Base oil of transformer oil, preparation method of base oil and transformer oil

Abstract

The invention relates to the technical field of transformer oil, in particular to base oil of transformer oil, a preparation method of the base oil and the transformer oil. The preparation method of the transformer oil base oil comprises the following steps: S1, mixing naphthenic base distillate oil with hydrogen, and carrying out hydrotreating to obtain hydrotreated generated oil; s2, mixing the hydrotreated generated oil with hydrogen, and performing hydrodewaxing treatment to obtain hydrodewaxed generated oil; s3, mixing the hydrodewaxing generated oil with hydrogen, and performing finishing treatment to obtain refined generated oil; s4, carrying out gas-liquid separation on the refined oil to obtain a liquid product; and carrying out vacuum fractionation on the liquid product, and extracting from a side line at the temperature of more than 260 DEG C to obtain the base oil of the class-U transformer oil or the base oil of the class-I transformer oil. The method realizes hydrogenation production of the U-type or I-type transformer oil base oil by the same device, and has the advantages of high device utilization rate, high product yield, flexible production and the like.

Description

Technical Field

[0001] The invention relates to the technical field of transformer oil, in particular to a transformer oil base oil and a preparation method thereof and transformer oil. Background Art

[0002] In order to ensure the long-term safe operation of electrical equipment, transformer oil must have excellent low-temperature performance to meet the low-temperature starting requirements of electrical equipment; excellent electrical performance; good anti-gassing performance, absorbing hydrogen generated by partial discharge to prevent air gap discharge from damaging the insulation of electrical equipment; good oxidation stability, slowing down the oxidation of oil products as much as possible, and reducing the formation of sludge, which is conducive to the long-term and safe operation of electrical equipment. Among the above properties of transformer oil, electrical performance, anti-oxidation performance, anti-gassing performance, and solubility are contradictory. To ensure good electrical performance and anti-oxidation performance, transformer oil needs to be deeply refined with low aromatic content; and to ensure anti-gassing performance and solubility, a certain content of aromatics needs to be retained in transformer oil. Therefore, to meet the above performance, the composition of transformer oil needs to contain a higher content of cycloalkanes and an appropriate content of aromatics.

[0003] The U-class transformer oil standard GB2536-2011 of the National Standards Committee (GB) specifies the performance requirements of transformer oil without antioxidants. At present, most transformer oils on the market are transformer oils containing antioxidants. In order to ensure that the product has good electrical properties and sensitivity to synthetic antioxidants, its base oil generally adopts deep refining processing technology and process conditions. Since most of the natural antioxidants with antioxidant effects - sulfides (some sulfides have antioxidant effects, most sulfides have no antioxidant effects) and polar aromatics (most aromatics have no antioxidant effects) are removed, its own oxidation stability is poor and cannot meet the requirements of the oxidation stability index of U-class transformer oil in the standard GB2536-2011.

[0004] The early preparation method of antioxidant-free cycloalkyl transformer oil is to add sulfide dibenzyl disulfide (DBDS) to the transformer oil base oil with a higher refining depth to improve the oxidation stability, but the obtained product cannot pass the more stringent corrosive sulfur test of IEC60296 standard. DBDS is the main cause of electrical equipment failure due to copper sulfide. IEC60296-2012 standard no longer allows transformer oil to contain DBDS. Traditional antioxidant-free transformer oil uses sulfur-containing cycloalkyl crude oil fraction as raw material, adopts a mild refining process, and retains more of its own sulfides and aromatics to ensure its oxidation stability. However, the transformer oil produced by this method has poor electrical properties due to the low refining depth, and sometimes contains corrosive sulfides. It can only meet the IEC60296-2003 standard, and cannot meet the more stringent corrosion test items of IEC60296-2012 standard.

[0005] The existing preparation processes of antioxidant-free transformer oil include the following:

[0006] Transformer oil without antioxidants that meets the IEC60296 standard is produced by blending hydrogenated cycloalkane transformer oil base oil with an aniline point of 63-84°C and solvent refined paraffin base oil with an aromatic content greater than 9%. However, paraffin base oil is specific, and other paraffin base oils cannot produce qualified transformer oil without antioxidants that meets the IEC60296 standard.

[0007] The transformer oil without antioxidant is produced by using hydrogenation process to produce low pour point transformer oil base oil or synthetic hydrocarbon oil and solvent refining process to produce bright oil and then treated with 1% kaolin. However, this method requires additional kaolin treatment after blending, which increases the production process and cost and produces solid waste that pollutes the environment.

[0008] The production is produced by blending low-sulfur and low-aromatic hydrogenated transformer oil base oil with high-sulfur medium-aromatic hydrogenated transformer oil base oil. Among them, the low-sulfur and low-aromatic hydrogenated transformer oil base oil is produced by a hydrogenation treatment-hydrogenation decondensation-hydrogenation supplementary refining process at a pressure of 15MPa; the high-sulfur medium-aromatic hydrogenated transformer oil base oil is produced by a solvent refining-kaolin supplementary refining process using high-sulfur paraffin-based crude oil fraction as a raw material. However, the method requires kaolin supplementation treatment before blending, which also increases the production process and cost and produces solid waste that pollutes the environment.

[0009] In the above preparation process, the transformer oil base oil needs to be refined with kaolin for denitrification and decolorization, which brings about the problem of handling waste kaolin; the use of high-pressure hydrogenation technology has the problems of complex process flow and large one-time investment scale; the use of two transformer oil base oils with different aromatic hydrocarbon contents to blend and produce high-quality transformer oil base oil has the problems of complex process flow and high production cost.

[0010] In view of this, this invention is proposed. Summary of the invention

[0011] The first object of the present invention is to provide a method for preparing a transformer oil base oil. The method uses cycloalkane distillate oil as a raw material and can directly generate a U-type transformer oil base oil or a I-type transformer oil base oil through hydrogenation treatment, hydrodecondensation, supplementary refining and fractionation processes; the method realizes hydrogenation production of the U-type transformer oil base oil or the I-type transformer oil base oil in the same device, and has the advantages of high device utilization, high product yield, flexible production and the like.

[0012] A second object of the present invention is to provide a transformer oil base oil.

[0013] A third object of the present invention is to provide a transformer oil.

[0014] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0015] In a first aspect, the present invention provides a method for preparing a transformer oil base oil, comprising the following steps:

[0016] S1, mixing the cycloalkane fraction oil with hydrogen, and then performing a hydrogenation treatment to obtain a hydrogenation product oil;

[0017] S2, mixing the hydrotreated product oil with hydrogen, and then performing a hydrodecondensation treatment to obtain a hydrodecondensation product oil;

[0018] S3, mixing the hydrodecondensation product oil with hydrogen, and then performing additional refining treatment to obtain a refined product oil;

[0019] S4, the refined product oil is subjected to gas-liquid separation to obtain a liquid product; the liquid product is subjected to vacuum fractionation, and a side line above 260° C. is produced to obtain a Class U transformer oil base oil or a Class I transformer oil base oil.

[0020] Furthermore, in step S1, the cycloalkyl distillate oil includes cycloalkyl normal second-line distillate oil and / or cycloalkyl minus first-line distillate oil.

[0021] Preferably, the cycloalkyl distillate oil comprises cycloalkyl normal second-line distillate oil and / or a mixed oil of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil in a mass ratio of 1:1; or, the cycloalkyl distillate oil comprises cycloalkyl minus first-line distillate oil and / or a mixed oil of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil in a mass ratio of 1:1.

[0022] Further, step S1 includes at least one of the following features (1) to (5);

[0023] (1) The hydroprocessing is carried out under the action of a hydroprocessing catalyst, wherein the hydroprocessing catalyst comprises a Group VIII metal oxide and / or a Group VIB metal oxide;

[0024] (2) The pressure of the hydrotreatment is 8.0 to 10.0 MPa;

[0025] (3) The temperature of the hydrotreatment is 300-370°C;

[0026] (4) The volume space velocity of the hydroprocessing is 0.2 to 1.0 h -1 ;

[0027] (5) The volume ratio of the hydrogen to the cycloalkane distillate oil is (800-1200):1.

[0028] Further, in step S1, the hydroprocessing catalyst includes nickel oxide and / or tungsten trioxide;

[0029] And / or, the temperature of the hydrotreatment is 340-350°C; or, the temperature of the hydrotreatment is 350-360°C.

[0030] Further, step S2 includes at least one of the following features (1) to (5);

[0031] (1) The hydrodegradation treatment is carried out under the action of a hydrodegradation catalyst, wherein the hydrodegradation catalyst comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the hydrodegradation catalyst comprises nickel oxide and / or tungsten trioxide;

[0032] (2) The pressure of the hydrodecondensation treatment is 8.0 to 10.0 MPa;

[0033] (3) The temperature of the hydrodecondensation treatment is 280-340° C.;

[0034] (4) The volumetric space velocity of the hydrodecondensation treatment is 0.8 to 3.0 h -1 ;

[0035] (5) The volume ratio of the hydrogen gas to the hydroprocessed oil is (800-1200): 1. Further, step S3 includes at least one of the following features (1) to (5);

[0036] (1) The supplementary refining treatment is carried out under the action of a supplementary refining catalyst, and the supplementary refining catalyst comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the supplementary refining catalyst comprises at least one of nickel oxide, tungsten trioxide and molybdenum trioxide;

[0037] (2) The pressure of the supplementary refining treatment is 8.0 to 10.0 MPa;

[0038] (3) The temperature of the supplementary refining treatment is 290 to 360° C.;

[0039] (4) The volumetric space velocity of the supplementary refining treatment is 0.3 to 2.0 h -1 ;

[0040] (5) The volume ratio of the hydrogen to the hydrodegradation oil is (800-1200):1.

[0041] In a second aspect, the present invention further provides a transformer oil base oil, including a Class U transformer oil base oil or a Class I transformer oil base oil;

[0042] The U-class transformer oil base oil or the I-class transformer oil base oil is prepared by the transformer oil base oil preparation method as described above.

[0043] Furthermore, in the U-type transformer oil base oil, the sulfur content is greater than 90.0 mg / kg, and the nitrogen content is less than 40.0 mg / kg; the CA value of the U-type transformer oil base oil is 4.5% to 5.5%, the pour point is less than -57°C, and the kinematic viscosity at 40°C is less than 12.0 mm 2 / s, closed cup flash point>140℃; the oxidation stability of the U-type transformer oil base oil at 120℃, 164h, total acid value<0.27mgKOH / g, oil sludge<0.0054%, and dielectric loss factor<0.082 at 90℃.

[0044] Furthermore, the sulfur content of the Class I transformer oil base oil is less than 10.0 mg / kg, and the nitrogen content is less than 3.0 mg / kg; the CA value of the Class I transformer oil base oil is less than 4.7%, the pour point is less than -57°C, and the kinematic viscosity at 40°C is less than 12.0 mm 2 / s, closed cup flash point>140℃.

[0045] In a third aspect, the present invention further provides a transformer oil, including Class U transformer oil or Class I transformer oil;

[0046] The U-type transformer oil comprises the U-type transformer oil base oil as described above;

[0047] The Class I transformer oil comprises an antioxidant and the Class I transformer oil base oil as described above, wherein the content of the antioxidant in the Class I transformer oil is 0.2wt%±0.05wt%; the oxidation stability of the Class I transformer oil at 120°C and 500h is as follows: the total acid value is less than 0.22mgKOH / g, the oil sludge is less than 0.0038%, and the dielectric loss factor at 90°C is less than 0.035.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The preparation method of transformer oil base oil of the present invention, under medium pressure (8.0~10.0MPa), takes cycloalkyl distillate as raw material, adopts non-precious metal catalyst, can directly generate U class transformer oil base oil or I class transformer oil base oil through hydrogenation treatment-hydrodecondensation-supplementary refining-fractionation process, realizes the hydrogenation production of U class transformer oil base oil or I class transformer oil base oil by the same device only through the adjustment of feedstock oil and hydrogenation process, has the advantages of rich product variety of production device, small device investment scale, flexible device production, etc.; solves the problem of large investment of two sets of production devices.

[0050] 2. The preparation method of transformer oil base oil of the present invention adopts a full hydrogenation process when processing cycloalkane distillate oil to produce U-type transformer oil base oil, adopts a selective hydrogenation catalyst to remove tricyclic and higher aromatic hydrocarbons that are not conducive to oxidation stability while retaining monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons and natural antioxidant sulfides that are beneficial to oxidation stability, thereby improving the yield and oxidation stability of the U-type transformer oil base oil; and solves the problems of low yield of products and generation of a large amount of low value-added by-products in the process of hydrodeacidification-furfural refining-clay refining.

[0051] 3. The preparation method of transformer oil base oil of the present invention realizes the transformer oil full hydrogenation process under medium pressure conditions through different high-activity catalyst grading, avoids the use of high-pressure hydrogenation equipment to increase equipment investment and operation severity, and the transformer oil base oil produced under medium pressure conditions retains an appropriate amount of aromatics to meet the requirements of Class U and Class I transformer oils in GB2536-2011; the transformer oil base oil prepared by the method has the characteristics of good low temperature performance, solubility and oxidation stability, safe operation and low hydrogen consumption. DETAILED DESCRIPTION

[0052] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0053] The transformer oil base oil and its preparation method and the transformer oil of the present invention are specifically described below.

[0054] In some embodiments of the present invention, a method for preparing a transformer oil base oil is provided, comprising the following steps:

[0055] S1, mixing the cycloalkane fraction oil with hydrogen, and then performing a hydrogenation treatment to obtain a hydrogenation product oil;

[0056] S2, mixing the hydrotreated product oil with hydrogen, and then performing a hydrodecondensation treatment to obtain a hydrodecondensation product oil;

[0057] S3, mixing the hydrodecondensation product oil with hydrogen, and then performing additional refining treatment to obtain refined product oil;

[0058] S4, the refined product oil is subjected to gas-liquid separation to obtain a liquid product; the liquid product is subjected to vacuum fractionation, and a side line with a temperature greater than 260° C. is produced to obtain a Class U transformer oil base oil or a Class I transformer oil base oil.

[0059] The invention mixes cycloalkane fraction oil with hydrogen and conducts hydrogenation treatment to remove heteroatoms such as sulfur, nitrogen, oxygen and the like in the raw material and saturate aromatic hydrocarbons to obtain hydrogenation product oil; mixes the hydrogenation product oil with hydrogen and conducts hydrodecondensation treatment to selectively remove macromolecular normal alkanes with high condensation points to obtain hydrodecondensation product oil; mixes the hydrodecondensation product oil with hydrogen and conducts supplementary refining treatment to further saturate olefins and aromatic hydrocarbons, and then conducts gas-liquid separation and vacuum fractionation, wherein the side line product with a temperature of more than 260° C. in the vacuum tower is obtained to obtain transformer oil base oil.

[0060] The method for preparing transformer oil base oil of the present invention uses cycloalkane distillate oil as a raw material, and can directly generate U-type transformer oil base oil or I-type transformer oil base oil through a hydrogenation treatment-hydrodecondensation-supplementary refining-fractionation process; the method realizes hydrogenation production of U-type transformer oil base oil or I-type transformer oil base oil in the same device, and has the advantages of high device utilization rate, high product yield, flexible production, etc.; and the prepared transformer oil base oil retains a proper amount of aromatics, can meet the requirements of U-type and I-type transformer oils in GB2536-2011, and has the characteristics of good low-temperature performance, solubility and oxidation stability.

[0061] In some embodiments of the present invention, in step S1, the cycloalkyl distillate oil includes cycloalkyl normal second-line distillate oil and / or cycloalkyl minus first-line distillate oil.

[0062] In some embodiments of the present invention, in step S1, in the method for preparing a U-type transformer oil base oil, the cycloalkyl distillate oil includes a cycloalkyl normal second-line distillate oil and / or a mixed oil of a cycloalkyl normal second-line distillate oil and a cycloalkyl minus first-line distillate oil in a mass ratio of 1:1.

[0063] In some embodiments of the present invention, in step S1, in the method for preparing Class I transformer oil base oil, the cycloalkyl distillate oil includes cycloalkyl minus first-line distillate oil and / or a mixed oil of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil in a mass ratio of 1:1.

[0064] In some embodiments of the present invention, in step S1, the hydroprocessing is carried out under the action of a hydroprocessing catalyst, and the hydroprocessing catalyst adopts a non-precious metal catalyst produced by patent application number 201611160651.2.

[0065] In some embodiments of the present invention, in step S1, the hydroprocessing catalyst comprises an active metal oxide and a metal oxide promoter; the active metal oxide comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the active metal oxide comprises nickel oxide and / or tungsten trioxide.

[0066] In some embodiments of the present invention, in step S1, the pressure of the hydrotreatment is 8.0-10.0 MPa; typically but not limitatively, for example, in step S1, the pressure of the hydrotreatment can be 8.0 MPa, 8.5 MPa, 9.0 MPa, 9.5 MPa, 10.0 MPa or a range of any two thereof.

[0067] In some embodiments of the present invention, in step S1, the temperature of the hydrotreatment is 300-370°C; typically but not limitatively, for example, in step S1, the temperature of the hydrotreatment can be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C or a range consisting of any two of them.

[0068] In some embodiments of the present invention, in step S1, in the method for preparing a U-type transformer oil base oil, the temperature of the hydrogenation treatment is 340-350° C. (eg, 340° C., 345° C., etc.).

[0069] In some embodiments of the present invention, in step S1, in the method for preparing a Class I transformer oil base oil, the temperature of the hydrogenation treatment is 340-360° C. (eg, 345° C., 350° C., 355° C., etc.).

[0070] In some embodiments of the present invention, in step S1, the volume space velocity of the hydroprocessing is 0.2 to 1.0 h -1 Typically, but not limiting, for example, in step S1, the volume space velocity of the hydroprocessing may be 0.2h -1 、0.3h -1 、0.4h -1 , 0.5h -1 、0.6h -1 、0.7h -1 , 0.8h -1 , 0.9h -1 , 1.0h -1 Or a range of values ​​consisting of any two of them.

[0071] In some embodiments of the present invention, in step S1, the volume ratio of hydrogen to cycloalkyl distillate oil is (800-1200):1; typically but not limitatively, for example, in step S1, the volume ratio of hydrogen to cycloalkyl distillate oil can be 800:1, 900:1, 1000:1, 1100:1, 1200:1 or a range of any two thereof.

[0072] In some embodiments of the present invention, in step S2, the hydrodecondensation treatment is carried out under the action of a hydrodecondensation catalyst, and the hydrodecondensation catalyst is a non-precious metal catalyst produced by patent application number 201910897903.7.

[0073] In some embodiments of the present invention, in step S2, the hydrodecondensation catalyst comprises an active metal oxide; the active metal oxide comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the active metal oxide comprises nickel oxide and / or tungsten trioxide.

[0074] The hydrodegradation catalyst selectively removes large molecular normal alkanes with high freezing points, thereby reducing the pour point of the hydrotreated oil.

[0075] In some embodiments of the present invention, in step S2, the pressure of the hydrodecondensation treatment is 8.0-10.0 MPa; typically but not limitatively, for example, in step S2, the pressure of the hydrodecondensation treatment can be 8.0 MPa, 8.5 MPa, 9.0 MPa, 9.5 MPa, 10.0 MPa or a range of any two thereof.

[0076] In some embodiments of the present invention, in step S2, the temperature of the hydrodecondensation treatment is 280-340°C; typically but not limitatively, for example, in step S2, the temperature of the hydrodecondensation treatment can be 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C or a range consisting of any two of them.

[0077] In some embodiments of the present invention, in step S2, the volumetric space velocity of the hydrodecondensation treatment is 0.8 to 3.0 h -1 Typically, but not limiting, for example, in step S1, the volumetric space velocity of the hydrodecondensation treatment may be 0.8 h -1 , 1.0h -1 , 1.2h -1 , 1.4h -1 , 1.6h -1 , 1.8h -1 , 2.0h -1 , 2.2h -1 , 2.4h -1 , 2.4h -1, 2.6h -1 , 2.8h -1 , 3.0h -1 Or a range of values ​​consisting of any two of them.

[0078] In some embodiments of the present invention, in step S2, the volume ratio of hydrogen to hydrotreated oil is (800-1200):1; typically but not limiting, for example, the volume ratio of hydrogen to hydrotreated oil can be 800:1, 900:1, 1000:1, 1100:1, 1200:1 or a range of any two thereof.

[0079] In some embodiments of the present invention, in step S3, the supplementary refining treatment is carried out under the action of a supplementary refining catalyst, and the supplementary refining catalyst is a non-precious metal catalyst produced by patent application number 201910952953.0.

[0080] In some embodiments of the present invention, in step S3, the supplementary refined catalyst comprises an active metal oxide; the active metal oxide comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the active metal oxide comprises at least one of nickel oxide, tungsten trioxide and molybdenum trioxide;

[0081] In some embodiments of the present invention, in step S3, the pressure of the supplementary refining treatment is 8.0-10.0 MPa; typically but not limitatively, for example, in step S3, the pressure of the supplementary refining treatment can be 8.0 MPa, 8.5 MPa, 9.0 MPa, 9.5 MPa, 10.0 MPa or a range of any two thereof.

[0082] In some embodiments of the present invention, in step S3, the temperature of the supplementary refining treatment is 290-360°C; typically but not limitatively, for example, in step S3, the temperature of the supplementary refining treatment can be 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C or a range consisting of any two of them.

[0083] In some embodiments of the present invention, in step S3, the volumetric space velocity of the supplementary refining treatment is 0.3 to 2.0 h -1 Typically but not limiting, for example, in step S3, the volumetric space velocity of the supplementary refining treatment may be 0.3h -1 、0.4h -1 、0.6h -1 , 0.8h -1 , 1.0h -1 , 1.2h -1 , 1.4h -1 , 1.6h -1, 1.8h -1 , 2.0h -1 Or a range of values ​​consisting of any two of them.

[0084] In some embodiments of the present invention, in step S3, the volume ratio of hydrogen to the hydrodecomposition product oil is (800-1200):1; typically but not limiting, for example, the volume ratio of hydrogen to the hydrodecomposition product oil can be 800:1, 900:1, 1000:1, 1100:1, 1200:1 or a range value consisting of any two thereof.

[0085] In some embodiments of the present invention, in step S4, the pressure of gas-liquid separation is 6.0-10.0 MPa, and the temperature of gas-liquid separation is 100-220°C.

[0086] In some embodiments of the present invention, in step S4, the pressure of the vacuum distillation is 0.014-0.018 MPa, and the temperature of the vacuum distillation is 100-260°C.

[0087] In some embodiments of the present invention, in step S4, the side line with a temperature greater than 260° C. is extracted to obtain Class U transformer oil base oil; or, the side line with a temperature greater than 270° C. is extracted to obtain Class I transformer oil base oil.

[0088] The side line extraction temperature affects the flash point of the product. On the premise that the flash point meets the index requirements, the lower the extraction temperature, the higher the yield of the target product and the better the economic benefits. Due to the different raw materials and hydrogenation processes of Class U transformer oil base oil and Class I transformer oil base oil, the product composition of the hydrogenated oil is different. On the premise that the flash point meets the index requirements, the extraction temperature is different.

[0089] In some embodiments of the present invention, the U-type transformer oil base oil yield of the transformer oil base oil preparation method is greater than 90.0% (e.g., 91.0%, 92.0%, etc.), and the I-type transformer oil base oil yield is greater than 89.0% (e.g., 89.5%, 90.0%, etc.).

[0090] The preparation method of transformer oil base oil of the present invention uses cycloalkane distillate oil as raw material and non-precious metal catalyst under medium pressure (8.0-10.0MPa) conditions to directly generate U-type transformer oil base oil or I-type transformer oil base oil through hydrogenation treatment-hydrodecondensation-supplementary refining-fractionation process. The U-type transformer oil base oil or I-type transformer oil base oil can be produced by hydrogenation in the same device only by adjusting the raw material oil and the hydrogenation process. The method has the advantages of rich product types of the production device, small device investment scale, flexible device production, etc., and solves the problem of two sets of production devices and large investment.

[0091] The preparation method of transformer oil base oil of the present invention adopts a full hydrogenation process when processing cycloalkane distillate oil to produce U-type transformer oil base oil, adopts a selective hydrogenation treatment catalyst to remove tricyclic and higher aromatic hydrocarbons that are not conducive to oxidation stability while retaining monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons and natural antioxidant sulfides that are beneficial to oxidation stability, thereby improving the yield and oxidation stability of the U-type transformer oil base oil; and solves the problems of low product yield and generation of a large amount of low value-added by-products in the process of hydrodeacidification-furfural refining-clay refining.

[0092] The method for preparing transformer oil base oil of the present invention realizes a full hydrogenation process of transformer oil under medium pressure conditions by using different high-activity catalyst gradations, avoids the use of a high-pressure hydrogenation device to increase equipment investment and operation severity, and the transformer oil base oil produced under the medium pressure conditions retains a proper amount of aromatics and meets the requirements of Class U and Class I transformer oils in GB2536-2011; the transformer oil base oil prepared by the method has the characteristics of good low-temperature performance, solubility and oxidation stability, safe operation and low hydrogen consumption.

[0093] In some embodiments of the present invention, a transformer oil base oil is also provided, including a Class U transformer oil base oil or a Class I transformer oil base oil;

[0094] The U-type transformer oil base oil or the I-type transformer oil base oil is prepared by adopting the above-mentioned transformer oil base oil preparation method.

[0095] In some embodiments of the present invention, in the U-type transformer oil base oil, the sulfur content is >90.0 mg / kg (e.g., 100.0 mg / kg, 110.0 mg / kg, 120.0 mg / kg, etc.), and the nitrogen content is <40.0 mg / kg (e.g., 35.0 mg / kg, 30.0 mg / kg, 25.0 mg / kg, etc.);

[0096] The CA value of U-type transformer oil base oil is 4.5% to 5.5% (for example, 4.6%, 4.9%, 5.2%, etc.), the pour point is less than -57°C (for example, -59°C, -60°C, -61°C, etc.), and the kinematic viscosity at 40°C is less than 12.0 mm 2 / s (e.g., 11.0 mm 2 / s, 10.0mm 2 / s, 9.0mm 2 / s, etc.), closed cup flash point>140℃ (for example, 141℃, 142℃, 143℃, etc.);

[0097] The oxidation stability of U-type transformer oil base oil at 120°C and 164h is as follows: the total acid value is less than 0.27mgKOH / g (for example, 0.25mgKOH / g, 0.23mgKOH / g, etc.), the sludge is less than 0.0054% (for example, 0.0051%, 0.0048%, etc.), and the dielectric loss factor at 90°C is less than 0.082 (for example, 0.078, 0.074, etc.).

[0098] In some embodiments of the present invention, the sulfur content in the Class I transformer oil base oil is <10.0 mg / kg (e.g., 8.0 mg / kg, 6.0 mg / kg, 4.0 mg / kg, etc.), and the nitrogen content is <3.0 mg / kg (e.g., 2.0 mg / kg, 1.0 mg / kg, etc.);

[0099] The CA value of Class I transformer oil base oil is less than 4.7% (for example, 4.5%, 4.3%, 4.1%, etc.), the pour point is less than -57°C (for example, -59°C, -60°C, -61°C, etc.), and the kinematic viscosity at 40°C is less than 12.0 mm 2 / s (e.g., 11.5 mm 2 / s, 11.0mm 2 / s, 10.5mm 2 / s, etc.), closed cup flash point>140℃ (for example, 141℃, 142℃, 143℃, etc.).

[0100] In some embodiments of the present invention, a transformer oil is also provided, including Class U transformer oil or Class I transformer oil;

[0101] Class U transformer oil includes the above-mentioned Class U transformer oil base oil;

[0102] The Class I transformer oil comprises an antioxidant and the Class I transformer oil base oil, wherein the content of the antioxidant in the Class I transformer oil is 0.2wt%±0.05wt% (e.g., 0.22wt%, 0.24wt%, etc.);

[0103] The oxidation stability of Class I transformer oil at 120°C and 500h is as follows: total acid value <0.22mgKOH / g (for example, 0.19mgKOH / g, 0.16mgKOH / g, etc.), sludge <0.0038% (for example, 0.0035%, 0.0032%, etc.), and dielectric loss factor at 90°C <0.035 (for example, 0.031, 0.027, etc.).

[0104] In some embodiments of the present invention, the antioxidant includes 2,6-di-tert-butyl-p-cresol.

[0105] Preparation Example

[0106] The preparation method of the hydroprocessing catalyst comprises the following steps:

[0107] (a) adding 100 g of calcined silicon-phosphorus-containing alumina powder (the mass fraction of SiO2 is 3.3%, the mass fraction of P2O5 is 2.0%, and the balance is Al2O3) to 300 mL of water (the mass fraction of water in the obtained slurry is 75%), stirring for 5 min, and obtaining a slurry of silicon-phosphorus-containing alumina;

[0108] (b) adding 18.6 g of boric acid (based on the mass of B2O2, the amount of boric acid added is 4.6% of the mass of the prepared hydrorefining catalyst), 73 g of ammonium metatungstate (based on the mass of WO3, the amount of ammonium metatungstate added is 28.3% of the mass of the prepared hydrorefining catalyst) and 37 g of nickel nitrate (based on the mass of NiO, the amount of nickel nitrate added is 4.1% of the mass of the prepared hydrorefining catalyst) to the slurry containing silicon phosphorus alumina, stirring for 1 h, standing for 2 h and then filtering to obtain a wet filter cake and a filtrate;

[0109] (c) The filtrate is mixed with 55 g of SB powder (the amount added is 19% of the mass of the prepared hydrotreating catalyst) and 4 mL of concentrated nitric acid (3.6% of the mass of the silicon- and phosphorus-containing alumina powder) to prepare a binder for use; the wet filter cake is dried at 120° C. for 8 h, crushed into powder, and mixed with 4 g of sesbania powder (the amount added is 4% of the mass of the silicon- and phosphorus-containing alumina powder) and the above-mentioned binder, and then formed into strips after rolling and extrusion. The strips are then cured at room temperature for 4 h, dried at 120° C. for 4 h, and then calcined at 230° C. for 1 h, 350° C. for 1 h, and finally 480° C. for 4 h to obtain a hydrotreating catalyst.

[0110] The preparation method of the hydrodecondensation catalyst comprises the following steps:

[0111] (a) Weigh the pore volume of 1.095 mL / g and the specific surface area of ​​328 m2 produced by the aluminum sulfate method. 2 / g, 500g of pseudo-boehmite with a dry basis of 71%, 18.4g of nitric acid with a concentration of 65%, 10g of sesbania powder, 71g of carbon black, 60g of nickel nitrate additive and 754g of deionized water were added into a roller and rolled and mixed, extruded into cylindrical strips with an outer diameter of 6mm and an inner hollow diameter of 2.5mm, and dried under constant humidity and constant temperature conditions to a solid content of 65%; a punching device was used to punch evenly arranged circular through holes with a diameter of 1.5mm on the surface of the cylindrical strip, and particles with a length of 3-10mm were made, dried at 130°C for 8h, and then calcined at 900°C for 3h, A carrier support is obtained; 7.52 g of aluminum sulfate, 320 g of silica sol containing 30% silicon oxide, 2.15 g of sodium hydroxide, 1.81 g of triethylamine and 80 g of water are weighed respectively to prepare a ZSM-5 molecular sieve mother liquor; the prepared molecular sieve mother liquor is used to impregnate the above-mentioned carrier support, and the impregnated materials are placed on the upper part of the gas phase reactor, and deionized water is added to the bottom of the gas phase reactor. The reaction is carried out at 180°C for 36 hours. After the reaction is completed, the catalyst carrier containing the ZSM-5 molecular sieve membrane is obtained by washing with deionized water until it is neutral, drying at 130°C for 8 hours, and then calcining at 550°C for 3 hours.

[0112] (b) 30.3 g of nickel nitrate was weighed to prepare a solution containing 0.019 g / mL of nickel oxide and the solution was impregnated into the catalyst support. After the impregnation, the material was dried at 120° C. for 8 h and calcined at 450° C. for 3 h to obtain a hydrodecondensation catalyst.

[0113] The preparation method of the supplementary refined catalyst comprises the following steps:

[0114] (a) Weigh the pore volume of aluminum sulfate produced by 1.095 mL / g and the specific surface area of ​​328 m 2 500 g of pseudo-boehmite (71% on dry basis), 18.4 g of nitric acid (65%), 10 g of sesbania powder and 694 g of deionized water were added into a roller and rolled and mixed, and after extrusion, the mixture was dried at 120° C. for 10 h, and then calcined at 750° C. for 3 h to obtain a clover-shaped catalyst carrier for standby use;

[0115] (b) preparing 90 mL of a calcium nitrate solution containing 0.02 g / mL of calcium oxide, weighing 100 g of the above carrier and impregnating it, and then drying at 140° C. for 8 h to obtain carrier A for standby use;

[0116] (c) The catalyst composition is MoO322%, NiO3.5%, P2.0%, and a Mo-Ni-P solution is prepared based on the water absorption of the calcium-containing carrier, wherein the MoO3 concentration is 0.344 g / mL, the NiO concentration is 0.055 g / mL, and the P concentration is 0.031 g / mL; the volume ratio of the prepared catalyst Mo-Ni catalyst in the catalyst is 40%;

[0117] The catalyst composition is WO3 32%, NiO 5.5%, and a W-Ni solution is prepared according to the water absorption rate of the carrier, wherein the concentration of WO3 is 0.582 g / mL and the concentration of NiO is 0.1 g / mL; the volume ratio of the pre-prepared catalyst W-Ni series catalyst in the catalyst is 40%;

[0118] (d) 52.8 mL of the Mo-Ni-P solution was weighed, and after starting stirring, 26.5 g of isooctane, 5.0 g of polyoxyethylene glycol octylphenyl ether, and 8.0 g of n-pentanol were added respectively, and after mixing evenly, stirring was continued for 50 min to obtain a water-in-oil microemulsion;

[0119] (e) Weighing 100 g of the calcium-containing carrier, impregnating the carrier with 88 mL of the water-in-oil microemulsion, drying at 120° C. for 8 h, and then calcining at 450° C. for 3 h to obtain a catalyst semi-finished product;

[0120] (f) 52.8 mL of the W-Ni solution was taken to impregnate the semi-finished catalyst, dried at 120° C. for 10 h, and then calcined at 500° C. for 3 h to obtain a supplementary refined catalyst.

[0121] The parameters of the hydroprocessing catalyst, the hydrodegassing catalyst and the supplementary refining catalyst are shown in Table 1. The hydroprocessing catalyst, the hydrodegassing catalyst and the supplementary refining catalyst prepared in this preparation example are used in the examples.

[0122] Table 1

[0123] Hydroprocessing catalyst Hydrodecondensation catalyst Supplementary refining catalyst Appearance Shamrock Shamrock Shamrock <![CDATA[Pore volume (cm 3 ·g -1 )]]> ＞0.30 ＞0.18 ＞0.35 <![CDATA[Specific surface area (m 2 ·g -1 )]]> ＞200 ＞180 ＞150 <![CDATA[Bulk density (g·cm -3 )]]> 0.75～0.90 0.70～0.80 0.82～0.88 Diameter(mm) 1.3～1.6 1.3～1.6 1.0～1.4 <![CDATA[Crushing strength (N·mm -1 )]]> ＞10 ＞10 ＞15.0 <![CDATA[Mass fraction of WO3 (%)]]> 25.7 - 22.3 NiO mass fraction (%) 3.6 2.0 4.6 <![CDATA[Mass fraction of MoO3 / %]]> - - 7.5

[0124] Example 1

[0125] The preparation method of the U-type transformer oil provided in this embodiment comprises the following steps:

[0126] The cycloalkane second-line distillate oil is used as the feed oil. The feed oil is mixed with hydrogen and then passes through the hydrotreating catalyst of the first hydrogenation reactor, the hydrodecondensation catalyst of the second hydrogenation reactor, and the supplementary refining catalyst in sequence. The feed volume space velocity is 1.0h -1 , the hydrogen-oil volume ratio is 800:1, the system hydrogen partial pressure is 9.5MPa, wherein the loading volume ratio of the hydrotreating catalyst, the hydrodecondensation catalyst and the supplementary refining catalyst is 3:1:2, the average reaction temperatures are 340℃, 340℃ and 340℃ respectively, and the refined product oil is obtained;

[0127] The refined oil enters the stripping tower for gas-liquid separation (pressure is 6.0-10.0MPa, temperature is 100-220°C), and the liquid product enters the vacuum tower for vacuum fractionation (pressure is 0.014-0.018MPa, temperature is 100-260°C). The side line product with a temperature of >260°C is the U-type transformer oil base oil, and no additives are needed to obtain U-type transformer oil.

[0128] Example 2

[0129] The preparation method of the U-type transformer oil provided in this embodiment comprises the following steps:

[0130] The mixed oil of naphthenic second-line distillate oil and naphthenic first-line distillate oil with a mass ratio of 1:1 is used as the raw oil. The raw oil is mixed with hydrogen and then passes through the hydrotreating catalyst of the first hydrogenation reactor, the hydrodecondensation catalyst of the second hydrogenation reactor, and the supplementary refining catalyst in sequence. The feed volume space velocity is 1.0h -1 , the volume ratio of hydrogen to oil is 800:1, the system hydrogen partial pressure is 9.5MPa, wherein the loading volume ratio of the hydrotreating catalyst, the hydrodecondensation catalyst and the supplementary refining catalyst is 3:1:2, the average reaction temperatures are 345℃, 340℃ and 340℃ respectively, and the refined product oil is obtained;

[0131] The refined oil enters the stripping tower for gas-liquid separation (pressure is 6.0-10.0MPa, temperature is 100-220°C), and the liquid product enters the vacuum tower for vacuum fractionation (pressure is 0.014-0.018MPa, temperature is 100-260°C). The side line product with a temperature of >260°C is the U-type transformer oil base oil, and no additives are needed to obtain U-type transformer oil.

[0132] Example 3

[0133] The preparation method of type I transformer oil provided in this embodiment comprises the following steps:

[0134] The mixed oil of naphthenic second-line distillate oil and naphthenic first-line distillate oil with a mass ratio of 1:1 is used as the raw oil. The raw oil is mixed with hydrogen and then passes through the hydrotreating catalyst of the first hydrogenation reactor, the hydrodecondensation catalyst of the second hydrogenation reactor, and the supplementary refining catalyst in sequence. The feed volume space velocity is 1.0h -1 , the volume ratio of hydrogen to oil is 900:1, the system hydrogen partial pressure is 9.5MPa, wherein the loading volume ratio of the hydrotreating catalyst, the hydrodecondensation catalyst and the supplementary refining catalyst is 3:1:2, the average reaction temperatures are 345℃, 340℃ and 340℃ respectively, and the refined product oil is obtained;

[0135] The refined product oil enters the stripping tower liquid for gas-liquid separation (pressure is 6.0-10.0MPa, temperature is 100-220°C), and the liquid product enters the vacuum tower for vacuum fractionation (pressure is 0.014-0.018MPa, temperature is 100-260°C). The side line product with a temperature of more than 275°C is type I transformer oil base oil. 2,6-di-tert-butyl-p-cresol is added to the type I transformer oil base oil in an amount of 0.2wt%±0.05wt% to obtain type I transformer oil.

[0136] Example 4

[0137] The preparation method of type I transformer oil provided in this embodiment comprises the following steps:

[0138] The cycloalkyl minus first-line distillate was used as the feed oil. The feed oil was mixed with hydrogen and passed through the hydrotreating catalyst of the first hydrogenation reactor, the hydrodecondensation catalyst of the second hydrogenation reactor, and the supplementary refining catalyst in sequence. The feed volume space velocity was 1.0h -1 , the volume ratio of hydrogen to oil is 1000:1, the system hydrogen partial pressure is 9.5MPa, wherein the loading volume ratio of the hydrotreating catalyst, the hydrodecondensation catalyst and the supplementary refining catalyst is 3:1:2, the average reaction temperatures are 355°C, 340°C and 350°C respectively, and the refined product oil is obtained;

[0139] The refined product oil enters the stripping tower liquid for gas-liquid separation (pressure is 6.0-10.0MPa, temperature is 100-220°C), and the liquid product enters the vacuum tower for vacuum fractionation (pressure is 0.014-0.018MPa, temperature is 100-260°C). The side line product with a temperature of more than 270°C is type I transformer oil base oil. 2,6-di-tert-butyl-p-cresol is added to the type I transformer oil base oil in an amount of 0.2wt%±0.05wt% to obtain type I transformer oil.

[0140] Test example

[0141] The parameter of the stock oil of embodiment 1~4 is shown in Table 2; The parameter of the product (U type transformer oil base oil or I type transformer oil base oil) of embodiment 1~4 is shown in Table 3; The parameter of the U type transformer oil of embodiment 1~2 and the I type transformer oil of embodiment 3~4 is shown in Table 4.

[0142] Table 2

[0143]

[0144]

[0145] Table 3

[0146]

[0147]

[0148] Table 4

[0149]

[0150]

[0151] The U-type transformer oil base oil experiment was produced with the same raw materials, process flow and operating conditions as in Example 1. The device was operated continuously for 120 days, and the U-type transformer oil base oil was sampled and analyzed for aromatic content, pour point and yield every 48 hours. The periodic data were shown in Table 5.

[0152] Table 5

[0153]

[0154]

[0155] The U transformer oil base oil obtained by the preparation method of the invention has a pour point of -57°C and an aromatic content of 20-21% within a 300-2900h operation cycle, and has the advantages of low pour point, suitable aromatics, high yield, stable properties and the like.

[0156] The same raw materials, process flow and operating conditions as in Example 4 were used to produce a type I transformer oil base oil experiment. The device was operated continuously for 120 days, and the transformer oil was sampled and analyzed for aromatic content, pour point and yield every 48 hours. The periodic data were shown in Table 6.

[0157] Table 6

[0158]

[0159]

[0160] The I transformer oil base oil obtained by the preparation method of the present invention has a pour point of -57°C and an aromatic content of 16% to 17% within a 300-2900h operation cycle, and has the advantages of low pour point, appropriate aromatic content, high yield, stable properties and the like.

[0161] The main factor restricting the long-term operation of industrial devices is the rapid growth of the device pressure drop. In addition to the well-known raw material factors, the growth rate of the pressure drop is directly related to the porosity of the catalyst itself, the permeability of the bed, and the quality of logistics distribution. The three hydrogenation catalysts have high porosity and good permeability, which are conducive to the diffusion of reactants and products, reduce the pressure drop of the decondensation catalyst bed, and are conducive to the long-term operation of the device. In order to verify the stability of the catalyst of the present invention and facilitate the long-term operation of the device, the stability of the catalyst of the present invention was verified on a medium-sized hydrogenation test device similar to the process flow of the industrial device.

[0162] The experiment was carried out using Example 1 and Example 3. The device was operated continuously for 2600 hours. The static pressure drop at the inlet a of the first hydrogenation reactor R1 and the outlet b of the second hydrogenation reactor was measured at the 300th hour and the 2600th hour. The periodic data were shown in Table 7.

[0163] Table 7

[0164]

[0165]

[0166] As can be seen from Table 7, after the device continuously runs for 2600 hours, the total pressure drop increases by 0.03 MPa compared with running for 300 hours, which fully meets the index requirements of industrial devices. Therefore, the use of the three hydrogenation catalysts of the present invention is conducive to the diffusion of reactants and products, reduces the pressure drop of the catalyst bed, and is conducive to the long-term operation of the device.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a transformer oil base oil, characterized in that: The steps include: S1, mixing the cycloalkane fraction oil with hydrogen, and then performing a hydrogenation treatment to obtain a hydrogenation product oil; S2, mixing the hydrotreated product oil with hydrogen, and then performing a hydrodecondensation treatment to obtain a hydrodecondensation product oil; S3, mixing the hydrodecondensation product oil with hydrogen, and then performing additional refining treatment to obtain a refined product oil; S4, the refined product oil is subjected to gas-liquid separation to obtain a liquid product; the liquid product is subjected to vacuum fractionation, and a side line above 260° C. is produced to obtain a Class U transformer oil base oil or a Class I transformer oil base oil.

2. The method for preparing transformer oil base oil according to claim 1, characterized in that: In step S1, the naphthenic distillate oil includes naphthenic normal second-line distillate oil and / or naphthenic minus first-line distillate oil; Preferably, the cycloalkyl distillate oil comprises cycloalkyl normal second-line distillate oil and / or a mixed oil of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil in a mass ratio of 1:1; or, the cycloalkyl distillate oil comprises cycloalkyl minus first-line distillate oil and / or a mixed oil of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil in a mass ratio of 1:

1.

3. The method for preparing transformer oil base oil according to claim 1, characterized in that, In step S1, at least one of the following features (1) to (5) is included; (1) The hydroprocessing is carried out under the action of a hydroprocessing catalyst, wherein the hydroprocessing catalyst comprises a Group VIII metal oxide and / or a Group VIB metal oxide; (2) The pressure of the hydrotreatment is 8.0 to 10.0 MPa; (3) The temperature of the hydrotreatment is 300-370°C; (4) The volume space velocity of the hydroprocessing is 0.2 to 1.0 h -1 ; (5) The volume ratio of the hydrogen to the cycloalkane distillate oil is (800-1200):

1.

4. The method for preparing transformer oil base oil according to claim 3, characterized in that: In step S1, the hydroprocessing catalyst includes nickel oxide and / or tungsten trioxide; And / or, the temperature of the hydrotreatment is 340-350°C; or, the temperature of the hydrotreatment is 350-360°C.

5. The method for preparing transformer oil base oil according to claim 1, characterized in that, In step S2, at least one of the following features (1) to (5) is included; (1) The hydrodegradation treatment is carried out under the action of a hydrodegradation catalyst, wherein the hydrodegradation catalyst comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the hydrodegradation catalyst comprises nickel oxide and / or tungsten trioxide; (2) The pressure of the hydrodecondensation treatment is 8.0 to 10.0 MPa; (3) The temperature of the hydrodecondensation treatment is 280-340° C.; (4) The volumetric space velocity of the hydrodecondensation treatment is 0.8 to 3.0 h -1 ; (5) The volume ratio of the hydrogen to the hydroprocessed oil is (800-1200):

1.

6. The method for preparing transformer oil base oil according to claim 1, characterized in that: In step S3, at least one of the following features (1) to (5) is included; (1) The supplementary refining treatment is carried out under the action of a supplementary refining catalyst, and the supplementary refining catalyst comprises a Group VIII metal oxide and / or a Group VIB metal oxide; preferably, the supplementary refining catalyst comprises at least one of nickel oxide, tungsten trioxide and molybdenum trioxide; (2) The pressure of the supplementary refining treatment is 8.0 to 10.0 MPa; (3) The temperature of the supplementary refining treatment is 290 to 360° C.; (4) The volumetric space velocity of the supplementary refining treatment is 0.3 to 2.0 h -1 ; (5) The volume ratio of the hydrogen to the hydrodegradation oil is (800-1200):

1.

7. A transformer oil base oil, characterized in that: Including Class U transformer oil base oil or Class I transformer oil base oil; The U-type transformer oil base oil or the I-type transformer oil base oil is prepared by the preparation method of the transformer oil base oil according to any one of claims 1 to 6.

8. The transformer oil base oil according to claim 7, characterized in that The U-type transformer oil base oil has a sulfur content of >90.0 mg / kg and a nitrogen content of <40.0 mg / kg; the U-type transformer oil base oil has a CA value of 4.5% to 5.5%, a pour point of <-57°C, and a kinematic viscosity of <12.0 mm at 40°C. 2 / s, closed cup flash point>140℃; the oxidation stability of the U-type transformer oil base oil at 120℃, 164h, total acid value<0.27mgKOH / g, oil sludge<0.0054%, and dielectric loss factor<0.082 at 90℃.

9. The transformer oil base oil according to claim 7, characterized in that: The sulfur content of the Class I transformer oil base oil is less than 10.0 mg / kg, and the nitrogen content is less than 3.0 mg / kg; the CA value of the Class I transformer oil base oil is less than 4.7%, the pour point is less than -57°C, and the kinematic viscosity at 40°C is less than 12.0 mm 2 / s, closed cup flash point>140℃.

10. A transformer oil, characterized in that: Including Class U transformer oil or Class I transformer oil; The U-type transformer oil comprises the U-type transformer oil base oil according to claim 7 or 8; The Class I transformer oil comprises an antioxidant and the Class I transformer oil base oil according to claim 7 or 9, wherein the content of the antioxidant in the Class I transformer oil is 0.2wt%±0.05wt%; the oxidation stability of the Class I transformer oil at 120°C and 500h is as follows: the total acid value is less than 0.22mgKOH / g, the sludge is less than 0.0038%, and the dielectric loss factor at 90°C is less than 0.035.

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