Mesophase pitch and process for its preparation

Abstract

The application discloses mesophase pitch and a preparation method thereof, and the method comprises the following steps: placing 2-vinyl naphthalene or 9-vinyl anthracene, fused ring aromatic hydrocarbon and Lewis acid in an autoclave to perform Friedel-Crafts alkylation reaction for 2h-12h, so as to obtain a fused ring aromatic hydrocarbon product with a large planar molecular structure; and performing thermal polycondensation treatment on the fused ring aromatic hydrocarbon product with the large planar molecular structure in the autoclave for 6h-72h, so as to obtain mesophase pitch. The prepared mesophase pitch has good fluidity, high mesophase content, high carbon residue rate and good spinnability.

Description

Technical Field

[0001] This invention relates to the technical field of carbon, and more specifically to a mesophase pitch and its preparation method. Background Technology

[0002] Mesophase pitch possesses numerous advantages, including high char residue, high fluidity, and high graphitizability, making it suitable as a raw material for mesophase pitch-based carbon fibers, mesophase pitch-based foamed carbon, carbon-carbon composites, and high-performance graphite. Mesophase pitch is a disk-shaped nematic liquid crystal formed by the parallel arrangement of planar aromatic macromolecules under thermal condensation. Its formation is the result of chemical reactions and physical π-π interactions of polycyclic aromatic hydrocarbons. The emergence, growth, fusion, and deformation of mesophase spheres represent a series of structural transformations, a product of liquid-phase carbonization, and an essential step for easily graphitized organic materials to achieve highly graphitized structural materials.

[0003] Mesophase pitch is mainly prepared by thermal polycondensation of coal tar, coal tar pitch, petroleum residue or petroleum pitch, and synthetic naphthalene pitch. The use of coal tar, coal tar pitch, petroleum residue or petroleum pitch for thermal polycondensation has significant drawbacks, primarily due to the complexity of raw material sources, difficulties in ash treatment, and catalyst residue. Furthermore, the thermal polycondensation of naphthalene pitch can lead to flowability problems. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a mesophase asphalt and its preparation method, which can produce mesophase asphalt with high fluidity and high mesophase content.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for preparing mesophase pitch in a first aspect, comprising the following steps:

[0006] 2-vinylnaphthalene or 9-vinylanthracene, polycyclic aromatic hydrocarbons and Lewis acids are placed in a high-pressure reactor and subjected to Friedel-Crafts alkylation for 2 h to 12 h to obtain polycyclic aromatic hydrocarbon products with large planar molecular structures.

[0007] The polycyclic aromatic hydrocarbon product with the large planar molecular structure was subjected to thermal polycondensation treatment in an autoclave for 6 to 72 hours to obtain mesophase pitch.

[0008] According to an embodiment of the present invention, a method for preparing mesophase pitch involves a Lewis acid-catalyzed Friedel-Crafts alkylation reaction of a highly reactive monomer (2-vinylnaphthalene or 9-vinylanthracene) with a polycyclic aromatic hydrocarbon to obtain a polycyclic aromatic hydrocarbon molecule with a large planar structure and an alkane structure. This molecule is then subjected to thermal polycondensation to obtain mesophase pitch with high fluidity and a high mesophase content. The polycyclic aromatic hydrocarbon molecule with a large planar structure and an alkane structure exhibits high purity and good structural controllability. During thermal polycondensation, it demonstrates strong π-π interactions, readily forming a mesophase. Furthermore, its alkyl structure contributes to its good fluidity. The mesophase pitch obtained after thermal polycondensation exhibits good fluidity, high mesophase content, high char residue, and good spinnability.

[0009] Optionally, the polycyclic aromatic hydrocarbon is naphthalene, dinaphthalene, anthracene, or phenanthrene.

[0010] Optionally, the Lewis acid is FeCl3, AlCl3, or HF / BF3.

[0011] Optionally, the Friedel-Crafts alkylation reaction is carried out at a temperature of 120°C to 220°C and a pressure of 0.5 MPa to 10 MPa.

[0012] Furthermore, the Friedel-Crafts alkylation reaction is carried out at a temperature of 130°C to 180°C and a pressure of 1 MPa to 3 MPa.

[0013] Optionally, the Lewis acid is in a weight ratio of 0.02 to 3 with 2-vinylnaphthalene or 9-vinylanthracene.

[0014] Optionally, the Friedel-Crafts alkylation reaction can be carried out for 3 to 8 hours.

[0015] Optionally, the thermal polycondensation treatment time is 12h to 18h.

[0016] An embodiment of the present invention provides, in a second aspect, mesophase pitch prepared by the above-described method.

[0017] According to the embodiments of the present invention, the mesophase pitch using the above-described method has a wide range of raw material sources and is composed of highly stable chemicals. A stable chemical structure is obtained by using Lewis acid catalysis. A stable precursor is very important for the preparation of mesophase pitch. Furthermore, the synthesized precursor also contains alkane and cycloalkane structures. The ability to form a mesophase and the fluidity during the thermal polycondensation process are well balanced, which can produce high-performance mesophase pitch.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] Figure 1A polarized light micrograph of mesophase pitch prepared according to Example 1 of the present invention;

[0020] Figure 2 The image shows a polarized light micrograph of mesophase pitch prepared according to the comparative example of this invention. Detailed Implementation

[0021] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0022] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0023] The test materials used in this invention are all common commercial products and can be purchased on the market.

[0024] The softening point was determined according to GB2294-80; the intermediate phase content was estimated using a polarizing microscope; group composition analysis: toluene soluble matter (determined according to GB2292-80), pyridine insoluble matter (determined according to GB2293-80), quinoline insoluble matter (determined according to GB2293-2008).

[0025] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0026] Example 1

[0027] 302 kg of solid 2-vinylnaphthalene and 128 kg of naphthalene were added to a high-pressure reactor equipped with a heating mantle. 10 kg of HF / BF3 (HF / BF3 weight ratio of 2) was added, and the mixture was heated to 140°C and purged with nitrogen to a pressure of 6 MPa. After reacting for 6 hours, the catalyst was removed by vacuuming. After the catalyst was removed, the product was subjected to thermal polycondensation treatment in a high-pressure reactor at a temperature of 410°C for 18 hours. After treatment, the product was removed from the reactor and subjected to group composition analysis, softening point testing, and mesophase content analysis.

[0028] The softening point of the mesophase pitch in this embodiment is 245°C, with 35% toluene-soluble content, 44% pyridine-insoluble content, 23% quinoline-insoluble content, 100% mesophase content, and 82% char residue. A polarized light micrograph of the mesophase pitch is shown below. Figure 1 As shown.

[0029] Example 2

[0030] 302 kg of solid 2-vinylnaphthalene and 128 kg of naphthalene were added to a high-pressure reactor equipped with a heating mantle. 20 kg of HF / BF3 (HF / BF3 weight ratio of 2) was added, and the mixture was heated to 150°C and purged with nitrogen to a pressure of 6 MPa. After reacting for 6 hours, the catalyst was removed by vacuuming. After the catalyst was removed, the product was subjected to thermal polycondensation treatment in a high-pressure reactor at a temperature of 420°C for 18 hours. After treatment, the product was removed from the reactor and subjected to group composition analysis, softening point testing, and mesophase content analysis.

[0031] The softening point of the mesophase pitch in this embodiment is 262°C, the toluene-soluble content is 31%, the pyridine-insoluble content is 47%, the quinoline-insoluble content is 30%, the mesophase content is over 99%, and the residual carbon rate is 85%.

[0032] Example 3

[0033] 302 kg of solid 2-vinylnaphthalene and 128 kg of naphthalene were added to a high-pressure reactor equipped with a heating mantle, along with 40 kg of anhydrous aluminum chloride. The mixture was heated to 150°C and purged with nitrogen to a pressure of 6 MPa. After reacting for 6 hours, the catalyst was removed by vacuum. After complete removal, the product was subjected to thermal polycondensation treatment in a high-pressure reactor at a temperature of 410°C for 12 hours. After treatment, the product was removed from the reactor and subjected to group composition analysis, softening point testing, and mesophase content analysis.

[0034] The softening point of the mesophase pitch in this embodiment is 242°C, the toluene-soluble content is 47%, the pyridine-insoluble content is 40%, the quinoline-insoluble content is 26%, the mesophase content is over 85%, and the carbon residue is 78%.

[0035] Example 4

[0036] 302 kg of solid 2-vinylnaphthalene and 128 kg of naphthalene were added to a high-pressure reactor equipped with a heating mantle, along with 20 kg of anhydrous aluminum chloride. The mixture was heated to 150°C and purged with nitrogen gas to a pressure of 6 MPa. After reacting for 6 hours, the catalyst was removed by vacuum. After complete removal, the product was subjected to thermal polycondensation treatment in a high-pressure reactor at a temperature of 430°C for 12 hours. After treatment, the product was removed from the reactor and subjected to group composition analysis, softening point testing, and mesophase content analysis.

[0037] The softening point of the mesophase pitch in this embodiment is 268°C, the toluene-soluble content is 38%, the pyridine-insoluble content is 46%, the quinoline-insoluble content is 37%, the mesophase content is over 90%, and the residual carbon rate is 83%.

[0038] Example 5

[0039] 302 kg of solid 9-vinylanthracene and 128 kg of naphthalene were added to a high-pressure reactor equipped with a heating mantle. 10 kg of HF / BF3 (HF / BF3 weight ratio of 2) was added, and the mixture was heated to 140°C and purged with nitrogen to a pressure of 6 MPa. After reacting for 6 hours, the catalyst was removed by vacuum. After the catalyst was removed, the product was subjected to thermal polycondensation treatment in a high-pressure reactor at a temperature of 410°C for 18 hours. After treatment, the product was removed from the reactor and subjected to group composition analysis, softening point testing, and mesophase content analysis.

[0040] The softening point of the mesophase pitch in this embodiment is 267°C, the toluene-soluble content is 32%, the pyridine-insoluble content is 51%, the quinoline-insoluble content is 39%, the mesophase content is 99%, and the carbon residue is 82%.

[0041] Comparative Example

[0042] 128g of solid naphthalene was added to a high-pressure reactor equipped with a heating jacket, and a certain amount of 93g of HF / BF3 (HF / BF3 molar ratio of 6:1) was added. The mixture was heated to 140℃ and purged with nitrogen to a pressure of 2MPa. After reacting for 8 hours, the catalyst was removed by vacuuming. After the catalyst was removed, the product was subjected to thermal polycondensation treatment at 400℃ for a certain period of time to obtain mesophase pitch. The product was then poured out of the reactor for group composition analysis, softening point testing, and mesophase content analysis.

[0043] The softening point of the mesophase pitch in this comparative example was 254℃, the yield was 53%, and the mesophase content was 100%. Its polarized light micrograph is shown below. Figure 2 As shown, the mesophase pitch domain texture obtained in this comparative example is not as good as that of the mesophase pitch obtained in this application (Example 1). The mesophase pitch of this application is wider and has a flow basin structure, which is beneficial to the flowability of the mesophase and the realization of subsequent spinning, impregnation and other processes.

[0044] In summary, according to the embodiments of the present invention, a Lewis acid-catalyzed highly reactive monomer is used to carry out a Friedel-Crafts reaction with a polycyclic aromatic hydrocarbon to obtain a polycyclic aromatic hydrocarbon molecule with a large planar structure and an alkane structure. The molecule is then subjected to thermal polycondensation treatment to obtain a mesophase pitch with high fluidity and high mesophase content. The raw materials used have the advantages of low price and simple and easy-to-separate catalyst.

[0045] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0046] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing mesophase pitch, characterized in that, Includes the following steps: 2-Vinylnaphthalene or 9-vinylanthracene, polycyclic aromatic hydrocarbons, and Lewis acids are placed in an autoclave for Friedel-Crafts alkylation for 2 h to 12 h. The catalyst is then removed under vacuum to obtain a polycyclic aromatic hydrocarbon product with a large planar molecular structure. The weight ratio of Lewis acid to 2-vinylnaphthalene or 9-vinylanthracene is 0.02 to 3. The Friedel-Crafts alkylation reaction is carried out at a temperature of 120℃ to 220℃ and a pressure of 0.5 MPa to 10 MPa. The Friedel-Crafts alkylation reaction is carried out for 3 h to 8 h. The polycyclic aromatic hydrocarbon product with a large planar molecular structure is then subjected to thermal polycondensation in an autoclave for 6 h to 72 h to obtain mesophase pitch. The thermal polycondensation treatment temperature is 410℃, 420℃, or 430℃.

2. The preparation method according to claim 1, characterized in that, The polycyclic aromatic hydrocarbon is naphthalene, dinaphthalene, anthracene, or phenanthrene.

3. The preparation method according to claim 1, characterized in that, The Lewis acids are FeCl3, AlCl3, and HF / BF3.

4. The preparation method according to claim 1, characterized in that, The Friedel-Crafts alkylation reaction is carried out at temperatures ranging from 130°C to 180°C and pressures ranging from 1 MPa to 3 MPa.

5. The preparation method according to claim 1, characterized in that, The heat shrinkage treatment time is 12 h to 18 h.

6. Mesophase pitch prepared by any one of claims 1-5.

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