Preparation method and application of inlaid highly isotropic coke

Abstract

The invention discloses a preparation method and application of inlaid highly isotropic coke, petroleum residual oil, petroleum asphalt, heavy oil or coal tar pitch are used as raw materials, a certain amount of graphene oxide or graphene is added, melt blending is carried out at a certain temperature, heat treatment is carried out at a certain atmosphere, pressure and temperature, and the inlaid highly isotropic coke is obtained. Isotropic semicoke rich in the superfine mosaic structure is prepared, and the superfine mosaic type highly isotropic coke is obtained after the obtained isotropic semicoke with the superfine mosaic structure is calcined. The isotropic degree of the prepared coke is greatly improved, and the isotropic degree and various performance indexes of the isotropic graphite material prepared by taking the prepared isotropic coke as the raw material are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of high isotropic coke required for the production and preparation of high-end isotropic graphite materials. This invention provides a method for the preparation and application of ultrafine embedded highly isotropic high-performance coke. Background Technology

[0002] With the rapid development of the semiconductor industry and nuclear power technology, high demands are being placed on graphite materials needed for semiconductor material preparation and nuclear reactor construction. These demands require high electrical and thermal conductivity, high density, high purity, and high uniformity, especially high isotropy. However, graphite microcrystalline structures theoretically exhibit anisotropy, and at high temperatures, the orientation of graphite microcrystals can become ordered. Based on this, this paper proposes designing and controlling the structure of the coke raw material for preparing graphite materials to produce highly isotropic coke with ultra-fine mosaic microstructures. This ensures that the produced isotropic graphite material possesses high isotropy and excellent physicochemical properties from the raw material stage.

[0003] Patent CN118620637A discloses a process for producing high-end isotropic coke. In the heating and cracking of wax oil feedstock, the gaseous products are fractionated to obtain liquid products. The liquid products are then added together with a polymerization initiator to the circulating oil to form coke in a coking tower.

[0004] Patent CN117383553A discloses a method for preparing isotropic coke for nuclear graphite. The method involves distilling high-temperature coal tar to obtain distillate oil; mixing the distillate oil with a solvent and then separating it through flocculation to obtain light phase oil and heavy phase oil; distilling the light phase oil to recover the solvent and obtain light purified tar; distilling the heavy phase oil to recover the solvent and obtain heavy tar; separating the heavy tar and solvent through extraction to obtain soluble and insoluble phases; distilling the soluble phase to recover the solvent and obtain heavy purified tar; subjecting the light purified tar to multi-stage series hydrogenation to obtain distillate oil A; subjecting the heavy purified tar to hydrogenation catalytic cracking to obtain distillate oil B; subjecting distillate oil B to vacuum distillation to obtain distillate oil C; subjecting distillate oil A to asphaltification to obtain prepolymerized asphalt; mixing distillate oil C with prepolymerized asphalt and then carbonizing it in the liquid phase to obtain embedded semi-raw coke; crushing the embedded semi-raw coke and then calcining it to obtain isotropic coke for nuclear graphite.

[0005] While the aforementioned inventions have successfully produced isotropic coke with good physical properties, the preparation steps are numerous and the process is complex, and it is only applicable to specific raw materials. Therefore, finding isotropic coke with a simple process that is suitable for the production of existing industrial coke is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing and applying highly isotropic embedded coke. This invention uses petroleum residue, petroleum asphalt, heavy oil, or coal tar pitch as raw materials, adds a certain amount of graphene oxide or graphene, melts and blends them at a certain temperature, and then heat-treats them under a certain atmosphere, pressure, and temperature to prepare isotropic semi-coke rich in ultrafine embedded structures. The resulting ultrafine embedded structure isotropic semi-coke is then calcined to obtain ultrafine embedded highly isotropic coke.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing a mosaic-type highly isotropic coke includes the following steps: Step S1: Prepare the additive dispersion by heating the raw material to 50-60°C above its softening point and holding it at that temperature. Then, mix the additive dispersion with the raw material to obtain a uniformly mixed molten raw material. The additive dispersion is an organic solvent dispersion of graphene oxide or an organic solvent dispersion of graphene; the raw material is coal tar pitch, petroleum pitch, petroleum residue oil or heavy oil. Step S2: Heat the molten raw material to the temperature at which the mesophase is formed, and stir continuously for 0.5-1 hour. Then stop stirring, remove the stirring rod, introduce nitrogen gas, and react at a constant temperature for 1-2 hours. Then continue to heat to the coking temperature of 480-550℃, while introducing nitrogen gas to maintain the pressure in the reactor at 0.2-0.5MPa, and react at a constant temperature for 2-3 hours. Cool to room temperature to obtain an ultrafine mosaic structure isotropic semi-coke. Step S3: Preparation of embedded highly isotropic coke: The ultrafine embedded isotropic semi-coke is heated to 1200-1300℃ in a calcining furnace and held at that temperature for 1-2 hours, and then cooled to obtain embedded highly isotropic coke.

[0008] In a further improvement, the mass ratio of graphene oxide or graphene to organic solvent in the additive dispersion is 1:400-600 g / ml.

[0009] A further improvement is that the graphene oxide or graphene is mixed with an organic solvent and then ultrasonically dispersed to obtain the additive dispersion; the ultrasonic dispersion time is 1-2 hours; the organic solvent is anhydrous ethanol, N,N-dimethylformamide or N-methylpyrrolidone.

[0010] A further improvement is that the temperature at which the intermediate phase is formed is 350-450°C.

[0011] In a further improvement, in step S2, when nitrogen gas is introduced, the nitrogen flow rate is 0.01 to 0.05 L / min.

[0012] In a further improvement, in step S2, the temperature is increased at a rate of 1 to 5 °C / min until the mesophase is formed.

[0013] In a further improvement, in step S3, the temperature is increased to 1200-1300°C at a heating rate of 5-10°C / min.

[0014] A further improvement is that the optical microstructure of the mosaic-type highly isotropic coke is a mosaic structure with a particle size of less than 5 μm and an OTI ≤ 3.

[0015] An application of the above-mentioned mosaic-type highly isotropic coke, characterized in that the mosaic-type isotropic coke is used as an aggregate for preparing isotropic graphite materials.

[0016] Further improvements include the following steps: the embedded highly isotropic coke is poured into a kneader and stirred and heated to 190°C. Molten high-temperature modified coal tar pitch is added and kneaded for 1 hour. The mixture is then cooled to obtain a mixed product. The product is then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The pressed powder is pressed into a green body using a cold isostatic pressing method. The pressing pressure is set to 150 MPa and the holding time is 5 min. The prepared green body is graphitized at 2800°C to prepare an isotropic graphite block. The mass ratio of the embedded highly isotropic coke to the high-temperature modified coal tar pitch is 395:105. The method for preparing high-temperature modified coal tar pitch is as follows: graphene oxide is added to molten asphalt to prepare the tar pitch, and the amount of graphene oxide added is 1% of the mass of molten asphalt.

[0017] The advantages of this invention are as follows: 1. This invention uses widely available and inexpensive coal tar pitch, petroleum pitch, petroleum residue, or heavy oil as raw materials. By adding different amounts of graphene oxide or graphene, the microstructure is regulated. The functional groups of graphene oxide or graphene can combine well with the strongly polar aromatic components containing oxygen-containing groups such as hydroxyl, carboxyl, and carbonyl groups in the raw materials. The active pitch molecules near the graphene oxide or graphene undergo a series of chemical reactions such as decomposition, condensation, and aromatization, which promotes the polymerization between aromatic molecules, improves the pyrolysis reactivity of pitch molecules, and thus shortens the coking induction period and reduces the coking temperature.

[0018] 2. In this invention, graphene oxide or graphene is introduced for co-carbonization during the liquid-phase carbonization process of asphalt components. During the formation of the mesophase in asphalt, graphene oxide or graphene acts as a nucleating agent, effectively promoting the nucleation of mesophase microspheres. Simultaneously, it acts as a separator, preventing the fusion and growth of mesophase microspheres, thus forming an island-like texture. With prolonged carbonization time, the island-like texture gradually evolves into small-diameter mosaic optically anisotropic units in the semi-coke.

[0019] 3. The carbon planes of graphene can induce the growth and stacking of carbon atoms on the graphene surface during the liquid-phase carbonization of asphalt, promoting the ordered arrangement of carbon atoms in the graphene micro-regions and effectively improving the graphitization degree of the prepared coke. The random, disordered dispersion of graphene in molten asphalt or residual oil forms a highly ordered structure within micro-regions and a highly disordered structure over long distances during carbonization. The resulting coke exhibits a macroscopic mosaic-like structure, significantly improving its isotropy. The isotropy and various performance indicators of isotropic graphite materials prepared using the prepared isotropic coke as raw material are greatly improved. Attached Figure Description

[0020] Figure 1 These are polarized light micrographs of coal tar pitch at different temperatures after the addition of graphene oxide. No mesophase was formed at 400℃, but a mesophase was formed at 420℃.

[0021] Figure 2 Polarized light micrographs of coal tar pitch forming semi-coke with different amounts of graphene oxide added.

[0022] Figure 3 Polarized light micrographs of coal tar pitch with varying amounts of graphene oxide added to form mosaic-type highly isotropic coke.

[0023] Figure 4 This is a schematic diagram of the preparation process for embedded highly isotropic coke. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0025] Example 1 A method for preparing a mosaic-type highly isotropic coke includes the following steps: Step S1: Obtain a uniformly mixed molten liquid. (1) 3.6g of graphene oxide was dispersed in 1800ml of anhydrous ethanol solvent and ultrasonically dispersed at room temperature for 1h to obtain an additive dispersion.

[0026] (2) Add the raw material coal tar pitch (purchased from Shandong, see Table 1 for specific composition) into the reactor, heat it to 150℃ at a heating rate of 5℃ / min and keep it at that temperature for 1h; and stir it at a stirring rate of 500rpm.

[0027] (3) Add the additive dispersion slowly in batches to the reactor and continue stirring for 30 minutes to obtain a uniformly mixed molten liquid.

[0028] Table 1 Performance Indicators of Coal Tar Pitch Step S2: Obtain an isotropic half-foil with an ultra-fine mosaic structure. (1) Continue heating at a rate of 10℃ / min to 420℃ to form the mesophase. Figure 1 Meanwhile, the pressure inside the reactor was kept at atmospheric pressure, and the mixture was stirred continuously for 1 hour at a stirring speed of 500 rpm.

[0029] (2) Stop stirring, remove the stirring rod, introduce nitrogen gas at a flow rate of 0.01 L / min, and react at a constant temperature for 8 hours.

[0030] (3) Continue heating to 500℃ at a heating rate of 10℃ / min, while simultaneously introducing nitrogen to maintain the pressure in the reactor at 0.5MPa. React at a constant temperature for 30min, and then cool to room temperature to obtain an ultrafine mosaic structure isotropic semi-coke.

[0031] Step S3: Preparation of embedded highly isotropic coke: The semi-coke obtained in step S2 is heated to 1300℃ in a calcining furnace at a heating rate of 10℃ / min and held for 2 hours, and then cooled to obtain the prepared embedded highly isotropic coke. The optical microstructure is an inlay structure with a particle size of less than 5 μm, such as Figure 3 OTI (Optical Anisotropy Index of Coke) = 2.79; S4. Using the isotropic coke prepared in S3 as aggregate, with D50=10-15μm, and high-temperature modified coal tar pitch as binder, prepare isotropic graphite materials: First, high-temperature modified coal tar pitch is prepared by adding graphene oxide to molten asphalt, with the amount of graphene oxide added being 1% of the mass of the molten asphalt.

[0032] Then, 395g of the isotropic coke prepared in S3 was poured into a kneader and stirred until heated to 190℃. 105g of molten high-temperature modified coal tar pitch was added and kneaded for 1 hour. The mixture was then cooled to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The green body was pressed using a cold isostatic pressing (CIP) method with a pressing pressure of 150MPa and a holding time of 5min. The prepared green body was then graphitized at 2800℃ to prepare isotropic graphite blocks.

[0033] The isotropic graphite bulk material has an anisotropy index of 1.02, a graphitization degree of 88%, a flexural strength of 60 MPa, a resistivity of 13.5 μΩ•m, and a thermal conductivity of 103 W / (K•m).

[0034] Example 2 A method for preparing a mosaic-type highly isotropic coke includes the following steps: Step S1: Obtain a uniformly mixed molten liquid. (1) 3.6g of graphene oxide was dispersed in 1800ml of N,N-dimethylformamide solvent and ultrasonically dispersed at room temperature for 1h to obtain an additive dispersion.

[0035] (2) Add the raw material petroleum asphalt (purchased from Shanghai, see Table 2 for specific composition) into the reactor, heat it to 130℃ at a heating rate of 5℃ / min and keep it at that temperature for 1h; and stir it at a stirring rate of 500rpm.

[0036] Table 2 Performance Indicators of Petroleum Asphalt (3) Add the additive dispersion slowly in batches to the reactor and continue stirring for 30 minutes to obtain a uniformly mixed molten liquid.

[0037] Step S2: Obtain an isotropic half-foil with an ultra-fine mosaic structure. (1) Continue heating to 410℃ at a heating rate of 10℃ / min to form an intermediate phase. At the same time, keep the pressure inside the reactor at atmospheric pressure and stir continuously for 1 hour at a stirring rate of 500 rpm.

[0038] (2) Stop stirring, remove the stirring rod, introduce nitrogen gas at a flow rate of 0.01 L / min, and react at a constant temperature for 8 hours.

[0039] (3) Continue heating to 500℃ at a heating rate of 10℃ / min, while simultaneously introducing nitrogen to maintain the pressure in the reactor at 0.5MPa. React at a constant temperature for 30min, and then cool to room temperature to obtain an ultrafine mosaic structure isotropic semi-coke.

[0040] Step S3: Preparation of embedded highly isotropic coke: The semi-coke obtained in step S2 is heated to 1300°C in a calcining furnace at a heating rate of 10°C / min and held for 2 hours, and then cooled to obtain the prepared embedded highly isotropic coke.

[0041] The optical microstructure is an inlaid structure with a particle size of less than 5 μm and an OTI (Optical Anisotropy Index of Coke) of 2.89.

[0042] S4. Using the isotropic coke prepared in S3 as aggregate, with D50=10-15μm, and high-temperature modified coal tar pitch as binder, prepare isotropic graphite materials: 395g of isotropic coke prepared in S3 was poured into a kneader and stirred until heated to 190°C. 105g of molten high-temperature modified coal tar pitch (same as in Example 1) was added and kneaded for 1 hour. The mixture was then cooled to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The green body was pressed using a cold isostatic pressing (CIP) method with a pressing pressure of 150MPa and a holding time of 5 minutes. The prepared green body was then graphitized at 2800°C to prepare isotropic graphite blocks.

[0043] The isotropic graphite bulk material has an anisotropy index of 1.02, a graphitization degree of 89%, a flexural strength of 58 MPa, a resistivity of 13.1 μΩ•m, and a thermal conductivity of 106 W / (K•m).

[0044] Example 3 A method for preparing a mosaic-type highly isotropic coke includes the following steps: Step S1: Obtain a uniformly mixed molten liquid. (1) 3.6g of graphene was dispersed in 1800ml of N-methylpyrrolidone and ultrasonically dispersed at room temperature for 1h to obtain an additive dispersion.

[0045] (2) Add the raw material petroleum residue oil (purchased from Liaoning, specific composition is shown in Table 3) into the reactor, heat it to 150℃ at a heating rate of 5℃ / min and keep it at that temperature for 1h; and stir it at a stirring rate of 500rpm. Table 3 Performance Indicators of Petroleum Residue Oil (3) Add the additive dispersion slowly in batches to the reactor and continue stirring for 30 minutes to obtain a uniformly mixed molten liquid.

[0046] Step S2: Preparation of an isotropic half-coke with an ultrafine mosaic structure: (1) Continue heating to 420°C at a heating rate of 10°C / min to form an intermediate phase. At the same time, keep the pressure inside the reactor at atmospheric pressure and stir continuously for 1 hour at a stirring rate of 500 rpm.

[0047] (2) Stop stirring, remove the stirring rod, introduce nitrogen gas at a flow rate of 0.01 L / min, and react at a constant temperature for 8 hours.

[0048] (3) Continue heating to 500℃ at a heating rate of 10℃ / min, while simultaneously introducing nitrogen to maintain the pressure in the reactor at 0.5MPa. React at a constant temperature for 30min, and then cool to room temperature to obtain an ultrafine mosaic structure isotropic semi-coke.

[0049] Step S3: Preparation of embedded highly isotropic coke: The semi-coke obtained in step S2 is heated to 1300℃ in a calcining furnace at a heating rate of 10℃ / min and held at that temperature for 0.5 hours, and then cooled to obtain the prepared embedded highly isotropic coke. The optical microstructure is an inlaid structure with a particle size of less than 5 μm and an OTI (Optical Anisotropy Index of Coke) of 2.84.

[0050] S4. Using the isotropic coke prepared in S3 as aggregate, with D50 = 10-15 μm, and high-temperature modified coal tar pitch as binder, prepare isotropic graphite materials: 395g of isotropic coke prepared in S3 was poured into a kneader and stirred until heated to 190℃. 105g of molten high-temperature modified coal tar pitch was added and kneaded for 1 hour. The mixture was then cooled to obtain a mixed product. This product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The green body was pressed using cold isostatic pressing (CIP) at a pressure of 150MPa for 5 minutes. The prepared green body was then graphitized at 2800℃ to prepare isotropic graphite blocks. The isotropic graphite bulk material has an anisotropy index of 1.03, a graphitization degree of 86%, a flexural strength of 54 MPa, a resistivity of 15.58 μΩ•m, and a thermal conductivity of 98 W / (K•m).

[0051] Example 4 A method for preparing a mosaic-type highly isotropic coke includes the following steps: Step S1: Obtain a homogeneous solution. (1) 3.6g of graphene was dispersed in 1800ml of N-methylpyrrolidone and ultrasonically dispersed at room temperature for 1h to obtain an additive dispersion; (2) Add the raw material heavy oil (purchased from Liaoning, specific composition is shown in Table 4) into the reactor, heat it to 120℃ at a heating rate of 5℃ / min and keep it at 1h; and stir it at a stirring rate of 500rpm.

[0052] Table 4 Performance Indicators of Heavy Oil (3) Add the additive dispersion slowly in batches to the reactor and continue stirring for 30 minutes to obtain a uniformly mixed solution. Step S2: Obtain an isotropic half-foil with an ultra-fine mosaic structure. (1) Continue heating to 380°C at a heating rate of 10°C / min to form an intermediate phase, while maintaining atmospheric pressure inside the reactor and stirring continuously for 1 hour at a stirring rate of 500 rpm.

[0053] (2) Stop stirring, remove the stirring rod, introduce nitrogen gas at a flow rate of 0.01 L / min, and react at a constant temperature for 6 hours.

[0054] (3) Continue heating to 500℃ at a heating rate of 10℃ / min, while introducing nitrogen to maintain the pressure in the reactor at 1MPa, react at a constant temperature for 30min, and cool to room temperature to obtain an ultrafine mosaic structure isotropic semi-coke.

[0055] Step S3: Preparation of embedded highly isotropic coke: The semi-coke obtained in step S2 is heated to 1300°C in a calcining furnace at a heating rate of 10°C / min and held for 2 hours, and then cooled to obtain the prepared embedded highly isotropic coke.

[0056] The optical microstructure is an inlaid structure with a particle size of less than 5 μm and an OTI (Optical Anisotropy Index of Coke) of 2.91.

[0057] S4. Using the isotropic coke prepared in S3 as aggregate, with D50=10-15μm, and high-temperature modified coal tar pitch as binder, prepare isotropic graphite materials: The prepared isotropic coke was poured into a kneader and kneaded with high-temperature modified coal tar pitch at 190℃ for 1 hour to obtain a mixed product. Then, it was pulverized twice to obtain pressed powder with a D50 of 10-15 μm. Green bodies were prepared using cold isostatic pressing (CIP) with a forming pressure of 150 MPa and a holding time of 5 min. The prepared green bodies were then graphitized at 2800℃ to prepare isotropic graphite blocks.

[0058] The isotropic graphite bulk material has an anisotropy index of 1.04, a graphitization degree of 85%, a flexural strength of 52 MPa, a resistivity of 15.74 μΩ•m, and a thermal conductivity of 98 W / (K•m).

[0059] Comparative Example 1 A method for preparing coal tar pitch coke includes the following steps: Step S1: Add the raw material coal tar pitch (purchased from Jining Chenxing Carbon Co., Ltd., specific composition is shown in Table 1) into the reactor, heat it to 150℃ at a heating rate of 5℃ / min and keep it at that temperature for 1.5h; and stir it at a stirring rate of 500rpm to obtain a uniformly mixed molten liquid. Step S2, obtaining half-burnt material: (1) Continue heating to 420°C at a heating rate of 10°C / min, while maintaining atmospheric pressure inside the reactor and stirring continuously for 1 hour at a stirring rate of 500 rpm.

[0060] (2) Stop stirring, remove the stirring rod, introduce nitrogen gas at a flow rate of 0.01 L / min, and react at a constant temperature for 8 hours.

[0061] (3) Continue heating to 500℃ at a heating rate of 10℃ / min, while introducing nitrogen to maintain the pressure in the reactor at 0.5MPa, react at a constant temperature for 30min, and cool to room temperature to obtain semi-coke.

[0062] Step S3, preparation of coke: The semi-coke obtained in step S2 is heated to 1300℃ in a calcining furnace at a heating rate of 10℃ / min and held at that temperature for 2 hours, and then cooled to obtain the prepared coke.

[0063] Optical microstructures are large-area, fluid-like structures, such as Figure 3 As shown in (a), the OTI (Optical Anisotropy Index of Coke) is 21.54; Step S4: Using the coke prepared in S3 as aggregate, with D50=10-15μm, and high-temperature modified coal tar pitch as binder, prepare isotropic graphite materials: 395g of coke prepared in S4 was poured into a kneader and stirred until heated to 190℃. 105g of molten high-temperature modified coal tar pitch was added and kneaded for 1 hour. The mixture was then cooled to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The green body was pressed using a cold isostatic pressing (CIP) method with a pressing pressure of 150MPa and a holding time of 5 minutes. The prepared green body was then graphitized at 2800℃ to prepare isotropic graphite blocks.

[0064] The isotropic graphite bulk material has an anisotropy index of 1.15, a graphitization degree of 78%, a flexural strength of 45 MPa, a resistivity of 18.52 μΩ•m, and a thermal conductivity of 87 W / (K•m).

[0065] The data above shows that, compared with Comparative Example 1, the absence of additive dispersion resulted in irregular particle size of the obtained coke structure and excessively high OTI value. Consequently, the flexural strength and thermal conductivity of the isotropic graphite bulk material prepared by this method were lower than those of Example 1, while the anisotropy index and resistivity were higher than those of Example 1. This indicates that the addition of additive dispersion can significantly improve various indicators of the final isotropic graphite bulk material.

[0066] Comparative Example 2 A method for preparing petroleum-based pitch coke includes the following steps: Step S1: Add the raw material petroleum asphalt (same as in Example 2) into the reactor, heat it at a rate of 5℃ / min to 150℃ above the asphalt softening point and keep it at that temperature for 1.5h to obtain a uniformly mixed molten asphalt liquid. Step S2: Obtain petroleum-based pitch semi-coke. (1) Continue heating to 410℃ at a heating rate of 10℃ / min, while maintaining atmospheric pressure inside the reactor and stirring continuously for 1 hour at a stirring rate of 500 rpm.

[0067] (2) Stop stirring, remove the stirring rod, introduce nitrogen gas at a flow rate of 0.01 L / min, and react at a constant temperature for 8 hours.

[0068] (3) Continue heating to 500℃ at a heating rate of 10℃ / min, while introducing nitrogen to maintain the pressure in the reactor at 0.5MPa, react at a constant temperature for 30min, and cool to room temperature to obtain petroleum-based pitch semi-coke; Step S3: The semi-coke obtained in step S2 is heated to 1300℃ in a calcining furnace at a heating rate of 10℃ / min and held at that temperature for 2 hours, and then cooled to obtain the prepared petroleum-based pitch coke. The optical microstructure is a large-area flow-like structure with an OTI (Optical Anisotropy Index of Coke) of 22.76. Step S4: Using the petroleum-based pitch coke prepared in S3 as aggregate (D50 = 10-15 μm) and high-temperature modified coal tar pitch as binder, prepare isotropic graphite materials: 395g of coke prepared in S4 was poured into a kneader and stirred until heated to 190℃. 105g of molten high-temperature modified coal tar pitch was added and kneaded for 1 hour. The mixture was then cooled to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The green body was pressed using a cold isostatic pressing (CIP) method with a pressing pressure of 150MPa and a holding time of 5 minutes. The prepared green body was then graphitized at 2800℃ to prepare isotropic graphite blocks.

[0069] The isotropic graphite bulk material has an anisotropy index of 1.20, a graphitization degree of 85%, a flexural strength of 42 MPa, a resistivity of 16.6 μΩ•m, and a thermal conductivity of 90 W / (K•m).

[0070] As can be seen from the above data, compared with Example 2, the absence of additive dispersion resulted in the coke structure exhibiting a large area of ​​flow domains at the microscopic level and a very high OTI value. Consequently, the flexural strength and thermal conductivity of the isotropic graphite bulk material prepared by this method were lower than those of Example 2, while the anisotropy index and resistivity were higher. This indicates that the addition of additive dispersion can significantly improve the various performance indicators of the final isotropic graphite bulk material.

[0071] Comparative Example 3 Using the coke prepared in Comparative Example 1 as aggregate with D50 = 10-15 μm, and commercially available coal tar pitch as binder, isotropic graphite materials were prepared: 395g of the coke prepared in Comparative Example 1 was poured into a kneader and stirred until heated to 190°C. 105g of molten ordinary commercial coal tar pitch was added and kneaded for 1 hour. The mixture was then cooled to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain a pressed powder. The green body was pressed using a cold isostatic pressing (CIP) method with a pressing pressure of 150MPa and a holding time of 5 minutes. The prepared green body was then graphitized at 2800°C to prepare an isotropic graphite block.

[0072] The isotropic bulk graphite material has an anisotropy index of 1.18, a graphitization degree of 76%, a flexural strength of 42 MPa, a resistivity of 20.3 μΩ•m, and a thermal conductivity of 83 W / (K•m). Compared with Comparative Example 1, Comparative Example 3 showed that the anisotropy index and resistivity of the isotropic graphite bulk material were higher than those of Comparative Example 1, while the thermal conductivity and flexural strength were lower than those of Comparative Example 1. This indicates that high-temperature modified coal tar pitch has the effect of reducing the anisotropy index, increasing the degree of graphitization, improving the flexural strength and thermal conductivity, and reducing the resistivity.

[0073] Comparative Example 4 Isotropic graphite material was prepared using isotropic coke prepared in Example 1 as aggregate (D50 = (10-15) μm) and commercially available coal tar pitch as binder. 395g of the isotropic coke prepared in Example 1 was poured into a kneader and kneaded with 105g of commercially available coal tar pitch at 190°C for 1 hour to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. Green bodies were prepared using cold isostatic pressing (CIP) with a molding pressure of 150 MPa and a holding time of 5 min. The prepared green bodies were then graphitized at 2800°C to prepare isotropic graphite blocks.

[0074] The isotropic graphite bulk material has an anisotropy index of 1.08, a graphitization degree of 80%, a flexural strength of 52 MPa, a resistivity of 16.2 μΩ•m, and a thermal conductivity of 98 W / (K•m).

[0075] This comparative example further demonstrates that high-temperature modified coal tar pitch can reduce the anisotropy index, increase the degree of graphitization, improve flexural strength and thermal conductivity, and reduce resistivity.

[0076] Comparative Example 5 Isotropic graphite materials were prepared using isotropic coke purchased from Shanghai Baowu as aggregate (D50 = (10-15) μm) and high-temperature modified coal tar pitch as binder. 395g of the isotropic coke was poured into a kneader and kneaded with 105g of high-temperature modified coal tar pitch at 190℃ for 1 hour to obtain a mixed product. The product was then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. Green bodies were prepared using cold isostatic pressing (CIP) with a molding pressure of 150MPa and a holding time of 5min. The prepared green bodies were then graphitized at 2800℃ to prepare isotropic graphite blocks.

[0077] The isotropic graphite bulk material has an anisotropy index of 1.06, a graphitization degree of 81%, a flexural strength of 55 MPa, a resistivity of 15.58 μΩ•m, and a thermal conductivity of 100 W / (K•m).

[0078] This comparative example further demonstrates that the additive dispersion can reduce the anisotropy index, increase the degree of graphitization, and improve the flexural strength. It can also improve the thermal conductivity, but the effect is not significant (less than 5%).

[0079] The embodiments described herein merely illustrate a few possible embodiments of this patent application, and their level of detail should not be construed as limiting the scope of the patent. Those skilled in the art will be able to implement various modifications and alterations without departing from the fundamental principles of this application. Therefore, the scope of protection of this application should be based on the claims.

Claims

1. A method for preparing a mosaic-type highly isotropic coke, characterized in that, Includes the following steps: Step S1: Prepare the additive dispersion by heating the raw material to 50-60°C above its softening point and holding it at that temperature. Then, mix the additive dispersion with the raw material to obtain a uniformly mixed molten raw material. The additive dispersion is an organic solvent dispersion of graphene oxide or an organic solvent dispersion of graphene; the raw material is coal tar pitch, petroleum pitch, petroleum residue oil or heavy oil. Step S2: Heat the molten raw material to the temperature at which the mesophase is formed, and stir continuously for 0.5-1 hour. Then stop stirring, remove the stirring rod, introduce nitrogen gas, and react at a constant temperature for 1-2 hours. Then continue to heat to the coking temperature of 480-550℃, while introducing nitrogen gas to maintain the pressure in the reactor at 0.2-0.5MPa, and react at a constant temperature for 2-3 hours. Cool to room temperature to obtain an ultrafine mosaic structure isotropic semi-coke. Step S3: Preparation of embedded highly isotropic coke: The ultrafine embedded isotropic semi-coke is heated to 1200-1300℃ in a calcining furnace and held at that temperature for 1-2 hours, and then cooled to obtain embedded highly isotropic coke.

2. The method for preparing the embedded highly isotropic coke as described in claim 1, characterized in that, The mass ratio of graphene oxide or graphene to organic solvent in the additive dispersion is 1:400-600 g / ml.

3. The method for preparing the embedded highly isotropic coke as described in claim 1, characterized in that, The additive dispersion is obtained by ultrasonic dispersion of graphene oxide or graphene mixed with an organic solvent; the ultrasonic dispersion time is 1-2 hours; the organic solvent is anhydrous ethanol, N,N-dimethylformamide or N-methylpyrrolidone.

4. The method for preparing the embedded highly isotropic coke as described in claim 1, characterized in that, The temperature at which the intermediate phase is formed is 350-450℃.

5. The method for preparing the embedded highly isotropic coke as described in claim 1, characterized in that, In step S2, when nitrogen gas is introduced, the nitrogen flow rate is 0.01 to 0.05 L / min.

6. The method for preparing the embedded highly isotropic coke as described in claim 1, characterized in that, In step S2, the temperature is increased at a rate of 1 to 15 °C / min until the mesophase is formed.

7. The method for preparing the embedded highly isotropic coke as described in claim 1, characterized in that, In step S3, the temperature is increased to 1200-1300℃ at a heating rate of 5-10℃ / min.

8. The method for preparing the mosaic-type highly isotropic coke as described in any one of claims 1-7, characterized in that, The optical microstructure of the mosaic-type highly isotropic coke is a mosaic structure with a particle size of less than 5 μm and an OTI ≤ 3.

9. The application of the embedded highly isotropic coke as described in any one of claims 1-7, characterized in that, The mosaic isotropic coke is used as aggregate for preparing isotropic graphite materials.

10. The application of the embedded highly isotropic coke as described in claim 9, characterized in that, The process includes the following steps: the embedded highly isotropic coke is poured into a kneader and stirred and heated to 190°C. Molten high-temperature modified coal tar pitch is added and kneaded for 1 hour. The mixture is then cooled to obtain a mixed product. The product is then pulverized twice and passed through a 100-mesh sieve to obtain pressed powder. The pressed powder is pressed into a green body using a cold isostatic pressing method. The pressing pressure is set to 150 MPa and the holding time is 5 min. The prepared green body is then graphitized at 2800°C to prepare an isotropic graphite block. The mass ratio of the embedded highly isotropic coke to the high-temperature modified coal tar pitch is 395:

105. The method for preparing high-temperature modified coal tar pitch is as follows: graphene oxide is added to molten asphalt to prepare the tar pitch, and the amount of graphene oxide added is 1% of the mass of molten asphalt.

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