A modified silica nano-sieve, its preparation method and application, and insulating oil obtained by modification

Abstract

The present invention relates to the technical field of insulating oil additives, and particularly to a modified silica nano-sieve, a preparation method and application thereof, and an insulating oil obtained by modification. In the present invention, cetyltrimethylammonium bromide, ammonia water solution, ethanol solution and tetraethoxysilane are used to prepare a white solid, which is combined with hydrochloric acid and absolute ethanol to prepare a silica nano-sieve. Subsequently, the prepared silica nano-sieve is modified with oleic acid to obtain a modified silica nano-sieve. Adding the modified silica nano-sieve to mineral insulating oil in a suitable proportion can improve the thermal conductivity of the mineral insulating oil and make its heat dissipation performance better. The present invention provides a new solution for improving the thermal conductivity and heat dissipation performance of mineral insulating oil.

Description

Technical Field

[0001] The present invention relates to the technical field of insulating oil additives, and particularly to a modified silica nano-sieve, a preparation method and an application thereof, and an insulating oil obtained by modification. Background Art

[0002] A transformer is a device that uses the principle of electromagnetic induction to change the AC voltage and is an infrastructure for power transmission and distribution. During the operation of a transformer, corona or breakdown accidents are likely to occur at its high-voltage end, causing losses to staff and equipment. To solve this problem, the transformer body composed of an iron core and its windings is placed in an oil tank filled with insulating oil. Insulating oil has a much higher insulation strength than air. Immersing materials in oil can not only improve the insulation strength and prevent breakdown, but also protect against moisture erosion. Moreover, the density of insulating oil is small, and moisture and impurities precipitate at the bottom, minimizing the impact on the transformer.

[0003] Most oil-immersed transformers use mineral insulating oil mainly composed of aromatic hydrocarbons and naphthenic hydrocarbons as the liquid insulating medium. However, during the operation of the transformer, a large amount of heat is easily generated. Since the oil has poor thermal conductivity and a low flash point, it is necessary to improve the thermal conductivity of the insulating oil in applications to improve the heat dissipation efficiency of the equipment and keep the operating temperature of the transformer stable. Research shows that nanofluids composed of nanoparticles mixed with traditional fluid media generally have a high thermal conductivity. Therefore, adding nanoparticles with excellent thermal conductivity to mineral oil can effectively improve its thermal conductivity. However, different particles have different modification effects on insulating oil, and those skilled in the art still need to continuously explore to provide more technical solutions for improving the thermal conductivity of mineral insulating oil. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified silica nano-sieve and a preparation method thereof, which can be used to improve the thermal conductivity of mineral insulating oil.

[0005] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a modified silica nano-sieve, comprising the following steps:

[0007] S1. Mix cetyltrimethylammonium bromide, ammonia water solution, and ethanol solution to obtain a mixed solution;

[0008] S2. Drop tetraethoxysilane into the mixed solution obtained in S1 for reaction to obtain a white solid;

[0009] S3. Add the white solid obtained in S2 to a mixed solution of hydrochloric acid and absolute ethanol, and react to obtain a silica nano-sieve;

[0010] S4. Modify the silica nano-sieve obtained in S3 with oleic acid in an organic solvent to obtain a modified silica nano-sieve.

[0011] Optionally, in S2, the dosage ratio of tetraethoxysilane to cetyltrimethylammonium bromide, aqueous ammonia solution, and ethanol solution in the mixed solution described in S1 is 1 ml: 0.1 - 0.2 g: 1 - 2 ml: 50 - 80 ml;

[0012] In S3, the volume ratio of the hydrochloric acid to absolute ethanol is 1: 240 - 260;

[0013] The dosage ratio of the tetraethoxysilane to the hydrochloric acid is 1 ml: 0.45 - 0.5 ml;

[0014] In S4, the dosage ratio of the oleic acid to the silica nano-sieve is 0.5 - 2 ml: 1 g.

[0015] Optionally, the mass concentration of the aqueous ammonia solution is 20 - 30%; the volume concentration of the ethanol solution is 20 - 40%;

[0016] The mass concentration of the hydrochloric acid is 30 - 35%.

[0017] Optionally, the temperature of the mixing in S1 is 30 - 40 °C, and the mixing time is 1 - 60 min;

[0018] The reaction in S2 specifically is to maintain at 30 - 40 °C for 21 - 30 h first, and then maintain at 60 - 80 °C for 10 - 15 h;

[0019] The temperature of the reaction in S3 is 60 - 70 °C, and the reaction time is 5 - 8 h;

[0020] The temperature of the modification in S4 is 60 - 80 °C, and the modification time is 2 - 4 h.

[0021] The present invention also provides a modified silica nano-sieve.

[0022] The present invention also provides the application of the modified silica nano-sieve in improving the thermal conductivity of mineral insulating oil, including the following steps:

[0023] Mix the modified silica nano-sieve with mineral insulating oil using the ultrasonic dispersion method to obtain a modified silica nano-sieve insulating oil.

[0024] Optionally, the addition concentration of the modified silica nano-sieve in the mineral insulating oil is 0.01 - 0.2 g / L.

[0025] Optionally, the mineral insulating oil includes one of Karamay #25 mineral oil, Karamay #45 mineral oil, and Karamay #10 mineral oil.

[0026] The present invention also provides a modified silica nano-sieve insulating oil obtained by adding the modified silica nano-sieve to mineral insulating oil.

[0027] The silica (SiO2) nano-sieve provided by the present invention has a loose and porous appearance. This structure can increase the contact area with the insulating oil, form a relatively thick adsorption layer with a large effective area on the surface of the nano-sieve, thereby improving the heat transfer efficiency between the nano-material and the insulating oil. However, this characteristic also causes the SiO2 nano-sieve to be prone to agglomeration, making it impossible to be uniformly dispersed in the insulating oil. To solve this problem, the present invention uses oleic acid to perform surface modification on the SiO2 nano-sieve to obtain a modified SiO2 nano-sieve. The modification can improve the dispersion performance of the SiO2 nano-sieve in the insulating oil without affecting the heat transfer efficiency. At the same time, the nano-sieve has extremely high reaction activity. Due to the improved dispersion performance, the modified SiO2 nano-sieve is more likely to perform random Brownian motion in the insulating oil, thereby improving the heat transfer efficiency. Therefore, the modified SiO2 nano-sieve can efficiently improve the thermal conductivity of mineral oil and has a significant heat dissipation effect. Specific embodiments

[0028] The present invention provides a preparation method of a modified silica nano-sieve, comprising the following steps:

[0029] S1. Mix cetyltrimethylammonium bromide, ammonia water solution, and ethanol solution to obtain a mixed solution;

[0030] S2. Drop tetraethoxysilane into the mixed solution described in S1 for reaction to obtain a white solid;

[0031] S3. Add the white solid obtained in S2 to a mixed solution of hydrochloric acid and absolute ethanol, and react to obtain a silica nano-sieve;

[0032] S4. In an organic solvent, use oleic acid to modify the silica nano-sieve prepared in S3 to obtain a modified silica nano-sieve.

[0033] In the present invention, the mass concentration of the ammonia water solution described in S1 is 20-30%, preferably 22-28%, and more preferably 24-26%; the volume concentration of the ethanol solution is 20-40%, preferably 22-38%, more preferably 25-35%, and even more preferably 28-32%;

[0034] The temperature of the mixing is 30-40°C, preferably 33-37°C; the mixing time is 1-60 min, preferably 10-50 min, more preferably 20-40 min, and even more preferably 25-35 min.

[0035] In the present invention, the dosage ratio of tetraethoxysilane in S2 to cetyltrimethylammonium bromide, aqueous ammonia solution, and ethanol solution in the mixed solution in S1 is 1 ml: 0.1 - 0.2 g: 1 - 2 ml: 50 - 80 ml, preferably 1 ml: 0.12 - 0.18 g: 1 - 1.5 ml: 52 - 75 ml, more preferably 1 ml: 0.14 - 0.16 g: 1 - 1.2 ml: 55 - 70 ml, and even more preferably 1 ml: 0.15 g: 1 ml: 58 - 65 ml;

[0036] The reaction in S2 specifically involves first maintaining at 30 - 40 °C, preferably 32 - 37 °C, more preferably 34 - 36 °C for 21 - 30 h, preferably 22 - 28 h, more preferably 23 - 25 h, and then maintaining at 60 - 80 °C, preferably 62 - 78 °C, more preferably 65 - 75 °C, and even more preferably 68 - 72 °C for 10 - 15 h, preferably 11 - 14 h, more preferably 11.5 - 13 h;

[0037] The obtaining of the white solid in S2 further includes centrifugation and washing.

[0038] In the present invention, the volume ratio of hydrochloric acid to absolute ethanol in S3 is 1: 240 - 260, preferably 1: 245 - 255;

[0039] The mass concentration of the hydrochloric acid is 30 - 35%, preferably 31 - 34%;

[0040] The dosage ratio of tetraethoxysilane in S2 to hydrochloric acid in S3 is 1 ml: 0.45 - 0.5 ml, preferably 1 ml: 0.46 - 0.49 ml, more preferably 1 ml: 0.48 ml;

[0041] The temperature of the reaction in S3 is 60 - 70 °C, preferably 62 - 68 °C, more preferably 64 - 66 °C; the reaction time is 5 - 8 h, preferably 6 - 8 h, more preferably 6.5 - 7.5 h.

[0042] In the present invention, the dosage ratio of oleic acid to silica nano - sieve in S4 is 0.5 - 2 ml: 1 g, preferably 1 - 1.5 ml: 1 g;

[0043] The temperature of the modification in S4 is 60 - 80 °C, preferably 65 - 75 °C; the modification time is 2 - 4 h, preferably 2.5 - 3.5 h;

[0044] The modification in S4 further includes centrifugation washing and vacuum drying. The temperature of the vacuum drying is 60 - 80 °C, preferably 70 °C, and the vacuum drying time is 23 - 26 h, more preferably 24 h.

[0045] The present invention also provides modified silica nanosieves.

[0046] The present invention also provides an application of the modified silica nanosieves in improving the thermal conductivity of mineral insulating oil, comprising the following steps:

[0047] Using the ultrasonic dispersion method to mix the modified silica nanosieves with the mineral insulating oil to obtain a modified silica nanosieve insulating oil.

[0048] In the present invention, the addition concentration of the modified silica nanosieves in the mineral insulating oil is 0.01 - 0.2 g / L.

[0049] In the present invention, the mineral insulating oil includes one of Karamay #25 mineral oil, Karamay #45 mineral oil, and Karamay #10 mineral oil.

[0050] The present invention also provides a modified silica nanosieve insulating oil obtained by adding the modified silica nanosieves to the mineral insulating oil.

[0051] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] Take 0.15 g of cetyltrimethylammonium bromide, 1 mL of 25% ammonia water solution, and 60 mL of 30% ethanol solution and continuously stir in an oil bath heating pot at 35°C for 30 min to fully mix the components. Slowly drop 1 mL of tetraethoxysilane into the stirred mixed solution, react at 35°C for 24 h, and then raise the temperature to 70°C and react for 12 h. After the reaction, perform centrifugation using a high-speed centrifuge, with the centrifuge speed being 1500 r / min and the centrifugation time being 30 min, and wash the centrifuged white solid three times with deionized water and anhydrous ethanol respectively. After washing, add the white solid to a mixed solution of 480 μL of hydrochloric acid with a mass concentration of 33% and 120 mL of anhydrous ethanol, and react at a constant temperature of 65°C for 7 h using an oil bath heating. Take the reactant and centrifuge it at 1500 r / min for 30 min, then wash the centrifuged solid three times with deionized water and anhydrous ethanol respectively, and then dry it in a vacuum at 70°C for 24 h to obtain silica (SiO2) nanosieves with a loose and porous morphology.

[0054] 0.5 g of the dried nano-sieve and 0.5 mL of oleic acid were added to 50 mL of cyclohexane solvent, and under continuous stirring, it was heated in an oil bath and reacted at a constant temperature of 70 °C for 3 h. The reaction precipitate was taken for centrifugation, the centrifuge speed was set at 3000 r / min, and the centrifugation time was 5 min. After washing, it was vacuum dried at 70 °C for 24 h to obtain modified SiO2 nano-sieve with good dispersibility in mineral oil.

[0055] Example 2

[0056] 0.1 g of cetyltrimethylammonium bromide, 2 mL of 20% ammonia water solution, and 70 mL of 25% ethanol solution were placed in an oil bath heating pot at 40 °C and continuously stirred for 25 min to fully mix the components. 1 mL of tetraethoxysilane was slowly dropped into the continuously stirred mixed solution, reacted at 30 °C for 28 h, and then heated to 65 °C and reacted for 13 h. After the reaction, centrifugation was carried out using a high-speed centrifuge, the centrifuge speed was 1500 r / min, and the centrifugation time was 30 min. The white solid obtained by centrifugation was washed three times with deionized water and absolute ethanol respectively. After washing, the white solid was added to a mixed solution of 450 μL of hydrochloric acid with a mass concentration of 33% and 110 mL of absolute ethanol, and reacted at a constant temperature of 70 °C for 6 h using an oil bath heating. After taking the reactant and centrifuging it at 1500 r / min for 30 min using a centrifuge, the solid obtained by centrifugation was washed three times with deionized water and absolute ethanol respectively, and then vacuum dried at 70 °C for 24 h to obtain silica (SiO2) nano-sieve with a loose and porous morphology.

[0057] 0.5 g of the dried nano-sieve and 0.75 mL of oleic acid were added to 50 mL of cyclohexane solvent, and under continuous stirring, it was heated in an oil bath and reacted at a constant temperature of 75 °C for 2.5 h. The reaction precipitate was taken for centrifugation, the centrifuge speed was set at 3000 r / min, and the centrifugation time was 5 min. After washing, it was vacuum dried at 70 °C for 24 h to obtain modified SiO2 nano-sieve with good dispersibility in mineral oil.

[0058] Example 3

[0059] The modified SiO2 nano-sieve prepared in Example 1 was added to Karamay #25 mineral oil at an addition concentration of 0.05 g / L. The mixed oil sample was ultrasonically oscillated for 70 min using the ultrasonic dispersion method, and the ultrasonic power was 960 W. After the oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90 °C for 48 h. After drying, modified SiO2 nano-sieve #25 mineral oil was obtained.

[0060] Examples 4 - 6

[0061] Based on Example 3, the differences between Examples 4 to 6 and Example 3 are that the addition concentrations of the modified SiO2 nano-sieve are 0.10 g / L, 0.15 g / L, and 0.25 g / L respectively.

[0062] Example 7

[0063] The modified SiO2 nano-sieve prepared in Example 1 was added to Karamay #45 mineral oil at an addition concentration of 0.05 g / L. The mixed oil sample was ultrasonically oscillated for 70 min by ultrasonic dispersion method, and the ultrasonic power was 960 W. After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90 °C for 48 h. After drying, the modified SiO2 nano-sieve #45 mineral oil was obtained.

[0064] Examples 8 to 9

[0065] Based on Example 7, the differences between Examples 4 to 6 and Example 3 are that the addition concentrations of the modified SiO2 nano-sieve are 0.10 g / L and 0.15 g / L respectively.

[0066] Comparative Example 1

[0067] The SiO2 nano-sieve prepared in Example 1 was added to Karamay #25 mineral oil at an addition concentration of 0.05 g / L. The mixed oil sample was ultrasonically oscillated for 70 min by ultrasonic dispersion method, and the ultrasonic power was 960 W. After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90 °C for 48 h. After drying, the SiO2 nano-sieve #25 mineral oil was obtained.

[0068] Comparative Examples 2 to 3

[0069] Based on Comparative Example 1, the differences between Comparative Examples 2 to 3 and Comparative Example 1 are that the addition concentrations of the SiO2 nano-sieve are 0.10 g / L and 0.15 g / L respectively.

[0070] Comparative Example 4

[0071] The modified SiO2 nano-sieve prepared in Example 1 was added to palm oil fatty acid ester insulating oil (PFAE) at an addition concentration of 0.05 g / L. The mixed oil sample was ultrasonically oscillated for 70 min by ultrasonic dispersion method, and the ultrasonic power was 960 W. After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90 °C for 48 h. After drying, the modified SiO2 nano-sieve PFAE insulating oil was obtained.

[0072] Comparative Examples 5 to 6

[0073] Based on Comparative Example 4, the differences between Comparative Examples 5 to 6 and Comparative Example 4 are that the addition concentrations of the modified SiO2 nano-sieve are 0.10 g / L and 0.15 g / L respectively.

[0074] Experimental Example

[0075] To characterize the thermal conductivity of the oil samples, the thermal conductivities of Karamay #25 mineral oil, Karamay #45 mineral oil, palm oil fatty acid ester insulating oil (PFAE), and the oil samples prepared in Examples 3-9 and Comparative Examples 1-6 were measured at 25 °C and 90 °C using a TC3010 series liquid thermal conductivity meter.

[0076] Since oil can absorb moisture in the air, prolonged storage can lead to a high water content in the oil. Before testing, the oil samples need to be vacuum-dried at 90 °C for 48 h to eliminate the influence of moisture on the experimental results, making the measured data more reliable and accurate.

[0077] The results are shown in the following table.

[0078] Table 1: Thermal Conductivities of Oil Samples at 25 °C and 90 °C

[0079]

[0080]

[0081] From the data in the above table, it can be seen that transforming the nano-SiO2 material into SiO2 nano-sieve by means of morphology control can improve the thermal conductivity of insulating oil. The modified SiO2 nano-sieve obtained by surface modification of SiO2 nano-sieve with oleic acid can more significantly enhance the thermal conductivity of mineral insulating oil, thus making the heat dissipation performance of mineral insulating oil better. By comparing the improvement effects of the surface-modified SiO2 nano-sieve on the thermal conductivities of natural esters and mineral oils, it can be found that the modified SiO2 nano-sieve provided by the present invention has stronger applicability in mineral insulating oil.

[0082] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Application of a modified silica nano sieve in improving the thermal conductivity of mineral insulating oil, characterized in that, It includes the following steps: Using the ultrasonic dispersion method to mix the modified silica nano-sieve with mineral insulating oil to obtain the modified silica nano-sieve insulating oil; The preparation method of the modified silica nano-sieve includes the following steps: S1. Mix cetyltrimethylammonium bromide, ammonia water solution, and ethanol solution to obtain a mixed solution; S2. Drop tetraethoxysilane into the mixed solution described in S1 for reaction to obtain a white solid; S3. Add the white solid obtained in S2 to a mixed solution of hydrochloric acid and anhydrous ethanol, and react to obtain silica nano-sieve; S4. In an organic solvent, use oleic acid to modify the silica nano-sieve prepared in S3 to obtain a modified silica nano-sieve; The mass concentration of the ammonia water solution is 20 - 30%; the volume concentration of the ethanol solution is 20 - 40%; In S2, the dosage ratio of tetraethoxysilane to cetyltrimethylammonium bromide, ammonia water solution, and ethanol solution in the mixed solution described in S1 is 1 ml: 0.1 - 0.2 g: 1 - 2 ml: 50 - 80 ml; The mass concentration of the hydrochloric acid solution is 30 - 35%; The dosage ratio of tetraethoxysilane to hydrochloric acid is 1 ml: 0.45 - 0.5 ml; In S4, the dosage ratio of oleic acid to silica nano-sieve is 0.5 - 2 ml: 1 g; The reaction in S2 is specifically to maintain at 30 - 40 °C for 21 - 30 h first, and then maintain at 60 - 80 °C for 10 - 15 h; The temperature of the reaction in S3 is 60 - 70 °C, and the reaction time is 5 - 8 h; The temperature of the modification in S4 is 60 - 80 °C, and the modification time is 2 - 4 h.

2. The application according to claim 1, wherein The addition concentration of the modified silica nano-sieve in mineral insulating oil is 0.01 - 0.2 g / L.

3. The application according to claim 1 or 2, characterized in that, The mineral insulating oil includes one of Karamay #25 mineral oil, Karamay #45 mineral oil, and Karamay # 10 mineral oil.

4. The application according to claim 1, characterized in that, The temperature of the mixing in S1 is 30 - 40 °C, and the mixing time is 1 - 60 min.

5. The application according to claim 1, wherein In S3, the volume ratio of hydrochloric acid to anhydrous ethanol is 1: 240 - 260.

6. The modified silica nano-sieve insulating oil obtained by any one of claims 1 - 5.

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