Method for preparing spinnable mesophase pitch through catalytic hydrogenation modification of coal pitch suspended bed

Abstract

A method for preparing spinnable mesophase pitch through catalytic hydrogenation modification of coal pitch in a suspended bed comprises the following steps: uniformly mixing raw materials with a solvent, adding a catalyst, and carrying out heat treatment under initial hydrogen pressure to obtain a hydrogenated product; carrying out reduced pressure distillation on the hydrogenated product to remove the solvent; carrying out primary extraction on the reduced pressure distillation product, and separating large particles of the catalyst to obtain an aromatic solvent soluble substance; extracting and centrifugally separating the fine catalyst particles again to obtain a heavy oil solvent mixture; and carrying out reduced pressure distillation again to obtain hydrogenated pitch, and carrying out thermal polycondensation and enrichment to obtain the spinnable mesophase pitch. A suspended bed catalytic hydrogenation technology is adopted to effectively solve the problem that a catalyst is easy to coke and carbon deposit to block a bed layer; the solvent oil has the effect of dissolving the raw materials and also has the hydrogen supply capacity, and meanwhile, the solvent can be recycled; the technological process is simple, the raw material requirement is low, and the production cost is low; the ash content in the hydrogenated asphalt is effectively removed by the secondary extraction-centrifugation process; the hydrogenated pitch prepared by the method is high in H / C ratio, low in aromaticity and low in heteroatom content, and the mesophase pitch synthesized by taking the hydrogenated pitch as a raw material is high in mesophase content, appropriate in softening point and good in spinnability.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal chemical industry, and relates to a method for catalytic hydrogenation modification of coal tar pitch in a suspension bed to prepare spinnable mesophase pitch. Background Art

[0002] Due to excellent physical and chemical properties such as medium strength, high modulus, and good thermal and electrical conductivity, mesophase pitch-based carbon fibers are widely used in the fields of aerospace, military equipment, and energy storage in China, and are star products for China's strategic development. One of the key preparation technologies for high-performance pitch-based carbon fibers is the synthesis of high-quality spinnable mesophase pitch. One of the key technical problems in the preparation of mesophase pitch-based carbon fibers is the synthesis of the raw material mesophase pitch, and the physical and chemical properties of the raw material pitch are a key factor affecting the properties of the mesophase pitch product and the spinning performance. China is rich in coal resources, and coal tar pitch has a wide source and its molecular structure is easy to regulate, making it an ideal raw material for preparing mesophase pitch. Coal tar pitch has a large molecular weight, a high content of polycyclic aromatic hydrocarbons, and a relatively high content of heteroatom compounds, and is not suitable for directly synthesizing mesophase pitch. Therefore, it is necessary to pretreat coal tar pitch to regulate its molecular structure.

[0003] Patent CN103205271A discloses a method for producing mesophase pitch using high-temperature coal tar as a raw material, including high-temperature coal tar purification, hydrofining, distillation to obtain hydrogenated pitch, and thermal condensation to obtain mesophase pitch. This method uses a fixed-bed reactor for catalytic hydrogenation reaction, and the catalyst is extremely prone to coking and carbon deposition, requiring a large amount of solvent, resulting in low production efficiency and high process costs.

[0004] Patent CN110699107A discloses a method for preparing spinnable mesophase pitch by catalytic hydrogenation-hydrogen supply treatment of coal tar pitch, including high-temperature catalytic hydrogenation to prepare primary hydrogenated pitch, catalytic hydrogenation-hydrogen supply synergistic treatment to prepare secondary hydrogenated pitch, purification treatment to prepare refined hydrogenated pitch, and thermal condensation to obtain mesophase pitch. This method promotes the formation of catalysts from the native inorganic minerals in coal tar pitch under high-temperature hydrogenation conditions for primary hydrogenation treatment, and then uses a hydrogen supply solvent for secondary hydrogenation treatment. The hydrogenation effect is poor, the hydrogen supply solvent cannot be recycled, and the hydrogenation process flow is complex, with high requirements for the content of native inorganic minerals in the raw materials and high production costs.

[0005] Patent CN107603671A discloses a system and method for preparing mesophase pitch and oil products based on the hydrogenation of medium and low temperature coal tar, including coal tar pretreatment, coal tar hydrodemetallization, and thermal condensation of heavy components to prepare mesophase pitch. This method requires the use of a protective catalyst, a demetallization catalyst, and a deasphalting catalyst, with high process costs; and a series of complex demetallization pretreatments are required before hydrogenation. This method has high requirements for raw materials and a complex treatment process. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for preparing hydrogenated asphalt, which is used to solve the problems of excessive aromaticity and high heteroatom content of coal tar pitch, and at the same time solve the problem of easy coking and carbon deposition of the catalyst blocking the bed. In addition, the solvent used in the method of the present invention can be recycled, which can effectively improve the process efficiency and save costs.

[0007] The technical solution of the present invention:

[0008] A method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch in a suspension bed, comprising the following steps:

[0009] Step 1: Uniformly mix coal tar pitch, solvent oil and catalyst in a mass ratio of 1:0.5-2:0.075-0.45, and then feed them into a suspension bed reactor. Under the conditions of a hydrogen pressure of 4-25 MPa, a temperature of 350-400 °C, and a residence time of 0.5-3 h, a hydrogenated product is obtained by reaction;

[0010] Step 2: Remove the solvent oil from the hydrogenated product obtained in Step 1 by vacuum distillation. The vacuum distillation conditions are a vacuum degree of -0.1 MPa and a maximum gas phase temperature of 350 °C to obtain hydrogenated asphalt;

[0011] Step 3: Mix the hydrogenated asphalt obtained after vacuum distillation in Step 2 with an aromatic solvent in a mass ratio of 1:5-20 for extraction, and separate the catalyst particles with a sintered metal filter with a filtration accuracy of 20-100 meshes to obtain an aromatic solvent coarsely separated soluble matter solution;

[0012] Step 4: Remove the aromatic solvent from the aromatic solvent coarsely separated soluble matter solution obtained in Step 3 by atmospheric distillation to obtain coarsely separated hydrogenated asphalt;

[0013] Step 5: Mix the coarsely separated hydrogenated asphalt obtained in Step 4 with a heavy oil solvent in a mass ratio of 1:5-10 for extraction, and use centrifugation to separate the catalyst powder to obtain a heavy oil soluble matter solution;

[0014] Step 6: Vacuum distill the heavy oil soluble matter solution obtained in Step 5 under the conditions of a vacuum degree of -0.1 MPa and a maximum gas phase temperature of 380 °C to remove the solvent and obtain refined hydrogenated asphalt;

[0015] Step 7: Perform thermal polycondensation reaction and mesophase enrichment on the refined hydrogenated asphalt obtained in Step 6 to prepare spinnable mesophase pitch.

[0016] In Step 1, the coal tar pitch is the pitch obtained by distilling high-temperature coal tar at 180-360 °C.

[0017] In Step 1, the solvent oil is selected from aromatic solvents obtained by subjecting high-temperature coal tar to vacuum distillation at a vacuum degree of -0.1 MPa and a gas-phase temperature of 240-350 °C, followed by partial hydrogenation saturation of the distillate oil. Its molecular structure features are partially saturated polycyclic aromatic hydrocarbons with a total ring number of 2-6 rings, where the number of naphthene rings accounts for 20-70% of the total ring number.

[0018] The method for preparing spinnable mesophase pitch by hydro-upgrading of coal tar pitch according to Claim 1 is characterized in that

[0019] In Step 1, the suspended bed catalytic hydrogenation reaction is carried out in the presence of the following hydrofining catalyst. The hydrofining catalyst is: using γ-alumina or silica-alumina as the carrier, with a specific surface area of 120-300 m 2 / g, a pore volume of 0.4-1.4 mL / g, a pore diameter of 8-20 nm, and a surface acid content of 0.05-0.1 mmol / g; the metal active components are Group VIB metals Mo or W and Group VIII metals Co or Ni; calculated based on the total mass of the hydrofining catalyst, the content of Group VIB metals in terms of oxides is 10-20 wt.%, and the content of Group VIII metals in terms of oxides is 1-5 wt.%.

[0020] In Step 3, the aromatic solvent is selected from one or a mixture of two or more of benzene, toluene, xylene, and cyclohexane.

[0021] In Step 5, the heavy oil solvent is selected from coal tar distillate oil and its partially hydrogenated saturated products, and its molecular structure is partially saturated polycyclic aromatic hydrocarbons with a total ring number of 4-7 rings, where the number of naphthene rings is not more than 40% of the total ring number.

[0022] In Step 5, the centrifugal separation is carried out at a rotational speed of 5000-10000 rpm.

[0023] In Step 7, the thermal polycondensation reaction is carried out at a pressure of 0-3.0 MPa (absolute pressure), an atmosphere of nitrogen or argon, a temperature of 380-460 °C, and a stirring speed of 10-60 rpm for 3-24 h.

[0024] In Step 7, the mesophase enrichment includes, but is not limited to, solvent extraction with benzene, toluene, or xylene; purging with nitrogen, hydrogen, or argon gas streams; and thin-film evaporation.

[0025] Advantages of the present invention: First, the present invention uses a suspension bed reactor to catalytically hydrogenate and modify coal tar pitch. The suspension bed reactor can effectively solve the problem of easy coking and carbon deposition of the catalyst through dynamic mixing, efficient mass transfer and heat transfer, utilization of high hydrogen partial pressure, and dynamic update of the catalyst surface. Second, the present invention uses partially hydrogenated saturated distillate oil as a solvent, which not only dissolves the raw coal tar pitch but also has a hydrogen supply capacity. At the same time, the solvent can be recovered and reused by vacuum distillation, with high production efficiency and low cost. Third, the process flow of this process is simple, with low requirements for raw materials and low production costs. Fourth, this process adopts a two-step extraction-centrifugation method to remove and recover large catalyst particles during the first extraction process, introduce heavy oil solvent during the second extraction process to break the colloids with tiny catalyst particles in the pitch, and completely remove the fine catalyst particles generated by mechanical collision during the reaction through mechanical centrifugation, effectively reducing the ash content of the product. Fifth, the hydrogenated pitch prepared under the preferred conditions of the present invention has a high H / C ratio, low aromaticity, and low heteroatom content. The mesophase pitch synthesized from it has a high mesophase content, appropriate softening point, and good spinnability. Description of the Drawings

[0026] Figure 1 It is the infrared spectrogram of the hydrogenated pitch prepared in Example 1.

[0027] Figure 2 It is the polarized light microscope photograph of the hydrogenated pitch prepared in Example 1 after thermal polycondensation into mesophase pitch. Detailed Embodiments

[0028] The following further illustrates the detailed embodiments of the present invention in conjunction with the drawings and technical solutions.

[0029] Example 1

[0030] The coal tar pitch, solvent oil and catalyst are uniformly mixed in a mass ratio of 1:1:0.3 and then fed into a suspension bed reactor. The catalyst uses γ-aluminum oxide as a carrier, the specific surface area of the carrier is 294 m 2 / g, the pore volume is 0.69 mL / g, the pore diameter is 14.69 nm, MoO 3The loading amount is 15.78 wt.%, and the NiO loading amount is 1.36 wt.%. It is heated to 360 °C under a hydrogen pressure of 16 MPa and heat-treated for 1.5 h to obtain the post-hydrogenation product; then the obtained post-hydrogenation product is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas phase temperature reaches 350 °C to remove the solvent, and hydrogenated asphalt is obtained; the hydrogenated asphalt and benzene are dissolved and extracted at a mass ratio of 1:10, and a 30-mesh sintered metal filter is used to filter out catalyst particles to obtain a benzene coarsely separated soluble matter solution; the benzene coarsely separated soluble matter solution is distilled at atmospheric pressure to remove the fractions with a gas phase temperature below 180 °C to obtain coarsely separated hydrogenated asphalt; the coarsely separated hydrogenated asphalt and a heavy oil solvent are mixed and extracted at a mass ratio of 1:5, the centrifuge speed is set at 5000 rpm to centrifugally separate the catalyst powder therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas phase temperature reaches 380 °C to remove the heavy oil solvent, and refined hydrogenated asphalt is obtained, with its H content being 5.73 wt.%, the aromaticity index being 0.51, and the ash content being less than 60 ppm. Under the conditions of this preferred embodiment, the molecular structure of the solvent oil used in the catalytic hydrogenation process is a partially saturated condensed polycyclic aromatic hydrocarbon with 4 rings, and the number of naphthene rings accounts for 45% of the total number of rings; the molecular structure of the heavy oil solvent used in the two-step extraction-centrifugation process is a partially saturated condensed polycyclic aromatic hydrocarbon with 5-7 rings, and the number of naphthene rings accounts for 20-40% of the total number of rings.

[0031] The hydrogenated asphalt is pyrolyzed at 410 °C, 3.0 MPa absolute pressure, and in a nitrogen atmosphere for 3 h to obtain primary pyrolytic asphalt; the primary pyrolytic asphalt and benzene are mixed and extracted to obtain benzene-insoluble matter, and the benzene-insoluble matter is pyrolyzed at 350 °C for 30 min to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 255 °C, a mesophase content of 100 vol.%, and the content of the wide-field optical texture is >96 vol.%.

[0032] Example 2

[0033] The coal tar pitch, solvent oil, and catalyst are uniformly mixed in a mass ratio of 1:0.75:0.085 and then fed into a suspension bed reactor. The catalyst uses γ-aluminum oxide as the carrier, the specific surface area of the carrier is 268 m 2 / g, the pore volume is 0.69 mL / g, the pore diameter is 12.44 nm, MoO 3The loading amount is 13.86 wt.%, and the NiO loading amount is 1.43 wt.%. It is heated to 420 °C under a hydrogen pressure of 8 MPa and heat-treated for 2.75 h to obtain the post-hydrogenation product; then the obtained post-hydrogenation product is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 350 °C to remove the solvent, and hydrogenated pitch is obtained; the hydrogenated pitch is dissolved and extracted with toluene at a mass ratio of 1:13, and a 100-mesh sintered metal filter is used to filter out the catalyst particles to obtain a toluene coarsely separated soluble matter solution; the toluene coarsely separated soluble matter solution is distilled at atmospheric pressure to remove the fractions with a gas-phase temperature below 170 °C to obtain coarsely separated hydrogenated pitch; the coarsely separated hydrogenated pitch is mixed and extracted with a heavy oil solvent at a mass ratio of 1:8, the centrifuge speed is set at 6000 rpm to centrifugally separate the catalyst powder therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 380 °C to remove the heavy oil solvent, and refined hydrogenated pitch is obtained, with its H content being 5.16 wt.%, the aromaticity index being 0.57, and the ash content being less than 85 ppm.

[0034] The hydrogenated pitch is pyrolyzed at 420 °C, 2.5 MPa absolute pressure, and in a nitrogen atmosphere for 4 h to obtain primary pyrolytic pitch; the primary pyrolytic pitch is subjected to thin-film evaporation to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 270 °C, a mesophase content of 95 vol.%, and a wide-area optical texture content > 93 vol.%.

[0035] Example 3

[0036] Coal tar pitch, solvent oil, and catalyst are uniformly mixed in a mass ratio of 1:0.7:0.095 and then fed into a suspension bed reactor. The catalyst uses silicon-aluminum oxide as the carrier, the specific surface area of the carrier is 277 m 2 / g, the pore volume is 0.58 mL / g, the pore diameter is 14.55 nm, and MoO 3The loading amount is 15.39 wt.%, and the NiO loading amount is 1.28 wt.%. It is heated to 320 °C under a hydrogen pressure of 11 MPa and heat-treated for 1.5 h to obtain the hydrogenated product; then the obtained hydrogenated product is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 350 °C to remove the solvent, and hydrogenated asphalt is obtained; the hydrogenated asphalt is dissolved and extracted with xylene in a mass ratio of 1:12, and a 40-mesh sintered metal filter is used to filter out catalyst particles to obtain a xylene coarsely separated soluble matter solution; the xylene coarsely separated soluble matter solution is distilled at atmospheric pressure to remove the fractions with a gas-phase temperature below 190 °C to obtain coarsely separated hydrogenated asphalt; the coarsely separated hydrogenated asphalt is mixed and extracted with a heavy oil solvent in a mass ratio of 1:10, the centrifuge speed is set at 7000 rpm to centrifugally separate the catalyst powder therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 380 °C. After removing the heavy oil solvent, refined hydrogenated asphalt is obtained, with an H content of 5.08 wt.%, an aromaticity index of 0.58, and an ash content of less than 90 ppm.

[0037] The hydrogenated asphalt is pyrolyzed at 420 °C, 2.0 MPa absolute pressure, and in an argon atmosphere for 5 h. Nitrogen is introduced for purging during the pyrolysis process to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 265 °C, a mesophase content of 90 vol.%, and a wide-area optical texture content > 90 vol.%.

[0038] Example 4

[0039] Coal tar pitch, solvent oil, and catalyst are uniformly mixed in a mass ratio of 1:0.5:0.09 and then fed into a suspension bed reactor. The catalyst uses γ-aluminum oxide as the carrier, the specific surface area of the carrier is 271 m 2 / g, the pore volume is 0.84 mL / g, the pore diameter is 12.63 nm, MoO 3The loading amount is 12.96 wt.%, and the NiO loading amount is 1.59 wt.%. It is heated to 375 °C under a hydrogen pressure of 14 MPa and heat-treated for 1.5 h to obtain the post-hydrogenation product; then the obtained post-hydrogenation product is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 350 °C to remove the solvent, and hydrogenated pitch is obtained; the hydrogenated pitch is dissolved and extracted with toluene at a mass ratio of 1:16, and a 50-mesh sintered metal filter is used to filter out catalyst particles to obtain a toluene roughly separated soluble matter solution; the toluene roughly separated soluble matter solution is distilled at atmospheric pressure to remove fractions with a gas-phase temperature below 175 °C to obtain roughly separated hydrogenated pitch; the roughly separated hydrogenated pitch is mixed and extracted with a heavy oil solvent at a mass ratio of 1:8, the centrifuge speed is set at 8000 rpm to centrifugally separate the catalyst powder therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 380 °C to remove the heavy oil solvent, and refined hydrogenated pitch is obtained, with its H content being 5.21 wt.%, the aromaticity index being 0.53, and the ash content being less than 100 ppm.

[0040] The hydrogenated pitch is pyrolyzed at 440 °C, 1.5 MPa absolute pressure, and in a nitrogen atmosphere for 14 h, and argon is introduced for purging during the pyrolysis process to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 291 °C, a mesophase content of 94 vol.%, and a wide-field optical texture content > 91 vol.%.

[0041] Example 5

[0042] Coal tar pitch, solvent oil, and catalyst are uniformly mixed in a mass ratio of 1:1:0.1 and then fed into a suspension bed reactor. The catalyst uses γ-aluminum oxide as the carrier, the specific surface area of the carrier is 201 m 2 / g, the pore volume is 0.79 mL / g, the pore diameter is 15.96 nm, MoO 3The loading amount is 16.89 wt.%, and the NiO loading amount is 1.37 wt.%. It is heated to 390 °C under an initial hydrogen pressure of 15 MPa and heat-treated for 2.5 h to obtain the post-hydrogenation product; then the obtained post-hydrogenation product is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 350 °C to remove the solvent, and hydrogenated pitch is obtained; the hydrogenated pitch is dissolved and extracted with toluene at a mass ratio of 1:20, and a 100-mesh sintered metal filter is used to filter out the catalyst particles to obtain a toluene crudely separated soluble matter solution; the toluene crudely separated soluble matter solution is distilled at atmospheric pressure to remove the fractions with a gas-phase temperature below 190 °C to obtain crudely separated hydrogenated pitch; the crudely separated hydrogenated pitch is mixed and extracted with a heavy oil solvent at a mass ratio of 1:9, the centrifuge speed is set at 8000 rpm to centrifugally separate the catalyst powder therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas-phase temperature reaches 380 °C to remove the heavy oil solvent, and refined hydrogenated pitch is obtained, with its H content being 5.15 wt.%, the aromaticity index being 0.52, and the ash content being less than 85 ppm.

[0043] The hydrogenated pitch is pyrolyzed at 450 °C, 1.5 MPa absolute pressure, and in an argon atmosphere for 5 h to obtain primary pyrolytic pitch; the primary pyrolytic pitch is extracted with xylene to obtain xylene-insoluble matter, and the xylene-insoluble matter is pyrolyzed at 350 °C for 30 min to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 283 °C, a mesophase content of 94 vol.%, and a wide-area optical texture content > 92 vol.%.

[0044] Example 6

[0045] Coal tar pitch, solvent oil, and catalyst are uniformly mixed in a mass ratio of 1:2:0.3 and then fed into a suspension bed reactor. The catalyst uses γ-aluminum oxide as the carrier, the specific surface area of the carrier is 274 m 2 / g, the pore volume is 1.1 mL / g, the pore diameter is 13.97 nm, MoO 3The loading amount is 20 wt.%, and the NiO loading amount is 1 wt.%. It is heated to 400 °C under a hydrogen pressure of 20 MPa and heat-treated for 1 h to obtain the post-hydrogenation product; then the obtained post-hydrogenation product is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas phase temperature reaches 350 °C to remove the solvent, and hydrogenated pitch is obtained; the hydrogenated pitch is dissolved and extracted with toluene at a mass ratio of 1:10, and a 80-mesh sintered metal filter is used to filter out the catalyst particles to obtain the toluene coarsely separated soluble matter solution; the toluene coarsely separated soluble matter solution is distilled at atmospheric pressure to remove the fractions with a gas phase temperature below 195 °C to obtain the coarsely separated hydrogenated pitch; the coarsely separated hydrogenated pitch is mixed and extracted with a heavy oil solvent at a mass ratio of 1:10, the centrifuge speed is set at 10,000 rpm to centrifugally separate the catalyst powder therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas phase temperature reaches 380 °C to remove the heavy oil solvent, and refined hydrogenated pitch is obtained, with its H content being 5.93 wt.%, the aromaticity index being 0.52, and the ash content being less than 95 ppm.

[0046] The refined hydrogenated pitch is pyrolyzed at 450 °C, 1.0 MPa absolute pressure, and in an argon atmosphere for 5 h to obtain primary pyrolyzed pitch; the primary pyrolyzed pitch is extracted with toluene to obtain toluene-insoluble matter, and the toluene-insoluble matter is pyrolyzed at 350 °C for 30 min to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 273 °C, a mesophase content of 99 vol.%, and a wide-field optical texture content > 95 vol.%.

[0047] Comparative Example 1

[0048] Using coal tar pitch as the raw material, the coal tar pitch and toluene are mixed and extracted at a mass ratio of 1:10 to obtain the toluene-soluble matter solution. The toluene-soluble matter solution is distilled at atmospheric pressure until the gas phase temperature reaches 170 °C to remove the toluene solvent, and coarsely refined pitch is obtained. The coarsely refined pitch and the heavy oil solvent are mixed and extracted at a mass ratio of 1:10, the centrifuge speed is set at 10,000 rpm to centrifugally separate the ash therein, and then the heavy oil solvent-soluble component is vacuum-distilled under a vacuum degree of -0.1 MPa until the gas phase temperature reaches 380 °C to remove the heavy oil solvent, and refined pitch is obtained. The H content of the refined pitch is 3.72 wt.%, the aromaticity index is 1.01, and the ash content is less than 96 ppm.

[0049] The refined pitch is pyrolyzed at 450 °C, 1.0 MPa absolute pressure, and in an argon atmosphere for 5 h to obtain primary pyrolyzed pitch; the primary pyrolyzed pitch is extracted with toluene to obtain toluene-insoluble matter, and the toluene-insoluble matter is pyrolyzed at 350 °C for 30 min to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 331 °C, a mesophase content of 91 vol.%, and the wide-field optical texture is only 87 vol.%.

[0050] Comparative Example 2

[0051] Coal tar pitch, solvent oil and catalyst were uniformly mixed in a mass ratio of 1:2:0.15 and then put into a suspension bed reactor. The catalyst uses γ-alumina as the carrier, and the specific surface area of the carrier is 274 m 2 / g, the pore volume is 1.1 ml / g, the pore diameter is 13.97 nm, and the MoO 3 loading amount is 20 wt.%, and the NiO loading amount is 1 wt.%. It was heated to 400 °C and heat-treated for 1 h under a hydrogen pressure of 20 MPa to obtain a hydrogenated product; then the obtained hydrogenated product was vacuum distilled to a gas phase temperature of 350 °C under a vacuum of -0.1 MPa to remove the solvent, and hydrogenated asphalt was obtained; then without going through a two-step extraction-centrifugation process to remove catalyst particles, the distilled product was dissolved and extracted with toluene in a mass ratio of 1:10, and the toluene-soluble component was distilled at atmospheric pressure to a gas phase temperature of 170 °C to remove toluene, and hydrogenated asphalt was prepared, with its H content being 4.01 wt.%, the aromaticity index being 0.95, and the ash content being 445 ppm.

[0052] The hydrogenated asphalt was pyrolyzed at 450 °C, 1.0 MPa absolute pressure, and in an argon atmosphere for 5 h to obtain primary pyrolytic asphalt; the primary pyrolytic asphalt was extracted with toluene to obtain toluene-insoluble matter, and the toluene-insoluble matter was pyrolyzed at 350 °C for 30 min to obtain mesophase pitch. The prepared mesophase pitch has a softening point of 305 °C, a mesophase content of 91 vol%, and a wide-area optical texture content greater than 90 vol.%.

[0053] According to Example 6, combined with Comparative Example 1, due to the catalytic hydrogenation modification of coal tar pitch, compared with refined asphalt, the H content of hydrogenated asphalt has increased significantly by 59.41%, and the aromaticity index has decreased significantly by 51.49%; at the same time, the mesophase pitch obtained from hydrogenated asphalt in Example 6, compared with the mesophase pitch synthesized from refined asphalt, has an increase in mesophase content of 33 vol% and an increase in wide-area optical texture content of 8 vol%, and the softening point has decreased significantly by 58 °C. Thus, it is confirmed that the suspension bed catalytic hydrogenation modification process in the example can effectively introduce H elements into coal tar pitch, reduce its aromaticity index, and thereby improve the quality of the product mesophase pitch.

[0054] According to Comparative Example 2, due to the failure to remove the residual catalyst particles in the reaction system, compared with the hydrogenated asphalt obtained in Comparative Example 2, the ash content of the hydrogenated asphalt obtained in Example 6 has decreased significantly by 350 ppm, and the softening point of the mesophase pitch obtained under the same synthesis process has decreased significantly by 32 °C, and the spinnability has become significantly better. Thus, it is confirmed the important influence of removing catalyst particles in the example when applied to the preparation of hydrogenated asphalt.

Claims

1. A method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed, characterized in that: The following steps are involved: Step 1, coal tar, solvent oil and catalyst are uniformly mixed in a mass ratio of 1:0.5-2:0.075-0.45 and then fed into a suspended bed reactor, and reacted to obtain a hydrogenation product under the conditions of a hydrogen pressure of 4-25 MPa, a temperature of 350-400° C. and a residence time of 0.5-3 h; Step 2: The hydrogenated product obtained in step 1 is subjected to reduced pressure distillation to remove the solvent oil, the reduced pressure distillation conditions being a vacuum degree of -0.1 MPa and a maximum gas phase temperature of 350° C., to obtain hydrogenated asphalt; Step 3, the hydrogenated asphalt obtained after the reduced pressure distillation in step 2 is mixed with an aromatic solvent at a mass ratio of 1:5 to 20 for extraction, and the catalyst particles are separated using a sintered metal filter with a filtration accuracy of 20 to 100 meshes to obtain a crude separation soluble solution of the aromatic solvent; Step 4, removing the aromatic solvent from the aromatic solvent crude separation soluble solution obtained in step 3 by atmospheric distillation to obtain crude separation hydrogenated asphalt; Step 5: Mix and extract the crudely separated hydrogenated asphalt obtained in step 4 with a heavy oil solvent in a mass ratio of 1:5 to 10, separate the catalyst powder by centrifugation, and obtain a heavy oil soluble solution; Step 6, distilling the heavy oil soluble solution obtained in step 5 under reduced pressure at a vacuum degree of -0.1 MPa and a maximum gas phase temperature of 380° C. to obtain refined hydrogenated asphalt; Step 7: subjecting the hydrogenated asphalt obtained in step 5 to thermal polycondensation reaction and mesophase enrichment to prepare a spinnable mesophase asphalt.

2. The method for preparing spinnable mesophase pitch by coal tar pitch suspension bed hydrogenation modification according to claim 1, characterized in that: In step 1, the coal tar pitch is the pitch obtained by distilling high-temperature coal tar at 180-360°C.

3. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 1, the solvent oil is selected from an aromatic solvent obtained by partially hydrogenating and saturating the fraction of high-temperature coal tar through vacuum distillation at a vacuum degree of -0.1 MPa and a gas phase temperature of 240-350°C, and the molecular structure is characterized by partially saturated condensed-ring aromatic hydrocarbons with a total number of 2-6 rings, wherein the number of cycloalkanes accounts for 20-70% of the total number of rings.

4. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 1, the suspended bed catalytic hydrogenation reaction is carried out in the presence of the following hydrorefining catalyst, the hydrorefining catalyst is: γ-alumina or silicon-containing alumina as a carrier, with a specific surface area of ​​120-300m2 / g, a pore volume of 0.4-1.4mL / g, a pore size of 8-20nm, and a surface acid content of 0.05-0.1mmol / g; the metal active component is a VIB group metal Mo or W, a VIII group metal Co or Ni; calculated based on the total mass of the hydrorefining catalyst, the VIB group metal content is 10-20wt.% in terms of oxide, and the VIII group metal content is 1-5wt.% in terms of oxide.

5. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 3, the aromatic solvent is selected from one or a mixture of two or more of benzene, toluene, xylene and cyclohexane.

6. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 5, the heavy oil solvent is selected from coal tar fraction oil and its partially hydrogenated saturated product, and its molecular structure is partially saturated condensed aromatic hydrocarbons with a total ring number of 4-7 rings, wherein the number of cycloalkanes is not more than 40% of the total number of rings.

7. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 5, the centrifugal separation is performed at a rotation speed of 5000 to 10000 rpm.

8. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 7, the thermal polycondensation reaction is carried out at a pressure of 0 to 3.0 MPa, an atmosphere of nitrogen or argon, a temperature of 380 to 460° C., and a stirring speed of 10 to 60 rpm for 3 to 24 hours.

9. The method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch suspension bed according to claim 1, characterized in that: In step 7, the intermediate phase enrichment includes but is not limited to benzene, toluene or xylene solvent extraction; nitrogen, hydrogen or argon gas flow purging; thin film evaporation.

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