Coal-based mesophase pitch and method for producing the same

Abstract

The present application provides a kind of coal-based mesophase pitch and its preparation method, belong to pitch preparation technical field.The preparation method includes the following steps: coal-based raw pitch is pretreated, and refined coal pitch is obtained;Distillation is carried out on refined coal pitch, and distillation coal pitch is obtained;Heat polycondensation reaction is carried out on distillation coal pitch, and coal-based mesophase pitch is obtained.The present application uses single coal-based raw pitch as raw material, with the help of the combination of pure physical purification of refining-distillation, cooperatively removes impurities and controls material composition, reduces the quinoline insoluble content of coal pitch to below 0.1wt%.On this basis, through non-catalytic heat polycondensation reaction, the mesophase conversion rate is significantly improved, and the performance consistency of the obtained product as carbon material precursor is improved.The process is simple, controllable, energy-saving and cost-effective, which provides a reliable technical path for the high-value utilization of coal tar pitch and the large-scale stable production of high-end carbon materials.

Description

Technical Field

[0001] This invention belongs to the field of bitumen preparation technology, specifically relating to a coal-series mesophase bitumen and its preparation method. Background Technology

[0002] Mesophase pitch is a liquid crystal-like substance formed during thermal conversion and is a core precursor for the preparation of high-performance carbon materials. Its formation essentially involves the pyrolysis and condensation reaction of coal tar pitch under heat treatment conditions. Polycyclic aromatic hydrocarbon molecules grow planarly through dehydrogenation, condensation, and other chemical reactions. When the molecular size reaches 1.0-3.0 nm, they are directionally stacked under the drive of π-π intermolecular forces, forming a disk-shaped liquid crystal structure with optical anisotropy. This unique mesophase structure makes it an ideal precursor for manufacturing high-end carbon materials.

[0003] Mesophase pitch mainly originates from heavy aromatic hydrocarbon feedstocks such as coal tar pitch and petroleum pitch. Traditional preparation processes primarily employ thermal polycondensation, precisely controlling the heat treatment temperature (380-450°C) and reaction time (typically 5-15 h) under an inert atmosphere. This allows isotropic pitch to undergo stages of thermal decomposition, molecular polycondensation, and liquid crystal phase development, ultimately transforming it into an anisotropic mesophase. Modern preparation techniques introduce new methods such as catalytic polymerization (e.g., using catalysts like AlCl3 and HF / BF3) and solvent extraction purification. By promoting the directional alignment of aromatic molecules, these methods significantly improve the mesophase content and optical texture quality.

[0004] With its unique molecular orientation characteristics and high carbonization yield (typically >85%), this material demonstrates irreplaceable application value in high-tech fields such as aerospace (missile nose cones, rocket nozzles), new energy (lithium-ion battery anode materials, fuel cell bipolar plates), and electronic packaging (chip heat dissipation substrates).

[0005] The current development of coal-based mesophase pitch material preparation technology still faces three major bottlenecks: First, it is difficult to control the purity of raw materials, and the content of quinoline insolubles (QI) is difficult to keep below 0.1%, which affects the orderly development of the mesophase; second, the thermodynamic and kinetic control precision in the mesophase formation process is insufficient, resulting in non-uniform optical texture and molecular orientation, and large fluctuations in product performance; finally, the process has high energy consumption and high production costs.

[0006] Coal tar pitch, a byproduct of coal chemical industry, is mainly composed of polycyclic aromatic hydrocarbons with three or more rings, and has a carbon content as high as 90-94%. Its hydrogen-to-carbon atomic ratio (H / C) is typically between 0.5 and 0.7. This unique molecular structure provides favorable conditions for the formation of the mesophase during its thermal conversion. Compared with petroleum-based pitch, coal tar pitch has higher aromaticity and better molecular planarity, making it easier to obtain mesophase pitch with a wide-area streamlined optical texture through heat treatment.

[0007] Currently, the main method for preparing mesophase pitch from coal tar pitch is a combined thermal polycondensation-solvent refining process. This process first reduces the amount of native quinoline insolubles in the raw materials through pretreatment, followed by programmed temperature heating under an inert atmosphere. Precise control of the reaction temperature (typically 390-430°C), pressure (atmospheric or slightly positive pressure), and residence time promotes the stepwise dehydrogenation polycondensation of aromatic molecules, forming and developing the mesophase. During the reaction, parameters such as system viscosity and gas phase escape need precise control to ensure the smooth nucleation, growth, and fusion of mesophase spheres. However, this technology still faces key challenges: the complex chemical composition and wide molecular weight distribution of coal tar pitch result in significant differences in reactivity, leading to low mesophase conversion rates (typically <60%); excessive polycondensation easily occurs during heat treatment, generating isotropic regions and mosaic structures, and the quinoline insoluble content fluctuates greatly (0.5-3%), severely affecting the performance of subsequent carbon materials. Furthermore, existing processes suffer from high energy consumption and difficulties in solvent recovery, hindering large-scale production.

[0008] In recent years, the introduction of new technologies such as catalytic polymerization, hydrogen donor modification, and mesophase seeding has made it possible to overcome these bottlenecks. These methods, by adjusting the reaction pathway and promoting the ordered arrangement of molecules, are expected to improve the content and quality of mesophase. However, how to achieve stable preparation with low cost and high content (>85%) remains a key challenge for industrialization.

[0009] Therefore, providing a method for preparing coal-based mesophase pitch that can effectively reduce QI content, improve mesophase conversion rate and optical texture quality, and reduce costs, so as to realize the high-value utilization of coal chemical by-products, is a hot research topic that urgently needs to be studied. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a coal-based mesophase pitch and its preparation method. This invention uses coal-based pitch as a single raw material, employing a purely physical purification combination of "refining-distillation" to synergistically remove impurities and regulate the material composition, reducing the quinoline insoluble content of the coal pitch to below 0.1 wt%, providing a high-purity, homogeneous precursor for subsequent reactions. Based on this, a significant improvement in mesophase conversion rate is achieved through a non-catalytic thermal polycondensation reaction, resulting in an anisotropic optical state and significantly enhancing the performance consistency of the obtained product as a carbon material precursor. Furthermore, the entire process utilizes a non-catalytic process of entirely physical purification and precise thermal control, avoiding impurities introduced by catalysts and subsequent processing challenges. It boasts significant advantages such as simple process, strong controllability, and low energy consumption and cost, providing a reliable technical path for the high-value utilization of coal tar pitch and the large-scale, stable production of high-end carbon materials.

[0011] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing coal-series mesophase pitch, the method comprising the following steps: Refined coal tar pitch is obtained by pretreating coal-based raw material tar pitch.

[0012] The refined coal tar pitch is distilled to obtain distilled coal tar pitch.

[0013] The distilled coal tar pitch is subjected to a thermal polycondensation reaction to obtain the coal-based mesophase pitch.

[0014] This invention uses a single coal-based bitumen as raw material, avoiding the compatibility risks associated with differences in molecular structure and heteroatom content among multiple raw materials. It ensures consistent reactivity, facilitates synergistic transformation during thermal polycondensation, and promotes the formation of a uniform and regular mesophase structure, thus improving product performance stability. In contrast, introducing bitumen from other sources, such as biomass bitumen, results in poor system compatibility, easily leading to phase separation, asynchronous reactions, optical texture embedding, structural defects, and impurities. This significantly reduces the quality controllability and consistency of the mesophase bitumen and subsequent carbon materials.

[0015] Preferably, the pretreatment includes sequential crushing, dissolving, and solid-liquid separation.

[0016] Preferably, the solvent used in the dissolution process is a composite organic solvent.

[0017] Preferably, the composite organic solvent includes quinoline, and at least one of pyridine, toluene, benzene, wash oil, tetrahydrofuran, petroleum ether, gasoline, n-hexane, n-pentane, or n-heptane.

[0018] In this invention, when dissolving coal-based raw material pitch using a composite organic solvent, quinoline is selected as one of the composite organic solvents and synergistically combined with at least one of pyridine, toluene, benzene, wash oil, tetrahydrofuran, petroleum ether, gasoline, n-hexane, n-pentane, or n-heptane. Utilizing the superior solubility of quinoline for polycyclic aromatic hydrocarbons and the differences in polarity, boiling point, and selectivity between quinoline and other solvents, a refining system with gradient dissolution characteristics is constructed. This composite solvent system not only efficiently dissolves the target aromatic hydrocarbon components but also achieves deep removal of QI from the raw material through the selective dissolution and precipitation of aromatic hydrocarbons of different molecular weights. This provides a reaction precursor with more uniform molecular size and more controllable active sites for subsequent thermal polycondensation reactions, which is beneficial for obtaining high-quality mesophase pitch with optical anisotropy and high mesophase content.

[0019] It should be noted that wash oil refers to a specific fraction distilled from coal tar or coal pitch during processing, within a temperature range of 230℃ to 300℃. Its main components are bicyclic and tricyclic aromatic hydrocarbons and heterocyclic compounds, typical components including but not limited to: naphthalene, methylnaphthalene, quinoline, indole, fluorene, oxyfluorene, acenaphthene, etc. This fraction is named "wash oil" because of its excellent absorption and dissolution properties for organic vapors (especially benzene compounds and naphthalene). For example, it can be wash oil conforming to the national standard GB / T24217-2025.

[0020] Preferably, the volume percentage of quinoline in the composite organic solvent is 30-70%, for example, it can be 30%, 40%, 50%, 60% or 70%.

[0021] In this invention, the volume percentage of quinoline is 30-70%, ensuring that quinoline dominates the composite organic solvent system and can fully exert its strong dissolving ability for heavy aromatic components, preventing insufficient dissolution of target components due to excessively low quinoline content; at the same time, by synergistically with other solvents, the polarity and volatility of the composite organic solvent are controlled, achieving the optimal extraction and separation effect of coal-based raw material pitch.

[0022] Preferably, the dissolution temperature is 40~160°C, for example, 40°C, 80°C, 120°C or 160°C, and the time is 0.5~6h, for example, 0.5h, 1h, 2h, 3h, 4h, 5h or 6h.

[0023] Preferably, the mass ratio of the coal-based raw material pitch to the composite organic solvent is 1:(1~3), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0024] Preferably, the solid-liquid separation temperature is 60~200°C, for example, it can be 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, and the processing time is 12~24h, for example, it can be 12h, 16h, 20h or 24h.

[0025] Preferably, the solid-liquid separation method includes filtration or sedimentation.

[0026] Preferably, the distillation method includes atmospheric distillation and / or vacuum distillation.

[0027] Preferably, the distillation temperature is 160~360°C, for example, 160°C, 200°C, 250°C, 300°C or 360°C, and the time is 10~30min, for example, 10min, 15min, 20min, 25min or 30min.

[0028] Preferably, the quinoline insoluble content of the distilled coal tar pitch is ≤0.03wt%, for example, it can be 0.03wt%, 0.02wt%, or 0.01wt%.

[0029] The quinoline-insoluble matter content of the distilled coal tar pitch obtained by this invention is ≤0.03wt%, indicating that a deep purification of raw material impurities is achieved through a physical combination purification process of "refining-distillation". As a precursor to the thermal polycondensation reaction, it can not only significantly improve the conversion efficiency of the mesophase, but also fundamentally promote the homogeneous nucleation and orderly fusion of liquid crystal domains in the reaction system, thus laying the foundation for finally obtaining mesophase pitch with highly consistent texture and excellent performance.

[0030] Preferably, an inert gas is introduced during the thermal polycondensation reaction. For example, it can be nitrogen or argon.

[0031] Preferably, the temperature of the thermal polycondensation reaction is 380~450°C, for example, it can be 380°C, 400°C, 420°C or 450°C.

[0032] Preferably, the thermal polycondensation reaction takes 4 to 24 hours, for example, 4 hours, 8 hours, 10 hours, 15 hours, 20 hours, or 24 hours.

[0033] Preferably, the pressure of the thermal polycondensation reaction is 0~5MPa, for example, it can be 0.1MPa, 0.5MPa, 1MPa, 2MPa, 3MPa, 4MPa or 5MPa, etc.

[0034] Preferably, the thermopolymerization reaction includes a low-pressure stage and a high-pressure stage performed sequentially.

[0035] During the low-pressure stage, the pressure is -0.05 to -0.1 MPa, for example, it can be -0.05 MPa, -0.06 MPa, -0.07 MPa, -0.08 MPa, -0.09 MPa, -0.1 MPa, etc., the constant temperature is 300 to 380°C, for example, it can be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, or 380°C, etc., and the constant temperature time is 2 to 4 hours, for example, it can be 2 hours, 3 hours, or 4 hours, etc.

[0036] During the high-pressure stage, the pressure is 1.5~3.5MPa, for example, it can be 1.5MPa, 2MPa, 2.5MPa, 3MPa or 3.5MPa, etc., the constant temperature is 400~450°C, for example, it can be 400°C, 410°C, 420°C, 430°C, 440°C or 450°C, etc., and the constant temperature time is 4~8h, for example, it can be 4h, 5h, 6h, 7h or 8h, etc.

[0037] This invention employs a low-pressure-high-pressure segmented thermal polycondensation process. In the low-pressure stage, residual light components and small molecule gases generated in the reaction are removed from the system to avoid interference with the nucleation and growth of mesophase microspheres, creating a favorable environment for the initial growth of the liquid crystal phase. In the high-pressure stage, sufficient energy and intermolecular forces are provided to the system to strongly drive the further orientation, orderly stacking, and full fusion of polycyclic aromatic hydrocarbons and microspheres. This achieves precise guidance of the mesophase formation path at the molecular scale, ultimately yielding high-quality mesophase asphalt.

[0038] Preferably, the preparation method includes the following steps: (1) Preparation of refined coal tar pitch, the specific steps include: (a) The coal-based raw material pitch is crushed and sieved to obtain a crushed raw material with a particle size D50 of 20~50μm (e.g., it can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm, etc.).

[0039] (b) The pulverized raw material and the composite organic solvent are mixed and dissolved at 40-160°C and 100-600 rpm for 0.5-6 hours to obtain a coal tar pitch mixture; the composite organic solvent includes quinoline and at least one of pyridine, toluene, benzene, wash oil, tetrahydrofuran, petroleum ether, gasoline, n-hexane, n-pentane or n-heptane; the volume percentage of quinoline in the composite organic solvent is 30-70%; the mass ratio of the coal-based raw material pitch to the composite organic solvent is 1:(1-3).

[0040] (c) The coal tar pitch mixture is filtered or settled at a temperature of 60~200°C for 12~24 hours to obtain the refined coal tar pitch.

[0041] (2) The refined coal tar pitch is heated to 160-360°C at a heating rate of 2-5°C / min (e.g., 2°C / min, 3°C / min, 4°C / min or 5°C / min, etc.) for 10-30 min to obtain distilled coal tar pitch with a quinoline insoluble content ≤0.03wt%.

[0042] (3) The distilled coal tar pitch is placed in a reaction vessel, and an inert gas is introduced as a protective gas at a flow rate of 1~10 L / min (e.g., 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, or 10 L / min, etc.). A low-pressure stage thermal polycondensation reaction is carried out for 2~4 hours at a pressure of -0.05~-0.1 MPa and a temperature of 300~380°C. Then the pressure is increased to 1.5~3.5 MPa, and the flow rate is increased to 1~10°C / min (e.g., 1°C / min, etc.). The temperature is increased to 400-450°C at a heating rate of 10°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, etc., and then subjected to a high-pressure stage thermal condensation reaction for 4-8 hours. After the reaction, the temperature is programmed to decrease to 200-300°C (e.g., 200°C, 250°C, or 300°C, etc.), and then allowed to cool naturally to 20-50°C (e.g., 20°C, 30°C, 40°C, or 50°C, etc.), to obtain coal-based mesophase pitch.

[0043] In a second aspect, the present invention provides a coal-based mesophase pitch, which is prepared by the preparation method described in the first aspect.

[0044] The coal-bearing mesophase pitch is in a liquid crystal state; the optical state of the coal-bearing mesophase pitch exhibits anisotropy.

[0045] Preferably, the coking value of the coal-series mesophase pitch is 60-85%, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C or 85°C.

[0046] Preferably, the C / H ratio of the coal-series mesophase pitch is 1.3 to 1.6, for example, it can be 1.3, 1.4, 1.5 or 1.6.

[0047] Preferably, the mesophase content of the coal-series mesophase pitch is 50-98%, for example, it can be 50%, 60%, 70%, 80%, 90% or 98%, etc.

[0048] Preferably, the softening point of the coal-series mesophase pitch is 260~320°C, for example, it can be 260°C, 270°C, 280°C, 290°C, 300°C, 310°C or 320°C.

[0049] The above parameters demonstrate that this invention produces coal-based mesophase pitch with excellent comprehensive properties. Specifically, the high coking value of 60-85% ensures high yield and dimensional stability during the carbonization process; the suitable C / H ratio of 1.3-1.6 reflects a moderate degree of molecular condensation and an ideal level of aromatization, providing a molecular structural basis for the efficient formation of the mesophase; the wide range of mesophase content of 50-98% covers the requirements from general-purpose to ultra-high-performance grades; and the softening point of 260-320°C endows the material with excellent thermoplasticity and a suitable processing window. These performance parameters work synergistically to ensure that the coal-based mesophase pitch prepared by this invention, as a precursor, can meet the stringent requirements ranging from general-purpose graphite materials to high-end carbon products (such as carbon fiber and carbon foam).

[0050] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0051] Compared with the prior art, the present invention has the following beneficial effects: This invention uses coal tar pitch as a single raw material and employs a purely physical purification process of "refining-distillation" to synergistically remove impurities and regulate the material composition, reducing the quinoline insoluble content of coal tar pitch to below 0.1 wt%, providing a high-purity, homogeneous precursor for subsequent reactions. Based on this, a non-catalytic thermal polycondensation reaction significantly improves the conversion rate of the mesophase and forms an anisotropic optical state, significantly enhancing the performance consistency of the resulting product as a carbon material precursor. Furthermore, the entire process utilizes a non-catalytic process of fully physical purification and precise thermal control, avoiding impurities introduced by catalysts and subsequent processing challenges. It boasts significant advantages such as simple process, strong controllability, and low energy consumption and cost, providing a reliable technical path for the high-value utilization of coal tar pitch and the large-scale, stable production of high-end carbon materials. Attached Figure Description

[0052] Figure 1 This is a polarized light microscope image of coal-bearing mesophase pitch provided in Example 2 of the present invention. Detailed Implementation

[0053] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0054] Example 1 This embodiment provides a method for preparing coal-series mesophase pitch, the method comprising the following steps: (1) Preparation of refined coal tar pitch, the specific steps include: (a) The coal tar pitch is crushed and sieved to obtain a crushed raw material with a particle size D50 of 35 μm.

[0055] (b) The pulverized raw material and the composite organic solvent are mixed and dissolved at 100°C and 350 rpm for 1 hour to obtain a coal tar pitch mixture; the composite organic solvent includes quinoline and pyridine; the volume percentage of quinoline in the composite organic solvent is 50%; the mass ratio of the coal tar pitch to the composite organic solvent is 1:2.

[0056] (c) The coal tar pitch mixture is filtered and separated using a thermal filter at a temperature of 130°C for 18 hours to obtain the refined coal tar pitch.

[0057] (2) The refined coal tar pitch was heated to 260°C at a heating rate of 3°C / min and subjected to vacuum distillation for 20 min to obtain distilled coal tar pitch with a quinoline insoluble content of 0.01 wt%.

[0058] (3) The distilled coal tar pitch was placed in a reaction vessel and nitrogen gas was introduced at a flow rate of 5 L / min as a protective gas. The thermal polycondensation reaction was carried out for 24 hours at 0.5 MPa and 400°C. After the reaction was completed, the temperature was programmed to drop to 250°C and then naturally cooled to 30°C to obtain coal-based mesophase pitch.

[0059] This embodiment also provides a coal-based mesophase pitch, which is prepared by the preparation method described above.

[0060] The coal-based mesophase pitch is in a liquid crystal state; the optical state of the coal-based mesophase pitch exhibits anisotropy; the coking value of the coal-based mesophase pitch is 75%; the C / H ratio of the coal-based mesophase pitch is 1.35; the mesophase content of the coal-based mesophase pitch is 80%; and the softening point of the coal-based mesophase pitch is 260°C.

[0061] Example 2 This embodiment provides a method for preparing coal-series mesophase pitch, the method comprising the following steps: (1) Preparation of refined coal tar pitch, the specific steps include: (a) The coal tar pitch is crushed and sieved to obtain a crushed raw material with a particle size D50 of 20 μm.

[0062] (b) The pulverized raw material and the composite organic solvent are mixed and dissolved at 50°C and 600 rpm for 3 hours to obtain a coal tar pitch mixture; the composite organic solvent includes quinoline and wash oil; the volume percentage of quinoline in the composite organic solvent is 70%; the mass ratio of the coal tar pitch to the composite organic solvent is 1:1.

[0063] (c) The coal tar pitch mixture is filtered and separated using a thermal filter at a temperature of 60°C for 24 hours to obtain the refined coal tar pitch.

[0064] (2) The refined coal tar pitch was heated to 160°C at a heating rate of 3°C / min and subjected to vacuum distillation for 30 min to obtain distilled coal tar pitch with a quinoline insoluble content of 0.02 wt%.

[0065] (3) The distilled coal tar pitch was placed in a reaction vessel and nitrogen gas was introduced at a flow rate of 5 L / min as a protective gas. The thermal polycondensation reaction was carried out for 24 hours at 0.5 MPa and 430°C. After the reaction was completed, the temperature was programmed to drop to 200°C and then naturally cooled to 20°C to obtain coal-based mesophase pitch.

[0066] This embodiment also provides a coal-bearing mesophase pitch, the polarized light microscope image of which is shown below. Figure 1 As shown, the coal-series mesophase pitch is prepared using the preparation method described above.

[0067] The coal-based mesophase pitch is in a liquid crystal state; the optical state of the coal-based mesophase pitch exhibits anisotropy; the coking value of the coal-based mesophase pitch is 72%; the C / H ratio of the coal-based mesophase pitch is 1.52; the mesophase content of the coal-based mesophase pitch is 95%; and the softening point of the coal-based mesophase pitch is 300°C.

[0068] Example 3 This embodiment provides a method for preparing coal-series mesophase pitch, the method comprising the following steps: (1) Preparation of refined coal tar pitch, the specific steps include: (a) The coal tar pitch is crushed and sieved to obtain a crushed raw material with a particle size D50 of 50 μm.

[0069] (b) The pulverized raw material and the composite organic solvent are mixed and dissolved at 80°C and 100 rpm for 6 hours to obtain a coal tar pitch mixture; the composite organic solvent includes quinoline and n-pentane; the volume percentage of quinoline in the composite organic solvent is 30%; the mass ratio of the coal tar pitch to the composite organic solvent is 1:3.

[0070] (c) The coal tar pitch mixture is filtered and separated using a thermal filter at 200°C for 12 hours to obtain the refined coal tar pitch.

[0071] (2) The refined coal tar pitch was heated to 360°C at a heating rate of 3°C / min and subjected to vacuum distillation for 10 min to obtain distilled coal tar pitch with a quinoline insoluble content of 0.02wt%.

[0072] (3) The distilled coal tar pitch was placed in a reaction vessel and nitrogen gas was introduced at a flow rate of 5 L / min as a protective gas. The thermal polycondensation reaction was carried out at 0.5 MPa and 430°C for 4 hours. After the reaction was completed, the temperature was gradually reduced to 250°C and then naturally reduced to 40°C to obtain coal-based mesophase pitch.

[0073] This embodiment also provides a coal-based mesophase pitch, which is prepared by the preparation method described above.

[0074] The coal-based mesophase pitch is in a liquid crystal state; the optical state of the coal-based mesophase pitch exhibits anisotropy; the coking value of the coal-based mesophase pitch is 80%; the C / H ratio of the coal-based mesophase pitch is 1.43; the mesophase content of the coal-based mesophase pitch is 90%; and the softening point of the coal-based mesophase pitch is 320°C.

[0075] Example 4 The difference between this embodiment and Embodiment 1 is that the thermal polycondensation reaction in step (3) is replaced by the following steps: The low-pressure stage thermal polycondensation reaction was carried out for 3 hours at a pressure of -0.05 MPa and a temperature of 340°C. Then, the pressure was increased to 2.5 MPa and the temperature was increased to 420°C at a heating rate of 5°C / min for 6 hours of high-pressure stage thermal polycondensation reaction.

[0076] The remaining preparation methods and parameters are consistent with those in Example 1.

[0077] Example 5 The difference between this embodiment and Embodiment 1 is that the composite organic solvent is replaced with wash oil (GB / T 24217-2025) and gasoline (GB 17930-2016, National VIB 95 gasoline standard), wherein the volume ratio of wash oil is 50%.

[0078] The remaining preparation methods and parameters are consistent with those in Example 1.

[0079] Example 6 The difference between this embodiment and Embodiment 1 is that the volume percentage of quinoline in the composite organic solvent is 25%.

[0080] The remaining preparation methods and parameters are consistent with those in Example 1.

[0081] Example 7 The difference between this embodiment and Embodiment 1 is that quinoline accounts for 75% of the volume in the composite organic solvent.

[0082] The remaining preparation methods and parameters are consistent with those in Example 1.

[0083] Example 8 The difference between this embodiment and embodiment 1 is that, in the process of the thermal polycondensation reaction described in step (3), the temperature is first raised to 300°C under constant pressure, and then raised to 410°C.

[0084] The remaining preparation methods and parameters are consistent with those in Example 1.

[0085] Example 9 The difference between this embodiment and embodiment 4 is that the temperature in the low-pressure stage thermal polycondensation reaction is the same as that in the high-pressure stage thermal polycondensation reaction, which is 400°C.

[0086] The remaining preparation methods and parameters are consistent with those in Example 4.

[0087] Comparative Example 1 The difference between this comparative example and Example 1 is that step (1) is omitted.

[0088] The remaining preparation methods and parameters are consistent with those in Example 1.

[0089] Comparative Example 2 The difference between this comparative example and Example 1 is that step (2) is omitted.

[0090] The remaining preparation methods and parameters are consistent with those in Example 1.

[0091] Performance testing The quinoline insoluble content of the distilled coal tar pitch provided in the above examples and comparative examples was tested according to GB / T 2293-2019.

[0092] The coking values ​​of the coal-series mesophase pitch prepared according to the above embodiments and comparative examples were tested in accordance with GB / T 8727-2008.

[0093] The C / H ratio of the coal-series mesophase pitch prepared in the above examples and comparative examples was tested using an elemental analyzer.

[0094] The mesophase content of the coal-series mesophase pitch prepared in the above examples and comparative examples was tested using a polarizing microscope.

[0095] The softening point of the coal-based mesophase pitch prepared in the above embodiments and comparative examples was tested using a thermomechanical analyzer.

[0096] The test results are shown in Table 1.

[0097] Table 1

[0098] analyze: As shown in Table 1, this invention uses coal tar pitch as a single raw material and employs a purely physical purification process of "refining-distillation" to synergistically remove impurities and regulate the material composition, reducing the quinoline insoluble content of coal tar pitch to below 0.1 wt%, thus providing a high-purity, homogeneous precursor for subsequent reactions. Based on this, a significant improvement in the conversion rate of the mesophase is achieved through a non-catalytic thermal polycondensation reaction, resulting in an anisotropic optical state and significantly enhancing the performance consistency of the obtained product as a carbon material precursor. Furthermore, the entire process utilizes a non-catalytic process of fully physical purification and precise thermal control, avoiding impurities introduced by catalysts and subsequent processing challenges. It boasts significant advantages such as simple process, strong controllability, and low energy consumption and cost, providing a reliable technical path for the high-value utilization of coal tar pitch and the large-scale, stable production of high-end carbon materials.

[0099] As can be seen from the comparison between Example 1 and Example 5, if a combination of wash oil and gasoline is used, compared with the combination of quinoline and pyridine, its solubility for heavy aromatic components is insufficient, resulting in a significant reduction in QI removal efficiency and difficulty in achieving effective narrowing of molecular weight distribution. Ultimately, this leads to a decrease in the content of the mesophase and a significant deterioration in the regularity and uniformity of the optical texture.

[0100] As can be seen from the comparison between Example 1 and Examples 6-7, if the volume ratio of quinoline in the composite organic solvent is too small, the strong dissolving ability cannot be fully utilized, resulting in some large molecular aromatic hydrocarbons in the raw material not being effectively extracted, QI removal being incomplete, and the content of the intermediate phase being low; if the volume ratio of quinoline in the composite organic solvent is too large, the selectivity of the solvent system becomes poor, too many high molecular weight components are retained in the soluble phase, which destroys the optimization of molecular weight distribution and the softening point is too high.

[0101] A comparison between Example 1 and Example 8 shows that if the temperature is raised first under constant pressure and then raised again during the thermal polycondensation reaction, the light components cannot be effectively eliminated in the initial stage. These small molecules will be violently vaporized in the subsequent high-temperature stage, interfering with the orderly arrangement of the intermediate phase, resulting in a large number of mosaic structures in the final product and a decrease in the content of the intermediate phase.

[0102] A comparison of Examples 1 and 9 shows that if the temperature in the low-pressure stage thermal condensation reaction is the same as that in the high-pressure stage thermal condensation reaction, then in the low-pressure stage, the excessively high temperature may cause some active components to prematurely and excessively condense, while in the high-pressure stage, the insufficient temperature cannot provide enough energy to drive the full fusion of the spheres, ultimately leading to a decrease in the content of the intermediate phase and the optical texture being mainly fine streamline.

[0103] As can be seen from the comparison between Example 1 and Comparative Example 1, if step (1) is not performed, the native QI in the raw material directly enters the subsequent reaction. As an impurity core, it seriously hinders the planar stacking of aromatic molecules, resulting in difficulty in nucleation and uneven growth of mesophase spheres. The final product has a low mesophase content, and the coking value and C / H ratio are not ideal.

[0104] As can be seen from the comparison between Example 1 and Comparative Example 2, if step (2) is not performed, the small amount of light components and high-boiling-point solvents remaining in the refined coal tar pitch will volatilize violently in the early stage of thermal polycondensation, which will destroy the stability of the reaction system and interfere with the formation of the intermediate phase. As a result, the content of the intermediate phase and the coking value of the final product are significantly lower, and the softening point also fails to meet the requirements due to insufficient molecular polycondensation.

[0105] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing coal-bearing mesophase pitch, characterized in that, The preparation method includes the following steps: Pre-treatment of coal-based raw material pitch yields refined coal pitch; The refined coal tar pitch is distilled to obtain distilled coal tar pitch; The distilled coal tar pitch is subjected to a thermal polycondensation reaction to obtain the coal-based mesophase pitch.

2. The preparation method according to claim 1, characterized in that, The pretreatment includes sequential crushing, dissolution, and solid-liquid separation; The solvent used in the dissolution process is a composite organic solvent; The composite organic solvent includes quinoline, and at least one of pyridine, toluene, benzene, wash oil, tetrahydrofuran, petroleum ether, gasoline, n-hexane, n-pentane, or n-heptane.

3. The preparation method according to claim 2, characterized in that, In the composite organic solvent, quinoline accounts for 30-70% by volume; And / or, the dissolution temperature is 40~160°C, and the time is 0.5~6h; And / or, the mass ratio of the coal-based raw material pitch to the composite organic solvent is 1:(1~3).

4. The preparation method according to claim 2, characterized in that, The solid-liquid separation temperature is 60~200°C, and the processing time is 12~24h; And / or, the solid-liquid separation method includes filtration or sedimentation.

5. The preparation method according to claim 1, characterized in that, The distillation methods include atmospheric distillation and / or vacuum distillation; And / or, the distillation temperature is 160~360°C and the time is 10~30 min; And / or, the quinoline insoluble content of the distilled coal tar pitch is ≤0.03wt%.

6. The preparation method according to claim 1, characterized in that, An inert gas is introduced during the thermal polycondensation reaction. And / or, the temperature of the thermal polycondensation reaction is 380~450°C; And / or, the duration of the thermal polycondensation reaction is 4 to 24 hours; And / or, the pressure of the thermal polycondensation reaction is 0~5MPa.

7. The preparation method according to claim 1, characterized in that, The thermal polycondensation reaction includes a low-pressure stage and a high-pressure stage that proceed sequentially. During the low-pressure stage, the pressure is -0.05 to -0.1 MPa, the constant temperature is 300 to 380°C, and the constant temperature time is 2 to 4 hours. During the high-pressure stage, the pressure is 1.5~3.5MPa, the constant temperature is 400~450°C, and the constant temperature time is 4~8h.

8. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Preparation of refined coal tar pitch, the specific steps include: (a) The coal-based raw material pitch is crushed and sieved to obtain crushed raw material with a particle size D50 of 20~50μm; (b) The pulverized raw material and the composite organic solvent are mixed and dissolved at 40-160°C and 100-600 rpm for 0.5-6 hours to obtain a coal tar pitch mixture; the composite organic solvent includes quinoline, and at least one of pyridine, toluene, benzene, wash oil, tetrahydrofuran, petroleum ether, gasoline, n-hexane, n-pentane or n-heptane; the volume percentage of quinoline in the composite organic solvent is 30-70%; the mass ratio of the coal-based raw material pitch to the composite organic solvent is 1:(1-3); (c) The coal tar pitch mixture is filtered or settled at a temperature of 60~200°C for 12~24 hours to obtain the refined coal tar pitch; (2) The refined coal tar pitch is heated to 160-360°C at a heating rate of 2-5°C / min for 10-30 min to obtain distilled coal tar pitch with a quinoline insoluble content ≤0.03wt%. (3) The distilled coal tar pitch is placed in a reaction vessel and an inert gas is introduced as a protective gas at a flow rate of 1~10L / min. The low-pressure stage thermal polycondensation reaction is carried out for 2~4h under the conditions of pressure -0.05~-0.1MPa and temperature 300-380°C. Then the pressure is increased to 1.5~3.5MPa and the temperature is increased to 400~450°C at a heating rate of 1~10°C / min for 4~8h of high-pressure stage thermal polycondensation reaction. After the reaction is completed, the temperature is programmed to drop to 200~300°C and then naturally cooled to 20~50°C to obtain coal-based mesophase pitch.

9. A coal-bearing mesophase pitch, characterized in that, The coal-series mesophase pitch is prepared using the preparation method described in any one of claims 1-8; The coal-bearing mesophase pitch is in a liquid crystal state; the optical state of the coal-bearing mesophase pitch exhibits anisotropy.

10. The coal-bearing mesophase pitch according to claim 9, characterized in that, The coking value of the coal-series mesophase pitch is 60-85%; And / or, the C / H ratio of the coal-series mesophase pitch is 1.3 to 1.6; And / or, the mesophase content of the coal-series mesophase pitch is 50-98%; And / or, the softening point of the coal-series mesophase pitch is 260~320°C.

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