Mesophase pitch, process for its preparation and use thereof

Abstract

The present application relates to the technical field of petroleum chemical industry, in particular to a mesophase pitch and a preparation method and application thereof. The method comprises the following steps: (1) performing a first thermal conversion reaction on raw materials containing catalytic cracking slurry oil distillate oil and aromatic hydrocarbon compounds to obtain a first thermal conversion product; (2) performing a first extraction on the first thermal conversion product and a solvent I, and performing a first distillation on the obtained extraction liquid to obtain an extraction product; (3) performing a second thermal conversion reaction on the extraction product to obtain a second thermal conversion product; (4) performing a second extraction on the second thermal conversion product and a solvent II, and performing a second distillation on the obtained raffinate phase to obtain a mesophase pitch; wherein the distillation range of the catalytic cracking slurry oil distillate oil is 400-490 DEG C. The mesophase pitch prepared by the method has the characteristics of moderate softening point, high mesophase content and good spinnability, and can be used as a high-quality raw material for high-performance pitch-based carbon fibers.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, specifically to a mesophase pitch, its preparation method, and its application. Background Technology

[0002] Carbon fiber, based on the different spinning raw materials, can be divided into polyacrylonitrile-based carbon fiber and pitch-based carbon fiber. Pitch-based carbon fiber can be further divided into general-purpose pitch-based carbon fiber and high-performance pitch-based carbon fiber based on the type of pitch. Compared with high-performance polyacrylonitrile-based carbon fiber, high-performance pitch-based carbon fiber has a higher degree of graphitization, higher modulus, and greater thermal and electrical conductivity. It has the highest modulus among materials currently available for mass production, reaching over 90% of the theoretical modulus of graphite materials, making it irreplaceable in applications where modulus is paramount. Due to its excellent properties such as high strength, high modulus, high temperature resistance, and low density, high-performance pitch-based carbon fiber is widely used in various fields, including military, aerospace, aerospace electronic devices, and high-end industrial equipment.

[0003] Since the 1990s, domestic companies have built production lines to try to produce spinning asphalt, but all of them have stopped production because the preparation of spinning asphalt is too difficult and there is no qualified spinning asphalt available.

[0004] CN108102679A discloses a method for refining coal tar pitch for synthesizing mesophase pitch. This method separates the effective components of coal tar pitch from impurities such as residual coal powder and coke particles in the original coal tar pitch under normal pressure. The resulting refined coal tar pitch can be used as a raw material for high-end carbon materials. However, coal tar pitch has a low hydrogen content, resulting in a high softening point and poor rheological properties in the prepared mesophase pitch, making it difficult to meet the spinning requirements of high-performance pitch-based carbon fibers.

[0005] CN110629326A discloses a method for preparing high thermal conductivity mesophase pitch-based carbon fibers and high-quality mesophase pitch. This method involves mixing graphene, a hydrogen donor, and purified coal tar pitch, and directly performing a thermal condensation reaction in a high-pressure autoclave to prepare mesophase pitch. The prepared mesophase pitch can be used to produce carbon fibers with excellent mechanical properties and thermal and electrical conductivity. However, graphene is costly, difficult to recover from the product, and has a high ash content.

[0006] CN110628449A discloses a method for preparing spinning-grade synthetic mesophase pitch. This method involves adding ZrCl2 as a catalyst to a pure aromatic compound and reacting it at 200-320℃ for 2-5 hours to obtain an aromatic oligomer. The product is then dissolved in pyridine, and the solid catalyst is removed by filtration. The solvent pyridine is recovered by distillation to obtain a catalyst-free aromatic oligomer. Finally, the aromatic oligomer is subjected to a thermal polycondensation reaction at 390-420℃ for 10-20 hours to obtain mesophase pitch. However, the use of a ZrCl2 solid catalyst makes complete separation difficult, easily resulting in a high ash content in the product, affecting spinnability.

[0007] However, the mesophase pitches prepared by the above methods all have drawbacks such as high softening point, low mesophase content, and poor spinnability. Therefore, a new method for preparing mesophase pitches is urgently needed. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of corrosion caused by the use of catalysts, difficulty in catalyst separation, high softening point, low mesophase content, and poor spinnability in the preparation of mesophase asphalt. This invention provides a mesophase asphalt, its preparation method, and its application. This method, without the use of catalysts, uses a combination of conventional techniques to produce mesophase asphalt with moderate softening point, high mesophase content, and good spinnability. At the same time, this method simplifies the process flow and facilitates industrial production.

[0009] To achieve the above objectives, the first aspect of the present invention provides a method for preparing mesophase pitch, the method comprising the following steps:

[0010] (1) The feedstock containing catalytic cracking slurry oil and aromatic compounds is subjected to a first thermal conversion reaction to obtain the first thermal conversion product;

[0011] (2) The first thermal conversion product and solvent I are subjected to a first extraction, and the resulting extract is subjected to a first distillation to obtain the extract product;

[0012] (3) The extraction product is subjected to a second thermal conversion reaction to obtain a second thermal conversion product;

[0013] (4) The second thermal conversion product and solvent II are subjected to a second extraction, and the resulting raffinate is subjected to a second distillation to obtain the intermediate phase pitch;

[0014] The distillation range of the catalytic cracking slurry oil is 400-490℃.

[0015] The second aspect of the present invention provides an mesophase pitch prepared by the method provided in the first aspect.

[0016] The third aspect of the present invention provides an application of the mesophase pitch provided in the second aspect in pitch-based carbon fibers.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The method provided by the present invention avoids the problems of catalyst corrosion and separation caused by the use of catalysts in the preparation of mesophase asphalt by using a combination of thermal conversion reaction, solvent extraction and distillation. It prepares mesophase asphalt with moderate softening point, high mesophase content and good spinnability. At the same time, the method uses catalytic cracking slurry oil and aromatic compounds as raw materials, which expands the raw material source of mesophase asphalt.

[0019] (2) The method provided by the present invention simplifies the process flow, is easy to operate, and is convenient for industrial production;

[0020] (3) The mesophase pitch provided by the present invention has the characteristics of moderate softening point, high mesophase content and good spinnability, and can be used as a high-quality raw material for high-performance pitch-based carbon fiber. Attached Figure Description

[0021] Figure 1 This is a polarized light microscopy reflectance photograph of the mesophase pitch S1 prepared in Example 1;

[0022] Figure 2 This is a polarized light microscopy reflectance photograph of the mesophase pitch S2 obtained in Example 2;

[0023] Figure 3 This is a polarized light microscopy reflection image of the mesophase pitch S3 obtained in Example 3. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] In this invention, unless otherwise specified, the terms "first" and "second" do not indicate a sequence or limit the specific materials or steps; they are merely used to distinguish between them. For example, "first" and "second" in "first thermal conversion reaction" and "second thermal conversion reaction" are simply used to distinguish that they are not the same thermal conversion reaction; "first" and "second" in "first thermal conversion product" and "first thermal conversion product" are simply used to distinguish that they are not the same thermal conversion product; "first" and "second" in "first distillation" and "second distillation" are simply used to distinguish that they are not the same distillation.

[0026] The first aspect of this invention provides a method for preparing mesophase pitch, the method comprising the following steps:

[0027] (1) The feedstock containing catalytic cracking slurry oil and aromatic compounds is subjected to a first thermal conversion reaction to obtain the first thermal conversion product;

[0028] (2) The first thermal conversion product and solvent I are subjected to a first extraction, and the resulting extract is subjected to a first distillation to obtain the extract product;

[0029] (3) The extraction product is subjected to a second thermal conversion reaction to obtain a second thermal conversion product;

[0030] (4) The second thermal conversion product and solvent II are subjected to a second extraction, and the resulting raffinate is subjected to a second distillation to obtain the intermediate phase pitch;

[0031] The distillation range of the catalytic cracking slurry oil is 400-490℃.

[0032] In some embodiments of the present invention, preferably, the distillation range of the catalytic cracking slurry oil is 20-50°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 50°C, and any value within any two of the ranges, preferably 20-35°C, and most preferably 30°C.

[0033] In some embodiments of the present invention, preferably, the distillation range of the catalytic cracking slurry oil is 400-430℃, 430-460℃, or 460-490℃, and more preferably 430-460℃.

[0034] In this invention, the source of the catalytic cracking slurry distillate has a wide range of selection, as long as the catalytic cracking slurry distillate meets the above-mentioned limitations. Preferably, the catalytic cracking slurry distillate is obtained by fractionation of catalytic cracking slurry; more preferably, the total heteroatom content in the catalytic cracking slurry is ≤3wt%, preferably 0.1-1wt%; the solid content is ≤20mg / kg, preferably 1-10mg / kg. The heteroatoms are S, N, and O atoms. Using these preferred conditions is more conducive to improving the performance of the mesophase asphalt. Preferably, when the heteroatom content or solid content in the catalytic cracking slurry is high, the catalytic cracking slurry needs to undergo impurity removal or solidification removal treatment before fractionation to ensure that the heteroatom content or solid content meets the above-mentioned limitations.

[0035] In this invention, unless otherwise specified, the heteroatom content parameter is measured using the petrochemical industry standard "Determination of carbon, hydrogen and nitrogen in petroleum products and lubricants (elemental analyzer method) (SH / T 0656-2017)"; the solid content is measured using the standard "Determination of ash content in petroleum products (GB 508-1985)". The solid content refers to the catalytic cracking catalyst powder in the catalytic cracking slurry.

[0036] In some embodiments of the present invention, preferably, the weight ratio of catalytic cracking slurry oil to aromatic compounds in the raw material is 1:1-10, for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:10, and any value within any two numerical ranges, preferably 1:2-5, and most preferably 1:3. In the present invention, adding a certain amount of aromatic compounds can effectively improve the uniformity of spheres in mesophase asphalt; however, when the amount of aromatic compounds added is too high, the resulting mesophase asphalt has low hydrogen content and poor rheological properties.

[0037] In some embodiments of the present invention, preferably, the aromatic compound is anthracene.

[0038] In this invention, during the first and second thermal conversion reactions, as the system temperature increases and the reaction proceeds, the hydrocarbons in the feedstock simultaneously undergo cracking and polymerization reactions. The cracking produces gasoline fractions, diesel fractions, wax oil fractions, light hydrocarbon gases, and a small amount of hydrogen. The polymerization reaction achieves an increase in the number of aromatic rings at the cost of dehydrogenation. After cracking, due to the closed nature of the reactor, the pressure in the reactor gradually increases, and the gasoline fraction, diesel fraction, and part of the wax oil fraction remain in the liquid phase. This helps reduce the viscosity of the liquid phase and prevents excessively rapid local reactions and over-polymerization in the system.

[0039] In some embodiments of the present invention, preferably, the first thermal conversion reaction and the second thermal conversion reaction are carried out independently in a reaction vessel, and the present invention does not limit the type of reaction vessel.

[0040] In this invention, the first thermal conversion reaction achieves the initial polycondensation of the raw materials under relatively high pressure. Preferably, in step (1), the conditions for the first thermal conversion reaction include: a temperature of 400-480℃, preferably 430-450℃; a time of 2-8h, preferably 3-5h; and a pressure of 2-6MPa, preferably 3-5MPa.

[0041] In this invention, unless otherwise specified, all pressures are gauge pressures.

[0042] In this invention, in step (1), the feedstock containing catalytic cracking slurry oil and aromatic compounds is subjected to a first thermal conversion reaction, and the first thermal conversion product contains 5-10 wt% toluene insoluble matter.

[0043] In this invention, in step (2), solvent I is intended to precipitate the toluene-insoluble matter in the first thermal conversion product, and the actual amount precipitated is inversely proportional to the amount of solvent I added within a certain range. Preferably, the weight ratio of the first thermal conversion product to solvent I is 1:1-5, for example, 1:1, 1:3, 1:4, 1:5, and any value within the range of any two values, preferably 1:3-5.

[0044] In some embodiments of the present invention, preferably, solvent I is selected from at least one of toluene, furfural, n-heptane and pyridine, and more preferably, solvent I is toluene.

[0045] In this invention, in step (2), the first extraction can remove 60%-80% of the heavier components in the insoluble matter. This component is the component with the highest degree of polymerization and the most likely to form coke in the system. The removal of this component is beneficial to the molecular weight distribution of the final spinning pitch and reduces quinoline insoluble matter.

[0046] In this invention, the first distillation aims to remove solvent I from the extract to obtain the extract product. Preferably, the recovered solvent I obtained from the first distillation is returned as a circulating solvent and mixed into the solvent I. In this invention, the method of the first distillation is not particularly limited, as long as solvent I is removed from the extract to obtain the extract product.

[0047] In some embodiments of the present invention, preferably, in step (2), the conditions for the first distillation include: a temperature of 85-105°C, preferably 95-100°C; a time of 1-3 hours, preferably 1.5-2.5 hours; and an absolute pressure of <20 kPa, preferably 7-8 kPa.

[0048] According to the present invention, preferably, the boiling point of the extracted product is 180-550℃, more preferably 200-500℃.

[0049] In this invention, the second thermal conversion reaction achieves the conversion of the extraction product into mesophase pitch. Preferably, in step (3), the conditions for the second thermal conversion reaction include: a temperature of 380-450℃, preferably 400-430℃; a time of 1-10h, preferably 2-4h; and a pressure of 0.5-5MPa, preferably 1-3MPa. In this invention, the second thermal conversion reaction is carried out in a closed, self-pressurized manner.

[0050] In some embodiments of the present invention, preferably, the weight ratio of the second thermal conversion product to solvent II is 1:1-3, for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, and any value within the range of any two values, preferably 1:1.5-2.5. The greater the amount of solvent II used, the greater the content of the mesophase and the lower the hydrogen content.

[0051] In this invention, the second extraction aims to remove the non-asphaltitic components of the second thermal conversion product, obtaining cake-shaped asphalt as the raffinate phase. Preferably, in step (4), the temperature of the second extraction is 60-120°C, for example, 60°C, 80°C, 90°C, 100°C, 120°C, and any value within the range of any two of these values, preferably 80-100°C.

[0052] In some embodiments of the present invention, preferably, solvent II is selected from at least one of toluene, furfural, n-heptane and pyridine, and more preferably a mixed solvent containing toluene and n-heptane.

[0053] In some embodiments of the present invention, preferably, the volume ratio of toluene to n-heptane in the mixed solvent containing toluene and n-heptane is 1-4:5-10, more preferably 3:7.

[0054] In this invention, the second distillation aims to remove residual solvent II and low-boiling-point components from the raffinate phase to obtain mesophase pitch. This invention offers a wide range of options for the method of second distillation; preferably, the second distillation is performed under reduced pressure.

[0055] In some embodiments of the present invention, preferably, the conditions for vacuum distillation include: a cutting temperature of 500-530°C, more preferably 515-525°C; and an absolute pressure of 0.1-0.3 mmHg, more preferably 0.15-0.25 mmHg.

[0056] According to a particularly preferred embodiment of the present invention, the method includes the following steps:

[0057] (1) The feedstock containing catalytic cracking slurry oil and anthracene is subjected to a first thermal conversion reaction to obtain the first thermal conversion product;

[0058] (2) The first thermal conversion product and solvent I are subjected to a first extraction, and the resulting extract is distilled to obtain the extract product;

[0059] (3) The extraction product is subjected to a second thermal conversion reaction to obtain a second thermal conversion product;

[0060] (4) The second thermal conversion product and solvent II are subjected to a second extraction, and the resulting raffinate is subjected to vacuum distillation to obtain the intermediate phase pitch;

[0061] The distillation range of the catalytic cracking slurry oil is 430-460℃;

[0062] The conditions for the first thermal conversion reaction include: a temperature of 430-450℃; a time of 3-5h; and a pressure of 3-5MPa. The conditions for the second thermal conversion reaction include: a pressure of 0.5-5MPa; a temperature of 400-430℃; and a time of 2-4h. The conditions for the vacuum distillation include: a cutting temperature of 515-525℃; and an absolute pressure of 0.15-0.25mmHg.

[0063] The second aspect of the present invention provides an mesophase pitch prepared by the method provided in the first aspect.

[0064] According to the present invention, preferably, the mesophase content of the mesophase asphalt is ≥60wt%, more preferably ≥80wt%; the softening point is 260-310℃, more preferably 285-300℃; the C element content is 94.5-95.5wt%, more preferably 94.5-95wt%; and the H element content is 4-4.5wt%, more preferably 4.3-4.5wt%.

[0065] According to the present invention, preferably, the mesophase morphology of the mesophase asphalt is selected from streamlined and / or spherical. When the mesophase morphology of the mesophase asphalt is streamlined, the mesophase asphalt has excellent spinnability; when the mesophase morphology of the mesophase asphalt is a combination of streamlined and spherical, the mesophase asphalt has good spinnability; when the mesophase morphology of the mesophase asphalt is spherical, the mesophase asphalt has a certain degree of spinnability.

[0066] In this invention, unless otherwise specified, the method for observing the mesophase morphology is as follows: First, 4-5g of mesophase pitch sample is embedded inside epoxy resin, and a curing agent, polyene polyamine, is added. Then, after the epoxy resin has cured, the surface of the embedded sample is metallographically polished. Finally, the polished surface is observed using a polarizing microscope for polarized light reflection. The mesophase component appears as a bright area under the polarizing microscope, while the non-mesophase component appears as a dark area. The percentage of the total image area occupied by the bright area is the mesophase content, which can be directly determined using Leica Microsystems' LAS image processing software.

[0067] In this invention, unless otherwise specified, the softening point parameter is measured using the "ASTM D3104 Standard Test Method for Softening Point of Bituminous Pitch (Mettler Softening Point Method)"; the elemental content parameter is measured using the petrochemical industry standard "Determination of Carbon, Hydrogen and Nitrogen in Petroleum Products and Lubricants (Elemental Analyzer Method) (SH / T0656-2017)".

[0068] The third aspect of the present invention provides an application of the mesophase pitch provided in the second aspect in pitch-based carbon fibers.

[0069] The present invention will be described in detail below through embodiments.

[0070] The hydrocarbon composition of the feedstock oil was determined according to the petrochemical industry standard "Determination of Hydrocarbons in Saturated Hydrocarbon Fractions of Gas Oil (Mass Spectrometry) (SH / T 0659-1998)";

[0071] The method for observing the mesophase morphology is as follows: First, 4-5g of mesophase pitch sample is embedded inside epoxy resin, and a curing agent, polyene polyamine, is added. After the epoxy resin cures, the surface of the embedded sample is metallographically polished. Finally, the polished surface is observed using a polarizing microscope. The mesophase component appears as a bright area under the polarizing microscope, while the non-mesophase component appears as a dark area. The percentage of the total image area occupied by the bright area is the mesophase content, which can be directly determined using the LAS image processing software from Leica Microsystems.

[0072] The softening point parameter was measured using the "ASTM D3104 Standard Test Method for Softening Point of Bituminous Pitch (Mettler Softening Point Method)".

[0073] The elemental content parameters in raw materials and products were determined using the petrochemical industry standard "Determination of carbon, hydrogen and nitrogen in petroleum products and lubricants (elemental analyzer method) (SH / T 0656-2017)".

[0074] Example 1

[0075] (1) The catalytic cracking slurry distillate (distillation range 430-460℃, composition analysis listed in Table 1) and anthracene were mixed at a weight ratio of 1:3, and 500g of the obtained feedstock was subjected to the first thermal conversion reaction (temperature 440℃, time 3h, pressure 3.25MPa) to obtain the first thermal conversion product.

[0076] (2) Extract the first thermal conversion product and solvent I (toluene) at a weight ratio of 1:5, and distill the resulting extract (temperature 95℃, absolute pressure 8kPa) to obtain an extract with a boiling point of 200-550℃.

[0077] (3) The above-extracted product was subjected to a second thermal conversion reaction (temperature 420℃, time 2h, pressure 1.89MPa) to obtain the second thermal conversion product;

[0078] (4) The above-mentioned second thermal conversion product and solvent II (toluene and n-heptane in a volume ratio of 3:7) were extracted at a weight ratio of 1:2 (at a temperature of 100°C). The raffinate was subjected to vacuum distillation (cutting temperature of 525°C and operating absolute pressure of 0.2 mmHg) to obtain mesophase pitch S1. The physical properties of mesophase pitch S1 are listed in Table 2.

[0079] Among them, the polarized light microscopy reflectance photograph of mesophase pitch S1 is as follows: Figure 1 As shown, by Figure 1 It can be seen that the mesophase morphology of mesophase asphalt S1 is streamlined.

[0080] Spinning at 1 MPa and 329℃ can be performed continuously for 30 minutes at a spinning speed of 200 m / min. Therefore, mesophase pitch S1 has excellent spinnability.

[0081] Table 1

[0082]

[0083] Example 2

[0084] (1) The catalytic cracking slurry distillate (distillation range 430-460℃, composition analysis listed in Table 1) and anthracene were mixed at a weight ratio of 1:3, and 500g of the obtained feedstock was subjected to the first thermal conversion reaction (temperature 440℃, time 2h, pressure 2.7MPa) to obtain the first thermal conversion product.

[0085] (2) Extract the first thermal conversion product and solvent I (toluene) at a weight ratio of 1:5, and distill the resulting extract (temperature 95℃, operating absolute pressure 8kPa) to obtain an extract with a boiling point of 180-520℃.

[0086] (3) The above-extracted product was subjected to a second thermal conversion reaction (temperature 440℃, time 2h, pressure 2.33MPa) to obtain the second thermal conversion product;

[0087] (4) The above-mentioned second thermal conversion product and solvent II (n-heptane) were extracted at a weight ratio of 1:2 (at a temperature of 90°C). The raffinate was subjected to vacuum distillation (cutting temperature of 530°C and operating absolute pressure of 0.2 mmHg) to obtain mesophase pitch S2. The physical properties of mesophase pitch S2 are listed in Table 2.

[0088] Among them, the polarized light microscopy reflectance photograph of mesophase pitch S2 is as follows: Figure 2 As shown, by Figure 2 It can be seen that the mesophase morphology of mesophase pitch S2 is spherical.

[0089] Spinning was performed at 1 MPa and 326℃, and continuous spinning was achieved for 10 minutes at a spinning speed of 50 m / min. Therefore, mesophase pitch S2 has a certain degree of spinnability.

[0090] Example 3

[0091] The method of Example 1 is different except that in step (1), the weight ratio of catalytic cracking slurry distillate (distillation range of 430-460℃) and anthracene is 1:2, and the other conditions are the same, to obtain mesophase pitch S3, wherein the physical properties of mesophase pitch S3 are listed in Table 2.

[0092] Among them, the polarized light microscopy reflectance photograph of mesophase pitch S3 is as follows: Figure 3 As shown, by Figure 3 It can be seen that the mesophase morphology of mesophase asphalt S3 is a combination of streamlined and spherical shapes.

[0093] Spinning was performed at 1 MPa and 350℃, and continuous spinning could be achieved for 30 minutes at a spinning speed of 100 m / min. Therefore, mesophase pitch S3 has good spinnability.

[0094] Example 4

[0095] The method of Example 1 is different except that in step (2), the weight ratio of the first thermal conversion product and solvent I (toluene) is 1:2, and the other conditions are the same, to obtain mesophase pitch S4, wherein the physical properties of mesophase pitch S4 are listed in Table 2.

[0096] Example 5

[0097] The method of Example 1 is different except that in step (3), the temperature of the second thermal conversion reaction is 440°C and the time is 3h, while the other conditions are the same, to obtain mesophase asphalt S5. The physical properties of mesophase asphalt S5 are listed in Table 2.

[0098] Example 6

[0099] The method of Example 1 is different except that in step (4), the weight ratio of the second thermal conversion product and solvent II (toluene and n-heptane in a volume ratio of 3:7) is replaced with 1:1, and the other conditions are the same, to obtain mesophase pitch S6, wherein the physical properties of mesophase pitch S6 are listed in Table 2.

[0100] Comparative Example 1

[0101] The method of Example 1 is different except that step (3) is omitted. The extract obtained in step (2) is directly extracted with solvent II (n-heptane) under the same conditions to obtain asphalt DS1. The physical properties of asphalt DS1 are listed in Table 2.

[0102] Comparative Example 2

[0103] Following the method of Example 1, except that catalytic cracking slurry distillate (distillation range 430-460℃) was directly used as raw material, and the other conditions were the same, to obtain mesophase pitch DS2. The physical properties of mesophase pitch DS2 are listed in Table 2.

[0104] Table 2

[0105]

[0106] Continued from Table 2

[0107]

[0108] As shown in Table 2, compared to the comparative example, the mesophase pitch prepared by the method provided in this invention has the characteristics of moderate softening point, high mesophase content, and good spinnability. In particular, by limiting the weight ratio of catalytic cracking oil slurry fraction and aromatic compounds in the raw materials, as well as the conditions of the first thermal conversion reaction and the second thermal conversion reaction, the overall performance of the mesophase pitch is further improved. Furthermore, the method provided in this invention broadens the sources of mesophase pitch raw materials, and the mesophase pitch prepared by this invention has the characteristics of high mesophase content, moderate softening point, and good spinnability, making it a high-quality raw material for pitch-based carbon fibers.

[0109] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing mesophase pitch, characterized in that, The method includes the following steps: (1) The feedstock containing catalytic cracking slurry oil and aromatic compounds is subjected to a first thermal conversion reaction to obtain the first thermal conversion product; The weight ratio of catalytic cracking slurry oil and aromatic compounds in the feedstock is 1:1-10; The aromatic compound is anthracene; In step (1), the conditions for the first thermal conversion reaction include: temperature of 400-480℃; time of 2-8h; and pressure of 2-6 MPa. (2) The first thermal conversion product and solvent I are subjected to a first extraction, and the resulting extract is subjected to a first distillation to obtain the extract product; Solvent I is selected from at least one of toluene, furfural, n-heptane, and pyridine; (3) The extraction product is subjected to a second thermal conversion reaction to obtain a second thermal conversion product; In step (3), the conditions for the second thermal conversion reaction include: pressure of 0.5-5 MPa; temperature of 380-450℃; and time of 1-10h. (4) The second thermal conversion product and solvent II are subjected to a second extraction, and the resulting raffinate is subjected to a second distillation to obtain the intermediate phase pitch; The distillation range of the catalytic cracking slurry oil is 400-490℃.

2. The method according to claim 1, wherein, The distillation range of the catalytic cracking slurry oil is 20-50℃; the distillation range of the catalytic cracking slurry oil is 400-430℃, 430-460℃, and 460-490℃.

3. The method according to claim 2, wherein, The distillation range of the catalytic cracking slurry oil is 20-35℃; the distillation range of the catalytic cracking slurry oil is 430-460℃.

4. The method according to claim 1, wherein, The catalytic cracking slurry distillate is obtained by fractionation of the catalytic cracking slurry; the total heteroatom content in the catalytic cracking slurry is ≤3wt%; and the solid content is ≤20 mg / kg.

5. The method according to claim 4, wherein, The total heteroatom content in the catalytic cracking slurry is 0.1-1 wt%; the solid content is 1-10 mg / kg.

6. The method according to claim 1, wherein, The weight ratio of catalytic cracking slurry oil and aromatic compounds in the feedstock is 1:2-5.

7. The method according to claim 1, wherein, In step (1), the conditions for the first thermal conversion reaction include: temperature of 430-450℃; time of 3-5h; and pressure of 3-5 MPa.

8. The method according to claim 1, wherein, The weight ratio of the first thermal conversion product to solvent I is 1:1-5.

9. The method according to claim 8, wherein, The weight ratio of the first thermal conversion product to solvent I is 1:3-5.

10. The method according to claim 1, wherein, Solvent I is toluene.

11. The method according to claim 1, wherein, In step (2), the conditions for the first distillation include: temperature of 85-105℃; time of 1-3h; and absolute pressure of <20 kPa.

12. The method according to claim 11, wherein, In step (2), the conditions for the first distillation include: a temperature of 95-100℃; a time of 1.5-2.5h; and an absolute pressure of 7-8 kPa.

13. The method according to claim 1, wherein, In step (3), the conditions for the second thermal conversion reaction include: pressure of 1-3 MPa; temperature of 400-430℃; and time of 2-4h.

14. The method according to any one of claims 1-13, wherein, The weight ratio of the second thermal conversion product to solvent II is 1:1-3; In step (4), the temperature of the second extraction is 60-120℃; Solvent II is selected from at least one of toluene, furfural, n-heptane, and pyridine.

15. The method according to claim 14, wherein, The weight ratio of the second thermal conversion product to solvent II is 1:1.5-2.5; In step (4), the temperature of the second extraction is 80-100℃; Solvent II is a mixed solvent containing toluene and n-heptane.

16. The method according to any one of claims 1-13, wherein, The second distillation method is vacuum distillation; The conditions for vacuum distillation include: a cutting temperature of 500-530℃ and an absolute pressure of 0.1-0.3 mmHg.

17. The method according to claim 16, wherein, The conditions for vacuum distillation include: a cutting temperature of 515-525℃ and an absolute pressure of 0.15-0.25 mmHg.

18. Mesophase pitch prepared by the method of any one of claims 1-17.

19. The mesophase pitch according to claim 18, wherein, The mesophase pitch has a mesophase content ≥60wt%; a softening point of 260-310℃; a carbon content of 94.5-95.5wt%; and a hydrogen content of 4-4.5wt%. The mesophase morphology of the mesophase asphalt is selected from streamlined and / or spherical types.

20. The mesophase pitch according to claim 19, wherein, The mesophase asphalt has a mesophase content ≥80wt%; a softening point of 285-300℃; a carbon content of 94.5-95wt%; and a hydrogen content of 4.3-4.5wt%.

21. The use of the mesophase pitch according to any one of claims 18-20 in pitch-based carbon fibers.

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