Process for producing transformer base oil, transformer base oil and transformer oil

Abstract

This invention provides a production process for transformer base oil, transformer base oil, and transformer oil, specifically relating to the field of mineral oil production technology. The production process involves mixing coking diesel and hydrogen for a first hydrotreating treatment to obtain a hydrotreated pre-treated oil; then mixing the hydrotreated pre-treated oil and hydrogen for a second hydrotreating treatment to obtain a hydrodepletion-depleted oil; finally, refining, gas-liquid separation, and fractionation of the hydrodepletion-depleted oil to obtain the transformer base oil. This production process couples full-volume feedstock with two-stage hydrotreating, overcoming blending limitations and achieving deep conversion of coking diesel; hydrodepletion selectively cracks long-chain wax components while retaining the naphthenic structure, significantly lowering the pour point, while avoiding excessive ring-opening that leads to reduced product yield and deterioration of oxidation stability; the three-stage post-treatment of refining, gas-liquid separation, and fractionation precisely removes H2S, NH3, etc., ensuring that the final base oil meets core performance indicators.

Description

Technical Field

[0001] This invention relates to the technical field of mineral oil production, and in particular to a production process for transformer base oil, transformer base oil, and transformer oil. Background Technology

[0002] On the one hand, high-quality naphthenic crude oil, as the core raw material for traditional transformer oil base oil, is becoming increasingly scarce and has a high import dependence, posing a severe challenge to the resilience of the supply chain. On the other hand, refineries are facing increasing pressure in the efficient conversion of heavy and inferior raw materials: in particular, by-product fractions, represented by coking diesel, have long been limited by their strong toxicity and inertness, making it difficult to achieve large-scale utilization of the entire fraction.

[0003] While existing processes attempt to couple hydrodewaxing, they rely on ultra-high pressure conditions, resulting in high equipment investment and operating energy consumption. On the other hand, coal tar-based routes are limited by unstable raw material quality and improper catalyst gradation, leading to insufficient deep removal of aromatics and making it difficult to meet the stringent requirements for transformer oil base oil.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a production process for transformer base oil, transformer base oil, and transformer oil, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The first aspect of the present invention provides a production process for transformer base oil, comprising mixing coking diesel and hydrogen for a first hydrotreating process to obtain a hydrotreating pretreated oil; then mixing the hydrotreating pretreated oil and hydrogen for a second hydrotreating process to obtain a hydrodepowdering product oil; and finally refining, gas-liquid separation and fractionation of the hydrodepowdering product oil to obtain the transformer base oil.

[0007] Furthermore, the pressure of the first hydrogenation treatment is 7~10 MPa, the temperature is 300~370℃, and the volume hourly space velocity is 0.2~1.0 h⁻¹. -1 .

[0008] Preferably, the volume ratio of the coking diesel to the hydrogen is 1:(400~600).

[0009] Preferably, the catalyst used in the first hydrogenation treatment includes at least one of tungsten-nickel type hydrogenation catalyst, molybdenum-nickel type hydrogenation catalyst and molybdenum-tungsten-nickel type hydrogenation catalyst, and is preferably a tungsten-nickel type hydrogenation catalyst.

[0010] Furthermore, the second hydrogenation treatment is carried out at a pressure of 7-10 MPa, a temperature of 260-350 °C, and a volumetric hourly space velocity of 0.3-2.0 h⁻¹. -1 .

[0011] Preferably, the volume ratio of the hydrotreated oil to the hydrogen is 1:(400~600).

[0012] Preferably, the catalyst used in the second hydrogenation treatment includes at least one of nickel-type hydrogenation catalyst, molybdenum-type hydrogenation catalyst, and tungsten-type hydrogenation catalyst, and is preferably a nickel-type hydrogenation catalyst.

[0013] Preferably, the catalyst used in the second hydrogenation treatment is subjected to nitrogen-resistant treatment before use.

[0014] Preferably, the nitrogen-resistant treatment involves hydrothermal treatment of the catalyst.

[0015] Preferably, the hydrothermal treatment is performed at a pressure of 0.1~0.5MPa, a temperature of 500~700℃, and a time of 2~8h.

[0016] Furthermore, the refining process involves mixing the hydrodecondensate-generated oil with hydrogen and performing a third hydrotreating process to obtain refined oil.

[0017] Preferably, the third hydrogenation treatment is performed at a pressure of 7-11 MPa, a temperature of 260-350°C, and a volume hourly space velocity of 0.3-2.0 h⁻¹. -1 .

[0018] Preferably, the volume ratio of the hydrodecondensing oil to hydrogen is 1:(400~600).

[0019] Preferably, the catalyst used in the third hydrogenation process includes at least one of a molybdenum-tungsten-nickel type hydrogenation catalyst, a molybdenum-nickel type hydrogenation catalyst, and a tungsten-nickel type hydrogenation catalyst, and is preferably a molybdenum-tungsten-nickel type hydrogenation catalyst.

[0020] Furthermore, the gas-liquid separation is carried out in a stripping tower.

[0021] Preferably, the top pressure of the stripping tower is 0.3~0.6MPa and the temperature is 100~150℃.

[0022] Preferably, the bottom temperature of the stripping tower is 190~230℃.

[0023] Preferably, the feed temperature of the stripping tower is 190~220℃.

[0024] Furthermore, the fractionation is carried out within a fractionation column.

[0025] Preferably, the fractionation is vacuum fractionation.

[0026] Preferably, the top pressure of the fractionation column is 0.07~0.09MPa and the temperature is 50~70℃.

[0027] Preferably, the bottom temperature of the fractionation column is 270~310℃.

[0028] Preferably, the feed temperature of the fractionation tower is 220~240℃.

[0029] Furthermore, the coking diesel contains 30-50 wt% aromatics, 7000-12000 ppm sulfur, and 2000-5000 ppm nitrogen.

[0030] Preferably, the pour point of the coking diesel is -10 to 10°C.

[0031] The second aspect of the present invention provides a transformer base oil, which is prepared using the production process described in the first aspect.

[0032] Furthermore, the transformer base oil has a pour point < -60℃, a sulfur content < 1.0 ppm by mass, a nitrogen content < 1.0 ppm by mass, and a kinematic viscosity < 2100 mmHg at -40℃. 2 / s.

[0033] Preferably, the transformer base oil has a CA value of <3% and a CN value of >55%.

[0034] The third aspect of the present invention provides a transformer oil comprising 0.25~0.35wt% antioxidant, with the balance being the transformer base oil described in the second aspect; The antioxidants include aromatic amine antioxidants and / or hindered phenolic antioxidants.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects: The production process provided by this invention, with full-volume feeding coupled with two-stage hydrotreating, overcomes the limitations of blending and achieves deep conversion of coking diesel. Hydrodewaxing selectively cracks long-chain wax components while preserving the naphthenic structure, significantly lowering the pour point, while avoiding excessive ring-opening that leads to reduced product yield and deterioration of oxidation stability. Three-stage post-treatment—refining, gas-liquid separation, and fractionation—precisely removes H2S, NH3, etc., ensuring that the final base oil meets the core indicators of GB 2536-2011. The entire process requires no upgrades to high-pressure equipment or additional reboilers, combining industrial feasibility and economic viability.

[0036] The transformer base oil provided by this invention, given the advantages of the above-mentioned production process, produces transformer oil base oil with excellent comprehensive performance, stable and compliant performance indicators, and a balance between product quality and economic benefits, making it highly practical and valuable for promotion.

[0037] The transformer oil provided by this invention reduces the cost of transformer oil and also lowers the operation and maintenance costs of transformers. Timely oil changes ensure stable and long-term operation of transformers and improve the overall service life of transformers. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0040] The first aspect of the present invention provides a production process for transformer base oil, comprising mixing coking diesel and hydrogen for a first hydrotreating process to obtain a hydrotreating pretreated oil; then mixing the hydrotreating pretreated oil and hydrogen for a second hydrotreating process to obtain a hydrodepowdering product oil; and finally refining, gas-liquid separation and fractionation of the hydrodepowdering product oil to obtain the transformer base oil.

[0041] The production process provided by this invention, with full-volume feeding coupled with two-stage hydrotreating, overcomes the limitations of blending and achieves deep conversion of coking diesel. Hydrodewaxing selectively cracks long-chain wax components while preserving the naphthenic structure, significantly lowering the pour point, while avoiding excessive ring-opening that leads to reduced product yield and deterioration of oxidation stability. Three-stage post-treatment—refining, gas-liquid separation, and fractionation—precisely removes H2S, NH3, etc., ensuring that the final base oil meets the core indicators of GB 2536-2011. The entire process requires no upgrades to high-pressure equipment or additional reboilers, combining industrial feasibility and economic viability.

[0042] Furthermore, the pressure of the first hydrogenation treatment is 7~10 MPa, the temperature is 300~370℃, and the volume hourly space velocity is 0.2~1.0 h⁻¹. -1 .

[0043] Typically, but not limitingly, the pressure of the first hydrogenation treatment can be, for example, 7 MPa, 8 MPa, 9 MPa, or 10 MPa, or any value within the range of 7 MPa to 10 MPa; the temperature can be, for example, 300°C, 320°C, 340°C, 350°C, 360°C, or 370°C, or any value within the range of 300°C to 370°C; and the volumetric hourly space velocity can be, for example, 0.2 h⁻¹. -1 0.4h -1 0.6h -1 0.8h -1 or 1.0h -1 It can also be 0.2h -1 ~1.0h -1 Any value within the range.

[0044] Preferably, the volume ratio of the coking diesel to the hydrogen is 1:(400~600).

[0045] Typically, but not limitingly, the volume ratio of the coking diesel to the hydrogen can be, for example, 1:400, 1:450, 1:500, 1:550 or 1:600, or any ratio in the range of 1:(400~600).

[0046] Preferably, the catalyst used in the first hydrogenation treatment includes at least one of tungsten-nickel type hydrogenation catalyst, molybdenum-nickel type hydrogenation catalyst and molybdenum-tungsten-nickel type hydrogenation catalyst, and is preferably a tungsten-nickel type hydrogenation catalyst.

[0047] Furthermore, the second hydrogenation treatment is carried out at a pressure of 7-10 MPa, a temperature of 260-350 °C, and a volumetric hourly space velocity of 0.3-2.0 h⁻¹. -1 .

[0048] Typically, but not limitingly, the pressure of the second hydrogenation treatment can be, for example, 7 MPa, 8 MPa, 9 MPa, or 10 MPa, or any value within the range of 7 MPa to 10 MPa; the temperature can be, for example, 260°C, 280°C, 300°C, 320°C, 340°C, or 350°C, or any value within the range of 260°C to 350°C; and the volumetric hourly space velocity can be, for example, 0.3 h⁻¹. -1 0.6h -1 1.0h -1 1.5h -1 or 2.0h -1 It can also be 0.3h -1 ~2.0h -1 Any value within the range.

[0049] Preferably, the volume ratio of the hydrotreated oil to the hydrogen is 1:(400~600).

[0050] Typically, but not limitingly, the volume ratio of the hydrotreated oil to the hydrogen can be, for example, 1:400, 1:450, 1:500, 1:550 or 1:600, or any ratio in the range of 1:(400~600).

[0051] Preferably, the catalyst used in the second hydrogenation treatment includes at least one of nickel-type hydrogenation catalyst, molybdenum-type hydrogenation catalyst, and tungsten-type hydrogenation catalyst, and is preferably a nickel-type hydrogenation catalyst.

[0052] Preferably, the catalyst used in the second hydrogenation treatment is subjected to nitrogen-resistant treatment before use.

[0053] Preferably, the nitrogen-resistant treatment involves hydrothermal treatment of the catalyst.

[0054] Preferably, the hydrothermal treatment is performed at a pressure of 0.1~0.5MPa, a temperature of 500~700℃, and a time of 2~8h.

[0055] Typically, but not limitingly, the pressure of the hydrothermal treatment can be, for example, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, or 0.5 MPa, or any value within the range of 0.1 MPa to 0.5 MPa; the temperature can be, for example, 500°C, 550°C, 600°C, 650°C, or 700°C, or any value within the range of 500°C to 700°C; the time can be, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h, or any value within the range of 2 h to 8 h.

[0056] Furthermore, the refining process involves mixing the hydrodecondensate-generated oil with hydrogen and performing a third hydrotreating process to obtain refined oil.

[0057] Preferably, the third hydrogenation treatment is performed at a pressure of 7-11 MPa, a temperature of 260-350°C, and a volume hourly space velocity of 0.3-2.0 h⁻¹. -1 .

[0058] Typically, but not limitingly, the pressure of the third hydrogenation treatment can be, for example, 7 MPa, 8 MPa, 9 MPa, 10 MPa, or 11 MPa, or any value within the range of 7 MPa to 11 MPa; the temperature can be, for example, 260°C, 280°C, 300°C, 320°C, 340°C, or 350°C, or any value within the range of 260°C to 350°C; and the volumetric hourly space velocity can be, for example, 0.3 h⁻¹. -1 0.6h -1 1.0h -1 1.5h -1 or 2.0h -1 It can also be 0.3h -1~2.0h -1 Any value within the range.

[0059] Preferably, the volume ratio of the hydrodecondensing oil to hydrogen is 1:(400~600).

[0060] Typically, but not limitingly, the volume ratio of the hydrodewaxing product oil to hydrogen can be, for example, 1:400, 1:450, 1:500, 1:550 or 1:600, or any ratio in the range of 1:(400~600).

[0061] Preferably, the catalyst used in the third hydrogenation process includes at least one of a molybdenum-tungsten-nickel type hydrogenation catalyst, a molybdenum-nickel type hydrogenation catalyst, and a tungsten-nickel type hydrogenation catalyst, and is preferably a molybdenum-tungsten-nickel type hydrogenation catalyst.

[0062] Furthermore, the gas-liquid separation is carried out in a stripping tower.

[0063] Preferably, the top pressure of the stripping tower is 0.3~0.6MPa and the temperature is 100~150℃.

[0064] Typically, but not limitingly, the top pressure of the stripping tower can be, for example, 0.3 MPa, 0.4 MPa, 0.5 MPa, or 0.6 MPa, or any value within the range of 0.3 MPa to 0.6 MPa; the temperature can be, for example, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, or any value within the range of 100°C to 150°C.

[0065] Preferably, the bottom temperature of the stripping tower is 190~230℃.

[0066] Typically, but not limitingly, the bottom temperature of the stripping tower can be, for example, 190°C, 200°C, 210°C, 220°C or 230°C, or any value within the range of 190°C to 230°C.

[0067] Preferably, the feed temperature of the stripping tower is 190~220℃.

[0068] Typically, but not limitingly, the feed temperature of the stripping tower can be, for example, 190°C, 200°C, 210°C, or 220°C, or any value within the range of 190°C to 220°C.

[0069] Furthermore, the fractionation is carried out within a fractionation column.

[0070] Preferably, the fractionation is vacuum fractionation.

[0071] Preferably, the top pressure of the fractionation column is 0.07~0.09MPa and the temperature is 50~70℃.

[0072] Typically, but not limitingly, the top pressure of the fractionation column can be, for example, 0.07 MPa, 0.08 MPa, or 0.09 MPa, or any value within the range of 0.07 MPa to 0.09 MPa; the temperature can be, for example, 50°C, 55°C, 60°C, 65°C, or 70°C, or any value within the range of 50°C to 70°C.

[0073] Preferably, the bottom temperature of the fractionation column is 270~310℃.

[0074] Typically, but not limitingly, the bottom temperature of the fractionation column can be, for example, 270°C, 280°C, 290°C, 300°C, or 310°C, or any value within the range of 270°C to 310°C.

[0075] Preferably, the feed temperature of the fractionation tower is 220~240℃.

[0076] Typically, but not limitingly, the feed temperature of the fractionation column can be, for example, 220°C, 225°C, 230°C, 235°C, or 240°C, or any value within the range of 220°C to 240°C.

[0077] Furthermore, the coking diesel contains 30-50 wt% aromatics, 7000-12000 ppm sulfur, and 2000-5000 ppm nitrogen.

[0078] Typically, but not limitingly, the aromatic hydrocarbon content in the coking diesel oil can be, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%, or any value within the range of 30 wt% to 50 wt%; the sulfur content can be, for example, 7000 ppm, 8000 ppm, 9000 ppm, 10000 ppm, 11000 ppm, or 12000 ppm, or any value within the range of 7000 ppm to 12000 ppm; and the nitrogen content can be, for example, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, or 5000 ppm, or any value within the range of 2000 ppm to 5000 ppm.

[0079] Preferably, the pour point of the coking diesel is -10 to 10°C.

[0080] Typically, but not limitingly, the pour point of the coking diesel oil can be, for example, -10°C, -5°C, 0°C, 5°C, or 10°C, or any value within the range of -10°C to 10°C.

[0081] In the first hydrotreating reaction, high-sulfur, high-nitrogen, and high-aromatic coking diesel is used as feedstock and undergoes deep hydrotreating pretreatment under the action of tungsten-nickel type hydrotreating catalysts. The main processes include hydrodesulfurization, hydrodenitrogenation, and partial hydrosaturation of aromatics and olefins. Specifically, thiophene and benzothiophene sulfur-containing compounds are converted into H2S and hydrocarbons, while quinoline and indole nitrogen-containing compounds are converted into NH3 and hydrocarbons. Simultaneously, some polycyclic aromatic hydrocarbons undergo ring-by-ring hydrosaturation, reducing the risk of poisoning in subsequent reaction systems. This step is not primarily cracking-based, but rather enhances the feedstock reactivity and protects the downstream hydrodewaxing catalyst through appropriate saturation and heteroatom removal, laying the foundation for subsequent selective dewaxing.

[0082] The second hydrotreating process, catalyzed by a nickel-based hydrodewaxing catalyst, aims to selectively crack long-chain n-alkanes and isoalkanes with long side chains without destroying the cycloalkane core structure. The reaction is essentially a β-cleavage-dominated hydrocracking process catalyzed by a weak acid center: acidic sites on the catalyst surface cause C / C bond cleavage of long-chain alkyl side chains at the cycloalkane ring junctions, generating small-molecule isoalkanes and light gases. Hydrogen simultaneously participates in the saturated cracking products, inhibiting coking and maintaining product saturation. Due to the relatively mild reaction temperature and the catalyst's nitrogen-resistant treatment enhancing its tolerance to nitrogen-containing impurities, ring-opening or deep aromatization of cycloalkane rings is effectively avoided. This significantly lowers the pour point while maximally preserving the cycloalkane structure, ensuring product yield and oxidation stability.

[0083] The refining process employs a molybdenum-tungsten-nickel catalyst to deeply hydrotreat the hydrodepressed oil. The main reactions include: deep hydrodesulfurization of trace amounts of stubborn sulfides such as thiophenes and benzothiophenes; hydrodenitrification of nitrogen-containing basic impurities; and complete saturation of trace unsaturated olefins and dienes, while some mono- and dicyclic aromatics undergo hydrosaturation. Particularly noteworthy is that this step also serves a hydrostabilization function: completely saturating the small amount of olefin intermediates that may be generated during hydrodepressing, eliminating potential oxidation initiation sources, and synergistically improving the oil's color stability and long-term storage stability.

[0084] The gas-liquid separation process is completed in a stripping tower, using hydrogen as the stripping medium. Under high temperature and low pressure conditions, H2S, NH3, light hydrocarbons, moisture, and residual hydrogen generated in the preceding hydrogenation reaction and dissolved in the oil phase are efficiently blown out and removed from the liquid phase. The stripping tower achieves efficient separation of the gas and liquid phases by controlling the reflux ratio at the top and the reboil rate at the bottom. This step directly determines the cleanliness of the subsequent fractionation feed, preventing H2S and NH3 from corroding equipment or contaminating the product in the high-temperature fractionation section.

[0085] Fractionation is carried out in a vacuum fractionation tower, where the boiling point of the oil is lowered under vacuum to prevent the cracking or condensation of cycloalkanes caused by high temperatures. The refined oil after stripping is precisely segmented according to its distillation range: light fractions (<280℃ fractions) are removed to control flash point and volatility, while the target narrow fraction above 280℃ is retained as a component of the transformer base oil; this fraction is rich in cycloalkanes and isoalkanes, exhibiting excellent low-temperature fluidity, high dielectric strength, and oxidation stability. Precise temperature and pressure control during vacuum fractionation ensures the product's kinematic viscosity and Cg. A / C N The carbon form distribution is stable and controllable.

[0086] The second aspect of the present invention provides a transformer base oil, which is prepared using the production process described in the first aspect.

[0087] The transformer base oil provided by this invention, given the advantages of the above-mentioned production process, produces transformer oil base oil with excellent comprehensive performance, stable and compliant performance indicators, and a balance between product quality and economic benefits, making it highly practical and valuable for promotion.

[0088] Furthermore, the transformer base oil has a pour point < -60℃, a sulfur content < 1.0 ppm by mass, a nitrogen content < 1.0 ppm by mass, and a kinematic viscosity < 2100 mmHg at -40℃. 2 / s.

[0089] Preferably, the transformer base oil has a CA value of <3% and a CN value of >55%.

[0090] The third aspect of the present invention provides a transformer oil comprising 0.25~0.35wt% antioxidant, with the balance being the transformer base oil described in the second aspect; The antioxidants include aromatic amine antioxidants and / or hindered phenolic antioxidants.

[0091] Typically, but not limitingly, the antioxidant content may be, for example, 0.25 wt%, 0.28 wt%, 0.30 wt%, 0.32 wt%, or 0.35 wt%, or any value within the range of 0.25 wt% to 0.35 wt%, and the remaining components are the transformer oil base oil described in the second aspect above.

[0092] The transformer oil provided by this invention reduces the cost of transformer oil and also lowers the operation and maintenance costs of transformers. Timely oil changes ensure stable and long-term operation of transformers and improve the overall service life of transformers.

[0093] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0094] The physicochemical properties of the coking diesel used in the following examples and comparative examples are shown in Table 1.

[0095] Table 1

[0096] Tungsten-nickel type hydrogenation catalyst: purchased from CNOOC Chemical and New Materials Research Institute, grade ZQC-25 hydrogenation treatment catalyst; Molybdenum-nickel type hydrogenation catalyst: purchased from CNOOC Chemical and New Materials Research Institute, grade ZQC-26 hydrogenation treatment catalyst; Molybdenum-cobalt type hydrogenation catalyst: purchased from CNOOC Chemical and New Materials Research Institute, grade ZQC-27 hydrogenation treatment catalyst; Nickel type hydrogenation catalyst: purchased from CNOOC Chemical and New Materials Research Institute, grade LC-1 hydrodewaxing catalyst; Molybdenum-tungsten-nickel type hydrogenation catalyst: purchased from CNOOC Chemical and New Materials Research Institute, grade LR-1 supplementary refining catalyst.

[0097] Example 1 This embodiment provides a transformer oil, using Daxie Petrochemical Phase I coking diesel as the feedstock. The specific preparation process is as follows: 1. The above-mentioned coking diesel feedstock and hydrogen are mixed at a hydrogen-to-oil volume ratio of 800:1 and then sequentially fed into a series three-stage fixed-bed reaction system: 1.1. The catalyst enters the first hydrogenation reactor, which is packed with ZQC-25 hydrogenation catalyst; reaction conditions: pressure 10.0 MPa, average temperature 350℃, volumetric hourly space velocity (LHSV) 0.6 h⁻¹. -1 .

[0098] 1.2 The effluent from the first hydrogenation reactor enters the second hydrogenation reactor, which is packed with LC-1 hydrodewaxing catalyst (pretreated with nitrogen-resistant hydrothermal treatment: 0.3 MPa, 620℃, 4 h); reaction conditions: pressure 10.0 MPa, average temperature 335℃, volumetric hourly space velocity 0.8 h⁻¹. -1 .

[0099] 1.3. Continue into the third hydrogenation reactor, which is loaded with LR-1 supplemental refining catalyst; reaction conditions: pressure 10.0 MPa, average temperature 330℃, volume hourly space velocity 0.9 h⁻¹. -1 .

[0100] 2. After being cooled by heat exchange, the reaction effluent enters the stripping tower for gas-liquid separation: tower top operating pressure: 0.45MPa, temperature: 125℃; tower bottom temperature: 210℃, feed temperature: 205℃.

[0101] 3. The bottom liquid phase of the stripping tower is fed into the vacuum fractionation tower: absolute pressure 0.08MPa; tower top temperature: 62℃, tower bottom temperature: 290℃, feed temperature: 230℃, and the fraction with a temperature >280℃ is taken as the target product: transformer oil base oil.

[0102] 4. Take the base oil obtained above, add 0.30wt% of 2,6-di-tert-butyl-p-cresol (BHT), and stir evenly at 60℃ for 30 minutes to obtain the finished transformer oil.

[0103] Example 2 This embodiment provides a transformer oil that differs from Embodiment 1 in that it uses Daxie Petrochemical Phase II coking diesel oil as the raw material, and the reaction temperature in step 1.2 is 340°C. The remaining steps are the same as in Embodiment 1 and will not be repeated here.

[0104] Example 3 This embodiment provides a transformer oil. The difference from Embodiment 1 is that the ZQC-25 hydrotreating catalyst in step 1.1 is replaced with the ZQC-26 hydrotreating catalyst. The remaining steps are the same as in Embodiment 1 and will not be repeated here.

[0105] Example 4 This embodiment provides a transformer oil. The difference from Embodiment 1 is that the ZQC-25 hydrotreating catalyst in step 1.1 is replaced with the ZQC-27 hydrotreating catalyst. The remaining steps are the same as in Embodiment 1 and will not be repeated here.

[0106] Example 5 This embodiment provides a transformer oil. Unlike embodiment 1, the hydrogen dewaxing catalyst in step 1.2 is not subjected to nitrogen-resistant treatment. The remaining steps are the same as in embodiment 1 and will not be repeated here.

[0107] Example 6 This embodiment provides a transformer oil. The difference from Embodiment 1 is that the reaction conditions in step 1.1 are: pressure 6MPa. The remaining steps are the same as in Embodiment 1, and will not be repeated here.

[0108] Example 7 This embodiment provides a transformer oil. The difference from Embodiment 1 is that the reaction conditions in step 1.1 are: pressure 7MPa. The remaining steps are the same as in Embodiment 1, and will not be repeated here.

[0109] Example 8 This embodiment provides a transformer oil. The difference from Embodiment 1 is that the reaction conditions in step 1.1 are: pressure 11 MPa. The remaining steps are the same as in Embodiment 1, and will not be repeated here.

[0110] Comparative Example 1 This comparative example provides a transformer oil. Unlike Example 1, step 1.1 is omitted. The remaining steps are the same as in Example 1 and will not be repeated here.

[0111] Comparative Example 2 This comparative example provides a transformer oil. Unlike Example 1, steps 1 and 2 are omitted. The remaining steps are the same as in Example 1 and will not be repeated here.

[0112] Comparative Example 3 This comparative example provides a transformer oil. Unlike Example 1, step 1.3 is omitted. The remaining steps are the same as in Example 1 and will not be repeated here.

[0113] Comparative Example 4 This comparative example provides a transformer oil that differs from Example 1 in that it uses naphthenic distillate oil instead of coking diesel oil. The remaining steps are the same as in Example 1 and will not be repeated here.

[0114] Comparative Example 5 This comparative example provides a transformer oil using naphthenic second-line distillate oil as the raw material. The specific preparation process is as follows: 1. The above-mentioned naphthenic distillate oil and hydrogen are mixed at a hydrogen-to-oil volume ratio of 800:1 and then sequentially fed into a series three-stage fixed-bed reaction system: 1.1. The catalyst enters the first hydrogenation reactor, which is packed with ZQC-25 hydrogenation catalyst; reaction conditions: pressure 9.5 MPa, average temperature 340℃, volumetric hourly space velocity (LHSV) 1.0 h⁻¹. -1 .

[0115] 1.2 The effluent from the first hydrogenation reactor enters the second hydrogenation reactor, which is packed with LC-1 hydrodewaxing catalyst (pretreated with nitrogen-resistant hydrothermal treatment: 0.3 MPa, 620℃, 4 h); reaction conditions: pressure 9.5 MPa, average temperature 340℃, volumetric hourly space velocity (LHSV) 1.0 h. -1 .

[0116] 1.3. Continue into the third hydrogenation reactor, which is loaded with LR-1 supplemental refining catalyst; reaction conditions: pressure 9.5 MPa, average temperature 340 °C, volumetric hourly space velocity (LHSV) 1.0 h⁻¹. -1 .

[0117] 2. After being cooled by heat exchange, the reaction effluent enters the stripping tower for gas-liquid separation: tower top operating pressure: 8MPa, temperature: 125℃; tower bottom temperature: 210℃, feed temperature: 205℃.

[0118] 3. The bottom liquid phase of the stripping tower is fed into the vacuum fractionation tower: absolute pressure 0.08MPa; tower top temperature: 62℃, tower bottom temperature: 290℃, feed temperature: 230℃, and the fraction with a temperature >260℃ is taken as the target product: transformer oil base oil.

[0119] 4. Take the base oil obtained above, add 0.30wt% of 2,6-di-tert-butyl-p-cresol (BHT), and stir evenly at 60℃ for 30 minutes to obtain the finished transformer oil.

[0120] Test Example 1 The transformer oils obtained in the examples and comparative examples were subjected to the following tests: (1) Yield (relative to blended oil), % (2) Density at 20℃, g / cm³ 3 Tested according to GB / T1884; (3) Pour point, °C: Tested in accordance with GB / T3535; (4) Kinematic viscosity at -40℃ / 40℃, mm 2 / s: Tested according to GB / T1884; (5) Oxidation stability: Tested according to SH / T0811; (6) Closed-cup flash point, °C: Tested according to GB / T261; (7) Acid value, mgKOH / g: Tested according to GB / T7304.

[0121] The results are summarized in Tables 2, 3, and 4.

[0122] Table 2

[0123] Table 3

[0124] Table 4

[0125] As can be seen from Tables 2, 3, and 4, Examples 1-4 all achieved excellent overall performance under the complete process: the yield was stable at 90.2%~91.9%, the pour point was better than -60℃ in all cases, and the kinematic viscosity at -40℃ was concentrated between 1955~2069 mm. 2The sulfur and nitrogen content are strictly controlled at 1.0 ppm, and key indicators such as oxidation stability, sludge and dielectric loss factor fully meet the requirements of GB2536-2011 for high-end transformer base oil.

[0126] Example 5 did not subject the hydrodewaxing catalyst to nitrogen-resistant hydrothermal pretreatment, resulting in non-selective cracking of the catalyst and a significant drop in yield to 78.1%. This demonstrates that nitrogen-resistant treatment is crucial for ensuring the catalyst's resistance to poisoning and achieving high yield. Example 6 reduced the first hydrogenation pressure to 6 MPa, resulting in a nitrogen residue of up to 32.8 ppm in the product and severely deteriorated oxidation stability with a total acid value of 6.07 mgKOH / g. This indicates that this pressure range represents a technical inflection point that balances hydrogenation depth and product performance. In contrast, Examples 1 and 7 operated within the 7-10 MPa range and consistently met the standards.

[0127] Comparative Example 1, lacking the first hydrogenation step, showed a complete performance degradation; Comparative Example 2, lacking hydrogen decondensation, resulted in a pour point of only -12℃, confirming its irreplaceable role in improving low-temperature fluidity; Comparative Example 3, lacking the third refining step, although meeting the pour point requirements, exhibited a significant decline in oxidation stability, demonstrating the decisive role of deep post-treatment in the long-term reliability of the product. Comparative Examples 4 and 5, using high-quality naphthenic acid distillation as raw material, achieved the required standards under the same process, but at a cost 1000-1500 yuan / ton higher; while Comparative Example 5 further lowered the fractionation cut-off point from 280℃ to 260℃, directly causing the closed-cup flash point to drop to 126℃.

[0128] In summary, this invention, without relying on scarce naphthenic crude oil or investing in new high-voltage equipment, has for the first time achieved the targeted conversion of coking diesel oil into high-end transformer base oil with full fraction, high yield, and high stability.

[0129] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A production process for transformer base oil, characterized in that, Coking diesel and hydrogen are mixed and subjected to a first hydrotreating process to obtain hydrotreated oil; then the hydrotreated oil and hydrogen are mixed and subjected to a second hydrotreating process to obtain hydrode-pour-depressed oil; finally, the hydrode-pour-depressed oil is refined, gas-liquid separated and fractionated to obtain transformer base oil.

2. The production process according to claim 1, characterized in that, The first hydrogenation treatment is carried out at a pressure of 7-10 MPa, a temperature of 300-370 °C, and a volume hourly space velocity of 0.2-1.0 h⁻¹. -1 ; Preferably, the volume ratio of the coking diesel to the hydrogen is 1:(400~600); Preferably, the catalyst used in the first hydrogenation treatment includes at least one of tungsten-nickel type hydrogenation catalyst, molybdenum-nickel type hydrogenation catalyst and molybdenum-tungsten-nickel type hydrogenation catalyst, and is preferably a tungsten-nickel type hydrogenation catalyst.

3. The production process according to claim 1, characterized in that, The second hydroprocessing has a pressure of 7-10 MPa, a temperature of 260-350°C, a volume space velocity of 0.3-2.0 h -1 ; Preferably, the volume ratio of the hydrotreated oil to the hydrogen is 1:(400~600); Preferably, the catalyst used in the second hydrogenation treatment includes at least one of nickel-type hydrogenation catalyst, molybdenum-type hydrogenation catalyst and tungsten-type hydrogenation catalyst, and is preferably a nickel-type hydrogenation catalyst; Preferably, the catalyst used in the second hydrogenation treatment is subjected to nitrogen-resistant treatment before use; Preferably, the nitrogen-resistant treatment involves hydrothermal treatment of the catalyst; Preferably, the hydrothermal treatment is performed at a pressure of 0.1~0.5MPa, a temperature of 500~700℃, and a time of 2~8h.

4. The production process according to claim 1, characterized in that, The refining process is as follows: the hydrodecondensed oil and hydrogen are mixed and subjected to a third hydrotreating process to obtain refined oil; Preferably, the third hydroprocessing is carried out at a pressure of 7 to 11 MPa, a temperature of 260 to 350°C, a volume space velocity of 0.3 to 2.0 h -1 ; Preferably, the volume ratio of the hydrodewaxing product oil to hydrogen is 1:(400~600); Preferably, the catalyst used in the third hydrogenation process includes at least one of a molybdenum-tungsten-nickel type hydrogenation catalyst, a molybdenum-nickel type hydrogenation catalyst, and a tungsten-nickel type hydrogenation catalyst, and is preferably a molybdenum-tungsten-nickel type hydrogenation catalyst.

5. The production process according to claim 1, characterized in that, The gas-liquid separation is carried out in a stripping tower; Preferably, the top pressure of the stripping tower is 0.3~0.6MPa, and the temperature is 100~150℃; Preferably, the bottom temperature of the stripping tower is 190~230℃; Preferably, the feed temperature of the stripping tower is 190~220℃.

6. The production process according to claim 1, characterized in that, The fractionation is carried out inside a fractionation column; Preferably, the fractionation is vacuum fractionation; Preferably, the top pressure of the fractionation column is 0.07~0.09MPa and the temperature is 50~70℃; Preferably, the bottom temperature of the fractionation column is 270~310℃; Preferably, the feed temperature of the fractionation tower is 220~240℃.

7. The production process according to any one of claims 1 to 6, characterized in that, The coking diesel contains 30-50 wt% aromatics, 7000-12000 ppm sulfur, and 2000-5000 ppm nitrogen. Preferably, the pour point of the coking diesel is -10 to 10°C.

8. A transformer base oil, characterized in that, It is prepared using the production process described in any one of claims 1 to 7.

9. The transformer base oil according to claim 8, characterized in that, Pour point < -60℃, sulfur content < 1.0 ppm, nitrogen content < 1.0 ppm, kinematic viscosity at -40℃ < 2100 mm³ / s. 2 / s; Preferably, the transformer base oil has a CA value of <3% and a CN value of >55%.

10. A transformer oil, characterized by, It includes 0.25~0.35wt% antioxidant, with the balance being the transformer base oil as described in claim 8 or 9; The antioxidants include aromatic amine antioxidants and / or hindered phenolic antioxidants.

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