Graphitization Treatment Method of Calcined Petroleum Coke

Abstract

The present invention provides a graphitization treatment method for calcined petroleum coke. The calcined petroleum coke is obtained from crude oil through distillation and thermal cracking. The graphitization treatment method includes: step S1, performing balling treatment on the calcined petroleum coke to obtain a petroleum coke cathode; and step S2, performing molten salt electrolysis on the petroleum coke cathode and an anode to obtain graphitized petroleum coke. The present invention converts low-graphitized calcined petroleum coke into graphitized petroleum coke, a carbonaceous material with a high degree of graphitization, through the molten salt electrolysis graphitization method. Compared with traditional graphitization methods, the electrochemical method can effectively reduce the graphitization temperature, thereby reducing the energy consumption and cost of graphitization.

Description

Technical Field

[0001] The present invention relates to the technical field of graphitization treatment, and in particular, to a method for graphitizing calcined petroleum coke. Background Art

[0002] In the aluminum electrolysis industry, calcined petroleum coke is a key raw material for pre-baked anodes and graphitized cathode blocks. Its graphitization degree directly affects the efficiency and production cost of aluminum electrolysis. Graphitization is an effective way to change the structure of carbonaceous materials, making them have properties such as high temperature resistance, electrical conductivity, and chemical stability. The traditional graphitization process needs to be carried out at high temperatures (usually close to 3000°C), which not only consumes a large amount of electric energy, but also has dangerous production conditions, and at the same time generates a large amount of pollutants.

[0003] Currently, the main methods for improving graphitization include catalytic graphitization method and high temperature and high pressure method, etc. However, a large amount of catalyst is used in the catalytic graphitization method and it is difficult to remove from the graphite; for carbonaceous materials with a porous disordered layer structure, it is difficult to achieve graphitization by the high temperature and high pressure method. The main problems currently faced in the graphitization process of calcined petroleum coke for aluminum electrolysis include high energy consumption and cost, serious environmental pollution, large fluctuations in raw material quality, obvious technical limitations, and increased resource consumption. These problems not only lead to high production costs and serious environmental pollution, but also affect the quality of the final product. Therefore, it is necessary to develop a new type of graphitization technology. Summary of the Invention

[0004] The main object of the present invention is to provide a method for graphitizing calcined petroleum coke, so as to solve the problems of high energy consumption and cost, large environmental pollution, and high requirements for raw materials in the graphitization of calcined petroleum coke in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a method for graphitizing calcined petroleum coke, wherein the calcined petroleum coke is obtained by distilling and thermally cracking crude oil, and the graphitization treatment method includes: step S1, performing pelletizing treatment on the calcined petroleum coke to obtain a petroleum coke cathode; and step S2, performing molten salt electrolysis on the petroleum coke cathode and an anode to obtain graphitized petroleum coke.

[0006] Further, by mass percentage, the calcined petroleum coke includes: 90-93% of carbon element, 0.5-1% of oxygen element, 1-4% of sulfur element, 0.5-1% of nitrogen element, and the balance of other impurity elements; and / or, the graphitization degree of the graphitized petroleum coke is 40-65%.

[0007] Further, the above-mentioned step S1 further includes: step S11, grinding the calcined petroleum coke to obtain petroleum coke powder; step S12, performing spheroidization treatment on the petroleum coke powder by spray drying to obtain petroleum coke microspheres; and step S13, wrapping the petroleum coke microspheres with a current collector to obtain a petroleum coke cathode.

[0008] Further, the particle size of the petroleum coke powder is 1 to 100 nm; and / or, the droplet diameter of the spray drying is 20 to 100 μm, and / or, the time of the spray drying is 5 to 10 s; and / or, the diameter of the petroleum coke microspheres is 5 to 10 μm; the current collector is selected from any one or more of a metal mesh, a metal foam, a graphite paper, a graphite mesh, and a graphite bar.

[0009] Further, the above-mentioned step S2 further includes removing moisture and pre-electrolyzing the molten salt in sequence to obtain a treated molten salt.

[0010] Further, the moisture of the molten salt is removed by vacuum pumping at 180 to 240 °C in a vacuum environment, and the time of the vacuum pumping is 16 to 48 h.

[0011] Further, the pre-electrolysis of the moisture-removed molten salt is carried out after heating to 900 to 950 °C in an argon atmosphere; and / or, the voltage of the pre-electrolysis is 1.5 to 2 V, and / or, the time of the pre-electrolysis is 1.5 to 3 h.

[0012] Further, the molten salt is selected from eutectic molten salts and / or fluorides, the eutectic molten salts are selected from any one or more of CaCl 2 -LiCl, CaCl 2 -NaCl, CaCl 2 -BaCl 2 and CaCl 2 -KCl, and the fluorides are selected from any one or more of NaF, CaF 2 、BaF 2 and KF.

[0013] Further, the above-mentioned step S2 further includes: step S21, placing the petroleum coke cathode and the anode in the treated molten salt for molten salt electrolysis in an inert atmosphere to obtain electrolyzed petroleum coke; and step S22, washing, pickling, and drying the electrolyzed petroleum coke in sequence to obtain graphitized petroleum coke.

[0014] Furthermore, the inert atmosphere is argon or nitrogen; and / or, the anode is graphite; and / or, the temperature of molten salt electrolysis is 850~980℃, and / or, the voltage of molten salt electrolysis is 2.6~3.1V, and / or, the time of molten salt electrolysis is 2~10h; and / or, ultrasonic-assisted distilled water is used for water washing; and / or, acid solution is used for pickling, and the acid solution is a hydrochloric acid solution with a mass concentration of 1~10%; and / or, the drying temperature is 70~80℃.

[0015] Applying the technical solution of the present invention, the present application converts low-graphitization calcined petroleum coke into graphitized petroleum coke, a carbonaceous material with a high degree of graphitization, through a molten salt electrolytic graphitization method. Compared with traditional graphitization methods, the use of an electrochemical method can effectively reduce the graphitization temperature, thereby reducing the energy consumption and cost of graphitization. Specifically, in step S1, the calcined petroleum coke is subjected to a pelletizing treatment, which can effectively improve the structural stability of the calcined petroleum coke and the conductivity between the calcined petroleum coke and the electrolyte molten salt. Among them, the pelletizing treatment is to make the raw material into a spherical material with a certain shape and strength. In step S2, during the electrolysis process, the molten salt can not only transmit current and provide an environment for the electrolytic reaction, but also promote the orderly arrangement of carbon atoms in the calcined petroleum coke and the formation of a graphite structure through its unique ionic effect and chemical properties. Specifically, the molten salt electrolysis method can not only effectively remove gas element impurities (such as oxygen, sulfur and nitrogen, etc.) in the petroleum coke cathode, but also effectively remove a large amount of sulfur content in the petroleum coke cathode, and at the same time make the removed sulfur ions form sulfur on the surface of the anode, thereby realizing efficient recycling of sulfur resources and reducing the consumption of the anode. In addition, the processing method of the present application has low requirements on the quality of raw materials and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 The XRD pattern of graphitized petroleum coke in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] As analyzed in the background technology of this application, the existing technology has the problems of high energy consumption and cost, great environmental pollution and high requirements for raw materials for graphitization of calcined petroleum coke. In order to solve the above problems, this application provides a method for graphitization of calcined petroleum coke.

[0020] In a typical embodiment of the present application, a method for graphitizing calcined petroleum coke is provided. The calcined petroleum coke is obtained from crude oil by distillation and thermal cracking. The method for graphitizing comprises: step S1, pelletizing the calcined petroleum coke to obtain a petroleum coke cathode; and step S2, subjecting the petroleum coke cathode and anode to molten salt electrolysis to obtain graphitized petroleum coke.

[0021] The present application converts low-graphitization calcined petroleum coke into graphitized petroleum coke, a carbonaceous material with a high degree of graphitization, through a molten salt electrolytic graphitization method. Compared with traditional graphitization methods, the use of an electrochemical method can effectively reduce the graphitization temperature, thereby reducing the energy consumption and cost of graphitization. Specifically, in step S1, the calcined petroleum coke is subjected to a pelletizing treatment, which can effectively improve the structural stability of the calcined petroleum coke and the conductivity between the calcined petroleum coke and the electrolyte molten salt. Among them, the pelletizing treatment is to make the raw material into a spherical material with a certain shape and strength. In step S2, during the electrolysis process, the molten salt can not only transmit current and provide an environment for the electrolytic reaction, but also promote the orderly arrangement of carbon atoms in the calcined petroleum coke and the formation of a graphite structure through its unique ionic effect and chemical properties. Specifically, the molten salt electrolysis method can not only effectively remove gas element impurities (such as oxygen, sulfur and nitrogen, etc.) in the petroleum coke cathode, but also effectively remove a large amount of sulfur content in the petroleum coke cathode, and at the same time make the removed sulfur ions form sulfur on the surface of the anode, thereby realizing efficient recycling of sulfur resources and reducing the consumption of the anode. In addition, the processing method of the present application has low requirements on the quality of raw materials and is environmentally friendly.

[0022] In one embodiment of the present application, the calcined petroleum coke comprises, by mass percentage: 90-93% carbon, 0.5-1% oxygen, 1-4% sulfur, 0.5-1% nitrogen, and the remainder other impurity elements; and / or the degree of graphitization of the graphitized petroleum coke is 40-65%, preferably 52-65%, and further preferably 55.3-64.8%.

[0023] Calcined petroleum coke refers to the main raw material for making carbon electrodes for aluminum electrolysis in the aluminum electrolysis industry. It is usually obtained by separating light and heavy oils from crude oil through distillation and then converting them into heavy oil through thermal cracking.

[0024] The calcined petroleum coke preferably includes the above elements, which helps to better perform molten salt electrolysis, thereby increasing the degree of graphitization to within the above range.

[0025] In an embodiment of the present application, the above step S1 further includes: step S11, grinding the calcined petroleum coke to obtain petroleum coke powder; step S12, performing spheronization treatment on the petroleum coke powder by spray drying to obtain petroleum coke microspheres; and step S13, wrapping the petroleum coke microspheres with a current collector to obtain a petroleum coke cathode.

[0026] Preferably, grinding the calcined petroleum coke helps to increase its contact area with the electrolyte, thereby better performing the subsequent spheronization treatment. Preferably, performing spheronization treatment on the petroleum coke powder by spray drying helps to further improve the structural stability of the calcined petroleum coke and its contact area with the electrolyte, thereby improving the electrical conductivity between it and the electrolyte. Preferably, wrapping the petroleum coke microspheres with a current collector helps to enhance the conductive connection between the petroleum coke microspheres, thereby further reducing the cell voltage.

[0027] In an embodiment of the present application, the particle size of the petroleum coke powder is 1 to 100 nm; and / or, the droplet diameter of the spray drying is 20 to 100 μm, and / or, the spray drying time is 5 to 10 s; and / or, the diameter of the petroleum coke microspheres is 5 to 10 μm; the current collector is selected from any one or more of a metal mesh, a metal foam, a graphite paper, a graphite mesh, and a graphite bar.

[0028] Preferably, the particle size of the petroleum coke powder is within the above range, which helps to enhance its contact area and reaction activity with the electrolyte. Preferably, the droplet diameter and time of the spray drying and the diameter of the petroleum coke microspheres are within the above range, which helps the petroleum coke microspheres to have a good specific surface area and pore structure, thereby facilitating the diffusion of reactants and the release of products. Preferably, the type of the current collector is within the above range, which helps to better perform molten salt electrolysis.

[0029] In order to improve the electrical conductivity of the electrolyte and reduce the temperature of molten salt electrolysis, in an embodiment of the present application, the above step S2 further includes removing moisture from the molten salt and pre-electrolyzing it in sequence to obtain the treated molten salt.

[0030] In an embodiment of the present application, the molten salt is dewatered by vacuum pumping at 180 to 240 °C in a vacuum environment, and the vacuum pumping time is 16 to 48 h.

[0031] Preferably, adopting the above vacuum pumping method and the vacuum pumping time within the above range helps to effectively remove the moisture in the molten salt.

[0032] In an embodiment of the present application, after the moisture-removed molten salt is pre-electrolyzed by heating to 900 to 950 °C in an argon atmosphere; and / or, the pre-electrolysis voltage is 1.5 to 2 V, and / or, the pre-electrolysis time is 1.5 to 3 h.

[0033] Preferably, before pre-electrolysis, heating up and controlling the voltage and time of pre-electrolysis within the above ranges are helpful for removing impurities in the molten salt, thereby contributing to providing a more favorable electrolysis environment for graphitization.

[0034] In one embodiment of the present application, the molten salt is selected from eutectic molten salts and / or fluorides. The eutectic molten salt is selected from any one or more of CaCl 2 -LiCl, CaCl 2 -NaCl, CaCl 2 -BaCl 2 and CaCl 2 -KCl, and the fluoride is selected from any one or more of NaF, CaF 2 、BaF 2 and KF.

[0035] Preferably, the above types of molten salts are used because they are easily soluble in water and their electrolysis products are relatively easy to remove, thus contributing to obtaining graphitized petroleum coke with higher purity.

[0036] In one embodiment of the present application, the above step S2 further includes: step S21, in an inert atmosphere, placing the petroleum coke cathode and anode in the treated molten salt for molten salt electrolysis to obtain electrolyzed petroleum coke; and step S22, sequentially washing, pickling, and drying the electrolyzed petroleum coke to obtain graphitized petroleum coke.

[0037] Preferably, the petroleum coke cathode and anode are placed in the treated molten salt for molten salt electrolysis. The treated molten salt helps to conduct current and provide an environment for the electrolysis reaction, thereby promoting the orderly arrangement of carbon atoms in the petroleum coke cathode and the formation of a graphite structure. In addition, the treated molten salt is used continuously without the need to replace the new electrolyte each time, which helps to reduce costs. Preferably, the electrolyzed petroleum coke is washed and pickled, which helps to remove impurities in the electrolyzed petroleum coke, thereby improving the purity of the graphitized petroleum coke.

[0038] In one embodiment of the present application, the inert atmosphere is argon or nitrogen; and / or, the anode is graphite; and / or, the temperature of the molten salt electrolysis is 850 - 980 °C, and / or, the voltage of the molten salt electrolysis is 2.6 - 3.1 V, and / or, the time of the molten salt electrolysis is 2 - 10 h; and / or, ultrasonic-assisted distilled water is used for washing; and / or, pickling is carried out with an acid solution, and the acid solution is a hydrochloric acid solution with a mass concentration of 1 - 10%; and / or, the drying temperature is 70 - 80 °C.

[0039] Preferably controlling the temperature, voltage, and time of molten salt electrolysis within the above ranges helps to promote the orderly arrangement of carbon atoms in the petroleum coke cathode and the formation of a graphite structure, thereby increasing the graphitization degree of graphitized petroleum coke. Preferably, ultrasonic-assisted distilled water is used for water washing, which helps to better remove molten salt and other impurities. Preferably, the above acid solution is used for pickling, which helps to remove metal ion contamination in the petroleum coke after electrolysis. Preferably, drying is carried out under vacuum, and the drying temperature is controlled within the above range, which helps to reduce the structural changes of the graphitized petroleum coke material caused by high temperature.

[0040] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0041] Example 1

[0042] By mass percentage, the calcined petroleum coke includes: 92% carbon element, 0.8% oxygen element, 2.5% sulfur element, 0.6% nitrogen element, and the balance of other impurity elements. The calcined petroleum coke is ground to obtain petroleum coke powder with a particle size of 45 nm. The petroleum coke powder is pelletized by spray drying to obtain petroleum coke microspheres with a diameter of 8 μm, and then wrapped with a graphite paper current collector to obtain a petroleum coke cathode. Among them, the droplet diameter of spray drying is 60 μm, and the spray drying time is 8 s.

[0043] 180 g of anhydrous CaCl 2 -LiCl eutectic molten salt (the molar ratio of CaCl 2 and LiCl is 0.65:0.35) is placed in an alumina crucible, evacuated at 200 °C and under vacuum for 24 h to remove moisture, and then heated to 920 °C in an argon atmosphere and pre-electrolyzed at 1.8 V for 2 h to obtain the treated molten salt. In an argon atmosphere, the petroleum coke cathode and the graphite anode are placed in the treated molten salt, and constant voltage molten salt electrolysis is carried out at 2.8 V at 950 °C for 6 h to obtain the electrolyzed petroleum coke. The electrolyzed petroleum coke is washed with ultrasonic-assisted distilled water, pickled with a hydrochloric acid solution with a mass concentration of 3%, and dried at 75 °C under vacuum to obtain graphitized petroleum coke.

[0044] Example 2

[0045] By mass percentage, the calcined petroleum coke includes: 90% carbon element, 0.5% oxygen element, 1% sulfur element, 0.5% nitrogen element, and the balance of other impurity elements. The calcined petroleum coke is ground to obtain petroleum coke powder with a particle size of 1 nm. The petroleum coke powder is pelletized by spray drying to obtain petroleum coke microspheres with a diameter of 5 μm, and then placed in a φ8 mm graphite frame current collector and connected to a 304 stainless steel rod to make a petroleum coke cathode. Among them, the droplet diameter of spray drying is 20 μm, and the spray drying time is 5 s.

[0046] Put 150 g of anhydrous CaCl 2 -NaCl eutectic molten salt (the molar ratio of CaCl 2 and NaCl is 0.7:0.3) in an alumina crucible, evacuate under vacuum at 180 °C for 48 h to remove moisture, heat to 900 °C under an argon atmosphere and perform pre-electrolysis at 1.5 V for 3 h to obtain the treated molten salt. In an argon atmosphere, place a petroleum coke cathode and a graphite anode in the treated molten salt, and perform constant voltage molten salt electrolysis at 2.6 V at 850 °C for 10 h to obtain electrolyzed petroleum coke. Wash the electrolyzed petroleum coke with ultrasonic-assisted distilled water, pickle it with a 1% hydrochloric acid solution by mass concentration, and dry it under vacuum at 70 °C to obtain graphitized petroleum coke.

[0047] Example 3

[0048] By mass percentage, the calcined petroleum coke includes: 93% carbon element, 1% oxygen element, 4% sulfur element, 1% nitrogen element, and the balance of other impurity elements. Grind the calcined petroleum coke to obtain petroleum coke powder with a particle size of 100 nm. Use spray drying to pelletize the petroleum coke powder to obtain petroleum coke microspheres with a diameter of 10 μm, and then place them in a graphite frame current collector with a diameter of φ8 mm and connect them to a 304 stainless steel rod to make a petroleum coke cathode. Among them, the droplet diameter of spray drying is 100 μm, and the spray drying time is 10 s.

[0049] Put 200 g of BaF 2 in an alumina crucible, evacuate under vacuum at 240 °C for 16 h to remove moisture, heat to 950 °C under an argon atmosphere and perform pre-electrolysis at 2 V for 1.5 h to obtain the treated molten salt. In an argon atmosphere, place a petroleum coke cathode and a graphite anode in the treated molten salt, and perform constant voltage molten salt electrolysis at 3.1 V at 980 °C for 2 h to obtain electrolyzed petroleum coke. Wash the electrolyzed petroleum coke with ultrasonic-assisted distilled water, pickle it with a 10% hydrochloric acid solution by mass concentration, and dry it under vacuum at 80 °C to obtain graphitized petroleum coke.

[0050] Example 4

[0051] The difference from Example 1 is that the droplet diameter of spray drying is 100 μm, the spray drying time is 10 s, and finally graphitized petroleum coke is obtained.

[0052] Example 5

[0053] The difference from Example 1 is that the droplet diameter of spray drying is 150 μm, the spray drying time is 3 s, and finally graphitized petroleum coke is obtained.

[0054] Example 6

[0055] The difference from Example 1 is that the temperature of molten salt electrolysis is 980 °C, and graphitized petroleum coke is finally obtained.

[0056] Example 7

[0057] The difference from Example 1 is that the temperature of molten salt electrolysis is 820 °C, and graphitized petroleum coke is finally obtained.

[0058] Example 8

[0059] The difference from Example 1 is that the voltage of molten salt electrolysis is 2.6 V, the time of molten salt electrolysis is 4 h, and graphitized petroleum coke is finally obtained.

[0060] Example 9

[0061] The difference from Example 1 is that the voltage of molten salt electrolysis is 3.5 V, the time of molten salt electrolysis is 1 h, and graphitized petroleum coke is finally obtained.

[0062] Comparative Example 1

[0063] The calcined petroleum coke is put into an Acheson graphitization furnace and heated at 3000 °C for 48 h to obtain graphitized petroleum coke.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that after the calcined petroleum coke is ground, it is wrapped with a graphite paper current collector to obtain a petroleum coke cathode, and finally graphitized petroleum coke is obtained.

[0066] Test method

[0067] The graphitized petroleum coke of the above examples and comparative examples was subjected to performance tests, and the test results are shown in Table 1.

[0068] Table 1

[0069]

[0070] Among them, Figure 1 is the XRD pattern of the graphitized petroleum coke in Example 1. As can be seen from Figure 1 , the diffraction angle corresponding to the (002) crystal plane of the calcined petroleum coke after molten salt electrolysis is 26.33°. According to the graphitization degree calculation formula Mering-Maire (Franklin formula), under this electrolysis condition, the graphitization degree of the calcined petroleum coke is 64.2%.

[0071] Compared with the high-temperature graphitization method of Comparative Example 1, the examples of the present application can still achieve a relatively high graphitization degree at a lower temperature. Therefore, while taking into account the graphitization degree of graphitized petroleum coke, the present application can reduce the energy consumption and cost of graphitizing calcined petroleum coke.

[0072] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0073] The present application converts low-graphitization calcined petroleum coke into graphitized petroleum coke, a carbonaceous material with a high degree of graphitization, through a molten salt electrolytic graphitization method. Compared with traditional graphitization methods, the use of an electrochemical method can effectively reduce the graphitization temperature, thereby reducing the energy consumption and cost of graphitization. Specifically, in step S1, the calcined petroleum coke is subjected to a pelletizing treatment, which can effectively improve the structural stability of the calcined petroleum coke and the conductivity between the calcined petroleum coke and the electrolyte molten salt. Among them, the pelletizing treatment is to make the raw material into a spherical material with a certain shape and strength. In step S2, during the electrolysis process, the molten salt can not only transmit current and provide an environment for the electrolytic reaction, but also promote the orderly arrangement of carbon atoms in the calcined petroleum coke and the formation of a graphite structure through its unique ionic effect and chemical properties. Specifically, the molten salt electrolysis method can not only effectively remove gas element impurities (such as oxygen, sulfur and nitrogen, etc.) in the petroleum coke cathode, but also effectively remove a large amount of sulfur content in the petroleum coke cathode, and at the same time make the removed sulfur ions form sulfur on the surface of the anode, thereby realizing efficient recycling of sulfur resources and reducing the consumption of the anode. In addition, the processing method of the present application has low requirements on the quality of raw materials and is environmentally friendly.

[0074] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for graphitizing calcined petroleum coke, wherein the calcined petroleum coke is obtained from crude oil by distillation and thermal cracking, characterized in that: The graphitization treatment method comprises: Step S1, pelletizing the calcined petroleum coke to obtain a petroleum coke cathode; and Step S2, subjecting the petroleum coke cathode and anode to molten salt electrolysis to obtain graphitized petroleum coke; The step S1 further comprises: Step S11, grinding the calcined petroleum coke to obtain petroleum coke powder; Step S12, performing the ball-forming treatment on the petroleum coke powder by spray drying to obtain petroleum coke microspheres; and Step S13, using a current collector to wrap the petroleum coke microspheres to obtain the petroleum coke cathode; The droplet diameter of the spray drying is 20-100 μm, and the spray drying time is 5-10 s.

2. The graphitization method according to claim 1, characterized in that: In terms of mass percentage, the calcined petroleum coke comprises: 90-93% carbon, 0.5-1% oxygen, 1-4% sulfur, 0.5-1% nitrogen, and the remainder is other impurity elements; and / or the graphitization degree of the graphitized petroleum coke is 40-65%.

3. The graphitization method according to claim 1, characterized in that: The particle size of the petroleum coke powder is 1-100 nm; and / or the diameter of the petroleum coke microspheres is 5-10 μm; the current collector is selected from any one or more of metal mesh, metal foam, graphite paper, graphite mesh and graphite column.

4. The graphitization method according to claim 1 or 2, characterized in that: The step S2 also includes removing moisture from the molten salt and pre-electrolyzing the molten salt in sequence to obtain treated molten salt.

5. The graphitization method according to claim 4, characterized in that: The molten salt is vacuumed at 180-240° C. to remove moisture, and the vacuuming time is 16-48 hours.

6. The graphitization method according to claim 4, characterized in that: The pre-electrolysis is performed on the molten salt after the water is removed after the temperature is raised to 900-950° C. in an argon atmosphere; and / or the voltage of the pre-electrolysis is 1.5-2V, and / or the time of the pre-electrolysis is 1.5-3h.

7. The graphitization method according to claim 4, characterized in that: The molten salt is selected from eutectic molten salt and / or fluoride, the eutectic molten salt is selected from any one or more of CaCl2-LiCl, CaCl2-NaCl, CaCl2-BaCl2 and CaCl2-KCl, and the fluoride is selected from any one or more of NaF, CaF2, BaF2 and KF.

8. The graphitization method according to claim 4, characterized in that: The step S2 further comprises: Step S21, placing the petroleum coke cathode and the anode in the treated molten salt in an inert atmosphere to perform molten salt electrolysis to obtain electrolyzed petroleum coke; and Step S22, washing, acid washing and drying the electrolyzed petroleum coke in sequence to obtain the graphitized petroleum coke.

9. The graphitization method according to claim 8, characterized in that: The inert atmosphere is argon or nitrogen; and / or the anode is graphite; and / or the temperature of the molten salt electrolysis is 850-980° C., and / or the voltage of the molten salt electrolysis is 2.6-3.1 V, and / or the time of the molten salt electrolysis is 2-10 h; and / or, using ultrasonic wave-assisted distilled water for the water washing; And / or, the pickling is performed using an acid solution, wherein the acid solution is a hydrochloric acid solution with a mass concentration of 1-10%; and / or, the drying temperature is 70-80°C.

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