Biomass super activated carbon and preparation method thereof

Abstract

This invention relates to the field of activated carbon preparation technology and discloses a biomass super activated carbon and its preparation method, comprising the following steps: S1, removing impurities, drying and pulverizing biomass raw materials to obtain pretreated biomass raw materials; S2, adjusting and homogenizing the composition of the pretreated biomass raw materials to obtain a homogeneous precursor, thereby reducing the impact of biomass raw material composition fluctuations on subsequent carbonization and activation processes. This invention, by adjusting and homogenizing the composition of biomass raw materials, can reduce the impact of differences in cellulose, hemicellulose, lignin and ash content among different raw materials on the carbonization and activation processes, which is beneficial for forming a more stable carbon skeleton and reducing localized excessive ablation during subsequent activation. This allows the obtained biomass super activated carbon to maintain a reasonable pore size distribution and high product yield even under high specific surface area conditions, improving the stability of the preparation process and the consistency of the product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of activated carbon preparation, in particular to a biomass super activated carbon and a preparation method thereof. BACKGROUND

[0002] Biomass raw materials have wide sources and low cost, and have application potential for preparing super activated carbon. The prior art usually adopts chemical activation or physical activation to increase the specific surface area and pore development degree. However, due to the large difference in cellulose, hemicellulose, lignin and ash content of different biomass raw materials, the reaction degree is inconsistent in the activation process, which leads to the lack of stability of the pore structure. In order to obtain a high specific surface area, the prior art often relies on strong corrosive or large amount of activating agent and high activation intensity, which not only causes problems such as equipment corrosion, complex waste liquid treatment and rising preparation cost, but also easily causes excessive ablation of the carbon skeleton, thereby leading to low yield, unreasonable pore size distribution and large fluctuation of product performance. The above problems further make it difficult for the obtained super activated carbon to simultaneously have high specific surface area, reasonable pore structure and high yield. Therefore, it is necessary to provide a biomass super activated carbon and a preparation method thereof, which can reduce the dependence on activating agent, reduce the burden of post-treatment, and stably control the pore structure under fluctuation of raw materials, so as to realize the technical effects of more stable preparation process, more uniform product performance, higher yield and lower environmental burden. SUMMARY

[0003] (I) Technical problems solved

[0004] In view of the deficiencies of the prior art, the present application provides a biomass super activated carbon and a preparation method thereof, which has the advantages of enabling the obtained biomass super activated carbon to maintain a reasonable pore size distribution and a high product yield under a high specific surface area condition, improving the stability of the preparation process and the consistency of the product, and solving the above problems.

[0005] (II) Technical solutions

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: a preparation method of a biomass super activated carbon, comprising the following steps:

[0007] S1, removing impurities, drying and crushing the biomass raw material to obtain a pretreated biomass raw material;

[0008] S2, adjusting the composition and homogenizing the pretreated biomass raw material to obtain a homogenized precursor, so as to reduce the influence of the fluctuation of the composition of the biomass raw material on the subsequent carbonization and activation process;

[0009] S3, pre-carbonizing the homogenized precursor under an inert atmosphere to obtain a biomass carbon precursor;

[0010] S4, activating the biomass charcoal precursor by contacting the biomass charcoal precursor with a composite activation system to obtain an activated product, the composite activation system comprising a mild chemical activation component and a pore structure regulation component, the mild chemical activation component being used for chemical activation of the biomass charcoal precursor, and the pore structure regulation component being used for regulation of pore expansion behavior in the activation process to form a pore structure with synergistic distribution of micropores and mesopores;

[0011] S5, washing, filtering and drying the activated product to obtain the biomass super activated carbon.

[0012] Preferably, the biomass raw material is selected from one or at least two of agricultural and forestry waste, fruit shell raw material, wood raw material, straw raw material, bamboo raw material and fruit core raw material.

[0013] Preferably, in S1, the moisture content of the biomass raw material after the drying treatment is not higher than 12%, and the particle size of the biomass raw material after the crushing treatment is 20 to 100 mesh.

[0014] Preferably, in S2, the composition adjustment and homogenization treatment comprises at least one of ash adjustment, volatile matter adjustment, lignocellulosic component balance, screening and mixing, stirring and soaking, and standing homogenization.

[0015] Preferably, in S3, the temperature of the pre-carbonization treatment is 300 to 600°C, and the holding time is 0.5 to 3 hours.

[0016] Preferably, the mild chemical activation component is selected from one or at least two of carbonates, bicarbonates, phosphates and organic acid salts, and the pore structure regulation component is selected from one or at least two of water vapor, carbon dioxide and nitrogen carrying oxidizing medium.

[0017] Preferably, in S4, the temperature of the activation treatment is 650 to 900°C, the activation time is 0.5 to 4 hours, and the mass ratio of the biomass charcoal precursor to the mild chemical activation component is 1:0.2 to 1:2.

[0018] Preferably, in S5, the washing treatment comprises at least one of water washing and neutral or weakly acidic washing liquid washing, and the washing is performed until the pH value of the filtrate is 6 to 8.

[0019] A biomass super activated carbon having a hierarchical pore structure with synergistic distribution of micropores and mesopores.

[0020] Preferably, the specific surface area of the biomass super activated carbon is 1500 to 3500 m² / g, the total pore volume is 0.8 to 2.5 cm³ / g, and the micropore volume accounts for 50% to 90% of the total pore volume.

[0021] Compared with the prior art, the biomass super activated carbon and the preparation method have the following beneficial effects:

[0022] 1、 The biomass raw material is subjected to composition adjustment and homogenization treatment, so that the influence of the differences in cellulose, hemicellulose, lignin and ash content of different raw materials on the carbonization and activation process is reduced, the problems of unstable reaction, uneven pore structure formation and obvious product performance fluctuation caused by large fluctuation of raw materials in the prior art are solved, and on this basis, the pre-carbonization treatment is combined, which is beneficial to forming a stable carbon skeleton and reducing the local excessive ablation in the subsequent activation process, so that the obtained biomass super activated carbon can still maintain a reasonable pore size distribution and a high product yield under the condition of a high specific surface area, and the stability of the preparation process and the consistency of the product are improved.

[0023] 2、 The mild chemical activation component and the pore structure regulation component are used to synergistically activate, the dependence on the strong corrosive and high dosage activation agent in the prior art is reduced, the problems of equipment corrosion, heavy washing burden and complex post-treatment process are reduced, and at the same time, the pore structure of the obtained activated carbon is formed by regulating the pore expansion behavior in the activation process, which is beneficial to increasing the number of adsorption sites and improving the mass transfer performance, and further improving the comprehensive use performance of the product, so that the biomass super activated carbon preparation process has the technical effects of low environmental burden, good controllability of pore structure and excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flowchart of the present application is shown. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] Please refer to Figure 1 , embodiment 1, a preparation method of biomass super activated carbon, comprising the following steps:

[0027] S1, raw material pretreatment: coconut shell powder and bamboo chips are selected as biomass raw materials, mixed in a mass ratio of 3:2, first subjected to impurity removal treatment to remove sand, metal impurities and obvious rotten substances; then the mixed raw materials are dried at 105 DEG C for 10 hours to reduce the moisture content to below 10%; the dried raw materials are crushed by a crushing device and sieved through a 40 mesh sieve to obtain pretreated biomass raw materials;

[0028] S2. Composition Adjustment and Homogenization: After thoroughly mixing the pretreated coconut shell powder and bamboo shavings, add deionized water equivalent to 15% of the total mass of the mixed raw materials and stir to soak. After stirring for 30 minutes, let stand for 4 hours to make the fiber components and ash distribution in different raw materials tend to be uniform, thus obtaining a homogeneous precursor. This step is used to reduce the impact of differences in the composition of different biomass raw materials on the consistency of subsequent carbonization and activation reactions.

[0029] S3. Pre-carbonization treatment: The obtained homogeneous precursor is placed in a tube furnace and heated to 450°C under nitrogen protection. It is held at this temperature for 1.5 hours and then cooled to obtain biochar precursor. Pre-carbonization treatment removes some volatiles and forms a more stable initial carbon skeleton to reduce local over-ablation during the subsequent activation process.

[0030] S4. Activation treatment: Mix the obtained biochar precursor with potassium carbonate at a mass ratio of 1:0.8 to obtain pre-activated material; then place the pre-activated material in an activation furnace, heat it to 780°C under nitrogen protection, keep it at that temperature for 1 hour, and introduce steam during the holding period for 40 minutes to carry out synergistic activation, and obtain the activated product.

[0031] Potassium carbonate serves as a mild chemical activating component, while water vapor acts as a pore structure regulating component. Through their synergistic effect, the resulting product forms a hierarchical pore structure dominated by micropores and supplemented by mesopores.

[0032] S5. Post-processing: After the activated product is taken out, it is first washed with deionized water, then washed once with a 3% acetic acid aqueous solution to remove residual inorganic components. Then, it is washed with deionized water until the pH of the filtrate is 7. The washed sample is dried at 110℃ for 8 hours to obtain the biomass super activated carbon product.

[0033] Performance testing: The obtained biomass super activated carbon was tested and found to have a specific surface area of ​​2180 m² / g, a total pore volume of 1.42 cm³ / g, a micropore volume accounting for 72% of the total pore volume, an iodine adsorption value of 1680 mg / g, a methylene blue adsorption value of 286 mg / g, and a product yield of 31.5%. The results indicate that the activated carbon prepared in this example has a high specific surface area, a reasonable pore size distribution, and good yield stability.

[0034] Comparative Example 1:

[0035] A conventional method for preparing biomass activated carbon differs from Example 1 in that it does not involve composition adjustment and homogenization treatment, and the activation stage uses potassium hydroxide as a single activator, without introducing water vapor for pore structure control. The specific process is as follows:

[0036] Coconut shell powder was selected as raw material. After impurity removal, drying and pulverization, it was pre-carbonized at 450℃ for 1.5 hours under nitrogen protection. The obtained carbon precursor was mixed with potassium hydroxide at a mass ratio of 1:2 and activated at 800℃ for 1 hour. After activation, it was washed with water and acid until neutral, and then dried to obtain activated carbon product.

[0037] Testing revealed that the comparative product had a specific surface area of ​​2310 m² / g and a total pore volume of 1.56 cm³ / g, but the product yield was only 21.8%, and the pore volume fluctuated significantly between batches. The proportion of micropores was high, the mesopore connectivity was poor, and the methylene blue adsorption performance was unstable. In addition, when potassium hydroxide was used for activation, the waste liquid in the washing process was highly alkaline, resulting in a heavy post-treatment burden.

[0038] As can be seen from the above embodiments and comparative examples, in the prior art, due to the large differences in the composition of biomass raw materials and the reliance on highly corrosive and large-volume activators for high-intensity activation, problems such as excessive ablation of the carbon skeleton, decreased yield, unstable pore structure, and heavy post-processing burden are easily caused. To address this problem, the present invention reduces the impact of raw material fluctuations on the consistency of carbonization and activation reactions by adjusting and homogenizing the composition of biomass raw materials; at the same time, it uses mild chemical activation components and pore structure regulating components for synergistic activation, reducing the dependence on highly corrosive activators and improving the controllability of the pore structure formation process. As a result, the obtained biomass super activated carbon maintains a high specific surface area while possessing a more reasonable distribution of micropores and mesopores, higher product yield, and more stable batch consistency, thereby achieving the technical effects of stable preparation process, lower environmental impact, and superior overall product performance.

[0039] Example 2, a method for preparing biomass super activated carbon, comprising the following steps:

[0040] S1. Raw material pretreatment: Corn straw powder and peanut shell powder are selected as biomass raw materials and mixed at a mass ratio of 1:1. First, remove mud, sand, stones and other impurities, and then dry at 100℃ for 8 hours to reduce the moisture content of the raw materials to below 11%. The dried raw materials are crushed and passed through a 60-mesh sieve to obtain pretreated biomass raw materials.

[0041] S2. Composition adjustment and homogenization treatment: Add deionized water equivalent to 12% of the total mass of the raw materials to the pretreated mixed raw materials, stir for 25 minutes and let stand for 5 hours to make the components in the straw and nut shell raw materials more evenly distributed and obtain a homogeneous precursor. This step reduces the reaction differences of different types of biomass raw materials in the subsequent pyrolysis process.

[0042] S3. Pre-carbonization treatment: The homogeneous precursor is placed in an inert atmosphere and heated to 420°C at a heating rate of 10°C per minute. The temperature is maintained for 2 hours and then cooled to obtain the biochar precursor.

[0043] S4. Activation treatment: Mix biochar precursor and potassium bicarbonate at a mass ratio of 1:0.6. After mixing evenly, place the mixture in an activation furnace and heat it to 750℃ under nitrogen protection and keep it at that temperature for 1.5 hours. In the later stage of activation, introduce carbon dioxide for 30 minutes to expand the pores and obtain the activated product.

[0044] Potassium bicarbonate is used to provide a mild chemical activation effect, while carbon dioxide is used to regulate the pore expansion process, so that the resulting activated carbon forms a more balanced microporous and mesoporous structure.

[0045] S5. Post-treatment: The activated product is repeatedly washed with deionized water, then washed once with a 2% citric acid aqueous solution, and then washed with deionized water until the pH of the filtrate is 6.8 to 7.2. Finally, it is dried at 105℃ for 10 hours to obtain the biomass super activated carbon product.

[0046] Performance testing: The obtained biomass super activated carbon had a specific surface area of ​​1965 m² / g, a total pore volume of 1.31 cm³ / g, a micropore volume accounting for 68% of the total pore volume, an iodine adsorption value of 1525 mg / g, a methylene blue adsorption value of 274 mg / g, and a product yield of 33.2%.

[0047] Test results show that even with a high proportion of straw-based raw materials, this embodiment still achieves a high specific surface area and a good pore structure matching relationship, as well as a high product yield, indicating that the technical solution has good adaptability to differences in raw materials.

[0048] Example 3, a method for preparing biomass super activated carbon, comprising the following steps:

[0049] S1. Raw material pretreatment: Apricot kernel shell powder and sawdust are selected as biomass raw materials, mixed at a mass ratio of 2:3, and impurities are removed. The raw materials are then dried at 110℃ for 9 hours to reduce the moisture content to below 9%. After drying, the raw materials are pulverized and passed through a 50-mesh sieve to obtain pretreated biomass raw materials.

[0050] S2. Composition adjustment and homogenization treatment: The pretreated raw materials are thoroughly mixed and sprayed with deionized water equivalent to 10% of the total mass of the raw materials. After stirring for 20 minutes, the mixture is allowed to stand for 6 hours to improve the homogeneity of the mixture and obtain a homogeneous precursor.

[0051] S3. Pre-carbonization treatment: The homogeneous precursor is heated to 480℃ under a nitrogen atmosphere and held for 1 hour. After cooling, the biochar precursor is obtained. By appropriately increasing the pre-carbonization temperature, the volatile matter in the raw material is further removed and the stability of the carbon skeleton is enhanced.

[0052] S4. Activation treatment: The biochar precursor and potassium phosphate are mixed at a mass ratio of 1:0.5 and placed in an activation device. Under nitrogen protection, the temperature is raised to 820℃ and kept at that temperature for 50 minutes. During the holding period, water vapor is introduced for 20 minutes for synergistic activation to obtain the activated product.

[0053] Potassium phosphate is used for mild activation, and water vapor is used to promote pore penetration and expansion to improve mesoporous connectivity.

[0054] S5. Post-processing: The obtained activated product is first washed with water, then washed once with a 3% acetic acid solution, and then washed with water until the pH of the filtrate is 7. Finally, it is dried at 110℃ for 6 hours to obtain the biomass super activated carbon product.

[0055] Performance testing: The obtained biomass super activated carbon was tested and found to have a specific surface area of ​​2058 m² / g, a total pore volume of 1.47 cm³ / g, a micropore volume of 64% of the total pore volume, an iodine adsorption value of 1590 mg / g, a methylene blue adsorption value of 301 mg / g, and a product yield of 30.8%.

[0056] The results show that even when using different types of mild chemically activated components, this embodiment can still obtain a better specific surface area and hierarchical pore structure, indicating that the present invention has good process adjustability.

[0057] As demonstrated in Examples 1 to 3, this invention is not limited to a single biomass raw material or a single activation system, but is applicable to the individual or combined use of various biomass raw materials such as fruit shells, straw, wood, and fruit kernels. Due to differences in cellulose, hemicellulose, lignin, and ash content among different biomass raw materials, directly employing conventional high-intensity activation methods can easily lead to uneven carbonization reactions, severe localized ablation, uncontrolled pore structure formation, and decreased product yield. To address these issues, this invention first reduces reaction variations caused by raw material fluctuations through composition adjustment and homogenization treatment. Then, through the synergistic effect of mild chemical activation components and pore structure regulating components, the pore structure formation process is regulated in stages, thereby reducing over-activation.

[0058] The test results of each embodiment show that the biomass super activated carbon prepared by this invention can maintain a high pore volume and a reasonable distribution of micropores and mesopores on a high specific surface area, while maintaining a high product yield. Compared with conventional methods that rely solely on highly corrosive activators for activation, this invention not only reduces equipment corrosion and post-processing burdens but also improves the performance stability between product batches. This achieves the technical effect of stably preparing biomass super activated carbon with high specific surface area, reasonable pore structure, and high yield under fluctuating raw material conditions.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing biomass super activated carbon, characterized in that, Includes the following steps: S1. The biomass raw material is subjected to impurity removal, drying and pulverization to obtain pretreated biomass raw material; S2. The pretreated biomass raw materials are subjected to composition adjustment and homogenization treatment to obtain homogeneous precursors, so as to reduce the impact of biomass raw material composition fluctuations on subsequent carbonization and activation processes. S3. The homogeneous precursor is pre-carbonized under an inert atmosphere to obtain biochar precursor. S4. The biochar precursor is contacted with the composite activation system for activation treatment to obtain the activation product. The composite activation system includes a mild chemical activation component and a pore structure regulating component. The mild chemical activation component is used to chemically activate the biochar precursor, and the pore structure regulating component is used to regulate the pore expansion behavior during the activation process to form a pore structure in which micropores and mesopores are distributed in a coordinated manner. S5. The activated product is washed, filtered and dried to obtain biomass super activated carbon.

2. The method for preparing biomass super activated carbon according to claim 1, characterized in that: The biomass raw materials are selected from one or at least two of the following: agricultural and forestry waste, fruit shells, wood, straw, bamboo, and fruit pits.

3. The method for preparing biomass super activated carbon according to claim 1, characterized in that: In S1, the moisture content of the biomass raw material after drying is not higher than 12%, and the particle size of the biomass raw material after pulverization is 20 mesh to 100 mesh.

4. The method for preparing biomass super activated carbon according to claim 1, characterized in that: In S2, the composition adjustment and homogenization treatment includes at least one of ash adjustment, volatile matter adjustment, wood fiber component balancing, sieving and mixing, stirring and impregnation, and static homogenization.

5. The method for preparing biomass super activated carbon according to claim 1, characterized in that: In S3, the temperature of the pre-carbonization treatment is 300°C to 600°C, and the holding time is 0.5 hours to 3 hours.

6. The method for preparing biomass super activated carbon according to claim 1, characterized in that: The mild chemical activating component is selected from one or at least two of carbonates, bicarbonates, phosphates, and organic acid salts, and the pore structure regulating component is selected from one or at least two of water vapor, carbon dioxide, and nitrogen-carrying oxidation media.

7. The method for preparing biomass super activated carbon according to claim 1, characterized in that: In S4, the activation treatment temperature is 650°C to 900°C, the activation time is 0.5 hours to 4 hours, and the mass ratio of the biochar precursor to the mild chemically activated component is 1:0.2 to 1:

2.

8. The method for preparing biomass super activated carbon according to claim 1, characterized in that: In S5, the washing process includes at least one of water washing and washing with a neutral or weakly acidic washing solution, and the washing is continued until the pH value of the filtrate is 6 to 8.

9. A biomass super activated carbon, characterized in that: The biomass super activated carbon is prepared by any one of the preparation methods described in claims 1 to 8, and has a hierarchical pore structure with micropores and mesopores distributed in a coordinated manner.

10. The biomass super activated carbon according to claim 9, characterized in that: The biomass super activated carbon has a specific surface area of ​​1500 m² / g to 3500 m² / g, a total pore volume of 0.8 cm³ / g to 2.5 cm³ / g, and micropores account for 50% to 90% of the total pore volume.

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