Preparation method and application of nitrogen-rich biomass in-situ nitrogen-doped activated carbon
By utilizing a combination of nitrogen-rich biomass and ordinary biomass in the carbonization process of nitrogen-doped activated carbon preparation, uniform doping of nitrogen is achieved, solving the problems of complexity and pollution associated with traditional methods. This improves the performance of activated carbon, reduces costs, and enables the efficient utilization of biomass waste.
Patent Information
- Application Number
- CN202511820614.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-02-10
AI Technical Summary
Existing methods for preparing nitrogen-doped activated carbon are complex, costly, and may cause environmental pollution. Traditional exogenous in-situ doping methods are difficult to control the uniform distribution of nitrogen.
Using nitrogen-rich biomass as the nitrogen source, it is loaded with ordinary biomass in a specific ratio, and the temperature and time are controlled during the carbonization process to achieve in-situ uniform doping of nitrogen, avoiding the addition of external chemical reagents and simplifying the process.
Activated carbon with uniform nitrogen distribution was prepared, improving its performance and stability, reducing costs, and achieving high-value-added conversion of biomass waste in a green and environmentally friendly manner.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of activated carbon technology, specifically relating to a method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass and its application. Background Technology
[0002] Activated carbon is widely used due to its high specific surface area and tunable pore structure. However, traditional activated carbon, without modification, has a relatively inert surface chemistry, limiting the performance of electrochemical devices (such as supercapacitors) made from it. Studies have shown that introducing heteroatoms (such as nitrogen atoms) into the carbon framework can effectively change the electron distribution of carbon materials, enhancing their surface polarity, conductivity, and chemical activity, thereby significantly improving their electrochemical and catalytic performance.
[0003] Currently, the main methods for preparing nitrogen-doped activated carbon include post-treatment and in-situ doping. Post-treatment involves first preparing activated carbon and then introducing nitrogen atoms through post-treatment. This method is complex, energy-intensive, and results in low nitrogen content, with the nitrogen mainly concentrated on the product surface and unevenly distributed. In-situ doping involves adding nitrogen dopants (such as ammonia or urea) to a carbon-containing precursor and directly carbonizing it. While in-situ doping can achieve uniform nitrogen doping through the carbonization process, traditional exogenous in-situ doping methods require the addition of additional nitrogen-containing chemical reagents, leading to high preparation costs, difficulty in control, and potential environmental pollution. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a method for preparing nitrogen-doped activated carbon that is simple in process, low in cost, and without the addition of exogenous nitrogen.
[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass, comprising the following steps:
[0006] S1. Raw material pretreatment: ordinary biomass is dried and crushed to obtain first raw material powder; nitrogen-rich biomass is dried and crushed to obtain second raw material powder; the ordinary biomass is a biomass raw material with a nitrogen content of <1 wt%, and the nitrogen-rich biomass is a biomass raw material with a nitrogen content of ≥4 wt%.
[0007] S2. Powder filling: Weigh the first raw material powder as the top layer and the second raw material powder as the bottom layer according to a mass ratio of 1:1 to 1.2, and fill them into the carbonization container to form an upper and lower filling structure.
[0008] Alternatively, the first raw material powder as the bottom layer, the second raw material powder as the middle layer, and the first raw material powder as the top layer are weighed out according to a mass ratio of 1:(2~2.5):1, and then filled into the carbonization container in the vertical direction to form a sandwich filling structure.
[0009] S3. Carbonization treatment: The filled powder is heated to 250±10℃ for pre-carbonization for 30 to 35 minutes, and then heated to 530 to 580℃ for carbonization for 60 to 90 minutes to obtain nitrogen-doped activated carbon.
[0010] Furthermore, the common biomass is at least one of sawdust, straw, rice husk, and corn cob;
[0011] And / or, the nitrogen-rich biomass is at least one of soybean residue, shrimp shells, crab shells, and waste silkworm cocoons.
[0012] Furthermore, in step S1, both ordinary biomass and nitrogen-rich biomass are dried to a moisture content of less than 10%.
[0013] Furthermore, the particle size of the first raw material powder is 50-200 mesh;
[0014] The particle size of the second raw material powder is 50-200 mesh.
[0015] Furthermore, in step S3, the heating rate is controlled to be 5–10 °C / min.
[0016] Furthermore, the preparation method also includes step S4;
[0017] S4. Mixing: Mix the prepared nitrogen-doped activated carbon evenly.
[0018] This invention also provides in-situ nitrogen-doped activated carbon from nitrogen-rich biomass, prepared by the above-mentioned method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass, having a nitrogen content of 3-5 wt% and a specific surface area of 150-200 m². 2 / g.
[0019] This invention also provides the application of the above-mentioned nitrogen-rich biomass in-situ nitrogen-doped activated carbon in electrochemical components or catalysts.
[0020] The beneficial effects of this invention are as follows: The preparation method provided by this invention uses ordinary biomass as the main carbon-containing precursor and nitrogen-rich biomass as the nitrogen source, placing it in the bottom or middle layer. Utilizing the differences in the pyrolysis characteristics of various components of biomass, cellulose and hemicellulose are preferentially decomposed and carbonized in the pre-carbonization stage, constructing a primary carbon layer with abundant internal channels, while effectively retaining the protein in the nitrogen-rich biomass. In the subsequent carbonization stage, the protein and lignin undergo synergistic pyrolysis, releasing a large amount of nitrogen-containing volatiles. These volatiles are captured and anchored during diffusion, especially upward diffusion, when they cross-link with the carbon layer and lignin, thereby achieving in-situ nitrogen doping. This preparation method not only makes the nitrogen element more uniformly distributed in the carbon skeleton, improving the performance and stability of activated carbon, but also eliminates the need for external chemical reagents, simplifying the process and significantly reducing preparation costs. Furthermore, by utilizing the widely available nitrogen-rich biomass, high-value-added conversion of biomass waste is achieved, and the process is green and environmentally friendly.
[0021] The technical effects brought about or directly generated by other technical features of the present invention will be described in detail in the following detailed description section. Attached Figure Description
[0022] Figure 1 This is a process flow diagram of one embodiment of the method of the present invention;
[0023] Figure 2 This is a process flow diagram of another embodiment of the method of the present invention. Detailed Implementation
[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0025] In the description of this invention, it should be understood that the terms "about," "around," etc., when used to describe numerical ranges, generally indicate an allowable error within ±2%. The nitrogen content of biomass is typically characterized as a dry-basis mass percentage. The term "multiple" indicates two or more. The term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist, for example: A and / or B, which can represent: A alone, A and B simultaneously, or B alone. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0026] Combination Figure 1 As shown, a method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass includes the following steps:
[0027] S1. Raw material pretreatment: Ordinary biomass is dried and crushed to obtain the first raw material powder; nitrogen-rich biomass is dried and crushed to obtain the second raw material powder; ordinary biomass is a biomass raw material with a nitrogen content of <1 wt%, mainly used as a carbon-containing precursor; ordinary biomass is usually one or more of sawdust, straw, rice husk, and corn cob; nitrogen-rich biomass is a biomass raw material with a nitrogen content of ≥4 wt%, mainly utilizing its own nitrogen element as a nitrogen source; nitrogen-rich biomass is usually one or more of soybean residue, shrimp shells, crab shells, and silkworm cocoon waste silk;
[0028] S2. Powder filling: Weigh the first raw material powder as the top layer and the second raw material powder as the bottom layer according to a mass ratio of 1:1 to 1.2, and fill them into the carbonization container to form an upper and lower filling structure.
[0029] Alternatively, the first raw material powder as the bottom layer, the second raw material powder as the middle layer, and the first raw material powder as the top layer are weighed out according to a mass ratio of 1:(2~2.5):1, and then filled into the carbonization container in the vertical direction to form a sandwich filling structure.
[0030] Among them, the carbonization container can be a carbonization furnace, carbonization tank, pyrolysis tube, etc. During the filling process, it is usually filled and compacted at the same time to reduce the porosity between powder particles and prolong the residence time of nitrogen-containing gas in the carbon layer.
[0031] S3. Carbonization treatment: The packed powder is heated to 250±10℃ for pre-carbonization for 30-35 minutes, and then heated to 530-580℃ for carbonization for 60-90 minutes to obtain nitrogen-doped activated carbon. Since the decomposition temperature of proteins in nitrogen-rich biomass is usually around 250-400℃, the pre-carbonization stage uses reasonable temperature control to decompose and carbonize cellulose and hemicellulose in biomass, forming a primary carbon layer with abundant internal pores, while the proteins in nitrogen-rich biomass hardly decompose and are mostly retained. In the subsequent carbonization process, the proteins and lignin are synergistically pyrolyzed, releasing a large amount of nitrogen-containing volatiles (nitrogen-containing gases such as NH3). These volatiles are captured and anchored when they cross-link with the carbon layer and lignin during diffusion, especially upward diffusion, thereby achieving in-situ nitrogen doping.
[0032] This preparation method not only makes the nitrogen element more evenly distributed in the carbon skeleton, improving the performance and stability of activated carbon, but also simplifies the process and significantly reduces the preparation cost by eliminating the need for external chemical reagents. In addition, it realizes the high-value-added transformation of biomass waste through the resource utilization of widely available nitrogen-rich biomass, and is green and environmentally friendly.
[0033] In some embodiments, step S1 involves drying both ordinary biomass and nitrogen-rich biomass to a moisture content of less than 10%, preferably to a moisture content of less than 5%, to facilitate subsequent nitrogen doping.
[0034] Preferably, in step S1, ordinary biomass is crushed into powder with a particle size of 50-200 mesh; nitrogen-rich biomass is also crushed into powder with a particle size of 50-200 mesh. Biomass powder with this particle size can ensure good heat transfer uniformity and has a large specific surface area, which is beneficial to improving heat and mass transfer efficiency.
[0035] In some embodiments, step S3 is performed under an inert atmosphere. Nitrogen is preferably used as the inert atmosphere gas.
[0036] Preferably, in step S3, the heating rate is controlled at 5-10℃ / min to facilitate the formation of the internal pore structure of the carbon layer and to improve the effect of subsequent carbonization and nitrogen doping.
[0037] Combination Figure 2 As shown, in some embodiments, the preparation method further includes step S4; S4, mixing: the nitrogen-doped activated carbon is mixed evenly.
[0038] This invention also provides in-situ nitrogen-doped activated carbon from nitrogen-rich biomass, prepared by the above-mentioned method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass, having a nitrogen content of 3-5 wt% and a specific surface area of 150-200 m². 2 / g.
[0039] The aforementioned nitrogen-rich biomass in-situ nitrogen-doped activated carbon possesses excellent electrochemical and catalytic properties, and can be used to manufacture electrochemical components such as supercapacitors and fuel cells, or to produce catalysts.
[0040] Comparative Example 1
[0041] The process of preparing biochar using crab shells as biomass raw material is as follows:
[0042] S1. Raw material pretreatment: The crab shells are dried and crushed, and then passed through a 100-mesh sieve to obtain crab shell powder;
[0043] S2. Powder filling: Weigh the crab shell powder and fill it into the pyrolysis tube;
[0044] S3. Carbonization treatment: The filled powder is heated to 550℃ at a heating rate of 10℃ / min and carbonized for 60 min to obtain biochar.
[0045] S4. Mix well: Mix the prepared biochar evenly.
[0046] The mixed biochar was tested, and CO2 adsorption was performed at room temperature and pressure. The results showed that the nitrogen content was 5.6 wt% and the specific surface area was 69 m². 2 / g, CO2 adsorption capacity is 0.7 mmol / g. See Table 1 below for details.
[0047] Comparative Example 2
[0048] The process of preparing biochar using sawdust as a biomass raw material is as follows:
[0049] S1. Raw material pretreatment: The wood chips are dried and crushed, and then passed through a 100-mesh sieve to obtain wood chip powder;
[0050] S2. Powder filling: Weigh the wood chip powder and fill it into the pyrolysis tube;
[0051] S3. Carbonization treatment: The filled powder is heated to 550℃ at a heating rate of 10℃ / min and carbonized for 60 min to obtain biochar.
[0052] S4. Mix well: Mix the prepared biochar evenly.
[0053] The mixed biochar was tested, and CO2 adsorption was performed at room temperature and pressure. The results showed that the nitrogen content was 0.3 wt% and the specific surface area was 248 m². 2 / g, CO2 adsorption capacity is 0.6 mmol / g. See Table 1 below for details.
[0054] Comparative Example 3
[0055] Nitrogen-doped activated carbon was prepared using nitrogen-rich biomass as the top layer and ordinary biomass as the bottom layer, as follows:
[0056] S1. Raw material pretreatment: Wood chips are selected as ordinary biomass, dried and crushed, and passed through a 100-mesh sieve to obtain the first raw material powder; crab shells are selected as nitrogen-rich biomass, dried and crushed, and passed through a 100-mesh sieve to obtain the second raw material powder.
[0057] S2. Powder filling: Weigh the first raw material powder as the bottom layer and the second raw material powder as the top layer at a mass ratio of 1:1, and fill them into the pyrolysis tube to form an upper and lower filling structure.
[0058] S3. Carbonization treatment: The filled powder is heated to 250℃ at a heating rate of 5℃ / min for pre-carbonization for 30 min, and then heated to 550℃ at a heating rate of 10℃ / min for carbonization for 60 min to obtain nitrogen-doped activated carbon.
[0059] S4. Mixing: Mix the prepared nitrogen-doped activated carbon evenly.
[0060] The nitrogen-doped activated carbon was tested after mixing and CO2 adsorption was performed at room temperature and pressure. The results showed that the nitrogen content was 2.9 wt% and the specific surface area was 142 m². 2 / g, CO2 adsorption capacity is 0.6 mmol / g. See Table 1 below for details.
[0061] Example 1
[0062] The method of this invention for preparing nitrogen-doped activated carbon is as follows:
[0063] S1. Material pretreatment: Wood chips are selected as ordinary biomass, dried and crushed, and passed through a 100-mesh sieve to obtain the first raw material powder; crab shells are selected as nitrogen-rich biomass, dried and crushed, and passed through a 100-mesh sieve to obtain the second raw material powder.
[0064] S2. Powder filling: Weigh the first raw material powder as the bottom layer, the second raw material powder as the middle layer, and the first raw material powder as the top layer according to the mass ratio of 1:2:1, and fill them into the pyrolysis tube in the vertical direction to form a sandwich filling structure.
[0065] S3. Carbonization treatment: The filled powder is heated to 250℃ at a heating rate of 8℃ / min for pre-carbonization for 30 min, and then heated to 550℃ at a heating rate of 10℃ / min for carbonization for 70 min to obtain nitrogen-doped activated carbon.
[0066] S4. Mixing: Mix the prepared nitrogen-doped activated carbon evenly.
[0067] The nitrogen-doped activated carbon was tested after mixing and CO2 adsorption was performed at room temperature and pressure. The results showed that the nitrogen content was 3.5 wt% and the specific surface area was 196 m². 2 / g, CO2 adsorption capacity is 1.1 mmol / g. See Table 1 below for details.
[0068] Example 2
[0069] The method of this invention for preparing nitrogen-doped activated carbon is as follows:
[0070] S1. Material pretreatment: Wood chips are selected as ordinary biomass, dried and crushed, and passed through a 100-mesh sieve to obtain the first raw material powder; crab shells are selected as nitrogen-rich biomass, dried and crushed, and passed through a 100-mesh sieve to obtain the second raw material powder.
[0071] S2. Powder filling: Weigh the first raw material powder as the top layer and the second raw material powder as the bottom layer at a mass ratio of 1:1, and fill them in the pyrolysis to form an upper and lower filling structure.
[0072] S3. Carbonization treatment: The filled powder is heated to 250℃ at a heating rate of 5℃ / min for pre-carbonization for 30 min, and then heated to 550℃ at a heating rate of 10℃ / min for carbonization for 60 min to obtain nitrogen-doped activated carbon.
[0073] S4. Mixing: Mix the prepared nitrogen-doped activated carbon evenly.
[0074] The nitrogen-doped activated carbon after mixing was tested, and CO2 adsorption was performed at room temperature and pressure. The results showed that the nitrogen content was 3.1 wt% and the specific surface area was 164 m². 2 / g, CO2 adsorption capacity is 0.9 mmol / g. See Table 1 below for details.
[0075] Table 1: Detection data and CO2 adsorption data of the derived carbons prepared in Comparative Examples 1-3 and Examples 1-2
[0076]
[0077] According to Comparative Examples 1-3, Examples 1-2, and Table 1, the nitrogen-rich biomass in-situ nitrogen-doped activated carbon prepared by the method of the present invention has a high specific surface area and good CO2 adsorption effect; moreover, it has a high nitrogen content and the nitrogen element is uniformly doped in the carbon skeleton, exhibiting excellent electrochemical and catalytic performance. It can be used as a high-performance electrode material in electrochemical devices or as a catalyst support in catalysts.
Claims
1. A method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass, characterized in that, Includes the following steps: S1. Raw material pretreatment: ordinary biomass is dried and crushed to obtain first raw material powder; nitrogen-rich biomass is dried and crushed to obtain second raw material powder; the ordinary biomass is a biomass raw material with a nitrogen content of <1 wt%, and the nitrogen-rich biomass is a biomass raw material with a nitrogen content of ≥4 wt%. S2. Powder filling: Weigh the first raw material powder as the top layer and the second raw material powder as the bottom layer according to a mass ratio of 1:1 to 1.2, and fill them into the carbonization container to form an upper and lower filling structure. Alternatively, the first raw material powder as the bottom layer, the second raw material powder as the middle layer, and the first raw material powder as the top layer are weighed out according to a mass ratio of 1:(2~2.5):1, and then filled into the carbonization container in the vertical direction to form a sandwich filling structure. S3. Carbonization treatment: The filled powder is heated to 250±10℃ for pre-carbonization for 30 to 35 minutes, and then heated to 530 to 580℃ for carbonization for 60 to 90 minutes to obtain nitrogen-doped activated carbon.
2. The method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass according to claim 1, characterized in that: The common biomass is at least one of sawdust, straw, rice husks, and corn cobs; And / or, the nitrogen-rich biomass is at least one of soybean residue, shrimp shells, crab shells, and waste silkworm cocoons.
3. The method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass according to claim 1, characterized in that: In step S1, both ordinary biomass and nitrogen-rich biomass are dried to a moisture content of less than 10%.
4. The method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass according to claim 1, characterized in that: The particle size of the first raw material powder is 50-200 mesh; The particle size of the second raw material powder is 50-200 mesh.
5. A method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass according to any one of claims 1 to 4, characterized in that: In step S3, the heating rate is controlled to be 5-10℃ / min.
6. The method for preparing in-situ nitrogen-doped activated carbon from nitrogen-rich biomass according to claim 5, characterized in that: It also includes step S4; S4. Mixing: Mix the prepared nitrogen-doped activated carbon evenly.
7. A nitrogen-doped activated carbon from nitrogen-rich biomass, characterized in that: The activated carbon prepared by the method for in-situ nitrogen-doped activated carbon from nitrogen-rich biomass according to any one of claims 1 to 6 has a nitrogen content of 3-5 wt% and a specific surface area of 150-200 m². 2 / g.
8. The application of the nitrogen-rich biomass in-situ nitrogen-doped activated carbon as described in claim 7 in electrochemical components or catalysts.