A method for the synthetic preparation of a spinning grade mesophase pitch

Abstract

The present application belongs to the technical field of coal chemical industry, and particularly relates to a method for preparing spinning-grade mesophase pitch. The method comprises the following steps: (1) adding a catalyst FeBr3 into a 300-360 DEG C initial distillate of coal tar, stirring and reacting to obtain a solid-liquid mixed product; (2) filtering the solid-liquid mixed product obtained in step (1) to separate a liquid-phase mesophase pitch precursor and a solid-phase catalyst FeBr3 and surface carbon; (3) performing a thermal polycondensation reaction on the liquid-phase mesophase pitch precursor obtained in step (2) to obtain a mesophase pitch crude product; and (4) performing a reduced-pressure polycondensation on the mesophase pitch crude product obtained in step (3) to remove small-molecule compounds and obtain a mesophase pitch with a mesophase content of greater than or equal to 90%. The method can solve the problems of high impurity content and difficulty in removal, long reaction time, low yield and low product performance in the production of mesophase pitch according to the prior art.

Description

Technical Field

[0001] This invention belongs to the technical field of coal chemical industry, specifically relating to a method for synthesizing and preparing spinning-grade mesophase pitch. Background Technology

[0002] Mesophase pitch is a mixture of various planar macromolecular polycyclic aromatic hydrocarbons that aggregate to form an optically anisotropic liquid crystal phase due to intermolecular π-π bond interactions. Mesophase pitch is readily graphitized and exhibits good fluidity at certain temperatures, making it an important raw material for preparing high-performance carbon materials. In particular, high-performance carbon fibers prepared using mesophase pitch possess unique properties such as high thermal conductivity and high modulus. Therefore, mesophase pitch-based carbon fiber materials are widely used in cutting-edge fields such as aerospace, defense, new energy storage devices, and the nuclear energy industry (nuclear reactors).

[0003] Currently, the raw materials used to prepare mesophase pitch are mainly petroleum pitch (including heavy oil, catalytic cracking slurry, etc.), coal pitch (including coal tar, coal hydrogenation liquefaction residue, etc.), and pure aromatic hydrocarbons and their blends. These raw materials are purified and then used to prepare mesophase pitch via thermal polycondensation or by catalytic condensation of aromatic compounds.

[0004] Due to the complexity of geological conditions during coal and petroleum formation and the influence of residues during refining, the composition of coal tar and petroleum residue is complex and unstable, containing trace impurities that are difficult to remove, directly affecting the properties of mesophase pitch. Mesophase pitch, primarily used as a precursor for advanced graphite materials, is widely applied in high thermal conductivity, high modulus, and high energy storage carbon materials. It requires excellent properties such as high flowability (easy processing), easy orientation, few defects, and easy graphitization, all of which necessitate high purification of the mesophase pitch.

[0005] It is evident that the structure and properties of mesophase pitch are highly dependent on raw materials and preparation processes. For example, coal-based pitch, due to its high aromaticity and near-disc-like molecular structure, often requires hydrogenation or co-carbonization with other hydrogen donors to increase the hydrogen-to-carbon ratio and achieve better fluidity, thus enabling the preparation of high-quality mesophase pitch. Petroleum-based pitch has a wide range of sources and complex composition; the presence of heteroatoms significantly affects the structure and properties of the prepared mesophase pitch, necessitating methods to improve the purity and stability of the raw materials. Pure aromatics possess excellent high purity and stability, but cannot be directly thermally polymerized; catalysts are required to prepare mesophase pitch under conventional conditions. Furthermore, the high cost of pure aromatics significantly increases the production cost of mesophase pitch.

[0006] Existing technologies often employ a series of complex refining processes on coal tar and petroleum residue, including desalting, acid washing, distillation, solvent extraction, and centrifugal filtration, before preparing mesophase pitch via thermal polycondensation. However, these methods can only remove most inorganic solid impurities, large molecular weight heavy aromatics, and high-boiling-point heavy components containing impurities; these insoluble solid components still remain at levels exceeding 100 ppm. Furthermore, it is even more difficult to remove ionic heteroatoms from coal tar and petroleum residue, resulting in low-quality mesophase pitch produced from these materials, unsuitable for the preparation of high-performance carbon fibers and other products. Therefore, existing processes are not only complex and costly, sometimes exceeding the cost of using pure compounds as raw materials, but also fail to completely remove impurities from the produced mesophase pitch, typically exceeding 100 ppm.

[0007] To address the inherent defects of coal tar pitch and petroleum residue pitch, researchers have developed a catalyst-based synthesis method for mesophase pitch. Catalytic synthesis of mesophase pitch refers to the preparation of mesophase pitch using pure compounds such as naphthalene and anthracene, or other relatively pure compounds, through a catalytic reaction; rather than using mixtures containing impurities like petroleum residue and coal tar. Therefore, catalytic synthesis of mesophase pitch only requires removing the catalyst after the reaction is complete to produce pure mesophase pitch, avoiding the problems caused by impurities in coal tar and petroleum residue feedstocks.

[0008] In addition, the method of preparing mesophase pitch using catalysis uses pure compounds as raw materials. Therefore, although the raw materials have high purity and regular molecular structure, the molecular weight distribution is relatively narrow.

[0009] Under the action of catalysts such as Lewis acids, the reaction process can be effectively controlled to generate long-chain aromatic hydrocarbon molecules with high molecular planarity; at the same time, it can make the pitch macromolecular chain contain short alkyl and cycloalkane structures, giving mesophase pitch extremely high rheological properties. These properties are particularly important for the spinning properties of synthesized mesophase pitch.

[0010] I. Mochida of Japan has disclosed a process for producing mesophase pitch using an HF / BF3 catalyst, which solves the problem of AlCl3 catalyst residue. However, the process for producing mesophase pitch using an HF / BF3 catalyst requires highly airtight equipment and corrosion-resistant materials, and the production process is difficult to control, making large-scale production impossible in ordinary laboratories or factories.

[0011] Japanese patents JP1-139621 and JP1-254796 employ HF / BF3 catalysis to produce mesophase pitch for spinning with low softening point and high mesophase content. However, this method involves reaction pressures reaching tens of megapascals, and the large amount of HF / BF3 causes severe corrosion to the equipment. Furthermore, it inevitably introduces some metal ions, negatively impacting post-processing and product performance. Additionally, it presents challenges related to high raw material costs, operational safety, environmental impact, and human toxicity, thus hindering the industrialization of this process.

[0012] In recent years, some researchers have used catalysts to prepare mesophase pitch from coal liquefaction residues. For example, patent CN105838409A discloses a method for producing mesophase pitch from coal liquefaction residues. The method involves mixing the coal liquefaction residues with an extractant for extraction to obtain refined pitch. Then, a high-pressure reaction is carried out in the presence of at least one catalyst, AlCl3, FeCl3, and ZrCl4, to obtain the mesophase pitch. However, this method still struggles to remove impurities from the mesophase pitch, limiting its application. Summary of the Invention

[0013] This invention addresses the shortcomings of existing technologies by providing a method for synthesizing and preparing spinning-grade mesophase pitch. This method can solve the problems of high impurity content, difficulty in removal, long reaction time, low yield and product performance in the production of mesophase pitch by current technologies.

[0014] This invention discloses for the first time a process for preparing mesophase pitch by adding FeBr3 as a catalyst to the initial fraction of coal tar at 300-360℃. Due to the directional catalytic effect of FeBr3, the aromatic ring molecular structure of the final mesophase pitch is guaranteed.

[0015] The specific technical solution is as follows:

[0016] A method for synthesizing and preparing spinning-grade mesophase pitch includes the following steps:

[0017] (1) Add the catalyst FeBr3 to the initial fraction of coal tar at 300-360℃ to obtain a mixture;

[0018] The resulting mixture was added to a reactor under a nitrogen atmosphere and stirred at a temperature of 150–200 °C and a pressure of 0.2–0.6 MPa to obtain a solid-liquid mixture.

[0019] The initial fraction of coal tar at 300-360℃ mainly consists of anthracene oil (300-330℃) and dianthracene oil (330-360℃), primarily composed of anthracene, naphthalene, and pyridine compounds. Based on the principle of distillation separation, the initial fraction of coal tar at 300-360℃ minimizes impurities, approaching a near-impurity state. The impurity content in this fraction is below 50 ppm, which will not affect the quality of the mesophase pitch, eliminating the need for further impurity reduction. Furthermore, this fraction is less expensive than pure aromatic hydrocarbons such as industrial naphthalene and anthracene.

[0020] The initial fraction of coal tar at 300-360℃ mostly possesses a three-ring aromatic structure, while mesophase pitch is a mixture of various polycyclic aromatic hydrocarbons. In other words, mesophase pitch can be considered as a further enlargement of the three-ring molecules; when the number of aromatic ring molecules increases to a certain amount, mesophase pitch can be formed. Therefore, the initial fraction of coal tar at 300-360℃ is more likely to form mesophase pitch precursors through catalysis.

[0021] Using FeBr3 as a catalyst, cationic polymerization of aromatic hydrocarbons such as anthracene, naphthalene, and pyridine is promoted. The reaction products are mainly trimers, tetramers, and pentamers of aromatic rings, and contain cycloalkane structures, methyl and methylene side chains, which are easy to form mesophase pitch precursors with more orderly internal molecular arrangement.

[0022] The FeBr3 catalyst differs from the catalytic reactions of AlCl3, FeCl3, Fe(NO3)3, and ZrCl4 in the following specific ways:

[0023] ① The catalytic reaction using FeBr3 catalyst has strong controllability. Because the cationic polymerization reaction catalyzed by AlCl3, FeCl3, Fe(NO3)3, ZrCl4, etc. is fast and exothermic, the reaction system can easily rise to a high temperature of 300-400℃ or even higher in a short time, which leads to runaway reaction and easy formation of carbon deposits on the catalyst surface.

[0024] FeBr3 catalyst can effectively control the reaction temperature below 200℃, because FeBr3 catalyst will decompose and lose its catalytic activity above 200℃. This property effectively controls the reaction temperature from becoming too high.

[0025] ② The FeBr3 catalyst results in high yield and low coking. Because the catalytic reaction of the FeBr3 catalyst occurs below 200℃, the amount of coking produced is low, and the amount of oligomers converted is high.

[0026] ③ The FeBr3 catalyst has low cost. The low cost of the FeBr3 catalyst itself and its high catalytic yield make the method of this invention less expensive overall than preparation methods using catalysts such as AlCl3, FeCl3, Fe(NO3)3, and ZrCl4.

[0027] The reaction temperature should be controlled between 150 and 200°C. If the reaction temperature exceeds 200°C, it will cause over-reaction, resulting in too much solid product and too little liquid phase in the solid-liquid mixture, making it difficult to separate.

[0028] (2) The solid-liquid mixture obtained in step (1) is filtered to separate the liquid phase mesophase asphalt precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0029] Liquid mesophase pitch precursors are mainly composed of aromatic ring trimers, tetramers, and pentamers, and contain cycloalkane structures, methyl and methylene side chains.

[0030] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction under N2 atmosphere to prepare crude mesophase pitch.

[0031] Liquid-phase mesophase pitch precursors share the basic characteristics of mesophase pitch, all being compounds containing polycyclic aromatic hydrocarbons. Through thermal condensation reactions, the number of aromatic rings in the polycyclic aromatic liquid-phase mesophase pitch precursors further increases, thus forming mesophase pitch.

[0032] (4) The crude mesophase pitch obtained in step (3) is subjected to reduced-pressure polymerization to remove small molecule compounds, thereby obtaining mesophase pitch with a mesophase content of ≥90%. This step, through reduced-pressure polymerization, allows the small molecule compounds generated during the polymerization reaction to be removed simultaneously.

[0033] The above-mentioned method for synthesizing and preparing spinning-grade mesophase pitch includes the following stages:

[0034] ① First stage of reaction: pressurized catalytic reaction. FeBr3 is added to the initial fraction of coal tar at 300-360℃. FeBr3 acts as a catalyst for the cationic polymerization of high molecular weight compounds, promoting the cationic polymerization reaction of the initial fraction of coal tar at 300-360℃ to form an intermediate phase pitch precursor with a more orderly internal molecular arrangement.

[0035] ② Second stage of the reaction: Atmospheric pressure thermal condensation reaction. During the reaction, condensed-ring aromatic hydrocarbon macromolecules condense to form larger aromatic hydrocarbon molecules, which are arranged in an orderly manner and have a certain orientation, forming an anisotropic liquid crystal phase, namely mesophase pitch. The mesophase pitch precursor obtained by FeBr3 catalysis contains condensed-ring aromatic hydrocarbon macromolecules with consistent structure and a certain orientation, which is conducive to the formation of chain molecular structures of aromatic rings.

[0036] ③ The third stage of the reaction: compression polymerization, which extracts the small molecule compounds and compounds that have not formed the mesophase generated in the first stage catalytic reaction, increases the mesophase content of the product, controls the softening point of the mesophase pitch, and prepares high-quality mesophase pitch.

[0037] In this invention, the catalyst FeBr3 in step (1) of the method for synthesizing and preparing spinning-grade mesophase pitch is anhydrous FeBr3 with analytical purity.

[0038] In this invention, in step (1) of the method for synthesizing and preparing spinning-grade mesophase pitch, the mass ratio of FeBr3 to the initial fraction of coal tar at 300-360℃ is 1 to 5: 100.

[0039] Compared to other catalysts used in the synthesis of mesophase asphalt, FeBr3 catalyst requires a smaller dosage. In existing technologies, during the catalytic reaction of AlCl3, a portion of the AlCl3 becomes carbon-covered on its surface due to the high reaction temperature, thus losing its activity. Therefore, the addition amount is generally 10%-50%, resulting in a large amount of AlCl3 mixed in the product. Even after acid and alkali washing, it still exists in the form of aluminum oxide / hydroxide in a large quantity, which has a certain impact on the mechanical properties of the material. However, the FeBr3 catalyst used in this invention effectively controls the reaction temperature to not exceed 200℃, thus producing less carbon buildup on the surface of the FeBr3 catalyst, and consequently requiring a smaller amount of catalyst, only 1%-5%.

[0040] In this invention, the stirring reaction time in step (1) of the method for synthesizing and preparing spinning-grade mesophase pitch is 2 to 3 hours.

[0041] In this invention, the filtration in step (2) of the method for synthesizing and preparing spinning-grade mesophase pitch uses qualitative filter paper.

[0042] In this invention, the reaction temperature of the thermal polycondensation reaction in step (2) of the method for synthesizing and preparing spinning-grade mesophase pitch is 390-425°C, the reaction pressure is atmospheric pressure, and the reaction time is 2-4 hours.

[0043] In this invention, in step (4) of the method for synthesizing and preparing spinning-grade mesophase pitch, the temperature of the compression polymerization is 390-420℃, the compression polymerization time is 10-30 min, and the compression polymerization pressure is -0.1--0.05 MPa.

[0044] A spinning-grade mesophase pitch synthesized by the above method has a softening point of 290-350℃; ash content <50ppm; mesophase content of 90-100%; and a suitable spinning viscosity temperature range of <380℃ (viscosity ≤12Pa·s).

[0045] The above-mentioned method synthesizes and prepares spinning-grade mesophase pitch, or the above-mentioned spinning-grade mesophase pitch is used in the preparation of high thermal conductivity carbon fibers.

[0046] The beneficial effects of the present invention are as follows: The method for synthesizing and preparing spinning-grade mesophase pitch described in the present invention uses FeBr3 as a catalyst and synergistically combines it with the initial distillation fraction of raw coal tar at 300-360℃ to prepare mesophase pitch.

[0047] First, the initial distillation of the raw coal tar at 300-360℃ is fractionally separated. The raw material is mainly composed of hydrocarbon elements, and the content of other impurity elements such as minerals, S, and N is extremely low, less than 50ppm. It can be seen that the raw material is basically free of impurities.

[0048] Then, compared with existing technologies, the catalytic reaction using FeBr3 catalyst has better controllability, higher yield and lower cost, with the following specific advantages:

[0049] (1) The aromatic oligomers generated by FeBr3 catalytic reaction have a regular molecular structure: Due to the directional catalytic effect of FeBr3, the aromatic rings are arranged in a longitudinal manner by condensation in the process of aromatic compounds condensing into macromolecules, which ensures the large planar molecular structure of the final mesophase pitch and the resulting mesophase pitch has a low softening point.

[0050] Cata-condensed arrangements are formed when two aromatic rings share a common carbon atom; their arrangement is primarily linear, as shown in the following equation:

[0051] (2) FeBr3 catalyst requires less dosage and is easy to remove: FeBr3 catalyst has good controllability of catalytic temperature and can control the catalytic reaction temperature within 200℃. As a result, the catalyst surface has less carbon, which will not cause catalyst deactivation and make it unusable. Therefore, compared with other catalytic synthesis of mesophase asphalt, FeBr3 catalyst requires less dosage.

[0052] In addition, the catalytic reaction product is a solid-liquid mixture, with the intermediate asphalt precursor aromatic oligomer in liquid state and the FeBr3 catalyst in solid state. Thus, after the reaction, the FeBr3 catalyst can be directly separated by filtration, which is simple and convenient. The liquid intermediate asphalt precursor contains almost no impurities such as catalyst, and the obtained intermediate phase content is greater than 90%. The final prepared intermediate phase asphalt has excellent performance.

[0053] (3) The FeBr3 catalytic reaction is easy to control and has low equipment requirements: FeBr3 catalyst is a solid powder, which makes the operation process easier to control compared to gaseous catalysts. The reaction process has low requirements for equipment airtightness, pressure resistance and corrosion resistance, thus saving equipment costs.

[0054] In summary, the above-described synthesis method allows for the control of mesophase pitch molecules, resulting in mesophase pitch with a low softening point, good rheological properties, high solubility, low impurity content, and a single molecular orientation. Compared to mesophase pitch produced by traditional methods, which has an impurity content greater than 100 ppm and is unspinnable, the method of this invention produces mesophase pitch with an impurity content below 50 ppm, achieving spinnable performance and suitable for preparing mesophase pitch carbon fibers. Traditional methods for producing mesophase pitch typically take more than 10 hours (e.g., CN105838409A), while this invention requires at most 7.5 hours. The yield of mesophase pitch produced by the method of this invention is 17-20%, while the yield of traditional methods is generally 10-15%. Attached Figure Description

[0055] Figure 1 A polarizing microscope image of the mesophase pitch prepared in Example 1. Detailed Implementation

[0056] The technical solution of the present invention will be further described below, but the scope of protection of the present invention is not limited thereto.

[0057] 1. Raw material source: FeBr3 was purchased from Bailingwei Chemical Reagent Company, analytical grade, >98%, moisture: none.

[0058] The 300-360℃ initial fraction of coal tar comes from the 300-360℃ fraction obtained by distilling crude tar from coking plants.

[0059] 2. Determination of mesophase content: The commonly used method in this field to determine the content of mesophase is to calculate the area occupied by the mesophase under a polarizing microscope.

[0060] 3. Softening point determination: The needle insertion method is commonly used.

[0061] Example 1

[0062] The specific steps of the method for synthesizing and preparing spinning-grade mesophase pitch are as follows:

[0063] (1) Add 10g of catalyst FeBr3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0064] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 160℃ and a pressure of 0.6MPa to obtain a solid-liquid mixture.

[0065] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase pitch precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0066] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 425°C, a reaction time of 2 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0067] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0068] A mesophase pitch with a mesophase content of 90% was obtained, which had a softening point of 305℃ and a yield of 19%.

[0069] 20g of the mesophase pitch prepared in this example can be used to prepare continuous pitch fibers at 345℃, N2 pressure of 0.010MPa, and take-up drum speed of 300r / min. The average diameter of the pitch fibers is 11.75μm, and the continuous spinning time is greater than 5min.

[0070] Example 2

[0071] The specific steps of the method for synthesizing and preparing spinning-grade mesophase pitch are as follows:

[0072] (1) Add 15g of catalyst FeBr3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0073] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2.5 h at a temperature of 170℃ and a pressure of 0.6 MPa to obtain a solid-liquid mixture.

[0074] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase pitch precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0075] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 420°C, a reaction time of 3 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0076] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0077] A mesophase pitch with a mesophase content of 95% was obtained, which had a softening point of 310℃ and a yield of 18%.

[0078] Example 3

[0079] The specific steps of the method for synthesizing and preparing spinning-grade mesophase pitch are as follows:

[0080] (1) Add 20g of catalyst FeBr3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0081] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 155℃ and a pressure of 0.6MPa to obtain a solid-liquid mixture.

[0082] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase pitch precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0083] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0084] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0085] Mesophase pitch with a mesophase content of 96% was obtained, with a softening point of 312℃ and a yield of 19%.

[0086] Example 4

[0087] The specific steps of the method for synthesizing and preparing spinning-grade mesophase pitch are as follows:

[0088] (1) Add 5g of catalyst FeBr3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0089] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 185℃ and a pressure of 0.5MPa to obtain a solid-liquid mixture.

[0090] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase pitch precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0091] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0092] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0093] A mesophase pitch with a mesophase content of 90% was obtained, which had a softening point of 302℃ and a yield of 19%.

[0094] Example 5

[0095] The specific steps of the method for synthesizing and preparing spinning-grade mesophase pitch are as follows:

[0096] (1) Add 25g of catalyst FeBr3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0097] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 165℃ and a pressure of 0.4MPa to obtain a solid-liquid mixture.

[0098] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase pitch precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0099] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0100] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0101] Mesophase pitch with a mesophase content of 97% was obtained, with a softening point of 310℃ and a yield of 17%.

[0102] Comparative Example 1

[0103] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0104] (1) Take 500g of the initial fraction of coal tar at 340-360℃ and stir it uniformly in a reactor at 430℃ for 5 hours. The reaction pressure is 0.6MPa and the reaction is carried out under N2 atmosphere to obtain a solid-liquid mixture.

[0105] (2) The solid-liquid mixture obtained in step (1) was reacted at 420℃ and -0.1MPa for 0.5 hours to remove small molecule compounds and obtain asphalt with an intermediate phase content of 85% and a softening point of 320℃.

[0106] The resulting solid-liquid mixture, when cooled to room temperature, consists of a solid phase of mesophase pitch and a liquid phase of light tar that has not yet formed a mesophase.

[0107] This comparative example did not include the catalyst FeBr3. Although the initial fraction of coal tar at 340-360℃ can also react to generate mesophase pitch, the mesophase content is low and the softening temperature is high, which is not conducive to applications such as spinning.

[0108] Comparative Example 2

[0109] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0110] (1) Add 50g of catalyst FeBr3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0111] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 175℃ and a pressure of 0.4MPa to obtain a solid-liquid mixture.

[0112] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase pitch precursor and the solid phase catalyst FeBr3 and its surface carbon.

[0113] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0114] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0115] A mesophase pitch with a mesophase content of 95% was obtained, which had a softening point of 330℃ and a yield of 10%.

[0116] Comparative Example 3

[0117] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0118] (1) Add 20g of catalyst FeCl3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0119] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 210℃ and a pressure of 0.5MPa to obtain a solid-liquid mixture.

[0120] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase asphalt precursor and the solid phase catalyst FeCl3 and its surface carbon.

[0121] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0122] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0123] A mesophase pitch with a mesophase content of 85% was obtained, which had a softening point of 325℃ and a yield of 10%.

[0124] Comparative Example 4

[0125] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0126] (1) Add 20g of catalyst Fe(NO3)3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0127] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 240℃ and a pressure of 0.5MPa to obtain a solid-liquid mixture.

[0128] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase asphalt precursor and the solid phase catalyst Fe(NO3)3 and its surface carbon.

[0129] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0130] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0131] A mesophase pitch with a mesophase content of 80% was obtained, which had a softening point of 325℃ and a yield of 8%.

[0132] Comparative Example 5

[0133] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0134] (1) Add 20g of catalyst AlCl3 to the initial fraction of 500g coal tar at 340-360℃ to obtain a mixture;

[0135] The resulting mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 230℃ and a pressure of 0.5MPa to obtain a solid-liquid mixture.

[0136] (2) The solid-liquid mixture obtained in step (1) is filtered through qualitative filter paper to separate the liquid phase mesophase asphalt precursor and the solid phase catalyst AlCl3 and its surface carbon.

[0137] (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction at a reaction temperature of 423℃, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0138] (4) The crude mesophase pitch obtained in step (3) is reacted at 420℃ and -0.1MPa for 30 min to remove small molecule compounds.

[0139] A mesophase pitch with a mesophase content of 80% was obtained, which had a softening point of 330℃ and a yield of 9%.

[0140] Comparative Example 6

[0141] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0142] (1) Add 20g of catalyst FeBr3 to 500g of medium-temperature coal tar pitch (ash content <0.3%, softening point 85℃) to obtain a mixture;

[0143] (2) The obtained mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 210℃ and a pressure of 0.5MPa to obtain a solid mixed product.

[0144] (3) The mixture obtained in step (1) is subjected to thermal polycondensation reaction at a reaction temperature of 420°C, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase asphalt.

[0145] A mesophase pitch with a mesophase content of 65% was obtained. The softening point of the mesophase pitch was 355℃ and the ash content was >4% (the catalyst FeBr3 could not be separated and removed).

[0146] Comparative Example 7

[0147] The specific steps of the method for synthesizing and preparing mesophase pitch described in the comparative example are as follows:

[0148] (1) Add 20g of catalyst FeBr3 to 500g of naphthalene pitch (ash content <0.1%, softening point 150℃) to obtain a mixture;

[0149] (2) The obtained mixture was added to a reactor under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 210℃ and a pressure of 0.5MPa to obtain a solid mixed product.

[0150] (3) The mixture obtained in step (1) is subjected to thermal polycondensation reaction at a reaction temperature of 420°C, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase asphalt.

[0151] A mesophase pitch with a mesophase content of 75% was obtained. The softening point of the mesophase pitch was 350℃ and the ash content was >4% (the catalyst FeBr3 could not be separated and removed).

[0152] Comparative Example 8

[0153] (1) Coal liquefaction residue was dissolved in pyridine extractant solution and refined bitumen with carbon content of 89.65% and aromaticity of 0.81 was obtained by extraction.

[0154] (2) Add 20g of catalyst FeBr3 to 500g of refined asphalt (ash content <0.2%, softening point 90℃) obtained in step (1) to obtain a mixture;

[0155] (3) The obtained mixture was added to a reaction vessel under N2 atmosphere and stirred uniformly for 2 hours at a temperature of 210℃ and a pressure of 0.5MPa to obtain a solid-liquid mixture product.

[0156] (4) The liquid product obtained in step (3) is subjected to thermal polycondensation reaction at a reaction temperature of 420°C, a reaction time of 3.5 hours, and a normal pressure N2 atmosphere to prepare crude mesophase pitch.

[0157] A mesophase pitch with a mesophase content of 85% was obtained. The softening point of the mesophase pitch was 335℃ and the ash content was >0.3% (the catalyst FeBr3 could not be separated and removed).

[0158] This invention, based on the inventor's long-term systematic theoretical research, has found a unique pathway for producing mesophase pitch using FeBr3 catalysis in the complex system of polycyclic aromatic hydrocarbon polymerization. Through appropriate process adjustments, the mesophase pitch prepared using this method shows significant improvements over other methods in terms of both catalyst dosage and equipment requirements. Large-scale production of this product will play a major role in promoting product upgrading in related fields.

Claims

1. A method for synthesizing and preparing spinning-grade mesophase pitch, characterized in that, Includes the following steps: (1) Add the catalyst FeBr3 to the initial fraction of coal tar at 300-360℃ to obtain a mixture; The resulting mixture was added to a reactor under N2 atmosphere and stirred at a temperature of 150–200 °C and a pressure of 0.2–0.6 MPa to obtain a solid-liquid mixture. (2) The solid-liquid mixture obtained in step (1) is filtered to separate the liquid phase mesophase asphalt precursor and the solid phase catalyst FeBr3 and its surface carbon. (3) The liquid mesophase pitch precursor obtained in step (2) is subjected to thermal polycondensation reaction under N2 atmosphere to prepare crude mesophase pitch. (4) The crude mesophase pitch obtained in step (3) is subjected to compression polymerization to remove small molecule compounds and obtain mesophase pitch with a mesophase content of ≥90%.

2. The method for synthesizing and preparing spinning-grade mesophase pitch according to claim 1, characterized in that, In step (1), the catalyst FeBr3 is anhydrous FeBr3 with analytical purity.

3. The method for synthesizing and preparing spinning-grade mesophase pitch according to claim 1, characterized in that, In step (1), the mass ratio of FeBr3 to the initial fraction of coal tar at 300-360℃ is 1 to 5:

100.

4. The method for synthesizing and preparing spinning-grade mesophase pitch according to claim 1, characterized in that, The stirring reaction time in step (1) is 2 to 3 hours.

5. The method for synthesizing and preparing spinning-grade mesophase pitch according to claim 1, characterized in that, The filtration in step (2) uses qualitative filter paper.

6. The method for synthesizing and preparing spinning-grade mesophase pitch according to claim 1, characterized in that, The reaction temperature of the thermal polycondensation reaction in step (3) is 390-425°C, the reaction pressure is atmospheric pressure, and the reaction time is 2-4 hours.

7. The method for synthesizing and preparing spinning-grade mesophase pitch according to claim 1, characterized in that, In step (4), the temperature for decompression polymerization is 390-420℃, the time for decompression polymerization is 10-30 minutes, and the pressure for decompression polymerization is -0.1 to -0.05 MPa.

8. A spinning-grade mesophase pitch synthesized and prepared by the method according to any one of claims 1-7, characterized in that, The softening point of the spinning-grade mesophase pitch is 290-315℃; ash content <50ppm; mesophase content 90-100%; suitable spinning viscosity temperature range <380℃.

9. The application of the spinning-grade mesophase pitch synthesized by the method of any one of claims 1-7 or the spinning-grade mesophase pitch of claim 8 in high thermal conductivity carbon fibers.

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