Isotropic coke and preparation method thereof

Abstract

The invention relates to the technical field of isotropic coke, in particular to isotropic coke and a preparation method thereof. The method comprises the following steps: (1) performing solid removal treatment on catalytic cracking slurry oil to obtain solid-removed oil; (2) contacting the solid-removed oil, hydrogen and a hydrogenation catalyst, and carrying out hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil; (3) distilling the hydrogenated oil to obtain distillate oil with the boiling point of 355-520 DEG C; and (4) carrying out delayed coking on the distillate oil and optional auxiliary oil to obtain the isotropic petroleum coke. According to the preparation method of the isotropic coke provided by the invention, the isotropic coke prepared by taking the catalytic cracking oil slurry as the raw material can be used for producing a lithium ion battery negative electrode carbon material, the problem of the outlet of the catalytic cracking oil slurry is solved, the added value of the catalytic cracking oil slurry is remarkably improved, and the preparation method is suitable for industrial popularization.

Description

Technical Field

[0001] The invention relates to the technical field of isotropic coke, and in particular to an isotropic coke and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have many advantages such as high voltage, high energy, long cycle life, and no memory effect, and have been widely used in consumer electronics, power tools, medical electronics, etc. It is foreseeable that the demand for lithium-ion battery negative electrode materials will also increase.

[0003] Lithium-ion batteries generally include a battery case, a positive electrode, a negative electrode, a separator and an electrolyte. Among them, the negative electrode is prepared from a negative electrode material. The negative electrode materials of lithium-ion batteries mainly include metallic lithium negative electrode materials, carbon-based negative electrode materials, silicon-based negative electrode materials, tin-based negative electrode materials, germanium-based negative electrode materials, lithium titanate negative electrode materials, etc. Among them, carbon-based negative electrode materials have the advantages of small volume expansion after lithium insertion, low redox potential, high coulomb efficiency and long cycle life. The negative electrode materials of commercial lithium-ion batteries are currently dominated by carbon-based negative electrode materials.

[0004] Isotropic coke refers to a coke whose physical and chemical properties do not change with its spatial direction, that is, the thermal properties, mechanical properties, electrical properties such as thermal expansion coefficient, resistivity and other indicators in all directions are roughly equivalent. Microscopically, the optical structure in all directions is a fine mosaic structure without a single orientation. Compared with ordinary carbon materials, isotropic coke has the characteristics of high isotropy, high strength, high density and low porosity, and can be used to produce negative electrode materials for lithium batteries. For example, CN113422026A discloses a negative electrode material that can be charged at low temperature using isotropic coke and a preparation method thereof. CN106356530A discloses a negative electrode material that can be used for lithium-ion batteries, which is prepared from granular or spherical isotropic coke as a raw material and graphitized.

[0005] CN110734779A discloses an isotropic coke suitable for anode raw materials of lithium batteries and a preparation method thereof. Low-temperature coal tar is used as a raw material, centrifuged by a super centrifuge, and then the centrifuged low-temperature coal tar is sent to a flash evaporator for flash evaporation to obtain a flash material; then the flash material is coked in an inert atmosphere to obtain isotropic coke for the cathode raw material of lithium ion batteries.

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

[0007] At present, catalytic cracking slurry, especially high-sulfur and high-ash catalytic cracking slurry, is generally shipped as cheap fuel oil. If catalytic cracking slurry can be used to prepare isotropic coke that can be used to produce negative electrode carbon materials for lithium-ion batteries, the added value of catalytic cracking slurry can be significantly improved, bringing good economic benefits. However, the methods disclosed in the above patents are not suitable for 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 negative electrode carbon materials for lithium-ion batteries using high-sulfur and high-ash catalytic cracking oil slurry. Summary of the invention

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

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

[0011] (1) desolidifying the catalytic cracking oil slurry to obtain desolidified oil;

[0012] (2) contacting the desolidified oil, hydrogen and a hydrogenation catalyst to carry out a hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil;

[0013] (3) distilling the hydrogenated oil to obtain a distillate oil with a boiling point of 300-550° C.;

[0014] (4) Delaying coking the distillate oil and optional auxiliary oil to obtain isotropic petroleum coke.

[0015] The second aspect of the present invention provides an isotropic coke prepared by the preparation method described in the first aspect of the present invention.

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

[0017] 1) The method for preparing isotropic coke provided in the present invention uses catalytic cracking slurry as raw material to prepare isotropic coke which can be used to produce negative electrode carbon materials for lithium-ion batteries, thereby solving the outlet of catalytic cracking slurry and significantly improving the added value of catalytic cracking slurry;

[0018] 2) The method for preparing petroleum coke provided in the present invention broadens the source of isotropic coke that can be used to produce negative electrode carbon materials for lithium-ion batteries, and has a simple process, convenient operation, and is suitable for industrial promotion. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

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

[0021] (1) desolidifying the catalytic cracking oil slurry to obtain desolidified oil;

[0022] (2) contacting the desolidified oil, hydrogen and a hydrogenation catalyst to carry out a hydrogenation reaction to obtain hydrogen-rich gas and hydrogenated oil;

[0023] (3) distilling the hydrogenated oil to obtain a distillate oil with a boiling point of 300-550° C.;

[0024] (4) subjecting the distillate oil and optional auxiliary oil to delayed coking to obtain isotropic coke.

[0025] In step (1):

[0026] In one embodiment of the present invention, the catalytic cracking slurry has a well-known meaning, and the present invention does not specifically limit it. The distillation range of the catalytic cracking slurry may be 200-650°C.

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

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

[0029] In the present invention, the catalytic cracking oil slurry contains some catalyst powder added in the oil refining process, so the ash content is relatively high. The ash content in the isotropic coke can be reduced by desolidifying the catalytic cracking oil slurry.

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

[0031] In one embodiment of the present invention, the sedimentation operation comprises: firstly allowing the catalytic cracking oil slurry to 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 filtering operation comprises filtering the catalytic cracking oil slurry at 160-200° C. In the present invention, the filtering can be performed using 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 comprises a hydrogenation protectant and a hydrogenation finishing agent.

[0035] Among them, the hydrogenation protective agent and hydrogenation refining agent known in the art can be used in the present invention. In the present invention, the hydrogenation protective agent can intercept the particulate matter in the desolidified rich aromatics, effectively remove the impurities such as metals and residual carbon in the desolidified rich aromatics, so as to reduce the pressure drop of the catalyst bed, effectively reduce the coking on the top of the catalyst bed, and extend the operation cycle of the device. The hydrogenation refining agent is mainly used to remove impurities such as S and N in the desolidified rich aromatics.

[0036] In one embodiment of the present invention, the hydrogenation protective agent 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 hydroprocessing is carried out in a fixed bed reactor, and the fixed bed reactor is sequentially filled with a hydrogenation protective agent and a hydrogenation refining agent, and the filling volume ratio of the hydrogenation protective agent 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 of the hydroprocessing include: the hydrogenation reaction temperature is 280-445°C, preferably 300-350°C; the hydrogen partial pressure is 2-10MPa, preferably 3-6MPa; the volume space velocity is 0.2-2h -1 , preferably 0.6-1.2h -1 ; Hydrogen oil volume ratio is 200-1000Nm 3 / m 3 , preferably 600-800Nm 3 / m 3 .

[0039] In the present invention, volumetric space velocity 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 the gas-liquid separation include: a separation temperature of 200-250°C and a separation pressure of 3-5MPa.

[0041] Among them, in the present invention, the liquid phase product separated from the hydrogenation product is hydrogenated oil, and the gas phase product separated is hydrogen-rich gas, including various hydrocarbons of C1-C4 and hydrogen and other components. In order to reduce hydrogen consumption, preferably, the hydrogen-rich gas is added to the hydrogen and returned to the hydrogenation process for recycling.

[0042] In step (3):

[0043] In one embodiment of the present invention, the distillation is carried out in a vacuum distillation tower. The present invention does not specifically limit the operating conditions of the vacuum distillation tower, and the desolidified catalytic cracking oil 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 oil, vacuum residue oil, thermal cracking residue oil, and furfural extracted oil, preferably vacuum residue oil.

[0047] Among them, atmospheric residue, vacuum residue, thermal cracking residue, and furfural extracted oil have well-known meanings. In the present invention, the distillate oil can be subjected to delayed coking alone, or the distillate oil and auxiliary oil can be mixed and then subjected to delayed coking. The inventor of the present invention has found through research that the ash content in the isotropic petroleum coke can be further reduced by mixing the distillate oil and auxiliary oil and then subjected to delayed coking.

[0048] In one embodiment of the present invention, the distillate oil and the 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°C, preferably 460-520°C; the temperature of the top of the coke tower is 400-460°C, preferably 410-440°C; the pressure at the top of the coke tower is 0.3-1MPa, preferably 0.5-0.8MPa; the circulation ratio is 0.4-1.5, preferably 0.6-1.

[0050] Among them, in the present invention, after delayed coking treatment, coking dry gas, coking gasoline, coking diesel, coking gas oil and isotropic coke can be obtained. The obtained isotropic coke has the characteristics of low sulfur, low ash, low metal content and high density, and can be used to produce negative electrode carbon materials for lithium ion batteries.

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

[0052] The second aspect of the present invention provides an isotropic coke prepared by the preparation method described in the first aspect of the present invention.

[0053] In one embodiment of the present invention, the S content in the isotropic coke is ≤0.55wt%, the ash content is ≤0.3wt%, the volatile matter is ≤8wt%, and the true density is ≥2.0g / cm 3 , tap density (0.5-1mm) ≥ 0.85g / cm 3 , particle homogeneity ≥0.7.

[0054] The isotropic coke in the present invention has the characteristics of low sulfur content, high isotropy and high density, and is a raw material that can be used to produce negative electrode carbon materials for lithium batteries. The present invention uses catalytic cracking slurry to produce isotropic coke that can be used to prepare negative electrode carbon materials for lithium batteries, which can significantly increase the added value of catalytic cracking slurry.

[0055] The present invention will be described in detail below through examples. The hydrogenation protective agent uses the RG-30B catalyst developed by the Institute of Petroleum Science and Technology, and the hydrogenation refining agent uses the RMS-30 catalyst developed by the Institute of Petroleum Science and Technology. The hydrogenation protective agent and the hydrogenation refining agent are both produced by the Changling Catalyst Plant of Sinopec Catalyst Branch. The composition of the catalytic cracking oil slurry is shown in Table 1:

[0056] Table 1

[0057]

[0058]

[0059] Example 1

[0060] (1) placing the catalytic cracking oil slurry in a raw material buffer tank and standing it at 110° C. for 48 hours to perform a desolidification treatment, separating the upper clear liquid to obtain desolidified oil;

[0061] (2) The desolidified oil is pressurized by a booster pump and mixed with hydrogen, and then heated to 350° C. in a heating furnace and then enters a fixed bed hydrogenation reactor, where it is contacted with an RG-30B catalyst and an RMS-30 catalyst in sequence to undergo a hydrogenation reaction to obtain a hydrogenated product; wherein the loading volume ratio of the RG-30B catalyst to the 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 Nm 3 / m 3 , volume space velocity is 1h -1 ;

[0062] Then, the hydrogenation product is introduced into a high-pressure separator, and gas-liquid separation is performed at 220°C and 4MPa to obtain hydrogen-rich gas and hydrogenated oil. The hydrogen-rich gas is added to hydrogen and returned to the fixed-bed hydrogenation reactor for recycling;

[0063] (3) introducing the hydrogenated oil into a vacuum distillation tower for vacuum distillation to obtain a distillate oil with a boiling point of 330-510° C.;

[0064] (4) introducing the above distillate oil 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 heating furnace outlet temperature of 470-500° C., a coke tower top temperature of 420° C., a coke tower top pressure of 0.7 MPa, and a circulation ratio of 0.8;

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

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

[0067] Table 2

[0068] Isotropic Focus Performance Indicators S, wt% 0.45 Ash, 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: Tap density refers to the tap density of petroleum coke with an average particle size of 0.5-1mm. Particle homogeneity is tested using the thermal expansion coefficient ratio method.

[0070] Among them, it can be seen from Table 2 that the isotropic coke prepared by the present invention using catalytic cracking oil slurry, sulfur element, ash content, volatile matter, true density and tap density meet the requirements of raw materials that can be used to prepare lithium battery negative electrode carbon materials (see GB / T24533-2019: Graphite negative electrode materials for lithium ion batteries), and can be used to prepare high-quality lithium battery negative electrode carbon materials.

[0071] Example 2

[0072] (1) placing the catalytic cracking oil slurry in a raw material buffer tank and standing it at 110° C. for 48 hours to perform a desolidification treatment, separating the upper clear liquid to obtain desolidified oil;

[0073] (2) The desolidified oil is pressurized by a booster pump and mixed with hydrogen, and then heated to 350° C. in a heating furnace and then enters a fixed bed hydrogenation reactor, where it is contacted with an RG-30B catalyst and an RMS-30 catalyst in sequence to undergo a hydrogenation reaction to obtain a hydrogenated product; wherein the loading volume ratio of the RG-30B catalyst to the RMS-30 catalyst is 15:85, the hydrogenation reaction temperature is 340° C., the hydrogen partial pressure is 4.2 MPa, and the hydrogen oil volume is 700 Nm 3 / m 3 , volume space velocity is 1.1h -1 ;

[0074] Then, the hydrogenation product is introduced into a high-pressure separator, and gas-liquid separation is performed at 220°C and 4MPa to obtain hydrogen-rich gas and hydrogenated oil. The hydrogen-rich gas is added to hydrogen and returned to the fixed-bed hydrogenation reactor for recycling;

[0075] (3) introducing the hydrogenated oil into a vacuum distillation tower for vacuum distillation to obtain a distillate oil with a boiling point of 330-510° C.;

[0076] (4) mixing the above-mentioned distillate oil and vacuum residue oil in a mass ratio of 9:1 and introducing the mixture 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 heating furnace outlet temperature of 465-505° C., a coke tower top temperature of 420° C., a coke tower top pressure of 0.6 MPa, and a circulation ratio of 1;

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

[0078] Wherein, the composition of vacuum residue is shown in Table 3:

[0079] Table 3

[0080]

[0081]

[0082]

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

[0084] Table 4

[0085] Isotropic Focus Performance Indicators S, wt% 0.49 Ash, 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: Tap density refers to the tap density of petroleum coke with an average particle size of 0.5-1mm. Particle homogeneity is tested using the thermal expansion coefficient ratio method.

[0087] Among them, it can be seen from Table 2 that the isotropic coke prepared by the present invention using catalytic cracking oil slurry, sulfur element, ash content, volatile matter, true density and tap density meet the requirements of raw materials that can be used to prepare lithium battery negative electrode carbon materials (see GB / T24533-2019: Graphite negative electrode materials for lithium ion batteries), and can be used to prepare high-quality lithium battery negative electrode carbon materials.

[0088] Comparative Example 1

[0089] The same as Example 1, except that the catalytic cracking oil slurry is directly introduced into the vacuum distillation tower for vacuum distillation to obtain a distillate oil with a boiling point of 330-510° C., 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, 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 homogeneity of the petroleum coke prepared in Comparative Example 1 is only 0.55, which does not meet the requirements of isotropic coke. Moreover, the petroleum coke prepared in Comparative Example 1 has high sulfur content and ash content, low true density, tap density and particle homogeneity, and the electrical properties of the lithium battery negative electrode carbon material prepared using the petroleum coke prepared in Comparative Example 1 are poor, and it is not suitable for preparing a high energy density lithium battery.

[0094] Test Example 1

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

[0096] The negative electrode carbon material of the lithium-ion battery is made into a negative electrode sheet and assembled into a lithium-ion battery. Then, the first discharge specific capacity and the first coulomb efficiency of the battery are tested according to the test method in GB / T24533-2019 lithium-ion battery graphite negative electrode material. The test results are shown in Table 6:

[0097] Table 6

[0098]

[0099]

[0100] It can be seen from Table 6 that the isotropic coke prepared in the present invention can be used to prepare a high energy density lithium battery with a first discharge capacity of more than 355 mAh / g and a first coulombic efficiency of more than 94%. However, the electrical performance of the lithium battery prepared using the petroleum coke prepared in Comparative Example 1 is poor, and both the first discharge capacity and the first coulombic efficiency are relatively low.

[0101] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing isotropic coke, characterized in that: The method comprises the following steps: (1) desolidifying the catalytic cracking oil slurry to obtain desolidified oil; (2) contacting the desolidified oil, hydrogen and a hydrogenation catalyst to carry out 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 300-550° C.; (4) subjecting the distillate oil and optional auxiliary oil to delayed coking to obtain isotropic coke.

2. The preparation method according to claim 1, wherein Based on the total mass of the catalytic cracking slurry, the catalytic cracking slurry comprises 10-20wt% of saturated hydrocarbons, 55-75wt% of aromatic hydrocarbons, 10-25wt% of colloids and 1-8wt% of asphaltenes; Preferably, the ash content in the catalytic cracking oil slurry is 0.005-0.4wt%, the sulfur content is 0.3-1.5wt%, the nitrogen content is 0.1-0.5wt%, and the total content of metal elements is 200-600μg / g.

3. The preparation method according to claim 1 or 2, wherein The desolidification method is selected from sedimentation and / or filtration; Preferably, the sedimentation operation comprises standing the catalytic cracking oil slurry at 100-120° C. for 36-60 hours to separate the upper clear liquid; Preferably, the filtering operation comprises filtering the catalytic cracking oil slurry at 160-200°C.

4. The preparation method according to any one of claims 1 to 3, wherein The hydrogenation catalyst comprises a hydrogenation protective agent and a hydrogenation refining agent; Preferably, the hydrogenation protective agent is selected from one or more of RG-20B, RG-30B, and RG-40B, preferably RG-30B; Preferably, the hydrogenation refining agent is selected from one or more of RMS-10, RMS-20, and RMS-30, preferably RMS-30; Preferably, the hydroprocessing is carried out in a fixed bed reactor, in which a hydrogenation protective agent and a hydrogenation refining agent are sequentially loaded, and the loading volume ratio of the hydrogenation protective agent to the hydrogenation refining agent is 5-25:75-95, preferably 10-15:85-90.

5. The preparation method according to any one of claims 1 to 4, wherein: The operating conditions of the hydrogenation reaction include: the hydrogenation reaction temperature is 280-445°C, preferably 300-350°C; the hydrogen partial pressure is 2-10MPa, preferably 3-6MPa; the volume space velocity is 0.2-2h -1 , preferably 0.6-1.2h -1 ; Hydrogen oil volume ratio is 200-1000Nm 3 / m 3 , preferably 600-800Nm 3 / m 3 .

6. The preparation method according to any one of claims 1 to 5, 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 the gas-liquid separation include: a separation temperature of 200-250°C and a separation pressure of 3-5MPa; Preferably, the hydrogen-rich gas is added to the hydrogen gas and returned to the hydrogenation reaction for cyclic use.

7. The preparation method according to any one of claims 1 to 6, wherein: The distillation is carried out in a vacuum distillation tower; Preferably, the hydrogenated oil is distilled to obtain a distillate oil with a boiling point of 330-510°C.

8. The preparation method according to any one of claims 1 to 7, wherein: The auxiliary oil is selected from one or more of atmospheric residue oil, vacuum residue oil, thermal cracking residue oil, and furfural extracted oil, preferably vacuum residue oil; Preferably, the hydrogenated oil and the auxiliary oil are subjected to delayed coking treatment; wherein the mass ratio of the hydrogenated oil to the auxiliary oil is 5-15:1, preferably 8-12:

1.

9. The preparation method according to any one of claims 1 to 8, wherein: The operating conditions of the delayed coking treatment include: the outlet temperature of the heating furnace is 440-550°C, preferably 460-520°C; the temperature of the top of the coke tower is 400-460°C, preferably 410-440°C; the pressure at the top of the coke tower is 0.3-1MPa, preferably 0.5-0.8MPa; the circulation ratio is 0.4-1.5, preferably 0.6-1.

10. Isotropic coke prepared by the preparation method according to any one of claims 1 to 9.

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