Isotropic focus and method for making the same

Abstract

This invention relates to the field of isotropic coke technology, specifically to an isotropic coke and its preparation method. The method includes: (1) desolidifying catalytic cracking slurry to obtain desolidified oil; (2) contacting the desolidified oil, hydrogen, and a hydrogenation catalyst to perform a hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil; (3) distilling the hydrogenated oil to obtain a distillate oil with a boiling point of 355-520℃; and (4) subjecting the distillate oil and optional auxiliary oil to delayed coking to obtain isotropic petroleum coke. The isotropic coke preparation method provided in this invention, using catalytic cracking slurry as raw material, produces isotropic coke that can be used to produce lithium-ion battery negative electrode carbon materials, solving the problem of catalytic cracking slurry disposal, significantly improving the added value of catalytic cracking slurry, and is suitable for industrial promotion.

Description

Technical Field

[0001] This invention relates to the field of isotropic coke technology, and more specifically to an isotropic coke and its preparation method. Background Technology

[0002] Lithium-ion batteries possess numerous advantages, including high voltage, high energy density, long cycle life, and no memory effect, and have already found widespread application in consumer electronics, power tools, and medical electronics. It is foreseeable that the demand for lithium-ion battery anode materials will also increase.

[0003] Lithium-ion batteries generally consist of a battery casing, a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode is made from negative electrode materials. Lithium-ion battery negative electrode materials mainly include lithium metal negative electrode materials, carbon-based negative electrode materials, silicon-based negative electrode materials, tin-based negative electrode materials, germanium-based negative electrode materials, and lithium titanate negative electrode materials. Among these, carbon-based negative electrode materials have advantages such as small volume expansion after lithium intercalation, low redox potential, high coulombic efficiency, and long cycle life; currently, commercially available lithium-ion battery negative electrode materials are mainly carbon-based.

[0004] Isotropic coke refers to coke whose physical and chemical properties do not change with its spatial orientation; that is, its thermal, mechanical, and electrical properties, such as the coefficient of thermal expansion and resistivity, are roughly equivalent in all directions. Microscopically, its optical structure in all directions is a fine mosaic structure, without any single orientation. Compared with ordinary carbon materials, isotropic coke has high isotropy, high strength, high density, and low porosity, making it suitable for producing lithium-ion battery anode materials. For example, CN113422026A discloses a method for preparing a low-temperature rechargeable anode material using isotropic coke. CN106356530A discloses an anode material for lithium-ion batteries prepared from granular or near-spherical isotropic coke through graphitization.

[0005] CN110734779A discloses an isotropic coke suitable for lithium battery anode materials and its preparation method. The method uses low-temperature coal tar as raw material, centrifuges it through a super centrifuge, and then sends the centrifuged low-temperature coal tar into a flash evaporator for flash evaporation to obtain flash material. Then, the flash material is coked under an inert atmosphere to obtain isotropic coke for lithium-ion battery anode materials.

[0006] CN114525153A discloses a method for preparing isotropic coke for lithium-ion electrode anode materials. The method involves removing quinoline insolubles from aromatic oil by vacuum flash evaporation to obtain flash oil, mixing the flash oil with a nucleating agent in a certain proportion, carrying out a polymerization reaction, and then coking the polymerized oil to prepare isotropic coke.

[0007] Currently, catalytic cracking slurry, especially high-sulfur and high-ash catalytic cracking slurry, is generally sold as inexpensive fuel oil. If catalytic cracking slurry could be used to prepare isotropic coke suitable for producing lithium-ion battery anode carbon materials, its added value could be significantly increased, bringing good economic benefits. However, the methods disclosed in the aforementioned patents are not applicable to processing catalytic cracking slurry.

[0008] Therefore, there is an urgent need to provide a method for preparing isotropic coke that can be used to produce carbon materials for lithium-ion batteries by utilizing high-sulfur and high-ash catalytic cracking slurry. Summary of the Invention

[0009] The purpose of this invention is to overcome the problem in the prior art that it is difficult to directly use high-sulfur and high-ash catalytic cracking slurry to prepare isotropic coke that can be used to produce carbon materials for lithium-ion batteries, and to provide an isotropic coke and its preparation method.

[0010] A first aspect of the present invention provides a method for preparing isotropic petroleum coke, wherein the method includes the following steps:

[0011] (1) The catalytic cracking slurry is subjected to desolidification treatment to obtain desolidified oil;

[0012] (2) The desolidified oil, hydrogen and hydrogenation catalyst are brought into contact to carry out a hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil.

[0013] (3) The hydrogenated oil is distilled to obtain a distillate oil with a boiling point of 300-550℃;

[0014] (4) The distillate oil and optional auxiliary oil are subjected to delayed coking to obtain isotropic petroleum coke.

[0015] A second aspect of the present invention provides an isotropic char prepared using the preparation method described in the first aspect of the present invention.

[0016] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0017] 1) The isotropic coke preparation method provided in this invention, which uses catalytic cracking slurry as raw material, can be used to produce lithium-ion battery negative electrode carbon materials, solving the problem of catalytic cracking slurry disposal and significantly improving the added value of catalytic cracking slurry.

[0018] 2) The method for preparing petroleum coke provided in this invention broadens the sources of isotropic coke that can be used to produce carbon materials for lithium-ion battery anodes. The process is simple, easy to operate, and suitable for industrial promotion. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] A first aspect of the present invention provides a method for preparing an isotropic coke, wherein the method includes the following steps:

[0021] (1) The catalytic cracking slurry is subjected to desolidification treatment to obtain desolidified oil;

[0022] (2) The desolidified oil, hydrogen and hydrogenation catalyst are brought into contact to carry out a hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil.

[0023] (3) The hydrogenated oil is distilled to obtain a distillate oil with a boiling point of 300-550℃;

[0024] (4) The distillate oil and optional auxiliary oil are subjected to delayed coking to obtain isotropic coke.

[0025] In step (1):

[0026] In one embodiment of the present invention, the term "catalytic cracking slurry" has a generally known meaning, and the present invention does not impose any particular limitation on it. The distillation range of the catalytic cracking slurry can be 200-650°C.

[0027] In one embodiment of the present invention, the catalytic cracking slurry comprises, by total mass, 10-20 wt% saturated hydrocarbons, 55-75 wt% aromatics, 10-25 wt% gums and 1-8 wt% asphaltenes.

[0028] In one embodiment of the present invention, the ash content in the catalytic cracking slurry is 0.005-0.5 wt%, the sulfur content is 0.3-1.5 wt%, the nitrogen content is 0.1-0.5 wt%, and the total metal content is 200-600 μg / g.

[0029] In this invention, the catalytic cracking slurry contains catalyst powder added during the oil refining process, resulting in a relatively high ash content. Desolidification treatment of the catalytic cracking slurry can reduce the ash content in the isotropic coke.

[0030] In one embodiment of the present invention, the desolidification process is selected from sedimentation and / or filtration, preferably sedimentation.

[0031] In one embodiment of the present invention, the sedimentation operation includes: first, letting the catalytic cracking slurry stand at 100-120°C for 36-60 hours, and then separating the upper clarified liquid.

[0032] In one embodiment of the present invention, the filtration operation includes filtering the catalytic cracking slurry at 160-200°C. In this invention, the filtration can use a filter screen, or a filter medium such as ceramic, metal, or polymer.

[0033] In step (2):

[0034] In one embodiment of the present invention, the hydrogenation catalyst includes a hydrogenation protectant and a hydrogenation refiner.

[0035] In this invention, both hydrogenation protectants and hydrogenation refining agents known in the art can be used. In this invention, the hydrogenation protectant can intercept particulate matter in the desolidified aromatic hydrocarbons, effectively removing impurities such as metals and residual carbon, thereby reducing the catalyst bed pressure drop, effectively reducing coking at the top of the catalyst bed, and extending the operating cycle of the unit. The hydrogenation refining agent is mainly used to remove impurities such as S and N from the desolidified aromatic hydrocarbons.

[0036] In one embodiment of the present invention, the hydrogenation protectant is selected from one or more of RG-20B, RG-30B, and RG-40B, preferably RG-30B; the hydrogenation refining agent is selected from one or more of RMS-10, RMS-20, and RMS-30, preferably RMS-30.

[0037] In one embodiment of the present invention, the hydrogenation treatment is carried out in a fixed-bed reactor, which is sequentially filled with a hydrogenation protectant and a hydrogenation refining agent, wherein the volume ratio of the hydrogenation protectant to the hydrogenation refining agent is 5-25:75-95, preferably 10-15:85-90.

[0038] In one embodiment of the present invention, the operating conditions for the hydrogenation treatment include: a hydrogenation reaction temperature of 280-445°C, preferably 300-350°C; a hydrogen partial pressure of 2-10 MPa, preferably 3-6 MPa; and a volume hourly space velocity of 0.2-2 h⁻¹. -1 Preferably 0.6-1.2h -1 The hydrogen-to-oil volume ratio is 200-1000 Nm. 3 / m 3 Preferably 600-800 Nm 3 / m 3 .

[0039] In this invention, volume hourly space velocity (VHSV) refers to the volume of desolidified oil passing through a unit volume of catalyst per unit time, and hydrogen-to-oil volume ratio refers to the volume ratio of hydrogen to desolidified oil.

[0040] In one embodiment of the present invention, after the hydrogenation reaction is completed, the hydrogenation product is subjected to gas-liquid separation to obtain hydrogen-rich gas and hydrogenated oil; wherein, the operating conditions for gas-liquid separation include: separation temperature of 200-250℃ and separation pressure of 3-5MPa.

[0041] In this invention, the liquid product separated from the hydrogenation product is hydrogenated oil, and the gaseous product separated is hydrogen-rich gas, comprising various C1-C4 hydrocarbons and hydrogen. To reduce hydrogen consumption, preferably, the hydrogen-rich gas is added to the hydrogen and recycled back into the hydrogenation process.

[0042] In step (3):

[0043] In one embodiment of the present invention, the distillation is carried out in a vacuum distillation column. The present invention does not impose special limitations on the operating conditions of the vacuum distillation column; the deconsolidated catalytic cracking slurry can be cut according to conventional operations.

[0044] In one embodiment of the present invention, the hydrogenated oil is distilled to obtain a distillate oil with a boiling point of 330-510°C.

[0045] In step (4):

[0046] In one embodiment of the present invention, the auxiliary oil is selected from one or more of atmospheric residue, vacuum residue, thermal cracking residue, and furfural extract oil, preferably vacuum residue.

[0047] In this invention, atmospheric residue, vacuum residue, thermal cracking residue, and furfural extract oil have well-known meanings. The distillate oil can be subjected to delayed coking alone, or it can be subjected to delayed coking after mixing with auxiliary oil. The inventors of this invention have discovered that delaying coking after mixing distillate oil and auxiliary oil can further reduce the ash content in isotropic petroleum coke.

[0048] In one embodiment of the present invention, the distillate oil and auxiliary oil are subjected to delayed coking treatment; wherein the mass ratio of the distillate oil to the auxiliary oil is 5-15:1, preferably 8-12:1.

[0049] In one embodiment of the present invention, the operating conditions of the delayed coking treatment include: the outlet temperature of the heating furnace is 440-550℃, preferably 460-520℃; the temperature at the top of the coke tower is 400-460℃, preferably 410-440℃; the pressure at the top of the coke tower is 0.3-1MPa, preferably 0.5-0.8MPa; and the circulation ratio is 0.4-1.5, preferably 0.6-1.

[0050] In this invention, delayed coking treatment yields coking dry gas, coking gasoline, coking diesel, coking gas oil, and isotropic coke. The resulting isotropic coke is characterized by low sulfur, low ash content, low metal content, and high density, and therefore can be used to produce carbon materials for lithium-ion battery anodes.

[0051] In one embodiment of the present invention, the delayed coking process is carried out in a delayed coking apparatus. As is common knowledge in the art, a delayed coking apparatus includes at least a heating furnace, two coke towers and a fractionation tower.

[0052] A second aspect of the present invention provides an isotropic char prepared using the preparation method described in the first aspect of the present invention.

[0053] In one embodiment of the present invention, the isotropic coke contains ≤0.55wt% sulfur, ≤0.3wt% ash, ≤8wt% volatile matter, and has a true density of ≥2.0g / cm³. 3 Tap density (0.5-1mm) ≥ 0.85 g / cm³ 3 Particle homogeneity ≥ 0.7.

[0054] The isotropic coke in this invention is characterized by low sulfur content, high isotropy, and high density, making it a suitable raw material for producing lithium-ion battery anode carbon materials. This invention utilizes catalytic cracking slurry to produce isotropic coke suitable for preparing lithium-ion battery anode carbon materials, significantly increasing the added value of catalytic cracking slurry.

[0055] The present invention will be described in detail below through examples. The hydroprotectant uses the RG-30B catalyst developed by the Research Institute of Petroleum Processing and Refining (RIPP), and the hydrorefining agent uses the RMS-30 catalyst developed by RIPP. Both the hydroprotectant and the hydrorefining agent are produced by Changling Catalyst Plant of Sinopec Catalyst Branch. The composition of the catalytic cracking slurry is shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] Example 1

[0060] (1) The catalytic cracking slurry is placed in the feed buffer tank and left to stand at 110°C for 48 hours to carry out desolidification treatment, and the upper clear liquid is separated to obtain desolidified oil.

[0061] (2) The above-mentioned desolidified oil is pressurized by a booster pump and mixed with hydrogen. After being heated to 350°C in a heater, it enters a fixed-bed hydrogenation reactor and is sequentially contacted with RG-30B catalyst and RMS-30 catalyst to carry out a hydrogenation reaction, thereby obtaining the hydrogenated product. The loading volume ratio of RG-30B catalyst to RMS-30 catalyst is 10:90, the hydrogenation reaction temperature is 320°C, the hydrogen partial pressure is 4.5 MPa, and the hydrogen oil volume is 650 Nm³. 3 / m 3 The volumetric space velocity is 1 h. -1 ;

[0062] The hydrogenation products were then introduced into a high-pressure separator and subjected to gas-liquid separation at 220°C and 4 MPa to obtain hydrogen-rich gas and hydrogenated oil. The hydrogen-rich gas was then added to the hydrogen and returned to the fixed-bed hydrogenation reactor for recycling.

[0063] (3) The above-mentioned hydrogenated oil is introduced into a vacuum distillation tower for vacuum distillation to obtain a distillate oil with a boiling point of 330-510℃;

[0064] (4) The above-mentioned distillate oil is introduced into a delayed coking unit for thermal cracking reaction to obtain coking dry gas, coking gasoline, coking diesel, coking gas oil and petroleum coke; wherein, the operating conditions of the delayed coking unit include a furnace outlet temperature of 470-500℃, a coke tower top temperature of 420℃, a coke tower top pressure of 0.7MPa, and a circulation ratio of 0.8.

[0065] Analysis of the products showed that the yields of coking dry gas, coking gasoline, coking diesel, coking gas oil, and isotropic coke were 17.56%, 11.35%, 20.39%, 5.55%, and 45.15%, respectively.

[0066] The properties of isotropic focal planes are shown in Table 2:

[0067] Table 2

[0068] Isotropic focal Performance indicators S, wt% 0.45 Ash content, wt% 0.20 Volatile matter, wt% 6.6 <![CDATA[True density, g / cm 3 > 2.12 <![CDATA[Tap density (0.5 - 1 mm), g / cm 3 > 0.88 Particle homogeneity 0.75

[0069] Note: Tapped density refers to the tapped density of petroleum coke with an average particle size of 0.5-1 mm. Particle homogeneity is tested using the ratio of thermal expansion coefficients.

[0070] As shown in Table 2, the isotropic coke prepared by the present invention using catalytic cracking slurry has sulfur content, ash content, volatile matter, true density and tap density that meet the raw material requirements for preparing lithium battery anode carbon materials (see GB / T24533-2019: Graphite Anode Materials for Lithium-ion Batteries), and can be used to prepare high-quality lithium battery anode carbon materials.

[0071] Example 2

[0072] (1) The catalytic cracking slurry is placed in the feed buffer tank and left to stand at 110°C for 48 hours to carry out desolidification treatment, and the upper clear liquid is separated to obtain desolidified oil.

[0073] (2) The above-mentioned desolidified oil is pressurized by a booster pump and mixed with hydrogen. After being heated to 350°C in a heater, it enters a fixed-bed hydrotreating reactor and is sequentially contacted with RG-30B catalyst and RMS-30 catalyst to carry out a hydrotreating reaction, thereby obtaining the hydrotreating product. The loading volume ratio of RG-30B catalyst to RMS-30 catalyst is 15:85, the hydrotreating reaction temperature is 340°C, the hydrogen partial pressure is 4.2 MPa, and the hydrogen oil volume is 700 Nm³. 3 / m 3 The volume hourly space velocity is 1.1 h⁻¹. -1 ;

[0074] The hydrogenation products were then introduced into a high-pressure separator and subjected to gas-liquid separation at 220°C and 4 MPa to obtain hydrogen-rich gas and hydrogenated oil. The hydrogen-rich gas was then added to the hydrogen and returned to the fixed-bed hydrogenation reactor for recycling.

[0075] (3) The above-mentioned hydrogenated oil is introduced into a vacuum distillation tower for vacuum distillation to obtain a distillate oil with a boiling point of 330-510℃;

[0076] (4) The above-mentioned distillate oil and vacuum residue are mixed in a mass ratio of 9:1 and then introduced into the delayed coking unit for thermal cracking reaction to obtain coking dry gas, coking gasoline, coking diesel, coking gas oil and petroleum coke; wherein, the operating conditions of the delayed coking unit include a furnace outlet temperature of 465-505℃, a coke tower top temperature of 420℃, a coke tower top pressure of 0.6MPa, and a circulation ratio of 1;

[0077] Analysis of the products showed that the yields of coking dry gas, coking gasoline, coking diesel, coking gas oil, and isotropic coke were 16.08%, 10.75%, 21.08%, 5.8%, and 46.29%, respectively.

[0078] The composition of vacuum residue is shown in Table 3:

[0079] Table 3

[0080]

[0081]

[0082]

[0083] The properties of isotropic focal planes are shown in Table 4:

[0084] Table 4

[0085] Isotropic focal Performance indicators S, wt% 0.49 Ash content, wt% 0.16 Volatile matter, wt% 6.2 <![CDATA[True density, g / cm 3 > 2.11 <![CDATA[Tap density (0.5 - 1 mm), g / cm 3 > 0.87 Particle homogeneity 0.72

[0086] Note: Tapped density refers to the tapped density of petroleum coke with an average particle size of 0.5-1 mm. Particle homogeneity is tested using the ratio of thermal expansion coefficients.

[0087] As shown in Table 2, the isotropic coke prepared by the present invention using catalytic cracking slurry has sulfur content, ash content, volatile matter, true density and tap density that meet the raw material requirements for preparing lithium battery anode carbon materials (see GB / T24533-2019: Graphite Anode Materials for Lithium-ion Batteries), and can be used to prepare high-quality lithium battery anode carbon materials.

[0088] Comparative Example 1

[0089] Similar to Example 1, except that the catalytic cracking slurry is directly introduced into a vacuum distillation tower for vacuum distillation to obtain a distillate oil with a boiling point of 330-510℃, and then the distillate oil is subjected to delayed coking treatment.

[0090] The properties of the petroleum coke prepared in Comparative Example 1 were analyzed, and the results are shown in Table 5.

[0091] Table 5

[0092] petroleum coke Performance indicators S, wt% 1.7 Ash content, wt% 0.35 Volatile matter, wt% 9.2 <![CDATA[True density, g / cm 3 > 2.01 <![CDATA[Tap density (0.5 - 1 mm), g / cm 3 > 0.82 Particle homogeneity 0.55

[0093] As shown in Table 5, the particle isotropy of the petroleum coke prepared in Comparative Example 1 is only 0.55, which does not meet the requirements for isotropic coke. Moreover, the petroleum coke prepared in Comparative Example 1 has high sulfur and ash content, and low true density, tap density, and particle isotropy. Therefore, the lithium battery anode carbon material prepared using the petroleum coke prepared in Comparative Example 1 has poor electrical performance and is not suitable for preparing high-energy-density lithium batteries.

[0094] Test Example 1

[0095] The isotropic coke prepared in Examples 1 and 2, and the petroleum coke prepared in Comparative Example 1, were crushed, granulated, carbonized, and graphitized to prepare lithium-ion battery anode carbon materials.

[0096] Carbon anode material for lithium-ion batteries was used to make anode sheets, which were then assembled into lithium-ion batteries. The initial discharge specific capacity and initial coulombic efficiency of the batteries were then tested according to the test methods in GB / T24533-2019 Graphite Anode Materials for Lithium-ion Batteries. The test results are shown in Table 6.

[0097] Table 6

[0098]

[0099]

[0100] As shown in Table 6, the isotropic coke prepared in this invention can produce high-energy-density lithium batteries with an initial discharge specific capacity of over 355 mAh / g and an initial coulombic efficiency of over 94%. However, the lithium batteries prepared using the petroleum coke obtained in Comparative Example 1 have poor electrical performance, with both the initial discharge specific capacity and initial coulombic efficiency being relatively low.

[0101] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing isotropic coke, characterized in that, The method includes the following steps: (1) The catalytic cracking slurry is subjected to desolidification treatment to obtain desolidified oil; (2) The desolidified oil, hydrogen and hydrogenation catalyst are brought into contact to carry out a hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil; The hydrogenation catalyst includes a hydrogenation protectant and a hydrogenation refining agent; The hydrogenation reaction is carried out in a fixed-bed reactor, which is sequentially filled with a hydrogenation protectant and a hydrogenation refining agent, wherein the volume ratio of the hydrogenation protectant to the hydrogenation refining agent is 5-25:75-95. (3) The hydrogenated oil is distilled to obtain a distillate oil with a boiling point of 300-550℃; (4) The distillate oil and auxiliary oil are subjected to delayed coking to obtain isotropic coke; The auxiliary oil is selected from one or more of atmospheric residue, vacuum residue, thermal cracking residue, and furfural extract. The isotropic coke contains ≤0.55wt% sulfur, ≤0.3wt% ash, ≤8wt% volatile matter, and has a true density ≥2.0g / cm³. 3 The tap density of isotropic coke with an average particle size of 0.5-1 mm is ≥0.85 g / cm³. 3 The particle homogeneity is ≥0.7, and the particle homogeneity is tested using the ratio of thermal expansion coefficients.

2. The preparation method according to claim 1, wherein, Based on the total mass of the catalytic cracking slurry, the catalytic cracking slurry comprises 10-20 wt% saturated hydrocarbons, 55-75 wt% aromatics, 10-25 wt% gums and 1-8 wt% asphaltenes.

3. The preparation method according to claim 1, wherein, The catalytic cracking slurry contains 0.005-0.4 wt% ash, 0.3-1.5 wt% sulfur, 0.1-0.5 wt% nitrogen, and 200-600 µg / g total metals.

4. The preparation method according to claim 1, wherein, The deconsolidation method is selected from sedimentation and / or filtration.

5. The preparation method according to claim 4, wherein, The sedimentation process includes separating the upper clarified liquid after the catalytic cracking slurry has been allowed to stand at 100-120°C for 36-60 hours.

6. The preparation method according to claim 4, wherein, The filtration operation includes filtering the catalytic cracking slurry at 160-200°C.

7. The preparation method according to claim 1, wherein, The hydrogenation protectant is selected from RG-20B and / or RG-30B.

8. The preparation method according to claim 7, wherein, The hydrogenation protectant is RG-30B.

9. The preparation method according to claim 1, wherein, The hydrogenated refining agent is RMS-30.

10. The preparation method according to claim 1, wherein, The filling volume ratio of the hydrogenation protective agent to the hydrogenation refining agent is 10-15:85-90.

11. The preparation method according to claim 1, wherein, The operating conditions for the hydrogenation reaction include: a hydrogenation reaction temperature of 280-445℃; a hydrogen partial pressure of 2-10 MPa; and a volume hourly space velocity of 0.2-2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 200-1000 Nm. 3 / m 3 .

12. The preparation method according to claim 11, wherein, The operating conditions for the hydrogenation reaction include: a hydrogenation reaction temperature of 300-350℃; a hydrogen partial pressure of 3-6 MPa; and a volume hourly space velocity of 0.6-1.2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 600-800 Nm. 3 / m 3 .

13. The preparation method according to any one of claims 1-12, wherein, After the hydrogenation reaction is completed, the hydrogenation product is subjected to gas-liquid separation to obtain hydrogen-rich gas and hydrogenated oil; wherein, the operating conditions for gas-liquid separation include: separation temperature of 200-250℃ and separation pressure of 3-5MPa.

14. The preparation method according to claim 13, wherein, The hydrogen-rich gas is added to the hydrogen gas and returned to the hydrogenation reaction for recycling.

15. The preparation method according to any one of claims 1-12, wherein, The distillation is carried out in a vacuum distillation column.

16. The preparation method according to any one of claims 1-12, wherein, The hydrogenated oil is distilled to obtain a distillate oil with a boiling point of 330-510℃.

17. The preparation method according to claim 1, wherein, The auxiliary oil is vacuum residue.

18. The preparation method according to any one of claims 1-12, wherein, The distillate oil and auxiliary oil are subjected to delayed coking treatment; wherein the mass ratio of the distillate oil to the auxiliary oil is 5-15:

1.

19. The preparation method according to claim 18, wherein, The mass ratio of the distillate oil to the auxiliary oil is 8-12:

1.

20. The preparation method according to any one of claims 1-12, wherein, The operating conditions for the delayed coking process include: furnace outlet temperature of 440-550℃; coke tower top temperature of 400-460℃; coke tower top pressure of 0.3-1MPa; and a circulation ratio of 0.4-1.

5.

21. The preparation method according to claim 20, wherein, The operating conditions for the delayed coking process include: furnace outlet temperature of 460-520℃; coke tower top temperature of 410-440℃; coke tower top pressure of 0.5-0.8MPa; and a circulation ratio of 0.6-1.

22. An isotropic char prepared by any one of claims 1-21.

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