A method for preparing a structurally preserved graphitized porous carbon material
Patent Information
- Application Number
- CN202610851166.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-12
- Publication Date
- 2026-08-18
AI Technical Summary
[0005]本申请针对现有技术中褐煤基多孔碳材料在提高石墨化程度时难以保持较高比表面积和稳定多孔结构的技术问题，提供一种结构保持型石墨化多孔碳材料的制备方法
参阅图1，本申请提供一种结构保持型石墨化多孔碳材料的制备方法，本申请解决了现有技术中褐煤基碳材料高温处理时“石墨化程度提高但比表面积下降”的矛盾。现有高温处理虽能提升石墨化度，但孔结构收缩严重，比表面积保留率通常不足50%。本申请针对褐煤挥发分高、骨架刚性弱的特点，先通过钾盐混合球磨和预热处理，使褐煤形成稳定的片状多孔前驱体骨架，再进行酸洗、洗涤、分离、干燥得到片状多孔前驱体；之后在限定的温度和时间窗口内进行处理，使碳骨架在已有骨架上发生有序重排而非从头重构。这种先建骨架、后做重排的工艺顺序，使得石墨化程度的提升主要发生在骨架基本定型之后，从而有效减缓了后续高温处理过程中孔结构进一步收缩及比表面积过度下降的问题，使所得材料在石墨化程度提高后仍能够保持二维片状多孔形貌及较高比表面积。相较于现有技术中高温处理导致比表面积保留率通常不足50%的局限，本申请实测比表面积保留率可达60.3%~93.5%，显著优于现有水平。
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Figure CN122586006A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of carbon material preparation technology, specifically to a method for preparing a structure-preserving graphitized porous carbon material. Background Technology
[0002] Lignite, with its low degree of coalification, is characterized by high moisture content, high volatile matter, and low calorific value, and has long been primarily used as a low-value-added fuel for power generation. Under the "dual carbon" target (coal and carbon emissions), the transformation of coal from fuel to material has become an inevitable trend, and the high-value-added utilization of lignite has become a pressing technical problem for the industry. Due to its sparse macromolecular structure and naturally porous particle morphology, lignite readily forms high specific surface area carbon materials, making it an excellent raw material for preparing catalyst supports, adsorbent materials, and electrochemical energy storage materials.
[0003] Porous carbon materials, due to their high specific surface area, good electrical conductivity, high chemical stability, and tunable pore structure, are widely used in supercapacitors, lithium-ion batteries, catalyst supports, and gas adsorption and separation. Existing technologies for preparing graphitized porous carbon materials mainly include chemical activation, molten salt template methods, and high-temperature heat treatment. However, these technologies all have limitations: chemical activation easily introduces a large number of defects into the material framework, resulting in low material order and graphitization degree; molten salt template methods struggle to balance pore structure development with framework ordering; and traditional tubular furnace heat treatment suffers from slow heating, long cycles, and high energy consumption, which are detrimental to rapid carbon atom rearrangement and efficient graphitization.
[0004] In recent years, rapid Joule heating technology has been gradually applied to the preparation and structural regulation of coal-based carbon materials due to its advantages of fast heating rate, short reaction time, and high processing efficiency. It can effectively promote the rapid and orderly rearrangement of carbon atoms and improve the degree of graphitization. However, this technology still has a prominent contradiction—as the processing intensity increases, while the degree of graphitization improves, the specific surface area and porosity decrease. Lignite, in particular, as a low-rank coal, is more prone to structural shrinkage, reduced porosity, and skeletal instability during rapid high-temperature processing due to its high volatile matter content, numerous oxygen-containing groups, and weak skeletal rigidity, leading to a decrease in specific surface area and poorer structural uniformity. Therefore, there is an urgent need for a method to prepare structure-preserving graphitized porous carbon materials. Summary of the Invention
[0005] This application addresses the technical problem in the prior art that lignite-based porous carbon materials are difficult to maintain a high specific surface area and a stable porous structure when increasing the degree of graphitization, and provides a method for preparing a structure-preserving graphitized porous carbon material.
[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a method for preparing a structure-preserving graphitized porous carbon material, comprising the following steps: Lignite and potassium salt were mixed and ball-milled to obtain a uniformly mixed powder; The mixed powder is preheated to obtain a preheated product, and the preheated product is acid-washed, washed, separated and dried to obtain a sheet-like porous precursor. The sheet-like porous precursor is processed within a defined temperature and time window to cause the carbon skeleton in the sheet-like porous precursor to undergo ordered rearrangement, thereby obtaining a structure-preserving graphitized porous carbon material.
[0007] Furthermore, the potassium salt includes potassium carbonate and potassium chloride.
[0008] Furthermore, the total mass ratio of lignite to potassium salt is 1:10, and the molar ratio of potassium carbonate to potassium chloride is 1:1 to 7:3.
[0009] Furthermore, the ball milling time is 4 hours, and the particle size of the uniformly mixed powder obtained after ball milling is 100 mesh to 300 mesh.
[0010] Furthermore, the preheating treatment temperature is 750°C, and the treatment time is 5 hours.
[0011] Furthermore, the pickling is performed using hydrochloric acid solution; the washing is performed sequentially using deionized water and ethanol; the drying temperature is 65–75°C, and the drying time is 12 hours.
[0012] Furthermore, the defined temperature and time window are: a processing temperature of 1300–1700°C and a processing time of 40 seconds.
[0013] Furthermore, the concentration of the hydrochloric acid solution used in the pickling is 0.5–2 mol / L.
[0014] Secondly, this application provides a structure-preserving graphitized porous carbon material prepared by the aforementioned method. The structure-preserving graphitized porous carbon material exhibits a two-dimensional sheet-like porous structure and a specific surface area of 900–2000 nm. .
[0015] Furthermore, the specific surface area retention rate of the structure-preserving graphitized porous carbon material relative to the sheet-like porous precursor is not less than 60%.
[0016] Compared with the prior art, this application has the following beneficial effects: See Figure 1This application provides a method for preparing structure-preserving graphitized porous carbon materials, which solves the contradiction in the prior art where "the degree of graphitization increases but the specific surface area decreases" during high-temperature treatment of lignite-based carbon materials. Although existing high-temperature treatments can increase the degree of graphitization, the pore structure shrinks severely, and the specific surface area retention rate is usually less than 50%. This application addresses the characteristics of lignite, such as high volatile matter and weak skeleton rigidity. First, potassium salt mixing and ball milling and preheating treatment are used to form a stable sheet-like porous precursor skeleton from lignite. Then, acid washing, washing, separation, and drying are performed to obtain the sheet-like porous precursor. Subsequently, treatment is carried out within a limited temperature and time window, allowing the carbon skeleton to undergo ordered rearrangement on the existing skeleton rather than de novo reconstruction. This process sequence of first building the skeleton and then rearranging ensures that the increase in graphitization mainly occurs after the skeleton is basically formed, thus effectively mitigating the problem of further shrinkage of the pore structure and excessive decrease in specific surface area during subsequent high-temperature treatment. This allows the obtained material to maintain a two-dimensional sheet-like porous morphology and a high specific surface area even after the degree of graphitization has increased. Compared to the limitations of existing technologies where high-temperature treatment typically results in a surface area retention rate of less than 50%, the measured surface area retention rate of this application can reach 60.3%~93.5%, which is significantly better than the existing level.
[0017] This application achieves a highly efficient conversion of low-value lignite into high-value-added functional carbon materials, with high process efficiency and suitability for industrial production. Lignite is widely available and inexpensive, requiring no complex pre-purification. A lamellar porous precursor is obtained directly through ball milling, preheating, acid washing, and drying, followed by a short-term high-temperature treatment to achieve ordered rearrangement of the carbon skeleton. Compared to the several hours of high-temperature treatment in traditional tubular furnaces, the processing time is significantly shortened, energy consumption is significantly reduced, and each step involves mature processes with universal equipment and controllable parameters, making it easy to scale up from the laboratory to industrial production. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a flowchart illustrating the synthesis and structural design of the structure-preserving graphitized porous carbon material described in this invention.
[0020] Figure 2 This is a SEM image of the sheet-like porous precursor described in this invention.
[0021] Figure 3 This is an SEM image of the product obtained in Example 1 of the present invention.
[0022] Figure 4 This is an SEM image of the product obtained in Example 2 of the present invention.
[0023] Figure 5 This is an SEM image of the product obtained in Example 3 of the present invention.
[0024] Figure 6 This is a schematic diagram of the EDS spectrum of the sheet-like porous precursor described in this invention.
[0025] Figure 7 This is a schematic diagram of the EDS spectrum of the product obtained in Example 1 of the present invention.
[0026] Figure 8 This is a schematic diagram of the EDS spectrum of the product obtained in Example 2 of the present invention.
[0027] Figure 9 This is a schematic diagram of the EDS spectrum of the product obtained in Example 3 of the present invention.
[0028] Figure 10 This is a TEM schematic diagram of the sheet-like porous precursor described in this invention.
[0029] Figure 11 This is a TEM diagram of the product obtained in Example 1 of the present invention.
[0030] Figure 12 This is a TEM diagram of the product obtained in Example 2 of the present invention.
[0031] Figure 13 This is a TEM diagram of the product obtained in Example 3 of the present invention.
[0032] Figure 14 The images show the Raman spectra of samples prepared using different methods in this invention.
[0033] Figure 15 The N2 adsorption-desorption curves are shown for samples prepared by different methods in this invention. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0035] See Figure 1 This application provides a method for preparing a structure-preserving graphitized porous carbon material, comprising the following steps: Lignite and potassium salt were mixed and ball-milled to obtain a uniformly mixed powder; The mixed powder is preheated to obtain a preheated product, and the preheated product is acid-washed, washed, separated and dried to obtain a sheet-like porous precursor. The sheet-like porous precursor is processed within a defined temperature and time window to cause the carbon skeleton in the sheet-like porous precursor to undergo ordered rearrangement, thereby obtaining a structure-preserving graphitized porous carbon material.
[0036] Specifically, the potassium salt includes potassium carbonate and potassium chloride.
[0037] The total mass ratio of lignite to potassium salt is 1:10, and the molar ratio of potassium carbonate to potassium chloride is 1:1 to 7:3.
[0038] The ball milling time is 4 hours, and the particle size of the uniformly mixed powder obtained after ball milling is 100 mesh to 300 mesh.
[0039] The preheating treatment is performed at a temperature of 750°C for 5 hours.
[0040] The pickling is performed using hydrochloric acid solution; the washing is performed sequentially using deionized water and ethanol; the drying temperature is 65-75℃, and the drying time is 12 hours.
[0041] The specified temperature and time window are: processing temperature of 1300-1700℃ and processing time of 40 seconds.
[0042] The concentration of the hydrochloric acid solution used for pickling is 0.5–2 mol / L.
[0043] It should be noted that the lignite used in the following embodiments is a commercially available raw material; the potassium carbonate (K2CO3), potassium chloride (KCl), hydrochloric acid (HCl), deionized water, ethanol, etc., used are all commercially available analytical grade reagents. The ball mill, tube furnace, rapid Joule heating equipment, etc., used are all conventional equipment in the chemical / materials field, and their models and operating parameters do not constitute a limitation on this application.
[0044] Example 1 This embodiment provides a method for preparing a structure-preserving graphitized porous carbon material.
[0045] S1, 2g of lignite and 20g of potassium salt are mixed, wherein the potassium salt is composed of K2CO3 and KCl in a molar ratio of 5:3. The mixture is placed in a ball mill and ball-milled at 350 rpm for 4 hours, and then sieved to obtain a uniform mixed powder with a particle size of 200 mesh. The above-mentioned mixed powder was placed in a tube furnace and preheated at 750°C for 5 hours to obtain a preheated product. The preheated product was added to 1 mol / L hydrochloric acid and stirred for 2 hours for acid washing. Then it was washed with deionized water and ethanol successively until neutral. Finally, it was dried at 70°C for 12 hours to obtain a sheet-like porous precursor.
[0046] The aforementioned sheet-like porous precursor was transferred to a rapid Joule heating apparatus and heated to 1300°C within 40 seconds for processing, causing a rapid and orderly rearrangement of the carbon skeleton in the sheet-like porous precursor. After natural cooling to room temperature, a structure-preserving graphitized porous carbon material was obtained.
[0047] like Figure 2 As shown, the precursor of the present invention has a two-dimensional sheet-like porous morphology. Figure 3 As shown, after rapid Joule heat treatment at 1300℃, the resulting product still maintains a complete sheet-like porous structure, with no obvious shrinkage or collapse, indicating that the method of the present invention has good structure preservation ability.
[0048] like Figure 6 As shown, impurities in the precursor have been effectively removed, with S and Si contents of only 0.29% and 0.23%, respectively. Figure 7 As shown, after acid washing and rapid Joule heat treatment at 1300℃, the S and Si elements in the product of Example 1 were further removed, proving that the acid washing, washing and heat treatment process of the present invention has a good purification effect.
[0049] like Figure 11 As shown in the TEM image of the product of Example 1, obvious lattice stripes appear in local areas, indicating that the carbon skeleton has undergone local ordered rearrangement and the material has a certain degree of graphitization.
[0050] like Figure 14 As shown in the Raman spectrum, the G peak and G′ peak of the product of Example 1 are significantly clearer than those of the precursor, and the D peak and G peak gradually separate, indicating that the degree of graphitization is significantly improved compared with the precursor.
[0051] like Figure 15 As shown in the N2 adsorption-desorption curve, the specific surface area of the precursor was 1553.49 m² / g, and the specific surface area of the product of Example 1 was 1452.64 m² / g. The specific surface area retention rate was approximately 93.5%, indicating that the material still maintained a high specific surface area after rapid Joule heat treatment at 1300℃.
[0052] Example 2 This embodiment is basically the same as Embodiment 1, except that the temperature of the rapid Joule heat treatment is adjusted to 1500℃.
[0053] A sheet-like porous precursor was prepared using the same method as in Example 1. The obtained precursor was transferred to a rapid Joule heating apparatus and heated to 1500°C within 40 seconds for treatment. It was then allowed to cool naturally to room temperature to obtain the product.
[0054] like Figure 4 As shown, after rapid Joule heat treatment at 1500℃, the resulting product still retains a two-dimensional lamellar porous morphology, similar to... Figure 2 The precursor shown and Figure 3 Compared to the product of Example 1, the edges of the sheets are slightly shrunken, but the overall skeletal structure remains intact.
[0055] like Figure 8 As shown, the impurity elements in the product of Example 2 were basically removed, indicating that the high-temperature treatment at 1500℃ will not introduce pollution, and that it has a good purification effect when combined with the acid washing process.
[0056] like Figure 12 As shown in the TEM image of the product of Example 2, the lattice fringes are clearer and more continuous than those of Example 1, indicating that the carbon atom rearrangement is more complete at 1500°C and the degree of graphitization is further improved.
[0057] like Figure 14 As shown in the Raman spectrum, the G peak and G′ peak of the product in Example 2 are sharper and more symmetrical, and the ID / IG value is significantly lower than that in Example 1, indicating that the crystallinity and graphitization degree of the material are significantly improved.
[0058] like Figure 15 As shown in the N2 adsorption-desorption curve, the specific surface area of the product in Example 2 was tested to be 1289.78 m² / g, compared to the precursor's 1553.49 m² / g. The specific surface area retention rate was approximately 83.0%, which is still at a high level (≥1000 m² / g).
[0059] Example 3 This embodiment is basically the same as Embodiment 1, except that the temperature of the rapid Joule heat treatment is adjusted to 1700℃.
[0060] A sheet-like porous precursor was prepared using the same method as in Example 1. The obtained precursor was transferred to a rapid Joule heating apparatus and heated to 1700°C within 40 seconds for treatment. It was then allowed to cool naturally to room temperature to obtain the product.
[0061] like Figure 5 As shown, after rapid Joule heat treatment at 1700℃, the obtained product still retains a two-dimensional lamellar porous morphology, similar to... Figure 2 The precursor shown Figure 3 The product of Example 1 shown Figure 4 Compared to the product of Example 2, some holes collapsed and cracked, but the overall skeleton structure remained intact.
[0062] like Figure 9 As shown, the impurity elements in the product of Example 3 were basically removed, indicating that the high-temperature treatment at 1700℃ will not introduce pollution, and that it has a good purification effect when combined with the acid washing process.
[0063] like Figure 13 As shown in the TEM image of the product of Example 3, the lattice fringes are clearer and more continuous than those of Examples 1 and 2, and the coverage area is larger, indicating that the carbon atom rearrangement is more complete at 1700°C and the degree of graphitization is further improved.
[0064] like Figure 14 As shown in the Raman spectrum, the G peak and G′ peak of the product in Example 3 are sharper and more symmetrical, the D peak is further weakened, and the ID / IG value is significantly lower than that in Example 1 and Example 2, indicating that the crystallinity and graphitization degree of the material are significantly improved.
[0065] like Figure 15 As shown in the N2 adsorption-desorption curve, the specific surface area of the product in Example 3 was tested to be 947.0453 m² / g, compared with the specific surface area of the precursor of 1553.49 m² / g, and the specific surface area retention rate was about 60.9%, which is still at a high level.
[0066] Comparative analysis of the results of Examples 1, 2 and 3: Figure 3 and Figure 4 and Figure 5 SEM images of the products from Examples 1, 2, and 3 are shown respectively, and... Figure 2 As can be seen from the comparison of the precursors shown, the materials maintained the two-dimensional lamellar porous structure of the precursors at all three heat treatment temperatures, indicating that the method of the present invention has good structure preservation ability.
[0067] Figure 11 , Figure 12 and Figure 13 TEM photos and Figure 14 The Raman spectra show that as the heat treatment temperature increases from 1300℃ to 1500℃ and then to 1700℃, the lattice fringes of the material become clearer, the G peak becomes sharper, and the degree of graphitization gradually increases.
[0068] Figure 15 The N2 adsorption-desorption curves and test data show that the specific surface area retention rates of Examples 1, 2 and 3 are 93.5%, 83.0% and 60.9% respectively, all higher than 60%, indicating that the method of the present invention can effectively inhibit pore structure shrinkage and specific surface area decrease while improving the degree of graphitization.
[0069] Figures 6 to 9The EDS spectrum shows that impurities in lignite are effectively removed after preheating, acid washing and rapid Joule heat treatment, proving that the post-processing process of the present invention is reliable and effective.
[0070] The above embodiments and experimental analysis demonstrate that this invention successfully resolves the contradiction between "rapid graphitization" and "maintaining porous structure." The prepared material possesses both a high specific surface area (≥900 m² / g, retention rate ≥60%) and a high degree of graphitization, and exhibits a stable two-dimensional sheet-like porous structure. This method utilizes widely available raw materials and has a simple process flow, showing promising application prospects in energy storage, catalyst supports, and adsorption separation.
[0071] In another embodiment provided in this application, a structure-preserving graphitized porous carbon material prepared by the above-described preparation method is provided.
[0072] Specifically, the structure-preserving graphitized porous carbon material exhibits a two-dimensional sheet-like porous structure with a specific surface area of 900–2000 m² / g. This material was prepared using the methods described in Examples 1, 2, or 3 above, and its morphology and pore structure characteristics were characterized by scanning electron microscopy and nitrogen adsorption-desorption testing.
[0073] like Figure 2 , Figure 3 , Figure 4 Figure 5 As shown, regardless of the preparation method used in Example 1, Example 2, or Example 3, the resulting products all maintain a two-dimensional sheet-like porous morphology. Figure 2 The image shows a typical sheet-like porous structure of the precursor. Figure 3 The image shows the SEM image of the product from Example 1, where the sheet-like porous structure is well preserved. Figure 4 The image shows the SEM image of the product from Example 2, where the sheet-like porous structure remains intact. Figure 5 The image shows a SEM image of the product from Example 3, where the sheet-like porous structure remains largely intact. These results demonstrate that the porous carbon material prepared in this application possesses a stable two-dimensional sheet-like porous morphology.
[0074] like Figure 15 As shown in the N2 adsorption-desorption curves, the specific surface area of the product in Example 1 was 1452.64 m² / g, the specific surface area of the product in Example 2 was 1289.78 m² / g, and the specific surface area of the product in Example 3 was 947.0453 m² / g. All of these figures fall within the range of 900–2000 m² / g. Therefore, the specific surface area of the structure-preserving graphitized porous carbon material described in this application can reach 900–2000 m² / g.
[0075] Furthermore, the specific surface area retention rate of the structure-preserving graphitized porous carbon material relative to the sheet-like porous precursor is not less than 60%.
[0076] In summary, the structure-preserving graphitized porous carbon material prepared by the above-described method provides a two-dimensional sheet-like porous structure with a specific surface area of 900–2000 m² / g and a specific surface area retention rate of not less than 60% relative to the precursor. This product combines high specific surface area and high degree of graphitization, showing promising application prospects in fields such as supercapacitors, lithium-ion batteries, catalyst supports, and gas adsorption and separation.
[0077] The above-described embodiments are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.
Claims
1. A method for preparing a structure-preserving graphitized porous carbon material, characterized in that, Includes the following steps: Lignite and potassium salt were mixed and ball-milled to obtain a uniformly mixed powder; The mixed powder is preheated to obtain a preheated product, and the preheated product is acid-washed, washed, separated and dried to obtain a sheet-like porous precursor. The sheet-like porous precursor is processed within a defined temperature and time window to cause the carbon skeleton in the sheet-like porous precursor to undergo ordered rearrangement, thereby obtaining a structure-preserving graphitized porous carbon material.
2. The method for preparing a structure-preserving graphitized porous carbon material according to claim 1, characterized in that, The potassium salts include potassium carbonate and potassium chloride.
3. The method for preparing a structure-preserving graphitized porous carbon material according to claim 2, characterized in that, The total mass ratio of lignite to potassium salt is 1:10, and the molar ratio of potassium carbonate to potassium chloride is 1:1 to 7:
3.
4. The method for preparing a structure-preserving graphitized porous carbon material according to claim 1, characterized in that, The ball milling time is 4 hours, and the particle size of the uniformly mixed powder obtained after ball milling is 100 mesh to 300 mesh.
5. The method for preparing a structure-preserving graphitized porous carbon material according to claim 1, characterized in that, The preheating treatment is performed at a temperature of 750°C for 5 hours.
6. The method for preparing a structure-preserving graphitized porous carbon material according to claim 1, characterized in that, The pickling is performed using hydrochloric acid solution; the washing is performed sequentially using deionized water and ethanol; the drying temperature is 65-75℃, and the drying time is 12 hours.
7. The method for preparing a structure-preserving graphitized porous carbon material according to claim 1, characterized in that, The specified temperature and time window are: processing temperature of 1300-1700℃ and processing time of 40 seconds.
8. The method for preparing a structure-preserving graphitized porous carbon material according to claim 6, characterized in that, The concentration of the hydrochloric acid solution used for pickling is 0.5–2 mol / L.
9. A structure-preserving graphitized porous carbon material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The structure-preserving graphitized porous carbon material exhibits a two-dimensional sheet-like porous structure with a specific surface area of 900–2000. .
10. The structure-preserving graphitized porous carbon material according to claim 9, characterized in that, The specific surface area retention rate of the structure-preserving graphitized porous carbon material relative to the sheet-like porous precursor is not less than 60%.