Method for the preparation of mesophase pitch by joule heating

Abstract

The present application relates to mesophase pitch preparation field, disclose a kind of method for preparing mesophase pitch by joule heating, the method comprises: the heating treatment of pitch raw material by joule, cooling, obtain mesophase pitch;Wherein, the temperature of heating is 3600-3700 ℃.The method has the characteristics of high heating efficiency, short heating time, can quickly remove volatile substances in pitch raw material, quickly obtain mesophase pitch, the whole process of operation is economic, environmental protection, green and low carbon.

Description

Technical Field

[0001] This invention relates to the field of mesophase pitch preparation, and more specifically to a method for preparing mesophase pitch by Joule heating. Background Technology

[0002] Mesophase pitch, especially foamed carbon and carbon fiber matrices with irregular 3D pore structures, is commonly used as a catalyst support to prepare "uncoated" catalysts. These catalysts feature large diffusion paths, large geometric areas, and high porosity. Combined with the excellent properties of carbon matrix, such as high thermal conductivity, high strength, high modulus, high temperature resistance, corrosion resistance, and impact resistance, they offer advantages in eliminating radial diffusion limitations, enhancing mass / heat transfer through eddy mixing, and improving catalytic lifetime. This has led to a series of advancements in energy catalysis, chemical production, and electrochemical energy storage. Using petroleum-based carbon materials as a matrix to reconstruct the macroscopic structure of the catalyst and achieve efficient coupling with the reactor improves the efficiency of the catalytic reaction process, fulfilling the principle of "oil-based" catalysts while simultaneously serving new energy sources. Therefore, the preparation of mesophase pitch is crucial for the research and development of "uncoated" catalyst preparation technology using foamed carbon and carbon fiber matrices.

[0003] There are six main conventional methods for preparing mesophase pitch: one-step thermal polycondensation, new mesophase method, potential mesophase method, pre-mesophase method, and catalytic modification method. The typical one-step thermal polycondensation method involves polycondensation at 400℃ under inert gas protection with mechanical stirring, held at this temperature for 2–17 hours. The UCC method involves two heat treatments: the first at 420℃ for 1–5 hours, and the second at 390℃ for 6 hours. While the new mesophase method reduces the heat treatment time to less than 10 minutes, it requires the use of benzene or toluene as a solvent for solvent separation of the raw materials, making the process complex. The potential mesophase method and the mesophase method add hydrogenation treatment to the UCC method, further complicating the process and extending the reaction time. The catalytic modification method adds catalytic modification, washing, and vacuum drying to the thermal polycondensation process, making the process more complex, with a polycondensation time of 15 hours.

[0004] Although many new methods for preparing mesophase asphalt have been proposed for complex and low-quality raw materials, the processes are generally complex, and the heat treatment or thermal polycondensation reaction times are very long. For example, CN117983167A requires a reflux reaction at 200-500℃ for 1-8 hours; CN118048167A requires a bromine substitution reaction at 0-60℃ for 4-10 hours, a debromination reaction at 210-250℃ at 1-5 MPa for 6-12 hours, and a thermal polycondensation reaction at 380-420℃ for 3-12 hours; CN117778048A requires a temperature of 400-450℃, a reaction pressure of 2-6 MPa, a stirring speed of 100-300 r / min, and a reaction time of 5-15 hours. Therefore, existing methods for preparing mesophase asphalt involve thermal reaction processes, which are time-consuming, have low thermal efficiency, and consume a lot of energy. In conclusion, there is an urgent need to develop a method for preparing mesophase pitch that can improve thermal efficiency.

[0005] In recent years, in response to the call for energy conservation, various high-efficiency heating technologies have emerged, such as the Joule thermoelectric flash evaporation method. Compared with traditional catalyst and support preparation techniques, the Joule thermoelectric flash evaporation method can achieve rapid heating and cooling, and is energy-saving, environmentally friendly, highly efficient, and easy to operate.

[0006] CN117127211A discloses a method for preparing single-atom platinum catalysts through flash Joule heat treatment. This method yields single-atom platinum catalysts confined within carbon nanotubes, exhibiting higher efficiency than traditional catalyst calcination methods, while also being environmentally friendly and simple to implement. CN117821995A discloses a method for rapidly synthesizing heterostructure electrocatalysts using Joule heat treatment. By activating carbon cloth with Joule heat, the instantaneous high temperature enhances the adhesion of the carbon cloth substrate to the precursor, while preventing catalyst agglomeration. Highly dispersed nanoscale heterostructure electrocatalysts can be obtained within a very short processing time. This technology features a simple and efficient synthesis process, facilitating mass production. CN118139225A discloses a method for efficiently and rapidly transforming rubber and organic materials into high-value-added products using Joule heat treatment. In order to effectively extend the self-conductivity time of volatile powder materials during the heating process, this technology provides a device and method for heating volatile powders using Joule heating, which has significant advantages, especially for volatile powders that are continuously filmed before treatment and still adhere to or are close to the heat source after heat treatment.

[0007] Therefore, exploring the application of Joule thermal flash evaporation in the preparation of mesophase pitch is of great practical significance. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of low thermal efficiency, excessively long reaction time, and complex process in the preparation of mesophase asphalt in the existing technology, and to provide a method for preparing mesophase asphalt by Joule heating. This method has high thermal efficiency, short reaction time, and can meet the requirements of being economical, environmentally friendly, green and low-carbon.

[0009] To achieve the above objectives, the present invention provides a method for preparing mesophase asphalt by Joule heating, the method comprising: subjecting dried asphalt raw material to Joule heating treatment, cooling down, and obtaining mesophase asphalt; wherein the heating temperature is 3600-3700℃.

[0010] Compared with the prior art, the technical solution of the present invention has the following characteristics: (1) It has the characteristics of high heating efficiency and short heating time, which makes it easy to achieve batch production; (2) Due to the extremely fast heating and cooling rate of the process, the thermal reaction also occurs very quickly, which promotes the structural change of some thermal polycondensation and forms a microcrystalline structure, which is conducive to the rapid transformation into mesophase asphalt; (3) Due to the extremely fast thermal polycondensation rate, this method can avoid excessive polymerization of thermal reaction and can also quickly remove volatile substances, so as to quickly obtain mesophase asphalt.

[0011] In addition, this synthesis method is energy-saving, environmentally friendly, highly efficient, and simple to operate. Attached Figure Description

[0012] Figure 1 The graph shows the change of voltage over time in the high-temperature flash evaporation experiment of raw material 1.

[0013] Figure 2 The graph shows the change of current over time in the high-temperature flash evaporation experiment of raw material 1.

[0014] Figure 3 The graph shows the temperature change over time in the high-temperature flash evaporation experiment of raw material 1.

[0015] Figure 4 Raw material 1 (lumpy raw material) is transformed into powder product 1 after high-temperature flash evaporation.

[0016] Figure 5 This is a comparison chart of the XRD patterns of product 1 and raw material 1.

[0017] Figure 6 The infrared spectrum of product 1.

[0018] Figure 7 The results are the TEM test results for product 1.

[0019] Figure 8 The graph shows the change of voltage over time in the high-temperature flash evaporation experiment of raw material 2.

[0020] Figure 9 The graph shows the change of current over time in the high-temperature flash evaporation experiment of raw material 2.

[0021] Figure 10 The graph shows the temperature change over time in the high-temperature flash evaporation experiment of raw material 2.

[0022] Figure 11 Raw material 2 (block raw material) is transformed into powder product 2 after high-temperature flash evaporation.

[0023] Figure 12 This is a comparison chart of the XRD patterns of product 2 and raw material 2.

[0024] Figure 13 The infrared spectrum of product 2.

[0025] Figure 14 The results are the TEM test results for product 2.

[0026] Figure 15 The graph shows the change of voltage over time in the high-temperature flash evaporation experiment of raw material 3.

[0027] Figure 16 The graph shows the change of current over time in the high-temperature flash evaporation experiment of raw material 3.

[0028] Figure 17 The graph shows the temperature change over time in the high-temperature flash evaporation experiment of raw material 3.

[0029] Figure 18 Raw material 3 (lumpy raw material) is flash-evaporated at high temperature to form larger block products 3.

[0030] Figure 19 This is a comparison chart of the XRD patterns of product 3 and raw material 3.

[0031] Figure 20 The infrared spectrum of product 3.

[0032] Figure 21 The results are the TEM test results for product 3.

[0033] Figure 22 This is a comparison chart of the XRD patterns of product 4 and raw material 4.

[0034] Figure 23 This is a comparison chart of the XRD patterns of product 3' and product 3.

[0035] Figure 24 This is a comparison chart of the infrared results of product 3' and product 3.

[0036] Figure 25 The image shows an XRD comparison of product 4' and raw material 4. Detailed Implementation

[0037] 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.

[0038] This invention provides a method for preparing mesophase asphalt by Joule heating, the method comprising: subjecting dried asphalt raw material to Joule heating treatment, cooling down, and obtaining mesophase asphalt.

[0039] The method described in this invention uses instantaneous Joule heating to flash-evaporate asphalt raw materials, which enables the asphalt raw materials to be rapidly heated and undergo a condensation reaction. The light components are quickly evaporated under the action of heat, thereby obtaining mesophase asphalt; wherein, the heating temperature is 3600-3700℃.

[0040] In this invention, there are no special requirements for the reaction system used in the specific implementation of the method. For example, the reaction system may include a reaction chamber connected to a vacuum pump. After purging the reaction system with nitrogen before and after the reaction, the reaction is started by pumping the system to a certain vacuum level or in an inert atmosphere. A quartz glass reaction tube is placed in the reaction chamber to hold the heating material. The reaction system may be connected to a buffer tank to collect the light components generated by the condensation of thermal decomposition and the volatile substances generated by physical heating.

[0041] In this invention, there are no special requirements for the heating power of Joule heating. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the heating power of Joule heating is 30-70W. The aforementioned technical solution features high heating efficiency and short heating time, which is beneficial for rapid conversion into mesophase pitch. It also offers advantages such as simple operation, environmental friendliness, and ease of mass production.

[0042] In this invention, there are no special requirements for the constant voltage of Joule heating. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the constant voltage of Joule heating is 6-200V.

[0043] In this invention, there are no special requirements for the Joule heating time. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the Joule heating time is 0.1-5 seconds. The aforementioned technical solution enables an ultra-fast thermal polycondensation reaction, which is beneficial for the rapid transformation into mesophase pitch.

[0044] In this invention, there are no special requirements for the number of Joule heating cycles. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the number of Joule heating cycles is 1-3.

[0045] In this invention, there are no special requirements for the heating interval of Joule heating. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the heating interval of Joule heating is 10-20 seconds.

[0046] In this invention, there are no special requirements for the Joule heating method. According to a preferred embodiment of the invention, the Joule heating method is pulse heating, and more preferably, capacitor pulse discharge Joule heating. Using the aforementioned technical solution, instantaneous, rapid, and efficient heating of the reaction can be achieved.

[0047] In this invention, the pulse time of the capacitor pulse discharge Joule heating can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the pulse time of the capacitor pulse discharge Joule heating is 0.2-0.5s.

[0048] In this invention, the current intensity of the capacitor pulse discharge Joule heating can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the current intensity of the capacitor pulse discharge Joule heating is 0.01-400A.

[0049] In this invention, the range of types of asphalt raw materials that can be selected is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the asphalt raw material is selected from coal tar pitch and / or coal liquefaction pitch.

[0050] The method described in this invention can process both lumpy and powdered coal tar pitch. There are no special requirements regarding the size of the coal tar pitch; the following is an illustrative description but does not limit the scope of the invention. According to a preferred embodiment of the invention, the size of the coal tar pitch in any dimension does not exceed 1.5 cm, preferably 0.1-1.5 cm. If powdered pitch raw materials are required, the lumpy raw materials can be pulverized. For example, the lumpy raw materials can be crushed and ground using an air jet mill for 0.2-0.5 hours, followed by sieving. The resulting powdered raw materials have average particle sizes of 400 μm, 600 μm, and 800 μm.

[0051] In this invention, the heat treatment can be performed under vacuum conditions or in an inert gas atmosphere. Specifically, for example, the operating system can be evacuated for 2-4 hours before preparation begins, and then slowly filled with inert gas.

[0052] In this invention, the range of types of inert gas that can be selected is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the inert gas is selected from one or more of nitrogen, helium and argon.

[0053] In this invention, the heating treatment can be direct heating or indirect heating, preferably indirect heating.

[0054] In this invention, the direct heating involves heating the asphalt raw material by mixing it with a conductive medium. The range of types of conductive medium is quite wide; the following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the conductive medium is selected from one or more of carbon black, carbon nanotubes, and graphene. In direct heating, the asphalt raw material can be pre-treated and crushed into micron-sized powder to increase the efficiency of direct heating. By doping with a certain proportion of conductive medium, direct Joule flash evaporation is performed. The powdered raw material is rapidly heated and undergoes a thermal condensation reaction, quickly generating microcrystals, and then rapidly transforming into mesophase asphalt. The particle size is related to the rate of thermal condensation reaction and the degree of crystallization.

[0055] In this invention, there are no special requirements for the resistance value of the conductive medium. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the resistance value of the conductive medium is 1-30Ω. Using the aforementioned technical solution, the reaction thermal field can be made more uniform, the heating efficiency higher, and the product performance better.

[0056] According to a preferred embodiment of the present invention, the amount of the conductive medium added is 5-20 wt% of the asphalt raw material. Using the aforementioned technical solution, the heating system can be started quickly, while simultaneously making the thermal reaction more uniform.

[0057] In this invention, the resistance value of the heated material can be adjusted by controlling the amount of conductive medium added. For example, according to the experimental results of this invention, adding 10 wt% carbon black to coal tar pitch can make the resistance value of the heated material (including raw materials and conductive medium) 25 Ω, adding 15 wt% carbon black can make the resistance value of the heated material 9 Ω, and adding 8 wt% carbon black can make the resistance value of the heated material 1 Ω.

[0058] According to a preferred embodiment of the present invention, the indirect heating is performed by wrapping the asphalt raw material with graphite paper and / or graphite felt for heating. Indirect heating involves rapidly flashing the blocky raw material with graphite paper and / or graphite felt, allowing the blocky raw material to be rapidly heated and then directly thermally broken into a large number of fine powder particles. Under the action of heat, the fine powder particles rapidly undergo thermal condensation reaction, resulting in extremely fast crystallization or crystal transformation, while allowing volatile components to escape rapidly through rapid heating.

[0059] In this invention, as long as the drying purpose can be achieved, there are no special requirements for the specific drying method and conditions. For example, drying can be carried out in an oven at a temperature of 40-60°C for 2-4 hours.

[0060] In this invention, the cooling process requires no special operation. After heating is stopped, the reactants will cool down rapidly, and the material can be removed after about 30 seconds.

[0061] The mesophase pitch prepared by this invention can be used as an excellent precursor for preparing high-performance carbon materials such as catalyst carriers, carbon fibers, foamed carbon, C / C composite materials, high thermal conductivity carbon, and carbon electrodes. Among them, carbon fibers have unique properties such as high thermal conductivity, high electrical conductivity, high strength, high modulus, high temperature resistance, corrosion resistance, impact resistance, and a thermal expansion coefficient close to zero, and can be used in aircraft material manufacturing and track design.

[0062] The present invention will be described in detail below through embodiments.

[0063] In the following embodiments,

[0064] The Joule heat flash evaporation equipment was manufactured by Taiyuan Saiyin New Material Technology Co., Ltd., model number FJH-2024A;

[0065] XRD analysis was performed using a Bruker D8 Advance A25 X-ray XRD system. Test conditions: Cu target Kα radiation, X-ray wavelength 0.154 nm, tube voltage 40 kV, tube current 100 mA, scan speed 5.0° / min.

[0066] Infrared testing was conducted using Bruker's technology. The FT-IR spectrometer uses powder samples in attenuated total reflection mode.

[0067] TEM analysis was performed using a JEM-F200(URP) dual-energy spectrometer from Nippon Electronics Co., Ltd. TEM: 0.10nm@200kV, 0.14nm@80kV; Total detector area: 200mm². 2 ;

[0068] The weight loss rate is the ratio of the difference between the weight of raw materials and the weight of the product to the weight of the raw materials. Under the same experimental conditions, the higher the weight loss rate, the higher the volatile substances produced by the thermal reaction, which can also qualitatively indicate that the proportion of raw materials participating in the thermal reaction is higher.

[0069] In the following embodiments,

[0070] The superior grade of coal tar pitch has a particle size of 0.1-1.0 cm and an ash content of ≤0.1%.

[0071] Grade I coal tar pitch has a particle size of 0.2-1.2 cm and an ash content of ≤0.6%.

[0072] The qualified product of coal tar pitch has a particle size of 0.5-1.5cm and an ash content of ≤25.0%.

[0073]

Example 1

[0074] Take an appropriate amount of raw material 1 (superior grade coal tar pitch) and place it in a vacuum drying oven for drying and dehydration at 50℃ for 2 hours. After drying, wrap it in graphite paper and place it in a quartz glass reaction tube. Place the quartz glass reaction tube in a reaction chamber connected to a vacuum pump and evacuate for 2 hours until the vacuum level reaches 0.01MPa. Turn on the Joule heat flash evaporation equipment, set the heating power to 70W, voltage to 180V, current to 255A, and pulse time to 0.5s, so that the heating temperature instantly rises to 3600℃. Then the equipment automatically stops heating, and the reactants cool down rapidly. After 30 seconds, remove the product and record it as product 1. Collect and weigh the product. Compared with raw material 1, product 1 has a weight loss rate of approximately 29%, and the material changes from lumps to powder. See [link to product description]. Figure 4 For specific Joule heating experimental conditions, please refer to [link / reference]. Figure 1-3 The entire reaction system is connected to a buffer tank to collect the light components produced by thermal decomposition and the volatile substances produced by physical heating.

[0075] XRD tests were performed on the raw materials and products of this embodiment, and infrared and TEM tests were performed on the products. The obtained XRD spectra, infrared spectra, and TEM images are shown below. Figure 5 , Figure 6 and Figure 7 As shown. From Figure 5 It can be seen that when the diffraction angle is approximately 25°, product 1 obtained from raw material 1 through high-temperature instantaneous electro-flash evaporation will exhibit diffraction peaks, indicating that the thermal reaction promotes the formation of a crystalline structure, possessing an mesophase pitch structure. Infrared spectroscopy can qualitatively analyze the functional group types of mesophase pitch. The molecular skeleton of mesophase pitch is mainly composed of polycyclic aromatic hydrocarbons, which have relatively high molecular rigidity. The presence of saturated groups such as methyl, methylene side chains, and cycloalkane structures can increase the toughness of polycyclic aromatic hydrocarbon molecules. Figure 6 It can be seen that the absorption peak range of polycyclic aromatic hydrocarbons in mesophase pitch is 700–900 cm⁻¹.-1 Absorption peak at 870 cm⁻¹ -1 Belongs to the isolated aromatic out-of-plane C-H vibration, 3050 cm -1 The nearby absorption peaks represent the C-H bond stretching vibrations of the aromatic ring, indicating that product 1 obtained by instantaneous electro-flash evaporation contains functional groups typical of mesophase pitch. TEM test results... Figure 7 This indicates that the structure of product 1 contains a typical crystal lattice structure. Figure 7 a), and also includes amorphous structures ( Figure 7 b) conforms to the structural composition of mesophase pitch. In summary, mesophase pitch can be obtained from raw material 1 through instantaneous high-temperature electric flash evaporation.

[0076]

Example 2

[0077] The method is the same as in Example 1, except that raw material 2 is grade I coal tar pitch. It is heated twice with a 10-second interval between heating cycles. After cooling, the material is collected and recorded as product 2, and weighed. Compared to raw material 2, product 2 has a weight loss rate of approximately 30%, and the product changes from a blocky state to a powdery state. (See...) Figure 11 For specific Joule heating experimental conditions, please refer to [link / reference]. Figure 8-10 .

[0078] XRD tests were performed on the raw materials and products of this embodiment, and infrared and TEM tests were performed on the products. The obtained XRD spectra, infrared spectra, and TEM images are shown below. Figure 12 , Figure 13 and Figure 14 As shown. From Figure 8 It can be seen that when the diffraction angle is approximately 25°, product 2 obtained from raw material 2 through high-temperature instantaneous electric flash evaporation will exhibit diffraction peaks, indicating that the thermal reaction promotes the formation of a crystalline structure, possessing an intermediate phase pitch structure. From Figure 9 Analysis shows that in the range of 700-900cm –1 The presence of strong absorption peaks within the range indicates that product 2, obtained from raw material 2 after high-temperature flash evaporation, contains a large amount of polycyclic aromatic hydrocarbons, and also shows strong absorption peaks at 3050 cm⁻¹. –1 The nearby absorption peaks also indicate the presence of the aromatic ring, and at the same time, in the range of 1300–1450 cm⁻¹ –1 and 2800~3000cm –1 The presence of typical absorption peaks within the range indicates the presence of saturated methyl and methylene groups. Therefore, product 2 obtained by instantaneous electro-flash evaporation contains typical functional groups of mesophase pitch. Furthermore, through... Figure 14 It can be seen that the structure of product 2 contains a typical crystal lattice structure. Figure 14 a), and also includes amorphous structures ( Figure 14 b) conforms to the structural composition of mesophase pitch. In summary, mesophase pitch can be obtained from raw material 2 through instantaneous high-temperature electro-flash evaporation.

[0079]

Example 3

[0080] The method is the same as in Example 1, except that raw material 3 is a qualified coal tar pitch product. It is heated three times with a 15-second interval between heating cycles. After cooling, the material is collected and recorded as product 3, and weighed. Compared to raw material 3, product 3 has a weight loss rate of approximately 35%. Furthermore, the product agglomerates from lumps into larger lumps. See details... Figure 18 For specific Joule heating experimental conditions, please refer to [link / reference]. Figure 15-17 The entire reaction system is connected to a buffer tank to collect the light components produced by thermal decomposition and the volatile substances produced by physical heating.

[0081] XRD tests were performed on the raw materials and products of this embodiment, and infrared and TEM tests were performed on the products. The obtained XRD spectra, infrared spectra, and TEM images are shown below. Figure 19 , Figure 20 and Figure 21 As shown. From Figure 19 It can be seen that when the diffraction angle is approximately 25°, product 3 obtained from raw material 3 through high-temperature instantaneous electro-flash evaporation will exhibit diffraction peaks, indicating that the thermal reaction promotes the formation of a crystalline structure with an intermediate phase pitch structure. However, because the specifications of raw material 3 are completely different from those of raw materials 2 and 3, many impurity peaks will appear in the XRD pattern. From Figure 20 Analysis shows that product 3 obtained from raw material 3 after high-temperature flash evaporation is at a temperature of 700-900 cm⁻¹. –1 The presence of strong absorption peaks within the range indicates that the raw material contains a large amount of polycyclic aromatic hydrocarbons, with a peak at 3050 cm⁻¹. –1 The nearby absorption peaks also indicate the presence of an aromatic ring. Additionally, the absorption peaks at 1300–1450 cm⁻¹ and 2800–3000 cm⁻¹ further confirm the presence of an aromatic ring. –1 The presence of typical absorption peaks within the range indicates the presence of saturated methyl and methylene groups, suggesting that the product obtained from raw material 3 after high-temperature flash evaporation contains typical functional group structures of polycyclic aromatic hydrocarbons and saturated groups found in mesophase pitch. Furthermore, through... Figure 21 It can be seen that the product contains a typical crystal lattice structure. Figure 21 a), and also includes amorphous structures ( Figure 21 b) conforms to the structural composition of mesophase pitch. In summary, mesophase pitch can be obtained from raw material 3 through instantaneous high-temperature electro-flash evaporation.

[0082]

Example 4

[0083] Raw material 4 (superior grade coal tar pitch) was placed in a vacuum drying oven for drying and dehydration at 50℃ for 2 hours. It was then pulverized and ground to obtain a powder with an average particle size of 800μm. Carbon black (8wt% of the raw material, resulting in a total resistivity of 1Ω) was added to the powder and mixed thoroughly. The mixture was then placed in a quartz glass reaction tube. The quartz glass reaction tube was placed in a reaction chamber connected to a vacuum pump, and a vacuum was applied for 2 hours until the vacuum level reached 0.01MPa. The Joule flash evaporation equipment was turned on, with the heating power set to 68W, voltage 188V, current 254A, and pulse time 0.5s, instantly raising the temperature to 3650℃. The equipment then automatically stopped heating, and the reactants rapidly cooled. After 30 seconds, the product was removed and recorded as product 4. The product was collected and weighed; compared to raw material 4, product 4 showed a weight loss of approximately 25%.

[0084] The XRD patterns of raw material 4 and product 4 are as follows: Figure 22 As shown, the infrared spectrum and TEM image of product 4 are compared with those of product 4. Figure 6 , Figure 7 Similarly, this indicates that mesophase pitch can be obtained by instantaneously high-temperature electric flash evaporation of raw material 4.

[0085] Comparative Example 1

[0086] Grind an appropriate amount of raw material 3 to obtain a powdered raw material with an average particle size of 800 μm. Weigh the blank sample in the ceramic boat, spread the powdered raw material evenly in the ceramic boat, cover the ceramic boat, and open the air valve and nitrogen valve in sequence. Set the nitrogen flow rate to 340 mL / min and maintain it for 15 minutes. Place the ceramic boat in a tube furnace and perform programmed heating. The temperature rises from room temperature (10 °C) to 380 °C at a heating rate of 10 °C / min for 27 minutes, then holds at 380 °C for 120 minutes. Next, the temperature rises from 380 °C to 430 °C (10 minutes) at a heating rate of 5 °C / min, then holds at 430 °C for 150 minutes. The heating program ends. Allow the tube furnace to cool naturally to below 200 °C (approximately 4 hours), then disconnect the gas supply, remove the ceramic boat, weigh it, take a sample, and analyze and characterize it.

[0087] Product 3', obtained after the tubular furnace thermal reaction of raw material 3, had a weight loss rate of 37.0%, which is higher than the weight loss rate of high-temperature flash evaporation (29%, 30%, and 35%) compared to Examples 1, 2, and 3. The tubular furnace thermal reaction time of Comparative Example 1 was 5 hours, requiring approximately 9 hours or more from start to finish. In contrast, the thermal reaction time of instantaneous ultra-high temperature electric flash evaporation in Examples 1, 2, and 3 was only 0.5 seconds, allowing sample removal 20 seconds after the end of the instantaneous ultra-high temperature electric flash evaporation, with a total time of approximately 60 seconds from start to finish. A comparison of the XRD results of Product 3' and Product 3... Figure 23As can be seen, the XRD test results of raw material 3 and product 3' are basically consistent, indicating that the structure of raw material 3 did not change under the thermal action of the tube furnace at 380℃ and 430℃; only some light components and volatiles were removed. However, raw material 3 developed a crystalline structure after instantaneous ultra-high temperature electric flash evaporation, indicating that raw material 3 underwent a structural change after this process. This is further compared with the infrared results (…). Figure 24 As can be seen, product 3 underwent a structural transformation, containing typical functional groups of mesophase pitch. For example, the absorption peak range of the polycyclic aromatic hydrocarbons in mesophase pitch is 700–900 cm⁻¹, of which 870 cm⁻¹ represents the isolated out-of-plane C-H vibration of the aromatic ring, the absorption peak near 3050 cm⁻¹ represents the C-H bond stretching vibration of the aromatic ring, and the absorption peak in the range of 1300–1450 cm⁻¹ represents the bending and stretching vibrations of the saturated methyl group. Completely different from the high-temperature flash evaporation results, product 3' does not contain typical infrared absorption peaks, indicating that its tubular furnace thermal reaction did not result in a structural transformation.

[0088] Comparative Example 2

[0089] Following the method of Example 4, except that the Joule flash evaporation parameters were set to instantly raise the heating temperature to 2083°C, and after the experiment, product 4' was collected and weighed. Product 4' showed no weight loss compared to the raw material, and the XRD pattern of the product was consistent with that of the raw material. Figure 25 No structural changes have occurred.

[0090] 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 by Joule heating, characterized in that, The method includes: subjecting asphalt raw materials to Joule heating treatment, cooling, and obtaining mesophase asphalt; wherein the heating temperature is 3600-3700℃.

2. The method according to claim 1, wherein, The conditions for Joule heating include: Heating power is 30-70W; and / or The constant voltage is 6-200V; and / or Heating time: 0.1-5 seconds; and / or The heating cycle is 1-3 times; and / or The heating interval is 10-20 seconds.

3. The method according to claim 1 or 2, wherein, The Joule heating method is pulse heating, preferably capacitor pulse discharge Joule heating. Preferably, the conditions for the Joule heating of the capacitor pulse discharge include: The pulse duration is 0.2-0.5 s; and / or The current intensity is 0.01-400A.

4. The method according to any one of claims 1-3, wherein, The asphalt raw material is selected from coal tar pitch and / or coal liquefaction pitch, preferably coal tar pitch.

5. The method according to any one of claims 4, wherein, The coal tar pitch has a size of no more than 1.5 cm in any dimension, preferably 0.1-1.5 cm.

6. The method according to any one of claims 1-5, wherein, The heat treatment is carried out under vacuum conditions and / or inert gas atmosphere; Preferably, the inert gas is selected from one or more of nitrogen, helium, and argon.

7. The method according to any one of claims 1-6, wherein, The heating treatment can be direct heating or indirect heating.

8. The method according to claim 7, wherein, The direct heating is performed by mixing a conductive medium into the asphalt raw material and then heating it. Preferably, The conductive medium is selected from one or more of carbon black, carbon nanotubes, and graphene; and / or The resistance of the conductive medium is 1-30Ω; and / or The amount of the conductive medium added is 5-20 wt% of the asphalt raw material.

9. The method according to claim 7, wherein, The indirect heating method involves wrapping the asphalt raw material in graphite paper and / or graphite felt for heating.

10. The method according to any one of claims 1-9, wherein, The method further includes drying the asphalt raw material before Joule heating treatment, preferably under the following conditions: The drying temperature is 40-60℃; and / or The drying time is 2-4 hours.

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