Biomass carbon sequestration value-added conversion method

Abstract

The invention discloses a biomass carbon sequestration value-added conversion method which comprises the following steps: S1, pyrolyzing cellulose to obtain carbonized cellulose; s2, performing resistance reduction treatment and / or conductive agent addition on the carbonized cellulose to obtain pretreated carbonized cellulose; s3, performing first Joule heat treatment on the pretreated carbonized cellulose to obtain graphitized cellulose of which the resistance is within a preset range; and S4, carrying out second Joule heat treatment on the graphitized cellulose to obtain the biomass graphene. According to the method, cellulose which is a low-cost and renewable biomass raw material is utilized, the Joule heat technology is combined, cellulose is converted into high-value graphene, and the method has remarkable economic benefits and environmental protection advantages. The method is simple, convenient and efficient, high-quality graphene can be produced on a large scale, a low-cost and sustainable production path is provided for industrial application of graphene, and the method has wide application prospects and market value.

Description

Technical Field

[0001] This invention relates to a method for biomass carbon sequestration and value-added conversion, belonging to the field of graphene preparation technology. Background Technology

[0002] Graphene, with its superior electrical and thermal conductivity, strength, and chemical stability, has shown immense application potential in electronics, energy, medicine, aerospace, and other fields. With the increasing demand for high-performance materials, the market demand for graphene is growing rapidly. However, existing graphene production methods present many problems, particularly regarding cost, environmental impact, and resource consumption. Currently, traditional graphene production methods mainly rely on natural graphite or petroleum-based raw materials. These methods typically require processes such as chemical vapor deposition, liquid-phase exfoliation, and chemical reduction, necessitating high-temperature, high-energy-consuming equipment and involving complex chemical processes and expensive catalysts or solvents. Furthermore, the environmental burden of traditional methods is significant, including the use of large amounts of chemical solvents, waste gas emissions, and water consumption.

[0003] Biomass materials, especially cellulose, as a renewable and inexpensive raw material, have become emerging candidate materials for graphene production. Cellulose is not only widely available but also has a high carbon content, providing an ample carbon source for graphene synthesis. Compared to natural graphite, cellulose offers a significant cost advantage as a raw material and effectively avoids over-reliance on limited mineral resources.

[0004] Currently, there are technologies that use cellulose as a raw material to prepare graphene. However, these technologies have the following defects and shortcomings: 1) Some methods use hydrothermal methods for preparation, which are time-consuming and severely restrict the improvement of production efficiency; 2) Some methods require the addition of alkali to mix and calcine with biochar, which will produce by-products. The by-products are then removed by soaking in acid solution, which is a complicated process. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings of the prior art and propose a biomass carbon fixation and value-added conversion method. Without the need to add other auxiliary materials, this method achieves rapid, simple, and large-scale production of highly conductive graphene by regulating the orderliness and defect density of the carbon structure through two-step Joule heating.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A biomass carbon fixation and value-added conversion method includes the following steps: S1, pyrolyzing cellulose to obtain carbonized cellulose; S2, adding a conductive agent to reduce the resistivity of the carbonized cellulose; S3, subjecting the carbonized cellulose after resistivity reduction treatment to a first Joule heat treatment at a first voltage to obtain graphitized cellulose with a resistivity within a preset range; S4, subjecting the graphitized cellulose to a second Joule heat treatment at a second voltage to obtain biomass graphene; wherein the first voltage is lower than the second voltage.

[0008] Furthermore, the pyrolysis in step S1 is carried out under an inert atmosphere; the pyrolysis temperature is set to 300–800℃, the pyrolysis time is 30–120 min, and the pyrolysis heating rate is 5–15℃ / min.

[0009] Furthermore, in step S2, by reducing the resistance of the carbonized cellulose and increasing the current density, a stronger local electric field is generated inside the carbon structure. This electric field can directly drive carbon atoms to align from a disordered state to an ordered graphite layer, and can also reduce the activation energy of the graphitization reaction, so that the phase transitions in steps S3 and S4 can be completed with lower energy input.

[0010] Further, step S2 specifically includes: adding a conductive agent and mixing it with the carbonized cellulose and ball milling it to make the conductive agent evenly distributed on the surface of the carbonized cellulose; then placing the carbonized cellulose in a quartz tube and compressing it with plugs at both ends to reduce the resistance to below a preset resistance value.

[0011] Furthermore, the resistance reduction treatment reduces the resistance of the carbonized cellulose to below 100Ω.

[0012] Furthermore, the conductive agent added in step S2 is carbon black, and the amount of carbon black added is 5 to 20 wt% of the carbonized cellulose.

[0013] Furthermore, in step S3, a low-pressure Joule heating method is used to induce the orientation and π-π stacking of aromatic fragments within the carbon source, partially removing amorphous carbon between the layers to form a graphite-like framework with low electrical resistance but still maintaining a porous network. This framework exhibits an ordered spp structure on a microscopic scale. 2 district.

[0014] Furthermore, in step S3, the DC voltage for the first Joule heat treatment is set to 30–100V, and the discharge time is 1–20s.

[0015] Furthermore, the resistivity of the graphitized cellulose obtained in step S3 is 1 to 5 Ω.

[0016] Furthermore, in step S4, the DC voltage for the second Joule heat treatment is set to 120–200V, and the discharge time is 1–5s.

[0017] The beneficial effects of this invention are mainly reflected in the following aspects: This invention uses inexpensive cellulose as a raw material and applies high voltage directly to cellulose through the Joule heating effect, enabling the production of graphene within seconds. Compared to traditional high-temperature sintering, hydrothermal, and catalytic methods, this not only simplifies the preparation process but also significantly shortens the graphene preparation time (traditional high-temperature sintering and hydrothermal methods require several to tens of hours), thus significantly improving graphene production efficiency. Simultaneously, the Joule heating method of this invention can control the material's resistance through direct current, ensuring the high conductivity of graphene. Particularly in step S2, by reducing the resistance of cellulose and increasing the current density, a stronger local electric field is generated within the carbon structure. This electric field not only directly drives carbon atoms from a disordered state to an ordered graphite layer orientation but also effectively reduces the activation energy of the graphitization reaction, allowing the phase transition to be completed with lower energy input. Therefore, controlling the sample resistance to be low is a key technical means to achieve efficient, rapid, and controllable graphitization.

[0018] Furthermore, in the graphene preparation process, reducing the resistance of the precursor followed by flash Joule heating can impart excellent conductivity and stability to the resulting graphene. Regarding conductivity, the key lies in the synergistic effect of "pre-alignment-rapid graphitization" in two stages of carbon atom arrangement: the initial stage employs low-pressure Joule heating and other methods to induce early orientation and π-π stacking of aromatic fragments within the carbon source, partially removing amorphous carbon between the layers to form a "graphite-like framework" with low resistance yet maintaining a porous network. This framework exhibits long-range ordered spp at the microscopic level. 2 In these regions, the defect density is low, reducing the potential barrier that electron transport needs to overcome, macroscopically manifested as a sharp drop in resistance. When instantaneous high-power Joule heating is performed, the enormous current density rapidly conducts along these partially graphitized, low-resistance channels, generating an extremely high temperature gradient and thermal shock. On the one hand, this instantaneously decomposes residual oxygen-containing groups within milliseconds, releasing them as gas and preventing defect regeneration; on the other hand, the thermal stress promotes sp... 2 The regions further expand and merge along the direction of the electric field, with slippage and reorientation occurring between the layers, ultimately forming a continuous, complete graphene network with large crystal size and orderly interlayer stacking. Due to the low initial resistance, Joule thermal energy is efficiently converted into the activation energy required for graphitization, rather than being dissipated into Joule dissipation in disordered carbon. As a result, defect healing is sufficient, electron migration pathways are unobstructed, and the conductivity of graphene is maximized.

[0019] Furthermore, the method of this invention allows for adjustment of parameters such as voltage and resistance, exhibiting excellent controllability and adaptability. Even under different raw material or environmental conditions, variables such as current and time can be adjusted as needed to ensure high consistency and repeatability of the prepared graphene.

[0020] In a further technical solution of the present invention, cellulose is mixed with a conductive agent (such as carbon black) and a voltage is applied to convert cellulose into graphene by utilizing the Joule heating effect. This can not only significantly reduce production costs, but also reduce carbon dioxide emissions through carbon fixation, providing a feasible way for the green production of graphene.

[0021] In a further technical solution of the present invention, the DC voltage of the first Joule heat treatment is set to 30-100V. The instantaneous energy density applied in this range is just enough to drive the carbonized cellulose to complete the low-temperature graphitization, so that its resistivity is precisely reduced to a set value—low enough to ensure the generation of the required high current density and local electric field during the second flash evaporation step, but not so low as to cause current shielding or local melting; at the same time, this energy window can eliminate oxygen-containing defects and appropriately expand the sp 2 Crystal domains are essential for preserving nucleation sites and suppressing hot cracks in subsequent high-field graphitization. If the voltage deviates from the 30–100V range, insufficient graphitization or decreased conductivity of the final product will result due to resistance mismatch or structural damage. Therefore, the selection of this voltage range is an irreplaceable, reasonable and necessary prerequisite.

[0022] In a further technical solution of the present invention, the DC voltage for the second Joule heat treatment is set to 120–200V. This is because in a flash Joule heat system, the applied voltage directly determines the instantaneous power density and electric field strength, thereby controlling the temperature rise rate, peak temperature, and current-induced graphitization driving force of the carbon precursor. The experimental window of 120–200V is based on the nonlinear trade-off between "graphitization quality and energy input." When the voltage is below 120V, the total energy input is insufficient to simultaneously meet the two kinetic thresholds of "rapid heating" and "defect healing," resulting in insufficient graphitization and significant disorder and micro-strain in the turbine layer. When the voltage exceeds 200V, the excessively high power density triggers two adverse effects: thermal shock and localized overheating cause in-plane tearing and edge curling of the graphene sheets, leading to an increase in lattice defects; the instantaneous peak temperature exceeds 3300℃, intensifying carbon atom volatilization, and graphitized fragments and disordered carbon begin to coexist in the product. Therefore, excessively high voltage not only failed to further improve the degree of order, but also destroyed the formed graphite lattice due to excessive energy injection, causing the product quality to decline. Attached Figure Description

[0023] Figure 1 This is a flowchart of the biomass carbon sequestration and value-added conversion method according to an embodiment of the present invention.

[0024] Figure 2 This is an X-ray diffraction pattern of biomass graphene from Example 1 of the present invention.

[0025] Figure 3 This is a Raman image of the biomass graphene from Example 1 of the present invention.

[0026] Figure 4 This is an X-ray diffraction pattern of biomass graphene from Example 2 of the present invention.

[0027] Figure 5 This is an X-ray diffraction pattern of biomass graphene from Example 3 of the present invention.

[0028] Figure 6 This is the X-ray diffraction pattern of biomass graphene from Example 4 of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The embodiments provided are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0030] This invention provides a method for biomass carbon fixation and value-added conversion, specifically a method for rapidly preparing graphene using cellulose as a raw material through a "two-step Joule heating" process. In this method, cellulose serves as both a carbon source and a carbon fixation carrier, and graphitization is completed within seconds through "two-step Joule heating" to obtain biomass graphene with excellent conductivity and stability.

[0031] Please refer to Figure 1 The biomass carbon sequestration and value-added conversion method provided in this embodiment of the invention specifically includes the following steps S1 to S4:

[0032] Step S1: Pyrolyze cellulose to obtain carbonized cellulose. In this step, pyrolysis must be carried out under an inert atmosphere (such as argon). The preferred pyrolysis temperature is 300–800℃, the pyrolysis time is 30–120 min, and the pyrolysis heating rate is 5–15℃ / min.

[0033] Step S2: Perform a resistance reduction treatment on the carbonized cellulose obtained in step S1. Specifically, add a conductive agent and mix with the carbonized cellulose and ball mill to make the conductive agent evenly distributed on the surface of the carbonized cellulose. Then, place the carbonized cellulose in a quartz tube and compress it with plugs at both ends to reduce the resistance to a preset resistance value (e.g., below 100Ω).

[0034] Step S3: Perform a first Joule heat treatment on the carbonized cellulose after reducing its resistance at a first voltage to obtain graphitized cellulose with a resistance within a preset range.

[0035] Step S4: Perform a second Joule heat treatment on the graphitized cellulose obtained in step S3 under a second voltage to obtain biomass graphene.

[0036] Wherein, the first voltage is lower than the second voltage.

[0037] Before the first Joule heat treatment in step S3, the carbonized cellulose is first subjected to a resistance reduction treatment in step S2 to ensure that the first Joule heat treatment can be carried out efficiently at a low resistance (e.g., ≤100Ω), laying the foundation for obtaining highly conductive graphene subsequently. In a preferred embodiment of the present invention, the method for reducing the resistance of the carbonized cellulose is as follows: a conductive agent, such as carbon black, is first added and mixed with the carbonized cellulose and ball-milled to ensure that the carbon black is evenly distributed on the surface of the carbonized cellulose. Then, the carbonized cellulose is placed in a quartz tube and pressed at both ends with two graphite plugs. During the process, the resistance value is measured, and the resistance is reduced to below 100Ω before the first Joule heat treatment is performed. Preferably, the amount of carbon black added is 5–20 wt% of the carbonized cellulose, more preferably 5–10 wt%.

[0038] In the Joule heat treatment process, the preferred method for applying direct current to the material is as follows: after preparing the material, it is filled into a quartz tube with graphite plugs at both ends, compressed between two copper gaskets to ensure compaction, and then direct current is applied through electrodes. In a specific embodiment, the parameters of the first Joule heat treatment in step S3 can be set as follows: the applied direct current voltage is preferably 30-100V, more preferably 50-100V; the discharge time is preferably 1-20s, more preferably 1-10s.

[0039] During the first Joule heat treatment, the resistance of the material is measured in real time. When the resistance drops to 1–5 Ω, preferably to 1–2 Ω, the treatment can be stopped to obtain graphitized cellulose. In step S4, the graphitized cellulose that meets this resistance range is subjected to a second Joule heat treatment at a higher voltage. Specifically, in step S4, the applied DC voltage is preferably 120–200 V, more preferably 150–200 V; the discharge time is preferably 1–5 s, more preferably 1 s.

[0040] Examples of preparing graphene using the aforementioned method are provided below.

[0041] Example 1

[0042] In this embodiment, the cellulose raw material is first placed in a high-temperature furnace and pyrolyzed under an argon protective atmosphere. The pyrolysis temperature is set at 300°C, the pyrolysis time is 120 minutes, and the heating rate is 5°C / min to ensure that the cellulose is fully carbonized under temperature control, resulting in carbonized cellulose.

[0043] Subsequently, carbon black (10 wt% of carbonized cellulose) was added and mixed, and the mixture was ground in a ball mill for 30 minutes to ensure that the carbon black was evenly distributed on the surface of the carbonized cellulose. After thorough mixing, the sample was filled into a quartz tube, and both ends of the quartz tube were sealed with graphite plugs. Compressive force was applied between two copper gaskets to ensure that the sample was compacted. The resistivity of the compacted sample was 90 Ω.

[0044] Next, a DC voltage was applied through the electrodes to perform the first step of Joule heating, with the voltage set at 80V and the discharge time at 10 seconds. After the initial application of current, the resistance of the sample (graphitized cellulose) was still greater than 2Ω, so the DC current was continued to be applied. After adjustment, the resistance dropped to 1.5Ω, meeting the conditions for further graphitization (second step Joule heating) reaction.

[0045] Subsequently, the graphitized cellulose sample with its resistance reduced to 1.5Ω was subjected to a second Joule heating reaction. By applying a higher DC voltage (180V) and shortening the discharge time to 1 second, the Joule heating effect was used to accelerate the reaction process, ultimately yielding biomass graphene.

[0046] Example 2

[0047] In this embodiment, the cellulose raw material is first placed in a high-temperature furnace and pyrolyzed under an argon protective atmosphere. The pyrolysis temperature is set at 500°C, the pyrolysis time is 60 minutes, and the heating rate is 5°C / min to ensure that the cellulose is fully carbonized under temperature control, resulting in carbonized cellulose.

[0048] Subsequently, carbon black (10 wt% of carbonized cellulose) was added and mixed, and the mixture was ground in a ball mill for 30 minutes to ensure that the carbon black was evenly distributed on the surface of the carbonized cellulose. After thorough mixing, the sample was filled into a quartz tube, and both ends of the quartz tube were sealed with graphite plugs. Compressive force was applied between two copper gaskets to ensure that the sample was compacted. The resistivity of the compacted sample was 99 Ω.

[0049] Next, a DC voltage was applied to the electrodes to initiate the first Joule heating step. The voltage was set to 30V, and the discharge time was 10 seconds. After the initial current was applied, the sample resistance was still greater than 2Ω. Therefore, the DC current was continued to be applied. After adjustment, the resistance dropped to 1.9Ω, which met the conditions for further graphitization reaction.

[0050] Subsequently, the processed graphitized cellulose sample was subjected to a Joule heating reaction. By applying a higher DC voltage (120V) and shortening the discharge time to 1 second, the Joule heating effect was used to accelerate the reaction process, ultimately yielding high-quality biomass graphene.

[0051] The X-ray diffraction test results of the graphene prepared in Example 2 of this invention are shown in... Figure 4 The spectrum shows a clearly broadened (002) diffraction peak with a significantly increased half-width at half-maximum (HWHM), which contrasts sharply with the sharp and narrow (002) peak obtained in Example 1. The broadened peak shape also suggests higher micro-strain or disordered interlayer stacking within the crystal, leading to a shortened coherence length in the diffraction vector direction. In summary, the long-range order of the sample in Example 2 along the (002) crystal plane is significantly lower than that in Example 1, indicating decreased crystal integrity and insufficient graphitization.

[0052] Example 3

[0053] In this embodiment, the cellulose raw material is first placed in a high-temperature furnace and pyrolyzed under an argon protective atmosphere. The pyrolysis temperature is set to 800°C, the pyrolysis time is 120 minutes, and the heating rate is 5°C / min to ensure that the cellulose is fully carbonized under temperature control, resulting in carbonized cellulose.

[0054] Subsequently, carbon black (5 wt% of carbonized cellulose) was added and mixed, and the mixture was ground in a ball mill for 30 minutes to ensure that the carbon black was evenly distributed on the surface of the carbonized cellulose. After thorough mixing, the sample was filled into a quartz tube, and both ends of the quartz tube were sealed with graphite plugs. Compressive force was applied between two copper gaskets to ensure that the sample was compacted. The resistivity of the compacted sample was 87 Ω.

[0055] Next, a direct current was applied through the electrodes, with the voltage set to 100V and the discharge time to 10 seconds. After the initial application of current, the sample resistance was still greater than 2Ω, so the direct current was continued to be applied. After adjustment, the resistance dropped to 1.4Ω, which met the conditions for further graphitization reaction.

[0056] Subsequently, the processed graphitized cellulose sample was subjected to a Joule heating reaction. By applying a higher DC voltage (180V) and shortening the discharge time to 1 second, the Joule heating effect was used to accelerate the reaction process, ultimately yielding high-quality biomass graphene.

[0057] The X-ray diffraction test results of the graphene prepared in Example 3 of this invention are shown in... Figure 5 A distinctly broadened (002) diffraction peak can be observed, and its full width at half maximum (FWHM) after Lorentz-Gaussian peak fitting is significantly larger than the corresponding value in Example 1. Furthermore, the peak position shifts slightly towards the lower angle, corresponding to a larger interlayer spacing, suggesting significant turbine layer disorder and local strain between layers. Considering both peak shape and position, the long-range order and graphitization integrity of the Example 3 sample in the (002) crystal plane normal direction are significantly inferior to those of Example 1.

[0058] Example 4

[0059] In this embodiment, the cellulose raw material is first placed in a high-temperature furnace and pyrolyzed under an argon protective atmosphere. The pyrolysis temperature is set at 300°C, the pyrolysis time is 120 minutes, and the heating rate is 5°C / min to ensure that the cellulose is fully carbonized under temperature control, resulting in carbonized cellulose.

[0060] Subsequently, carbon black (20 wt% of carbonized cellulose) was added and mixed, and the mixture was ground in a ball mill for 30 minutes to ensure that the carbon black was evenly distributed on the surface of the carbonized cellulose. After thorough mixing, the sample was filled into a quartz tube, and both ends of the quartz tube were sealed with graphite plugs. Compressive force was applied between two copper gaskets to ensure that the sample was compacted. The resistivity of the compacted sample was 85 Ω.

[0061] Next, a direct current was applied through the electrodes, with the voltage set to 80V and the discharge time to 10 seconds. After the initial application of current, the sample resistance was still greater than 2Ω, so the direct current was continued to be applied. After adjustment, the resistance dropped to 1.8Ω, which met the conditions for further graphitization reaction.

[0062] Subsequently, the processed graphitized cellulose sample was subjected to a Joule heating reaction. By applying a higher DC voltage (200V) and shortening the discharge time to 1 second, the Joule heating effect was used to accelerate the reaction process, ultimately yielding high-quality biomass graphene.

[0063] The X-ray diffraction test results of the graphene prepared in Example 4 of this invention are shown in... Figure 6 A clearly broadened (002) diffraction peak can be observed, while the diffraction peak of Example 1 is sharp and has a smaller half-width. The increased half-width of the (002) peak in Example 4 is the result of the combined effects of domain refinement, turbine layer disorder and micro-strain, reflecting that its graphitization integrity is lower than that of Example 1.

[0064] The X-ray diffraction test results of the graphene prepared in Example 1 of this invention are as follows: Figure 2 As shown, a sharp characteristic peak appears at the (002) crystal plane diffraction position. The sharp peak indicates high crystallinity of the material, and the stacking of carbon atom layers in the direction perpendicular to the layer plane exhibits high order and periodicity. The interlayer arrangement is regular, and defects (such as interlayer dislocations and disordered stacking) are few. This characteristic is consistent with the high I observed in Raman spectroscopy. G / I D The ratio results corroborate each other, indicating that the graphene prepared in Example 1 not only has a good in-plane ordered structure (Raman results), but also maintains high crystal integrity in the interlayer stacking direction.

[0065] The Raman spectroscopy results of the graphene prepared in Example 1 of this invention are as follows: Figure 3 As shown. In the field of carbon material characterization, Raman spectroscopy, due to its high sensitivity and specificity, has become an important means of identifying the structural characteristics of graphene and assessing its crystal quality. Among them, the G peak (approximately 1580 cm⁻¹) is significant. -1 The D peak originates from the in-plane vibrations of carbon atoms in the graphene lattice, reflecting the orderliness of the graphite crystal; while the D peak (approximately 1350 cm⁻¹) is due to the in-plane vibrations of carbon atoms in the graphene lattice. -1The intensity of the lattice defects, edge effects, or disordered structures is related to the lattice defects, edge effects, or disordered structures, and its intensity change can intuitively reflect the defect density in the material.

[0066] In the performance evaluation of graphene, the intensity ratio of the G peak to the D peak (IG) is considered. G / I D The ratio (x) is a key parameter: a higher ratio indicates a more significant degree of graphitization in the material, better lattice structure integrity, and fewer defects. This characteristic is crucial for the electrical conductivity of graphene because the presence of defects scatters charge carriers, reducing charge mobility, while highly graphitized graphene often possesses superior electrical properties. Figure 3 As can be seen from the Raman spectroscopy curve, the graphene sample prepared in this embodiment exhibits significant Ig. G / I D High ratio characteristics. This result clearly demonstrates that the graphene has a highly ordered graphitized structure with a low internal defect density.

[0067] In summary, the method of the embodiments of the present invention has the following advantages:

[0068] 1. This invention uses cellulose as a raw material. Cellulose is abundant and inexpensive, and it absorbs atmospheric CO2 during its growth stage. This process encapsulates it into high-value graphene, achieving net negative carbon emissions throughout its entire life cycle. No harmful chemical reagents are used in the synthesis process, meeting environmental protection requirements and avoiding the environmental pollution problems caused by the use of toxic chemicals in traditional graphene production methods.

[0069] 2. Traditional graphene preparation methods typically require high temperature, high pressure, or complex catalytic reactions. This invention, however, utilizes the Joule heating effect to directly apply high voltage to cellulose, greatly simplifying the preparation process. The second-level Joule heating reaction significantly shortens the graphene preparation time. Compared to traditional high-temperature sintering methods (which require several hours to tens of hours), this invention can complete graphene synthesis in just a few seconds, significantly improving production efficiency.

[0070] 3. This invention ensures the high conductivity of graphene by controlling the resistance of the material with direct current. In particular, in step 2, by controlling the resistance of the pre-graphitized cellulose, the Joule heating process is ensured to proceed efficiently, thereby ensuring the excellent conductivity and stability of the final product, graphene.

[0071] 4. The operation process of this invention allows for adjustment of parameters such as voltage and resistance, exhibiting excellent controllability and adaptability. Even under different raw material or environmental conditions, variables such as current and time can be adjusted as needed to ensure high consistency and repeatability of the prepared graphene.

[0072] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.

Claims

1. A method for carbon sequestration and value-added conversion of biomass, characterized in that, The method comprises the following steps: S1, pyrolyzing cellulose to obtain carbonized cellulose; S2, adding a conductive agent to reduce the resistance of the carbonized cellulose; S3, performing first joule heat treatment on the carbonized cellulose after resistance reduction at a first voltage to obtain graphitized cellulose with resistance within a preset range; S4, performing second joule heat treatment on the graphitized cellulose at a second voltage to obtain biomass graphene; The first voltage is lower than the second voltage.

2. The biomass carbon sequestration value-added conversion method of claim 1, wherein, The pyrolysis in step S1 is performed in an inert atmosphere; the pyrolysis temperature is set to 300-800℃, the pyrolysis time is 30-120min, and the pyrolysis heating rate is 5-15℃ / min.

3. The biomass carbon capture and value-added conversion process of claim 1 wherein, In step S2, the resistance of the carbonized cellulose is reduced to increase the current density, so as to generate a stronger local electric field inside the carbon structure, which can directly drive carbon atoms to arrange in an ordered graphite layer from a disordered state, and also reduce the activation energy of the graphitization reaction, so that the phase transition in steps S3 and S4 can be completed at a lower energy input.

4. The biomass carbon sequestration value-added conversion method according to claim 1 or 3, characterized in that, Step S2 specifically comprises: adding a conductive agent to mix and ball mill with the carbonized cellulose, so that the conductive agent is uniformly distributed on the surface of the carbonized cellulose; then the carbonized cellulose is placed in a quartz tube, and the both ends are compressed using plugs to reduce the resistance to below a preset resistance value.

5. The biomass carbon sequestration value-added conversion method of claim 4, wherein, The resistance reduction treatment reduces the resistance of the carbonized cellulose to below 100Ω.

6. The biomass carbon sequestration value-added conversion method of claim 4, wherein, The conductive agent added in step S2 is carbon black, and the amount of carbon black added is 5-20wt% of the carbonized cellulose.

7. The biomass carbon capture and value-added conversion process of claim 1 wherein, Step S3 makes the aromatic fragments inside the carbon source to be oriented and π-π stacked in advance by low-pressure Joule heating, and the amorphous carbon between the sheets is partially removed to form a low-resistance graphite-like skeleton that still maintains a porous network, which microscopically presents an ordered sp 2 zone.

8. The biomass carbon sequestration value-added conversion method according to any one of claims 1-7, wherein, In step S3, the direct current voltage of the first joule heat treatment is set to 30-100V, and the discharge time is 1-20s.

9. The biomass carbon sequestration value-added conversion method of claim 8, wherein, The resistance of the graphitized cellulose obtained in step S3 is 1-5Ω.

10. The biomass carbon sequestration value-added conversion method according to any one of claims 1-9, wherein, In step S4, the direct current voltage of the second joule heat treatment is set to 120-200V, and the discharge time is 1-5s.

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