Method for preparing spinnable mesophase pitch and carbon fiber from coal tar fraction

Abstract

The present invention relates to a method for preparing spinnable mesophase pitch and carbon fiber from coal tar fractions, belonging to the technical field of carbon materials. In the method of the present invention, aromatic fractions with different distillation ranges in coal tar are first distilled and extracted, and one or more aromatic fractions with a certain distillation range are used as raw materials for activation treatment. Then, one or more activated coal tar fractions and one or more unactivated coal tar fractions are subjected to a non-catalytic polymerization reaction at a lower temperature to obtain a synthetic asphalt precursor, and then a high-temperature polymerization reaction is carried out to obtain a matrix asphalt. After vacuum distillation treatment, solvent extraction or inert gas purge, spinnable mesophase pitch is obtained. The spinnable mesophase pitch has a wide-range streamline optical texture distribution, good orientation and order, the mesophase content can reach 100%, the softening point is low, the coking value is high, the ash content is low, and the structure is controllable. The carbon fiber prepared based on this mesophase pitch requires a short oxidation time and has excellent properties.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon materials, and in particular relates to a method for preparing spinnable mesophase pitch and carbon fiber from coal tar fractions. Background Art

[0002] Mesophase pitch is a nematic liquid crystal material with a disc-like or rod-like molecular structure prepared by thermal polycondensation of polycyclic aromatic hydrocarbons. It exhibits the unique anisotropy of crystals and maintains the fluidity of the liquid phase. Mesophase pitch has the advantages of easy graphitization, high carbon residue rate, low price and strong processability. It can be used to prepare many high-performance carbon materials (such as high-performance carbon fibers, needle coke, carbon microspheres, etc.) at low cost, and plays a huge role in the fields of national defense industry, aerospace cutting-edge technology, electrical and electronic engineering, daily life, etc. As an important precursor of high-quality carbon materials, the orientation and structure of mesophase pitch have an important influence on the performance of carbon materials. With the rapid development of the carbon material production industry, the demand and quality requirements for mesophase pitch as a precursor of carbon materials are also increasing. However, the localization preparation of high-performance functional materials based on mesophase pitch in my country has not reached the level of performance of medium-sized products abroad. It is imperative to study and develop a low-cost, high-performance and simple process preparation method for mesophase pitch.

[0003] Coal tar contains fractions such as light oil, phenol oil, naphthalene oil, washing oil, anthracene oil, and asphalt residues. However, the coal tar produced directly is difficult to directly meet the production needs of carbon materials. It often needs to be modified to reduce the content of low molecular weight substances, increase the residual carbon rate, and adjust the molecular weight distribution and rheological properties to meet the use needs of carbon products. Mesophase asphalt has been industrialized abroad, but restrictions on exports to my country have severely restricted the development of related downstream industries in my country. Industrial asphalt is a complex molecular mixture with different structures and reactivity. It is difficult to control the uniform source of raw materials. The influence of molecular structure characteristics on liquid phase carbonization behavior is not obvious. Its reaction process and mechanism are difficult to control and control. Therefore, it is difficult to prepare mesophase asphalt with stable quality. There is no breakthrough in the technology of stable and continuous production of high-quality mesophase asphalt in China. In addition, industrial asphalt needs to undergo purification treatment containing multiple cumbersome steps as raw material, which increases the preparation cost and complexity of mesophase asphalt. In order to facilitate large-scale preparation and application, pure aromatic compounds such as naphthalene have become one of the raw materials for preparing synthetic asphalt. However, due to the very stable properties of such aromatic compounds, the existing preparation methods usually require the addition of catalysts. The polymerization of aromatics is a non-dehydrogenation reaction process, and its products usually have cycloalkane rings or alkyl side chains, and have low softening points, high solubility and excellent anisotropy. The commonly used Lewis acid catalysts are difficult to remove during the reaction, and metal ions are introduced. For example, aluminum trichloride may generate hydrogen chloride and aluminum oxide during the reaction, which will have a significant negative impact on product quality and equipment safety. In addition, superacid catalysts (hydrofluoric acid, etc.) will also cause serious safety problems for equipment and personnel. In order to solve the above problems, aromatics with active sites and controllable components are used as raw materials. If they are allowed to undergo polycondensation reactions using their own active sites during heat treatment, the preparation process of mesophase asphalt can be designed and regulated at the molecular level. It is possible to simply and efficiently prepare mesophase asphalt with uniform and stable quality through non-catalytic routes, and it can meet the requirements of large-scale industrial production.

[0004] Compared with coal tar pitch and petroleum asphalt with extremely complex components as raw materials for preparing mesophase asphalt, aromatic compounds have the advantages of high purity, stable properties, good aromaticity, extremely low ash content, no other heteroatoms, controllable molecular structure, simple heat treatment process, etc., mainly naphthalene, methylnaphthalene, anthracene, etc. CN114381292A uses polycyclic aromatic hydrocarbons such as tetrahydroquinoline, tetrahydronaphthalene, decahydronaphthalene as raw materials to prepare mesophase asphalt with wide-area streamlined optical structure. CN113637147A chloromethylates aromatic compounds such as naphthalene and anthracene, and then uses the chloromethylated products to perform polymerization to obtain isotropic asphalt. The reaction conditions are mild, the corrosiveness of the materials is greatly reduced, and the operation is simple. CN113621130A uses brominated methylnaphthalene to perform debromination polymerization to prepare isotropic asphalt. CN115197732A obtains isotropic asphalt by polymerization of halogenated aromatic compounds and other aromatic components.

[0005] On the basis of the existing technology, by adjusting the raw material composition and process conditions, it is expected that the synthesized isotropic pitch will be transformed to the direction of generating the mesophase, thereby greatly improving the quality of the synthetic asphalt and the performance of the prepared carbon fiber. In addition, the cost and requirements of using pure aromatics as raw materials in the existing technology are relatively higher, and there are few cases of using coal tar fractions as raw materials to synthesize spinnable asphalt. Directly using coal tar fractions as raw materials to prepare spinnable asphalt can allow low molecular weight substances to participate in the reaction and enter the product system, thereby fully and controllably utilizing various aromatics in coal tar, so that low-value coal tar can be used in a high-value and efficient manner. In addition, the molecular weight distribution of aromatics in coal tar fractions is more continuous and easy to control, which is more suitable for preparing spinnable asphalt with suitable viscosity and fluidity, and has significant advantages over pure aromatic raw materials. Therefore, making full use of coal tar rich aromatic fractions for non-catalytic thermal polycondensation to synthesize high-quality mesophase asphalt and use it to prepare carbon fibers has great application prospects. Summary of the invention

[0006] In view of the above technical problems, the present invention uses coal tar fractions, which are inexpensive and readily available, as the basic raw materials, and provides a method for preparing spinnable mesophase pitch and carbon fiber from coal tar fractions. The molecular structure and molecular weight of the aromatic fractions in the coal tar fractions have significant diversity characteristics, and have different active sites after activation treatment; the aromatic fractions with different active sites are mixed to undergo thermal polycondensation reaction, and the highly active structure is used to initiate selective polymerization to synthesize spinnable mesophase pitch with suitable molecular arrangement, thereby eliminating the purification treatment steps required for industrial asphalt raw materials, and the design and control of the reaction process can be achieved at the molecular level. At the same time, various other required unactivated coal tar fractions are added together with the activated coal tar fractions as precursors for preparing high-performance mesophase pitch-based carbon fibers, and the molecular structure of the product is further regulated and optimized. The raw materials of this method are cheap, stable and easily available, the components and molecular weight are easy to regulate, no impurity removal treatment is required, the preparation process is simple, the equipment requirements are low, the product purity is high, and stable industrial production is easy to achieve.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows.

[0008] In a first aspect, the present invention provides a method for preparing a spinnable mesophase pitch from a coal tar fraction, comprising the following steps:

[0009] S1, extracting aromatic fractions of different distillation ranges from coal tar by distillation, and selecting one or more aromatic fractions of distillation ranges as raw materials;

[0010] S2, performing activation treatment on the selected one or more distillation range aromatic fractions to obtain one or more activated coal tar fractions;

[0011] S3, one or more activated coal tar fractions in step S2 are mixed with one or more unactivated coal tar fractions in proportion as synthetic asphalt raw materials, and polymerization reaction is carried out at 120-350° C. under inert atmosphere protection, and cooling is performed to obtain a synthetic asphalt precursor with a softening point of 40-130° C.;

[0012] In the synthetic asphalt raw material, the total proportion of activated coal tar fraction is 10wt%~100wt%;

[0013] S4, under the protection of an inert atmosphere, further polymerizing the synthetic asphalt precursor at 200-440° C. to obtain a matrix asphalt;

[0014] S5. The matrix pitch is subjected to reduced pressure distillation, solvent extraction or inert gas purging to obtain a spinnable mesophase pitch.

[0015] Preferably, in step S1, the coal tar is coal tar produced by coking coking coal at 950-1050°C (high temperature), coal tar produced by pyrolysis of low-rank coal at 500-700°C (medium temperature), or coal tar produced by pyrolysis of low-rank coal at 300-450°C (low temperature).

[0016] Preferably, in step S1, the distillation is atmospheric distillation or reduced pressure distillation at 80-400°C.

[0017] Preferably, in step S1, the aromatic fraction includes but is not limited to a mixture of one or more of a benzene-rich aromatic fraction, a naphthalene-rich aromatic fraction, a phenol-rich aromatic fraction, an anthracene-rich aromatic fraction, a phenanthrene-rich aromatic fraction, a quinone-rich aromatic fraction and a quinoline-rich aromatic fraction.

[0018] Preferably, in step S2, the activation treatment method is:

[0019] One or more selected coal tar aromatic fractions and solvent carbon tetrahalide are added to a reaction device in a mass ratio of (2-5): (10-30), heated to 40-150°C, introduced with halogen gas, reacted for 3-20 hours, condensed and refluxed during the reaction process, and after the reaction is completed, the solvent carbon tetrahalide is recovered by distillation for recycling to obtain an activated coal tar fraction; the solvent carbon tetrahalide is carbon tetrachloride or carbon tetrabromide, and the halogen gas is chlorine or bromine;

[0020] Alternatively, one or more aromatic hydrocarbon fractions of the distillation range are mixed with a highly active halide in a mass ratio of 1:(0.1-10), and reacted at 120-250° C. for 1-20 hours; the highly active halide includes but is not limited to a mixture of one or more of halobenzenes, halogenated methylbenzenes, dihalogenated benzenes, halogenated naphthalenes, halogenated methylnaphthalenes, halogenated alkanes, and halogenated olefins.

[0021] Preferably, in step S2, the activated coal tar fraction includes but is not limited to a mixture of one or more of halogenated benzene-rich aromatics, halogenated naphthalene-rich aromatics, halogenated phenol-rich aromatics, halogenated anthracene-rich aromatics, halogenated phenanthrene-rich aromatics, halogenated quinone-rich aromatics and halogenated quinoline-rich aromatics.

[0022] Preferably, in step S2, the activated coal tar fraction is a monohalogenated or polyhalogenated product at any halogenated site.

[0023] Preferably, in step S2, the unactivated coal tar fraction includes but is not limited to one or more of a benzene-rich aromatic fraction, a naphthalene-rich aromatic fraction, a phenol-rich aromatic fraction, an anthracene-rich aromatic fraction, a phenanthrene-rich aromatic fraction, a quinone-rich aromatic fraction and a quinoline-rich aromatic fraction;

[0024] More preferably, in step S2, the method for obtaining the unactivated coal tar fraction is the same as the method for obtaining the aromatic fraction in step S1.

[0025] Preferably, the aromatic fraction obtained by atmospheric distillation of the coal tar at 80°C to 150°C is activated to obtain activated fraction 1, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 150°C and less than or equal to 200°C is activated to obtain activated fraction 2, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 200°C and less than or equal to 250°C is activated to obtain activated fraction 3, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 250°C and less than or equal to 300°C is activated to obtain activated fraction 4, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 300°C and less than or equal to 350°C is activated to obtain activated fraction 5, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 350°C and less than or equal to 400°C is activated to obtain activated fraction 6, and the pressure of the vacuum distillation is below 13 kPa;

[0026] In the synthetic asphalt raw material, the ratio of activated fraction 1 used in the preparation is 0~30wt%, the ratio of activated fraction 2 used in the preparation is 0~60wt%, the ratio of activated fraction 3 used in the preparation is 0~60wt%, the ratio of activated fraction 4 used in the preparation is 0~60wt%, the ratio of activated fraction 5 used in the preparation is 0~60wt%, and the ratio of activated fraction 6 used in the preparation is 0~60wt%.

[0027] Preferably, in step S3, the conditions for the polymerization reaction at 120-350°C under the protection of an inert atmosphere are as follows: the inert atmosphere is one or more of nitrogen, helium and argon, and the inert atmosphere flow rate is 0.5-10 L / min; the reaction is carried out under stirring, and the stirring rate is 80-1000 rpm / min; the temperature is first raised to 120-270°C and kept at a constant temperature for 0.5-10h, and then the temperature is further raised to 280-350°C and kept at a constant temperature for 0.5-10h, and the heating rates are 1-10°C / min respectively; condensation and reflux are performed during the reaction;

[0028] More preferably, reflux is performed through a spherical condenser tube with a length of 0.2-2.5 m;

[0029] More preferably, the reaction container is a quartz glass reactor or a Hastelloy alloy reactor;

[0030] Particularly preferably, the reaction container is a quartz glass reactor.

[0031] Preferably, in step S3, the cooling temperature is below 160°C.

[0032] Preferably, in step S4, the conditions for further polymerization of the synthetic asphalt precursor at 200-440° C. under the protection of an inert atmosphere are:

[0033] The inert atmosphere is one or more of nitrogen, helium and argon, and the inert atmosphere flow rate is 0.5~10L / min; the reaction is carried out under stirring, and the stirring rate is 60~1200rpm / min; the temperature is first raised to 200~350℃ and kept at a constant temperature for 0.5~20h, and then raised to 360~440℃ and kept at a constant temperature for 0.5~20h, and the heating rates are 2~10℃ / min respectively;

[0034] More preferably, the temperature is first increased to 200-350° C. at a heating rate of 5° C. / min and maintained at a constant temperature for 0.5-20 h, and then increased to 360-440° C. at a heating rate of 2° C. / min and maintained at a constant temperature for 0.5-20 h.

[0035] Preferably, in step S5, the temperature of the reduced pressure distillation treatment is 340-400° C., the vacuum degree is -80--110 kPa, and the time is 0.5-2 h;

[0036] The solvent used for the solvent extraction is one or more of quinoline, pyridine, washing oil, kerosene, nitrogen methyl pyrrolidone, and toluene. The temperature of the solvent extraction is room temperature or lower than the boiling point of the solvent, the pressure is normal pressure, and the time is 1 to 5 hours;

[0037] The inert gas purging adopts an inert atmosphere of nitrogen, argon or helium, the purging time is 1 to 5 hours, and the purging gas rate is 1 to 20 L / min.

[0038] More preferably, the vacuum degree of the reduced pressure distillation treatment is -90 kPa and the time is 1 hour.

[0039] In a second aspect, the present invention also provides a method for preparing carbon fiber using the spinnable mesophase pitch prepared by the above method, comprising the following steps: melt spinning the spinnable mesophase pitch to obtain fiber precursors, oxidizing the fiber precursors, and carbonizing and graphitizing the fiber precursors under an inert atmosphere to obtain mesophase pitch-based carbon fibers.

[0040] Preferably, the melt spinning temperature is 340-390°C.

[0041] Preferably, the oxidation temperature is 280-360°C.

[0042] Preferably, the inert atmosphere is one or more of nitrogen, helium and argon, and the gas flow rate is 1-10 L / min.

[0043] Preferably, the carbonization temperature is 700-1400° C., and the time is 0.1-3 h.

[0044] Preferably, the graphitization temperature is 2800-3000° C., and the time is 0.5-3 h.

[0045] Preferably, the heating rates of the carbonization and graphitization are 0.5-5°C / min respectively.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The present invention uses coal tar as raw material, obtains activated coal tar fraction after distillation, activation and mixing, and simultaneously adds a certain proportion of unactivated coal tar fraction that can polymerize with it to synthesize high-quality spinnable mesophase pitch through non-catalysis and prepare carbon fiber. The preparation method has the advantages of stable raw material source, low cost, no other impurities, controllable molecular structure, mild reaction conditions, low equipment requirements, and easy industrial stable production.

[0048] 2. The raw material selection of the present invention is diversified and flexible. Aromatic fractions of different distillation ranges are extracted from coal tar by distillation. A single distillation range aromatic fraction can be selected, or aromatic fractions of multiple distillation ranges can be combined as the starting raw material, making full use of the characteristics of each distillation segment of coal tar, broadening the range of raw material selection, and meeting different synthesis needs.

[0049] 3. The present invention can accurately control the elemental composition, molecular weight distribution and molecular structure of the spinnable mesophase asphalt; the spinnable mesophase asphalt synthesized by this method has the characteristics of continuous and controllable molecular weight distribution, controllable elements, good viscosity and fluidity, and extremely low ash content.

[0050] 4. The present invention adopts a thermal gradient controlled polymerization process. In the initial stage of polymerization of the activated fraction, a relatively low temperature is used and the heating rate is controlled to promote the initial orderly arrangement of the molecules; as the polymerization reaction proceeds, the temperature is gradually increased to promote further crosslinking and rearrangement of the molecules. Through this fine thermal gradient control, the asphalt molecules are guided to accurately arrange to form a high-quality mesophase structure, effectively reducing the generation of disordered phases in traditional constant temperature polymerization processes, thereby increasing the mesophase content to 100%.

[0051] 5. The present invention solves the problem of pretreatment of mixed raw materials such as coal tar and petroleum asphalt; at the same time, the present invention uses coal tar fraction as raw material, and after ratio adjustment, solves the problem of stability of raw material source, and the preparation process is simpler and more feasible, so that coal tar can be used more efficiently and with higher value.

[0052] 6. The raw materials of the spinnable mesophase asphalt prepared by the present invention are cheap and easily available, and the conditions are mild. The spinnable mesophase asphalt prepared thereby has a wide-area streamlined optical texture distribution, a low softening point (220-280°C), good fluidity, a mesophase content of up to 100%, a coking value of more than 80%; and the ash content is less than 0.005%.

[0053] 7. The present invention uses solvent extraction, vacuum distillation or inert gas purging to treat the base asphalt, effectively remove low-boiling impurities and unreacted residues, adjust the composition, and finally obtain spinnable mesophase asphalt, realizing the conversion from coal tar fraction to high-quality spinnable mesophase asphalt.

[0054] 8. The carbon fiber prepared by melt spinning, oxidation, carbonization or graphitization of the spinnable mesophase pitch prepared by the present invention has very excellent tensile strength and elastic modulus. According to test results, the tensile strength of the obtained fiber after carbonization can reach 1500MPa, and the elastic modulus can reach 230GPa; the tensile strength of the obtained fiber after graphitization can reach 3600MPa, and the elastic modulus can reach 900GPa.

[0055] 9. The mesophase pitch prepared by the present invention can also be used as a high-quality raw material for materials such as needle coke, foamed carbon, and mesophase carbon microspheres, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 The present invention is a process flow chart of a method for preparing spinnable mesophase pitch and carbon fiber from coal tar fractions in a specific embodiment of the present invention.

[0058] Figure 2 This is a GC-MS spectrum of a coal tar fraction product with halogen active sites prepared by direct halogenation of an aromatic fraction extracted by distillation of coal tar at 225-270° C. in Example 1 of the present invention.

[0059] Figure 3 This is a polarized microstructure photograph of the spinnable mesophase pitch obtained in Example 1 of the present invention.

[0060] Figure 4 This is a SEM image of the carbon fiber obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0061] To facilitate understanding of the present invention, various exemplary embodiments of the present invention are now described in detail. This detailed description should not be regarded as a specific limitation of the present invention, but should be understood as a more detailed description of certain aspects, features and embodiments of the present invention.

[0062] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0063] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0064] The method for preparing spinnable mesophase pitch from coal tar fractions of the present invention comprises the following steps:

[0065] S1. extracting aromatic fractions of different distillation ranges from coal tar by distillation, and using one or more aromatic fractions of distillation ranges as raw materials;

[0066] S2, performing activation treatment on the selected one or more distillation range aromatic fractions to obtain one or more activated coal tar fractions;

[0067] S3. Under the protection of an inert atmosphere, one or more activated coal tar fractions and one or more unactivated coal tar fractions are mixed in an appropriate proportion as a synthetic asphalt raw material, added to a reaction vessel, reacted under stirring, first heated to 120-270°C and kept at a constant temperature for 0.5-10h, and then continued to heat to 280-350°C and kept at a constant temperature for 0.5-10h to obtain a synthetic asphalt precursor; during the reaction, the conversion rate of the light component raw material is increased by condensation reflux;

[0068] S4. Under inert atmosphere protection and stirring, the synthetic asphalt precursor is first heated to 200-350°C and kept at a constant temperature for 0.5-20h, and then heated to 360-440°C and kept at a constant temperature for 0.5-20h, with a heating rate of 2-10°C / min, to obtain a matrix asphalt;

[0069] S5. The matrix pitch is subjected to solvent extraction, vacuum distillation or inert gas purging to obtain a spinnable mesophase pitch.

[0070] In the above technical solution, in step S1, coal tar includes coal tar produced by high temperature (950-1050°C) coking of coking coal, coal tar produced by medium temperature (500-700°C) pyrolysis of low-rank coal, or coal tar produced by low temperature (300-450°C) pyrolysis of low-rank coal, but is not limited to these.

[0071] In the above technical scheme, in step S1, the aromatic fraction includes but is not limited to one or more mixtures of a benzene-rich aromatic fraction, a naphthalene-rich aromatic fraction, a phenol-rich aromatic fraction, anthracene-rich aromatic fraction, a phenanthrene-rich aromatic fraction, a quinone-rich aromatic fraction and a quinoline-rich aromatic fraction.

[0072] In the above technical solution, in step S1, the distillation is atmospheric distillation or reduced pressure distillation at 80-400° C., and different distillation temperatures are required to obtain different aromatic fractions.

[0073] In the above technical scheme, in step S2, the activation treatment adopts direct halogenation or addition of highly active halides; the activated coal tar fraction includes one or more mixtures of halogenated benzene-rich aromatics, halogenated naphthalene-rich aromatics, halogenated phenol-rich aromatics, halogenated anthracene-rich aromatics, halogenated phenanthrene-rich aromatics and halogenated quinone-rich aromatics. The activated coal tar fraction can be a monohalogenated compound or a polyhalogenated compound. Preferably, the direct halogenation method is: adding the selected coal tar aromatic fraction and carbon tetrachloride or carbon tetrabromide to a reaction device in a mass ratio of (2-5): (10-30), heating to 40-150°C, introducing chlorine or bromine gas, reacting for 3-20 hours, condensing and refluxing the reaction process, and after the reaction is completed, distilling and recovering carbon tetrachloride or carbon tetrabromide to obtain a coal tar fraction with chlorine or bromine halogen active sites, that is, an activated coal tar fraction. Preferably, the highly active halide is a halide with a certain reactivity, including but not limited to one or more of halogenated benzenes, dihalogenated benzenes, halogenated naphthalenes, halogenated alkanes, and halogenated olefins. The reaction temperature is 120-250° C., and the reaction time is 1-20 hours.

[0074] In the above technical scheme, in step S2, the unactivated coal tar fraction includes but is not limited to one or more of a benzene-rich aromatic fraction, a naphthalene-rich aromatic fraction, a phenol-rich aromatic fraction, anthracene-rich aromatic fraction, a phenanthrene-rich aromatic fraction, a quinone-rich aromatic fraction and a quinoline-rich aromatic fraction; preferably, the method for obtaining the unactivated coal tar fraction is the same as the method for obtaining the aromatic fraction in step S1.

[0075] In the above technical solution, in step S3, the inert atmosphere is preferably one or more of nitrogen, helium and argon; the inert atmosphere flow rate is 0.5-10L / min; the reaction stirring rate is 80-1000rpm / min; the preferred heating rate is 1-10℃ / min; reflux is performed through a spherical condenser with a length of 0.2-2.5m; the reaction container is a quartz glass reactor or a Hastelloy reactor; the preferred reaction container is a quartz glass reactor. In the preferred raw material for synthetic asphalt, the mass proportion of coal tar fraction with halogen active sites is 10%-100%. It is preferably cooled to below 160℃.

[0076] In the above technical solution, in step S4, it is preferred to first increase the temperature to 200-350°C at a heating rate of 5°C / min and keep the temperature constant for 0.5-20h, and then increase the temperature to 360-440°C at a heating rate of 2°C / min and keep the temperature constant for 0.5-20h. The reaction pressure is: normal pressure, the pressure generated by the autogenous pressure of the reaction process, or the pressure generated by the inert atmosphere.

[0077] In the above technical scheme, in step S5, the temperature of the reduced pressure distillation treatment is 340~400℃, the vacuum degree is -80~-110kPa, and the time is 0.5h~2h; preferably, the vacuum degree is -90kPa, and the time is 1h. The solvent used in the solvent extraction process is a mixture of one or more solvents such as quinoline, pyridine, washing oil, kerosene, nitrogen methyl pyrrolidone, toluene, etc.; preferably, the temperature of the solvent extraction is room temperature or lower than the boiling point of the solvent, the pressure is normal pressure, and the time is 1~5h; preferably, the inert gas purging conditions are large flow nitrogen, argon or helium, the purging time is 1~5h, and the purging gas rate is 1~20L / min.

[0078] The spinnable mesophase pitch prepared by the invention has a softening point of 220-280° C., a mesophase content of 100%, a coking value of more than 80%, and an ash content of less than 0.005%.

[0079] The method for preparing carbon fiber by using the spinnable mesophase pitch of the present invention comprises the following steps: the spinnable mesophase pitch is melt-spun to obtain fiber precursors, the fiber precursors are oxidized, and then carbonized and graphitized under an inert atmosphere to obtain mesophase pitch-based carbon fibers.

[0080] In the above technical scheme, the inert atmosphere is preferably one or more of nitrogen, helium and argon, and the gas flow rate is 1~10L / min; the melt spinning temperature is 340~390°C; the oxidation temperature is 280~360°C; the carbonization temperature is 700~1400°C, and the time is 0.1~3h; the graphitization temperature is 2800~3000°C, and the time is 0.5~3h; the heating rate is 0.5~5°C / min.

[0081] Figure 1A specific embodiment of the method for preparing spinnable mesophase pitch and carbon fiber from coal tar fractions of the present invention comprises the following steps: first, distilling and extracting aromatic fractions of different distillation ranges from coal tar as raw materials, and performing activation treatments on them respectively, namely, the aromatic fraction of 80°C to 150°C obtained by atmospheric distillation of coal tar at 80°C to 150°C is activated to obtain activated fraction 1, the aromatic fraction of 150°C to 200°C obtained by atmospheric distillation of coal tar at a temperature greater than 150°C and less than or equal to 200°C is activated to obtain activated fraction 2, and the aromatic fraction of 200°C obtained by atmospheric distillation of coal tar at a temperature greater than 200°C and less than or equal to 250°C is activated to obtain activated fraction 2. The 0°C~350°C aromatic fraction is activated to obtain an activated fraction 3, the 250~300°C aromatic fraction obtained by atmospheric distillation of coal tar at a temperature greater than 250°C and less than or equal to 300°C is activated to obtain an activated fraction 4, the 300°C~350°C aromatic fraction obtained by atmospheric distillation of coal tar at a temperature greater than 300°C and less than or equal to 350°C is activated to obtain an activated fraction 5, and the 350°C~400°C aromatic fraction obtained by vacuum distillation of coal tar at a temperature greater than 350°C and less than or equal to 400°C is activated to obtain an activated fraction 6, and the pressure of the vacuum distillation is less than 13 kPa;

[0082] Then, after being prepared in appropriate proportions, they are used as synthetic asphalt raw materials. In the synthetic asphalt raw materials, the proportion of activated fraction 1 used in the preparation is 0-30wt%, the proportion of activated fraction 2 used in the preparation is 0-60wt%, the proportion of activated fraction 3 used in the preparation is 0-60wt%, the proportion of activated fraction 4 used in the preparation is 0-60wt%, the proportion of activated fraction 5 used in the preparation is 0-60wt%, and the proportion of activated fraction 6 used in the preparation is 0-60wt%; the total proportion of activated coal tar fraction is 10wt%-100wt%;

[0083] The synthetic asphalt raw material is then initially polymerized to obtain a synthetic asphalt precursor, and further polymerized to obtain a base asphalt;

[0084] The matrix pitch is then subjected to vacuum distillation, solvent extraction or inert gas purging to obtain a spinnable mesophase pitch;

[0085] Finally, the spinnable mesophase pitch is melt-spinned to obtain fiber precursors, and the fiber precursors are oxidized, carbonized and graphitized under an inert atmosphere to obtain mesophase pitch-based carbon fibers.

[0086] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

[0087] Example 1

[0088] S1. Distill 18700 kg of coal tar at 225-270° C. to obtain 1100 kg of aromatic fraction as a raw material;

[0089] S2, adding 1000kg of aromatic hydrocarbon fraction and 4000kg of carbon tetrachloride into a reactor, heating to 75°C, condensing and reflux during the reaction process, introducing chlorine gas and reacting for 3.5h, distilling and recovering carbon tetrachloride to obtain 960kg of activated coal tar fraction;

[0090] S3, 610 kg of activated coal tar fraction, 60 kg of coal tar fraction extracted by distillation at 70-110 ° C, and 4 kg of coal tar fraction extracted by distillation at 200-250 ° C were placed in a polymerization reaction vessel, a spherical condenser was vertically installed on the upper part of the reaction vessel, and then N2 with a flow rate of 5 L / min was introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 220°C at a heating rate of 4°C / min and kept at this temperature for 2 hours, and then raised to 330°C and kept at this temperature for 5 hours, to obtain a synthetic asphalt precursor with a softening point of 89°C;

[0091] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into the polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 The reaction was purged for 25 minutes, the reaction pressure was in the autogenous pressure state, and the mixture was stirred at a stirring rate of 100 rpm / min. The temperature was first raised to 320°C at a heating rate of 10°C / min and kept constant for 2 hours, and then raised to 380°C at a heating rate of 3°C / min and kept constant for 9 hours to obtain the matrix asphalt.

[0092] S5. The temperature of the matrix asphalt is lowered to 360°C, and then vacuumed to -90 kPa, and subjected to reduced pressure distillation for 1 hour to obtain a spinnable mesophase asphalt having a softening point of 259°C, a mesophase content of 100%, a coking value of 83%, and an ash content of less than 0.003%;

[0093] S6. Place the spinnable mesophase asphalt into a melt spinning machine, gradually increase the temperature to 375°C to continuously spin fiber filaments with a diameter of 9 microns; after oxidation at 280°C, increase the temperature to 1000°C at a heating rate of 4°C / min under the protection of nitrogen and keep the temperature constant for 0.5h, and obtain a carbon fiber with a tensile strength of 1500MPa and an elastic modulus of 230GPa; increase the temperature to 2900°C at a heating rate of 5°C / min under the protection of argon and keep the temperature constant for 1h, and obtain a graphitized carbon fiber with a tensile strength of 3600MPa and an elastic modulus of 900GPa.

[0094] Example 2

[0095] S1. 18700 kg of coal tar is distilled and extracted at 300-400° C. to obtain 350 kg of aromatic fraction as a raw material;

[0096] S2, adding 200kg of aromatic hydrocarbon fraction and 800kg of carbon tetrachloride into a reactor, heating to 75°C, condensing and reflux during the reaction process, introducing chlorine gas and reacting for 3.5h, distilling and recovering carbon tetrachloride to obtain 195kg of activated coal tar fraction;

[0097] S3, 106 kg of activated coal tar fraction and 25 kg of coal tar fraction extracted by distillation at 210-270 ° C were placed in a polymerization reaction vessel, a spherical condenser was vertically installed on the upper part of the reaction vessel, and then N with a flow rate of 5 L / min was introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 160°C at a heating rate of 4°C / min and kept at this temperature for 2 hours, and then raised to 310°C and kept at this temperature for 8 hours, to obtain a synthetic asphalt precursor with a softening point of 65°C;

[0098] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into the polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 The reaction was purged for 25 minutes, the reaction pressure was in the autogenous pressure state, and the mixture was stirred at a stirring rate of 100 rpm / min. The temperature was first raised to 320°C at a heating rate of 10°C / min and kept constant for 0.5h, and then raised to 400°C at a heating rate of 3°C / min and kept constant for 6h to obtain the matrix asphalt.

[0099] S5. The temperature of the matrix asphalt is lowered to 360°C, and then vacuumed to -90 kPa, and subjected to reduced pressure distillation for 1 hour to obtain a spinnable mesophase asphalt having a softening point of 253°C, a mesophase content of 100%, a coking value of 88%, and an ash content of less than 0.005%;

[0100] S6. Place the spinnable mesophase asphalt into a melt spinning machine, gradually increase the temperature to 360°C to continuously spin fiber filaments with a diameter of 9 microns; after oxidation at 280°C, increase the temperature to 1000°C at a heating rate of 4°C / min under the protection of nitrogen and keep the temperature constant for 0.5h, and obtain a carbon fiber with a tensile strength of 1293MPa and an elastic modulus of 200GPa; increase the temperature to 2900°C at a heating rate of 5°C / min under the protection of argon and keep the temperature constant for 1h, and obtain a graphitized fiber with a tensile strength of 3310MPa and an elastic modulus of 760GPa.

[0101] Example 3

[0102] S1. 18700 kg of coal tar is distilled and extracted at 200-250° C. to obtain 1500 kg of aromatic fraction, and 300-350° C. is distilled and extracted to obtain 350 kg of aromatic fraction, and the two are mixed in a mass ratio of 3:2 to obtain raw aromatics;

[0103] S2, adding 870kg of aromatic hydrocarbon fraction and 3600kg of carbon tetrabromide into a reactor, heating to 75°C, condensing and reflux during the reaction process, introducing bromine gas, reacting for 5.5h, and distilling and recovering carbon tetrabromide to obtain 770kg of activated coal tar fraction;

[0104] S3, 513 kg of activated coal tar fraction, 66 kg of coal tar fraction extracted by distillation at 70-110 ° C, and 11 kg of coal tar fraction extracted by distillation at 210-270 ° C are placed in a polymerization reaction vessel; a spherical condenser is vertically installed on the upper part of the reaction vessel, and then N with a flow rate of 5 L / min is introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 200°C at a heating rate of 4°C / min and kept constant for 1.5 h, and then raised to 320°C and kept constant for 4 h, to obtain a synthetic asphalt precursor with a softening point of 80°C;

[0105] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into the polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 The reaction was purged for 25 minutes, the reaction pressure was in the autogenous pressure state, and the mixture was stirred at a stirring rate of 200 rpm / min. The temperature was first raised to 310°C at a heating rate of 10°C / min and kept constant for 1 hour, and then raised to 390°C at a heating rate of 3°C / min and kept constant for 5 hours to obtain the matrix asphalt.

[0106] S5. The temperature of the matrix asphalt is lowered to 370°C, and then vacuumed to -90 kPa, and subjected to reduced pressure distillation for 1 hour to obtain a spinnable mesophase asphalt having a softening point of 271°C, a mesophase content of 100%, a coking value of 82%, and an ash content of less than 0.002%;

[0107] S6. Place the spinnable mesophase asphalt into a melt spinning machine, gradually increase the temperature to 385°C to continuously spin fiber filaments with a diameter of 10 microns; after oxidation at 300°C, increase the temperature to 1000°C at a rate of 4°C / min under the protection of nitrogen and keep the temperature constant for 0.5h, and obtain a carbon fiber with a tensile strength of 1400MPa and an elastic modulus of 220GPa; increase the temperature to 2900°C at a rate of 5°C / min under the protection of argon and keep the temperature constant for 1h, and obtain a graphitized fiber with a tensile strength of 3300MPa and an elastic modulus of 710GPa.

[0108] Example 4

[0109] S1, distilling 18700kg coal tar at 150-200°C to obtain 374kg aromatic fraction as raw material 1; distilling 18700kg coal tar at 200-250°C to obtain 1500kg aromatic fraction as raw material 2;

[0110] S2, 370kg of raw material 1 and 1480kg of carbon tetrachloride were added to a reactor, heated to 75°C, condensed and refluxed in the reaction process, reacted for 3.5h after chlorine was introduced, and carbon tetrachloride was recovered by distillation to obtain 350kg of activated fraction 1; 1000kg of raw material 2 and 4000kg of carbon tetrachloride were added to a reactor, heated to 75°C, condensed and refluxed in the reaction process, reacted for 3.5h after chlorine was introduced, and carbon tetrachloride was recovered by distillation to obtain 950kg of activated fraction 2;

[0111] S3, 320 kg of activated fraction 1, 523 kg of activated fraction 2, 28 kg of coal tar fraction extracted by distillation at 200-250 ° C, and 26 kg of coal tar fraction extracted by distillation at 80-150 ° C were placed in a quartz glass reactor, a spherical condenser was vertically installed on the upper part of the reaction vessel, and N with a flow rate of 5 L / min was introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 170°C at a heating rate of 4°C / min and kept constant for 1 hour, and then raised to 300°C and kept constant for 5 hours, to obtain a synthetic asphalt precursor with a softening point of 59°C;

[0112] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into a high-temperature polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 After purging for 25 minutes, the reaction pressure was normal pressure, and the mixture was stirred at a stirring rate of 100 rpm / min. The temperature was first increased to 340°C at a heating rate of 5°C / min and kept constant for 0.5h, and then increased to 420°C at a heating rate of 2°C / min and kept constant for 7h to obtain the matrix asphalt.

[0113] S5, the base pitch is purged with nitrogen at 10 L / min for 2 h to obtain a spinnable mesophase pitch having a softening point of 266°C, a mesophase content of 100%, a coking value of 86%, and an ash content of less than 0.001%;

[0114] S6. Place the spinnable mesophase asphalt into a melt spinning machine, gradually increase the temperature to 370°C to continuously spin fiber filaments with a diameter of 10 microns; after oxidation at 290°C, increase the temperature to 1000°C at a heating rate of 4°C / min under the protection of nitrogen and keep the temperature constant for 0.5h, and obtain a carbon fiber with a tensile strength of 1356MPa and an elastic modulus of 210GPa; increase the temperature to 2900°C at a heating rate of 5°C / min under the protection of argon and keep the temperature constant for 1h, and obtain a graphitized fiber with a tensile strength of 3400MPa and an elastic modulus of 810GPa.

[0115] Example 5

[0116] S1. Distill 18700 kg of coal tar at 225-270° C. to obtain 1100 kg of aromatic fraction as a raw material;

[0117] S2, adding 400 kg of aromatic hydrocarbon fraction and 80 kg of chloromethylnaphthalene into a reactor, stirring and mixing evenly, reacting at 240° C. for 8 h, and obtaining 430 kg of activated coal tar fraction;

[0118] S3, 360 kg of activated coal tar fraction and 30 kg of coal tar fraction extracted by distillation at 70-110 °C were placed in a polymerization reaction vessel, a spherical condenser was vertically installed on the upper part of the reaction vessel, and then N2 with a flow rate of 5 L / min was introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 180°C at a heating rate of 4°C / min and kept constant for 1 hour, and then raised to 320°C and kept constant for 2 hours, to obtain a synthetic asphalt precursor with a softening point of 118°C;

[0119] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into the polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 The reaction was purged for 25 minutes, the reaction pressure was in the autogenous pressure state, and the mixture was stirred at a stirring rate of 100 rpm / min. The temperature was first raised to 290°C at a heating rate of 10°C / min and kept constant for 1 hour, and then raised to 440°C at a heating rate of 3°C / min and kept constant for 6 hours to obtain the matrix asphalt.

[0120] S5, adding the matrix asphalt to a toluene solvent of 1.5 times its mass, stirring at 180°C for 2 hours, filtering, and drying the residue to obtain a spinnable mesophase asphalt having a softening point of 246°C, a mesophase content of 100%, a coking value of 84%, and an ash content of less than 0.001%;

[0121] S6. Place the spinnable mesophase asphalt into a melt spinning machine, gradually increase the temperature to 370°C to continuously spin fiber filaments with a diameter of 10 microns; after oxidation at 280°C, increase the temperature to 1000°C at a heating rate of 4°C / min under the protection of nitrogen and keep the temperature constant for 0.5h, and obtain a carbon fiber with a tensile strength of 1266MPa and an elastic modulus of 190GPa; increase the temperature to 2900°C at a heating rate of 5°C / min under the protection of argon and keep the temperature constant for 1h, and obtain a graphitized fiber with a tensile strength of 3000MPa and an elastic modulus of 800GPa.

[0122] Example 6

[0123] S1, distill 18700kg coal tar at 150-200°C to obtain 374kg fraction as raw material 1; distill 18700kg coal tar at 200-250°C to obtain 1500kg fraction as raw material 2;

[0124] S2, add 370kg of raw material 1 and 80kg of p-chlorodiphenyl into the reactor, stir and mix evenly, react at 160°C for 12h, and obtain 400kg of activated fraction 1; add 1000kg of raw material 2 and 210kg of p-chlorodiphenyl into the reactor, stir and mix evenly, react at 160°C for 15h, and obtain 1010kg of activated fraction 2;

[0125] S3, 360 kg of activated fraction 1, 900 kg of activated fraction 2 and 200 kg of coal tar fraction extracted by distillation at 80-150 °C were placed in a polymerization reaction vessel, a spherical condenser was vertically installed on the upper part of the reaction vessel, and then N2 with a flow rate of 5 L / min was introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 180°C at a heating rate of 4°C / min and kept constant for 1 hour, and then raised to 320°C and kept constant for 2 hours, to obtain a synthetic asphalt precursor with a softening point of 128°C;

[0126] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into the polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 The reaction was purged for 25 minutes, the reaction pressure was in the autogenous pressure state, and the mixture was stirred at a stirring rate of 100 rpm / min. The temperature was first raised to 290°C at a heating rate of 10°C / min and kept constant for 1 hour, and then raised to 440°C at a heating rate of 3°C / min and kept constant for 6 hours to obtain the matrix asphalt.

[0127] S5, the base pitch is purged with nitrogen at 10 L / min for 2 h to obtain a spinnable mesophase pitch having a softening point of 276°C, a mesophase content of 100%, a coking value of 86%, and an ash content of less than 0.001%;

[0128] S6. Place the spinnable mesophase asphalt into a melt spinning machine, gradually increase the temperature to 370°C to continuously spin fiber filaments with a diameter of 9 microns; after oxidation at 280°C, increase the temperature to 1000°C at a heating rate of 4°C / min under the protection of nitrogen and keep the temperature constant for 0.5h, and obtain a carbon fiber with a tensile strength of 1266MPa and an elastic modulus of 220GPa; increase the temperature to 2900°C at a heating rate of 5°C / min under the protection of argon and keep the temperature constant for 1h, and obtain a graphitized fiber with a tensile strength of 3000MPa and an elastic modulus of 760GPa.

[0129] Comparative Example 1

[0130] S1. Distill 210,000 kg of coal tar at 80-150° C. to extract 2,000 kg of aromatic fraction as raw material;

[0131] S2, adding 1000kg of aromatic hydrocarbon fraction and 4000kg of carbon tetrachloride into a reactor, heating to 75°C, condensing and reflux during the reaction process, introducing chlorine gas and reacting for 3.5h, distilling and recovering carbon tetrachloride to obtain 850kg of activated coal tar fraction;

[0132] S3, 620 kg of activated coal tar fraction and 61 kg of coal tar fraction extracted by distillation at 80-110 ° C were placed in a polymerization reaction vessel, a spherical condenser was vertically installed on the upper part of the reaction vessel, and then N with a flow rate of 5 L / min was introduced. 2 , the stirring rate was 350 rpm / min, and the temperature was raised to 230°C at a heating rate of 4°C / min and kept at this temperature for 3 hours, and then raised to 330°C and kept at this temperature for 5 hours, to obtain a synthetic asphalt precursor with a softening point of 128°C;

[0133] S4, synthesizing asphalt precursor in N 2 After cooling to 160°C under protection, the mixture was taken out and added into the polymerization reactor according to the corresponding capacity; the polymerization reactor was equipped with an anchor-type stirring paddle and N with a flow rate of 5 L / min was introduced. 2 After purging for 25 minutes, the reaction pressure was in the autogenous pressure state, and the mixture was stirred at a stirring rate of 100 rpm / min. The temperature was first raised to 300°C at a heating rate of 10°C / min and kept constant for 3 hours, and then raised to 430°C at a heating rate of 3°C / min and kept constant for 8 hours to obtain the matrix asphalt.

[0134] S5. The base asphalt was purged with nitrogen at 10 L / min for 2 h to obtain the mesophase asphalt, which had a softening point of 296°C, a mesophase content of 99%, a coking value of 93%, an ash content of less than 0.01%, and obvious coking and poor fluidity;

[0135] S6. Put the mesophase pitch into a melt spinning machine and gradually increase the temperature to 400°C, but continuous spinning is still not possible.

[0136] Figure 2 The GC-MS spectrum of the activated coal tar fraction product prepared by direct halogenation of the aromatic fraction extracted by coal tar distillation in Example 1. Figure 2 The GC-MS spectrum shows that the aromatic fraction is extracted from coal tar, and the activated fraction is prepared by chlorination treatment, and the directional reaction effect is excellent. Figure 3 This is a polarized microscopic photograph of the spinnable mesophase pitch obtained in Example 1. Figure 3It can be seen that the mesophase asphalt has an anisotropic structure, a coking value higher than 80%, and an mesophase content of up to 100%. It is a wide-area streamlined structure with good optical texture distribution, good directional arrangement and orderliness, which also proves that the synthetic mesophase asphalt has good melt fluidity. Figure 4 This is a SEM image of the carbon fiber obtained in Example 1. Figure 4 It can be seen that the carbon fiber carbon layers of the present invention are arranged in order.

[0137] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for preparing spinnable mesophase pitch from coal tar fractions, characterized in that: The following steps are involved: S1, extracting aromatic fractions of different distillation ranges from coal tar by distillation, and selecting one or more aromatic fractions of distillation ranges as raw materials; S2, performing activation treatment on the selected one or more distillation range aromatic fractions to obtain one or more activated coal tar fractions; S3, one or more activated coal tar fractions in step S2 and one or more unactivated coal tar fractions are mixed in proportion as a synthetic asphalt raw material, and a polymerization reaction is carried out at 120-350° C. under the protection of an inert atmosphere, and the mixture is cooled to obtain a synthetic asphalt precursor having a softening point of 40-130° C. The method for obtaining the unactivated coal tar fraction is the same as the method for obtaining the aromatic fraction in step S1; In the synthetic asphalt raw material, the total proportion of activated coal tar fraction is 10wt%~100wt%; S4, under the protection of an inert atmosphere, further polymerizing the synthetic asphalt precursor at 200-440° C. to obtain a matrix asphalt; S5, subjecting the matrix pitch to vacuum distillation, solvent extraction or inert gas purging to obtain a spinnable mesophase pitch; Wherein, in step S2, the activation treatment method is: adding one or more selected coal tar aromatic fractions and solvent carbon tetrahalide in a mass ratio of (2-5): (10-30) to a reaction device, heating to 40-150° C., introducing halogen gas, reacting for 3-20 hours, condensing and refluxing during the reaction process, and after the reaction is completed, distilling and recovering the solvent carbon tetrahalide for recycling to obtain an activated coal tar fraction; the solvent carbon tetrahalide is carbon tetrachloride or carbon tetrabromide, and the halogen gas is chlorine or bromine; Alternatively, the aromatic hydrocarbon fractions of one or more selected distillation ranges are uniformly mixed with a highly active halide in a mass ratio of 1:(0.1-10), and reacted at 120-250° C. for 1-20 hours to obtain an activated coal tar fraction; the highly active halide includes but is not limited to a mixture of one or more of halobenzenes, halogenated methylbenzenes, dihalogenated benzenes, halogenated naphthalenes, halogenated methylnaphthalenes, halogenated alkanes, and halogenated olefins; Wherein, in step S3, the conditions for carrying out the polymerization reaction at 120-350°C under the protection of an inert atmosphere are: first heating to 120-270°C and keeping the temperature constant for 0.5-10h, then continuing to heating to 280-350°C and keeping the temperature constant for 0.5-10h, with a heating rate of 1-10°C / min respectively; condensing and reflux during the reaction; the cooling temperature is below 160°C; Among them, in step S4, the conditions for further polymerization reaction of the synthetic asphalt precursor at 200~440℃ under the protection of inert atmosphere are: first heating to 200~350℃ and keeping the temperature constant for 0.5~20h, then heating to 360~440℃ and keeping the temperature constant for 0.5~20h, and the heating rate is 2~10℃ / min.

2. The method for preparing spinnable mesophase pitch from coal tar fractions according to claim 1, characterized in that: In step S1, the coal tar is coal tar produced by coking coking coal at 950-1050°C, coal tar produced by pyrolysis of low-rank coal at 500-700°C, or coal tar produced by pyrolysis of low-rank coal at 300-450°C; The distillation is atmospheric distillation or reduced pressure distillation at 80-400°C; The aromatic fraction includes, but is not limited to, a mixture of one or more of a benzene-rich aromatic fraction, a naphthalene-rich aromatic fraction, a phenol-rich aromatic fraction, an anthracene-rich aromatic fraction, a phenanthrene-rich aromatic fraction, a quinone-rich aromatic fraction and a quinoline-rich aromatic fraction.

3. The method for preparing spinnable mesophase pitch from coal tar fraction according to claim 1, characterized in that: In step S2, the activated coal tar fraction includes but is not limited to a mixture of one or more of halogenated benzene-rich aromatics, halogenated naphthalene-rich aromatics, halogenated phenol-rich aromatics, halogenated anthracene-rich aromatics, halogenated phenanthrene-rich aromatics, halogenated quinone-rich aromatics and halogenated quinoline-rich aromatics; The activated coal tar fraction is a monohalogenated product or a polyhalogenated product at any halogenation site; The unactivated coal tar fraction includes, but is not limited to, one or more of a benzene-rich aromatic fraction, a naphthalene-rich aromatic fraction, a phenol-rich aromatic fraction, an anthracene-rich aromatic fraction, a phenanthrene-rich aromatic fraction, a quinone-rich aromatic fraction and a quinoline-rich aromatic fraction.

4. The method for preparing spinnable mesophase pitch from coal tar fractions according to claim 1, characterized in that: The aromatic fraction obtained by atmospheric distillation of the coal tar at 80°C to 150°C is activated to obtain activated fraction 1, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 150°C and less than or equal to 200°C is activated to obtain activated fraction 2, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 200°C and less than or equal to 250°C is activated to obtain activated fraction 3, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 250°C and less than or equal to 300°C is activated to obtain activated fraction 4, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 300°C and less than or equal to 350°C is activated to obtain activated fraction 5, the aromatic fraction obtained by atmospheric distillation of the coal tar at a temperature greater than 350°C and less than or equal to 400°C is activated to obtain activated fraction 6, and the pressure of the vacuum distillation is below 13kPa; In the synthetic asphalt raw material, the ratio of activated fraction 1 used in the preparation is 0~30wt%, the ratio of activated fraction 2 used in the preparation is 0~60wt%, the ratio of activated fraction 3 used in the preparation is 0~60wt%, the ratio of activated fraction 4 used in the preparation is 0~60wt%, the ratio of activated fraction 5 used in the preparation is 0~60wt%, and the ratio of activated fraction 6 used in the preparation is 0~60wt%.

5. The method for preparing spinnable mesophase pitch from coal tar fractions according to claim 1, characterized in that: In step S3, the conditions for carrying out the polymerization reaction at 120-350° C. under the protection of an inert atmosphere are: The inert atmosphere is one or more of nitrogen, helium and argon, and the flow rate of the inert atmosphere is 0.5-10 L / min; the reaction is carried out under stirring, and the stirring rate is 80-1000 rpm / min.

6. The method for preparing spinnable mesophase pitch from coal tar fractions according to claim 1, characterized in that: In step S4, the conditions for further polymerization reaction of the synthetic asphalt precursor at 200~440°C under the protection of an inert atmosphere are: the inert atmosphere is one or more of nitrogen, helium and argon, and the inert atmosphere flow rate is 0.5~10L / min; the reaction is carried out under stirring, and the stirring rate is 60~1200rpm / min.

7. The method for preparing spinnable mesophase pitch from coal tar fractions according to claim 1, characterized in that: In step S5, the temperature of the reduced pressure distillation treatment is 340-400° C., the vacuum degree is -80--110 kPa, and the time is 0.5-2 h; The solvent used for the solvent extraction is one or more of quinoline, pyridine, washing oil, kerosene, nitrogen methyl pyrrolidone, and toluene. The temperature of the solvent extraction is room temperature or lower than the boiling point of the solvent, the pressure is normal pressure, and the time is 1 to 5 hours; The inert gas purging adopts an inert atmosphere of nitrogen, argon or helium, the purging time is 1 to 5 hours, and the purging gas rate is 1 to 20 L / min.

8. A method for preparing mesophase pitch-based carbon fibers using the spinnable mesophase pitch prepared by the method according to any one of claims 1 to 7, characterized in that: The spinnable mesophase pitch is melt-spinned to obtain fiber precursors, and the fiber precursors are oxidized, carbonized and graphitized under an inert atmosphere to obtain mesophase pitch-based carbon fibers.

9. The method for preparing mesophase pitch-based carbon fiber according to claim 8, characterized in that: The melt spinning temperature is 340-390°C; The oxidation temperature is 280-360°C; The inert atmosphere is one of nitrogen, helium and argon, and the gas flow rate is 1-10 L / min; The carbonization temperature is 700-1400°C and the time is 0.1-3h; The graphitization temperature is 2800-3000°C and the time is 0.5-3h; The heating rates of carbonization and graphitization are 0.5-5°C / min respectively.

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