High-performance transformer oil based on imidazolium ionic liquid and preparation method thereof

Abstract

The invention belongs to the technical field of electrical insulating materials, and provides high-performance transformer oil based on imidazolium ionic liquid and a preparation method of the high-performance transformer oil. The high-performance transformer oil based on the imidazolium ionic liquid is prepared from the following components in parts by mass: 20 to 28 parts of basic transformer oil, 20 to 28 parts of ionic liquid, 2 to 18 parts of antioxidant, 2 to 20 parts of pour point depressant and 2 to 20 parts of metal organic framework compound, the ionic liquid comprises imidazole tetrafluoroborate ionic liquid and / or imidazole hexafluorophosphate ionic liquid. The ionic liquid, the antioxidant, the pour point depressant and the metal organic framework compound are introduced into the basic transformer oil, so that the breakdown voltage, the heat-conducting property and the flame retardant property of the transformer oil are remarkably improved on the premise of not changing the basic physical and chemical properties of an oil product, and meanwhile, good oxidation stability and low gassing property of the transformer oil are kept; the device is suitable for high-performance and high-voltage power transmission and transformation equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical insulation materials, and particularly relates to a high-performance transformer oil based on imidazole ionic liquid and a preparation method thereof. BACKGROUND

[0002] As a kind of liquid dielectric, transformer oil plays a key role in power transformers in terms of insulation, heat dissipation and arc extinguishing. With the continuous improvement of power grid voltage level and the development of equipment towards miniaturization and high efficiency, higher requirements are put forward for the comprehensive performance of transformer oil, especially its dielectric strength, thermal conductivity and operational safety.

[0003] However, the mineral transformer oil widely used at present has the following inherent defects: ① limited thermal stability and thermal conductivity: prone to aging under overload or hot spot temperature, and low thermal conductivity, which restricts the heat dissipation efficiency of the transformer; ② flammability risk: relatively low flash point, which poses a fire safety hazard; ③ bottleneck in performance improvement: the space for further improving the performance of the oil by means of traditional refining process and additive technology has reached the limit.

[0004] Therefore, it is urgent to provide a modified transformer oil with excellent thermal stability and thermal conductivity and high safety performance and a preparation method thereof. SUMMARY

[0005] Therefore, the present application provides a high-performance transformer oil based on imidazole ionic liquid and a preparation method thereof, so as to solve the problems of poor thermal stability and thermal conductivity, low flash point and flammability of the existing transformer oil, and improve the compatibility of ionic liquid and transformer oil.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: The present application provides a high-performance transformer oil based on imidazole ionic liquid, which comprises the following components by mass fraction: 20-28 parts of base transformer oil, 20-28 parts of ionic liquid, 2-18 parts of antioxidant, 2-20 parts of pour point depressant and 2-20 parts of metal organic framework compound.

[0007] Preferably, the ionic liquid comprises imidazole tetrafluoroborate ionic liquid and / or imidazole hexafluorophosphate ionic liquid.

[0008] Preferably, the base transformer oil comprises one or more of API Class II hydrogenated mineral oil, API Class III hydrogenated mineral oil and alkyl naphthalene synthetic oil.

[0009] Preferably, the imidazolium tetrafluoroborate ionic liquid comprises one or more of 1-decyl-3-methylimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, 1-tetradecyl-3-methylimidazolium tetrafluoroborate and 1-hexadecyl-3-methylimidazolium tetrafluoroborate.

[0010] Preferably, the imidazolium hexafluorophosphate ionic liquid comprises one or more of 1-decyl-3-methylimidazolium hexafluorophosphate, 1-dodecyl-3-methylimidazolium hexafluorophosphate, 1-tetradecyl-3-methylimidazolium hexafluorophosphate and 1-hexadecyl-3-methylimidazolium hexafluorophosphate.

[0011] Preferably, the antioxidant comprises one or more of 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol and tetra- [beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester.

[0012] Preferably, the pour point depressant comprises polymethacrylate and / or ethylene-propylene copolymer.

[0013] Preferably, the metal-organic framework compound comprises one or more of MIL-101, MIL-100, UiO-66 and ZIF-8.

[0014] The present application also provides a preparation method of the above-mentioned high-performance transformer oil based on imidazolium ionic liquid, comprising the following steps: 1) mixing the ionic liquid with aromatic hydrocarbon compounds to obtain a mother liquor; 2) mixing the mother liquor, antioxidant, pour point depressant, metal-organic framework compound and base transformer oil, and performing vacuum treatment to obtain the high-performance transformer oil based on imidazolium ionic liquid.

[0015] Preferably, the mass concentration of the mother liquor in step 1) is 1-5 wt%; and the aromatic hydrocarbon compounds comprise alkylbenzene and / or methylnaphthalene.

[0016] Preferably, the temperature of the vacuum treatment in step 2) is 60-100℃, the vacuum degree is ≤-0.095 MPa, and the time is 4-8 h.

[0017] According to the above technical solution, compared with the prior art, the present application has the following beneficial effects: The application introduces an ionic liquid, an antioxidant, a pour point depressant and a metal organic framework compound into the base transformer oil, wherein the anion and cation pair in the ionic liquid can form a relaxation polarization under the action of an electric field, which helps to improve the dielectric strength and inhibit static charging; in addition, the ionic liquid has high heat capacity and heat conductivity, which helps to improve the overall heat dissipation to improve the conduction and stability of the transformer oil; the addition of the antioxidant helps to improve the chemical stability and service life of the transformer oil; the addition of the pour point depressant helps to reduce the pour point of the transformer oil and improve the low-temperature fluidity; the metal organic framework compound has a super-high specific surface area and a regular pore structure which can be designed, and can effectively adsorb aging products, improve the purification and retention capacity of the transformer oil and enhance the stability.

[0018] The addition of the above additives can significantly improve the breakdown voltage, heat conduction performance and flame retardant performance of the transformer oil without changing the basic physical and chemical properties of the oil, while maintaining the good oxidation stability and low gas separation of the transformer oil, and is suitable for high-performance, high-voltage grade power transmission and transformation equipment. DETAILED DESCRIPTION

[0019] The application provides a high-performance transformer oil based on an imidazole ionic liquid, which comprises the following components in mass fraction: The base transformer oil is 20-28 parts, the ionic liquid is 20-28 parts, the antioxidant is 2-18 parts, the pour point depressant is 2-20 parts and the metal organic framework compound is 2-20 parts.

[0020] In the application, the base transformer oil is preferably 22-27 parts, and further preferably 23-25 parts; the ionic liquid is preferably 22-27 parts, and further preferably 23-25 parts; the antioxidant is preferably 3-15 parts, and further preferably 5-10 parts; the pour point depressant is preferably 5-18 parts, and further preferably 8-15 parts; and the metal organic framework compound is preferably 5-18 parts, and further preferably 8-15 parts.

[0021] In the application, the ionic liquid preferably comprises an imidazole tetrafluoroborate ionic liquid and / or an imidazole hexafluorophosphate ionic liquid.

[0022] In the application, the base transformer oil preferably comprises one or more of API Class II hydrogenated mineral oil, API Class III hydrogenated mineral oil and alkyl naphthalene synthetic oil.

[0023] In the application, the imidazole tetrafluoroborate ionic liquid preferably comprises one or more of 1-decyl-3-methyl imidazole tetrafluoroborate, 1-dodecyl-3-methyl imidazole tetrafluoroborate, 1-tetradecyl-3-methyl imidazole tetrafluoroborate and 1-hexadecyl-3-methyl imidazole tetrafluoroborate.

[0024] In the present application, the imidazole-based hexafluorophosphate ionic liquid preferably comprises one or more of 1-decyl-3-methylimidazolium hexafluorophosphate, 1-dodecyl-3-methylimidazolium hexafluorophosphate, 1-tetradecyl-3-methylimidazolium hexafluorophosphate and 1-hexadecyl-3-methylimidazolium hexafluorophosphate.

[0025] In the present application, the antioxidant preferably comprises one or more of 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol and tetra-β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid pentaerythritol ester.

[0026] In the present application, the pour point depressant preferably comprises polymethyl acrylate and / or ethylene-propylene copolymer.

[0027] In the present application, the metal organic framework compound preferably comprises one or more of MIL-101, MIL-100, UiO-66 and ZIF-8.

[0028] The present application also provides a preparation method of the above-mentioned high-performance transformer oil based on imidazole-based ionic liquid, comprising the following steps: 1) mixing the ionic liquid with the aromatic hydrocarbon compound to obtain a mother liquor; 2) mixing the mother liquor, the antioxidant, the pour point depressant, the metal organic framework compound and the base transformer oil, and performing vacuum treatment to obtain the high-performance transformer oil based on imidazole-based ionic liquid.

[0029] In the present application, the mass concentration of the mother liquor in step 1) is 1-5 wt%, preferably 1.5-4.5 wt%, further preferably 2-4 wt%, and more preferably 3 wt%; the aromatic hydrocarbon compound comprises alkylbenzene and / or methylnaphthalene.

[0030] In the present application, the mixing in step 1) is preferably ultrasonic mixing; the power of the ultrasonic is preferably 3000-6000 Hz, further preferably 3500-5500 Hz, and more preferably 4000-5000 Hz; the time of the ultrasonic is preferably 20-40 min, further preferably 25-35 min, and more preferably 30 min.

[0031] In the present application, the temperature of the vacuum treatment in step 2) is 60-100℃, preferably 65-90℃, further preferably 70-85℃, and more preferably 75-80℃; the vacuum degree of the vacuum treatment is ≤-0.095 MPa, preferably -0.01--0.09 MPa, further preferably -0.02--0.085 MPa, and more preferably -0.03--0.06 MPa; the time of the vacuum treatment is 4-8 h, preferably 4.5-7.5 h, further preferably 5-7 h, and more preferably 5.5-6 h; and the vacuum treatment is used to completely remove the organic solvent.

[0032] In the present application, the mixing in step 2) is preferably mixing the antioxidant, the pour point depressant, the metal organic framework compound, and the base transformer oil first, and then adding the mother liquor; the step-by-step addition can make each component disperse and dissolve gradually, prevent "clumping", and ensure that each component can play a role.

[0033] In the present application, the mixing in step 1) further preferably includes a vacuum drying operation; and the vacuum drying is preferably vacuum drying the base transformer oil and the ionic liquid respectively.

[0034] In the present application, the temperature of the vacuum drying treatment is preferably 60-120℃, further preferably 105-115℃, and more preferably 110℃; and the time of the vacuum drying treatment is preferably 6-24 h, further preferably 10-20 h, and more preferably 15-18 h.

[0035] In the present application, the preparation method of the high-performance transformer oil based on the imidazole ionic liquid effectively solves the problems of poor dispersion stability and poor water absorption of the ionic liquid in the oil, and ensures the long-term stability and industrial feasibility of the high-performance transformer oil based on the imidazole ionic liquid.

[0036] The technical solutions provided by the present application are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0037] Example 1 1) 25 parts of API Class II hydrogenated mineral oil (No. 10 transformer oil) and 25 parts of 1-tetradecyl-3-methylimidazolium tetrafluoroborate ionic liquid were vacuum dried at a temperature of 60℃ for 24 h to obtain dried API Class II hydrogenated mineral oil (moisture content of 6 ppm) and dried 1-tetradecyl-3-methylimidazolium tetrafluoroborate ionic liquid (moisture content of 8 ppm); the dried 1-tetradecyl-3-methylimidazolium tetrafluoroborate ionic liquid and the alkylbenzene were ultrasonically mixed at 5000 Hz for 30 min to obtain a mother liquor (mass concentration of 1 wt%); 2) 8 parts of antioxidant 2,6-di-tert-butyl-p-cresol, 8 parts of pour point depressant polymethacrylate and 8 parts of metal-organic framework compound MIL-101 were mixed with the dry API Class II hydrogenated mineral oil obtained in step 1), to obtain a mixture, the mixture was heated to 60°C, and high-speed magnetic stirring was carried out at a rotation speed of 800 rpm, then the mother liquor obtained in step 1) was added dropwise into the above mixture being magnetically stirred, vacuum treatment was carried out at 60°C and -0.095 MPa for 4 h, finally, filtration was carried out through a polytetrafluoroethylene filter membrane with a pore size of 0.22 μm, to obtain a clear and transparent imidazolium-based ionic liquid-based high-performance transformer oil.

[0038] Example 2 The difference between this example 2 and example 1 is only that the metal-organic framework compound MIL-101 in step 2) is replaced by MIL-100.

[0039] Example 3 The difference between this example 3 and example 1 is only that the metal-organic framework compound MIL-101 in step 2) is replaced by UiO-66.

[0040] Example 4 The difference between this example 4 and example 1 is only that the metal-organic framework compound MIL-101 in step 2) is replaced by ZIF-8.

[0041] Comparative Example 1 The difference between this comparative example 1 and example 1 is only that no metal-organic framework compound is added, and other operating conditions remain unchanged.

[0042] The performance of the imidazolium-based ionic liquid-based high-performance transformer oil prepared in the above examples 1~4 and comparative example 1 was detected. Among them, the detection method of breakdown voltage is: the transformer oil breakdown voltage test is carried out according to GB / T 507-2002 standard, which aims to evaluate the insulation strength of the oil. The test uses a standard oil cup (electrode gap 2.5 mm) and a high voltage tester. First, the oil sample is treated to eliminate bubbles, and the oil cup is thoroughly cleaned and dried; then slowly fill the oil, and stand for 15 minutes. When testing, the voltage is increased at a rate of 2 kV / s until the oil sample breaks down, and the same oil sample needs to complete 6 breakdowns, each breakdown is stirred and stands for 2 minutes, finally the first result is discarded, and the average value of the last 5 breakdown voltages is taken as the final result. The test is carried out in an environment with a humidity of 50%, and the electrode is clean and the gap is accurate to effectively monitor the insulation performance of the oil quality; The detection method of thermal conductivity is: using the transient hot-wire method (according to standard ASTM D7896), by inserting a thin metal hot-wire into the oil sample, applying a constant power short-time pulse heating, by precisely measuring the temperature rising rate of the hot-wire itself over time, directly calculating the thermal conductivity of the oil sample. Before testing, the oil sample is also heated to a specified temperature (40℃), and ensure that the oil sample is stationary, bubble-free; The detection method of flash point is: flash point detection mainly uses the Pensky-Martin closed cup method (according to standard GB / T 261-2021). During testing, 50 mL of oil sample is injected into the standard closed cup, and heated at a constant rate of 0.1℃ / s, while every 0.6℃, the mixture of vapor and air above the standard flame test cup is tested. The lowest temperature at which the first instantaneous flash occurs and the flame spreads to the entire liquid surface is recorded as the flash point. The test must be carried out in a fume hood and strictly prevent fire; The detection method of gas evolution is: using gas chromatography method (according to standard GB / T 10065-2007), under specific electric field (10 kV / mm) and temperature (80℃) conditions, evaluate the tendency of transformer oil to release or absorb gas under high voltage stress. During testing, the degassed oil sample is injected into a special gas evolution tank, a high voltage (10 kV / mm) is applied and kept at a constant temperature (80℃) for 24 h, then the gas composition (especially hydrogen) above the oil surface before and after the experiment is accurately analyzed by gas chromatograph. The results are expressed in terms of gas volume produced or absorbed per unit time, per unit volume of oil sample (usually μL / min). "Evolution" of gas is positive, and "absorption" is negative; The detection method of stability is: take 500 mL of new oil or running oil sample to be tested, dehydrate, degas and filter pretreatment according to standard method, to ensure the initial state is consistent. Use a special borosilicate glass aging tank with a sealed cover, seal for 30 days under constant temperature conditions, check and record whether visible sludge or precipitate is generated in the oil or not.

[0043] The results are shown in Table 1.

[0044] Table 1 Performance of high-performance transformer oil in Examples 1-4 and Comparative Example 1

[0045] As can be seen from Table 1, the performance of the high-performance transformer oil prepared by Examples 1-4 is better than that of Comparative Example 1, which shows that the addition of metal organic framework compound can significantly improve the performance of transformer oil. Among them, when MIL-100 is added as the metal organic framework compound of high-performance transformer oil, the performance of high-performance transformer oil is the best.

[0046] Example 5 The difference between this example 5 and example 1 is only that the ionic liquid in step 1) is replaced by 1-decyl-3-methylimidazolium tetrafluoroborate.

[0047] Example 6 The difference between this example 6 and example 1 is only that the ionic liquid in step 1) is replaced by 1-dodecyl-3-methylimidazolium tetrafluoroborate.

[0048] Example 7 The difference between this example 7 and example 1 is only that the ionic liquid in step 1) is replaced by 1-hexadecyl-3-methylimidazolium hexafluorophosphate.

[0049] Example 8 The difference between this example 8 and example 1 is only that the ionic liquid in step 1) is replaced by 1-decyl-3-methylimidazolium hexafluorophosphate.

[0050] Comparative Example 2 The difference between this comparative example 2 and example 1 is only that no ionic liquid is added, and other operation conditions remain unchanged.

[0051] Comparative Example 3 The difference between this comparative example 3 and example 1 is only that the ionic liquid in step 1) is replaced by 1-ethyl-3-methylimidazolium bisfluorosulfonylimide.

[0052] Comparative Example 4 The difference between this comparative example 4 and example 1 is only that the ionic liquid in step 1) is replaced by 1-hexyl-3-methylimidazolium bisfluorosulfonylimide.

[0053] Comparative Example 5 The difference between this comparative example 5 and example 1 is only that the ionic liquid in step 1) is replaced by tetramethylammonium hexafluorophosphate.

[0054] Comparative Example 6 The difference between this comparative example 6 and example 1 is only that the ionic liquid in step 1) is replaced by tetraoctylphosphonium bis(trifluoromethylsulfonyl)imide.

[0055] The performance of the modified high-performance transformer oil based on the above examples 5-8 and comparative example 2 is detected. Among them, the detection methods of breakdown voltage, thermal conductivity, flash point, gas evolution, stability remain unchanged. The results are shown in Table 2.

[0056] Table 2 Performance of high-performance transformer oil in examples 5-8 and comparative example 2

[0057] As can be seen from Table 2, the type of ionic liquid has a greater influence on the performance of the transformer, among the many types of ionic liquids, imidazole ionic liquid has the best effect, and the compatibility is poor if the chain is too short, which leads to poor long-term stability and gas separation, and the performance also decreases if the chain is too long; and through the comparison of Examples 5-8 and Comparative Examples 2-6, it can be seen that the 1-tetradecyl-3-methyl imidazole tetrafluoroborate salt achieves the best balance in various performances.

[0058] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A high performance transformer oil based on imidazolium ionic liquid, characterized in that, The components include the following mass fractions: 20-28 parts of base transformer oil, 20-28 parts of ionic liquid, 2-18 parts of antioxidant, 2-20 parts of pour point depressant, and 2-20 parts of metal organic framework compound; The ionic liquid includes imidazole tetrafluoroborate ionic liquid and / or imidazole hexafluorophosphate ionic liquid.

2. The high performance transformer oil based on imidazolium ionic liquid according to claim 1, characterized in that, The base transformer oil includes one or more of API Class II hydrogenated mineral oil, API Class III hydrogenated mineral oil, and alkyl naphthalene synthetic oil.

3. A high performance transformer oil based on imidazolium ionic liquid according to claim 2, characterized in that, The imidazole tetrafluoroborate ionic liquid includes one or more of 1-decyl-3-methyl imidazole tetrafluoroborate, 1-dodecyl-3-methyl imidazole tetrafluoroborate, 1-tetradecyl-3-methyl imidazole tetrafluoroborate, and 1-hexadecyl-3-methyl imidazole tetrafluoroborate; The imidazole hexafluorophosphate ionic liquid includes one or more of 1-decyl-3-methyl imidazole hexafluorophosphate, 1-dodecyl-3-methyl imidazole hexafluorophosphate, 1-tetradecyl-3-methyl imidazole hexafluorophosphate, and 1-hexadecyl-3-methyl imidazole hexafluorophosphate.

4. The high performance transformer oil based on imidazolium ionic liquid according to any one of claims 1 to 3, characterized in that, The antioxidant includes one or more of 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl phenol, and tetra-β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid pentaerythritol ester.

5. The high performance transformer oil based on imidazolium ionic liquid according to claim 4, characterized in that, The pour point depressant includes polymethyl acrylate and / or ethylene-propylene copolymer.

6. A high performance transformer oil based on imidazolium ionic liquid according to claim 5, characterized in that, The metal organic framework compound includes one or more of MIL-101, MIL-100, UiO-66, and ZIF-8.

7. A process for the preparation of a high performance transformer oil based on imidazolium ionic liquids according to any one of claims 1 to 6, characterized in that, The method includes the following steps: 1) mixing the ionic liquid with aromatic hydrocarbon compounds to obtain a mother liquor; 2) mixing the mother liquor, antioxidant, pour point depressant, metal organic framework compound, and base transformer oil, and performing vacuum treatment to obtain the imidazole ionic liquid-based high-performance transformer oil.

8. The method for preparing high-performance transformer oil based on imidazole ionic liquid according to claim 7, characterized in that, The mass concentration of the mother liquor in step 1) is 1-5 wt%; The aromatic hydrocarbon compounds include alkyl benzene and / or methyl naphthalene.

9. The method for preparing high-performance transformer oil based on imidazole ionic liquid according to claim 8, characterized in that, The temperature of the vacuum treatment in step 2) is 60-100°C, the vacuum degree is ≤-0.095 MPa, and the time is 4-8 h.

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