magnesium salt includes magnesium chloride hexahydrate.

[0009] More preferably, the molar ratio of Al:Ca:Mg in the aluminum salt, calcium salt, and magnesium salt is 10:4:1.

[0010] More preferably, the silicon source includes Na2SiO3 with a concentration of 0.5~2.0 mol / L; and the total concentration of the aluminum salt, calcium salt and magnesium salt is 0.3~1.2 mol / L.

[0011] More preferably, the structure-directing agent comprises hexadecyltrimethylammonium bromide at a concentration of 0.1~0.4 mol / L.

[0012] More preferably, the slow-release alkaline source includes urea with a concentration of 1-2 mol / L.

[0013] More preferably, the hydrothermal reaction conditions are: reaction at 100~160℃ for 12~18h; and the calcination conditions are: calcination at 300~500℃ for 1~3h.

[0014] Based on the above technical solutions, preferably, in step S1, after adding the bifunctional nanoporous material, a higher stirring speed is adopted to ensure that the nanomaterial is fully and quickly dispersed evenly in cottonseed oil, ensuring that its huge specific surface area can fully contact the oil, thereby effectively exerting the preliminary functions of physical adsorption of impurities and providing heterogeneous nucleation sites.

[0015] In a further preferred embodiment, in step S2, when the oil begins to cool, the rotation speed is adjusted to a medium range. This rotation speed maintains the necessary mixing state of the system, prevents uneven temperature, and avoids excessive shear damage to the newly formed micro-crystal nuclei, thus promoting the initial formation and stabilization of the nuclei.

[0016] In a further preferred embodiment, in step S3, after entering the main crystallization temperature zone, the stirring speed is significantly reduced. The purpose is to provide a relatively stable environment for crystal growth under a slow cooling rate. Lower shear force is beneficial for the already formed crystal nuclei to grow larger smoothly, rather than being broken up.

[0017] More preferably, in step S4, the crystal growth temperature is maintained at a specific low temperature range and subjected to an extremely low stirring speed during the crystallization separation (wintering) process of insulating oil preparation, for a relatively long period of time. The core purpose of using an extremely low stirring speed is to avoid shear force from destroying the formed crystals. Under these mild conditions, the high-melting-point components in the oil can fully nucleate, grow, and form structurally stable crystals, while ensuring that the adsorbed impurities are effectively encapsulated inside the crystal lattice, thus laying the foundation for achieving efficient solid-liquid separation (filtration).

[0018] On the other hand, the present invention also provides a cottonseed-based insulating oil, which is prepared by any of the above preparation methods.

[0019] Based on the above technical solutions, preferably, the cottonseed-based insulating oil uses a bifunctional nanoporous material with a particle size of 30-60 nm, a mesoporous structure, a pore size of 4-6 nm, and a specific surface area of ​​10-30 m². 2 / g, pore volume 0.5-2cm 3 / g.

[0020] More preferably, the cottonseed-based insulating oil has a pour point ≤ -25℃, an acid value ≤ 0.02 mgKOH / g, and a dielectric loss factor (90℃) ≤ 0.007.

[0021] The present invention has the following advantages over the prior art: (1) Simplified process and improved efficiency: This invention creatively uses a specially made bifunctional nanoporous material to simultaneously achieve the adsorption of polar impurities and the induction of heterogeneous nucleation of high-pour-point components during the programmed cooling crystallization (wintering) process of cottonseed oil. The two independent steps of "adsorption purification" and "crystallization fractionation" are combined into one step process, which significantly shortens the production cycle, improves production efficiency, and is more conducive to continuous industrial production.

[0022] (2) Excellent overall performance of the product: The cottonseed-based insulating oil prepared by the above one-step process has synergistically optimized low-temperature performance, electrical performance and oxidation stability. The product pour point can be reduced to -25℃ or even lower, the acid value is less than 0.02mgKOH / g, the dielectric loss factor (90℃) is not higher than 0.7%, and the breakdown voltage is high, fully meeting the standard requirements of high-performance natural ester insulating oil.

[0023] (3) High raw material utilization and controllable cost: The one-step process reduces oil loss in intermediate processing steps and improves product yield. The raw materials for preparing the nanoporous materials are readily available, the synthesis method is mature, and the overall process route has good economic efficiency and potential for large-scale application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of the bifunctional nanoporous material prepared in Example 1 of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Table 1: Material Source Description Table

[0028] Example 1: S1. Weigh 12.21 g sodium silicate, 20.00 g aluminum nitrate nonahydrate, 2.37 g calcium chloride, and 1.08 g magnesium chloride hexahydrate (molar ratio Al:Ca:Mg = 10:4:1, total aluminum, calcium, and magnesium salts 0.8 mol / L), and dissolve in 100 mL of ethanol. Disperse 7.29 g hexadecyltrimethylammonium bromide (0.2 mol / L) and 9.01 g urea (1.5 mol / L) ultrasonically for 40 min to form a transparent sol. Transfer the sol to a high-pressure reactor and react at 120 °C for 15 h. After cooling, centrifuge and wash successively with ethanol and deionized water until neutral. Freeze-dry. Spread the freeze-dried powder evenly in a ceramic crucible, place the crucible in a muffle furnace, and calcine at 350 °C for 2 h in air to remove the hexadecyltrimethylammonium bromide template, finally obtaining a nanoporous material of multi-metallic (Al:Ca:Mg) silicate. Store it in a desiccator for later use.

[0029] S2. Heat 100g of cottonseed oil to 80℃, add 2g of bifunctional nanoporous material (2 wt%), and stir at 260 r / min for 1 h. S3. Adjust the speed to 150 r / min, cool the cottonseed oil to 20 ℃, and continue stirring for 1 h; S4. Adjust the rotation speed to 10 r / min and cool the cottonseed oil to 2 ℃, with the cooling rate controlled at 2 ℃ / h; this cooling process takes about 9 hours. S5. Then adjust the rotation speed to 7 r / min and cool the cottonseed oil to the crystal growth temperature of -3 ℃, with the cooling rate controlled at 1℃ / h. This cooling process takes about 5 hours. Maintain the rotation speed at 7 r / min and the temperature at -3 ℃, and continue crystal growth for 15 hours before performing negative pressure filtration. The filtrate is the refined cottonseed-based insulating oil.

[0030] Example 2: S1. Weigh 6.10 g sodium silicate, 7.03 g aluminum nitrate nonahydrate, 0.83 g calcium chloride, and 0.76 g magnesium chloride hexahydrate (molar ratio Al:Ca:Mg = 5:2:1, total aluminum, calcium, and magnesium salts 0.3 mol / L), and dissolve in 100 mL of ethanol. Add 3.64 g hexadecyltrimethylammonium bromide (0.1 mol / L) and 6.01 g urea (1.0 mol / L), and ultrasonically disperse for 40 min to form a transparent sol. Transfer the sol to a high-pressure reactor and react at 100 °C for 12 h. After cooling, centrifuge and wash successively with ethanol and deionized water until neutral. Freeze-dry. Spread the freeze-dried powder evenly in a ceramic crucible, place the crucible in a muffle furnace, and calcine at 300 °C for 1 h in air to remove the hexadecyltrimethylammonium bromide template, finally obtaining a nanoporous material of multi-metallic (Al:Ca:Mg) silicate. Store it in a desiccator for later use.

[0031] S2. Heat 100g of cottonseed oil to 50℃, add 0.3g of bifunctional nanoporous material (0.3 wt%), and stir at 150 r / min for 0.5 h; S3. Adjust the speed to 100 r / min, cool the cottonseed oil to 10 ℃, and continue stirring for 0.5 h; S4. Adjust the rotation speed to 5 r / min and cool the cottonseed oil to 0 ℃, with the cooling rate controlled at 1 ℃ / h; S5. Adjust the rotation speed to 1 r / min and cool the cottonseed oil to the crystal growth temperature of -15 ℃, with the cooling rate controlled at 1 ℃ / h. Maintain the rotation speed at 1 r / min and the temperature at -15 ℃, and continue crystal growth for 10 h before performing negative pressure filtration. The filtrate is the refined cottonseed-based insulating oil.

[0032] Example 3: S1. Weigh 24.41 g sodium silicate, 30.68 g aluminum nitrate nonahydrate, 3.63 g calcium chloride, and 1.11 g magnesium chloride hexahydrate (molar ratio Al:Ca:Mg = 15:6:1, total aluminum, calcium, and magnesium salts 1.2 mol / L), and dissolve in 100 mL of ethanol. Add 14.58 g hexadecyltrimethylammonium bromide (0.4 mol / L) and 12.01 g urea (2.0 mol / L), and ultrasonically disperse for 40 min to form a transparent sol. Transfer the sol to a high-pressure reactor and react at 160 ℃ for 18 h. After cooling, centrifuge and wash successively with ethanol and deionized water until neutral. Freeze-dry. Spread the freeze-dried powder evenly in a ceramic crucible, place the crucible in a muffle furnace, and calcine at 500 ℃ for 3 h in air to remove the hexadecyltrimethylammonium bromide template, finally obtaining a nanoporous material of multi-metallic (Al:Ca:Mg) silicate. Store it in a desiccator for later use.

[0033] S2. Heat 100g of cottonseed oil to 120℃, add 5.0g of bifunctional nanoporous material (5.0 wt%), and stir at 300 r / min for 3 h. S3. Adjust the speed to 200 r / min, cool the cottonseed oil to 50 ℃, and continue stirring for 3 h; S4. Adjust the rotation speed to 80 r / min and cool the cottonseed oil to 25 ℃, with the cooling rate controlled at 10 ℃ / h; S5. Adjust the rotation speed to 20 r / min and cool the cottonseed oil to the crystal growth temperature of 0 ℃, with the cooling rate controlled at 5 ℃ / h; maintain the rotation speed at 20 r / min and the temperature at 5 ℃, and continue crystal growth for 50 h before performing negative pressure filtration; the filtrate is the refined cottonseed-based insulating oil.

[0034] Comparative Example 4: First, the same bifunctional nanoporous material as in Example 1 was added to cottonseed oil for adsorption. After the adsorption was completed, the material was immediately filtered out. Then, the filtered clarified oil was subjected to the same cooling, crystallization, and crystal growth process as in Example 1.

[0035] Comparative Example 5: S1. Heat 100g of cottonseed oil to 80℃, add 3g of activated clay, stir at 260 r / min for 1 h, and then filter under negative pressure to obtain clear cottonseed oil. S2. Adjust the rotation speed to 30 r / min, cool the cottonseed oil obtained in step S1 to 22 ℃, and continue stirring for 60 min; S3. Maintain the temperature difference between the cooling medium and cottonseed oil at 10 °C, and cool the cottonseed oil to 5 °C under atmospheric pressure with stirring at 5 r / min for 10 h. S4. Maintain the temperature difference between the cooling medium and cottonseed oil at 7 ℃, and cool the cottonseed oil to -3 ℃ under atmospheric pressure with stirring at 3 r / min. After stirring at constant temperature for 24 h, filter at constant temperature. Under vacuum conditions of S5, 50 r / min and -0.096 MPa, the cottonseed oil after constant temperature filtration was vacuum heated to 80℃, and 0.15 g tert-butylhydroquinone, 0.2 g 4,4-methylene (2,6-di-tert-butylphenol) and 0.8 g octylnaphthalene were added. After stirring continuously for 45 min, the cottonseed oil was vacuum cooled to room temperature.

[0036] Comparative Examples 6-7: Unlike Example 1, this example uses two different molar ratios: Al:Ca:Mg:1:1:1 (18.01g aluminum nitrate nonahydrate; 1.78g calcium chloride; 3.25g magnesium chloride hexahydrate) and Al:Ca:Mg:20:8:1 (20.69g aluminum nitrate nonahydrate; 2.45g calcium chloride; 0.56g magnesium chloride hexahydrate), with cottonseed oil weighing 100g and a total metal salt concentration of 0.8 mol / L. The remaining steps are the same as in Example 1 and will not be repeated here.

[0037] Comparative Examples 8-9: Unlike Example 1, 0.2 g of bifunctional nanoporous material (0.2 wt%) and 7 g of bifunctional nanoporous material (7 wt%) were used, respectively, with cottonseed oil weighing 100 g and a total metal salt concentration of 0.8 mol / L in both cases. The remaining steps were the same as in Example 1 and will not be repeated here.

[0038] Comparative Examples 10-11: Unlike Example 1, in step S5, crystal growth temperatures of -20 ℃ and 10 ℃ are used respectively. The remaining steps are the same as in Example 1, and will not be repeated here.

[0039] Performance testing: The cottonseed-based insulating oils prepared in Examples 1-3 and Comparative Examples 4-11 were used as samples and the following tests were performed: Breakdown voltage test (2.5mm) kV: GB / T 507; Dielectric loss factor test (tanδ) (90℃): GB / T5654; ​​Pour point test (℃): GB / T 3535; Acid value test (calculated as KOH) mg / g: GB / T 264.

[0040] Table 2. Main performance parameters of cottonseed-based insulating oils prepared in Examples 1-3

[0041] Table 3. Main performance parameters of cottonseed-based insulating oil prepared in Comparative Example 4-11

[0042] As shown in Tables 2 and 3, Examples 1-3 all exhibited lower pour points compared to Comparative Example 4. Furthermore, Example 1 was able to lower the pour point to a level comparable to Comparative Example 5 (-30 °C), but with a significantly shorter preparation time and a significantly higher yield. This demonstrates that the addition of bifunctional nanoporous materials during winterization has a significant effect on reducing the pour point of cottonseed oil and can significantly improve preparation efficiency and yield.

[0043] Examples 1-3 and Comparative Example 4 all used bifunctional nanoporous materials as adsorbents, and compared with Comparative Example 5, the acid value and media loss factor were all lower. This proves that compared with ordinary adsorbent activated clay, bifunctional nanoporous materials, due to their porous structure and nanoscale effect, have a high specific surface area and multiple active sites, and can better adsorb and remove acidic / polar impurities such as gossypol, phospholipids, and free fatty acids from cottonseed oil.

[0044] Comparing Comparative Examples 6-7 with Example 1, it can be seen that the molar ratios of Al:Ca and Al:Mg decreased during the preparation of the bifunctional nanoporous material in Comparative Example 6; while the molar ratios of Al:Ca and Al:Mg increased during the preparation of the bifunctional nanoporous material in Comparative Example 7. The test results showed higher pour point, acid value, and dielectric loss compared to Example 1. This demonstrates that when the molar ratio decreases (relative Al deficiency), the metal active sites (such as Ca) in the material... 2+ Mg 2+ The density decreases, the ability to adsorb free fatty acids weakens (acid value increases), and Al 3+ Insufficient stabilizing effect on the silicate framework leads to a decrease in the dispersion of polymetallic sites (Mg-Zn-Ca) and a reduction in seeding efficiency (increased pour point); when the molar ratio increases (Al is relatively excessive), Al... 3+ It can easily lead to localized collapse of the skeleton, destruction of the mesoporous structure, and excessive Al 3+ With Ca 2+ Mg 2+ Competitive coordination weakens the synergistic nucleation ability of ternary metals, ultimately leading to residual impurities (simultaneous increase in acid value and dielectric loss). Only within a suitable molar ratio range can the skeletal support of Al, the nucleation induction of Ca / Mg, and the adsorption and capture functions be balanced, achieving synergistic optimization of "adsorption-crystallization" and ensuring that cottonseed oil meets the standards for low-temperature fluidity (pour point), electrical insulation (dielectric loss), and stability (acid value).

[0045] Comparing Comparative Examples 8-9 with Example 1, it can be seen that in Comparative Example 8, the amount of bifunctional catalyst added was reduced, and the test results showed an increase in pour point, acid value, and dielectric loss compared to Example 1. This proves that when the amount of bifunctional catalyst added is too low, the number of heterogeneous nucleation centers decreases (pour point rises) and the impurity removal efficiency decreases (dielectric loss and acid value increase). In Comparative Example 9, the amount of bifunctional catalyst added was increased, and the test results showed a decrease in acid value and dielectric loss compared to Example 1, but the yield decreased significantly. This proves that although an increase in adsorption sites can adsorb more impurities and improve the purity of the oil (dielectric loss and acid value decrease), it can also lead to too many nucleation sites during winterization, resulting in larger crystal growth and a decrease in the final yield of liquid grease.

[0046] Comparing Comparative Examples 10-11 with Example 1, it can be seen that the crystallization temperature of Comparative Example 10 decreased, and the test results showed a lower pour point compared to Example 1, but the yield decreased significantly. This proves that the crystallization temperature was too low. Although it allowed more high-pour-point lipids to crystallize and obtain a lower pour point, too much liquid lipid crystallized and was filtered, resulting in a low liquid lipid yield. The crystallization temperature of Comparative Example 11 increased, and the pour point was not improved compared to the initial cottonseed oil (-3 ℃), with almost no loss (yield 98%). This proves that the crystallization temperature was too high, and crystal nuclei could not be formed, resulting in no solid lipids being produced.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cottonseed-based insulating oil, characterized in that, Includes the following steps: Silicon source, aluminum salt, calcium salt and magnesium salt are dissolved in ethanol solvent, a structure directing agent and a slow-release alkali source are added, and ultrasonic dispersion is performed to form a sol. After hydrothermal reaction, washing, drying and calcination, a bifunctional nanoporous material is obtained. The bifunctional nanoporous material is added to cottonseed oil and refined to obtain cottonseed-based insulating oil.

2. The preparation method according to claim 1, characterized in that, The refining process includes the following steps: S1. Heat cottonseed oil to 50~120℃, add the bifunctional nanoporous material, and stir at 150~300r / min for 0.5-3h; S2. Adjust the speed to 100~200r / min, cool the cottonseed oil to 10~50℃, and continue stirring for 0.5-3h; S3. Adjust the rotation speed to 5~80r / min, cool the cottonseed oil to 0~25℃, and control the cooling rate at 1~10℃ / h; S4. Adjust the rotation speed to 1~20r / min and cool the cottonseed oil to the crystal growth temperature of -15~5℃, with the cooling rate controlled at 1~5℃ / h; continue crystal growth for 10-50h and then perform negative pressure filtration.

3. The preparation method according to claim 2, characterized in that, In step S1, the amount of the bifunctional nanoporous material added is 0.3~5.0 wt% of the cottonseed oil mass.

4. The preparation method according to claim 1, characterized in that, In the aluminum, calcium, and magnesium salts, the molar ratio of Al:Ca is (2.5~5):1, and the molar ratio of Al:Mg is (5~15):

1.

5. The preparation method according to claim 1, characterized in that, The silicon source includes Na2SiO3 with a concentration of 0.5~2.0 mol / L; the total concentration of the aluminum salt, calcium salt and magnesium salt is 0.3~1.2 mol / L.

6. The preparation method according to claim 1, characterized in that, The structure-directing agent comprises hexadecyltrimethylammonium bromide at a concentration of 0.1~0.4 mol / L.

7. The preparation method according to claim 1, characterized in that, The slow-release alkaline source includes urea at a concentration of 1-2 mol / L.

8. The preparation method according to claim 1, characterized in that, The hydrothermal reaction conditions are: reaction at 100~160℃ for 12~18h; the calcination conditions are: calcination at 300~500℃ for 1~3h.

9. A cottonseed-based insulating oil, characterized in that, It is prepared by any one of the preparation methods of claims 1-8.

10. The cottonseed-based insulating oil as described in claim 9, characterized in that, The bifunctional nanoporous material used has a mesoporous structure with a pore size of 4-6 nm.

Images