Spinnable mesophase pitch for producing carbon fibers and preparation method thereof

Abstract

The invention relates to the technical field of mesophase pitch preparation, in particular to spinnable mesophase pitch for producing carbon fibers and a preparation method thereof.The spinnable mesophase pitch is obtained through the following steps that aromatic hydrocarbon-rich raw material oil and an extraction solvent are extracted according to the proportion, and then extracted oil and raffinate oil are obtained after standing sedimentation and separation; the preparation method comprises the following steps: filtering raffinate oil, carrying out atmospheric and vacuum distillation to obtain heavy raffinate oil, carrying out mild thermal cracking reaction on the heavy raffinate oil to obtain cracked raffinate oil, heating and distilling the raffinate oil to obtain refined raffinate oil, and finally mixing the refined raffinate oil and the cracked raffinate oil according to a ratio and carrying out thermal polycondensation reaction. According to the invention, the structure, composition and molecular weight distribution of the raw material oil are regulated and controlled by adjusting the ratio of the refined extract oil to the cracking raffinate oil, and the mesophase pitch with low softening point, high mesophase content, high H / C molar ratio and good spinnability is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of mesophase pitch preparation, in particular to a spinnable mesophase pitch for producing carbon fiber and a preparation method thereof. Background Art

[0002] Mesophase pitch-based carbon fiber belongs to high-performance asphalt-based carbon fiber. It is made of mesophase pitch as raw material through melt spinning, pre-oxidation, carbonization and graphitization. Its production technology is difficult. As a high-end product of structural materials or functional materials, it is known as "black gold". Due to its high strength, low thermal expansion coefficient, good impact resistance, high temperature resistance, corrosion resistance, high thermal conductivity and other advantages, it is widely used in defense industries such as aerospace and civilian fields such as medical electronics.

[0003] Mesophase pitch refers to pitch containing mesophase structure, but only spinnable mesophase pitch can prepare high-performance mesophase pitch-based carbon fiber. Therefore, the quality requirements for spinnable mesophase pitch are higher. Specifically, first of all, it is required to achieve a high mesophase content, usually more than 90%, or even 100%. High mesophase content is the guarantee that the system can obtain a high degree of orientation. High mesophase content means that the condensed aromatic hydrocarbon molecules need to reach a certain molecular weight level, but it is necessary to prevent the molecular weight from being too large and causing loss of spinnability; secondly, the mesophase must have a good morphology, which is reflected in the test results. It is required to be a wide-area streamlined shape under the hot stage polarizing microscope. Such a mesophase reflects that the system has good fluidity and a relatively narrow molecular weight distribution; thirdly, the softening point is usually required to reach 230℃ to 280℃. If the softening point is too high, the difficulty of spinning will increase. When the spinning temperature exceeds 380℃, the system is prone to decomposition, affecting the product quality; if the softening point is too low, although spinning is easy, it will cause difficulties for subsequent pre-oxidation, and the oriented structure formed is relatively easy to be destroyed. Finally, the heteroatom and ash content should be low. Ash content will cause difficulties in spinning the system, and the strength and thermal conductivity of the obtained carbon fiber will deteriorate. Heteroatoms such as sulfur will escape during fiber graphitization and cause defects, which will also affect product performance.

[0004] Research has found that in order to obtain high-quality spinnable mesophase asphalt, the composition and structure of the appropriate raw material oil are very critical. It is generally believed that raw materials rich in 3 to 5-ring aromatics are more conducive to obtaining excellent mesophase structures, but they cannot be used as a criterion for determining high-quality raw materials. They are also related to the composition of other structures in the raw materials and the structure of substituents on the aromatic rings, as well as factors such as ash content and heteroatom content in the raw materials. The presence of saturated components in the raw materials is not conducive to the formation of an ordered structure of the mesophase. During thermal cracking, they capture active hydrogen from colloids and asphaltene, promote coke formation, and are not conducive to the formation of an ordered structure of the mesophase. The size of the aromatic molecules in the raw materials and the planarity of the aromatics during the formation process affect the internal structure and physicochemical properties of the mesophase. The planar structure of the aromatic molecules is related to the number of substituents. With the increase of side chain substituents, the non-planar type will be higher, resulting in an increased difficulty in the formation of macromolecular aromatic planar sheets and an increase in the isotropic structure in the product. The light components with a certain aromaticity and the light components of cycloalkanes in the raw materials can serve as effective solvents and hydrogen donors, limiting the excessive condensation of macromolecules and enabling the reaction to obtain planar aromatic molecules with a moderate relative molecular weight. The activity of the reaction system is maintained within a certain range, allowing the mesophase globules to grow evenly, which is conducive to the formation of a uniform, wide-area structured mesophase.

[0005] The Chinese patent document with publication number CN110776943A discloses a method for preparing a spinnable mesophase pitch, which specifically comprises the following steps: crushing a high softening point petroleum pitch, performing heat extraction, filtering, and obtaining a purified petroleum pitch; mixing the purified petroleum pitch with octahydrophenanthrene or a hydrogen-donating agent containing octahydrophenanthrene, and then performing a thermal polycondensation reaction; after the thermal polycondensation reaction is completed, the pressure is reduced, and the mixture is stirred and purged at 370°C to 420°C to obtain the mesophase pitch. However, the mass content of octahydrophenanthrene used in this method is greater than 50%, resulting in a high preparation cost, which limits its promotion and application.

[0006] Patent CN108795467A provides a method for preparing mesophase asphalt by extracting and separating FCC clarified oil and thermal polycondensing. This method uses the fraction with a boiling point below 540°C in cycloalkyl FCC clarified oil as raw material, selects n-pentane as extractant to extract the raw material, and obtains the extractant-insoluble component to prepare mesophase asphalt. This method removes the heavy components with higher molecular weight and the light components with lower molecular weight in the crude oil, and the molecular weight distribution of the crude oil is concentrated. However, this patent only uses a single process to regulate the properties of the crude oil, and it is difficult to take into account some other properties of the crude oil, such as the content of S and N heteroatoms and the removal of catalyst solid powder.

[0007] Publication number CN111019700A discloses a method for preparing a high-quality mesophase asphalt precursor, specifically, extracting coal tar with a mixture of petroleum ether and acetone to obtain an organic solvent mixture, then filtering the mixture under reduced pressure, and then distilling under reduced pressure, taking a fraction within the range of 280°C to 320°C, and obtaining a mesophase asphalt precursor mainly containing four-ring and five-ring aromatic hydrocarbons. This method also has a relatively simple pretreatment process, no step of removing heteroatoms (S, N, etc.), and the saturation rate of aromatics and olefins is not controlled. Due to the complex structure and composition of heavy oil, the efficiency of hydroprocessing under catalyst-free conditions is low, it is difficult to effectively remove sulfur and nitrogen heteroatoms in the raw oil, and at the same time, the aromatic part will undergo hydrogenation saturation reaction, reducing the aromaticity of the raw oil, and it is difficult to obtain a suitable spinnable mesophase asphalt as a raw material.

[0008] The raw oils rich in aromatic components such as petroleum asphalt and coal tar pitch for preparing mesophase asphalt often have a wide molecular weight distribution range and high asphaltene and heteroatom contents. The raw materials need to be refined before the reaction. Solvent extraction refining is a commonly used and effective method for enriching aromatics. However, for high-quality cycloalkane-rich aromatic raw oils, solvent extraction refining enriches aromatics while leaving cycloalkanes in the raw materials in the raffinate, destroying the hydrogen supply advantage of cycloalkanes in the raw materials. Therefore, the existing traditional single treatment process is difficult to meet the requirements. Summary of the invention

[0009] The present invention provides a spinnable mesophase pitch for producing carbon fiber and a preparation method thereof, which overcomes the deficiencies of the above-mentioned prior art. The spinnable mesophase pitch for producing carbon fiber prepared therefrom has the characteristics of low softening point and high mesophase content.

[0010] The technical solution of the present invention is achieved by the following measures: a spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, stirring and extracting the aromatics-rich feedstock oil and the extraction solvent in proportion, and then obtaining extraction oil and raffinate oil after static sedimentation and separation; S2, filtering the raffinate oil in a heated state to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain heavy raffinate oil; S3, placing the heavy raffinate oil in a nitrogen atmosphere, and then subjecting the heavy raffinate oil to a mild thermal cracking reaction to obtain a pyrolysis oil, and then subjecting the pyrolysis oil to atmospheric and vacuum distillation to obtain a pyrolysis raffinate oil; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil; S5, mixing the refined extract oil and the cracking raffinate oil in proportion as co-carbonization feedstock oil, placing the co-carbonization feedstock oil in a nitrogen atmosphere, and then subjecting the co-carbonization feedstock oil to a thermal polycondensation reaction to obtain a spinnable mesophase pitch for producing carbon fiber.

[0011] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The aromatics-rich feedstock oil is one or more of cycloalkyl catalytic cracking slurry, cycloalkyl catalytic cracking cycle oil, cycloalkyl coker wax oil and cycloalkyl vacuum distillate oil.

[0012] The extraction solvent is one or more of furfural, N,N-dimethylformamide and N-methylpyrrolidone.

[0013] In the above step S1, the weight ratio of the aromatics-rich feedstock oil to the extraction solvent is 1:(1 to 4).

[0014] In the above step S5, the weight ratio of the refined extract oil to the cracking raffinate oil is 10:(1 to 3).

[0015] In the above step S1, the extraction temperature is 55°C to 65°C, the extraction time is 30min to 40min, and the static sedimentation time is 30min to 40min.

[0016] In the above step S2, the heating temperature is 80°C to 150°C, and a ceramic membrane with a pore size of 20nm to 150nm is used as a filter membrane for filtration.

[0017] In the above step S3, during the mild thermal cracking reaction, the reaction temperature is 390° C. to 420° C., the reaction pressure is 0.1 MPa to 1.0 MPa, and the reaction time is 10 min to 30 min.

[0018] In the above step S5, during the thermal polycondensation reaction, the reaction temperature is 400° C. to 450° C., the reaction pressure is 0.1 MPa to 4.0 MPa, and the reaction time is 4 h to 10 h.

[0019] The initial distillation point of the heavy raffinate oil is greater than 400°C, the ash content is 0μg / g to 10μg / g, the initial distillation point of the cracking raffinate oil is greater than 400°C, and the cycloalkane content is 70% to 80%.

[0020] The above-mentioned refined extraction oil has an aromatic content of 50% to 80% and an ash content of 0μg / g to 5μg / g.

[0021] The softening point of the spinnable mesophase pitch is 230° C. to 280° C., the mesophase content is 92.0% to 99.7%, and the H / C molar ratio is 0.57 to 0.68.

[0022] The technical solution of the present invention is achieved by the following measures: a spinnable mesophase pitch for producing carbon fiber is carried out according to the following method: S1, stirring and extracting the aromatics-rich feedstock oil and the extraction solvent in proportion, and then obtaining extraction oil and raffinate oil after static sedimentation and separation; S2, filtering the raffinate oil in a heated state to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain heavy raffinate oil; S3, placing the heavy raffinate oil in a nitrogen atmosphere, and then subjecting the heavy raffinate oil to a mild thermal cracking reaction to obtain a pyrolysis oil, and then subjecting the pyrolysis oil to atmospheric and vacuum distillation to obtain a pyrolysis raffinate oil; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil; S5, mixing the refined extract oil and the cracking raffinate oil in proportion as co-carbonization feedstock oil, placing the co-carbonization feedstock oil in a nitrogen atmosphere, and then subjecting the co-carbonization feedstock oil to a thermal polycondensation reaction to obtain a spinnable mesophase pitch for producing carbon fiber.

[0023] The invention is used to produce a spinnable mesophase pitch for carbon fiber. The structure, composition and molecular weight distribution of the raw oil are regulated by adjusting the ratio of refined extraction oil to cracking raffinate oil, so as to prepare a mesophase pitch with a low softening point, a high mesophase content, a high H / C molar ratio and good spinnability. The process flow is simple, the preparation cost is low, the raw material adaptability is strong, the hydrocarbon composition of the aromatics-rich raw oil can be flexibly regulated, and the industrialization can be easily promoted. DETAILED DESCRIPTION

[0024] The present invention is not limited by the following embodiments, and specific implementation methods can be determined according to the technical scheme of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art; the percentages in the present invention are all mass percentages unless otherwise specified.

[0025] The present invention will be further described below in conjunction with embodiments: Example 1: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, stirring and extracting the aromatics-rich feedstock oil and the extraction solvent in proportion, and then standing, settling and separating to obtain an extraction oil and a raffinate oil; S2, filtering the raffinate oil in a heated state to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain heavy raffinate oil; S3, placing the heavy raffinate oil in a nitrogen atmosphere, and then subjecting the heavy raffinate oil to a mild thermal cracking reaction to obtain a pyrolysis oil, and then subjecting the pyrolysis oil to atmospheric and vacuum distillation to obtain a pyrolysis raffinate oil; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil; S5, mixing the refined extract oil and the cracking raffinate oil in proportion as co-carbonization feedstock oil, placing the co-carbonization feedstock oil in a nitrogen atmosphere, and then subjecting the co-carbonization feedstock oil to a thermal polycondensation reaction to obtain a spinnable mesophase pitch for producing carbon fiber.

[0026] Example 2: As an optimization of the above example, the aromatics-rich feedstock oil is one or more of cycloalkyl catalytic cracking slurry oil, cycloalkyl catalytic cracking cycle oil, cycloalkyl coker wax oil and cycloalkyl vacuum distillate oil.

[0027] Example 3: As an optimization of the above example, the extraction solvent is one or more of furfural, N,N-dimethylformamide and N-methylpyrrolidone.

[0028] Example 4: As an optimization of the above example, in step S1, the weight ratio of the aromatics-rich feedstock oil to the extraction solvent is 1:(1 to 4).

[0029] Example 5: As an optimization of the above example, in step S5, the weight ratio of the refined extract oil to the cracking raffinate oil is 10:(1 to 3).

[0030] Example 6: As an optimization of the above example, in step S1, the extraction temperature is 55°C to 65°C, the extraction time is 30min to 40min, and the standing sedimentation time is 30min to 40min.

[0031] Example 7: As an optimization of the above example, in step S2, the heating temperature is 80°C to 150°C, and a ceramic membrane with a pore size of 20nm to 150nm is used as a filter membrane for filtration.

[0032] Example 8: As an optimization of the above example, in step S3, during the mild thermal cracking reaction, the reaction temperature is 390°C to 420°C, the reaction pressure is 0.1MPa to 1.0MPa, and the reaction time is 10min to 30min.

[0033] Example 9: As an optimization of the above example, in step S5, during the thermal polycondensation reaction, the reaction temperature is 400°C to 450°C, the reaction pressure is 0.1MPa to 4.0MPa, and the reaction time is 4h to 10h.

[0034] Example 10: As an optimization of the above example, the initial distillation point of the heavy raffinate is greater than 400°C, the ash content is 0 μg / g to 10 μg / g, the initial distillation point of the cracking raffinate is greater than 400°C, and the cycloalkane content is 70% to 80%.

[0035] Example 11: As an optimization of the above example, the aromatic content of the refined extraction oil is 50% to 80%, and the ash content is 0 μg / g to 5 μg / g.

[0036] Example 12: As an optimization of the above example, the softening point of the spinnable mesophase pitch is 230°C to 280°C, the mesophase content is 92.0% to 99.7%, and the H / C molar ratio is 0.57 to 0.68.

[0037] In step S1 of the present invention, the extraction solvent has a strong solubility for heavy aromatic hydrocarbons with multiple rings and short side chains, and a weak solubility for hydrocarbons with few rings and long side chains. Therefore, the enrichment of aromatic hydrocarbons is achieved in the extracted oil, while the alkanes and cycloalkanes with long side chains are concentrated in the raffinate oil. At the same time, during the solvent extraction and refining process, the powder impurities in the raw oil are enriched in the raffinate oil. Due to its low viscosity, it is easy to remove by filtering in a heated state.

[0038] In steps S2 and S3 of the present invention, the light components in the raffinate oil are evaporated to obtain heavy raffinate oil, and then the long side chains of the heavy raffinate oil are removed by a mild thermal cracking process to obtain cracked raffinate oil. The cracked raffinate oil is enriched with cycloalkane components in the raffinate oil. Since the cycloalkane with short side chains can be used as a more effective solvent and hydrogen donor, the short alkyl side chains can continuously and stably release small molecular free radicals, regulate the reaction of large molecular free radicals, limit the excessive condensation of large molecules during the formation of the intermediate phase, which is beneficial to the growth of the intermediate phase and significantly improves the uniformity of the microstructure of the intermediate phase asphalt.

[0039] The present invention enriches cycloalkanes and performs mild thermal cracking to remove long side chains to obtain cracking raffinate oil, which is then blended into refined extraction oil to provide a more effective hydrogen donor for the mesophase asphalt reaction, thereby achieving deep and precise control of the structure, group composition and molecular weight distribution of the feedstock oil, which is beneficial to the preparation of excellent spinnable mesophase asphalt for the production of carbon fibers.

[0040] Compared with the prior art, the present invention has the following beneficial effects: First, the invention is used to produce the spinnable mesophase pitch of carbon fiber. No solid catalyst is used in the whole process, no other solid impurities are introduced, the ash content is low, and no liquid or gas catalyst with strong corrosiveness is introduced. The process is relatively easy to industrialize. Secondly, the spinnable mesophase pitch for producing carbon fiber of the present invention, in view of the characteristics of aromatic-rich feedstock oil (cycloalkyl aromatic-rich fraction oil), separates the fractions of the raffinate oil, and removes the long side chains of the heavy raffinate oil through a mild thermal cracking process, thereby effectively enriching the cycloalkane components in the raffinate oil. The cycloalkane components are effectively utilized, providing a more effective hydrogen donor for the mesophase pitch reaction; Thirdly, the present invention is used to produce a spinnable mesophase pitch for carbon fiber. By adjusting the ratio of refined extract oil to cracked raffinate oil, the structure, composition and molecular weight distribution of the aromatic-rich feedstock oil can be regulated to prepare a mesophase pitch having a softening point of 230° C. to 280° C., a mesophase content of 92.0% to 99.7%, a high H / C molar ratio and good spinnability. Finally, the present invention is used to produce the spinnable mesophase asphalt of carbon fiber, the process flow is simple, the resource advantage of aromatic-rich feedstock oil is fully utilized, the preparation cost is low, the raw material adaptability is strong, the hydrocarbon composition of aromatic-rich feedstock oil can be flexibly controlled, and it is easy to promote and realize industrialization.

[0041] Embodiment 13: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, extracting cycloalkyl catalytic cracking cycle oil and furfural in a weight ratio of 1:1 at 60° C. for 30 minutes by stirring, and then standing and settling for 30 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 80°C using a ceramic membrane with a pore size of 20 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 0 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.5 MPa, and performing a mild thermal cracking reaction at a temperature of 390° C. for 30 min, during which gas is produced, the pressure in the reactor is controlled to be stable, and after the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain a cracking raffinate oil having an initial boiling point greater than 400° C. and a cycloalkane content of 76%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 78% and an ash content of 0 μg / g; S5, the refined extraction oil and the cracking residual oil in a weight ratio of 10:1 are mixed as the co-carbonization feedstock oil, the co-carbonization feedstock oil is added into the reactor, the air is replaced by nitrogen for 3 times, nitrogen is introduced into the reactor to increase the pressure to 4.0MPa, and after the thermal polycondensation reaction is carried out at a temperature of 420°C for 6 hours, gas is produced during the reaction process, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 270°C, an mesophase content of 98.7%, and an H / C molar ratio of 0.62.

[0042] Embodiment 14: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, stirring and extracting cycloalkyl catalytic cracking oil slurry and furfural in a weight ratio of 1:2 at 65° C. for 35 minutes, and then standing and settling for 35 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 150°C using a ceramic membrane with a pore size of 50 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 10 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.1 MPa, and performing a mild thermal cracking reaction at a temperature of 420° C. for 10 min. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain a cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 80%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 76% and an ash content of 5 μg / g; S5, mixing the refined extract oil and the cracking raffinate oil in a weight ratio of 10:2 as the co-carbonization feedstock oil, adding the co-carbonization feedstock oil into the reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 3MPa, and subjecting the reactor to a thermal polycondensation reaction at a temperature of 410°C for 10 hours. Gas is produced during the reaction, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 260°C, an mesophase content of 99.7%, and an H / C molar ratio of 0.68.

[0043] Embodiment 15: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, extracting cycloalkyl coker wax oil and furfural in a weight ratio of 1:1 at 55° C. by stirring for 30 minutes, and then standing and settling for 30 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 100°C using a ceramic membrane with a pore size of 100 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 0 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 1.0 MPa, and performing a mild thermal cracking reaction at a temperature of 400° C. for 20 min. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 73%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 55% and an ash content of 0 μg / g; S5, the refined extraction oil and the cracking residual oil are mixed in a weight ratio of 10:2 as the co-carbonization feedstock oil, the co-carbonization feedstock oil is added into the reactor, the air is replaced by nitrogen for 3 times, nitrogen is introduced into the reactor to increase the pressure to 0.1MPa, and after the thermal polycondensation reaction is carried out at a temperature of 440°C for 10 hours, gas is produced during the reaction process, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 280°C, an mesophase content of 92.0%, and an H / C molar ratio of 0.57.

[0044] Embodiment 16: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, stirring and extracting cycloalkyl catalytic cracking oil slurry and furfural in a weight ratio of 1:1 at 60° C. for 40 minutes, and then standing and settling for 40 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 80°C using a ceramic membrane with a pore size of 150 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 5 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.5 MPa, and performing a mild thermal cracking reaction at a temperature of 400° C. for 20 min. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 70%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 80% and an ash content of 0 μg / g; S5, mixing the refined extract oil and the cracking raffinate oil in a weight ratio of 10:2 as the co-carbonization feedstock oil, adding the co-carbonization feedstock oil into the reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 3MPa, and subjecting the reactor to a thermal polycondensation reaction at a temperature of 400°C for 10 hours. Gas is produced during the reaction, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 255°C, an mesophase content of 98.7%, and an H / C molar ratio of 0.62.

[0045] Embodiment 17: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, stirring and extracting cycloalkyl catalytic cracking oil slurry and furfural in a weight ratio of 1:1 at 60° C. for 40 minutes, and then standing and settling for 40 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 150°C using a ceramic membrane with a pore size of 80 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 5 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.5 MPa, and performing a mild thermal cracking reaction at a temperature of 400° C. for 20 min. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain a cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 73%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 80% and an ash content of 0 μg / g; S5, mixing the refined extract oil and the cracking raffinate oil in a weight ratio of 10:3 as the co-carbonization feedstock oil, adding the co-carbonization feedstock oil into the reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 2MPa, and subjecting the reactor to a thermal polycondensation reaction at a temperature of 400°C for 10 hours. Gas is produced during the reaction, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 235°C, an mesophase content of 99.5%, and an H / C molar ratio of 0.66.

[0046] Embodiment 18: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, extracting cycloalkyl catalytic cracking cycle oil and furfural in a weight ratio of 1:1 at 60° C. for 30 minutes by stirring, and then standing and settling for 30 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 100°C using a ceramic membrane with a pore size of 20 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 0 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.5 MPa, and performing a mild thermal cracking reaction at a temperature of 400° C. for 20 minutes. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain a cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 75%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 78% and an ash content of 0 μg / g; S5, mixing the refined extraction oil and the cracking raffinate oil in a weight ratio of 10:2 as the co-carbonization feedstock oil, adding the co-carbonization feedstock oil into the reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 4MPa, and subjecting the reactor to a thermal polycondensation reaction at a temperature of 420°C for 6 hours. Gas is produced during the reaction, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 260°C, an mesophase content of 98.9%, and an H / C molar ratio of 0.64.

[0047] Embodiment 19: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, extracting cycloalkyl catalytic cracking cycle oil and furfural in a weight ratio of 1:4 at 60° C. by stirring for 30 minutes, and then standing and settling for 30 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 100°C using a ceramic membrane with a pore size of 20 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 0 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.5 MPa, and performing a mild thermal cracking reaction at a temperature of 400° C. for 20 minutes. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain a cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 71%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 74% and an ash content of 5 μg / g; S5, mixing the refined extraction oil and the cracking residual oil in a weight ratio of 10:3 as the co-carbonization feedstock oil, adding the co-carbonization feedstock oil into the reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 1MPa, and subjecting the reactor to a thermal polycondensation reaction at a temperature of 440°C for 4 hours. Gas is produced during the reaction, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 230°C, an mesophase content of 97.5%, and an H / C molar ratio of 0.67.

[0048] Embodiment 20: The spinnable mesophase pitch for producing carbon fiber is obtained by the following method: S1, extracting cycloalkyl minus four fraction oil and furfural in a weight ratio of 1:1 at 55° C. for 30 minutes by stirring, and then standing and settling for 30 minutes to separate extract oil and raffinate oil; S2, filtering the raffinate oil at 80°C using a ceramic membrane with a pore size of 150 nm to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain a heavy raffinate oil with an initial distillation point greater than 400°C and an ash content of 0 μg / g; S3, adding the heavy raffinate oil to a reactor, replacing the air with nitrogen for 3 times, introducing nitrogen into the reactor to increase the pressure to 0.5 MPa, and performing a mild thermal cracking reaction at a temperature of 400° C. for 20 min. During the reaction, gas is produced, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain cracking oil, and then the cracking oil is subjected to atmospheric and vacuum distillation to obtain cracking raffinate oil with an initial boiling point greater than 400° C. and a cycloalkane content of 74%; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil with an aromatic content of 50% and an ash content of 0 μg / g; S5, a mixture of refined extract oil and cracking raffinate oil in a weight ratio of 10:1 is used as a co-carbonization feedstock oil, the co-carbonization feedstock oil is added into a reactor, the air is replaced by nitrogen three times, nitrogen is introduced into the reactor to increase the pressure to 2MPa, and a thermal polycondensation reaction is carried out at a temperature of 400°C for 7 hours. Gas is produced during the reaction, and the pressure in the reactor is controlled to be stable. After the reaction is completed, the pressure is released and the temperature is slowly lowered to obtain a spinnable mesophase asphalt for the production of carbon fiber with a softening point of 245°C, an mesophase content of 93.8%, and an H / C molar ratio of 0.59.

[0049] The spinnable mesophase pitch for producing carbon fiber prepared in Examples 13 to 20 of the present invention has excellent performance, a softening point of 230°C to 280°C, an mesophase content of 92.0% to 99.7%, and a high H / C molar ratio.

[0050] In summary, the present invention is used to produce a spinnable mesophase asphalt for carbon fiber. By adjusting the ratio of refined extraction oil to cracking raffinate oil, the structure, composition and molecular weight distribution of the raw oil are regulated to prepare an mesophase asphalt with a low softening point, a high mesophase content, a high H / C molar ratio and good spinnability. The process flow is simple, the preparation cost is low, the raw material adaptability is strong, the hydrocarbon composition of the aromatic-rich raw oil can be flexibly regulated, and the process is easy to promote and realize industrialization.

[0051] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A spinnable mesophase pitch for producing carbon fiber, characterized in that Obtained as follows: S1, stirring and extracting the aromatics-rich feedstock oil and the extraction solvent in proportion, and then standing, settling and separating to obtain an extraction oil and a raffinate oil; S2, filtering the raffinate oil in a heated state to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain heavy raffinate oil; S3, placing the heavy raffinate oil in a nitrogen atmosphere, and then subjecting the heavy raffinate oil to a mild thermal cracking reaction to obtain a pyrolysis oil, and then subjecting the pyrolysis oil to atmospheric and vacuum distillation to obtain a pyrolysis raffinate oil; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil; S5, mixing the refined extract oil and the cracking raffinate oil in proportion as co-carbonization feedstock oil, placing the co-carbonization feedstock oil in a nitrogen atmosphere, and then subjecting the co-carbonization feedstock oil to a thermal polycondensation reaction to obtain a spinnable mesophase pitch for producing carbon fiber.

2. The spinnable mesophase pitch for producing carbon fiber according to claim 1, characterized in that The aromatics-rich feedstock oil is one or more of cycloalkyl catalytic cracking oil slurry, cycloalkyl catalytic cracking cycle oil, cycloalkyl coker wax oil and cycloalkyl vacuum distillate oil; or / and, the extraction solvent is one or more of furfural, N,N-dimethylformamide and N-methylpyrrolidone.

3. The spinnable mesophase pitch for producing carbon fiber according to claim 1 or 2, characterized in that In step S1, the weight ratio of the aromatics-rich feedstock oil to the extraction solvent is 1:1 to 4; or / and, in step S5, the weight ratio of the refined extraction oil to the cracking raffinate oil is 10:1 to 3.

4. The spinnable mesophase pitch for producing carbon fiber according to claim 1, 2 or 3, characterized in that In step S1, the extraction temperature is 55°C to 65°C, the extraction time is 30min to 40min, and the static sedimentation time is 30min to 40min.

5. The spinnable mesophase pitch for producing carbon fiber according to any one of claims 1 to 4, characterized in that In step S2, the heating temperature is 80°C to 150°C, and a ceramic membrane with a pore size of 20nm to 150nm is used as a filter membrane for filtration.

6. The spinnable mesophase pitch for producing carbon fiber according to any one of claims 1 to 5, characterized in that In step S3, during the mild thermal cracking reaction, the reaction temperature is 390° C. to 420° C., the reaction pressure is 0.1 MPa to 1.0 MPa, and the reaction time is 10 min to 30 min.

7. The spinnable mesophase pitch for producing carbon fibers according to any one of claims 1 to 6, characterized in that In step S5, during the thermal polycondensation reaction, the reaction temperature is 400° C. to 450° C., the reaction pressure is 0.1 MPa to 4.0 MPa, and the reaction time is 4 h to 10 h.

8. The spinnable mesophase pitch for producing carbon fibers according to any one of claims 1 to 7, characterized in that The initial distillation point of the heavy raffinate is greater than 400°C, the ash content is 0μg / g to 10μg / g, the initial distillation point of the cracking raffinate is greater than 400°C, and the cycloalkane content is 70% to 80%.

9. The spinnable mesophase pitch for producing carbon fibers according to any one of claims 1 to 8, characterized in that The refined extracted oil has an aromatic content of 50% to 80%, an ash content of 0μg / g to 5μg / g; or / and, the softening point of the spinnable mesophase pitch is 230°C to 280°C, the mesophase content is 92.0% to 99.7%, and the H / C molar ratio is 0.57 to 0.

68.

10. A method for preparing a spinnable mesophase pitch for producing carbon fiber according to claims 2 to 9, characterized in that Proceed as follows: S1, stirring and extracting the aromatics-rich feedstock oil and the extraction solvent in proportion, and then standing, settling and separating to obtain an extraction oil and a raffinate oil; S2, filtering the raffinate oil in a heated state to remove impurities, and then subjecting the extracted oil after the impurities are removed to atmospheric and vacuum distillation to remove a small amount of extraction solvent and light components to obtain heavy raffinate oil; S3, placing the heavy raffinate oil in a nitrogen atmosphere, and then subjecting the heavy raffinate oil to a mild thermal cracking reaction to obtain a pyrolysis oil, and then subjecting the pyrolysis oil to atmospheric and vacuum distillation to obtain a pyrolysis raffinate oil; S4, heating and distilling the extracted oil, recovering the extraction solvent, and obtaining a refined extracted oil; S5, mixing the refined extract oil and the cracking raffinate oil in proportion as co-carbonization feedstock oil, placing the co-carbonization feedstock oil in a nitrogen atmosphere, and then subjecting the co-carbonization feedstock oil to a thermal polycondensation reaction to obtain a spinnable mesophase pitch for producing carbon fiber.