Preparation method of natural polymer conductive aerogel

Abstract

The invention discloses a preparation method of natural polymer conductive aerogel, and relates to the technical field of conductive aerogel. When the natural polymer conductive aerogel is prepared, firstly, modified nanocellulose is prepared into wet gel, then the wet gel and ammonium bicarbonate are subjected to freeze drying together to prepare aerogel, and finally in the atmosphere of mixed gas of nitrogen and hydrogen, a carbonization process is performed to prepare the natural polymer conductive aerogel. The modified nano cellulose wet gel is formed by wrapping microcrystalline cellulose with an alpha, omega-dihydroxy dimethyl siloxane oligomer long chain and has a three-dimensional network structure; the natural polymer conductive aerogel prepared by the invention not only has good toughness, but also has relatively strong adsorption capacity.

Description

Technical Field

[0001] The invention relates to the technical field of conductive aerogels, in particular to a method for preparing natural polymer conductive aerogels. Background Art

[0002] Carbon aerogel is a new type of porous carbon material. It is a nanoscale porous amorphous material discovered by Pekala et al. in 1989. It is obtained by high-temperature carbonization of aerogel. After high-temperature carbonization of low-density, low-thermal conductivity and network-structured organic aerogel, the obtained aerogel not only maintains the porous network structure of the organic aerogel, but also gives it excellent conductive properties.

[0003] CN201610605988 discloses a modified chitosan / nanocellulose composite aerogel and a preparation method and application thereof. Chitosan is first subjected to sulfur-modification to obtain the modified chitosan, which is then compounded with nanocellulose to prepare a sulfur-containing modified chitosan / nanocellulose composite porous aerogel. Although the adsorption effect is good, the obtained product does not have conductivity and has poor toughness.

[0004] The conductive aerogel obtained by carbonizing natural polymer aerogel has a high porosity, but the pores are often large. Even if electrostatic adsorption is used, the adsorption effect of natural polymer aerogel cannot be fully developed. In order to improve the adsorption efficiency, this application studies and prepares a natural polymer conductive aerogel with high toughness and strong adsorption capacity. Summary of the invention

[0005] The object of the present invention is to provide a natural polymer conductive aerogel and a preparation method thereof to solve the problems raised in the above background technology.

[0006] A method for preparing a natural polymer conductive aerogel, the method comprising: preparing a modified nanocellulose wet gel, preparing an aerogel, and preparing a natural polymer conductive aerogel in sequence; the method is characterized in that the preparation of the modified nanocellulose wet gel comprises placing pretreated microcrystalline cellulose in an ionic liquid containing 2, 2, 6, 6-tetramethylpiperidinyl oxide, and then adding α, ω-dihydroxydimethylsiloxane oligomer to react to obtain the modified nanocellulose wet gel.

[0007] Preferably, the aerogel preparation process comprises adding an ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, sealing, heating to 40-50° C., reacting, and performing freeze drying and low-temperature vacuum drying to obtain the aerogel.

[0008] Preferably, the preparation of the natural polymer conductive aerogel includes: placing the aerogel in a tubular furnace, replacing the air in the furnace with a mixture of hydrogen and nitrogen, and sintering at a high temperature to obtain the natural polymer conductive aerogel.

[0009] Preferably, a method for preparing a natural polymer conductive aerogel comprises the following specific steps: (1) placing the pretreated microcrystalline cellulose in an ionic liquid with a mass of 20 to 30 times that of the microcrystalline cellulose, stirring evenly until dissolved, adding α, ω-dihydroxydimethylsiloxane oligomer with a mass of 0.3 to 0.5 times that of the microcrystalline cellulose, stirring at room temperature and 150 to 300 rpm for 24 to 28 hours, to obtain a modified nanocellulose wet gel; (2) adding 0.15 to 0.3 times the mass of the modified nanocellulose wet gel and a 10 to 25% ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, and sealing the mixture, heating the mixture to 40 to 50° C., reacting the mixture for 30 to 50 minutes, and then transferring the mixture to a freeze dryer, and immediately performing freeze drying and low-temperature vacuum drying to obtain an aerogel; (3) The aerogel is placed in a tubular furnace and the air in the furnace is replaced by a mixture of hydrogen and nitrogen with a mass ratio of nitrogen to hydrogen of 0.5:1 to 1:1. The temperature is raised to 800 to 1000°C at a rate of 4 to 5°C / min, kept at this temperature for 2 to 3 hours, and cooled to room temperature to obtain a natural polymer conductive aerogel.

[0010] Preferably, in the above step (1), the process of pretreating the microcrystalline cellulose is as follows: dispersing the microcrystalline cellulose in a 3-5% formic acid solution having a mass fraction of 50-60 times the mass of the microcrystalline cellulose, ultrasonicating at 20° C. and 50-60 kHz for 3-5 hours, adding distilled water having a mass fraction of 100-200 times the mass of the microcrystalline cellulose, and rapidly filtering with filter paper under vacuum conditions to obtain the pretreated microcrystalline cellulose.

[0011] Preferably, in the above step (1): in the ionic liquid, the mass ratio of the imidazole ionic liquid to 2, 2, 6, 6-tetramethylpiperidinyl oxide is 10:0.05 to 10:0.15.

[0012] Preferably, in the above step (1): the preparation method of α, ω-dihydroxydimethylsiloxane oligomer is as follows: octamethylcyclotetrasiloxane, acetic anhydride and aluminum oxide are mixed in a mass ratio of 5:1:0.08 to 5:1.5:0.1 in a three-necked flask, heated to 120°C and refluxed for reaction for 8 to 10 hours, cooled to 50°C and then filtered, the filtrate is washed 3 to 5 times with a mixture of sodium chloride and ammonium bicarbonate with a mass fraction of 10%, the filtrate is placed in a three-necked flask after washing, deionized water of 2 to 3 times the mass of octamethylcyclotetrasiloxane is added, the mixture is reacted at 70°C for 3 to 4 hours, cooled to room temperature, washed with deionized water for 3 to 5 times, separated and distilled under reduced pressure to obtain α, ω-dihydroxydimethylsiloxane oligomer.

[0013] Preferably, in the above step (2), the process of treating the modified nanocellulose wet gel with acetone is as follows: immersing the modified nanocellulose wet gel in acetone, replacing the acetone once every 24 hours, and replacing it three times to obtain the modified nanocellulose wet gel treated with acetone.

[0014] Preferably, in the above step (2): during freeze drying, the freezing temperature is -48 to -52°C, the freezing time is 12 to 15 hours, and during low-temperature vacuum drying, the pressure is 1 Pa, and the drying time is 48 hours.

[0015] Preferably, the natural polymer conductive aerogel prepared by the preparation method of the natural polymer conductive aerogel comprises the following raw materials in weight fractions: 20 to 30 parts of modified nanocellulose wet gel and 3 to 9 parts of ammonium bicarbonate solution; the modified nanocellulose wet gel dissolves microcrystalline cellulose in an ionic liquid containing 2, 2, 6, 6-tetramethylpiperidinyl oxide, and after dissolution, α, ω-dihydroxydimethylsiloxane oligomer is added; the ionic liquid is an imidazole ionic liquid containing 2, 2, 6, 6-tetramethylpiperidinyl oxide; the mass fraction of the ammonium bicarbonate solution is 10 to 25%.

[0016] Preferably, the modified nanocellulose wet gel dissolves microcrystalline cellulose in an ionic liquid containing 2, 2, 6, 6-tetramethylpiperidinyl oxide, and after dissolution, α, ω-dihydroxydimethylsiloxane oligomer is added; the ionic liquid is an imidazole ionic liquid containing 2, 2, 6, 6-tetramethylpiperidinyl oxide; and the mass fraction of the ammonium bicarbonate solution is 10 to 25%.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: When preparing the natural polymer conductive aerogel, the present invention first prepares the modified nanocellulose into a wet gel, then dries it into an aerogel, and finally performs a carbonization process to prepare the natural polymer conductive aerogel. The microcrystalline cellulose is dissolved in an ionic liquid containing 2, 2, 6, 6-tetramethylpiperidinyl oxide, and after the dissolution, α, ω-dihydroxydimethylsiloxane oligomer is added to modify the nanocellulose wet gel; 2, 2, 6, 6-tetramethylpiperidinyl oxide oxidizes the hydroxyl groups on the surface of the nanocellulose into carboxyl groups, thereby improving the dissolution of the crystalline region of the microcrystalline cellulose, and at the same time, under the catalysis of 2, 2, 6, 6-tetramethylpiperidinyl oxide, the remaining hydroxyl groups and the generated carboxyl groups of the microcrystalline cellulose are cross-linked with the α, ω-dihydroxydimethylsiloxane oligomer to form a modified nanocellulose wet gel with a long chain wrapping and a three-dimensional network structure, thereby increasing the strength of the modified nanocellulose wet gel and thus enhancing the toughness of the conductive aerogel; During drying, ammonium bicarbonate is added to the modified nanocellulose wet gel, which is first sealed and heated and then freeze-dried; during heating, the ammonium bicarbonate decomposes to generate ammonia, water and carbon dioxide, and the gas is sealed so that it remains inside the modified nanocellulose wet gel. At the same time, the ammonia reacts with the hydroxyl group and the carboxyl group to aminize the modified nanocellulose wet gel and form a bridge inside the wet gel. After freeze-drying, the aerogel expands and contracts due to heat, so that the pores inside the aerogel are first dispersed by the bridges and then shrink, the pores become smaller, the porosity increases, and the adsorption capacity is enhanced; during the final carbonization process, nitrogen and hydrogen are used as protective gases, which, on the one hand, replenish ammonia for the aerogel to continue the reaction, and on the other hand, adsorb and remove the generated carbon dioxide from the aerogel to prevent the carbon dioxide generated during drying from affecting the adsorption of the conductive aerogel. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the natural polymer conductive aerogels prepared in the examples and comparative examples as follows: Toughness: The elastic modulus of the natural polymer conductive aerogels prepared in the examples and comparative examples was tested using a static method; Adsorption: The natural polymer conductive aerogels prepared in the examples and comparative examples were tested for specific surface area, area and pore size using an adsorption instrument.

[0020] Example 1 A natural polymer conductive aerogel, measured by weight, mainly comprising: 20 parts of modified nanocellulose wet gel, 3 parts of ammonium bicarbonate solution.

[0021] A method for preparing a natural polymer conductive aerogel, the method for preparing the natural polymer conductive aerogel comprising: (1) Disperse microcrystalline cellulose in a 5% formic acid solution with a mass fraction of 50 times that of the microcrystalline cellulose, ultrasonicate at 20°C and 50kHz for 3h, add distilled water with a mass fraction of 100 times that of the microcrystalline cellulose, and quickly filter with filter paper under vacuum to obtain pretreated microcrystalline cellulose; mix 1,2,4-triazole ionic liquid with 2, 2, 6, 6-tetramethylpiperidinyl oxide was mixed in a mass ratio of 10:0.05 to obtain an ionic liquid; octamethylcyclotetrasiloxane, acetic anhydride and aluminum oxide were mixed in a mass ratio of 5:1:0.08 and placed in a three-necked flask, heated to 120°C and refluxed for reaction for 8 hours, cooled to 50°C and filtered, the filtrate was washed 3 times with a mixture of sodium chloride and sodium bicarbonate with a mass fraction of 10%, placed in a three-necked flask after washing, deionized water twice the mass of octamethylcyclotetrasiloxane was added, reacted at 70°C for 3 hours, cooled to room temperature, washed 3 times with deionized water, separated and distilled under reduced pressure to obtain α, ω-dihydroxydimethylsiloxane oligomer; pretreated microcrystalline cellulose was placed in an ionic liquid 20 times the mass of microcrystalline cellulose, stirred evenly until dissolved, α, ω-dihydroxydimethylsiloxane oligomer 0.3 times the mass of microcrystalline cellulose was added, stirred at room temperature and 150rpm for 28 hours to obtain a modified nanocellulose wet gel; (2) Immersing the modified nanocellulose wet gel in acetone, replacing the acetone every 24 hours, and replacing it three times to obtain the modified nanocellulose wet gel treated with acetone; adding 0.15 times the mass of the modified nanocellulose wet gel and a 10% ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, and sealing it, heating it to 40°C, reacting it for 30 minutes, and then transferring it to a freeze dryer, and immediately freeze drying and low-temperature vacuum drying treatment, during freeze drying, the freezing temperature is -48°C, the freezing time is 12 hours, and during low-temperature vacuum drying treatment, the pressure is 1Pa, and the drying time is 48 hours, to obtain an aerogel; (3) Nitrogen and hydrogen are mixed in a mass ratio of 0.5:1 to prepare a mixed gas; the aerogel is placed in a tubular furnace, and the air in the furnace is replaced by the mixed gas, the temperature is increased to 800-1000°C at 4°C / min, the temperature is kept for 2 hours, and the mixture is cooled to room temperature to prepare a natural polymer conductive aerogel.

[0022] Example 2 A natural polymer conductive aerogel, measured by weight, mainly comprising: 25 parts of modified nanocellulose wet gel, 5 parts of ammonium bicarbonate solution.

[0023] A method for preparing a natural polymer conductive aerogel, the method for preparing the natural polymer conductive aerogel comprising: (1) Disperse microcrystalline cellulose in a 4% formic acid solution with a mass fraction of 55 times that of microcrystalline cellulose, ultrasonicate at 20°C and 55kHz for 4h, add distilled water with a mass fraction of 150 times that of microcrystalline cellulose, and quickly filter with filter paper under vacuum to obtain pretreated microcrystalline cellulose; mix 1,2,4-triazole ionic liquid with 2, 2, 6, 6-tetramethylpiperidinyl oxide was mixed in a mass ratio of 10:0.1 to obtain an ionic liquid; octamethylcyclotetrasiloxane, acetic anhydride and aluminum oxide were mixed in a mass ratio of 5:1:0.09 and placed in a three-necked flask, heated to 120°C and refluxed for reaction for 9 hours, cooled to 50°C and filtered, the filtrate was washed 4 times with a mixture of sodium chloride and sodium bicarbonate with a mass fraction of 10%, placed in a three-necked flask after washing, deionized water 3 times the mass of octamethylcyclotetrasiloxane was added, reacted at 70°C for 4 hours, cooled to room temperature, washed 4 times with deionized water, separated and distilled under reduced pressure to obtain α, ω-dihydroxydimethylsiloxane oligomer; pretreated microcrystalline cellulose was placed in an ionic liquid 25 times the mass of microcrystalline cellulose, stirred evenly until dissolved, α, ω-dihydroxydimethylsiloxane oligomer 0.4 times the mass of microcrystalline cellulose was added, stirred at room temperature and 200rpm for 26 hours to obtain a modified nanocellulose wet gel; (2) Immersing the modified nanocellulose wet gel in acetone, replacing the acetone every 24 hours, and replacing it three times to obtain the modified nanocellulose wet gel treated with acetone; adding 0.2 times the mass of the modified nanocellulose wet gel and a 15% ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, and sealing it, heating it to 45°C, reacting it for 40 minutes, and then transferring it to a freeze dryer, and immediately freeze drying and low-temperature vacuum drying treatment, during freeze drying, the freezing temperature is -50°C, the freezing time is 14 hours, and during low-temperature vacuum drying treatment, the pressure is 1Pa, and the drying time is 48 hours, to obtain an aerogel; (3) Nitrogen and hydrogen are mixed in a mass ratio of 0.8:1 to prepare a mixed gas; the aerogel is placed in a tubular furnace, and the air in the furnace is replaced by the mixed gas, the temperature is raised to 9000°C at a rate of 4.5°C / min, the temperature is kept at this temperature for 2.5 h, and the aerogel is cooled to room temperature to prepare a natural polymer conductive aerogel.

[0024] Example 3 A natural polymer conductive aerogel, measured by weight, mainly comprising: 30 parts of modified nanocellulose wet gel, 6 parts of ammonium bicarbonate solution.

[0025] A method for preparing a natural polymer conductive aerogel, the method for preparing the natural polymer conductive aerogel comprising: (1) Disperse microcrystalline cellulose in a 5% formic acid solution with a mass fraction of 60 times that of the microcrystalline cellulose, ultrasonicate at 20°C and 60kHz for 5 h, add distilled water with a mass fraction of 200 times that of the microcrystalline cellulose, and quickly filter with filter paper under vacuum to obtain pretreated microcrystalline cellulose; mix 1,3-dimethyl-3-imidazole hexafluorophosphate ionic liquid with 2, 2, 6, 6-tetramethylpiperidinyl oxide was mixed in a mass ratio of 10:0.15 to obtain an ionic liquid; octamethylcyclotetrasiloxane, acetic anhydride and aluminum oxide were mixed in a mass ratio of 5:1.5:0.1 and placed in a three-necked flask, heated to 120°C and refluxed for reaction for 10 hours, cooled to 50°C and filtered, the filtrate was washed 5 times with a mixture of sodium chloride and sodium bicarbonate with a mass fraction of 10%, placed in a three-necked flask after washing, deionized water 3 times the mass of octamethylcyclotetrasiloxane was added, reacted at 70°C for 4 hours, cooled to room temperature, washed 5 times with deionized water, separated and distilled under reduced pressure to obtain α, ω-dihydroxydimethylsiloxane oligomer; pretreated microcrystalline cellulose was placed in an ionic liquid 30 times the mass of microcrystalline cellulose, stirred evenly until dissolved, α, ω-dihydroxydimethylsiloxane oligomer 0.5 times the mass of microcrystalline cellulose was added, stirred at room temperature and 300 rpm for 24 hours to obtain a modified nanocellulose wet gel; (2) Immersing the modified nanocellulose wet gel in acetone, replacing the acetone every 24 hours, and replacing it three times to obtain the modified nanocellulose wet gel treated with acetone; adding 0.3 times the mass of the modified nanocellulose wet gel and a 25% ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, and sealing it, heating it to 50°C, reacting it for 50 minutes, and then transferring it to a freeze dryer, and immediately freeze drying and low-temperature vacuum drying treatment, during freeze drying, the freezing temperature is -52°C, the freezing time is 15 hours, and during low-temperature vacuum drying treatment, the pressure is 1Pa, and the drying time is 48 hours, to obtain an aerogel; (3) Nitrogen and hydrogen are mixed in a mass ratio of 1:1 to prepare a mixed gas; the aerogel is placed in a tubular furnace, and the air in the furnace is replaced by the mixed gas, the temperature is increased to 1000°C at a rate of 5°C / min, the temperature is kept for 3 hours, and the mixture is cooled to room temperature to obtain a natural polymer conductive aerogel.

[0026] Comparative Example 1 The prescription composition of comparative example 1 is the same as that of example 2. The natural polymer conductive aerogel and its preparation method differ from example 2 only in step (1), which is modified as follows: disperse microcrystalline cellulose in a 4% formic acid solution with a mass fraction of 55 times the mass of microcrystalline cellulose, ultrasonicate at 20°C and 55kHz for 4 hours, add distilled water with a mass fraction of 150 times the mass of microcrystalline cellulose, and quickly filter with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; mix imidazole ionic liquid and 2,2,6,6-tetramethylpiperidinyl oxide in a mass ratio of 10:0.1 to obtain ionic liquid; place the pretreated microcrystalline cellulose in an ionic liquid with a mass fraction of 25 times the mass of microcrystalline cellulose, stir evenly until dissolved, and stir at room temperature and 200rpm for 26 hours to obtain a modified nanocellulose wet gel. The remaining steps are the same as example 2.

[0027] Comparative Example 2 The formula composition of comparative example 2 is the same as that of example 2. The natural polymer conductive aerogel and its preparation method differ from example 2 only in step (1), which is modified as follows: disperse microcrystalline cellulose in a 4% formic acid solution with a mass fraction of 55 times the mass of microcrystalline cellulose, ultrasonicate at 20°C and 55kHz for 4h, add distilled water with a mass fraction of 150 times the mass of microcrystalline cellulose, and quickly filter with filter paper under vacuum conditions to obtain pretreated microcrystalline cellulose; mix octamethylcyclotetrasiloxane, acetic anhydride and alumina in a mass ratio of 5:1:0.09 in a three-necked flask, heat to 120°C and reflux for 9h, cool to 50°C and filter, and separate the filtrate with water. The mixture of sodium chloride and sodium bicarbonate with a mass fraction of 10% was washed 4 times, and after washing, it was placed in a three-necked flask, and deionized water with a mass of 3 times that of octamethylcyclotetrasiloxane was added, and the mixture was reacted at 70°C for 4 hours, cooled to room temperature, washed 4 times with deionized water, separated and distilled under reduced pressure to obtain α, ω-dihydroxydimethylsiloxane oligomers; the pretreated microcrystalline cellulose was placed in an ionic liquid with a mass of 25 times that of the microcrystalline cellulose, stirred evenly until dissolved, and α, ω-dihydroxydimethylsiloxane oligomers with a mass of 0.4 times that of the microcrystalline cellulose were added, and stirred at room temperature and 200 rpm for 26 hours to obtain a modified nanocellulose wet gel. The remaining steps are the same as in Example 2.

[0028] Comparative Example 3 The formula composition of Comparative Example 3 is the same as that of Example 2. The natural polymer conductive aerogel and its preparation method are different from those of Example 2 only in step (2), which is modified as follows: immersing the modified nanocellulose wet gel in acetone, replacing the acetone once every 24 hours, and replacing it three times to obtain the modified nanocellulose wet gel treated with acetone; sealing the modified nanocellulose wet gel treated with acetone, heating it to 45°C, reacting it for 40 minutes, and then transferring it to a freeze dryer, and immediately freeze drying and low-temperature vacuum drying are performed. During freeze drying, the freezing temperature is -50°C and the freezing time is 14 hours. During low-temperature vacuum drying, the pressure is 1Pa and the drying time is 48 hours to obtain the aerogel. The remaining steps are the same as those of Example 2.

[0029] Comparative Example 4 The formulation composition of Comparative Example 4 is the same as that of Example 2. The natural polymer conductive aerogel and its preparation method are different from those of Example 2 only in step (3), which is modified as follows: placing the aerogel in a tubular furnace, replacing the air in the furnace with nitrogen, heating the aerogel to 800-1000° C. at 4-5° C. / min, keeping the temperature for 2-3 hours, and cooling to room temperature to obtain the natural polymer conductive aerogel. The remaining steps are the same as those of Example 2.

[0030] Comparative Example 5 Comparative Example 5 is the sulfur-modified chitosan aerogel prepared in Example 1 of CN201610605988. Table 1 below shows the performance analysis results of rubber materials prepared using the natural polymer conductive aerogels of Examples 1 and 2 of the present invention and Comparative Examples 1, 2, 3, and 4.

[0031] Table 1 <![CDATA[Impact toughness (kJ / m 2 )]]> <![CDATA[Specific surface area (m 2 / g)]]> Average pore size (nm) Example 1 6.0 372 5.08 Example 2 6.1 365 5.13 Example 3 5.9 369 5.02 Comparative Example 1 4.2 310 6.52 Comparative Example 2 4.9 327 6.34 Comparative Example 3 5.8 361 7.10 Comparative Example 4 5.7 319 6.49 Comparative Example 5 4.3 360 5.16 By comparing the experimental data of the examples and the comparative examples in Table 1, it can be clearly found that the natural polymer conductive aerogels prepared in Examples 1 and 2 have good impact toughness, large specific surface area and small average pore size, indicating excellent toughness and adsorption; From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Examples 1 and 2, it can be found that when the natural polymer conductive aerogel is prepared, α, ω-dihydroxydimethylsiloxane oligomer is added, and under the catalysis of 2, 2, 6, 6-tetramethylpiperidinyl oxide, the remaining hydroxyl groups and the generated carboxyl groups of the microcrystalline cellulose are cross-linked with the α, ω-dihydroxydimethylsiloxane oligomer to form a modified nanocellulose wet gel wrapped in a long chain and having a three-dimensional network structure, thereby increasing the strength of the modified nanocellulose wet gel, thereby enhancing the toughness of the conductive aerogel, while the use of only α, ω-dihydroxydimethylsiloxane oligomers cannot enhance the toughness of the conductive aerogel; From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Example 3, it can be found that during freeze-drying, ammonium bicarbonate is added to the modified nanocellulose wet gel to amino the modified nanocellulose wet gel, forming bridges inside the wet gel, dividing the aerogel with larger pores, reducing the air gap, increasing the specific surface area of ​​the conductive aerogel, and enhancing the adsorption capacity. When ammonium bicarbonate is not added, the average pore size of the conductive aerogel obtained is larger and the adsorption capacity is weaker.

[0032] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Example 4, it can be found that hydrogen is omitted during the sintering process, and only nitrogen is used as the protective gas, so that the average pore size of the aerogel is larger and the specific surface area is smaller, which means that the protective gas can not only supplement the ammonia to continue the reaction, but also reduce the effect of the carbon dioxide generated during drying on the adsorption of the aerogel.

[0033] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Example 5, it can be found that chitosan is first subjected to sulfur-containing modification to obtain modified chitosan, and then compounded with nanocellulose to prepare sulfur-containing modified chitosan / nanocellulose composite porous aerogel, which has a small average pore size and a large specific surface area, but α, ω-dihydroxydimethylsiloxane oligomers and 2, 2, 6, 6-tetramethylpiperidinyl oxide are not used, resulting in poor toughness, indicating that under the catalysis of 2, 2, 6, 6-tetramethylpiperidinyl oxide, α, ω-dihydroxydimethylsiloxane oligomers can react with microcrystalline cellulose to form a three-dimensional network structure with strong toughness.

[0034] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a natural polymer conductive aerogel, characterized in that: The preparation method of the natural polymer conductive aerogel is: (1) Disperse microcrystalline cellulose in a 4% formic acid solution with a mass fraction of 55 times that of microcrystalline cellulose, ultrasonicate at 20°C and 55kHz for 4h, add distilled water with a mass fraction of 150 times that of microcrystalline cellulose, and quickly filter with filter paper under vacuum to obtain pretreated microcrystalline cellulose; mix 1,2,4-triazole ionic liquid with 2, 2, 6, 6-tetramethylpiperidinyl oxide was mixed in a mass ratio of 10:0.1 to obtain an ionic liquid; octamethylcyclotetrasiloxane, acetic anhydride and aluminum oxide were mixed in a mass ratio of 5:1:0.09 and placed in a three-necked flask, heated to 120°C and refluxed for reaction for 9 hours, cooled to 50°C and filtered, the filtrate was washed 4 times with a mixture of sodium chloride and sodium bicarbonate with a mass fraction of 10%, placed in a three-necked flask after washing, deionized water 3 times the mass of octamethylcyclotetrasiloxane was added, reacted at 70°C for 4 hours, cooled to room temperature, washed 4 times with deionized water, separated and distilled under reduced pressure to obtain α, ω-dihydroxydimethylsiloxane oligomer; pretreated microcrystalline cellulose was placed in an ionic liquid 25 times the mass of microcrystalline cellulose, stirred evenly until dissolved, α, ω-dihydroxydimethylsiloxane oligomer 0.4 times the mass of microcrystalline cellulose was added, stirred at room temperature and 200rpm for 26 hours to obtain a modified nanocellulose wet gel; (2) Immersing the modified nanocellulose wet gel in acetone, replacing the acetone every 24 hours, and replacing it three times to obtain the modified nanocellulose wet gel treated with acetone; adding 0.2 times the mass of the modified nanocellulose wet gel and a 15% ammonium bicarbonate solution to the modified nanocellulose wet gel treated with acetone, and sealing it, heating it to 45°C, reacting it for 40 minutes, and then transferring it to a freeze dryer, and immediately freeze drying and low-temperature vacuum drying treatment, during freeze drying, the freezing temperature is -50°C, the freezing time is 14 hours, and during low-temperature vacuum drying treatment, the pressure is 1Pa, and the drying time is 48 hours, to obtain an aerogel; (3) Nitrogen and hydrogen are mixed in a mass ratio of 0.8:1 to prepare a mixed gas; the aerogel is placed in a tubular furnace, and the air in the furnace is replaced by the mixed gas, the temperature is raised to 9000°C at a rate of 4.5°C / min, the temperature is kept at this temperature for 2.5 h, and the aerogel is cooled to room temperature to prepare a natural polymer conductive aerogel.