Spinnable mesophase pitch and synthesis method

Abstract

The invention discloses spinnable mesophase pitch and a synthesis method, and belongs to the technical field of pitch, the synthesis method comprises the following steps: S1, uniformly mixing coal pitch, solvent oil and catalyst powder, and carrying out heat treatment under an inert atmosphere condition to prepare a first intermediate product; s2, cooling the first intermediate product, standing, carrying out settling separation, filtering upper-layer clarified oil after settling separation, and then carrying out reduced pressure distillation to obtain modified pitch; s3, carrying out heat treatment on the modified asphalt in an inert atmosphere to prepare thermal polycondensation asphalt; s4, crushing the thermal polycondensation asphalt, sieving the crushed thermal polycondensation asphalt with a 60-300-mesh sieve, adding an extracting agent for extraction, and filtering after the extraction is finished to obtain an insoluble substance which is a second intermediate product; and S5, carrying out vacuum drying on the second intermediate product, carrying out heat treatment under inert atmosphere and normal pressure conditions, and cooling after the heat treatment is finished, so as to obtain the mesophase pitch. The mesophase pitch with high anisotropic content and low softening point is prepared, the production process is simplified, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of asphalt technology, specifically relating to a spinnable mesophase asphalt and its synthesis method. Background Technology

[0002] In recent years, with the continuous development of new carbon material preparation technologies, high-performance pitch-based carbon fibers have been widely used in thermal management materials and C / C composite materials due to their high thermal conductivity, high modulus, high temperature resistance, and corrosion resistance. One of the key technological bottlenecks in the preparation of high-performance pitch-based carbon fibers is the preparation of high-quality spinnable mesophase pitch. This requires the mesophase pitch to have a high mesophase content, low softening point, and low heteroatom content, enabling continuous spinning over a wide spinnable temperature range. However, the main problem with current domestic mesophase pitch preparation technology is the contradiction between mesophase content and softening point: pitch with high mesophase content usually has a high softening point, resulting in poor fluidity during melt spinning and easy breakage or uneven fiber diameter; while lowering the softening point may introduce too many light components, affecting the orientation and mechanical properties of the final carbon fibers. Chinese patent CN118087095A discloses a high thermal conductivity mesophase pitch-based carbon fiber precursor and its preparation method, using petroleum residue oil as raw material to form a mesophase under mild conditions, and increasing the mesophase content through a N2 purging process. However, this method consumes a large amount of N2 and suffers from low mesophase yield. Chinese patent CN120059782A discloses a method for preparing spinnable mesophase pitch by catalytic hydrogenation modification of coal tar pitch in a suspended bed. The method involves uniformly mixing the raw materials and solvent, adding a catalyst, and heat-treating under initial hydrogen pressure to obtain the hydrogenated product. After purification, the spinnable mesophase pitch is obtained through thermal polycondensation and enrichment. This method requires ensuring the purity of the hydrogenated product before proceeding with the final thermal polycondensation treatment, and it demands high pressure and sophisticated production equipment. Therefore, current domestic mesophase pitch preparation processes still have significant shortcomings, requiring advanced equipment and making it difficult to reduce production costs.

[0003] Based on this, the present invention proposes a spinnable mesophase pitch and its synthesis method in order to solve the above problems. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a spinnable mesophase pitch and its synthesis method, thereby preparing mesophase pitch with high anisotropy content and low softening point, simplifying the production process, and reducing production costs.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for synthesizing spinnable mesophase pitch, comprising the following steps: S1. Coal tar pitch, solvent oil and catalyst powder are mixed evenly and heat-treated under an inert atmosphere to obtain the first intermediate product, wherein the reaction pressure is 0.5~3 MPa and the heat treatment temperature is 350~430℃. S2. After cooling the first intermediate product, add an aliphatic solvent and let it stand for sedimentation separation. Filter the clear oil in the upper layer after sedimentation separation, and then remove the solvent oil and aliphatic solvent by vacuum distillation to obtain modified asphalt. S3. The modified asphalt is heat-treated in an inert atmosphere to obtain thermally condensed asphalt. S4. Crush the thermally condensed asphalt, pass it through a 60-300 mesh sieve, add an extractant for extraction, filter after extraction to obtain insoluble matter, which is the second intermediate product. S5. After vacuum drying of the second intermediate product, heat treatment is carried out under an inert atmosphere and normal pressure at a temperature of 350~400℃. After heat treatment, the product is rapidly cooled to obtain mesophase pitch.

[0006] Preferably, in step S1, the mass ratio of coal tar pitch, solvent oil and catalyst powder is 100:(100~300):1~10.

[0007] Preferably, in step S1, the catalyst includes a catalytic component and a support, wherein the support is porous alumina, the catalytic component is Fe-S, and the mass of the catalytic component accounts for ≥5% of the mass of the support.

[0008] Preferably, in step S1, the solvent oil includes hydrogenated anthracene oil and / or hydrogenated wash oil.

[0009] Preferably, in step S1, the coal tar pitch is a type of pitch with a softening point of 30~110℃ obtained by distilling high-temperature coal tar.

[0010] Preferably, in step S2, the aliphatic solvent includes one or more of kerosene, naphtha, cyclohexane, and n-octane.

[0011] Preferably, in step S3, the specific steps for preparing thermopolymerized asphalt from modified asphalt are as follows: the modified asphalt is reacted in an inert atmosphere at 380~460℃ and 0.1~5 MPa. After the reaction is completed, the temperature is lowered to 350~380℃, and the reaction is continued under vacuum conditions to obtain thermopolymerized asphalt.

[0012] More preferably, in the first reaction of step S3, the temperature is 420~440℃ and the pressure is 1~1.5 MPa.

[0013] Preferably, in step S4, the thermally condensed asphalt is crushed and passed through a 60-100 mesh sieve, and the mass ratio of the thermally condensed asphalt to the extractant is 1:(5-50).

[0014] Preferably, in step S4, the extraction conditions are: temperature 20~80℃, time 1~6 h.

[0015] In a second aspect, the present invention provides a spinnable mesophase pitch, which is prepared by the above-described synthesis method.

[0016] Beneficial effects

[0017] This invention provides hydrogen via solvent oil, avoiding high-pressure reaction conditions and the use of flammable and explosive gases like hydrogen. This results in safer and milder production conditions. The innovative use of solvent oil as a hydrogen-providing feedstock also improves catalytic conditions, allowing for the use of more cost-effective catalysts. This invention synthesizes mesophase pitch with high anisotropy content and low softening point using simpler steps and lower reaction conditions, making it suitable for the industrial production of spinnable mesophase pitch. Detailed Implementation

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, specific implementation methods of the present invention will be described below with reference to the embodiments. Obviously, the following description is only some embodiments of the present invention. For those skilled in the art, other implementation methods can be obtained based on these embodiments without creative effort.

[0019] This invention proposes a method for synthesizing spinnable mesophase pitch, which synthesizes mesophase pitch with high anisotropy content and low softening point using relatively simple steps and lower reaction conditions. The specific steps are as follows: S1. Coal tar pitch, solvent oil and catalyst powder are mixed evenly and heat-treated under an inert atmosphere to obtain the first intermediate product, wherein the reaction pressure is 0.5~3 MPa and the heat treatment temperature is 350~430℃. S2. After cooling the first intermediate product, add an aliphatic solvent and let it stand for sedimentation separation. Filter the clear oil in the upper layer after sedimentation separation, and then remove the solvent oil and aliphatic solvent by vacuum distillation to obtain modified asphalt. S3. The modified asphalt is heat-treated in an inert atmosphere to obtain thermally condensed asphalt. S4. Crush the thermally condensed asphalt, pass it through a 60-300 mesh sieve, add an extractant for extraction, filter after extraction to obtain insoluble matter, which is the second intermediate product. S5. After vacuum drying of the second intermediate product, heat treatment is carried out under an inert atmosphere and normal pressure at a temperature of 350~400℃. After heat treatment, the product is rapidly cooled to obtain mesophase pitch.

[0020] In step S1, the preferred mass ratio of coal tar pitch, solvent oil and catalyst powder is 100:(100~300):1~10.

[0021] The main component of coal tar pitch is polycyclic aromatic hydrocarbons, and the solvent oil is a partially saturated polycyclic aromatic hydrocarbon. The mechanism of this invention is: during the heat treatment process, the solvent oil releases hydrogen free radicals, which are adsorbed by the active sites on the catalyst surface and transferred to the polycyclic aromatic hydrocarbons of coal tar pitch, so that cycloalkane structures are formed on the polycyclic aromatic hydrocarbons.

[0022] The preferred coal tar pitch is the pitch obtained by distilling high-temperature coal tar, and more preferably, coal tar pitch with a softening point of 30~110℃ is selected.

[0023] The solvent oil is preferably hydrogenated anthracene oil and / or hydrogenated wash oil, that is, the solvent oil can be hydrogenated anthracene oil, hydrogenated wash oil or a mixture of hydrogenated anthracene oil and hydrogenated wash oil, wherein the content of cycloalkane structure in the hydrogenated anthracene oil / hydrogenated wash oil is 30~60%.

[0024] The catalyst comprises a catalytic component and a support, wherein the support is porous alumina with a specific surface area of ​​180–300 m². 2 The catalyst has a pore size of 8-16 nm and is composed of Fe-S, accounting for 5-18% of the total catalyst mass. In this invention, the catalyst primarily functions as a carrier for hydrogen radical transfer. The catalyst of this invention is a conventional catalyst and can be prepared using conventional methods, such as co-precipitation or impregnation. This invention does not limit the methods used. For example, an aqueous solution of iron salts (ferric nitrate, ferric chloride, etc.) is prepared in a specific ratio, and the iron salts are impregnated onto the surface of alumina by equal volume impregnation. The alumina is then dried at 120°C for 12 h and calcined at 500°C for 2 h to form an iron oxide / alumina catalyst. The catalyst is then sulfided with a cyclohexane solution of CS2 to form a sulfur-iron catalyst.

[0025] Compared to conventional hydrogenation methods, this invention uses solvent oil to provide hydrogen, avoiding high-pressure reaction conditions and the use of flammable and explosive gases like hydrogen, resulting in safer and milder production conditions. Furthermore, the innovative use of solvent oil as a hydrogen-providing feedstock also improves catalytic conditions, allowing the use of more cost-effective catalysts.

[0026] In conventional catalytic hydrogenation processes, since hydrogen is derived from hydrogen gas, a molybdenum / tungsten-nickel / cobalt catalyst is needed to adsorb and activate the hydrogen. While these catalysts offer high hydrogenation activity, they are also expensive. Furthermore, in the hydrogenation of coal tar pitch, the catalyst is prone to coking and deactivation, resulting in high production costs for catalysts using molybdenum / tungsten-nickel / cobalt. This invention utilizes hydrogen free radicals released from the solvent oil at high temperatures as the hydrogen source. Therefore, it does not require a catalyst with excessively high hydrogenation activity. A low-cost Fe-S catalyst is used, and after hydrogenation, the catalyst settles along with the pitch and is directly discarded, eliminating the need for recycling. This approach is both cost-effective and simple.

[0027] In step S1, the heat treatment time is preferably 30 to 240 min. More preferably, the heat treatment reaction conditions are: a heat treatment temperature of 380 to 430°C and a heat treatment time of 30 to 60 min. Even more preferably, the heat treatment reaction conditions are: a heat treatment temperature of 410°C and a heat treatment time of 60 min.

[0028] In step S2, the addition of an aliphatic solvent is necessary. Its functions are: to reduce the viscosity of the system and promote the sedimentation of the catalyst powder; to reduce the solubility of the solvent oil, so that some of the heavy asphalt encapsulates the catalyst and settles together, thereby accelerating the sedimentation rate. Preferably, the solvent oil is different from the aliphatic solvent.

[0029] In step S2, the aliphatic solvent includes one or more of kerosene, naphtha, cyclohexane, and n-octane. The aliphatic solvent does not participate in the reaction, and its amount is determined according to actual production needs. Preferably, the mass ratio of aliphatic solvent to solvent oil is (0.5~2):1.

[0030] In step S2, the settling time is preferably ≥24 h, and more preferably 24~72 h. The specific operation of step S2 can be as follows: the first intermediate product is fed into a settling tank, cooled to room temperature and then settling for separation. The upper clarified oil is filtered and then fed into a distillation tower to remove the solvent oil by vacuum distillation to obtain modified asphalt.

[0031] In step S3, the specific steps for preparing thermopolymerized asphalt from modified asphalt are as follows: The modified asphalt is reacted in an inert atmosphere at 380–460°C and 0.1–5 MPa for a preferred reaction time of 1–30 h. After the reaction is complete, the temperature is lowered to 350–380°C, and the reaction continues under vacuum for a preferred time of 1 h, yielding thermopolymerized asphalt. The main purpose of reacting at 350–380°C under vacuum for 1 h is to remove light components generated during the thermopolymerization process, which is beneficial for the recovery of the extraction solvent in step S4. More preferably, in the first reaction, the temperature is 420–440°C, the reaction time is 3–9 h, and the pressure is 1–1.5 MPa.

[0032] In step S4, the thermally condensed asphalt is preferably crushed and passed through a 60-100 mesh sieve.

[0033] The extractant is preferably an aromatic solvent, including one or more of toluene, benzene, xylene, and tetrahydrofuran. The amount of extractant used depends on actual production. Preferably, the mass ratio of thermally condensed pitch to extractant is 1:(5~50), and more preferably, the mass ratio is 1:(5~10).

[0034] In step S4, the preferred extraction conditions are: temperature 20~80℃ and time 1~6 h. More preferably, the extraction temperature is 20~50℃ and the extraction time is 2~5 h.

[0035] In step S5, the vacuum drying temperature is set so as not to affect the second intermediate product. Preferably, the vacuum drying temperature is 60-180°C.

[0036] In this invention, an inert atmosphere refers to an atmosphere that does not react with raw materials or solvents, such as inert gases or nitrogen.

[0037] The technical solution of the present invention will be described in detail below with specific embodiments.

[0038] Example 1

[0039] S1. Coal tar pitch, hydrogenated anthracene oil, and catalyst powder are mixed uniformly at a mass ratio of 100:150:10, and heat-treated at 1 MPa, 410℃, and nitrogen atmosphere for 1 h to obtain the first intermediate product. The catalyst has a specific surface area of ​​210 m². 2 / g, Fe-S catalyst supported on porous alumina with a pore size of 12nm, with Fe-S accounting for 12% of the total catalyst mass; S2. After cooling the first intermediate product to room temperature, add kerosene equal to 50% of the mass of hydrogenated anthracene oil, stir well, and let stand for 48 hours for sedimentation separation. Filter the clear upper layer of oil after sedimentation separation, and then remove the hydrogenated anthracene oil and kerosene by vacuum distillation to obtain modified pitch; S3. The modified asphalt was heat-treated at 430℃ and 1MPa in a nitrogen atmosphere for 6 hours. After the reaction was completed, the temperature was lowered to 380℃ and the reaction was continued under vacuum for 1 hour to obtain thermally condensed asphalt. S4. The thermally condensed asphalt is crushed, passed through a 60-mesh sieve, and then 10 times its weight of toluene is added for extraction. The extraction temperature is 50℃ and the extraction time is 3h. After the extraction is completed, the mixture is filtered to obtain the insoluble matter, which is the second intermediate product. S5. After vacuum drying the second intermediate product at 80°C, heat-treat it at 380°C for 30 minutes in a nitrogen atmosphere. After the heat treatment, cool it down rapidly to obtain mesophase pitch.

[0040] The mesophase pitch prepared in this embodiment has a softening point of 295℃ and a mesophase content of >95 vol%. It was evaluated by a single-hole spinning machine and the length of the single filament is greater than 10,000 meters. The thermal conductivity of the pitch fiber after graphitization is 801 W / m·K.

[0041] Example 2

[0042] S1. Coal tar pitch, hydrogenated anthracene oil, and catalyst powder are mixed uniformly at a mass ratio of 100:100:10, and heat-treated at 1 MPa, 390℃, and nitrogen atmosphere for 2 hours to obtain the first intermediate product; wherein, the catalyst has a specific surface area of ​​230 m². 2 / g, Fe-S catalyst supported on porous alumina with a pore size of 8nm, with Fe-S accounting for 8% of the total catalyst mass; S2. After cooling the first intermediate product to room temperature, add an equal mass of hydrogenated anthracene oil and cyclohexane, stir evenly, and let stand for 48 hours for sedimentation separation. Filter the clear upper layer of oil after sedimentation separation, and then remove the hydrogenated anthracene oil and cyclohexane by vacuum distillation to obtain modified asphalt. S3. The modified asphalt was heat-treated at 430℃ and 1MPa in a nitrogen atmosphere for 8 hours. After the reaction was completed, the temperature was lowered to 360℃ and the reaction was continued under vacuum for 1 hour to obtain thermally condensed asphalt. S4. The thermally condensed asphalt is crushed, passed through a 60-mesh sieve, and then extracted with 5 times its mass of toluene at a temperature of 50°C for 3 hours. After extraction, it is filtered to obtain an insoluble substance, which is the second intermediate product. S5. After vacuum drying the second intermediate product at 80°C, heat-treat it at 350°C for 30 minutes in a nitrogen atmosphere. After the heat treatment, cool it down rapidly to obtain mesophase pitch.

[0043] The mesophase pitch prepared in this embodiment has a softening point of 288℃ and a mesophase content of >90 vol%. It was evaluated by a single-hole spinning machine and the length of the single filament is greater than 10,000 meters. The thermal conductivity of the pitch fiber after graphitization is 752 W / m·K.

[0044] Comparative Example 1

[0045] No catalyst was used in this comparative example.

[0046] S1. Coal tar pitch and hydrogenated anthracene oil are mixed evenly at a mass ratio of 100:150 and heat-treated at 1 MPa, 410℃ and nitrogen atmosphere for 1 h to obtain the first intermediate product. S2. After cooling the first intermediate product to room temperature, add kerosene equal to 50% of the mass of hydrogenated anthracene oil, stir evenly, and let stand for 48 hours for sedimentation separation. Filter the clear upper layer of oil after sedimentation separation, and then remove the hydrogenated anthracene oil and kerosene by vacuum distillation to obtain modified asphalt. S3. The modified asphalt was heat-treated at 430℃ and 1MPa in a nitrogen atmosphere for 6 hours. After the reaction was completed, the temperature was lowered to 380℃ and the reaction was continued under vacuum for 1 hour to obtain thermally condensed asphalt. S4. The thermally condensed asphalt is crushed, passed through a 60-mesh sieve, and then 10 times its weight of toluene is added for extraction. The extraction temperature is 50℃ and the extraction time is 3h. After the extraction is completed, the mixture is filtered to obtain the insoluble matter, which is the second intermediate product. S5. After vacuum drying the second intermediate product at 80°C, heat-treat it at 380°C for 30 minutes in a nitrogen atmosphere. After the heat treatment, cool it down rapidly to obtain mesophase pitch.

[0047] The mesophase pitch prepared in this comparative example has a softening point of 308℃ and a mesophase content >95 vol%. Evaluation using a single-hole spinning machine showed that the monofilament length was less than 2000 meters, and the thermal conductivity of the pitch fiber after graphitization was 622 W / m·K. Compared to Examples 1-2, the monofilament length in this comparative example was significantly reduced, and the thermal conductivity also decreased markedly.

[0048] Comparative Example 2

[0049] This comparative example does not use hydrogenated anthracene oil, but rather anthracene oil.

[0050] S1. Coal tar pitch, anthracene oil, and catalyst powder are mixed uniformly at a mass ratio of 100:150:10, and heat-treated at 1 MPa, 410℃, and nitrogen atmosphere for 1 h to obtain the first intermediate product. The catalyst has a specific surface area of ​​210 m². 2 / g, Fe-S catalyst supported on porous alumina with a pore size of 12nm, with Fe-S accounting for 12% of the total catalyst mass; S2. After cooling the first intermediate product to room temperature, add kerosene equal to 50% of the mass of anthracene oil, stir evenly, and let stand for 48 hours for sedimentation separation. Filter the clear upper layer of oil after sedimentation separation, and then remove the anthracene oil and kerosene by vacuum distillation to obtain modified pitch. S3. The modified asphalt was heat-treated at 430℃ and 1MPa in a nitrogen atmosphere for 6 hours. After the reaction was completed, the temperature was lowered to 380℃ and the reaction was continued under vacuum for 1 hour to obtain thermally condensed asphalt. S4. The thermally condensed asphalt is crushed, passed through a 60-mesh sieve, and then 10 times its weight of toluene is added for extraction. The extraction temperature is 50℃ and the extraction time is 3h. After the extraction is completed, the mixture is filtered to obtain the insoluble matter, which is the second intermediate product. S5. After vacuum drying the second intermediate product at 80°C, heat-treat it at 380°C for 30 minutes in a nitrogen atmosphere. After the heat treatment, cool it down rapidly to obtain mesophase pitch.

[0051] The mesophase pitch prepared in this comparative example has a softening point of 320℃ and a mesophase content >95 vol%. Evaluation using a single-hole spinning machine showed that the monofilament length was less than 1000 meters, and the thermal conductivity of the pitch fiber after graphitization was 499 W / m·K. Compared to Examples 1-2, the monofilament length in this comparative example is shorter, and the thermal conductivity is significantly reduced.

[0052] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for synthesizing spinnable mesophase pitch, characterized in that, Includes the following steps: S1. Coal tar pitch, solvent oil and catalyst powder are mixed evenly and heat-treated under an inert atmosphere to obtain the first intermediate product, wherein the reaction pressure is 0.5~3 MPa and the heat treatment temperature is 350~430℃. S2. After cooling the first intermediate product, add an aliphatic solvent and let it stand for sedimentation separation. Filter the clear oil in the upper layer after sedimentation separation, and then remove the solvent oil and aliphatic solvent by vacuum distillation to obtain modified asphalt. S3. The modified asphalt is heat-treated in an inert atmosphere to obtain thermally condensed asphalt. S4. Crush the thermally condensed asphalt, pass it through a 60-300 mesh sieve, add an extractant for extraction, filter after extraction to obtain insoluble matter, which is the second intermediate product. S5. After vacuum drying of the second intermediate product, heat treatment is carried out under inert atmosphere and normal pressure. The heat treatment temperature is 350~400℃ and the heat treatment time is 0.1~2 h. After the heat treatment is completed, the temperature is lowered to obtain mesophase asphalt.

2. The synthesis method according to claim 1, characterized in that, In step S1, the mass ratio of coal tar pitch, solvent oil and catalyst powder is 100:(100~300):1~10.

3. The synthesis method according to claim 1, characterized in that, In step S1, the catalyst includes a catalytic component and a support, wherein the support is porous alumina, the catalytic component is Fe-S, and the mass of the catalytic component accounts for 5-18% of the total mass of the catalyst.

4. The synthesis method according to claim 1, characterized in that, In step S1, the solvent oil includes hydrogenated anthracene oil and / or hydrogenated wash oil.

5. The synthesis method according to claim 1, characterized in that, In step S1, the coal tar pitch is a type of pitch with a softening point of 30~110℃ obtained by distilling high-temperature coal tar.

6. The synthesis method according to claim 1, characterized in that, In step S2, the aliphatic solvent includes one or more of kerosene, naphtha, cyclohexane, and n-octane.

7. The synthesis method according to claim 1, characterized in that, In step S3, the steps for preparing thermopolymerized asphalt from modified asphalt are as follows: the modified asphalt is reacted in an inert atmosphere at 380~460℃ and 0.1~5 MPa. After the reaction is completed, the temperature is lowered to 350~380℃, and the reaction is continued under vacuum to obtain thermopolymerized asphalt.

8. The synthesis method according to claim 1, characterized in that, In step S4, the thermally condensed asphalt is crushed and passed through a 60-100 mesh sieve, and the mass ratio of the thermally condensed asphalt to the extractant is 1:(5-50).

9. The synthesis method according to claim 1, characterized in that, In step S4, the extraction conditions are: temperature 20~80℃, time 1~6 h.

10. A spinnable mesophase pitch, characterized in that, It is prepared by the synthesis method according to any one of claims 1-9.