Preparation and application of a biowaste-derived carbon aerogel material

Abstract

The present invention belongs to the field of gas storage technology and provides a method for preparing and applying a biowaste-derived carbon aerogel material. The method comprises: physically crushing polysaccharide-containing biomass to less than 200 μm, performing alkaline hydrolysis, and then dissolving and purifying the material using an organic solvent to obtain a precursor; immersing the precursor in a salt solution and placing it at -30°C to -25°C for 24 to 32 hours to allow gelation to occur, thereby obtaining a salt-containing aerogel; and carbonizing the salt-containing aerogel at 600-1000°C under an inert atmosphere. The aerogel has low production costs, is widely available, and possesses a controllable pore structure. The pore size can be adjusted to effectively capture hydrogen molecules, thus possessing excellent practical application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas storage, and in particular relates to the preparation and application of a biowaste-derived carbon aerogel material. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] The excessive use of fossil fuels not only causes serious environmental pollution but also exacerbates energy shortages, making the search for cleaner alternative energy sources increasingly important and sensible. Hydrogen is considered an environmentally friendly energy source with advantages such as low cost, high calorific value, and zero pollution, making it the best alternative to fossil fuels. Currently, there are three main ways to store hydrogen: liquefied hydrogen storage, compressed hydrogen storage, and solid-state hydrogen storage. Although liquefied hydrogen storage and compressed hydrogen storage are mature technologies in the commercial field, they are still not suitable for large-scale use due to the risks of leakage and explosion, high energy consumption, and low storage capacity. Solid-state hydrogen storage has the advantages of low operating pressure, high safety, and high storage density, making it an ideal way to store hydrogen. Solid-state hydrogen storage mainly stores hydrogen in the pore structure of the material, so adsorption materials with a porous structure and high porosity play an important role in solid-state hydrogen storage.

[0004] Aerogels are three-dimensional, highly porous materials derived from organic, inorganic, or hybrid molecular precursors. Due to their high porosity, high specific surface area, and low density, they hold broad application prospects in gas adsorption. Furthermore, the surface chemical composition of aerogels can be customized and modified to achieve gas capture. Rapid economic development in recent years has led to the generation of large quantities of agricultural, food, and clothing waste. Recycling these wastes for the production of biomass aerogels holds great potential. This not only addresses the significant energy consumption required for traditional waste disposal and significantly reduces air and water pollution, but also significantly reduces production costs by using biowaste as a precursor for biomass aerogels. Converting biowaste into biodegradable aerogels is an important sustainable process. However, since aerogels are mostly mesoporous or macroporous materials, adsorption of small molecule gases remains challenging. Furthermore, the complex composition of biomass waste makes it difficult to prepare aerogels with good hydrogen adsorption properties. Therefore, developing a novel method to control the pore size of aerogels to a certain extent is of great practical significance and research value for adsorption applications. Summary of the Invention

[0005] To address the challenges of existing technologies, the present invention proposes the preparation and application of biowaste-derived carbon aerogel materials. The aerogels involved are low-cost, widely available, and possess a tunable pore structure. By adjusting the pore size, they can effectively capture hydrogen molecules, thus possessing promising practical applications.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a biowaste-derived carbon aerogel material, comprising:

[0008] The polysaccharide-containing biomass is physically crushed to less than 200 μm, alkaline hydrolyzed, and then dissolved and purified using an organic solvent to obtain a precursor;

[0009] The precursor is immersed in a salt solution and placed at -30°C to -25°C for 24 to 32 hours to gel to obtain a salt-containing aerogel;

[0010] The salt-containing aerogel is carbonized at 600-1000° C. under an inert atmosphere to obtain the aerogel.

[0011] The molten salt method involves mixing molten salt and reactants in a specific ratio, heating the mixture to melt it, and then cooling it to remove the soluble salts. Research has found that by using the molten salt method to prepare biomass carbon aerogels, micropores of varying sizes can be etched into the aerogel by controlling the type of molten salt, thereby producing biomass carbon aerogels with a hierarchical porous structure. For biomass aerogels used as hydrogen adsorbents, the small size of hydrogen molecules and the presence of hierarchical porosity will greatly facilitate the storage and promotion of hydrogen in the aerogels.

[0012] At the same time, due to the complex composition of polysaccharide biomass waste, in order to better improve the hydrogen gas adsorption performance of biomass aerogel, the present invention uses alkaline hydrolysis and organic microwave treatment to purify the polysaccharide biomass waste, converting it into an aerogel precursor, effectively improving the specific surface area, having a hierarchical porous structure, and having a strong adsorption capacity for hydrogen molecules.

[0013] The second aspect of the present invention provides a biowaste-derived carbon aerogel material prepared by the above method.

[0014] The third aspect of the present invention provides the use of the above-mentioned biowaste-derived carbon aerogel material in the preparation of a hydrogen gas adsorbent.

[0015] Beneficial effects of the present invention

[0016] One or more technical solutions of the present invention have the following beneficial effects:

[0017] (1) The present invention provides a method for converting general polysaccharide biomass waste into an aerogel precursor, which is purified by alkaline hydrolysis and organic microwave treatment. The method is simple, efficient and low-cost.

[0018] (2) The present invention subsequently immerses the obtained aerogel precursor in a salt solution, undergoes directional freeze-drying, and directional ion diffusion of the high-concentration salt solution, forming a dense area at the bottom and a connected porous structure at the top, thereby forming a gel with a concentration gradient. Furthermore, after the carbonization process, the salt remaining inside the gel is etched to produce a large number of micropores. Due to the uneven pore structure caused by the different concentration gradients, the prepared aerogel has a continuous gradient pore structure. Its pore structure is richer than that of conventional methods, which can effectively improve the capture of hydrogen molecules.

[0019] (3) The carbon source materials for preparing the carbon aerogels described in the present invention are widely available and low in cost, including urban waste such as waste corrugated paper, disposable chopsticks, and discarded milk cartons; food waste such as melon seed shells, brown sugar residue, fig kernels, MSG residue, and coffee grounds; agricultural and forestry waste such as pine needles, palm leaves, pistachio shells, peanut skins, pine nut shells, and kale stems; and waste residues of traditional Chinese medicine such as coptis root, isatis root, forsythia, reed root, and liquorice residue. This achieves high-value utilization of waste and greatly reduces production costs.

[0020] (4) The present invention uses biowaste as a carbon source, resulting in the aerogel produced during the production process containing elements such as N, P, K, and S, which gives the carbon aerogel smaller micropores and a larger specific surface area; due to the synergistic effect of heteroatoms, the co-doped carbon aerogel can change its chemical properties and provide additional active sites, which is beneficial to the adsorption of hydrogen gas.

[0021] (5) The present invention uses freeze-drying technology to prepare aerogels, which avoids the shortcomings of supercritical drying, such as long cycle, high price, and complex operation.

[0022] (6) The carbon aerogel prepared by the present invention has a high specific surface area, a hierarchical porous structure, and a strong adsorption capacity for hydrogen molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 This is a physical picture of the ZnCl2 / paper corrugated cellulose carbon aerogel prepared in Example 1 of the present invention.

[0025] Figure 2 This is the SEM image of ZnCl2 / paper corrugated cellulose carbon aerogel in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0027] A method for preparing carbon aerogel material from biological waste comprises the following steps:

[0028] (1) The biomass material containing polysaccharides is physically crushed, then subjected to alkaline hydrolysis, and then dissolved and purified using an organic solvent to generate a precursor material for preparing a carbon aerogel material;

[0029] (2) Preparing a precursor of a carbon aerogel material, then pouring the solution into a mold and immersing it in a salt solution to gel; carbonizing the gel under a nitrogen atmosphere to obtain the final carbon aerogel

[0030] Furthermore, the biomass material is physically crushed to a size below 200 μm and then treated with 10% NaOH for 12 hours while mechanically stirring. The resulting alkali-treated material is then microwave-purified in an organic solvent such as phenol or acetone in a microwave reactor to produce a precursor material for preparing carbon aerogel materials.

[0031] Furthermore, the carbon source materials of the carbon aerogel include urban waste such as waste corrugated paper, disposable chopsticks, and waste milk cartons; food waste such as melon seed shells, brown sugar residue, fig cores, MSG residue, and coffee grounds; agricultural and forestry waste such as pine needles, palm leaves, pistachio shells, peanut skins, pine nut shells, and kale stems; and traditional Chinese medicine waste such as coptis root, isatis root, forsythia, reed root, and licorice residue.

[0032] Furthermore, the selected soaking salt solution includes alkali metal halides such as RbCl2, CsCl, ZnCl2, KCl, CaCl2; nitrates such as Ce(NO3)3, Pb(NO3)2, NH4NO3, KNO3, NaNO3;

[0033] Furthermore, the carbonization treatment is specifically as follows: in a tubular furnace, after ventilation for 30 minutes under a nitrogen atmosphere, the temperature is increased to 500°C at a heating rate of 5°C / min, and after keeping warm for 1-3 hours, the temperature is further increased to a target temperature of 600-1000°C at a heating rate of 5°C / min, and kept warm at the target temperature for 2-6 hours, and finally cooled naturally to room temperature.

[0034] Furthermore, the method further comprises: dissolving the precursor in water, adding the precursor to an alkaline urine system to dissolve the cellulose, and dissolving the precursor at a low temperature until no particles are formed to obtain a translucent gel;

[0035] The alkaline urea system consists of NaOH, urea and water, and the mass ratio of NaOH, urea and water is 7:12:81-85.

[0036] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0037] In the following examples, the gas adsorption and desorption cycle test is a CO2 cycle test: test temperature: 25°C; test pressure range: 0-1 bar.

[0038] Example 1 ZnCl2 / paper corrugated cellulose carbon aerogel

[0039] Cut the waste corrugated paper into small pieces, crush and sieve it with a wall breaker. Add it to a 10% NaOH solution with mechanical stirring and stir continuously for 12 hours. Then collect the suspended matter and soak it in a phenol solution (pure phenol (AR, 99.5%), transfer it to a microwave reactor, microwave it at 120°C for 20 minutes, and the microwave power is 10w. The obtained material is repeatedly washed with deionized water until it is neutral, put it into a mold, and soak it in a weighed ZnCl2 salt solution (concentration is 1.5mol / L). It is placed in a refrigerator at minus 30°C for 24 hours, and then freeze-dried in a freeze dryer (freeze-drying temperature: -40°C; pressure: 0.01mpa) for 2 days until the moisture is completely removed. In a tubular furnace, with nitrogen as the protective atmosphere, the salt-containing aerogel is carbonized at a carbonization temperature of 600°C for 2 hours and taken out after cooling. The final carbon aerogel is obtained.

[0040] The ZnCl2 / paper corrugated cellulose carbon aerogel material has a hierarchical porous structure, in which the presence of the microporous structure plays a positive role in better capturing hydrogen molecules. After 2,000 cycles of gas adsorption and desorption, the adsorption volume still retains 80%.

[0041] Example 2 NH4NO3 / licorice residue carbon aerogel

[0042] The liquorice residue was washed several times, crushed and sieved using a wall-breaking machine. The residue was then added to a 10% NaOH solution with mechanical stirring and stirred continuously for 12 hours. The suspended material was then collected and immersed in a phenol solution (pure phenol (AR, 99.5%)). The suspension was then transferred to a microwave reactor and microwaved at 120°C for 20 minutes at a microwave power of 10W. The resulting material was repeatedly washed with deionized water until neutral and dispersed in water for later use.

[0043] The cellulose was dissolved in an alkaline-urea system (NaOH:urea:water = 7:12:81) at 1% (mass fraction relative to the alkaline-urea system) of the raw materials. The solution dissolved at low temperature until free of particles, yielding a translucent gel. The gel was dispensed into molds and immersed in a prepared NH4NO3 salt solution (1.5 mol / L) in a -30°C refrigerator for 24 hours. The gel was then freeze-dried in a freezer (freeze-drying temperature: -40°C; pressure: 0.01 MPa) for 2 days to completely remove the moisture. The salt-containing aerogel was then carbonized in a tubular furnace with nitrogen as a protective atmosphere at 600°C for 2 hours, then removed after cooling.

[0044] The NH4NO3 / licorice residue aerogel material has a hierarchical porous structure, in which the presence of microporous structure plays a positive role in better capturing hydrogen molecules. After 2000 cycles of gas adsorption and desorption, the adsorption volume still retains 80%.

[0045] Comparative Example 1 was not subjected to alkaline hydrolysis and dissolution purification treatment

[0046] Waste corrugated paper was cut into small pieces, crushed and sieved using a wall breaker, placed in a mold, and immersed in a weighed ZnCl2 salt solution (concentration: 1.5 mol / L). The pieces were placed in a refrigerator at -30°C for 24 hours, and then freeze-dried in a freeze dryer (freeze-drying temperature: -40°C; pressure: 0.01 MPa) for 2 days to completely remove the moisture. The salt-containing aerogel was carbonized in a tubular furnace with nitrogen as a protective atmosphere at a carbonization temperature of 600°C for 2 hours. The pieces were then removed after cooling. This resulted in the final carbon aerogel.

[0047] The test results show that after 2,000 cycles of gas adsorption and desorption, the adsorption volume of the obtained carbon aerogel only retains 30%.

[0048] Comparative Example 2 was not immersed in a saline solution

[0049] Cut the waste corrugated paper into small pieces, crush and sieve them using a wall breaker. Add them to a 10% NaOH solution with mechanical stirring and stir continuously for 12 hours. Then collect the suspended matter and soak it in a phenol solution (pure phenol (AR, 99.5%), transfer it to a microwave reactor, microwave it at 120°C for 20 minutes, and the microwave power is 10w. The obtained material is repeatedly washed with deionized water until it is neutral, put it into a mold, soak it in water, and place it in a refrigerator at minus 30°C for 24 hours. Then, freeze-dry it in a freeze dryer (freeze-drying temperature: -40°C; pressure: 0.01mpa) for 2 days until the moisture is completely removed. In a tubular furnace, with nitrogen as the protective atmosphere, carbonize the salt-containing aerogel at a carbonization temperature of 600°C and a time of 2 hours. Take it out after cooling. The final carbon aerogel is obtained.

[0050] The test results show that after 2,000 cycles of gas adsorption and desorption, the adsorption volume of the obtained carbon aerogel only retains 60%.

[0051] Comparative Example 3: Alkaline Urea System Not Added

[0052] Licorice residue was washed several times, crushed and sieved using a wall breaker. The residue was then added to a 10% NaOH solution with mechanical stirring and stirred continuously for 12 hours. The resulting suspension was then collected and immersed in a phenol solution (pure phenol (AR, 99.5%)). The suspension was then transferred to a microwave reactor and microwaved at 120°C for 20 minutes at a microwave power of 10 W. The resulting material was repeatedly washed with deionized water until neutral.

[0053] The obtained material was added to a mold, immersed in the prepared NH4NO3 salt solution (concentration of 1.5 mol / L), placed in a refrigerator at minus 30°C for 24 hours, and then freeze-dried in a freeze dryer (freeze-drying temperature: -40°C; pressure: 0.01 MPa) for 2 days until the moisture was completely removed. In a tubular furnace, with nitrogen as the protective atmosphere, the salt-containing aerogel was carbonized at a carbonization temperature of 600°C for 2 hours. After cooling, it was taken out to obtain carbon aerogel.

[0054] The test results show that after 2000 cycles of gas adsorption and desorption, the adsorption volume of the obtained carbon aerogel only retains 20%.

[0055] From the comparison between Example 1 and Comparative Example 1, it can be seen that the carbon aerogel prepared from polysaccharide biomass waste after alkaline hydrolysis and organic matter microwave treatment for purification has a higher specific surface area and hierarchical porous structure, and its adsorption capacity for hydrogen molecules is significantly improved.

[0056] From the comparison between Example 1 and Comparative Example 2, it can be seen that the biomass carbon aerogel prepared by the molten salt method has a hierarchical porous structure and has a better adsorption capacity for hydrogen.

[0057] From the comparison between Example 2 and Comparative Example 2, it can be seen that the biomass carbon aerogel prepared by dissolving the cellulose in the precursor using the alkaline urine system has a better adsorption capacity for hydrogen.

[0058] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing biowaste-derived carbon aerogel material, characterized in that: include: The polysaccharide-containing biomass is physically crushed to less than 200 μm, alkaline hydrolyzed, and then dissolved and purified using an organic solvent to obtain a precursor; The precursor is immersed in a salt solution, placed at -30°C to -25°C for 24 to 32 hours, freeze-dried, and gelled to obtain a salt-containing aerogel; The salt-containing aerogel is carbonized at 600-1000° C. under an inert atmosphere to obtain the aerogel.

2. The method for preparing biowaste-derived carbon aerogel material according to claim 1, wherein: The biomass containing polysaccharides includes: urban garbage waste, food waste, agricultural and forestry waste, and traditional Chinese medicine waste residue.

3. The method for preparing biowaste-derived carbon aerogel material according to claim 2, wherein: The municipal waste includes: waste corrugated paper, disposable chopsticks, and waste milk cartons; Alternatively, the food waste includes: melon seed peels, brown sugar residue, fig cores, MSG residue, coffee grounds; Alternatively, the agricultural and forestry wastes include: pine needles, palm leaves, pistachio shells, peanut skins, pine nut shells, kale stems; Or, the traditional Chinese medicine waste residue includes: coptis root, isatis root, forsythia suspensa, reed root, and liquorice residue.

4. The method for preparing biowaste-derived carbon aerogel material according to claim 1, wherein: The specific steps of the alkaline hydrolysis include: treating with 10% to 12% NaOH for 12 to 16 hours under mechanical stirring.

5. The method for preparing biowaste-derived carbon aerogel material according to claim 1, wherein: The specific steps of the dissolution and purification include: soaking the suspended matter after alkaline hydrolysis in phenol or acetone, and subjecting it to microwave treatment at 120° C. to 130° C. for 20 to 30 minutes.

6. The method for preparing biowaste-derived carbon aerogel material according to claim 1, wherein: In the salt solution, the salt includes: alkali metal halide and nitrate.

7. The method for preparing biowaste-derived carbon aerogel material according to claim 6, wherein: The alkali metal halide includes: RbCl2, CsCl, ZnCl2, KCl, CaCl2; Alternatively, the nitrate includes: Ce(NO3)3, Pb(NO3)2, NH4NO3, KNO3, and NaNO3.

8. The method for preparing biowaste-derived carbon aerogel material according to claim 1, wherein: The carbonization treatment specifically comprises the following steps: after ventilation in a nitrogen atmosphere for 30 minutes, heating to 500°C at a heating rate of 5°C / min, keeping the temperature for 1-3 hours, then continuing to heat to a target temperature of 600-1000°C at a heating rate of 5°C / min, keeping the temperature at the target temperature for 2-6 hours, and finally cooling naturally to room temperature; The method further comprises: dissolving the precursor in water, adding the precursor into an alkaline urine system to dissolve the cellulose, and dissolving the cellulose at a low temperature until no particles are formed to obtain a translucent gel; The alkaline urea system consists of NaOH, urea and water, and the mass ratio of NaOH, urea and water is 7:12:81-85.

9. Biowaste-derived carbon aerogel material prepared by the method according to any one of claims 1 to 8.

10. Use of the biowaste-derived carbon aerogel material according to claim 9 in the preparation of a hydrogen gas adsorbent.

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