A method for preparing carbon aerogel and its product

Abstract

The present invention relates to a method for preparing carbon aerogel, comprising the following steps: S1, mixing prepared carboxylated carbon nanotubes with glucose, hexane hexol, and water, and reacting them under heating condition 1 to form a reaction system; S2, adding hydroxy silicon dioxide to the reaction system, and continuing the reaction under heating condition 2 to generate an intermediate product; S3, cooling the intermediate product, subjecting it to several freeze-thaw cycles, and then drying it at a low temperature to obtain the carbon aerogel. The method for preparing the carbon aerogel of the present invention has a simple synthesis process and non-harsh reaction conditions, making it suitable for large-scale industrial production. The synthesized carbon aerogel product has a highly branched, porous network structure that is conducive to improving adsorption performance; it also has a relatively stable structure that is not easily deformed; and the synthesized carbon aerogel product has a more significant adsorption capacity and adsorption rate than similar products.

Description

Technical Field

[0001] The present invention belongs to the field of carbon aerogels, and in particular relates to a preparation method and product of carbon aerogels. Background Art

[0002] Carbon aerogel is a lightweight, porous nanocarbon material with a continuous three-dimensional network structure. Its low density, high conductivity, and high specific surface area make it widely applicable in various fields. In particular, its porosity, typically exceeding 80%, and pore size less than 50nm, enable efficient adsorption, making it an ideal candidate for use as an adsorbent, carrier, or capacitor material.

[0003] Early synthesis methods used resorcinol and formaldehyde as raw materials, and the gel-sol method is currently one of the most common methods. The resulting carbon aerogels possess a three-dimensional network structure and have achieved breakthroughs in improving adsorption performance and structural stability. However, how to further increase the degree of branching and specific surface area to enhance adsorption while maintaining structural stability has also been a focus of attention.

[0004] Carbon aerogels are widely reported in the prior art, such as patents CN109225152A, CN109179372A, CN106120007A, and CN107200600A. These patents provide detailed reports on the preparation methods and structures of carbon aerogels, and the resulting products demonstrate excellent performance in oil-water separation and gas adsorption. However, these patents do not describe the porosity and specific surface area expansion of the three-dimensional network structure, nor do they consider how to balance material stability.

[0005] Therefore, the present invention designs a method for preparing carbon aerogel and related structures to solve the above problems. Summary of the Invention

[0006] An object of the present invention is to provide a method for preparing carbon aerogel, which comprises the following steps:

[0007] S1, mixing the prepared carboxylated carbon nanotubes with glucose, hexane hexacol and water, and reacting them under heating condition 1 to form a reaction system;

[0008] S2, adding hydroxy silicon dioxide to the reaction system, and continuing the reaction under heating condition 2 to generate an intermediate product;

[0009] S3. Cooling the intermediate product, subjecting it to several freeze-thaw cycles, and then drying it at low temperature to obtain the carbon aerogel.

[0010] The carbon nanotubes of the present invention contain a large number of carboxyl groups, which, under heating conditions, easily undergo a similar esterification reaction with the hydroxyl groups on glucose and hexadecene, thereby causing the latter to be grafted onto the carbon nanotubes to form a macromolecular cross-linked gel structure. The hydroxyl groups on glucose, hexadecene, and hydroxysilica have a high density and a large functionality, making it easier to form a high-density three-dimensional network structure. In addition, the high hydroxyl density is also conducive to the formation of intermolecular and intramolecular hydrogen bonds between unreacted hydroxyl groups, thereby greatly enhancing the interaction force between the various parts of the macromolecule and making the structure of the three-dimensional network molecule tend to be stable.

[0011] Furthermore, the mass ratio of the carboxylated carbon nanotubes, glucose and hexane is 2:1:0.1-3:1:0.03.

[0012] Furthermore, the heating condition 1 is: 80-90°C; the heating condition 2 is: 80-90°C.

[0013] Furthermore, the number of freeze-thaw cycles is 3-5 times.

[0014] Furthermore, the temperature of the low-temperature drying is -80 to -60°C.

[0015] Furthermore, the device for drying at low temperature is a freeze dryer.

[0016] Furthermore, the carboxylated carbon nanotubes are prepared according to the following steps:

[0017] The carbon nanotubes are placed in a container, a mixture of concentrated sulfuric acid and concentrated hydrochloric acid is added, and the carbon nanotubes are washed with water and ethanol after ultrasonic treatment, and dried to obtain the carboxylated carbon nanotubes.

[0018] Furthermore, the volume ratio of the concentrated sulfuric acid to the concentrated hydrochloric acid is 1:1-3:1.

[0019] Another object of the present invention is to provide carbon aerogel prepared by the above-mentioned method for preparing carbon aerogel.

[0020] The present invention has the following beneficial effects:

[0021] 1. The preparation method of the carbon aerogel of the present invention has a simple synthesis process, non-critical reaction conditions, and is suitable for large-scale industrial production;

[0022] 2. The synthesized carbon aerogel product has a highly branched, porous network structure, which is beneficial to improving adsorption performance; it also has a relatively stable structure and is not easy to deform;

[0023] 3. The adsorption capacity and adsorption rate of the synthesized carbon aerogel product are more significant than those of similar products. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the technical solutions of the present invention, the following examples are given. Unless otherwise stated, the raw materials, reactions and post-processing methods mentioned in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0025] The preparation method of carboxylated carbon nanotubes of the present invention is as follows: 20 g of commercially available carbon nanotubes are mixed with 1 L of concentrated sulfuric acid and 0.5 L of concentrated hydrochloric acid, placed in a container, and ultrasonically treated at 50°C (500 W) for 10 hours. The product is then washed with deionized water and then ethanol until neutral, dried at 60°C overnight, and then ground into fine particles to obtain carboxylated carbon nanotubes.

[0026] Example 1

[0027] A method for preparing carbon aerogel comprises the following steps:

[0028] S1. 2 g of the prepared carboxylated carbon nanotubes, 1 g of glucose, and 0.1 g of hexacol were mixed in 50 ml of deionized water, and stirred at 80° C. for 1 h to form a reaction system;

[0029] S2. Add 0.5 g of hydroxy silicon dioxide to the reaction system and continue stirring at 80° C. for 1 h to generate an intermediate product;

[0030] S3. Cool the intermediate product, freeze the sample in a -78°C refrigerator for 1 hour, then thaw at room temperature for 1 hour, and repeat this process three times; finally, place the sample in a freeze dryer and dry it at -78°C for 3 days to obtain the product.

[0031] Example 2

[0032] A method for preparing carbon aerogel comprises the following steps:

[0033] S1. 3 g of the prepared carboxylated carbon nanotubes, 1 g of glucose, and 0.3 g of hexacol were mixed in 60 ml of deionized water, and stirred at 90° C. for 1 h to form a reaction system;

[0034] S2. Add 0.8 g of hydroxy silicon dioxide to the reaction system and continue stirring at 90° C. for 1 h to generate an intermediate product;

[0035] S3. Cool the intermediate product, freeze the sample in a -78°C refrigerator for 1 hour, then thaw at room temperature for 1 hour, and repeat this process three times; finally, place the sample in a freeze dryer and dry it at -78°C for 3 days to obtain the product.

[0036] Example 3

[0037] A method for preparing carbon aerogel comprises the following steps:

[0038] S1. 2.5 g of the prepared carboxylated carbon nanotubes, 1.2 g of glucose, and 0.2 g of hexacol were mixed in 60 ml of deionized water, and stirred at 90° C. for 1 h to form a reaction system;

[0039] S2. Add 0.6 g of hydroxy silicon dioxide to the reaction system and continue stirring at 90° C. for 1 h to generate an intermediate product;

[0040] S3. Cool the intermediate product, place the sample in a refrigerator at -78°C for 2 hours, then thaw at room temperature for 2 hours, and repeat this process three times; finally, place the sample in a freeze dryer and dry it at -78°C for 3 days to obtain the product.

[0041] Example 4

[0042] A method for preparing carbon aerogel comprises the following steps:

[0043] S1. 2.7 g of the prepared carboxylated carbon nanotubes, 1.3 g of glucose, and 0.3 g of hexacol were mixed in 65 ml of deionized water, and stirred at 85° C. for 1 h to form a reaction system;

[0044] S2. Add 0.7 g of hydroxy silicon dioxide to the reaction system and continue stirring at 90° C. for 1 h to generate an intermediate product;

[0045] S3. Cool the intermediate product, place the sample in a refrigerator at -78°C for 2 hours, then thaw at room temperature for 2 hours, and repeat this process three times; finally, place the sample in a freeze dryer and dry it at -78°C for 3 days to obtain the product.

[0046] Comparative Example 1

[0047] The preparation method of the carbon aerogel of Comparative Example 1 is the same as that of Example 1, with the only difference being that in Comparative Example 1, hexane hexol is replaced with an equal mass of butanol.

[0048] Comparative Example 2

[0049] The preparation method of the carbon aerogel in Comparative Example 1 is the same as that in Example 1, with the only difference being that in Comparative Example 1, hexane hexol is replaced with polyethylene glycol of the same mass.

[0050] Comparative Example 3

[0051] The preparation method of the carbon aerogel in Comparative Example 1 is the same as that in Example 1, with the only difference being that in Comparative Example 1, glucose is replaced by polyethylene glycol of an equal mass.

[0052] Test Case

[0053] The carbon aerogels obtained in Example 1 and Comparative Examples 1-3 were subjected to an oil absorption test.

[0054] The test method is as follows: the following parallel experiments were performed: 50 ml beakers were added with an organic solvent, petroleum ether, and then carbon aerogel samples of the same size obtained in Example 1 and Comparative Examples 1-3 were added to each beaker separately. The carbon aerogels were immersed in the solvent for static adsorption. After these samples were taken out, the adsorption amount was weighed. The results are shown in Table 1.

[0055] Table 1 Adsorption capacity of petroleum ether by carbon aerogels obtained in Example 1 and Comparative Examples 1-3 (g / g)

[0056] sample Adsorption capacity Example 1 69.5 Comparative Example 1 62.3 Comparative Example 2 61.2 Comparative Example 3 59.7

[0057] As can be seen from Table 1, the adsorption amount of the oil phase in Example 1 is much higher than that in Comparative Examples 1-3. This is because the branching degree and specific surface area of ​​the carbon aerogel in Example 1 are larger than those in the comparative examples, and the three-dimensional network structure is more fully formed, which is very conducive to the improvement of the adsorption amount.

[0058] The mechanical properties of the carbon aerogels obtained in Example 1 and Comparative Examples 1-3 were tested.

[0059] The test method is as follows: cut the sample to a size of 20.0cm*20.0cm*5.0cm, then apply mechanical force to its surface, compress it to 1 / 4 of the original thickness, and let the mechanical force stand for 1 hour.

[0060] The mechanical force was then slowly removed, and the sample was allowed to stand for 10 minutes before the thickness change was measured. The results are shown in Table 2.

[0061] Table 2 Deformation degree of carbon aerogel obtained in Example 1 and Comparative Examples 1-3 (%)

[0062] sample Deformation degree Example 1 Less than 5% Comparative Example 1 ～10％ Comparative Example 2 ～10％ Comparative Example 3 ～10％

[0063] As can be seen from Table 2, the carbon aerogel skeleton formed in Example 1 is more stable and is not prone to permanent deformation during the long-term application of static mechanical force.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0065] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing carbon aerogel, characterized in that: The preparation method of the carbon aerogel comprises the following steps: S1, mixing the prepared carboxylated carbon nanotubes with glucose, hexane hexacol and water, and reacting them under heating condition 1 to form a reaction system; S2, adding hydroxy silicon dioxide to the reaction system, and continuing the reaction under heating condition 2 to generate an intermediate product; S3, cooling the intermediate product, subjecting it to several freeze-thaw cycles, and then drying it at low temperature to obtain the carbon aerogel, Wherein, the mass ratio of the carboxylated carbon nanotubes, glucose and hexane is 2:1:0.1-3:1:0.03, Wherein, the heating condition 1 is: 80-90°C; the heating condition 2 is: 80-90°C, Wherein, the carboxylated carbon nanotubes are prepared according to the following steps: The carbon nanotubes are placed in a container, a mixture of concentrated sulfuric acid and concentrated hydrochloric acid is added, and the carbon nanotubes are washed with water and ethanol after ultrasonic treatment, and dried to obtain the carboxylated carbon nanotubes. Wherein, the volume ratio of the concentrated sulfuric acid to the concentrated hydrochloric acid is 1:1-3:

1.

2. The method for preparing carbon aerogel according to claim 1, characterized in that: The number of freeze-thaw cycles is 3-5 times.

3. The method for preparing carbon aerogel according to claim 1, characterized in that: The temperature of the low temperature drying is -80 to -60°C.

4. The method for preparing carbon aerogel according to claim 1, wherein: The device for drying at low temperature is a freeze dryer.

5. A carbon aerogel prepared by the method for preparing a carbon aerogel according to any one of claims 1 to 4.