Method for preparing biomass mesoporous carbon in non-activation mode and application

Abstract

The invention relates to the technical field of mesoporous carbon material preparation, in particular to a high-temperature mesoporous carbon preparation method which comprises the following steps: S1, mixing a metal halide and an inorganic hydrogen bond donor, and heating and stirring until a solution is clear to obtain an inorganic eutectic solvent; s2, mixing the inorganic eutectic solvent and a biomass raw material for reaction; s3, filtering and washing the material obtained in the step S2; and S4, carbonizing the material obtained in the step S3 in a high-temperature inert atmosphere to obtain the high-temperature mesoporous carbon. According to the method, the wood fiber biomass such as the lowest-value straw, the lowest-value bamboo and the lowest-value wood dust is directly used as raw materials, component separation does not need to be conducted on the wood fiber biomass, and high-value utilization of a large amount of low-value wood fiber biomass can be achieved. The method is relatively simple in process, relatively mild in condition and relatively high in product yield, and an activating agent does not need to be used. The biomass mesoporous carbon prepared by the method also has a high specific surface area in a huge mesoporous volume state, and the specific capacitance in an alkaline electrolyte exceeds 260F / g.

Description

Technical Field

[0001] The invention relates to the technical field of mesoporous carbon material preparation, in particular to a method for non-activation preparation of biomass mesoporous carbon and its application. Background Art

[0002] Mesoporous carbon refers to carbon materials with pores concentrated in the range of 2 to 50 nm. It has excellent physical and chemical properties, such as adjustable porosity of the ordered structure, high specific surface area, and high chemical stability, thermal stability, and mechanical stability. This makes it extremely versatile in applications such as catalysis, energy storage, carbon dioxide capture, water purification, and adsorption. Waste biomass is a very promising and sustainable precursor for the preparation of mesoporous carbon materials. Since a large amount of agricultural and forestry waste biomass is generated annually around the world, converting this waste biomass into high-value materials can not only increase the value of these materials, but also solve the environmental problems caused by incineration.

[0003] In recent years, the preparation of mesoporous carbon using biomass as raw materials is mainly done through chemical activation and template methods. Among them, another route for preparing mesoporous carbon is to use the template method, using rigid materials such as mesoporous SiO2 as templates, filling the template pores with biomass carbon precursors, and then removing the template to replicate its pore structure. This type of method requires the preparation of a template with an ordered morphology first, and the subsequent removal of the template requires the use of reagents such as hydrofluoric acid, which has certain safety risks. At present, the industry generally adopts chemical activation to form pores in biomass carbon. Common chemical activators include KOH, H3PO4 and salts. The pore-forming effect of these activators is mainly achieved at high temperatures. For example, the activation temperature of KOH is 700-900°C, the activation temperature of salt reagents is above 500°C, and the activation temperature of phosphoric acid is around 500°C. Carbon materials prepared by chemical activation generally have a large specific surface area (greater than 1000m 2 Although the carbonization process is relatively simple, the carbonization process itself is notoriously complex. However, the carbonization process itself is characterized by a high pore size (~1000 ppm / g), with the pore structure primarily consisting of micropores, and the mesopore fraction generally less than 50%. However, the use of large amounts of activators at high temperatures can easily lead to volatilization pollution and increased corrosion in the carbonization furnace. Therefore, a low-cost, green, safe, and efficient method for preparing biomass mesoporous carbon without the need for activators is urgently needed. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art and provide a method for preparing high-porosity mesoporous carbon. An inorganic deep eutectic solvent is used to react with biomass at a relatively low temperature. The inorganic deep eutectic solvent swells the biomass and simultaneously generates a template, giving the material a porous structure. High-temperature activation then significantly increases the degree of carbonization, thereby enhancing the material's conductivity and potential application in the field of electrode materials.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A method for preparing high-temperature mesoporous carbon comprises the following steps:

[0007] S1: Mixing a metal halide and an inorganic hydrogen bond donor, heating and stirring until the solution is clear to obtain an inorganic deep eutectic solvent;

[0008] S2: mixing the inorganic deep eutectic solvent and the biomass raw material for reaction;

[0009] S3: Filter and wash the material obtained in step S2;

[0010] S4: Carbonizing the material obtained in step S3 in a high-temperature inert atmosphere to obtain high-temperature mesoporous carbon.

[0011] Furthermore, the metal halide includes at least one of zinc chloride, aluminum chloride, tin chloride and lead chloride.

[0012] Furthermore, the inorganic hydrogen bond donor includes at least one of phosphoric acid, boric acid, and ammonium chloride.

[0013] Furthermore, in step S1, the molar ratio of the metal halide to the inorganic hydrogen bond donor is 1:0.1-10.

[0014] Preferably, the molar ratio of the metal halide to the hydrogen bond donor is 0.3:1.

[0015] Furthermore, in step S1, the temperature of the heating and stirring is 60-140°C.

[0016] Preferably, the temperature of the heating and stirring is 90°C.

[0017] Furthermore, in step S2, the biomass raw material is at least one of native biomass and biomass separation and decomposition products.

[0018] Furthermore, in step S2, the solid-liquid ratio of the biomass raw material and the inorganic deep eutectic solvent is 1 g:1-30 mL.

[0019] Preferably, the solid-to-liquid ratio of the biomass raw material to the deep eutectic solvent is 1 g:5 mL.

[0020] Furthermore, in step S2, the reaction temperature of the mixed reaction is 100-400° C.; and the reaction time of the mixed reaction is 0.5-30 h.

[0021] Preferably, the reaction temperature is 300° C.; and the reaction time of the mixing reaction is 2 h.

[0022] Furthermore, in step S4, the high temperature is 450-1200°C.

[0023] Furthermore, in step S4, the carbonization time is 0.5 to 30 hours.

[0024] It is worth noting that in the present invention, metal halides and hydrogen bond donors are first used to form IDES (inorganic low eutectic solvent) with a developed hydrogen bond network, so that the biomass can swell at 10-30°C. At a lower temperature (100-400°C), IDES reacts when heated to generate fine metal salt templates inside the biomass, so that the prepared carbon material has a huge mesoporous volume. High-temperature carbonization is then carried out to greatly improve the degree of carbonization, thereby improving the conductivity of the material and having application value in the field of electrode materials.

[0025] The beneficial effects of the present invention are:

[0026] 1) The method of the present invention directly uses the lowest-value lignocellulosic biomass such as straw, bamboo and sawdust as raw materials, without the need to separate the components of the lignocellulosic biomass, and can achieve high-value utilization of bulk low-value lignocellulosic biomass.

[0027] 2) The method of the present invention has a simple process, mild conditions, a high product yield, and the IDES used can be recycled and dissolved after forming a template.

[0028] 3) The biomass mesoporous carbon prepared by the method of the present invention has a large mesoporous volume and a high specific surface area, and its specific capacitance in alkaline electrolyte can exceed 260F / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a simplified process flow diagram of the present invention;

[0030] Figure 2 This is a scanning electron microscope image of the high-temperature mesoporous carbon material in Example 3;

[0031] Figure 3 The constant current charge and discharge curves of Examples 1-3 are shown. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0033] Example 1

[0034] A high-temperature mesoporous carbon material is prepared by the following method:

[0035] Zinc chloride powder and 85wt% phosphoric acid solution were mixed in a 0.4:1 molar ratio and heated at 90°C with stirring until the solution became clear. Heating and stirring were continued for 12 hours to remove excess water from the raw materials, yielding IDES. 40g of bamboo powder (a biomass raw material) was added to a crucible and mixed with 100mL of IDES. After stirring, the mixture was heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solids were then washed with an acidic solution and then with water to a constant pH. The mesoporous carbon material was then dried. The dried mesoporous carbon was then placed in a crucible and carbonized at 800°C under a nitrogen atmosphere for 2 hours to yield high-temperature biomass mesoporous carbon.

[0036] Example 2

[0037] A high-temperature mesoporous carbon material is prepared by the following method:

[0038] Zinc chloride powder and solid phosphoric acid were mixed in a molar ratio of 0.4:1 (heated to melt), then stirred and heated at 90°C until the solution clarified to obtain IDES. 30g of biomass raw material straw powder was added to a crucible and mixed with 100mL of IDES. After stirring evenly, the mixture was heated at 300°C for 2h. After the reaction, the resulting solid-liquid mixture was cooled to room temperature, filtered, and then the solid matter was washed with hydrochloric acid and water in sequence until the pH was constant. After drying, the mesoporous carbon material was obtained. The dried mesoporous carbon was placed in a crucible and carbonized at 800°C in a nitrogen atmosphere for 2h to obtain high-temperature biomass mesoporous carbon.

[0039] Example 3

[0040] A mesoporous carbon material is prepared by the following method:

[0041] Tin chloride powder, solid phosphoric acid, and boric acid powder were mixed (heated to melt) in a molar ratio of 0.6:1:0.2, and then stirred and heated at 90°C until the solution was clear to obtain IDES. 20g of the biomass raw material wheat straw was added to a crucible and mixed with 100mL of IDES. After stirring evenly, the mixture was heated at 300°C for 2h. After the reaction, the solid-liquid mixture was cooled to room temperature, filtered, and then the solid matter was washed with an acidic solution and water to a constant pH. After drying, the mesoporous carbon material was obtained. The dried mesoporous carbon was placed in a crucible and carbonized at 800°C in a nitrogen atmosphere for 2h to obtain a high-temperature mesoporous carbon material.

[0042] The obtained materials were subjected to SEM testing. Figure 2 shown.

[0043] Comparative Example 1

[0044] A mesoporous carbon material is prepared using biomass as raw material. The specific method is as follows:

[0045] Zinc chloride powder and 85wt% phosphoric acid solution were mixed in a 0.4:1 molar ratio and heated at 90°C with stirring until the solution became clear. Heating and stirring were continued for 12 hours to remove excess water from the raw materials, yielding IDES. 40g of bamboo powder, a biomass raw material, was added to a crucible and mixed with 100mL of IDES. After stirring, the mixture was heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature, filtered, and the solids were washed with an acidic solution and then with water to a constant pH. The mesoporous carbon material was obtained after drying.

[0046] Comparative Example 2

[0047] A carbon material was prepared using biomass as a raw material. Unlike Comparative Example 1, phosphoric acid was omitted and zinc chloride was used alone. The specific method was as follows: 30 g of sawdust (a biomass raw material) was mixed with 100 g of zinc chloride and reacted at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solid was then washed with acid and then water until the pH was constant. The carbon material was then dried.

[0048] Comparative Example 3

[0049] A carbon material was prepared using biomass as raw material. Unlike Comparative Example 1, zinc chloride powder was not added, and only phosphoric acid solution was used. The specific method was as follows: 40g of the biomass raw material sawdust was mixed with 100mL of 85%wt phosphoric acid in a crucible, stirred evenly, and then heated at 300°C for 2h. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solid material was then washed with acid and water to a constant pH, and dried. The dried material was placed in a crucible and carbonized at 800°C under a nitrogen atmosphere for 2h to obtain a high-temperature mesoporous carbon material.

[0050] Comparative Example 4

[0051] Using DES as a comparison, choline chloride powder and lactic acid were mixed in a 1:1 molar ratio and then heated at 90°C with stirring until the solution clarified. 30 g of biomass straw powder and 100 mL of DES were added to a crucible, mixed, and stirred until uniformly mixed. The mixture was then heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solids were then washed with an acidic solution and then with water to a constant pH, and dried to obtain a carbon material. The dried material was then placed in a crucible and carbonized at 800°C under a nitrogen atmosphere for 2 hours to produce a high-temperature mesoporous carbon material.

[0052] Experimental Example 1

[0053] The carbon materials or high-temperature mesoporous carbon materials of Examples 1-3 and Comparative Examples 1-4 were tested using a nitrogen adsorption-desorption method, and the specific surface area and pore volume were calculated, and the mesoporous ratio was calculated. A blank control was also set up (30 g of bamboo powder was placed in a crucible and heated at 300°C for 2 hours. The obtained biochar was washed with acid and water and dried. The dried powder was placed in a crucible and heated in a nitrogen environment at 800°C for 2 hours to obtain a high-temperature mesoporous carbon material). The results are shown in Table 1:

[0054] Table 1

[0055]

[0056]

[0057] As shown in the table above, the high-temperature mesoporous carbon materials prepared using bamboo powder, straw powder, and wheat straw as biomass feedstocks in Examples 1-3 all achieved a mesopore ratio of approximately 80%. Compared to high-temperature carbon materials prepared without the addition of metal halides, inorganic hydrogen bond donors, or using other deep eutectic solvents (Comparative Examples 2-4), the specific surface area, pore volume, and mesopore ratio were more than doubled, demonstrating improved adsorption and storage capabilities.

[0058] Experimental Example 2

[0059] The specific capacitance of the carbon materials or high-temperature mesoporous carbon materials of Examples 1-3 and Comparative Examples 1-4 was detected by mixing polyvinylidene fluoride (2 wt% dissolved in N-methylpyrrolidone), acetylene black and the above carbon material or high-temperature mesoporous carbon material in a ratio of 8:1:1 and evenly coating the mixture on graphite paper. The loading amount of the carbon material was 3-5 mg / cm 2 After being fully dried, it was used as a working electrode and tested in a 6M KOH solution. The counter electrode was graphite and the reference electrode was Hg / HgO. The experimental results are shown in Table 2:

[0060] Table 2

[0061] Group Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Specific capacitance (1A / g) 268 287 274 124 133 141 27

[0062] As can be seen from the above table, the high-temperature mesoporous carbon materials of Examples 1-3 have a specific capacitance that is more than double that of the carbon material without high-temperature carbonization (Comparative Example 1), and are more than ten times higher than the high-temperature carbon materials without the addition of metal halides and inorganic hydrogen bond donors (Comparative Examples 2-4), and are more than ten times higher than the high-temperature carbon materials prepared using other low eutectic solvents (Comparative Example 4).

[0063] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A method for preparing high-temperature mesoporous carbon, characterized in that: The following steps are involved: S1: Mixing a metal halide and an inorganic hydrogen bond donor, heating and stirring until the solution is clear to obtain an inorganic deep eutectic solvent; S2: mixing the inorganic deep eutectic solvent and the biomass raw material for reaction; S3: Filter and wash the material obtained in step S2; S4: Carbonizing the material obtained in step S3 in a high-temperature inert atmosphere to obtain high-temperature mesoporous carbon.

2. The preparation method according to claim 1, wherein: The metal halide includes at least one of zinc chloride, aluminum chloride, tin chloride and lead chloride.

3. The preparation method according to claim 1, wherein: The inorganic hydrogen bond donor includes at least one of phosphoric acid, boric acid, and ammonium chloride.

4. The preparation method according to claim 1, wherein: In step S1, the molar ratio of the metal halide to the inorganic hydrogen bond donor is 1:0.1-10.

5. The preparation method according to claim 1, wherein: In step S2, the biomass raw material is at least one of primary biomass and biomass separation and decomposition products.

6. The preparation method according to claim 1, wherein: In step S2, the solid-liquid ratio of the biomass raw material to the inorganic deep eutectic solvent is 1:1 to 30.

7. The preparation method according to claim 1, wherein: In step S2, the reaction temperature of the mixing reaction is 100-400° C.; the reaction time of the mixing reaction is 0.5-30 h.

8. The preparation method according to claim 1, wherein: In step S4, the high temperature is 600-1100°C.

9. The preparation method according to claim 1, wherein: In step S4, the carbonization time is 2 to 5 hours.

10. Use of the high-temperature mesoporous carbon material prepared by the preparation method according to any one of claims 1 to 9 in the preparation of capacitors.

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