Preparation method and application of natural asphalt-based porous carbon

Abstract

The invention discloses a preparation method and an application of natural asphalt-based porous carbon. The preparation method comprises the following steps: preparing natural asphalt-based porous carbon; the preparation method comprises the following steps: (1) uniformly mixing natural asphalt powder and biomass powder, and kneading into raw material balls; (2) the raw material balls are placed in an air atmosphere for pre-oxidation, and after pre-oxidation is finished, a material A is obtained; (3) uniformly mixing the material A with an activating agent, and performing high-temperature carbonization in a reaction kettle to obtain a material B after the high-temperature carbonization is finished; and (4) sequentially carrying out acid pickling and filter pressing on the material B, carrying out low-temperature calcination on a filter cake obtained by filter pressing in a reducing atmosphere, and after the low-temperature calcination is finished, preparing the natural asphalt-based porous carbon. The natural asphalt-based porous carbon prepared by the method is large in specific surface area and smooth in pore structure surface, and pore size distribution mainly comprises micropores and mesopores.

Description

Technical Field

[0001] This invention relates to the field of porous carbon preparation technology. Specifically, it relates to a method for preparing and applying natural pitch-based porous carbon. Background Technology

[0002] Porous carbon materials, due to their high specific surface area, rich pore structure, and excellent chemical stability, have shown significant application value in fields such as energy storage (e.g., supercapacitors) and environmental remediation (pollutant adsorption). Traditional porous carbon preparation often uses fossil resources such as coal and petroleum coke as raw materials, but controlling their pore structure is difficult, and the activation process can easily generate environmental pollution.

[0003] In recent years, the technology of preparing porous carbon from natural bitumen has gradually emerged. Natural bitumen, due to its abundant carbon precursors and natural pore structure, is considered one of the ideal precursors for carbon materials. However, the preparation of natural bitumen-based porous carbon in existing technologies still suffers from problems such as poor pore uniformity, insufficient specific surface area, and high production costs, which limit its application and promotion in high-value-added fields. Therefore, developing a method to precisely control process parameters through natural bitumen modification to prepare high-performance porous carbon has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing and applying natural bitumen-based porous carbon, so as to solve the problems of poor pore uniformity, insufficient specific surface area and high production cost of existing bitumen-based porous carbon.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A method for preparing natural pitch-based porous carbon includes the following steps;

[0007] Step (1): Mix the natural asphalt powder and biomass powder evenly and knead them into raw material balls. Mixing the two raw materials and kneading them into raw material balls can improve the bonding degree between the two different raw materials and increase the density of subsequent carbon materials. On the other hand, the spherical structure has good stability and high bulk density, which is conducive to improving production capacity. Moreover, the uniform spherical structure can make the contact area between each raw material ball and the air the same, which is conducive to ensuring the consistency of the degree of oxidation crosslinking of the raw materials during the pre-oxidation process. If the natural asphalt powder and biomass powder are mixed and pre-oxidized directly, it is difficult to control the degree of pre-oxidation crosslinking and may lead to a large difference in the degree of oxidation crosslinking of the raw materials in the same batch of pre-oxidation treatment.

[0008] Step (2): Place the raw material balls in an air atmosphere for pre-oxidation. After the pre-oxidation is completed, material A is obtained. The pre-oxidation achieves a close combination of natural asphalt powder and biomass powder, inducing the formation of abundant oxygen functional groups. That is, during the pre-oxidation process, oxygen elements are embedded in the molecular chains of asphalt and biomass to form oxygen-containing functional groups such as hydroxyl (-OH) and carboxyl (-COOH). In particular, the oxygen-containing functional groups introduced by asphalt during the pre-oxidation process can connect unsaturated aliphatic hydrocarbons and aromatic hydrocarbon side chains to form a disordered carbon skeleton.

[0009] Step (3): After mixing material A with the activator evenly, place it in the reaction vessel for high-temperature carbonization. After the high-temperature carbonization is completed, material B is obtained.

[0010] Step (4): The material B is acid washed and pressure filtered in sequence. The filter cake obtained by pressure filtration is calcined at low temperature in a reducing atmosphere. After the low temperature calcination is completed, natural asphalt-based porous carbon is obtained. The impurities in the porous carbon can be effectively removed by acid washing and low temperature calcination, and a smooth porous carbon structure surface is obtained.

[0011] Existing technologies for preparing asphalt-based porous carbon typically involve first subjecting biomass feedstock to alkali activation and pre-carbonization separately before mixing it with asphalt for carbonization. In contrast, this invention directly mixes biomass feedstock and asphalt, performs pre-oxidation together, adds an activator for carbonization and alkali activation, and finally performs acid washing and low-temperature calcination in a reducing atmosphere. This significantly improves the uniformity of the biomass carbon and asphalt carbon mixture in the final porous carbon. Furthermore, during the co-oxidation process of biomass and asphalt, biomass acts as a solid framework to inhibit the softening and accumulation of asphalt, increasing the contact area between asphalt and air, thereby significantly improving the pre-oxidation effect. It also facilitates the effective removal of impurity atoms from the porous carbon surface during high-temperature carbonization followed by acid washing and low-temperature calcination in a reducing atmosphere, repairing surface defects and forming a more stable porous carbon structure. This invention involves pre-oxidizing, alkali-activating, and carbonizing a mixture of biomass and asphalt raw materials, followed by acid washing and low-temperature calcination in a reducing atmosphere. This process effectively removes impurity atoms from the surface of porous carbon, repairs surface defects, and forms a more stable porous carbon structure. Acid washing removes metal ions and silicon atoms, while calcination removes non-metallic impurities such as H, O, N, and S. Without low-temperature calcination, the resulting porous carbon exhibits numerous surface defects, an unstable pore structure, and an uneven surface. Furthermore, the presence of impurities negatively impacts the functional applications of the porous carbon; for example, in energy storage, the purity of porous carbon typically needs to be above 98%.

[0012] This invention involves directly mixing biomass raw materials and asphalt, then pre-oxidizing them together, adding an activator for carbonization and alkali activation, and finally acid washing and low-temperature calcination in a reducing atmosphere. This process allows the biomass raw materials and asphalt to introduce abundant oxygen-containing functional groups through oxidative cross-linking. During the carbonization and alkali activation processes, a disordered carbon skeleton and a microporous-mesoporous hierarchical structure are formed. Furthermore, the surface defects of the porous carbon are repaired through acid washing and low-temperature calcination in a reducing atmosphere, resulting in a stable microporous-mesoporous hierarchical porous carbon structure with smooth pores.

[0013] Compared to pre-oxidation followed by alkali activation, this invention adds alkali as an activator after pre-oxidation and simultaneously performs alkali activation during high-temperature carbonization, offering the following advantages: After pre-oxidation, natural asphalt undergoes oxidative cross-linking, increasing its softening point, which facilitates uniform mixing of the material and the activator. Asphalt and biomass raw materials are more prone to forming micropores after oxidative cross-linking; mixing with the activator at this stage during carbonization allows the activator to play a certain pore-forming role (primarily participating in the formation of mesopores), which is beneficial for increasing the material's porosity and forming a hierarchical pore structure. Furthermore, simultaneous high-temperature carbonization of the material and activator in a sealed reactor eliminates the need for a protective atmosphere, facilitating exhaust gas collection and treatment, saving costs, and effectively enhancing the reaction efficiency between the activator and the material under high pressure and high temperature, reducing carbon emissions and promoting energy conservation and environmental protection.

[0014] In the above-mentioned method for preparing natural bitumen-based porous carbon, in step (1), the particle size of the natural bitumen powder is less than or equal to 0.150 mm; the particle size of the biomass powder is less than or equal to 0.038 mm; the smaller particle size is beneficial to the uniform mixing of the two; the diameter of the raw material spheres is 2-5 mm, and the density of the raw material spheres is 1.2-2.0 g / cm³. 3 If the density of the raw material spheres is too high (above 2.0 g / cm³), 3 If the diameter of the raw material spheres is too large, it will hinder air from entering the interior of the spheres and affect the pre-oxidation effect; if the diameter of the raw material spheres is too small, energy consumption will be high and production capacity will be low; if the density of the raw material spheres is less than 1.2 g / cm³... 3 If the asphalt and biomass are not tightly bonded, and the asphalt carbon and biomass carbon are not uniformly combined, the density of the final carbon material will decrease.

[0015] In the above-mentioned method for preparing porous carbon based on natural asphalt, in step (1), the mass ratio of natural asphalt powder to biomass powder is 1:(4-10); the biomass powder is one or a mixture of two or more of palm shell powder, straw powder, peanut shell powder, or starch (starch is preferred because it undergoes significant expansion during carbonization, which is beneficial for forming more pores, and the porous carbon prepared by mixing with natural asphalt has better overall performance). If the mass ratio of natural asphalt powder to biomass powder is too low, the biomass as a skeleton will not play an obvious role in inhibiting the softening and rearrangement of asphalt, resulting in a decrease in pore-forming efficiency; since the density of asphalt carbon is higher than that of biomass carbon, if the mass ratio of the two is too high, the density of the carbon material finally prepared will decrease. This invention, by controlling the ratio of natural asphalt powder to biomass powder within an appropriate range, is beneficial for constructing porous carbon with an ideal hierarchical pore structure and density.

[0016] In the above-mentioned method for preparing porous carbon based on natural asphalt, step (2) involves pre-oxidation: heating to 250-300℃ at a heating rate of 0.2-1.0℃ / min, and pre-oxidizing at 250-300℃ for 4-8 hours; then naturally cooling to room temperature. During pre-oxidation, if the heating rate is too fast, the asphalt will soften rapidly, making it difficult to maintain the spherical structure of the raw material spheres and increasing the difficulty of subsequent processes. If the pre-oxidation temperature is too high, the raw material spheres may spontaneously combust; if the pre-oxidation temperature is too low, the oxidative crosslinking effect of natural asphalt and biomass powder will be poor. By controlling the heating rate, pre-oxidation temperature, and pre-oxidation time of pre-oxidation, this invention can introduce abundant oxygen-containing functional groups into natural asphalt and biomass, improve the oxidative crosslinking effect of asphalt and biomass, and facilitate the formation of a disordered carbon skeleton.

[0017] In the above-mentioned method for preparing natural asphalt-based porous carbon, in step (3), the mass ratio of material A to activator is 1:(4-8), and the activator is one or a mixture of two or more of potassium hydroxide, sodium hydroxide, sodium carbonate, or potassium carbonate, preferably potassium hydroxide. The mechanism of potassium hydroxide (KOH) in activation and pore-forming reactions is the most complex, mainly including the following steps: (1) Dehydration reaction: 2KOH → K2O + H2O; (2) Water gas reaction: C + H2O → H2 + CO; (3) Water gas transfer reaction: CO + H2O → H2 + CO2; (4) Carbonate formation: K2O + CO2 → K2CO3; (5) Metallic potassium formation (high temperature stage): K2O reacts with H2 or carbon to generate metallic potassium vapor (K2O + H2 → 2K + H2O; K2O + C → 2K + CO); (6) Pore expansion and etching: KOH selectively consumes carbon atoms to form micropores and widen the pore size. At the same time, metallic potassium vapor is squeezed into the micropores and between the graphite layers. During the catalytic activation process, KOH activation energy generates a high specific surface area (up to 3000). Activated carbon with a density of m² / g or higher and a well-developed pore structure is highly corrosive and can easily lead to pore collapse and equipment corrosion, so its usage must be strictly controlled. Sodium hydroxide (NaOH) acts as a pore-forming agent primarily by corroding amorphous regions in the carbon framework to create pores. At high temperatures, NaOH decomposes to produce Na₂O and H₂O. Na₂O reacts with carbon to generate sodium vapor and CO. The sodium vapor is then forced into the carbon structure, leaving pores upon cooling. NaOH is less corrosive than KOH, but the resulting pore structure is less developed, with a specific surface area typically in the range of 1000-1500 m² / g. Sodium carbonate (Na₂CO₃), on the other hand, primarily decomposes at high temperatures to produce Na₂O. Na₂O reacts with carbon to generate sodium vapor and CO. The sodium vapor is then forced into the carbon structure, leaving pores upon cooling. Because Na₂CO₃ has lower reactivity than KOH and NaOH, it requires higher activation temperatures (typically 800-1000℃). Although the resulting pore structure is more uniform, the specific surface area is relatively low (500-1000 m² / g). Potassium carbonate (K₂CO₃) also plays a role. The reaction mechanism is similar to that of Na2CO3 but milder. Its reaction temperature is lower than that of K2CO3 (700-900℃), and the resulting pore structure is uniform with a specific surface area between 800-1500 m² / g.

[0018] If the amount of activator (such as potassium hydroxide) is too small, its pore-forming effect during the high-temperature carbonization process will be insignificant, resulting in insufficient porosity of the prepared porous carbon material. If the amount is too large, it will not only increase costs and be detrimental to subsequent acid washing processes, but also easily lead to pore collapse. This invention, by strictly controlling the ratio of material A to activator (such as potassium hydroxide) and controlling the process parameters of high-temperature carbonization and low-temperature calcination within a reasonable range, can regulate the pore structure of the final porous carbon, enabling it to form a microporous-mesoporous hierarchical pore structure.

[0019] In the above-mentioned method for preparing natural asphalt-based porous carbon, step (3) involves high-temperature carbonization: heating to 800-1000℃ at a heating rate of 5-10℃ / min, and carbonizing at 800-1000℃ for 3-8 hours; then naturally cooling to room temperature; the filling volume of the reactor is 70-90%. If the carbonization temperature is higher than 1000℃, not only will energy consumption be high and costs increase, but the pore structure will also easily collapse. If the carbonization temperature is lower than 800℃, the pore-forming effect of the activator will be poor, the porosity of the carbon material will decrease, and the pore hierarchical structure will be unsatisfactory. If the material filling volume of the reactor is too low, the material combustion problem will easily occur, leading to a decrease in carbon yield. If the material filling volume of the reactor is too high, the pore-forming effect of biomass / asphalt cracking gas on the carbon material cannot be fully utilized, thereby affecting the porosity and pore structure of the porous carbon material. The reactor in this invention is a closed pressure-resistant reactor. Under conditions of high filling coefficient and rapid generation of cracked gas, an inert or reducing atmosphere is formed inside the reactor, thereby preventing the oxidation and combustion of materials.

[0020] In the above-mentioned method for preparing natural asphalt-based porous carbon, in step (4), the pickling solution is a mixed acid solution of hydrochloric acid and hydrofluoric acid, and the mass fraction of hydrochloric acid in the mixed acid solution is 25-35wt%, and the mass fraction of hydrofluoric acid is 8-15wt%. The pickling method is as follows: material B and pickling solution are mixed and stirred evenly at a mass-volume ratio of (4-8) g / mL, the stirring speed is 20-60 rpm, and the stirring time is 3-5 h. The pressure filtration method is as follows: the mixture after pickling is placed under a pressure filtration condition of 0.6-2.0 MPa.

[0021] In the above-mentioned method for preparing natural asphalt-based porous carbon, step (4) involves low-temperature calcination as follows: the filter cake is directly transferred to a reducing atmosphere at 350-500℃ without drying, and calcined at 350-500℃ for 1-4 hours; then naturally cooled to room temperature; the reducing atmosphere is a mixed reducing atmosphere formed by hydrogen and argon at a flow rate ratio of 1:(10-19). Directly transferring the filter cake to a reducing atmosphere for low-temperature calcination without drying not only simplifies the process and increases production capacity, but also allows the vaporization of residual moisture during low-temperature calcination to help form a more uniform pore distribution. Under these calcination conditions, reducing gases (such as CO and H2) can react with oxides or oxygen-containing functional groups on the porous carbon surface to effectively remove surface oxides, impurity atoms, and reduce interfacial impurities. Furthermore, under these conditions, the disordered carbon structure is rearranged through atomic migration to form a more complete graphite microcrystalline structure. Edge defect sites are repaired through carbon atom diffusion, thus repairing the defects on the porous carbon surface and forming a more stable porous carbon structure with smooth pores and a microporous-mesoporous hierarchical pore structure.

[0022] In the above method for preparing natural bitumen-based porous carbon, in step (1), the natural bitumen powder is passed through a 100-mesh sieve; the biomass powder is passed through a 400-mesh sieve; the diameter of the raw material balls is 3 mm, and the density of the raw material balls is equal to 1.5 g / cm³. 3 The mass ratio of natural bitumen powder to biomass powder is 1:4; the biomass powder is palm shell powder.

[0023] In step (2), the pre-oxidation method is as follows: the temperature is increased to 280℃ at a heating rate of 0.5℃ / min, and pre-oxidized at 280℃ for 6 hours; then it is naturally cooled to room temperature.

[0024] In step (3), the mass ratio of material A to activator is 1:4, and the activator is potassium hydroxide; the high-temperature carbonization method is as follows: the temperature is increased to 900℃ at a heating rate of 6℃ / min, and carbonized at 900℃ for 4 hours; then it is naturally cooled to room temperature; the filling volume of the reactor is 80%;

[0025] In step (4), the pickling solution is a mixed acid solution of hydrochloric acid and hydrofluoric acid, and the mass fraction of hydrochloric acid in the mixed acid solution is 30wt% and the mass fraction of hydrofluoric acid is 10wt%. The pickling method is: material B and pickling solution are mixed and stirred evenly at a mass-volume ratio of 5g / mL, the stirring speed is 50rpm, and the stirring time is 4h. The pressure filtration method is: the mixed material after pickling is placed under a pressure filtration condition of 1.0MPa. The low-temperature calcination method is: the filter cake is directly transferred to a reducing atmosphere at 400℃ without drying, and calcined at 400℃ for 1-4h. Then it is naturally cooled to room temperature. The reducing atmosphere is a mixed reducing atmosphere formed by hydrogen and argon at a flow rate ratio of 1:15.

[0026] An application of natural pitch-based porous carbon involves using the natural pitch-based porous carbon prepared by the above-mentioned method as a matrix for silicon-carbon composite materials; or using the natural pitch-based porous carbon prepared by the above-mentioned method as an electrode additive for lead-acid or lithium-ion batteries. This not only effectively alleviates the volume expansion problem of electrode materials during charging and discharging due to ion insertion / extraction, thus improving the cycle stability of the electrode; it also effectively improves the interfacial stability between the electrode and the electrolyte, reduces side reactions (such as electrolyte decomposition), and improves the interfacial performance of the electrode; and simultaneously enhances ion transport, thereby improving the rate performance of the battery.

[0027] The technical solution of the present invention achieves the following beneficial technical effects:

[0028] 1. The method for preparing natural asphalt-based porous carbon of the present invention involves first mixing natural asphalt powder and biomass powder of a specific particle size in a specific ratio and kneading them into raw material balls of a specific diameter. Then, the natural asphalt powder and biomass powder are subjected to low-temperature pre-oxidation, high-temperature carbonization with the addition of an activator, acid washing, and low-temperature reduction calcination in the form of raw material balls. By controlling the conditions of low-temperature pre-oxidation, rationally selecting the type and amount of activator, the conditions of high-temperature carbonization, and the conditions of low-temperature reduction calcination, it is possible to prepare natural asphalt-based porous carbon with a large specific surface area, smooth pore structure surface, and pore size distribution mainly consisting of micropores and mesopores.

[0029] 2. The natural pitch-based porous carbon prepared by the method of this invention utilizes natural pitch to provide a stable carbon framework, while biomass contributes to the porous structure. Calcination in a reducing atmosphere effectively repairs the interface of the porous carbon, forming a microporous-mesoporous hierarchical pore structure with smooth pores. When used as an electrode additive in lead-acid or lithium-ion batteries, it not only effectively alleviates the volume expansion problem caused by ion insertion / extraction during charge / discharge, improving the cycle stability of the electrode, but also effectively improves the interfacial stability between the electrode and the electrolyte, reducing side reactions (such as electrolyte decomposition) and enhancing the interfacial performance of the electrode. Simultaneously, it enhances ion transport and improves the rate performance of the battery. Attached Figure Description

[0030] Figure 1 Adsorption-desorption curves of porous carbon prepared in the embodiments of the present invention;

[0031] Figure 2 Pore ​​size distribution characteristic curve of porous carbon prepared in the embodiments of the present invention;

[0032] Figure 3 SEM images of the porous carbon prepared in the embodiments of the present invention;

[0033] Figure 4SEM image of the porous carbon prepared in Comparative Example 1 of this invention;

[0034] Figure 5 SEM image of the porous carbon prepared in Comparative Example 2 of this invention. Detailed Implementation

[0035] Example

[0036] The preparation method of natural bitumen-based porous carbon in this embodiment includes the following steps:

[0037] Step (1): Mix 100g of natural asphalt powder and 400g of biomass powder evenly and knead into raw material balls of 3mm (density 1.5g / cm³). 3 The natural bitumen powder is Nigerian natural bitumen powder, which has passed through a 100-mesh sieve; the biomass powder is palm shell powder that has passed through a 400-mesh sieve.

[0038] Step (2): Place the raw material balls in a muffle furnace and pre-oxidize them in an air atmosphere. The pre-oxidation method is as follows: heat up to 280℃ at a heating rate of 0.5℃ / min and pre-oxidize at 280℃ for 6 hours; then cool naturally to room temperature; after the pre-oxidation is completed, material A is obtained.

[0039] Step (3): Mix 100g of material A with 400g of activator (potassium hydroxide solid powder) evenly, and fill it into a sealed reactor (the filling coefficient in the reactor is 80%) for high-temperature carbonization. The high-temperature carbonization method is as follows: heat up to 900℃ at a heating rate of 6℃ / min, and carbonize at 900℃ for 4h; then cool naturally to room temperature; after the high-temperature carbonization is completed, material B is obtained.

[0040] Step (4): The material B is acid washed and filtered in sequence. The filter cake obtained by filtration is calcined at low temperature in a reducing atmosphere. After the low temperature calcination is completed, natural asphalt-based porous carbon is obtained.

[0041] In this embodiment, the pickling solution used is a mixed acid solution of hydrochloric acid and hydrofluoric acid, with the mass fraction of hydrochloric acid being 30 wt% and the mass fraction of hydrofluoric acid being 10 wt%. The pickling method is as follows: material B and the pickling solution are mixed and stirred evenly at a mass-volume ratio of 5 g / mL, with a stirring speed of 50 rpm and a stirring time of 4 h. The pressure filtration method is as follows: the mixture after pickling is placed under a pressure filter at 1.0 MPa. The low-temperature calcination method is as follows: the filter cake is directly transferred to a reducing atmosphere at 400°C without drying and calcined at 400°C for 2 h; then it is naturally cooled to room temperature. The reducing atmosphere is a mixed reducing atmosphere formed by hydrogen and argon at a flow rate ratio of 1:15.

[0042] like Figure 1It can be seen that the adsorption and desorption curves of the natural pitch-based porous carbon prepared in this embodiment are Type I. The adsorption capacity increases rapidly in the low relative pressure region (P / Po close to 0), indicating that the porous carbon material is rich in micropores (pore size < 2 nm). In addition, there is no obvious "hysteresis loop", indicating that the porous carbon material has a uniform pore structure.

[0043] like Figure 2 The diagram shows the pore size distribution of the natural bitumen-based porous carbon prepared in this embodiment; the specific surface area of ​​the natural bitumen-based porous carbon prepared in this embodiment is 2842 m². 2 / g, with an average pore size of 1.7nm, indicating a high proportion of micropores.

[0044] like Figure 3 The image shows an SEM image of the natural bitumen-based porous carbon prepared in the example; the porous carbon has a three-dimensional interconnected pore structure and a smooth surface.

[0045] Comparative Example 1

[0046] The only difference between this comparative example and the embodiment is that in step (4), material B is not acid washed and pressure filtered, but is directly placed in a reducing atmosphere for low-temperature calcination. The operation methods, raw materials, equipment and process parameters of other steps are exactly the same as those of the embodiment.

[0047] The specific surface area of ​​the natural bitumen-based porous carbon prepared in this comparative example is 1682 m². 2 / g, with an average pore size of 4.2nm. From Figure 4 As can be seen, the porous carbon in Comparative Example 1 has a larger pore size, and the sample contains irregular fragments, which can cause pore blockage.

[0048] Comparative Example 2

[0049] The only difference between this comparative example and the embodiment is that in step (3), material A and potassium hydroxide are mixed at a mass ratio of 1:1, that is, 100g of material A is mixed with 100g of potassium hydroxide. The operation methods, raw materials, equipment and process parameters of other steps are exactly the same as those of the embodiment.

[0050] The specific surface area of ​​the natural bitumen-based porous carbon prepared in this comparative example is 357 m². 2 / g, with an average pore size of 14.6nm. From Figure 5 As can be seen from the data, only a small number of pore structures can be observed in the porous carbon of Comparative Example 2. This is because the amount of activator used is too small, and the sample fails to form a rich microporous structure.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing a natural bitumen-based porous carbon, characterized by, The method comprises the following steps: Step (1), uniformly mixing natural asphalt powder and biomass powder, and then kneading into raw material balls; Step (2), pre-oxidizing the raw material balls in an air atmosphere, and obtaining material A after the pre-oxidation is completed; Step (3), uniformly mixing the material A and an activating agent, and then placing in a reaction kettle for high-temperature carbonization, and obtaining material B after the high-temperature carbonization is completed; Step (4), sequentially performing acid pickling and pressure filtration on the material B, and then low-temperature calcining the filter cake obtained through the pressure filtration in a reducing atmosphere, and obtaining the natural asphalt-based porous carbon after the low-temperature calcination is completed.

2. The method for preparing natural pitch-based porous carbon according to claim 1, characterized by, In step (1), the particle size of the natural asphalt powder is less than or equal to 0.150 mm; the particle size of the biomass powder is less than or equal to 0.038 mm; the diameter of the raw material ball is 2-5 mm, and the density of the raw material ball is 1.2-2.0 g / cm 3 .

3. The method for preparing natural pitch-based porous carbon according to claim 1, characterized in that, In step (1), the mass ratio of the natural asphalt powder to the biomass powder is 1:(4-10); the biomass powder is one or two or more than two of palm shell powder, straw powder, peanut shell powder or starch.

4. The method for preparing natural bitumen-based porous carbon according to claim 1, characterized in that, In step (2), the pre-oxidation method is: increasing the temperature to 250-300°C at a temperature increasing rate of 0.2-1.0°C / min, and pre-oxidizing at 250-300°C for 4-8h; and then naturally cooling to room temperature.

5. The method for preparing natural bitumen-based porous carbon according to claim 1, characterized in that, In step (3), the mass ratio of the material A to the activating agent is 1:(4-8), and the activating agent is one or two or more than two of potassium hydroxide, sodium hydroxide, sodium carbonate or potassium carbonate.

6. The method for preparing natural pitch-based porous carbon according to claim 1, characterized in that, In step (3), the high-temperature carbonization method is: increasing the temperature to 800-1000°C at a temperature increasing rate of 5-10°C / min, and carbonizing at 800-1000°C for 3-8h; and then naturally cooling to room temperature; and the filling volume of the reaction kettle is 70-90%.

7. The method for preparing natural bitumen-based porous carbon according to claim 1, characterized in that, In step (4), the acid pickling solution is a mixed acid solution of hydrochloric acid and hydrofluoric acid, and the mass fraction of the hydrochloric acid in the mixed acid solution is 25-35wt%, and the mass fraction of the hydrofluoric acid is 8-15wt%; The acid pickling method is: uniformly mixing and stirring the material B and the acid pickling solution at a mass-volume ratio of (4-8)g / mL, the stirring rate is 20-60rpm, and the stirring time is 3-5h; The pressure filtration method is: pressure filtering the mixed material after the acid pickling under the condition of 0.6-2.0MPa.

8. The method for preparing natural bitumen-based porous carbon according to claim 1, characterized in that, In step (4), the low-temperature calcination method is: transferring the filter cake to a reducing atmosphere at 350-500°C, and calcining at 350-500°C for 1-4h; and then naturally cooling to room temperature; and the reducing atmosphere is a mixed reducing atmosphere formed by hydrogen and argon at a flow ratio of 1:(10-19).

9. The method for preparing natural bitumen-based porous carbon according to claim 1, characterized in that, In step (1), the natural asphalt powder is passed through a 100-mesh sieve; the biomass powder is passed through a 400-mesh sieve; the diameter of the raw material ball is 3 mm, and the density of the raw material ball is equal to 1.5 g / cm 3 ; the mass ratio of the natural asphalt powder to the biomass powder is 1:4; and the biomass powder is palm shell powder. In step (2), the pre-oxidation method is: increasing the temperature to 280°C at a temperature increasing rate of 0.5°C / min, and pre-oxidizing at 280°C for 6h; and then naturally cooling to room temperature; In step (3), the mass ratio of the material A to the activating agent is 1:4, the activating agent is potassium hydroxide, the high-temperature carbonization method is: increasing the temperature to 900°C at a temperature increasing rate of 6°C / min, and carbonizing at 900°C for 4h; and then naturally cooling to room temperature; and the filling volume of the reaction kettle is 80%. In step (4), the pickling solution is a mixed acid solution of hydrochloric acid and hydrofluoric acid, and the mass fraction of hydrochloric acid in the mixed acid solution is 30wt%, and the mass fraction of hydrofluoric acid is 10wt%; the pickling method is: the material B is mixed and stirred with the pickling solution according to the mass volume ratio of 5g / mL, the stirring rate is 50rpm, and the stirring time is 4h; the pressure filtration method is: the mixed material after pickling is placed under the condition of 1.0MPa for pressure filtration; the low-temperature calcination method is: the filter cake is directly transferred to a reducing atmosphere at 400℃, and calcined at 400℃ for 2h; then naturally cooled to room temperature; the reducing atmosphere is a mixed reducing atmosphere formed by hydrogen and argon according to the flow ratio of 1:

15.

10. Use of natural bitumen-based porous carbon, characterized in that, The natural asphalt-based porous carbon prepared by the preparation method of the natural asphalt-based porous carbon according to any one of claims 1-9 is used as a matrix of silicon-carbon composite material; or the natural asphalt-based porous carbon prepared by the preparation method of the natural asphalt-based porous carbon according to any one of claims 1-9 is used as an electrode additive of lead-acid battery or lead-lithium battery.

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