Preparation method of high-temperature transformer oil

Abstract

The invention discloses a preparation method of high-temperature transformer oil, and belongs to the technical field of high-temperature transformer oil. Comprising the following steps: 1, carrying out hydrolysis reaction to obtain ricinoleic acid; step 2, carrying out first esterification reaction to obtain a ricinoleic acid esterification product; 3, performing epoxidation reaction to obtain an epoxidized ricinoleic acid esterification product; 4, carrying out ring-opening reaction to obtain ring-opened castor oil; 5, carrying out a second esterification reaction to obtain modified castor oil base oil; and 6, mixing the modified castor oil base oil, a viscosity index improver, an antioxidant, a demulsifying agent and an extreme pressure agent to obtain the high-temperature transformer oil. The invention provides modified castor oil and a preparation method thereof. The high-temperature antioxidant transformer oil prepared by using the modified castor oil as base oil has the characteristics of environmental protection, degradability, high flash point, high breakdown voltage and the like, and also has excellent oxidation stability.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature transformer oil technology, specifically, it relates to a method for preparing high-temperature transformer oil. Background Technology

[0002] Transformer oil, as a key functional material in power equipment, must simultaneously meet multiple performance requirements, including insulation, heat dissipation, and arc suppression. Currently, the widely used transformer oils are still mainly naphthenic or paraffinic mineral oils. While these have advantages such as low cost and mature technology, their non-renewability, poor biodegradability, and potential environmental risks in the event of leakage have become key bottlenecks restricting the sustainable development of the industry. With increasingly stringent global environmental regulations, the International Electrotechnical Commission (IEC) and relevant national standards (such as IEC 62770 and GB 2536-2011) have clearly proposed requirements for the development of bio-based insulating oils, driving vegetable oil-based transformer oils to become a key research direction.

[0003] Mineral insulating oils have been widely used in oil-immersed power transformers for the past century. However, their low flash point poses a risk of combustion and explosion, and their poor biodegradability can cause long-term environmental pollution after leakage, which is incompatible with my country's "green and low-carbon" development strategy and "dual-carbon" goals. Against this backdrop, ester-based insulating oils—including natural and synthetic esters—which combine excellent environmental protection characteristics with superior technical performance, are considered ideal alternatives and are gradually becoming the development trend in the transformer oil field.

[0004] Vegetable oils such as soybean oil, castor oil, and rapeseed oil are considered potential alternatives to mineral oils due to their renewable sources, high viscosity index, and good lubricity. Castor oil, for example, is rich in hydroxyl groups and double bonds in its molecular structure (ricinoleic acid content exceeds 85%), possessing the potential to further enhance its thermal stability and antioxidant properties through chemical modification. However, using vegetable oils directly as transformer oil still faces three key challenges: First, insufficient oxidative stability: polyunsaturated fatty acids are easily oxidized, leading to increased acid value and deterioration of insulation performance; second, limited low-temperature performance: for example, castor oil's freezing point is approximately -18℃, making it difficult to meet the operating requirements of extremely cold regions; and third, insufficient extreme pressure anti-wear properties: structural modification or additives are needed to enhance its load-bearing capacity.

[0005] Therefore, in order to solve the above problems, the present invention provides a method for preparing high-temperature transformer oil. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing high-temperature transformer oil.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing high-temperature transformer oil includes the following steps: Step 1: Hydrolysis reaction: Mix castor oil with an acidic catalyst and stir at 50-150℃ for 1-10 hours. After the reaction is completed, wash the reaction solution until neutral and remove the solvent to obtain ricinoleic acid. Step 2: First esterification reaction: Castor oil acid, long-chain fatty alcohol and catalyst are mixed and reacted at 80-160℃ for 6-12h. After the reaction is completed, the product is washed until neutral and the solvent is removed to obtain the esterified castor oil product. Step 3: Epoxidation reaction: The esterified castor oil product, oxidant and catalyst are mixed and reacted at 50-100℃ for 5-15h. After the reaction is completed, the product is washed and the solvent is removed to obtain the epoxidized castor oil esterified product. Step 4: Ring-opening reaction: The epoxidized castor oil esterification product, long-chain fatty acids and catalyst are mixed and stirred at 100-150℃ for 8-16 hours. After the reaction is completed, the mixture is extracted, washed and the solvent is removed to obtain ring-opened castor oil. Step 5: Second esterification reaction: Mix open-ring castor oil, long-chain fatty acids and catalyst, and stir at 100-150℃ for 8-16 hours. After the reaction is completed, wash the product until neutral and remove the solvent to obtain modified castor oil base oil. Step 6: Mix modified castor oil base oil, viscosity index improver, antioxidant, demulsifier, and extreme pressure agent to obtain high-temperature transformer oil.

[0008] The specific preparation process of the hydrolysis reaction in the scheme is as follows: The specific preparation process for the first esterification reaction in the scheme is as follows: The specific preparation process of the epoxidation reaction in the scheme is as follows: The specific preparation process of the ring-opening reaction in the scheme is as follows: The specific preparation process for the second esterification reaction in the scheme is as follows: Ideally, the catalysts described in steps 2, 3, 4, and 5 are independently selected from one of Lewis acid catalysts, organic acid catalysts, or basic catalysts.

[0009] More preferably, the Lewis acid catalyst is aluminum chloride, zinc chloride, boron trifluoride, or an acidic ion exchange resin; the organic acid catalyst is formic acid, acetic acid, phosphoric acid, or p-toluenesulfonic acid; and the basic catalyst is sodium hydroxide, potassium hydroxide, triethylamine, cyclohexylamine, tetrabutylammonium bromide, pyridine, or 4-dimethylaminopyridine.

[0010] Ideally, the amount of catalyst used in steps 2, 3, 4, and 5 is 0.01-1% of the total mass of the reactants in each step.

[0011] Ideally, the oxidant in step 3 is one of hydrogen peroxide, m-chloroperoxybenzoic acid, or persulfate.

[0012] In a more optimized manner, the mass ratio of the epoxidized castor oil esterification product to the long-chain fatty acid in step 4 is 1:1 to 1:5; and the mass ratio of the open-ring castor oil to the long-chain fatty acid in step 5 is 1:1 to 1:5.

[0013] More preferably, the long-chain fatty alcohol in step 2 is a saturated monohydric alcohol with 5 to 18 carbon atoms and its isomers; the long-chain fatty acid in steps 4 and 5 is a saturated monocarboxylic acid with 8 to 16 carbon atoms and its isomers.

[0014] Further optimized, the long-chain fatty alcohol in step 2 is dodecyl alcohol or isooctyl alcohol; the long-chain fatty acids in steps 4 and 5 are independently selected from dodecanoic acid or octadecanoic acid.

[0015] In a more optimized manner, the high-temperature transformer oil comprises the following components: by mass percentage, 85-90% modified castor oil base oil, 1-10% viscosity index improver, 2-5% antioxidant, 0.05-0.2% demulsifier, and 0.1-5% extreme pressure agent.

[0016] More preferably, the viscosity index improver is selected from one or more of polymethacrylate, ethylene-propylene copolymer, and polyisobutylene; The antioxidant is selected from hindered phenolic antioxidants or ammonia antioxidants; The deemulsifier is selected from cationic emulsifiers or anionic emulsifiers; The extreme pressure agent is selected from one of sulfurized cottonseed oil, sulfurized lard, and ammonium thiophosphate.

[0017] The beneficial effects of this invention are: This invention proposes a modified castor oil and its preparation method. High-temperature antioxidant transformer oil formulated using this modified castor oil as a base oil is characterized by its environmental friendliness, biodegradability, high flash point (greater than 330℃), and high breakdown voltage (up to 75kV). It also exhibits excellent oxidation stability, meeting current market demands and demonstrating promising application prospects.

[0018] The proposed method employs a multi-step chemical modification strategy to achieve controllable functionalization of the castor oil molecular structure. During the hydrolysis and esterification stages, the triglyceride structure in castor oil is hydrolyzed and broken, releasing ricinoleic acid (primarily 12-hydroxyoctadec-9-enoic acid), rich in hydroxyl groups and double bonds. These active sites provide the reaction basis for subsequent modifications. Subsequently, a long-chain fatty alcohol is introduced during the esterification reaction, replacing the original glycerol backbone to form a linear fatty acid ester structure. This process not only reduces molecular polarity and improves hydrophobicity and low-temperature fluidity but also retains the hydroxyl functional groups, laying the foundation for subsequent functionalization modifications.

[0019] During the epoxidation and ring-opening stages, the double bonds in the ricinoleate molecule are converted into highly reactive epoxy groups via epoxidation, enhancing intermolecular forces and compatibility with polar substrates. Subsequently, under acid-catalyzed conditions, a ring-opening reaction occurs, converting the epoxy groups into secondary hydroxyl groups and introducing a long-chain fatty acid ester structure. This further regulates the molecular polarity distribution and enhances steric hindrance, thereby significantly improving the product's thermal stability and hydrolysis resistance.

[0020] In the final esterification modification step, the secondary hydroxyl groups in the ring-opening product undergo further esterification with long-chain fatty acids, forming new ester bonds and further increasing the polarity of the modified castor oil. Due to the strong interaction between the ester groups and the metal surface, the resulting polyester-modified castor oil exhibits significantly better lubricity, adhesion, and friction-improving properties than unmodified castor oil and traditional mineral oil. Furthermore, by controlling the molecular chain length and branching degree, the intermolecular regularity can be effectively altered, thereby controlling key properties such as viscosity, viscosity index, pour point, and flash point of the product. For example, longer branches can weaken intermolecular forces and promote chain slip, thus giving the product better low-temperature fluidity and a lower pour point.

[0021] In summary, this study achieved synergistic optimization of viscosity, polarity, thermal stability, low-temperature performance, and compatibility at the molecular level by precisely constructing "hydrophilic-hydrophobic" micro-region structures and systematically controlling the length and distribution of branch chains. Detailed Implementation

[0022] 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 some embodiments of the present invention, and not all 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.

[0023] Example 1: A method for preparing high-temperature transformer oil, comprising the following steps: Step 1: Mix 1000g castor oil with 1g concentrated sulfuric acid (as a catalyst, accounting for 0.1% of the total mass of the reactants), place the mixture in a three-necked flask equipped with a condenser, and stir the mixture at 75°C for 3 hours. After the reaction is complete, wash the reaction solution until it is neutral, and then perform vacuum distillation to remove the solvent to obtain ricinoleic acid. Step 2: Take 100g of ricinoleic acid, 150g of dodecanol and 2.5g of acidic ion exchange resin (catalyst, accounting for 1% of the total mass of reactants) and mix them. Add the mixture to a three-necked flask equipped with a water separator and heat it at 80℃ for 8 hours. After the reaction is completed, wash the product until it is neutral and remove the solvent to obtain the esterified product of ricinoleic acid. Step 3: Mix 100g of castor oil esterification product, 50g of hydrogen peroxide (as oxidant) and 50g of acetic acid (as catalyst and solvent), place them in a three-necked flask with a condenser, and react at 50°C for 5 hours. After the reaction is complete, wash the product until it is neutral and remove the solvent by rotary evaporation to obtain the epoxidized castor oil esterification product. Step 4: Mix 100g of epoxidized castor oil esterification product with 50g of stearic acid, add 0.15g of concentrated sulfuric acid (catalyst, accounting for 0.1% of the total mass of reactants), place in a three-necked flask equipped with a thermometer, and stir at 100℃ for 8h. After the reaction is completed, extract the product and wash until neutral to obtain open-ring castor oil. Step 5: Mix 100g of ring-opening castor oil with 50g of dodecanoic acid, add 2.5g of acidic ion exchange resin (catalyst, accounting for 1.67% of the total mass of reactants), and heat the mixture in a three-necked flask equipped with a water separator at 100℃ for 12h. After the reaction is completed, wash the product until it is neutral and remove the solvent to obtain modified castor oil base oil. Step 6: Mix modified castor oil base oil, viscosity index improver (ethylene-propylene copolymer), antioxidant (2,6-di-tert-butyl-p-cresol), demulsifier (nonylphenol polyoxyethylene ether), and extreme pressure agent (sulfurized cottonseed oil) to obtain high-temperature transformer oil (by mass percentage: 90% modified castor oil base oil, 5% ethylene-propylene copolymer, 2.5% 2,6-di-tert-butyl-p-cresol, 0.2% nonylphenol polyoxyethylene ether, and 0.3% sulfurized cottonseed oil).

[0024] Example 2: A method for preparing high-temperature transformer oil, comprising the following steps: Step 1: Mix 1000g castor oil with 1g concentrated sulfuric acid (as a catalyst, accounting for 0.1% of the total mass of the reactants), place the mixture in a three-necked flask equipped with a condenser, and stir the mixture at 75°C for 3 hours. After the reaction is complete, wash the reaction solution until it is neutral, and then perform vacuum distillation to remove the solvent to obtain ricinoleic acid. Step 2: Take 100g of ricinoleic acid, 150g of isooctyl alcohol and 2.5g of acidic ion exchange resin (catalyst, accounting for 1% of the total mass of reactants) and mix them. Add the mixture to a three-necked flask equipped with a water separator and heat it at 80℃ for 8 hours. After the reaction is completed, wash the product until it is neutral and remove the solvent to obtain the esterified product of ricinoleic acid. Step 3: Mix 100g of castor oil esterification product, 50g of hydrogen peroxide (as oxidant) and 50g of acetic acid (as catalyst and solvent), place them in a three-necked flask with a condenser, and react at 50°C for 5 hours. After the reaction is complete, wash the product until it is neutral and remove the solvent by rotary evaporation to obtain the epoxidized castor oil esterification product. Step 4: Mix 100g of epoxidized castor oil esterification product with 50g of dodecanoic acid, add 0.15g of concentrated sulfuric acid (catalyst, accounting for 0.1% of the total mass of reactants), place in a three-necked flask equipped with a thermometer, and stir at 100℃ for 8h. After the reaction is completed, extract the product and wash until neutral to obtain open-ring castor oil. Step 5: Mix 100g of ring-opening castor oil with 50g of stearic acid, add 2.5g of acidic ion exchange resin (catalyst, accounting for 1.67% of the total mass of reactants), and heat the mixture in a three-necked flask equipped with a water separator at 100℃ for 12h. After the reaction is completed, wash the product until it is neutral and remove the solvent to obtain modified castor oil base oil. Step 6: Mix modified castor oil base oil, viscosity index improver (polyisobutylene), antioxidant (4,4-methylenebis(2,6-di-tert-butylphenol) and N-phenyl-α-aniline), demulsifier (nonylphenol polyoxyethylene ether), and extreme pressure agent (ammonium thiophosphate) to obtain high-temperature transformer oil (by mass percentage: 85% modified castor oil base oil, 5% polyisobutylene, 2.5% 4,4-methylenebis(2,6-di-tert-butylphenol), 2% N-phenyl-α-aniline, 0.2% nonylphenol polyoxyethylene ether, and 0.3% ammonium thiophosphate).

[0025] Testing and experimentation: The high-temperature transformer oil obtained in the example was subjected to the following tests, and the data obtained are shown in the table below: Conclusion: This invention successfully prepared a high-temperature transformer oil based on modified castor oil through multi-step chemical modification. The product exhibits excellent performance in several key indicators. Experimental data show that its auto-ignition point is above 550℃ and its resistivity exceeds 5.6 × 10⁻⁶. 10With a high Ω•cm, acid value below 0.015 mg KOH / g, breakdown voltage of 81.5-82 kV, flash point above 330℃, pour point as low as -50℃, and viscosity index as high as 168-169, this transformer oil exhibits excellent thermal stability, electrical insulation, oxidation stability, and low-temperature fluidity. Furthermore, its rotating oxygen bomb oxidation induction time exceeds 110 minutes, further confirming its good oxidation resistance. This transformer oil, made from renewable castor oil, possesses advantages such as being environmentally friendly, biodegradable, having a high flash point, and high breakdown voltage. It can meet the operational requirements of power equipment under high temperature, high load, and harsh environments, demonstrating promising application prospects and market potential.

[0026] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing high-temperature transformer oil, characterized in that, Includes the following steps: Step 1: Mix castor oil with an acidic catalyst and stir at 50-150℃ for 1-10 hours. After the reaction is complete, wash the reaction solution until neutral and remove the solvent to obtain ricinoleic acid. Step 2: Mix ricinoleic acid, long-chain fatty alcohol and catalyst, and react at 80-160℃ for 6-12h. After the reaction is completed, wash the product until neutral and remove the solvent to obtain the esterified product of ricinoleic acid. Step 3: Mix the castor oil esterification product, oxidant, and catalyst, and react at 50-100℃ for 5-15 hours. After the reaction is completed, wash and remove the solvent to obtain the epoxidized castor oil esterification product. Step 4: Mix the epoxidized castor oil esterification product, long-chain fatty acids, and catalyst, and stir the mixture at 100-150℃ for 8-16 hours. After the reaction is completed, extract and wash the mixture to remove the solvent and obtain open-ring castor oil. Step 5: Mix open-ring castor oil, long-chain fatty acids and catalyst, and stir at 100-150℃ for 8-16 hours. After the reaction is completed, wash the product until neutral and remove the solvent to obtain modified castor oil base oil. Step 6: Mix modified castor oil base oil, viscosity index improver, antioxidant, demulsifier, and extreme pressure agent to obtain high-temperature transformer oil.

2. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, The catalysts described in steps 2, 3, 4, and 5 are independently selected from one of Lewis acid catalysts, organic acid catalysts, or basic catalysts.

3. The method for preparing high-temperature transformer oil according to claim 2, characterized in that, The Lewis acid catalyst is aluminum chloride, zinc chloride, boron trifluoride, or an acidic ion exchange resin; the organic acid catalyst is formic acid, acetic acid, phosphoric acid, or p-toluenesulfonic acid; the basic catalyst is sodium hydroxide, potassium hydroxide, triethylamine, cyclohexylamine, tetrabutylammonium bromide, pyridine, or 4-dimethylaminopyridine.

4. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, The amount of catalyst used in steps 2, 3, 4, and 5 is 0.01-1% of the total mass of the reactants in each step.

5. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, The oxidant mentioned in step 3 is one of hydrogen peroxide, m-chloroperoxybenzoic acid, and persulfate.

6. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, In step 4, the mass ratio of the epoxidized castor oil esterification product to the long-chain fatty acid is 1:1 to 1:5; in step 5, the mass ratio of the open-ring castor oil to the long-chain fatty acid is 1:1 to 1:

5.

7. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, The long-chain fatty alcohols mentioned in step 2 are saturated monohydric alcohols with 5 to 18 carbon atoms and their isomers; the long-chain fatty acids mentioned in steps 4 and 5 are saturated monocarboxylic acids with 8 to 16 carbon atoms and their isomers.

8. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, The high-temperature transformer oil comprises the following components by mass percentage: 85-90% modified castor oil base oil, 1-10% viscosity index improver, 2-5% antioxidant, 0.05-0.2% demulsifier, and 0.1-5% extreme pressure agent.

9. The method for preparing high-temperature transformer oil according to claim 1, characterized in that, The viscosity index improver is selected from one or more of polymethyl methacrylate, ethylene-propylene copolymer, and polyisobutylene; The antioxidant is selected from hindered phenolic antioxidants or ammonia antioxidants; The deemulsifier is selected from cationic emulsifiers or anionic emulsifiers; The extreme pressure agent is selected from one of sulfurized cottonseed oil, sulfurized lard, and ammonium thiophosphate.

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