A method of biomass pyrolysis

Abstract

This invention provides a biomass pyrolysis method, comprising the following steps: contacting biomass feedstock with carbon foam material, applying microwaves under an inert atmosphere to generate plasma with a temperature not lower than 3000K, causing the biomass feedstock to undergo a pyrolysis reaction; simultaneously, the volume ratio of the carbon foam material to the microwave power is 1:(25-500); wherein the unit of volume is cm³. 3 The unit of power is W. This biomass pyrolysis method has high conversion efficiency and high added value.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy technology and relates to a biomass pyrolysis method. Background Technology

[0002] In recent years, the use of unconventional heating methods such as Joule heating, microwaves, and lasers to convert biomass-based feedstocks through thermal processing under non-traditional conditions has gradually attracted attention. Compared with traditional thermal processing methods, this unconventional heating method can achieve highly efficient pyrolysis of biomass feedstocks in a very short time. Through thermal processes such as dehydrogenation and decarboxylation, it produces pyrolysis gases such as hydrogen, carbon monoxide, and ethylene. This not only enables the resource utilization of biomass feedstocks but also reduces carbon emissions and environmental pollution.

[0003] Chinese patent CN105295970A discloses a method for co-producing carbon gas from rice straw via microwave pyrolysis. The method involves crushing the rice straw, adding a certain amount of catalyst, and then directly heating and pyrolyzing the raw material using microwaves. The pyrolysis temperature is 400℃, the reaction time is 8-12 minutes, and the carbon gas yield is 65.21-89.34%. While the process is relatively simple, the microwave heating efficiency and pyrolysis temperature are relatively low, the pyrolysis time is relatively long, and the added value of the pyrolysis products is also low.

[0004] Chinese patent CN117819544A discloses a method for preparing syngas and activated carbon from cotton stalks via microwave pyrolysis. This method involves adding microwave-safe materials to the cotton stalks to separate the gaseous, liquid, and solid products from the pyrolysis reaction. The pyrolysis process can reach temperatures up to 750°C, but it is complex. The solid products after microwave pyrolysis require further carbonization, preheating and drying, deep carbonization, and activation to obtain the final product.

[0005] Therefore, how to develop a biomass pyrolysis method with high conversion efficiency and high added value is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned shortcomings, this invention provides a biomass pyrolysis method with high conversion efficiency and added value.

[0007] This invention provides a biomass pyrolysis method, comprising the following steps: contacting biomass raw materials with carbon foam material, applying microwaves under an inert atmosphere to generate plasma with a temperature not lower than 3000K, and causing the biomass raw materials to undergo a pyrolysis reaction;

[0008] The volume ratio of the carbon foam material to the microwave power is 1:(25-500); where the volume is measured in cm³. 3 The unit of power is W.

[0009] Furthermore, the specific surface area (BET) of the carbon foam material is ≥25 m². 2 / g, and / or, total pore volume ≥0.04cm³ 3 / g, and / or, micro-mesoporous ratio ≥50%.

[0010] Furthermore, the carbon foam material is obtained by carbonizing a carbonizable organic foam at 700-1200℃ for 0.5-6 hours;

[0011] The organic foam includes at least one of melamine foam, polyimide foam, and phenolic resin foam.

[0012] Furthermore, the volume ratio of the carbon foam material to the mass of the biomass raw material is 1:(0.05-1); where the unit of volume is cm. 3 The unit of mass is g.

[0013] Furthermore, the frequency of the microwave is 2.45-3.20 GHz.

[0014] Furthermore, the pyrolysis reaction is intermittent;

[0015] The ratio of the microwave application time to the mass of the biomass raw material is (3-60):1; where the unit of application time is s and the unit of mass is g.

[0016] Furthermore, the biomass raw material has a moisture content of <0.5wt% and / or a particle size of <100 mesh.

[0017] Furthermore, the carbon foam material includes a first carbon foam material and a second carbon foam material; the first carbon foam material and the second carbon foam material are placed opposite each other to form a sandwich, and the biomass raw material is located in the sandwich;

[0018] The spacing between the interlayers is 0.5-10mm.

[0019] Furthermore, the inert atmosphere includes nitrogen and / or argon, and the oxygen content in the inert atmosphere is <0.1%.

[0020] Furthermore, the biomass raw materials include at least one of activated carbon, kitchen waste, rice husks, straw, and bamboo powder.

[0021] The biomass pyrolysis method of this invention involves contacting carbon foam material with biomass feedstock, placing it in an inert atmosphere, and applying microwaves. The carbon foam material induces the microwaves to ionize the gas, generating high-temperature plasma (not less than 3000K). Simultaneously, by controlling the ratio of the volume of the carbon foam material to the power of the microwaves to be 1:(25-500), the conversion rate of biomass feedstock can be improved, and a large number of gaseous products (hydrogen, carbon monoxide, ethylene, etc.) and high-quality solid product graphene can be obtained, realizing high-value-added biomass pyrolysis and thus achieving the resource utilization of biomass. Attached Figure Description

[0022] Figure 1 The Raman spectrum of the solid product in Example 1 of this invention;

[0023] Figure 2 This is a SEM image of the solid product in Example 1 of the present invention;

[0024] Figure 3 This is a TEM image of the solid product in Example 1 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Biomass, as a new type of energy, possesses unique advantages such as abundant reserves and renewability. In the near future, it is expected to replace traditional petrochemical materials in various application fields, effectively reducing the risk of fossil fuel depletion. In my country, biomass energy primarily utilizes various residues and waste materials, such as agricultural waste, forestry waste, and household garbage. Through the resource utilization of biomass, not only can waste be turned into treasure and the energy shortage problem be solved, but it also reduces environmental pollution, mitigates climate change, and is of great significance in addressing energy shortages, environmental pollution, and promoting economic development.

[0027] Currently, many technicians have conducted research on the resource utilization of biomass raw materials and proposed various processing methods. Among these methods, microwave pyrolysis of biomass has significant advantages in terms of heating speed, heating uniformity, penetration, energy saving and environmental protection, and ease of operation. However, there is still considerable room for improvement in its pyrolysis efficiency, the added value of pyrolysis products, and the simplicity of the process.

[0028] Through analysis, the inventors discovered that the pyrolysis temperature in the biomass pyrolysis reaction has a significant impact on the conversion rate of biomass feedstock and the added value of the products. The higher the pyrolysis temperature, the higher the degree of pyrolysis of the biomass feedstock, and the higher the conversion rate and added value. To increase the pyrolysis temperature, further selection of absorbing materials and microwave power is required.

[0029] Based on the above analysis, the present invention provides a biomass pyrolysis method, comprising the following steps: contacting biomass raw materials with carbon foam material, applying microwaves under an inert atmosphere to generate plasma with a temperature not lower than 3000K, and causing the biomass raw materials to undergo a pyrolysis reaction;

[0030] The volume ratio of carbon foam material to microwave power is 1:(25-500); where the volume unit is cm³. 3 The unit of power is W.

[0031] The biomass pyrolysis method of this invention involves contacting a carbon foam material with biomass feedstock and placing it in an inert atmosphere. Microwaves are applied to the carbon foam material, inducing charge accumulation and ionization of the gas, thereby generating a continuous high-temperature plasma (not less than 3000K) to promote the pyrolysis of the biomass feedstock. The carbon foam material maintains its original microstructure at high temperatures, effectively preventing the collapse of the carbon foam structure from affecting the stability of the pyrolysis reaction. Furthermore, when the volume ratio of the carbon foam material to the microwave power is 1:(25-500), the pyrolysis temperature can be further increased. Therefore, the biomass pyrolysis method of this invention can comprehensively improve the conversion rate of biomass feedstock and obtain high-value-added products, including a large number of gaseous products (hydrogen, carbon monoxide, ethylene, etc.) and solid products (graphene).

[0032] In this invention, "biomass" refers to all biological organisms produced through photosynthesis, including plants, crops, forest products and their waste.

[0033] In this invention, "carbon foam material" refers to a carbon material with a three-dimensional network structure formed by the cross-linking of carbon skeletons.

[0034] This invention does not specifically limit the types and sources of carbon foam materials and biomass raw materials; products prepared using commercially available products or conventional preparation methods known to those skilled in the art are acceptable.

[0035] This invention does not impose a specific limit on the ratio of carbon foam material to biomass raw materials, as long as the biomass raw materials can be fully reacted.

[0036] The present invention does not specifically limit the contact method between biomass raw materials and carbon foam materials, as long as the two are in full contact. For example, the biomass raw materials can be filled into the carbon foam materials, or the biomass raw materials can be spread flat on the surface of the carbon foam.

[0037] It is understood that the pyrolysis reaction in this invention is carried out in a microwave reactor. The pyrolysis reaction in this invention can be a batch pyrolysis reaction or a continuous pyrolysis reaction.

[0038] In one embodiment, the biomass feedstock is divided into multiple batches. The Nth batch of biomass feedstock is sent to a microwave reactor for pyrolysis, and solid and gaseous products are collected after the reaction. Then, the (N+1)th batch of biomass feedstock is sent to the microwave reactor for pyrolysis, and solid and gaseous products are collected after the reaction. This process is repeated, and this reaction method is called intermittent pyrolysis reaction.

[0039] In another embodiment, biomass feedstock is continuously and uninterruptedly fed into a microwave reactor for pyrolysis, while the resulting solid and gaseous products are continuously and uninterruptedly collected; this reaction method is a continuous pyrolysis reaction.

[0040] In this invention, "volume of carbon foam material" refers to the total volume of carbon foam material participating in the reaction in the microwave reactor.

[0041] Furthermore, the structure of carbon foam materials also has a significant impact on the degree of biomass pyrolysis. For example, the specific surface area, total pore volume, and micro / mesopore ratio of carbon foam materials. Higher specific surface area and total pore volume indicate that carbon foam materials have a more complex microstructure and higher porosity. Combined with a higher micro / mesopore ratio, this is conducive to the induced absorption of microwaves, thereby triggering the generation of high-temperature plasma.

[0042] In this invention, "micropore-mesopore ratio" refers to the percentage of the total volume of micropores and mesopores in carbon foam materials relative to the total pore volume.

[0043] In one specific embodiment, the BET specific surface area of ​​the carbon foam material is ≥25m². 2 / g, pore volume ≥0.04cm³ 3 / g, with a microporous / mesoporous ratio ≥50%. Within this range, higher pyrolysis temperatures can be achieved, further improving the conversion rate of biomass feedstock and the added value of products.

[0044] Furthermore, carbon foam materials can be further selected to improve their specific surface area (BET), total pore volume, and micro / mesopore ratio, while ensuring high structural stability.

[0045] In one specific embodiment, the carbon foam material is obtained by carbonizing a carbonizable organic foam at 700-1200°C for 0.5-6 hours;

[0046] Organic foam includes at least one of melamine foam, polyimide foam, and phenolic resin foam.

[0047] Furthermore, melamine foam is preferred.

[0048] When carbon foam materials meet the aforementioned conditions, they help to further increase the specific surface area (BET), total pore volume, and micro-mesopore ratio of carbon foam, thereby enhancing the induction effect of carbon foam materials on microwaves, generating plasma at higher temperatures, and achieving a higher degree of pyrolysis. At the same time, the carbon foam materials obtained by carbonizing the above-mentioned organic foams have higher structural stability, ensuring the normal progress of the reaction and giving biomass raw materials a higher conversion rate and added value.

[0049] For example, the carbonization temperature is 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C; and the carbonization time is 0.5h, 1h, 2h, 3h, 4h, 5h or 6h.

[0050] Furthermore, the ratio of carbon foam material volume to biomass feedstock mass in the pyrolysis reaction can be controlled to ensure complete pyrolysis of the biomass feedstock. A ratio that is too high, while ensuring complete pyrolysis, results in lower production efficiency; a ratio that is too low leads to an excess of biomass feedstock, which cannot be fully pyrolyzed, resulting in a decrease in conversion rate and added value.

[0051] In one specific embodiment, the volume ratio of the carbon foam material to the mass of the biomass raw material is 1:(0.05-1); where the unit of volume is cm. 3 The unit of mass is g. That is, the ratio of the total volume of carbon foam material participating in the reaction to the total mass of biomass feedstock participating in the reaction in the microwave reactor. Within this range, the carbon foam material and biomass feedstock can better synergize and cooperate, which can not only further enhance the reaction degree of the biomass feedstock and improve the pyrolysis effect, but also ensure high production efficiency.

[0052] For example, the volume ratio of carbon foam material to the mass of biomass raw material is 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.

[0053] Furthermore, the frequency and duration of microwave application can be controlled to enhance the degree of pyrolysis of biomass raw materials, thereby further improving their conversion rate and product added value.

[0054] Among them, the microwave frequency affects the effect of carbon foam material in inducing plasma in a microwave field; the application time of microwaves is equivalent to the reaction time, which has a significant impact on the microstructure of the solid product graphene, thereby affecting the quality of graphene and reducing its added value.

[0055] In one specific embodiment, the microwave frequency is 2.45-3.20 GHz. Within this range, carbon foam can effectively exert an inductive effect in the microwave field, thereby generating high-temperature plasma.

[0056] For example, the microwave frequency is 2.45 GHz, 2.5 GHz, 2.6 GHz, 2.7 GHz, 2.8 GHz, 2.9 GHz, 3 GHz, 3.1 GHz or 3.2 GHz.

[0057] In one specific embodiment, the pyrolysis reaction is batch-based;

[0058] The ratio of microwave application time to the mass of biomass raw material is (3-60):1; where the unit of application time is s and the unit of mass is g.

[0059] When the pyrolysis reaction is intermittent, and when the ratio of the mass of each batch of biomass feedstock to the microwave application time is within the aforementioned range, the incomplete pyrolysis reaction caused by the mismatch between the application time and the mass of biomass feedstock can be avoided. This can further enhance the reaction degree of the biomass feedstock, converting it to a greater extent into solid products such as graphene and gaseous products such as hydrogen, carbon monoxide, and ethylene, thus giving the biomass feedstock a higher conversion rate and added value. At the same time, it can also ensure the quality of graphene.

[0060] Furthermore, the particle size and moisture content of the biomass feedstock also significantly affect the pyrolysis reaction. Specifically, the particle size of the biomass feedstock should not be too large, otherwise it will not be able to fully contact the carbon foam material, affecting the degree of pyrolysis. Moreover, excessive moisture in the biomass feedstock can also cause the carbon foam structure to be destroyed during high-temperature pyrolysis, resulting in cracking and affecting the normal progress of the reaction. Therefore, the moisture content of the biomass feedstock should not be too high and needs to be controlled.

[0061] In one specific embodiment, the moisture content of the biomass feedstock is <0.5wt%. Within this range, the damage and cracking of the carbon foam structure caused by moisture under high-temperature plasma conditions can be effectively avoided, ensuring the stable progress of the reaction.

[0062] In one specific embodiment, the particle size of the biomass feedstock is <100 mesh. Within this range, not only can the heat transfer effect be improved, but it can also ensure that the biomass feedstock is in full contact with the high-temperature plasma, ensuring that the carbon elements in the biomass are completely converted into graphene structures, thereby increasing the added value of the product.

[0063] For example, the particle size of the biomass feedstock is 150 mesh, 200 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh or 500 mesh.

[0064] Furthermore, the contact method between carbon foam materials and biomass feedstock during the pyrolysis reaction can be adjusted to improve the pyrolysis effect.

[0065] In one specific embodiment, the carbon foam material includes a first carbon foam material and a second carbon foam material; the first and second carbon foam materials are placed opposite each other to form a sandwich, with the biomass feedstock located in the sandwich; the spacing between the sandwich layers is 0.5-10 mm. When the biomass feedstock and carbon foam material are placed in the aforementioned manner, and the spacing between the sandwich layers is 0.5-10 mm, the contact area between the biomass feedstock and the high-temperature plasma can be effectively increased, allowing as much biomass feedstock as possible to come into contact with the high-temperature plasma, thereby ensuring a more uniform and complete reaction of the biomass in the pyrolysis reaction, and further improving the conversion rate and added value of the biomass feedstock.

[0066] For example, the spacing between the interlayers is 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm.

[0067] Besides the moisture content in the biomass feedstock, the oxygen content in the reaction atmosphere also significantly affects the structure of carbon foam materials. The presence of oxygen causes the carbon foam structure to collapse, rendering it ineffective and unable to induce microwave plasma generation. Therefore, the oxygen content in the reaction atmosphere needs to be strictly controlled.

[0068] In one specific embodiment, the inert atmosphere includes nitrogen and / or argon, and the oxygen content in the inert atmosphere is <0.1%. It should be noted that the oxygen content in this invention refers to volume content. Within this range, the low oxygen content in the atmosphere effectively prevents the collapse of the carbon foam structure caused by the reaction of oxygen with carbon.

[0069] In one specific embodiment, the biomass raw material includes at least one of activated carbon, kitchen waste, rice husks, straw, and bamboo powder.

[0070] The biomass pyrolysis method of the present invention will be described in detail below through specific embodiments.

[0071] Example 1

[0072] 1) Commercial melamine foam was cleaned with ultrapure water in an ultrasonic cleaner for 0.5 hours, then dried in an oven at 105°C for 12 hours. Subsequently, the dried melamine foam was carbonized in an inert atmosphere at 1000°C for 1 hour to obtain the carbon foam material of this embodiment. Next, the carbon foam material was cut to a size of 16×7×7 mm (0.784 cm). 3 ) dimensions;

[0073] The specific surface area (BET) of the carbon foam material is 36.24 m². 2 / g, pore volume 0.06cm³ 3 / g, with a micro-mesopore ratio of 64%;

[0074] 2) Using kitchen waste as biomass raw material, the moisture content of the kitchen waste is first removed to 4.5 wt% through freeze drying, and then it is pulverized to ensure that the powder particle size is within 100 mesh; the pulverized kitchen waste powder is then dried again, and the final moisture content is 0.32%.

[0075] 3) Select an intermittent reaction. Fill 1g of the above-mentioned kitchen waste powder between two sandwich-type carbon foam materials with a spacing of 3mm. Replace the air in the microwave reactor with nitrogen. Place the sandwich-type carbon foam material filled with biomass raw materials in the reactor. During the reaction, ensure that the nitrogen flow rate is 50mL / min and the oxygen content is <0.1%. Use a magnetron to generate a microwave frequency of 2.45GHz and a power of 400W to generate plasma with a temperature of not less than 3000K. The reaction time is 15s. The biomass raw materials are decomposed to obtain solid products, gaseous products and liquid products. The solid product is graphene. The gaseous products include hydrogen, carbon monoxide, hydrocarbons, ethylene and other gases (mainly carbon dioxide and hydrogen sulfide). The liquid products include tar and water.

[0076] Example 2

[0077] 1) Commercial melamine foam was cleaned with ultrapure water in an ultrasonic cleaner for 0.5 hours, then dried in an oven at 105°C for 12 hours. Subsequently, the dried melamine foam was carbonized in an inert atmosphere at 800°C for 1 hour to obtain the carbon foam material of this embodiment. Next, the carbon foam material was cut to a size of 15×10×5mm (0.75cm). 3 ) dimensions;

[0078] The specific surface area (BET) of the carbon foam material is 36.24 m². 2 / g, pore volume 0.06 cm³ 3 / g, of which the proportion of micropores is 64%;

[0079] 2) Using bamboo powder as a biomass raw material, the bamboo powder is further pulverized to ensure that the powder particle size is within 100 mesh; the pulverized bamboo powder is then dried to a moisture content of 0.17%.

[0080] 3) Select an intermittent reaction. Fill 1g of bamboo powder between two sandwiched carbon foam materials with a spacing of 2.3mm. Replace the air in the microwave reactor with nitrogen. Place the sandwiched carbon foam material filled with biomass raw materials in the reactor. During the reaction, ensure that the nitrogen flow rate is 100mL / min and the oxygen content is <0.1%. Use a magnetron to generate a microwave frequency of 2.45GHz and a power of 600W to generate plasma with a temperature of not less than 3000K. The reaction time is 18s. The biomass raw materials are decomposed to obtain solid products, gaseous products and liquid products, which are collected separately.

[0081] Example 3

[0082] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the microwave power is adjusted to 39W, so the ratio of carbon foam volume to microwave power is 1:25.

[0083] Example 4

[0084] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the microwave power is adjusted to 235W, so the ratio of carbon foam volume to microwave power is 1:150.

[0085] Example 5

[0086] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1. The difference is that in step 3), the microwave power is adjusted to 784W, so the ratio of carbon foam volume to microwave power is 1:500.

[0087] Example 6

[0088] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the mass of kitchen waste powder is adjusted to 0.0784g and the microwave application time is adjusted to 4s. Then the ratio of carbon foam volume to biomass raw material mass is 1:0.05 and the ratio of microwave application time to biomass raw material mass is 51:1.

[0089] Example 7

[0090] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the mass of kitchen waste powder is adjusted to 1.568g, so the ratio of carbon foam volume to biomass raw material mass is 1:1, and the ratio of microwave application time to biomass raw material mass is 9.6:1.

[0091] Example 8

[0092] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the microwave application time is adjusted to 3s, so the ratio of microwave application time to the mass of biomass raw material is 3:1.

[0093] Example 9

[0094] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the microwave application time is adjusted to 60s, so the ratio of microwave application time to the mass of biomass raw material is 60:1.

[0095] Example 10

[0096] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1, except that in step 3), the interlayer spacing is adjusted to 0.5 mm.

[0097] Example 11

[0098] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1, except that in step 3), the interlayer spacing is adjusted to 10 mm.

[0099] Example 12

[0100] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1. The difference is that in step 1), polyimide foam is used, and the carbonization temperature is adjusted to 1200℃ and the carbonization time is adjusted to 0.5h to obtain the carbon foam material of this embodiment.

[0101] The specific surface area (BET) of this carbon foam material is 34.17 m². 2 / g, pore volume 0.05cm³ 3 / g, with a micro-mesopore ratio of 59%.

[0102] Example 13

[0103] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 1), phenolic resin foam is used, and the carbonization temperature is adjusted to 700°C and the carbonization time is adjusted to 6h to obtain the carbon foam material of this embodiment.

[0104] The specific surface area (BET) of this carbon foam material is 38.73 m². 2 / g, pore volume is 0.07cm³ 3 / g, with a micro-mesopore ratio of 61%.

[0105] Example 14

[0106] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the mass of kitchen waste powder is adjusted to 0.047g and the microwave time is adjusted to 0.7s, so the ratio of the volume of carbon foam material to the mass of biomass raw material is 1:0.03.

[0107] Example 15

[0108] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3), the mass of kitchen waste powder is adjusted to 1.88g and the microwave time is adjusted to 28.2s, so the ratio of the volume of carbon foam material to the mass of biomass raw material is 1:1.2.

[0109] Example 16

[0110] The biomass pyrolysis method in this embodiment is basically the same as that in Embodiment 1, except that in step 3), the microwave frequency is adjusted to 3.5 GHz.

[0111] Example 17

[0112] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1, except that in step 3), the microwave time is adjusted to 2 seconds.

[0113] Example 18

[0114] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1, except that in step 3), the microwave time is adjusted to 65s.

[0115] Example 19

[0116] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1, except that in step 2), the final moisture content of the kitchen waste powder is 1.25%.

[0117] Example 20

[0118] The biomass pyrolysis method in this embodiment is basically the same as that in embodiment 1, except that in step 2), the particle size of the kitchen waste powder is less than 50 mesh.

[0119] Example 21

[0120] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1, except that in step 1), the carbon foam material is cut to 16×14×7mm (1.568cm). 3 );

[0121] In step 3), place the kitchen waste powder on top of a single piece of carbon foam, close to the carbon foam, and keep everything else unchanged.

[0122] Example 22

[0123] The biomass pyrolysis method in this embodiment is basically the same as that in Example 1, except that in step 3), the interlayer spacing is 0.3 mm.

[0124] Comparative Example 1

[0125] The biomass pyrolysis method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the microwave power is adjusted to 32W, so the ratio of the volume of the carbon foam material to the microwave power is 1:20.

[0126] Comparative Example 2

[0127] The biomass pyrolysis method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the microwave power is adjusted to 815W, so the ratio of the volume of the carbon foam material to the microwave power is 1:520.

[0128] Comparative Example 3

[0129] The biomass pyrolysis method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), tungsten wire is used as the microwave absorbing material, and kitchen waste powder is filled between two tungsten wires. Everything else remains the same.

[0130] Test case

[0131] 1. The solid product prepared in Example 1 was subjected to Raman spectroscopy, SEM, and TEM testing, such as... Figures 1-3 As shown.

[0132] Figure 1 The image shows the Raman spectrum of the solid product prepared in Example 1. Figure 1 It can be seen that the Raman spectrum of carbon-based materials (solid products) contains a region located at 1350 cm⁻¹. -1 The nearby D peak is located at 1580cm. -1 The nearby G peak and located at 2700cm -1 The nearby 2D peak. When the peak intensity of the 2D peak is I 2D The peak intensity of G peak I G When the ratio is greater than 0.3, it indicates the presence of graphene sheet structure in the carbon material, and the I in the solid product... 2D / I G The value is 0.75, which indicates the presence of few-layer graphene structures in the solid product.

[0133] Figure 2 Here is an SEM image of the solid product from Example 1. Figure 3 This is a TEM image of the solid product from Example 1. Figure 2It can be seen that the product consists of smooth carbon nanofiber coils and carbon nanocrystal clusters, which is a typical heteroatom-doped graphene structure prepared through a thermal process; Figure 3 It can be seen that the product is composed of several sets of graphene lattice stripes with curved and wrinkled structures, which confirms that it has an extremely high degree of graphitization and the existence of graphene structure.

[0134] 2. The solid products, gaseous products, and liquid products prepared in the above embodiments and comparative examples were collected and measured to obtain the mass of the solid products, gaseous products, and liquid products, respectively; then the yield of solid products (%) = mass of solid products / mass of biomass raw materials × 100%; the yield of gaseous products (%) = mass of gaseous products / mass of biomass raw materials × 100%; the yield of liquid products (%) = mass of liquid products / mass of biomass raw materials × 100%.

[0135] Subsequently, the gaseous products were analyzed by gas chromatography. The composition of the gas samples was analyzed using a refinery gas analyzer. Hydrogen, carbon monoxide, carbon dioxide, and oxygen were detected using a thermal conductivity detector (TCD) channel, while hydrocarbon components such as methane and ethylene were detected using a flame ionization detector (FID) channel. The response factors of each gas component were calibrated using standard gases for quantitative analysis, and the mole fraction of each component in the gaseous products was calculated. The composition of the liquid products was analyzed for water content to obtain the mass fraction of tar and water.

[0136] The test results are shown in Table 1.

[0137] Table 1

[0138]

[0139] As shown in Table 1:

[0140] Examples 1-22 not only achieve high biomass feedstock conversion rates, but also yield solid graphene of better quality. 2D / I G All values ​​were greater than 0.3, with a maximum of 0.75, indicating that it possesses a few-layer graphene sheet structure and has high added value. While Comparative Examples 1-3 also achieved high conversion rates, their added value was lower, and the resulting solid product, graphene I... 2D / I G All values ​​were less than 0.3, indicating significantly poor quality.

[0141] Among them, the quality of the solid products graphene in Examples 14-22 was slightly lower than that in Example 1. This was because the reaction conditions in the biomass pyrolysis reaction deviated, resulting in incomplete or excessive reaction. The former would lead to incomplete carbonization of the biomass raw materials, with a large amount of amorphous carbon still present in the solid. The latter would cause the graphene sheets stripped by high-temperature flash evaporation to tend to stack, resulting in an increase in the number of graphene sheets and ultimately a decrease in the quality of the solid product.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for biomass pyrolysis, characterized in that, Includes the following steps: Biomass feedstock is brought into contact with carbon foam material, and microwaves are applied under an inert atmosphere to generate plasma with a temperature of not less than 3000K, causing the biomass feedstock to undergo a pyrolysis reaction. The volume ratio of the carbon foam material to the microwave power is 1:(25-500); where the volume is measured in cm³. 3 The unit of power is W.

2. The biomass pyrolysis method according to claim 1, characterized in that, The specific surface area (BET) of the carbon foam material is ≥25m². 2 / g, and / or, total pore volume ≥0.04cm³ 3 / g, and / or, micro-mesoporous ratio ≥50%.

3. The biomass pyrolysis method according to claim 2, characterized in that, The carbon foam material is obtained by carbonizing carbonizable organic foam at 700-1200℃ for 0.5-6 hours; The organic foam includes at least one of melamine foam, polyimide foam, and phenolic resin foam.

4. The biomass pyrolysis method according to any one of claims 1-3, characterized in that, The volume ratio of the carbon foam material to the mass of the biomass raw material is 1:(0.05-1); where the volume unit is cm. 3 The unit of mass is g.

5. The biomass pyrolysis method according to any one of claims 1-4, characterized in that, The frequency of the microwave is 2.45-3.20 GHz.

6. The biomass pyrolysis method according to any one of claims 1-5, characterized in that, The pyrolysis reaction is intermittent; The ratio of the microwave application time to the mass of the biomass raw material is (3-60):1; where the unit of application time is s and the unit of mass is g.

7. The biomass pyrolysis method according to any one of claims 1-6, characterized in that, The biomass feedstock has a moisture content of <0.5wt% and / or a particle size of <100 mesh.

8. The biomass pyrolysis method according to any one of claims 1-7, characterized in that, The carbon foam material includes a first carbon foam material and a second carbon foam material; the first carbon foam material and the second carbon foam material are placed opposite each other to form a sandwich, and the biomass raw material is located in the sandwich; The spacing between the interlayers is 0.5-10 mm.

9. The biomass pyrolysis method according to any one of claims 1-8, characterized in that, The inert atmosphere includes nitrogen and / or argon, and the oxygen content in the inert atmosphere is <0.1%.

10. The biomass pyrolysis method according to any one of claims 1-9, characterized in that, The biomass raw materials include at least one of activated carbon, kitchen waste, rice husks, straw, and bamboo powder.

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