A method for producing a molded porous carbon

Abstract

The present application belongs to the technical field of porous carbon, and discloses a preparation method of shaped porous carbon. The preparation method is to take wood as a base frame structure, introduce polymerizable molecules on the surface of the wood, facilitate the Van der Waals interaction between the abundant hydroxyl groups on the surface of the wood and the polymerizable molecules, in-situ reaction to generate a layer of closely adhered polymer, and directly obtain shaped porous carbon through high-temperature carbonization. The preparation method is simple, can be designed and prepared according to application requirements, can solve the technical problems that high porosity, fast mass transfer rate and non-destructive shaping of porous carbon materials cannot be achieved at the same time, and can realize large-scale production. The preparation method has expansibility, and the prepared shaped porous carbon has wide application potential and market prospect in the fields of gas separation, battery materials, monolithic electrodes and the like.

Description

Technical Field

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

[0002] Porous carbon materials possess advantages such as large specific surface area, well-developed pore structure, modifiable pore size and surface chemical properties, resistance to acid and alkali corrosion, good thermal and chemical stability, insolubility in water and organic solvents, and easy regeneration. They are widely used in gas-phase adsorption, liquid-phase adsorption, catalysts, energy, and medicine, playing a vital role in industrial production and daily life. However, currently synthesized porous carbon materials are in powder form. To meet practical application requirements, they must be molded using binders to improve mechanical strength and wear resistance. The presence of binders significantly reduces the porosity of the molded porous carbon, leading to a decline in its performance (CN106794443B). Therefore, molded carbon usually requires further activation and pore expansion, but this further reduces its mechanical strength and wear resistance (New Carbon Materials, 2000, 15:6-10). Direct preparation of self-supporting monolithic molded porous carbon has attracted widespread attention, with numerous related literature and patent reports in recent years (CN109734449B, CN110354803B). These monolithic porous carbons are primarily obtained from phenolic basic polymers through sol-gel and carbonization processes. While these self-supporting monolithic porous carbons possess abundant microporous structures and a certain degree of mechanical strength, they lack macropores that facilitate mass diffusion, thus restricting the diffusion behavior of molecules within them. Therefore, new preparation methods need to be explored. Summary of the Invention

[0003] This invention addresses the aforementioned problems by providing a method for preparing molded porous carbon with interconnected macropores. The porous carbon prepared by this method possesses advantages such as abundant pore structure, high strength, high wear resistance, and fast mass transfer rate, exhibiting excellent performance in adsorption separation, electrode materials, and catalyst supports. This method uses wood as a substrate framework structure, introducing polymerizable molecules onto its surface. Utilizing the attractive force of hydrogen bonds formed between the abundant hydroxyl groups on the wood surface and the polymer molecules, a tightly bonded polymer layer is generated in situ, followed by high-temperature carbonization to directly obtain molded porous carbon. This preparation method is simple, can be directionally designed and prepared according to application requirements, and can solve the technical challenge of simultaneously achieving high porosity, high mass transfer rate, and non-destructive molding in porous carbon materials, enabling large-scale production.

[0004] The technical solution of this invention:

[0005] A method for preparing shaped porous carbon, comprising the following steps:

[0006] (1) Add the hydroxyl-containing aromatic compound and the amine-containing compound sequentially to the alcohol-water mixed solvent, wherein the molar ratio of the hydroxyl-containing aromatic compound and the amine-containing compound is 1:10-10:1; and the volume ratio of alcohol to water is 1:1000-1000:1;

[0007] (2) Using wood as the base frame material, add it to the solution obtained in step (1) and let it stand to absorb the solution;

[0008] (3) Place the material obtained in step (2) into a sealed container containing aldehyde compounds, heat the sealed container to 20-90℃ and keep it for 0.5-96h, cool and take out the composite material; the molar ratio of aldehyde compounds to hydroxyl aromatic compounds is 2:1-10:1.

[0009] (4) Place the composite material obtained in step (3) in a carbonization furnace and carbonize it in an inert gas atmosphere to obtain shaped porous carbon; the carbonization conditions are a heating rate of 0.5-50℃ / min, heating to 500-1400℃, and holding at a constant temperature for 10-240min.

[0010] In step (1), the hydroxyl-containing aromatic compound is selected from one or more combinations of phenol, resorcinol, phloroglucinol, 2,3-xylenol and bisphenol A, with resorcinol being preferred.

[0011] In step (1), the amine-containing compound is one or more of aniline, p-phenylenediamine, benzidine, ethylenediamine, 1,6-hexanediamine, cyclohexanediamine, p-aminobenzoic acid, melamine and amino acids, preferably aniline.

[0012] In step (1), the alcohol-water mixed solvent is a mixed solvent of ethanol and water, a mixed solvent of methanol and water, or a mixed solvent of ethylene glycol and water.

[0013] In step (2), the base frame material is any wood, preferably one or more of pine, cypress, teak, cedar, camphor, willow, balsa wood and bamboo.

[0014] In step (3), the aldehyde compound is one or more of formaldehyde, propionaldehyde, butyraldehyde, furfural, glyoxal, 4-pyridinecarboxaldehyde, 2-pyridinecarboxaldehyde, benzaldehyde, terephthalaldehyde and isophthalaldehyde.

[0015] In step (4), the inert atmosphere is argon or nitrogen.

[0016] The present invention also provides an application of the shaped porous carbon in the separation of propylene and propane.

[0017] The beneficial effects of this invention are as follows: Using wood as a substrate, this invention utilizes the hydrogen bonding between the abundant hydroxyl groups on the wood surface and organic molecules to grow a layer of high-molecular-weight polymer material in situ on the wood surface through gas-phase induced polymerization. This polymer is then directly prepared into shaped porous carbon through a subsequent carbonization process. This shaped porous carbon retains the framework structure of wood, possesses abundant and interconnected mass transfer channels, and has functional sieve layers grown on its surface. The porous carbon material prepared by this invention combines the advantages of functional sieving performance, high porosity, high mechanical strength, and fast mass transfer rate. The size and morphology of the shaped porous carbon can be customized according to target requirements. The preparation method provided by this invention is scalable, and the prepared shaped porous carbon has broad application potential and market prospects in fields such as gas separation, battery materials, and monolithic electrodes. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the shaped porous carbon prepared in Example 1 of the present invention.

[0019] Figure 2 This is the breakthrough curve of the propylene / propane mixed gas separated by the shaped porous carbon prepared in Example 2 of the present invention.

[0020] Figure 3 This is the breakthrough curve of the porous carbon propylene / propane mixture formed in Comparative Example 1 of the present invention.

[0021] Figure 4 This is a comparison of the diffusion kinetics curves of propylene / propane in the porous carbon formed in Comparative Example 2 of the present invention. Detailed Implementation

[0022] To better understand the present invention, the following detailed description is provided in conjunction with embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0023] The preparation process of the molded polymer composite material is as follows:

[0024] Example 1.1

[0025] Weigh 0.06 mol of resorcinol and 0.04 mol of aniline and dissolve them in 5 mL of anhydrous ethanol, stirring until homogeneous. Weigh 3 g of cedar wood and add it to the above solution, allowing it to stand until saturated. Add 16 mL of formaldehyde aqueous solution to a sealed container. Transfer the cedar wood to a sealed container and heat to 90 °C for 18 h. After the reaction is complete, remove the molded polymer composite material, dry it to constant weight, and use it for later use. The sample is numbered and named P@B-1.

[0026] Example 1.2

[0027] Weigh 0.1 mol of phloroglucinol and 0.06 mol of p-phenylenediamine and dissolve them in 20 mL of ethanol / water mixture, stirring until homogeneous. Weigh 9 g of pine wood and add it to the above solution, allowing it to stand until saturated. Add 24 mL of formaldehyde aqueous solution to a sealed container. Transfer the pine wood to a sealed container and heat to 90 °C for 12 h. After the reaction is complete, remove the molded polymer composite material, dry it to constant weight, and use it for later use. The sample is numbered and named P@B-2.

[0028] Example 1.3

[0029] Weigh 0.02 mol of bisphenol A and 0.03 mol of 1,6-hexanediamine and dissolve them in 16 mL of anhydrous ethanol, stirring until homogeneous. Weigh 7 g of balsam wood and add it to the above solution, allowing it to stand until saturated. Add 12 mL of formaldehyde aqueous solution to a sealed container. Transfer the balsam wood to a sealed container and heat to 90 °C for 6 h. After the reaction is complete, remove the molded polymer composite material, dry it to constant weight, and use it for later use. The sample is numbered and named P@B-3.

[0030] Example 1.4

[0031] Weigh 0.07 mol of 2,3-xylenol and 0.08 mol of ethylenediamine and dissolve them in 10 mL of anhydrous ethanol, stirring until homogeneous. Weigh 6 g of willow wood and add it to the above solution, allowing it to stand until saturated. Add 18 mL of formaldehyde aqueous solution to a sealed container. Transfer the willow wood to a sealed container and heat to 90 °C for 24 h. After the reaction is complete, remove the molded polymer composite material, dry it to constant weight, and use it for later use. The sample is numbered and named P@B-4.

[0032] The process for preparing porous carbon is as follows:

[0033] Example 2.1

[0034] The prepared molded polymer composite material P@B-1 was placed in a ceramic boat in a carbonization furnace and, under an argon atmosphere, carbonized at 5 °C·min. -1 The temperature was increased from room temperature to 800℃ and held for 2 hours to produce porous carbon material. Figure 1 The image shows a scanning electron microscope (SEM) image of the prepared porous carbon. The prepared porous carbon possesses neatly arranged micron-sized macropores with an average channel width of approximately 20 μm. The carbon material surface is uniform, without delamination or cracking, indicating that the polymer material can grow uniformly on the wood surface due to hydrogen bonding. The sample is designated CPB-1-800.

[0035] Example 2.2

[0036] The prepared molded polymer composite material P@B-2 was placed in a ceramic boat in a carbonization furnace and, under a nitrogen atmosphere, carbonized at 3℃·min.-1 The temperature was increased from room temperature to 800℃ and held for 1.5 hours to produce porous carbon material, which was named CPB-2-800.

[0037] Example 2.3

[0038] The prepared molded polymer composite material P@B-3 was placed in a ceramic boat in a carbonization furnace and, under an argon atmosphere, carbonized at 10 °C·min. -1 The temperature was increased from room temperature to 700℃ and held for 2.5 hours to produce porous carbon material, which was named CPB-3-700.

[0039] Example 2.4

[0040] The prepared molded polymer composite material P@B-4 was placed in a ceramic boat in a carbonization furnace and, under a nitrogen atmosphere, carbonized at 5°C·min. -1 The temperature was increased from room temperature to 900℃ and held for 1 hour to produce porous carbon material, which was named CPB-4-900.

[0041] Example 3 (Static performance of porous carbon adsorbent)

[0042] Taking Example 2.1 as an example, after pyrolysis treatment at different carbonization temperatures, the static adsorption test of the obtained porous carbon with sieving function on single-component gases was performed:

[0043] Weigh 70-300 mg of porous carbon and degas it at 200 °C for 6-12 h. Use a Micromeritics ASAP 2020 physical adsorption analyzer to test the gas adsorption capacity at different equilibrium pressures and obtain adsorption isotherms at different temperatures. Sample numbers and static adsorption test results are shown in Table 1.

[0044] Table 1 Comparison of the static adsorption test results of porous carbon in Example 3 with its corresponding results.

[0045]

[0046] Example 4 (Dynamic separation performance of porous carbon adsorbent)

[0047] The molded porous carbon was crushed into 20-40 mesh particles and packed into the adsorption column of a dynamic breakthrough separation device. The device pipeline was purged with argon gas. A propylene / propane mixture was passed through the adsorption column at a flow rate of 2 mL / min (50:50 volume ratio) under conditions of 25°C and 1 bar. Gas chromatography was used to detect the composition and content of the outlet gas at the column outlet, and the adsorption capacity and dynamic selectivity of the porous carbon were calculated accordingly. The separation results of the mixed gas are shown below. Figure 2 As shown in Table 2.

[0048] Table 2 Comparison of the dynamic gas adsorption and separation performance results of porous carbon and its corresponding counterpart in Example 4.

[0049]

[0050]

[0051] Comparative Example 1 (Separation Selectivity Comparison)

[0052] The fir wood frame material from Example 1 was taken out separately and carbonized under the conditions of Example 2.1 to obtain a porous carbon material with only macropores, which was used as adsorbent A. Then, a dynamic separation test of the propylene-propane mixture was conducted according to the test conditions in Example 4. The dynamic breakthrough curve is shown below. Figure 3 As shown, the dynamic adsorption capacity of propylene is 1.66 mmol / g, the dynamic adsorption capacity of propane is 0.81 mmol / g, and the dynamic selectivity is 2, which can be calculated from the curve.

[0053] Porous carbon materials without polymer composites, which only have large pores, have a fast diffusion rate but lack excellent gas selectivity.

[0054] Comparative Example 2 (Diffusion Rate Comparison)

[0055] The polymer raw materials from Example 1 were polymerized separately in the same proportions and carbonized under the conditions of Example 2.1 to prepare a porous carbon material without macropores. This material was used as adsorbent B, and its diffusion rate at 25°C was tested using a smart gravimetric analyzer. The result was compared with that of Example 2.2. Figure 4 As shown, the propylene diffusion rate decreased significantly, to 2.5 × 10⁻⁶. -9 m 2 / s, which is only 60% of that of Example 2.2, and the adsorption capacity is also only 30% of that of Example 2.2.

[0056] Comparative Example 3 (Comparison of Different Substrate Materials)

[0057] The fir wood frame material from Example 1 was separately extracted and carbonized under the carbonization conditions of Example 2.4 to obtain a carbonaceous frame. Using this as a substrate material, shaped porous carbon was prepared using the same synthesis method as in Examples 1 and 2.1, serving as adsorbent C. Then, a dynamic separation test of a propylene-propane mixture was conducted according to the test conditions in Example 4. The calculated dynamic adsorption capacity for propylene was 0.32 mmol / g, and for propane, it was 0.01 mmol / g. Clearly, the dynamic adsorption capacity for propylene was significantly reduced, only 20% of that in Example 2.1. The significant reduction in propylene adsorption capacity is due to the lack of abundant hydroxyl functional groups on the surface of the carbonaceous frame material. This prevents the polymer material from being uniformly distributed within it, causing blockage of mass transfer channels and a significant decrease in mass transfer efficiency, resulting in a substantial reduction in adsorption capacity.

[0058] The above description is merely a specific implementation example of this invention patent; however, the technical features of this invention patent are not limited thereto. It should be noted that, for those skilled in the art, various improvements and modifications can be made without departing from the principles and technical features of this invention, and all such changes, improvements, or modifications are covered within the protection scope of this invention patent.

Claims

1. A method for producing a molded porous carbon, characterized by, The steps are as follows: (1) the hydroxyl-containing aromatic compound and the amine-containing compound are sequentially added into an alcohol-water mixed solvent, wherein the molar ratio of the hydroxyl-containing aromatic compound to the amine-containing compound is 1:10-10:1; the volume ratio of alcohol to water is 1:1000-1000:1; (2) wood is used as a base frame material and is added into the solution obtained in step (1) to absorb the solution by standing; (3) Place the material obtained in step (2) into a sealed container containing aldehyde compounds, and heat the sealed container to 20-90°C. o C, and keep for 0.5-96 hours, then cool and remove the composite material; the molar ratio of aldehyde compounds to hydroxyl-containing aromatic compounds is 2:1-10:1; (4) placing the composite material obtained in step (3) in a carbonization furnace, and carbonizing under an inert gas atmosphere to obtain a shaped porous carbon; the carbonization conditions are a heating rate of 0.5-50 o C / min, rising to 500-1400 o C, and constant temperature for 10-240 min; The hydroxyl-containing aromatic compound is selected from one or more than two combinations of phenol, m-dihydroxybenzene, m-trihydroxybenzene, 2,3-dimethylphenol and bisphenol A; The amine-containing compound is one or more than two combinations of aniline, p-phenylenediamine, diphenyl diamine, ethylenediamine, 1,6-hexanediamine, cyclohexanediamine, p-aminobenzoic acid, melamine and amino acid; The aldehyde compound is formaldehyde.

2. The method of claim 1, wherein the method further comprises, The alcohol-water mixed solvent is one of a mixed solvent of ethanol and water, a mixed solvent of methanol and water and a mixed solvent of ethylene glycol and water.

3. The preparation method according to claim 1, characterized in that, The base frame material is one or more than two combinations of pine wood, cypress wood, teak wood, fir wood, camphor wood, willow wood, basswood and bamboo wood.

4. The preparation method according to claim 1, characterized in that, The inert atmosphere is argon or nitrogen.

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