A method for preparing mesoporous activated carbon

Abstract

This invention relates to a method for preparing mesoporous activated carbon, comprising the following steps: S1: crushing biomass raw materials and mixing them evenly with phosphoric acid solution to obtain a pre-formed material; S2: heating and mixing the pre-formed material to plasticize it, obtaining a plasticized material, and then granulating the plasticized material; S3: reheating the granulated plasticized material to activate it, obtaining an activated material; S4: rinsing and drying the activated material sequentially, then immersing it in a template agent and mixing it evenly; S5: feeding the material obtained in step S4 into a graphite furnace for calcination to graphitize it, obtaining a graphitized material; S6: removing the template agent from the graphitized material, opening pores, and then grinding it to obtain the mesoporous activated carbon.

Description

Technical Field

[0001] This invention belongs to the field of mesoporous activated carbon preparation technology, and specifically relates to a method for preparing mesoporous activated carbon. Background Technology

[0002] Mesoporous activated carbon is a porous carbon material with a pore size between 2-50 nm. It has a high specific surface area, a relatively ordered pore structure, and electrical conductivity. It has broad application prospects in fields such as medicine, agricultural fertilizer, catalyst support, electrode materials, chemistry, and microelectronics.

[0003] Currently, mesoporous activated carbon can be prepared from biomass raw materials. The biomass undergoes carbonization, the addition of a template agent, calcination, and pore opening to produce mesoporous activated carbon. Mesoporous activated carbon can be used to make silicon-carbon anode materials for lithium-ion or sodium-ion batteries. However, the wide pore size distribution and non-concentrated pore size of mesoporous activated carbon are unfavorable for silicon deposition. It also has a low degree of graphitization and insufficient framework strength, making it prone to producing fine powder during grinding. This negatively impacts the electrochemical performance of silicon-carbon anode materials, such as causing battery capacity decay and shortened cycle life. Finally, its poor conductivity increases internal resistance, leading to further battery capacity decay and shortened cycle life. Summary of the Invention

[0004] To address one of the above problems, the present invention provides a method for preparing mesoporous activated carbon, comprising the following steps:

[0005] S1: After crushing the biomass raw materials, mix them evenly with the phosphoric acid solution to obtain the pre-formulated material;

[0006] S2: Heat and mix the pre-formed material to plasticize it, and then granulate the plasticized material.

[0007] S3: The granulated plasticized material is heated again to activate it, resulting in activated material;

[0008] S4: Rinse and dry the activating material in sequence, then immerse it in the template agent and mix it evenly;

[0009] S5: Input the material obtained in step S4 into a graphite furnace for calcination to obtain graphitized material;

[0010] S6: Remove the template agent from the graphitized material, open the pores, and then grind it to obtain the mesoporous activated carbon.

[0011] Optionally, in step S1, the biomass raw material includes hard biomass and humus. The hard biomass is selected from one or more combinations of wood, coconut shell, bamboo, or walnut shell. The humic acid content in the humus is not less than 30 wt%. The humus accounts for 4-7% of the total mass of the biomass raw material.

[0012] The biomass raw material is crushed to 100-200 mesh.

[0013] Optionally, the concentration of the phosphoric acid solution is 65-75 wt%, and the mass ratio of biomass raw material to phosphoric acid solution is 1:(1-3).

[0014] Optionally, in step S2, the pre-formed material is fed into a kneader for mixing to improve the plasticity of the biomass raw material. The plasticizing temperature is 160-250℃ and the plasticizing time is 1-3h.

[0015] Optionally, the granulation in step S2 involves granulating the cooled plasticized material to obtain columnar or spherical granules. For example, columnar granules can be produced by an extrusion granulator with particle sizes of 2mm, 3mm, 4mm, etc.; spherical granules can be produced by a needle granulator with particle sizes of 1.5mm, 2mm, 2.5mm, 3mm, etc.

[0016] Optionally, in step S3, the granulated plasticized material is fed into a stainless steel rotary furnace for heating and activation at a temperature of 400-700℃ for 1-3 hours.

[0017] During the activation process, a first process gas is introduced into the plasticizer. The first process gas includes nitrogen and organic gas, with the organic gas accounting for 4-8 vol%. The organic gas is selected from one or more of ethylene, n-butene, or propylene. If the organic gas includes two or more gases, they have the same volume.

[0018] Optionally, in step S4, the activating material is repeatedly rinsed with water to remove residual phosphoric acid, so that the phosphoric acid in the activating material is less than 200 ppm. The residual phosphoric acid can also be recovered and, after slight filtration, can be reused in step S1.

[0019] The drying process specifically involves drying the activated material in a drying oven at, for example, 200-300°C, until the moisture content is less than 5%.

[0020] Optionally, the template agent is a silicon-based template agent, which is a silica gel solution. By controlling the size of the nano-silica in the silica gel solution, the pore size of the mesoporous activated carbon after template removal is adjusted. The size of the nano-silica in the silica gel solution used in this invention is selected from the following levels: 8-10nm, 10-20nm, 30-50nm or 80-150nm.

[0021] The amount of the template agent is 30-60% of the mass of the activating material.

[0022] Optionally, in step S5, the calcination temperature is 2300-2700℃, and the degree of graphitization can be 30-70%.

[0023] In step S5, during the graphitization process, a second process gas is introduced into the material obtained in step S4. The second process gas includes nitrogen and carbon dioxide, with carbon dioxide accounting for 10-25 vol of the second process gas.

[0024] The present invention provides a horizontal graphite furnace for calcination in step S5. The horizontal graphite furnace includes a horizontal furnace body, a heating device and a heat insulation jacket. The upstream end of the furnace body is provided with a feed port for inputting activated material impregnated with template agent into the furnace body. The downstream end of the furnace body is provided with a discharge port and an exhaust port. The discharge port is used to discharge the calcined material and the exhaust port is used to discharge excess gas in the furnace body.

[0025] The heating device surrounds the outside of the furnace body to heat the furnace body; a gas transmission layer is provided outside the heating device for preheating nitrogen; an insulation sleeve is provided outside the gas transmission layer for heat preservation of the furnace body.

[0026] The inner side of the furnace body is provided with a gas output layer. The end of the gas output layer near the feed inlet is connected to the gas transmission layer. The side of the gas output layer facing the inside of the furnace body has several gas outlets. Nitrogen gas is preheated by the gas transmission layer and then input into the gas output layer, and then enters the furnace body from the gas outlet.

[0027] The furnace body is equipped with a vent pipe for introducing carbon dioxide into the furnace body.

[0028] Optionally, the gas transmission layer is provided with a continuous spiral gas channel, which is arranged around the furnace body and the heating device, that is, it is arranged from the downstream end of the furnace body to the upstream end. The gas channel has an inlet near the downstream end of the furnace body and an outlet near the upstream end of the furnace body. This allows nitrogen to flow from the downstream end of the furnace body to the upstream end along the spiral gas channel during preheating, flowing in the opposite direction to the main gas flow in the furnace body, and prolonging the preheating time.

[0029] Optionally, the gas output layer is set close to the inner wall of the furnace body, and the gas output layer covers the inner wall of the furnace body from the top to the middle; the gas output layer is hollow inside, and the end of the gas output layer near the feed inlet is connected to the gas outlet of the gas transmission layer, that is, the gas outlet of the gas transmission layer passes through the furnace body wall.

[0030] Several gas outlet holes are evenly arranged on one side wall facing the inside of the furnace body to release nitrogen gas;

[0031] The thickness of the gas output layer is 1 / 10 to 1 / 5 of the furnace body's internal radius.

[0032] Optionally, the vent pipe is horizontally arranged and located at the center of the furnace body; the vent pipe is a sleeve structure, including an inner pipe and an outer pipe arranged concentrically, with both ends of the outer pipe fixed inside the two ends of the furnace body; the air inlet of the inner pipe extends out of the side wall at the downstream end of the furnace body for inputting carbon dioxide; the air outlet of the inner pipe is close to the upstream end of the furnace body and located inside the outer pipe, for inputting the carbon dioxide that has flowed through the inner pipe and completed preheating into the outer pipe;

[0033] The outer tube has several jet holes evenly distributed on its side for introducing carbon dioxide into the furnace body.

[0034] Optionally, the exhaust port is connected to a cooling pipe, and the cooling pipe has a cooling jacket on its outer side, with an inlet and an outlet at each end of the cooling jacket; the outlet of the cooling pipe is connected to a gas tank or vented directly. Excess gas after the reaction is discharged from the furnace body, cooled (the cooling medium is cold water or cold air), and then discharged into a gas tank or vented directly.

[0035] In the horizontal graphite furnace of this invention, the material obtained in step S4 is fed into the furnace body through the feed inlet. A conventional heating device is sufficient to provide heat to the furnace body, gas transmission layer, and vent pipe. Nitrogen gas is fed into the gas transmission layer from the downstream side, preheated during its transmission from the downstream side to the upstream side, then fed into the gas output layer, and finally uniformly fed into the furnace body through the vent. Simultaneously, organic gas is first fed into the inner tube of the vent pipe, preheated during its transmission from the downstream side to the upstream side, then fed into the outer tube, and finally uniformly fed into the furnace body. Since step S5 of this invention requires the use of the second process gas, the horizontal graphite furnace facilitates the separate input of nitrogen and carbon dioxide, and allows for separate preheating of nitrogen and carbon dioxide before they enter the furnace body. The preheated nitrogen is uniformly fed into the furnace body through the vent, and the preheated carbon dioxide is uniformly fed into the middle of the furnace body through the jet nozzle, where it undergoes graphitization together with the material inside the furnace body. Preheated gas is more likely to mix with the materials inside the furnace, reducing resistivity; improved gas uniformity facilitates full contact with the materials inside the furnace, which in turn helps to increase graphitization and reduce resistivity.

[0036] There are many types of biomass in nature, and different types of biomass have different biochemical compositions, different microstructures, and significantly different physicochemical properties. This invention, targeting the pore size characteristics of mesoporous activated carbon, selects hard biomass as the raw material, which contains a large amount of lignin and has a rich pore structure. Nitrogen provides an inert atmosphere in the rotary kiln. During the heating and activation process, the plasticizer undergoes a complex reaction with the hard biomass, humic substances, phosphoric acid, and organic gases, activating the structure of the hard biomass. Humic substances contain abundant nitrogen, carbon, oxygen, hydrogen, and other metallic elements, which, combined with organic gases, give the hard biomass many active sites, thus improving its electrical conductivity.

[0037] In step S3, the plasticized material is activated by heating in an atmosphere of organic gas, resulting in a reaction that yields numerous activation sites and various active groups. In step S5, the activated material impregnated with the template agent is reacted again in a furnace under an atmosphere of nitrogen and carbon dioxide, incorporating carbon dioxide into the material. Unexpectedly, this invention has discovered that the graphitized material obtained after activation in step S3 and graphitization in step S5 exhibits excellent electrical conductivity, with a specific surface area controlled to be <100 m². 2 / g, bulk density > 0.6g / ml, resistivity < 3Ω·cm.

[0038] Optionally, in step S6, the specific operation of opening the hole is as follows: When using a silicon-based template agent, the graphitized material is subjected to high-pressure alkaline boiling to remove the template, and potassium hydroxide solution and / or sodium hydroxide solution are added. The alkaline concentration is 3-5 wt%. The prepared alkaline solution is loaded into a high-pressure reactor together with the graphitized material at a solid-liquid ratio of 1:(3-5). The alkaline boiling pressure is 0.8-1 MPa, and the alkaline boiling time is 2-4 hours. After high-pressure alkaline boiling, the obtained material is rinsed with water until neutral, and then the material is dried.

[0039] Optionally, in step S6, air jet milling is used, and the particle size D50 is controlled to be 7±2μm.

[0040] The mesoporous activated carbon obtained by this invention has a specific surface area >1200 m². 2 / g, total pore volume > 1.2cm³ 3 / g, average pore size >4nm. Attached Figure Description

[0041] Figure 1 The Raman spectrum of the mesoporous activated carbon prepared in Example 1;

[0042] Figure 2 The Raman spectrum of the mesoporous activated carbon prepared in Comparative Example 1 is shown.

[0043] Figure 3 Electron micrograph of the mesoporous activated carbon prepared in Example 1;

[0044] Figure 4 Electron microscopy image of the mesoporous activated carbon prepared in Comparative Example 1;

[0045] Figure 5 This is a schematic diagram of the structure of the horizontal graphite furnace in Example 8 (I);

[0046] Figure 6 This is a schematic diagram (II) of the horizontal graphite furnace in Example 8.

[0047] In the attached diagram, 1-furnace body, 2-heating device, 3-insulation sleeve, 4-feed inlet, 5-exhaust port, 6-gas transmission layer, 7-gas output layer, 8-air outlet, 9-vent pipe, 10-inner pipe, 11-outer pipe, 12-air jet hole, 13-discharge port. Detailed Implementation

[0048] Example 1

[0049] This embodiment provides a method for preparing mesoporous activated carbon, such as... Figure 1 As shown, it includes the following steps:

[0050] S1: After crushing the biomass raw materials, mix them evenly with the phosphoric acid solution to obtain the pre-formulated material;

[0051] The biomass raw materials are equal masses of wood, coconut shells, and walnut shells, crushed to 100-200 mesh;

[0052] The concentration of the phosphoric acid solution is 65 wt%, and the mass ratio of biomass raw material to phosphoric acid solution is 1:3;

[0053] S2: The pre-formed material is fed into a kneader for heating and mixing to plasticize it. The plasticizing temperature is 160℃ and the plasticizing time is 3 hours to obtain the plasticized material.

[0054] The cooled plasticized material is then granulated using a needle granulator to obtain spherical particles with an average particle size of 2 mm.

[0055] S3: The granulated plasticized material is reheated in a stainless steel rotary furnace, and air is introduced for activation. The activation temperature is 700℃ and the activation time is 1 hour to obtain the activated material.

[0056] S4: Rinse the activating material repeatedly with water to remove residual phosphoric acid, so that the phosphoric acid in the activating material is less than 200 ppm, and recover the phosphoric acid for use in step S1.

[0057] The rinsed activated material is dried in a drying oven at 200°C until the moisture content is <5%.

[0058] The dried activating material is immersed in a template agent and mixed evenly. The template agent is a silica gel solution containing nano-silica with a size of 10-20 nm.

[0059] S5: Input the material obtained in step S4 into a graphite furnace for calcination to graphitize it. The calcination temperature is 2300℃ and the calcination time is 4h to obtain graphitized material.

[0060] S6: Remove the template agent from the graphitized material, open the pores, and then perform air jet milling. Control the particle size D50 to 7±2μm, that is, 50% of the product has a particle size of 7±2μm, to obtain the mesoporous activated carbon.

[0061] The specific operation for opening the hole is as follows: the graphitized material is subjected to high-pressure alkaline boiling to remove the template, and potassium hydroxide solution and / or sodium hydroxide solution are added with an alkaline concentration of 3wt%. The prepared alkaline solution is loaded into a high-pressure reactor together with the graphitized material at a solid-liquid ratio of 1:5. The alkaline boiling pressure is 0.8MPa and the alkaline boiling time is 4h. After high-pressure alkaline boiling, the material is rinsed with water until it is neutral, and then the material is dried.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing mesoporous activated carbon, which is the same as in Example 1, except that the activation treatment in step S3 is not performed, and the granulated plasticized material is directly treated in step S4.

[0064] Appendix Figure 1 and 2 In the middle, at 1600m -1 The peak at the figure is the peak of graphitization of mesoporous activated carbon. As can be seen from the figure, the graphitization peak of the mesoporous activated carbon prepared in Comparative Example 1 is much smaller than that of the mesoporous activated carbon prepared in Example 1, indicating that the mesoporous activated carbon prepared in Example 1 has a higher degree of graphitization and better conductivity.

[0065] From the appendix Figure 3 and 4 As can be seen, the mesoporous activated carbon particles in Example 1 are more regular, and the particles obtained after grinding are blocky with distinct edges and corners and no obvious fine powder, indicating that the carbon skeleton has higher strength; the mesoporous activated carbon particles in Comparative Example 1 are irregular in size and have more obvious fine powder, indicating that the carbon skeleton has lower strength.

[0066] Example 2

[0067] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Embodiment 1, except that the biomass raw material also includes humic substances, the humic acid content in the humic substances is 35 wt%, and the humic substances account for 4% of the total mass of the biomass raw material.

[0068] Example 3

[0069] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Example 2, except that the humic substance accounts for 7% of the total mass of the biomass raw material.

[0070] Example 4

[0071] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Example 2, except that the humic substance accounts for 8% of the total mass of the biomass raw material.

[0072] Example 5

[0073] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Embodiment 2, except that a first process gas is introduced into the plasticizer during the activation process. The first process gas includes nitrogen and organic gas, with the organic gas accounting for 4 vol% of the first process gas. The organic gas consists of ethylene and propylene of equal volume.

[0074] Example 6

[0075] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Example 5, except that the organic gas accounts for 8 vol% of the total gas volume in the first process.

[0076] Example 7

[0077] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Example 5, except that the organic gas accounts for 3 vol% of the total gas volume in the first process.

[0078] Example 8

[0079] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as that in embodiment 5, except that a second process gas is introduced into the material obtained in step S4 during the graphitization process in step S5. The second process gas includes nitrogen and carbon dioxide, and carbon dioxide accounts for 10 vol of the total amount of the second process gas.

[0080] In this embodiment, a horizontal graphite furnace is used for graphitization in step S5, such as... Figures 5-6 As shown, the horizontal graphite furnace includes a horizontal furnace body 1, a heating device 2, and an insulation jacket 3. The upstream end of the furnace body 1 is provided with a feed inlet 4 for feeding the activated material impregnated with template agent into the furnace body 1. The downstream end of the furnace body 1 is provided with a discharge outlet 13 and an exhaust outlet 5. The discharge outlet 13 is used to discharge the graphitized material, and the exhaust outlet 5 is used to discharge excess gas in the furnace body 1.

[0081] Heating device 2 is a heating plate, which surrounds the outside of furnace body 1 to heat furnace body 1; a gas transmission layer 6 is provided on the outside of heating device 2 for preheating nitrogen; an insulation sleeve 3 is provided on the outside of gas transmission layer 6 for insulating furnace body 1.

[0082] The inner side of the furnace body 1 is provided with a gas output layer 7. The end of the gas output layer 7 near the feed inlet 4 is connected to the gas transmission layer 6. The side of the gas output layer 7 facing the inside of the furnace body 1 is provided with several gas outlets 8. After the nitrogen is preheated by the gas transmission layer 6, it is input into the gas output layer 7 and then enters the inside of the furnace body 1 from the gas outlet.

[0083] The furnace body 1 is equipped with a vent pipe 9 for introducing carbon dioxide into the furnace body 1.

[0084] The gas transmission layer 6 is provided with a continuous spiral gas channel, which is arranged around the furnace body 1 and the heating device 2, that is, it is arranged from the downstream end of the furnace body 1 to the upstream end. The gas channel has an inlet near the downstream end of the furnace body 1 and an outlet near the upstream end of the furnace body 1. This allows nitrogen to flow from the downstream end of the furnace body 1 to the upstream end along the spiral gas channel during preheating, flowing in the opposite direction to the main airflow in the furnace body 1, and prolonging the preheating time.

[0085] The gas output layer 7 is set close to the inner wall of the furnace body 1, and the gas output layer 7 covers the inner wall of the furnace body 1 from the top to the middle. The gas output layer 7 is hollow inside, and the end of the gas output layer 7 near the feed inlet 4 is connected to the gas outlet of the gas transmission layer 6, that is, the gas outlet of the gas transmission layer 6 passes through the wall of the furnace body 1.

[0086] Several gas outlet holes 8 are evenly arranged on the side wall of the gas output layer 7 facing the interior of the furnace body 1 for releasing nitrogen gas;

[0087] The thickness of the gas output layer 7 is 1 / 10 of the internal radius of the furnace body 1.

[0088] The vent pipe 9 is horizontally arranged and located at the center of the furnace body 1. The vent pipe 9 is a sleeve structure, including an inner pipe 10 and an outer pipe 11 arranged concentrically. The two ends of the outer pipe 11 are fixed inside the two ends of the furnace body 1. The air inlet of the inner pipe 10 extends out of the side wall of the downstream end of the furnace body 1 and is used to input organic gas. The air outlet of the inner pipe 10 is close to the upstream end of the furnace body 1 and is located inside the outer pipe 11. It is used to input carbon dioxide that has flowed through the inner pipe 10 and completed preheating into the outer pipe 11.

[0089] The outer tube 11 has several jet holes 12 evenly distributed on its side for introducing carbon dioxide into the furnace body 1.

[0090] The exhaust port 5 is connected to a cooling pipe, and a cooling jacket is provided on the outside of the cooling pipe. The two ends of the cooling jacket are respectively provided with an inlet and an outlet; the outlet of the cooling pipe is connected to a gas tank.

[0091] Example 9

[0092] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Example 8, except that carbon dioxide accounts for 25 vol% of the total amount of gas in the second process.

[0093] Example 10

[0094] This embodiment provides a method for preparing mesoporous activated carbon, which is the same as in Example 8, except that carbon dioxide accounts for 9 vol% of the total gas volume in the second process.

[0095] The nitrogen, carbon dioxide, ethylene, and propylene used in the above embodiments and comparative examples were all high-purity gases of 99.9%.

[0096] The resistivity of the mesoporous activated carbon prepared in the above examples and comparative examples was measured, and the results are shown in the table below.

[0097] Table 1. Comparison of the electrical properties of mesoporous activated carbon prepared in the examples and comparative examples.

[0098] Resistivity (Ω·cm) Resistivity (Ω·cm) Example 1 2.5 Example 7 1.9 Example 2 2.1 Example 8 1.3 Example 3 2.0 Example 9 1.2 Example 4 2.3 Example 10 1.5 Example 5 1.7 Comparative Example 1 10 Example 6 1.6

[0099] As shown in the table above, the resistivity of the mesoporous activated carbon prepared using this invention is less than 3 Ω·cm, indicating that the prepared mesoporous activated carbon has good electrical conductivity. In particular, the introduction of the first process gas during the activation treatment and the introduction of the second process gas during the graphitization treatment, combined with the biomass and humus in the raw materials, can achieve good performance.

Claims

1. A method for producing mesoporous activated carbon, characterized by, The method comprises the following steps: S1: crushing the biomass raw material, mixing it with a phosphoric acid solution, and obtaining a pre-prepared material; S2: heating and mixing the pre-prepared material, plasticizing it, obtaining plasticized material, and granulating the plasticized material; S3: heating the granulated plasticized material again, activating it, and obtaining activated material; S4: sequentially rinsing and drying the activated material, and then immersing it in a template agent and mixing it uniformly; S5: inputting the material obtained in step S4 into a graphite furnace, graphitizing it, and obtaining graphitized material; S6: removing the template agent from the graphitized material, opening pores, and grinding it to obtain the mesoporous activated carbon; The calcination operation of step S5 uses a horizontal graphite furnace, which comprises a horizontal furnace body, a heating device, and a heat preservation sleeve. The upstream end of the furnace body is provided with a feeding port for inputting the activated material immersed in the template agent into the furnace body. The downstream end of the furnace body is provided with a discharging port for discharging the calcined material and an exhaust port for discharging excess gas in the furnace body. The heating device surrounds the outside of the furnace body to heat the furnace body. The outside of the heating device is provided with a gas transmission layer for preheating nitrogen. The outside of the gas transmission layer is provided with a heat preservation sleeve for heat preservation of the furnace body. The inside of the furnace body is provided with a gas output layer. One end of the gas output layer close to the feeding port is communicated with the gas transmission layer. The side of the gas output layer facing the inside of the furnace body is provided with a plurality of gas outlets. Nitrogen is preheated in the gas transmission layer, input into the gas output layer, and then enters the inside of the furnace body from the gas outlet. The furnace body is provided with an air pipe for inputting carbon dioxide into the furnace body. The air pipe is horizontally arranged and located at the center of the furnace body. The air pipe has a sleeve structure comprising an inner pipe and an outer pipe arranged concentrically. The two ends of the outer pipe are fixed to the inside of the two ends of the furnace body. The gas inlet of the inner pipe penetrates through the side wall of the downstream end of the furnace body for inputting carbon dioxide. The gas outlet of the inner pipe is close to the upstream end of the furnace body and located inside the outer pipe for inputting carbon dioxide that has completed preheating in the inner pipe into the outer pipe. The side of the outer pipe is uniformly provided with a plurality of air injection holes for inputting carbon dioxide into the inside of the furnace body.

2. The method of claim 1, wherein the mesoporous activated carbon is prepared by the steps of: In step S1, the biomass raw material comprises hard biomass and humus. The hard biomass is selected from one or more than two combinations of wood, coconut shell, bamboo block, or walnut shell. The content of humic acid in the humus is not less than 30wt%. The humus accounts for 4-7% of the total mass of the biomass raw material.

3. The method of claim 1, wherein the mesoporous activated carbon is prepared by the steps of: The concentration of the phosphoric acid solution is 65-75wt%. The mass ratio of the biomass raw material to the phosphoric acid solution is 1:(1-3).

4. The method of claim 1, wherein the mesoporous activated carbon is prepared by the steps of: In step S2, the pre-prepared material is input into a kneader for mixing. The plasticizing temperature is 160-250℃, and the plasticizing time is 1-3h.

5. The method for preparing mesoporous activated carbon according to claim 1, characterized in that, In step S3, the activation temperature is 400-700℃, and the activation time is 1-3h. During the activation process, the first process gas is input into the plasticized material. The first process gas comprises nitrogen and an organic gas. The organic gas accounts for 4-8vol% of the first process gas. The organic gas is selected from one or more than two combinations of ethylene, n-butene, or propylene.

6. The method of claim 1, wherein the mesoporous activated carbon is prepared by the steps of: In step S4, the activated material is repeatedly rinsed with water to remove residual phosphoric acid, so that the phosphoric acid in the activated material is less than 200 ppm, and the residual phosphoric acid can also be recovered, and after filtration, can be used in step S1; The drying is specifically drying the activated material in a drying furnace, and the moisture is less than 5%.

7. The method for preparing mesoporous activated carbon according to claim 1, characterized in that, In step S5, the calcination temperature is 2300-2700°C; In the graphitization process of step S5, a second process gas is introduced into the material obtained in step S4, and the second process gas includes nitrogen and carbon dioxide, and the carbon dioxide accounts for 10-25 vol% of the second process gas.

8. The method for preparing mesoporous activated carbon according to claim 7, characterized in that, The gas transmission layer is provided with a continuous spiral gas channel, which is arranged around the furnace body and the heating device, and is arranged from the downstream end to the upstream end of the furnace body. One end of the gas channel close to the downstream end of the furnace body is provided with a gas inlet, and the gas outlet of the gas channel is close to one end of the upstream end of the furnace body. The gas output layer is arranged close to the inner side wall of the furnace body, and covers the inner side wall of the top to the middle of the furnace body. The gas output layer is hollow inside, and one end of the gas output layer close to the inlet is communicated with the gas outlet of the gas transmission layer.

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