A refined coal liquefaction pitch-based capacitor carbon and a method for preparing the same

Abstract

This application belongs to the field of functional carbon material preparation technology, specifically relating to a refined coal liquefaction pitch-based capacitor carbon and its preparation method. The preparation method of the refined coal liquefaction pitch-based capacitor carbon includes the following steps: pre-oxidizing the refined coal liquefaction pitch; mixing the pre-oxidized refined coal liquefaction pitch with an activator, and then performing carbonization and activation treatments to obtain the capacitor carbon; the activator includes low-melting-point activating molten salt and high-melting-point activating molten salt. The preparation method of this application uses refined coal liquefaction pitch as raw material, employs a composite activator, and uses a microwave tube furnace instead of the traditional high-temperature tube furnace heating method for pre-oxidation, carbonization, and activation treatment, promoting the clean and efficient utilization of coal and the efficient and environmentally friendly preparation of capacitor carbon; through microwave tube furnace heating, heat is generated by friction and collision between the raw material and activator molecules, which has advantages over resistance tube furnaces such as shorter activation time, lower energy consumption, smaller temperature gradient, and better activation uniformity.

Description

Technical Field

[0001] This invention belongs to the field of functional carbon material preparation technology, specifically relating to a refined coal liquefaction pitch-based capacitor carbon and its preparation method. Background Technology

[0002] New renewable energy sources are a key force driving energy structure transformation and achieving sustainable development. Simultaneously, downstream energy storage technology has become a focus of research in various countries. Supercapacitors, as a novel energy storage device, exhibit broad application prospects in new energy vehicles, smart grids, rail transit, and portable electronic products due to their high power density, fast charging and discharging speeds, and long cycle life. Electrode materials are the core determinant of supercapacitor performance. Among them, carbon materials are the most widely used electrode materials due to their wide availability, good chemical stability, and excellent conductivity. Among various carbon materials, capacitor carbon, with its high specific surface area, can efficiently store charge through the double-layer energy storage mechanism, making it a key material for preparing high-performance supercapacitor electrodes. Currently, commercially available capacitor carbon mostly uses activated carbon, whose raw materials are mainly derived from coal, petroleum coke, and biomass. However, these carbon sources are largely dependent on imports, resulting in high prices and susceptibility to fluctuations in climate or international situations. Furthermore, existing methods for preparing capacitor carbon involve lengthy carbonization and activation processes and consume significant energy. Traditional resistance-heated tube furnaces transfer heat through the furnace body, which in turn conducts heat and convection between the furnace body and the corundum ceramic boat and raw materials. This process typically takes 5-8 hours to complete the sample heating, carbonization, and activation, resulting in a long time frame and high energy consumption. It also suffers from slow temperature response and uneven temperature distribution. Furthermore, current preparation methods are plagued by highly corrosive activators that cause environmental pollution. To achieve the high specific surface area of ​​capacitive carbon, strong corrosive reagents such as KOH and H3PO4 are commonly used for activation. These activators corrode equipment, threatening production safety. Additionally, capacitive carbon prepared using these activators requires extensive acid or alkali washing, generating large amounts of acid and alkaline wastewater and causing environmental pollution.

[0003] Coal liquefaction pitch, a major solid waste product generated from direct coal liquefaction, is projected to have a production capacity exceeding 4 million tons per year by 2027. This substance is rich in polycyclic aromatic hydrocarbons, possesses a high carbon content and suitable reactivity, making it a highly promising precursor for carbon materials. However, currently, the high-value-added utilization pathways for coal liquefaction pitch are relatively limited. Apart from being used in part as a pitch modifier or fuel, it is mostly regarded as a low-value byproduct or even solid waste, resulting in resource waste.

[0004] Therefore, it is of great significance to invent a green activation strategy that can be rapidly heated to prepare high-performance coal liquefaction pitch-based capacitor carbon. Summary of the Invention

[0005] This application provides a refined coal liquefaction pitch-based capacitor carbon and its preparation method, aiming to solve the problems of low utilization efficiency of existing coal liquefaction pitch, high energy consumption, high cost, and easy environmental pollution in capacitor carbon production.

[0006] The first aspect of this application provides a method for preparing refined coal liquefaction pitch-based capacitor carbon, comprising the following steps:

[0007] (1) Pre-oxidation treatment of refined coal liquefaction pitch; (2) The pre-oxidized refined coal liquefaction pitch and activator are mixed and carbonized and activated to obtain the capacitor carbon; The activator includes low-melting-point molten salts and high-melting-point molten salts.

[0008] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the pre-oxidation treatment includes pre-oxidizing the refined coal liquefaction pitch using a microwave tube furnace.

[0009] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the pre-oxidation treatment temperature is 250-400℃ and the time is 20-40min.

[0010] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the pre-oxidation treatment includes placing refined coal liquefaction pitch in a microwave tube furnace, introducing air into the microwave tube furnace, heating to 250-400°C at a power of 700W-900W, and holding at that temperature for 20-40 minutes for pre-oxidation treatment; more preferably, the air flow rate is 80-120 ml / min.

[0011] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the softening point of the refined coal liquefaction pitch is 100-130℃, and the quinoline insoluble matter is ≤0.01wt%.

[0012] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the particle size of the refined coal liquefaction pitch is 200-300 mesh.

[0013] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the mass ratio of the pre-oxidized refined coal liquefaction pitch to the activator is 1:(1-3).

[0014] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the high melting point activated molten salt includes one or more of potassium carbonate, sodium carbonate, lithium carbonate, potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, and potassium fluoride.

[0015] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the low-melting-point activating molten salt includes HCOOK.

[0016] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the activator includes HCOOK and potassium carbonate; more preferably, the mass ratio of HCOOK and potassium carbonate in the activator is (1-2):1.

[0017] According to some embodiments of the method for preparing refined coal liquefaction pitch-based capacitor carbon described in this application, the carbonization includes carbonization treatment using a microwave tube furnace.

[0018] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the carbonization temperature is 500-700℃ and the time is 10-30min.

[0019] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the carbonization includes mixing pre-oxidized refined coal liquefaction pitch and an activator, placing the mixture in a microwave tube furnace, introducing nitrogen gas into the microwave tube furnace, heating the mixture to 500-700°C at a power of 1000W-1500W, and holding the temperature for 10-30 minutes for carbonization treatment; more preferably, the nitrogen gas flow rate is 50-80 ml / min.

[0020] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the activation includes activation treatment using a microwave tube furnace.

[0021] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the activation temperature is 800-1000℃ and the time is 20-40min.

[0022] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the activation includes placing the carbonization product in a microwave tube furnace, introducing nitrogen gas into the microwave tube furnace, heating to 800-1000℃ at a power of 1000W-1500W, and holding at that temperature for 20-40 minutes for activation treatment.

[0023] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the method further includes the steps of washing and drying the activation product to obtain the capacitor carbon.

[0024] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the cleaning includes cleaning with deionized water until the cleaning solution is neutral.

[0025] According to some embodiments of the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application, the drying temperature is 75-85℃ and the time is 10-15h.

[0026] The second aspect of this application provides a refined coal liquefaction pitch-based capacitor carbon, which is prepared by the preparation method described in the first aspect of this application.

[0027] The beneficial effects of this application include: the preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application uses refined coal liquefaction pitch as raw material, adopts a composite activator, and uses a microwave tube furnace instead of the traditional high-temperature tube furnace heating method for pre-oxidation, carbonization and activation treatment, which promotes the clean and efficient utilization of coal and the efficient and environmentally friendly preparation of capacitor carbon.

[0028] During the activation process, HCOOK in the composite activator can form a molten medium with K2CO3 at medium temperature, which not only acts as a heat transfer medium but also achieves effective contact with the precursor. In addition, the composite activator (K2CO3 and HCOOK) decomposes together into potassium salt, carbon dioxide, water, and hydrogen at high temperature, achieving synergistic activation to generate more micropores, effectively increasing the specific surface area of ​​the capacitor carbon, and realizing the green and efficient preparation of multi-level layered capacitor carbon.

[0029] Microwave tube furnace heating generates heat through friction and collision between raw material and activator molecules. Compared with resistance tube furnace, it has advantages such as shorter activation time, lower energy consumption, smaller temperature gradient, and better activation uniformity. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application; Figure 2 X-ray diffraction test patterns of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 and Comparative Examples 1-5 of this application; Figure 3 The Raman spectrum of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application; Figure 4 Thermogravimetric curve of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application; Figure 5 The nitrogen isothermal adsorption-desorption curves of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 and Comparative Examples 1-5 of this application are shown. Figure 6 This is a pore size distribution curve of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 and Comparative Example 5 of this application; Figure 7 This is a cyclic voltammetry curve of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application; Figure 8 This is a constant current charge-discharge curve of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application; Figure 9 This is the electrochemical impedance spectroscopy of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application. Detailed Implementation

[0031] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] This application provides a method for preparing refined coal liquefaction pitch-based capacitor carbon, comprising the following steps: (1) Pre-oxidation treatment of refined coal liquefaction pitch; (2) The pre-oxidized refined coal liquefaction pitch and activator are mixed and carbonized and activated to obtain the capacitor carbon; The activator includes low-melting-point molten salts and high-melting-point molten salts.

[0034] The preparation method of refined coal liquefaction pitch-based capacitor carbon described in this application uses a composite activator. The low-melting-point activating molten salt in the composite activator can effectively reduce the melting point of the high-melting-point activating molten salt, and together they form a molten medium, which not only acts as a heat transfer medium, but also achieves effective contact with the precursor. In addition, the composite activator (HCOOK and K2CO3) decomposes together into potassium salt, carbon dioxide, water and hydrogen at high temperature, achieving synergistic activation to generate more micropores, effectively increasing the specific surface area of ​​the capacitor carbon, and realizing the green and efficient preparation of multi-level layered capacitor carbon.

[0035] In some embodiments of this application, the pre-oxidation treatment includes pre-oxidizing refined coal liquefaction pitch using a microwave tube furnace. Through this pre-oxidation treatment, oxygen molecules are introduced, allowing them to diffuse into the pitch and trigger cross-linking and polymerization reactions between the basic structure of the refined coal liquefaction pitch and its oxygen-containing functional groups. This transforms the originally thermoplastic pitch into a relatively rigid and stable thermosetting disordered carbon skeleton, effectively preventing carbon layer rearrangement during carbonization and inhibiting the melting and recombination of the coal liquefaction pitch during carbonization. Furthermore, the oxygen on the side chains of polycyclic aromatic molecules increases the wettability of the material, which is beneficial for the adhesion of activators and etching of relatively unstable structural regions. It also releases some CO2 and CO, thereby promoting pore formation and development and increasing the specific surface area of ​​the capacitive carbon.

[0036] Microwave heating exhibits significant advantages in oxidation reactions. By exciting the vibration of polar molecules within the material, microwave heating achieves rapid and uniform heating, avoiding the problems of excessively high surface temperatures and uneven heating that can occur with traditional heat conduction heating. This allows for better control over the depth and uniformity of the oxidation reaction. Under microwave heating conditions, the diffusion rate of oxygen molecules is accelerated, enabling them to effectively penetrate the pitch structure and react with defective carbon atoms and small molecular structures, promoting the formation of stable oxygen-containing functional groups (such as carboxyl, quinone, and phenolic hydroxyl groups). The increase in these polar functional groups also improves the hydrophilicity and pseudocapacitance of the capacitive carbon, further enhancing its electrochemical performance. In addition, microwave pre-oxidation effectively prevents carbon layer rearrangement and melting during the carbonization process of pitch-based carbon, inhibiting the melting and recombination of pitch, laying a more stable foundation for subsequent carbonization and activation processes, and further improving the conductivity and energy storage performance of the capacitive carbon.

[0037] In some embodiments of this application, the temperature of the pre-oxidation treatment is 250-400℃, such as 250℃, 280℃, 300℃, 350℃, 380℃, 400℃, etc., and the time is 20-40min; such as 20min, 28min, 30min, 32min, 35min, 40min, etc.

[0038] In some embodiments of this application, the pre-oxidation treatment includes placing refined coal liquefaction pitch in a microwave tube furnace, introducing air into the microwave tube furnace, heating to 250-400°C at a power of 700W-900W, and holding at that temperature for 20-40 minutes for pre-oxidation treatment; more preferably, the air flow rate is 80-120ml / min.

[0039] In some embodiments of this application, the softening point of the refined coal liquefaction pitch is 100-130℃, and the quinoline insoluble matter is ≤0.01wt%.

[0040] In some embodiments of this application, the particle size of the refined coal liquefaction pitch is 200-300 mesh, such as 200 mesh, 250 mesh, 280 mesh, 300 mesh, etc.

[0041] In some embodiments of this application, the mass ratio of the pre-oxidized refined coal liquefaction pitch to the activator is 1:(1-3), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc. This ratio range can improve activation efficiency, ensure that the activator fully participates in the reaction and effectively opens the pore structure of the carbon material, and avoid incomplete or over-activation due to insufficient or excessive activator, which would affect the capacitance performance. In addition, the salt-sealing carbonization effect is also enhanced within this range. The liquid-solid contact between the activator and the precursor makes the activation process more efficient, while the release of gas in the closed environment and the reaction etching effect help to form pores in the carbon material. Controlling the ratio within the range of 1:1 to 1:3 also has economic advantages. Under the premise of ensuring a sufficient supply of activator and promoting the chemical reaction or modification of pitch, it effectively avoids waste of activator and reduces costs.

[0042] In some embodiments of this application, the high-melting-point activated molten salt includes one or more of potassium carbonate, sodium carbonate, lithium carbonate, potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, and potassium fluoride.

[0043] In some embodiments of this application, the low-melting-point activated molten salt includes HCOOK.

[0044] In some embodiments of this application, the activator includes HCOOK and potassium carbonate; more preferably, the mass ratio of HCOOK to potassium carbonate in the activator is (1-2):1. For example, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, etc. Both HCOOK and K2CO3 play a significant role in the activation process. The low melting point of HCOOK allows it to disrupt the regular structure of the original crystals in the mixture through the interaction between molecules and atoms when mixed with K2CO3 in a certain proportion, thereby completing the solid-to-liquid phase transition within the melting point range below that of high-melting-point molten salts. This process promotes the encapsulation and activation of asphalt by the molten salt, increases the reaction contact area, and further enhances the pore formation effect. The optimal activation effect can be achieved when the mass ratio of HCOOK to K2CO3 is in the range of 1:1 to 2:1. When the HCOOK ratio is too low, the melting point of the mixed molten salt is too high, making it impossible to achieve effective uniform distribution of the activator and asphalt, as well as liquid-phase encapsulation. This results in incomplete activation, which in turn reduces the specific surface area and electrochemical performance of the capacitor carbon. If the HCOOK ratio is too high, it will cause the HCOOK to decompose and produce excessive gas, which will lead to local bubbling and damage to micropores, generating excessive mesopores and macropores, significantly reducing the specific surface area of ​​the capacitor carbon and weakening its energy storage performance.

[0045] In some embodiments of this application, the carbonization includes carbonization treatment using a microwave tube furnace. Microwave carbonization can significantly improve the specific surface area and pore structure of the capacitor carbon, enabling uniform heating of the material and optimizing pore distribution, thereby enhancing the electrochemical performance of the capacitor carbon. By precisely controlling the carbonization process, over- or incomplete carbonization is avoided, maintaining the conductivity and stability of the capacitor carbon. Furthermore, microwave carbonization greatly shortens processing time and reduces energy consumption; traditional carbonization takes several hours, while microwave carbonization only takes several minutes to tens of minutes, offering significant advantages in environmental protection and sustainable development.

[0046] In some embodiments of this application, the carbonization temperature is 500-700℃, such as 500℃, 550℃, 580℃, 600℃, 650℃, 700℃, etc., and the time is 10-30min, such as 10min, 15min, 20min, 22min, 28min, 30min, etc.

[0047] In some embodiments of this application, the carbonization includes mixing pre-oxidized refined coal liquefaction pitch and an activator, placing the mixture in a microwave tube furnace, introducing nitrogen gas into the microwave tube furnace, heating the mixture to 500-700°C at a power of 1000W-1500W, and holding the temperature for 10-30 minutes for carbonization treatment; more preferably, the nitrogen gas flow rate is 50-80 ml / min.

[0048] In some embodiments of this application, the activation includes activation treatment using a microwave tube furnace; the application of microwave activation combined with molten salt-coated pitch technology in the preparation of capacitive carbon fully leverages the high efficiency of microwave heating and the heat transfer advantages of molten salt. Firstly, microwave energy can directly act on the interior of the material, heating it rapidly and uniformly, reducing energy loss and improving heating efficiency. Compared to traditional heating methods, microwave activation achieves shorter processing times, thereby significantly improving production efficiency. Molten salt, as a heat transfer medium, can more effectively absorb microwave energy, promoting the uniformity of the heating process, and further optimizing the temperature distribution by coating the pitch material, avoiding localized overheating or uneven heating, and ensuring the stability of the activation process. This combination of molten salt-coated pitch not only improves activation efficiency but also effectively reduces the formation of byproducts, improving the purity and quality of the product. Furthermore, microwave activation has high energy conversion efficiency, significantly reducing energy consumption compared to traditional activation methods, offering good environmental and energy-saving advantages. By precisely controlling the heating temperature, power, and reaction time, key properties such as pore structure and specific surface area can be optimized according to different requirements of capacitive carbon, ultimately obtaining capacitive carbon materials with excellent electrochemical performance.

[0049] In some embodiments of this application, the activation temperature is 800-1000℃, such as 800℃, 850℃, 900℃, 930℃, 970℃, 1000℃, etc., and the time is 20-40min, such as 20min, 25min, 30min, 35min, 40min, etc.

[0050] In some embodiments of this application, the activation includes placing the carbonized product in a microwave tube furnace, introducing nitrogen gas into the microwave tube furnace, heating to 800-1000°C at a power of 1000W-1500W, and holding at that temperature for 20-40 minutes for activation treatment.

[0051] In some embodiments of this application, the method further includes the steps of washing and drying the activation product to obtain the capacitor carbon. Washing with deionized water removes impurities from the surface of the capacitor carbon, especially soluble salts and metal ions, thus preventing these impurities from adversely affecting the electrochemical performance of the capacitor carbon.

[0052] In some embodiments of this application, the cleaning includes rinsing with deionized water until the cleaning solution is neutral.

[0053] In some embodiments of this application, the drying temperature is 75-85℃, such as 75℃, 78℃, 80℃, 85℃, etc., and the time is 10-15h, such as 10h, 12h, 13h, 15h, etc. The activated product is added to deionized water for stirring and washing, followed by ultrasonic washing for 20 minutes. After standing, the supernatant is removed, and the above washing steps are repeated until the supernatant is neutral. The washed carbon material is placed in a sand core filter device for vacuum filtration to extract the sample, and the sample is dried in a vacuum oven to obtain the capacitor carbon material.

[0054] This application also provides a refined coal liquefaction pitch-based capacitor carbon, prepared by the method described in the first aspect of this application. The capacitor carbon sample described in this application exhibits excellent electrochemical properties, with a specific surface area of ​​1100-1600 m². 2 ·g -1 The total pore volume is 0.5-0.7 cm³. 3 ·g -1 Furthermore, the micropore volume accounts for more than 80% of the total pore volume, exhibiting a layered porous structure. Three-electrode electrochemical testing revealed that the CV curve of the capacitive carbon exhibited a near-rectangular shape, indicating its excellent dual-capacitance characteristics; the GCD curve showed a symmetrical triangle shape, and at 0.5 A·g2... -1 and 1 A·g -1 The specific capacitance at current density is 226 F·g -1 and 194 F·g -1Furthermore, its EIS curve exhibits a smaller semi-circular characteristic in the low-frequency region, indicating lower charge transport resistance, further demonstrating its excellent electrochemical performance. Compared with capacitor carbon prepared by single-component salt activation and resistance tube furnace carbonization activation, the capacitor carbon prepared by the method described in this application has a larger specific surface area, higher microporosity, and better specific capacitance, resulting in superior overall performance.

[0055] The technical solution of this application will be further described below with reference to specific embodiments.

[0056] Example 1 A method for preparing refined coal liquefaction pitch-based capacitor carbon includes the following steps: (1) Place refined coal liquefaction pitch with a softening point of 120℃ and a quinoline insoluble content of <0.01wt% and a particle size of 200-300 mesh in a microwave tube furnace, introduce air into the microwave tube furnace at a flow rate of 100ml / min, and then heat it to 300℃ at a power of 800W for pre-oxidation for 30min. (2) Mix HCOOK and K2CO3 at a mass ratio of 1:1 to obtain a composite activator; (3) Grind and mix 2g of pre-oxidized refined coal liquefaction pitch and 4g of composite activator in a mortar. Place the mixture in a microwave tube furnace and introduce nitrogen into the microwave tube furnace at a flow rate of 60ml / min. Then heat the furnace to 600℃ at a power of 1200W and hold for 20min for carbonization treatment. Then continue to heat the furnace to 800℃ at the same power and hold for 30min for activation treatment. After the activation treatment is completed, allow it to cool naturally to room temperature.

[0057] (5) Take out the activated sample, add it to deionized water and stir to clean it, then ultrasonically clean it for 20 minutes, let it stand, remove the supernatant, repeat the above cleaning steps until the supernatant is neutral, put the washed carbon material in the sand core filter device for vacuum filtration to remove the sample, and dry the sample in an 80°C vacuum oven for 12 h to obtain the capacitor carbon.

[0058] Example 2 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Example 2 and that in Example 1 is the amount of pre-oxidized refined coal liquefaction pitch and composite activator used in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Example 2.

[0059] The specific operating steps include: Grind and mix 2g of pre-oxidized refined coal liquefaction pitch and 2g of composite activator in a mortar. Place the mixture in a microwave tube furnace and introduce nitrogen gas into the microwave tube furnace at a flow rate of 60ml / min. Then, heat the furnace to 600℃ at a power of 1200W and hold for 20min for carbonization treatment. Then, continue to heat the furnace to 800℃ at the same power and hold for 30min for activation treatment. After the activation treatment is completed, allow it to cool naturally to room temperature. The remaining operation steps are the same as in Example 1.

[0060] Example 3 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Example 3 and that in Example 1 is the amount of pre-oxidized refined coal liquefaction pitch and composite activator used in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Example 3.

[0061] The specific operating steps include: Grind and mix 2g of pre-oxidized refined coal liquefaction pitch and 6g of composite activator in a mortar. Place the mixture in a microwave tube furnace and introduce nitrogen gas into the microwave tube furnace at a flow rate of 60ml / min. Then, heat the furnace to 600℃ at 1200W and hold for 20min for carbonization. Then, continue heating the furnace to 800℃ at the same power and hold for 30min for activation. After activation, allow the furnace to cool naturally to room temperature. The remaining steps are the same as in Example 1.

[0062] Example 4 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Example 4 and that in Example 1 is that the composite activator used in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Example 4 is a mixture of HCOOK and K2CO3 in a mass ratio of 1:2.

[0063] Example 5 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Example 5 and that in Example 1 is that the composite activator used in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Example 5 is a mixture of HCOOK and K2CO3 in a mass ratio of 2:1.

[0064] Comparative Example 1 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 1 and Example 1 is that KCl is used instead of HCOOK in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 1, and the rest of the operation is the same as in Example 1.

[0065] Comparative Example 2 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 2 and Example 1 is that KCl is used instead of K2CO3 in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 2, and the rest of the operation is the same as in Example 1.

[0066] Comparative Example 3 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 3 and Example 1 is that HCOOK is used as the activator in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 3, and the rest of the operation is the same as in Example 1.

[0067] Comparative Example 4 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 4 and Example 1 is that only K2CO3 is used as an activator in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 4, and the rest of the operation is the same as in Example 1.

[0068] Comparative Example 5 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 5 and Example 1 is that a resistance high-temperature tube furnace is used instead of a microwave tube furnace for pre-oxidation, carbonization and activation treatment in the preparation process of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 5.

[0069] Comparative Example 6 The only difference between the preparation method of refined coal liquefaction pitch-based capacitor carbon in Comparative Example 6 and Example 1 is that the refined coal liquefaction pitch was not pre-oxidized during the preparation process of the refined coal liquefaction pitch-based capacitor carbon in Comparative Example 6.

[0070] Performance study of the refined coal liquefaction pitch-based capacitor carbon described in Examples 1-5 and Comparative Examples 1-6 of this application: Test method: The refined coal liquefaction pitch-based capacitor carbon described in Examples 1-5 and Comparative Examples 1-6 of this application were used as active material materials for supercapacitor electrodes. These materials were mixed with polytetrafluoroethylene (PTFE) and acetylene black in a mass ratio of 8:1:1 in an appropriate amount of ethanol to form a homogeneous slurry, which was then coated onto nickel foam sheets (1 cm thick). 1 cm) as the working electrode, each piece of foamed nickel coating has a mass of 10-20 mg, the working electrode prepared above is pressed under a pressure of 5 MPa for 5 min, and then dried in a vacuum drying oven at 100℃ for 8 h to obtain a carbon electrode; The carbon electrodes described above were used as working electrodes, and platinum sheet electrodes (1cm) were employed. A 1 cm electrode was used as the counter electrode, an Hg / HgO electrode was used as the reference electrode, and a 6 mol / L KOH solution was used as the electrolyte to form a three-electrode test system. Cyclic voltammetry (CV), galvanostatic charge-discharge test (GCD), and electrochemical impedance spectroscopy (EIS) were performed to evaluate the electrochemical properties of the prepared capacitive carbon. The results are shown in Table 1.

[0071] Table 1

[0072] As can be seen from Table 1, using mixed molten salt as the activation system can effectively construct porous carbon materials with high specific surface area, which can exceed 1100 m². 2 ·g -1 Furthermore, the micropore volume fraction accounts for more than 80% of the total pore volume. By adjusting the proportion of the activator and the ratio of the two molten salts, the ratio of micropores to mesopores within the material can be precisely controlled.

[0073] Compared with Comparative Examples 3 and 4, which were activated using a single molten salt, the capacitor carbon described in Example 1 of this application exhibits a more significant activation advantage in terms of pore structure construction in the mixed molten salt system.

[0074] A comparison of the capacitor carbon obtained in Example 1 of this application with the capacitor carbon prepared in Comparative Example 5 reveals that the microwave tube furnace is significantly superior to the traditional resistance heating tube furnace in terms of activation efficiency and pore structure control.

[0075] Comparative Example 6 was obtained without pre-oxidation. The sample exhibited a hard, caking state, making it difficult to remove for further processing. This demonstrates that pre-oxidation is crucial for inhibiting the melting and reorganization of coal liquefaction pitch during carbonization and for adjusting the morphology and properties of capacitive carbon.

[0076] Scanning electron microscope image of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application; from Figure 1 As can be seen, the capacitor carbon prepared by microwave-assisted molten salt activation exhibits a honeycomb porous structure with diverse pore sizes and interconnected pores. In this layered porous structure, the abundant micropores significantly increase the specific surface area, while the presence of mesopores and macropores facilitates electrolyte permeation and ion migration, thereby effectively improving its capacitance performance.

[0077] X-ray diffraction patterns of the refined coal liquefaction pitch-based capacitor carbon described in Examples 1, 1, 2, 3, 4, and 5 of this application are shown below. Figure 2 As shown.

[0078] from Figure 2As can be seen from the data, the two diffraction peaks of the capacitor carbon prepared in Example 1 and Comparative Examples 1-5 of this application are located near 21° and 44°, respectively, corresponding to the (002) and (100) crystal planes of graphite crystals. Compared with the comparative examples, the (002) crystal plane diffraction peak of the example samples generally shifts to a lower angle, indicating that the interlayer spacing of graphite is increased, the amorphous structure is enhanced, and the pore structure is abundant.

[0079] The Raman spectrum of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application is as follows: Figure 3 As shown.

[0080] from Figure 3 It can be seen that in Example 1 of this application, the prepared capacitor carbon at 1350 cm⁻¹ 1 and 1590 cm 1 The peaks at these locations represent the D peak, signifying defective structures, and the G peak, signifying ordered structures, respectively. D / I G The ratio, as an important indicator of the disorder of carbon-based materials, is obtained by calculating the area ratio of the D peak to the G peak. Example 1 sample I... D / I G The ratio of 1.71 indicates that the capacitor carbon has a high degree of disorder due to the presence of a large number of pores.

[0081] Thermogravimetric curve of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application is as follows: Figure 4 As shown.

[0082] from Figure 4 It can be seen that when the capacitor carbon prepared in Example 1 of this application is heated from 30°C to the final temperature of 800°C at a heating rate of 10°C / min, the sample weight loss is only 8.27%, indicating that the capacitor carbon prepared in Example 1 has good thermal stability.

[0083] The nitrogen isothermal adsorption-desorption curves of the refined coal liquefaction pitch-based capacitive carbon described in Examples 1, 1, 2, 3, 4, and 5 of this application are shown below. Figure 5 As shown.

[0084] from Figure 5 It can be seen that the capacitive carbons prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5 all exhibit typical type I isothermal adsorption characteristics, accompanied by obvious hysteresis loops, indicating that the pore structure is mainly micropores, while containing a certain proportion of mesopores.

[0085] The pore size distribution curves of the refined coal liquefaction pitch-based capacitor carbon described in Embodiment 1 and Comparative Example 5 of this application are as follows: Figure 6 As shown.

[0086] from Figure 6 It can be seen that, in comparing the capacitor carbon prepared in Example 1 and Comparative Example 5 of this application, the pore size range of the capacitor carbon prepared in Example 1 is mainly concentrated in the range of 0-4 nm, while that in Comparative Example 5 is 0-2 nm. Compared with the capacitor carbon prepared in Comparative Example 5, the capacitor carbon in Example 1 has a wider pore size distribution, exhibiting a layered porous structure dominated by micropores and supplemented by an appropriate amount of mesopores. The presence of mesopores helps to accelerate the rapid transport of electrolyte ions, while the micropore-dominated structure can effectively improve the specific capacitance, thereby enhancing its application potential in supercapacitors. This indicates that the carbonization and activation effect of the microwave tube furnace is superior to that of the traditional resistance tube furnace.

[0087] The cyclic voltammetry curve of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application is as follows: Figure 7 As shown.

[0088] from Figure 7 It can be seen that the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application exhibits an approximately rectangular morphology at low scan rates, indicating that the material has ideal double-layer capacitor behavior.

[0089] The constant current charge-discharge curves and electrochemical impedance spectroscopy of the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application are shown below. Figure 8 and Figure 9 As shown.

[0090] from Figure 8 and Figure 9 It can be seen that: the refined coal liquefaction pitch-based capacitor carbon described in Example 1 of this application is at 0.5 A•g -1 and 1A•g -1 The specific capacitance at current density reached 226 F•g -1 and 194F•g -1 Its impedance spectrum exhibits a small semicircular feature in the low-frequency region, indicating low charge transport resistance and excellent overall electrochemical performance.

[0091] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing refined coal liquefaction pitch-based capacitor carbon, characterized in that, Includes the following steps: (1) Pre-oxidation treatment of refined coal liquefaction pitch; (2) The pre-oxidized refined coal liquefaction pitch and activator are mixed and carbonized and activated to obtain the capacitor carbon; The activator includes low-melting-point molten salts and high-melting-point molten salts.

2. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The pre-oxidation treatment includes pre-oxidation of refined coal liquefaction pitch using a microwave tube furnace. Preferably, the pre-oxidation treatment is performed at a temperature of 250-400℃ for 20-40 minutes. Preferably, the pre-oxidation treatment includes placing refined coal liquefaction pitch in a microwave tube furnace, introducing air into the microwave tube furnace, heating to 250-400°C at a power of 700W-900W, and holding at that temperature for 20-40 minutes for pre-oxidation treatment; more preferably, the air flow rate is 80-120ml / min.

3. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The refined coal liquefaction pitch has a softening point of 100-130℃ and quinoline insolubles ≤0.01wt%. And / or, the particle size of the refined coal liquefaction pitch is 200-300 mesh.

4. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The mass ratio of the pre-oxidized refined coal liquefaction pitch to the activator is 1:(1-3).

5. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The high-melting-point activated molten salt includes one or more of potassium carbonate, sodium carbonate, lithium carbonate, potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, and potassium fluoride. And / or, the low-melting-point activated molten salt includes HCOOK; Preferably, the activator includes HCOOK and potassium carbonate; more preferably, the mass ratio of HCOOK to potassium carbonate in the activator is (1-2):

1.

6. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The carbonization includes carbonization treatment using a microwave tube furnace. Preferably, the carbonization temperature is 500-700℃ and the time is 10-30 minutes; Preferably, the carbonization process includes mixing pre-oxidized refined coal liquefaction pitch and an activator, placing the mixture in a microwave tube furnace, introducing nitrogen gas into the microwave tube furnace, heating the mixture to 500-700°C at a power of 1000W-1500W, and holding the temperature for 10-30 minutes for carbonization treatment; more preferably, the nitrogen gas flow rate is 50-80 ml / min.

7. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The activation includes activation treatment using a microwave tube furnace; Preferably, the activation temperature is 800-1000℃ and the activation time is 20-40 min; Preferably, the activation includes placing the carbonized product in a microwave tube furnace, introducing nitrogen gas into the microwave tube furnace, heating to 800-1000°C at a power of 1000W-1500W, and holding at that temperature for 20-40 minutes for activation treatment.

8. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 1, characterized in that, The process also includes the steps of washing and drying the activated product to obtain the capacitor carbon.

9. The method for preparing refined coal liquefaction pitch-based capacitor carbon according to claim 8, characterized in that, The cleaning process includes rinsing with deionized water until the cleaning solution is neutral. And / or, the drying temperature is 75-85℃ and the time is 10-15h.

10. A refined coal liquefaction pitch-based capacitor carbon, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

Images