Alumina aerogel and method for preparing the same

Abstract

The application relates to an alumina aerogel and a preparation method thereof, the method comprising the following steps: first mixing and stirring industrial aluminum-containing raw materials, a first solvent and an additive, and then performing chemical reaction to obtain a first slurry; reprocessing the first slurry to obtain a wet solid; adding a second solvent to the wet solid and performing second mixing and stirring to obtain a second slurry; adding an adjusting agent to the second slurry and then performing pH regulation to obtain a third slurry; sealing the third slurry to obtain a gel; drying the gel and then calcining to obtain the alumina aerogel. The alumina aerogel prepared by the method has excellent performance, the method is low in cost, simple and controllable in the preparation process and high in added value, and thus realizes industrialized production of the alumina aerogel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alumina aerogel preparation, and in particular to an alumina aerogel and a preparation method thereof. BACKGROUND

[0002] The Al2O3 aerogel not only has various properties of general aerogels, but also has a higher use temperature due to its special microstructure, and the use temperature can reach 1000℃. Therefore, the Al2O3 aerogel can be used in the fields of high-temperature insulation, catalysts and carriers, etc. At present, the preparation of the alumina aerogel generally uses inorganic aluminum salt and aluminum alkoxide as raw materials, and uses a sol-gel method and a special drying technology for synthesis.

[0003] However, the preparation process using aluminum alkoxide as raw material is relatively complex, the hydrolysis rate is fast and difficult to control, there are many influencing factors, and the types and concentrations of solvents, reaction temperature, etc. will have a great influence. Moreover, the raw material is expensive, which is not conducive to the industrial production of aerogel products. The alumina gel prepared by the inorganic aluminum salt method generally has large particles, large shrinkage of the aerogel, poor bulk performance and easy pulverization. Therefore, the Al2O3 aerogels prepared by the two methods are difficult to realize industrial production. SUMMARY

[0004] The present application provides an alumina aerogel and a preparation method thereof, to solve the technical problem that the existing alumina aerogel is difficult to realize industrial production.

[0005] In a first aspect, the present application provides a preparation method of an alumina aerogel, and the method comprises:

[0006] mixing and stirring an industrial aluminum-containing raw material, a first solvent and an additive to obtain a first slurry;

[0007] reprocessing the first slurry to obtain a wet solid;

[0008] adding a second solvent to the wet solid and mixing and stirring to obtain a second slurry;

[0009] adding an adjusting agent to the second slurry and then controlling the pH to obtain a third slurry;

[0010] sealing the third slurry to obtain a gel;

[0011] drying the gel and then calcining to obtain an alumina aerogel.

[0012] Optionally, the industrial aluminum-containing raw material comprises one of the following: aluminum hydroxide, hydrous aluminum oxide, a derivative after treatment of aluminum hydroxide, and a derivative after treatment of hydrous aluminum oxide.

[0013] Optionally, the second solvent comprises an alcohol solvent, an amine solvent, and an alkane solvent.

[0014] Optionally, the pH of the adjusting agent is 7-10.

[0015] Optionally, the component of the adjusting agent comprises a third solvent and a pH adjusting agent.

[0016] Optionally, the third solvent comprises one of the following: ethanol, methanol, propanol, acetone; and / or,

[0017] The pH adjusting agent comprises one of the following: ammonium carbonate, ammonium bicarbonate, methylamine, ethylamine, diethylamine, diisopropyl ethylamine, ammonia.

[0018] Optionally, the pH of the third slurry is 3-8.

[0019] Optionally, the solute is 0.01-0.5 parts by weight relative to 1 part by weight of the second slurry.

[0020] Optionally, the process parameters of the second mixing and stirring comprise: a stirring temperature of 15-40 DEG C, and a stirring speed of 500-2000 r / min.

[0021] In a second aspect, the application provides an alumina aerogel, which is prepared by the method of any one of the embodiments of the first aspect.

[0022] Compared with the prior art, the above technical solution provided in the embodiments of the application has the following advantages:

[0023] The preparation method of the alumina aerogel provided in the embodiments of the application uses industrial aluminum-containing raw materials as main raw materials, has low cost, and has a unique structure and performance. The industrial aluminum-containing raw materials, the solvent, and the auxiliary agent are converted into hydrous alumina through a chemical reaction, have a unique structure and performance. Then, the performance of the aerogel is reprocessed, and the solvent and the adjusting agent are used to control the gel network structure. Finally, the alumina aerogel with excellent performance is prepared. The method has low cost, a simple and controllable preparation process, and high added value, thereby realizing industrialized production of the alumina aerogel. BRIEF DESCRIPTION OF DRAWINGS

[0024] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the application and together with the description serve to explain the principles of the application.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0026] Figure 1 A flow chart of a preparation method of an alumina aerogel provided by an embodiment of the present application;

[0027] Figure 2 A microstructure diagram of an alumina aerogel provided by Example 1 of the present application;

[0028] Figure 3 A microstructure diagram of an alumina aerogel provided by Example 2 of the present application;

[0029] Figure 4 A microstructure diagram of an alumina aerogel provided by Example 3 of the present application;

[0030] Figure 5 A microstructure diagram of an alumina aerogel provided by Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0032] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the described range, such as 1, 2, 3, 4, 5 and 6, which applies to any range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0033] In the present application, the orientation words such as "upper" and "lower" are the directions of the drawing surface in the drawings unless otherwise stated. In addition, in the description of the present application, the terms "include", "contain" and the like mean "include but not limited to". In the present text, the relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In the present text, the association relationship of the association object described by "and / or" can represent three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. In the present text, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0034] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0035] In a first aspect, the present application provides a preparation method of an alumina aerogel, please refer to Figure 1 , the method comprises:

[0036] S1, mixing and stirring the industrial aluminum-containing raw material, the first solvent and the auxiliary agent, and then performing chemical reaction to obtain a first slurry;

[0037] In some embodiments, the industrial aluminum-containing raw material includes one of the following: aluminum hydroxide, hydrous aluminum oxide, derivative after treatment of aluminum hydroxide, derivative after treatment of hydrous aluminum oxide.

[0038] In the embodiments of the present application, one of the above-mentioned aluminum hydroxide, hydrous aluminum oxide, derivative after treatment of aluminum hydroxide, derivative after treatment of hydrous aluminum oxide is selected as an industrial aluminum-containing raw material, which is low in price and easy to obtain, can significantly reduce the production cost of aluminum oxide aerogel, and is conducive to the popularization and application of aluminum oxide aerogel. The first solvent can be formic acid, acetic acid, oxalic acid, citric acid, etc., and the auxiliary agent includes a pH regulator and a control agent, wherein the pH regulator can be an acid substance such as nitric acid; the control agent includes one or more of a crystal grain control agent, a directing control agent, and a specific surface control agent; wherein the crystal grain control agent includes one or more of an ammonium salt, an acid or a base, the directing agent includes one or more of inorganic salts such as aluminum nitrate, aluminum chloride, ammonium chloride, aluminum oxide with a molar ratio of crystal water of 0.01-2.5, organic acids such as formic acid and acetic acid, and the surfactant includes one or more of ionic, non-ionic carboxylic acid, benzene sulfonic acid, etc. By selecting different raw materials, different solvents, different auxiliary agents and different reaction conditions, the morphology and structure of the reaction product can be controlled, so as to control the morphology and structure of the aluminum oxide aerogel, thereby improving the blocking performance of the aluminum oxide aerogel, and optimizing the high-temperature resistance and the thermal conductivity of the aerogel. Among them, the above-mentioned aluminum-containing raw material accounts for 1-99% of the weight of the entire reaction system, the weight ratio of the above-mentioned pH regulator to the aluminum-containing raw material is 1-10%, and the weight ratio of the above-mentioned control agent to the aluminum-containing raw material is 0.1-10%. The above-mentioned S1 step specifically includes: mixing and stirring the aluminum-containing raw material, water, pH regulator and control agent at room temperature for 30-60 min; according to the raw material production process, raw material particle size, water content, structure, pH regulator type and amount, control agent type and amount, and different microstructure of the obtained product, the chemical reaction temperature is determined to set whether the reaction temperature for preparing the first slurry is below 100℃ or above 100℃; stirring at the selected reaction temperature for 1-20 h to obtain a first slurry.

[0039] S2, the first slurry is reprocessed to obtain a wet solid; the reprocessing can be filtration or centrifugal processing;

[0040] In some embodiments, the solute is 0.01-0.5 parts by weight relative to 1 part by weight of the second slurry.

[0041] In the embodiment of the present application, the content of the solute in the second slurry is controlled, the degree of polymerization of the particles formed by the polycondensation reaction is low, the gel network structure is open, the product has excellent flexibility and certain strength, thereby having excellent blocking performance and not being easy to powder. If the content of the solute is too much, the thermal insulation performance of the product will be reduced to a certain extent; if the content of the solute is too much, the flexibility and strength of the product will be reduced to a certain extent. Specifically, the solute can be 0.01 parts by weight, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, etc., relative to 1 part by weight of the second slurry, and preferably, the solute can be 0.01-0.25 parts by weight, relative to 1 part by weight of the second slurry.

[0042] S3, adding a second solvent to the wet solid and performing second mixing and stirring to obtain a second slurry;

[0043] In some embodiments, the second solvent includes an alcohol solvent, an amine solvent, and an alkane solvent.

[0044] In the embodiment of the present application, the second solvent is added to the wet solid to replace the first solvent, and the wet solid is uniformly dispersed into a slurry. The role of the alcohol solvent is to act as a solvent, exchange water-alcohol, and lay the foundation for reducing the capillary tension of the wet gel. The alcohol solvent can be methanol, ethanol, and other low surface tension liquids that are miscible with water. The role of the amine solvent is hydrophobic action, and the surface amino group of the solute ion is modified. The amine solvent can be formamide and dimethylformamide. The role of the alkane solvent is to increase the hydrophobicity, flexibility, and help form a three-dimensional network structure. The alkane solvent can be propylene oxide, 3-aminopropyl triethoxysilane, ethylene oxide, and epoxy propylene.

[0045] In some embodiments, the process parameters of the second mixing and stirring include that the stirring temperature is 15-40℃, and the stirring speed is 500-2000r / min.

[0046] In the embodiment of the present application, the temperature of the second mixing and stirring is controlled to prevent solvent evaporation, thereby ensuring the quality and gelling speed of the gel, ensuring the three-dimensional network structure of the gel, and ensuring the performance of the gel. If the stirring temperature is too high, the alcohol solvent will evaporate too fast, the gelling speed will be too fast, the strength will be unstable, and the three-dimensional network structure will be destroyed. If the stirring temperature is too low, the cost will be increased, and cooling auxiliary facilities will be needed. The speed of the second mixing and stirring is controlled to homogenize the solid slurry. If the stirring speed is too high, the energy consumption will be increased, and safety hazards will be caused. If the stirring speed is too low, the homogenization of the slurry will be reduced, and the quality of the aerogel will be reduced. Specifically, the stirring temperature can be 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc., and the stirring speed can be 500r / min, 600r / min, 700r / min, 800r / min, 1000r / min, 1500r / min, 2000r / min, etc.

[0047] S4, adding a regulator to the second slurry, and then performing pH regulation to obtain a third slurry;

[0048] In some embodiments, the pH of the regulator is 7-10.

[0049] In the embodiment of the present application, the pH of the regulator is controlled to make the reaction smooth, form a slurry with good quality, and ensure the performance of the final product. If the pH of the regulator is too large, the reaction will be too fast, a precipitate will be formed, or the product quality will be reduced. If the pH of the regulator is too small, the reaction will be very slow, and the reaction period will be increased. Specifically, the pH of the regulator can be 7, 8, 9, 10, etc.

[0050] In some embodiments, the components of the regulator include a third solvent and a pH regulator.

[0051] In some embodiments, the third solvent includes one of the following: ethanol, methanol, propanol, acetone; and / or,

[0052] The pH regulator includes one of the following: ammonium carbonate, ammonium bicarbonate, methylamine, ethylamine, diethylamine, diisopropyl ethylamine, ammonia.

[0053] In the embodiment of the present application, among the components of the above regulator, the third solvent has the following functions: interchanging with water, and assisting in modifying the surface properties of the particles; and the pH regulator has the following functions: buffering the reaction speed, regulating the reaction process, and thereby ensuring the quality of the slurry.

[0054] Ethanol, methanol, propanol, acetone are selected as the third solvent, which is miscible with water and can reduce the surface tension. Ammonium carbonate, ammonium bicarbonate, methylamine, ethylamine, diethylamine, diisopropyl ethylamine, ammonia are selected as the pH adjuster, which has the following advantages: less harmful, and a small amount can produce obvious effect.

[0055] In some embodiments, the pH of the third slurry is 3-8.

[0056] In the embodiments of the present application, the pH of the third slurry is controlled to control the gelation speed and the quality of the gel. If the pH of the third slurry is too large, a precipitate will be formed to some extent instead of a gel. If the pH of the third slurry is too small, the production cycle will be increased to some extent. Specifically, the pH of the third slurry can be 3, 4, 5, 6, 7, 8, etc.

[0057] S5, sealing the third slurry to obtain a gel;

[0058] S6, drying the gel and then calcining to obtain an alumina aerogel.

[0059] In the embodiments of the present application, S6 specifically comprises: drying the gel at 30-90°C for 5-48h and calcining at 300-1000°C for 2-8h to obtain an alumina aerogel product, which can be used as an alumina ceramic aerogel product.

[0060] In summary, by using the above-mentioned preparation method of the alumina aerogel, the industrial aluminum-containing raw material is used to achieve low cost. The first slurry is in a metastable state, has high activity and good formability, and the micro-morphology is controllable. The micro-morphology of the alumina aerogel can be controlled to obtain an alumina aerogel with excellent performance. The first slurry is subsequently treated and the solvent and the adjusting agent are used to control the gel network structure, so that an alumina aerogel with excellent performance can be finally prepared, and the industrial production can be realized. The excellent performance includes temperature resistance, heat insulation, and block formation performance.

[0061] In a second aspect, the present application provides an alumina aerogel, which is prepared by the method of any one of the embodiments of the first aspect.

[0062] The alumina aerogel is realized based on the above-mentioned preparation method of the alumina aerogel. The specific steps of the preparation method of the alumina aerogel can be referred to the above-mentioned embodiments. Since the alumina aerogel adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0063] The present application is further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not intended to limit the scope of the present application. The experimental methods in the following examples, if no specific conditions are noted, are generally determined according to the national standards. If there is no corresponding national standard, the general international standards, conventional conditions, or the conditions suggested by the manufacturers are used.

[0064] Example 1

[0065] According to the molar ratio, 25.6 moles of Bayer process produced aluminum oxide trihydrate, 0.25 moles of ammonium sulfate as a grain control agent, and 5.12 moles of aluminum-containing hydrate as a directing control agent were mixed uniformly with water, and the pH value was adjusted to about 3 by nitric acid. The mixture was stirred at 150 rpm for 30 minutes at room temperature, and then the temperature was raised to 180°C and reacted for 3 hours at the same speed. After the reaction was completed, a first slurry was obtained;

[0066] The 60 grams of wet solid obtained by centrifugation of the first slurry, 150 milliliters of anhydrous ethanol, 8 milliliters of formamide, and 60 milliliters of propylene oxide were mixed and stirred at a temperature of 25°C and a stirring speed of 1000 r / min to obtain a second slurry. A solution of an ethanol regulator was prepared by mixing 3 milliliters of ammonia water with 20 milliliters of anhydrous ethanol, and the solution was gradually added to the second slurry while adjusting the pH value with ammonia water to obtain a third slurry with a pH value of 6. The third slurry was sealed until it became a gel;

[0067] The gel was dried at a temperature of 60°C for 12 hours, and the wet gel was dried by supercritical drying or other drying methods. The dried product was calcined at 500°C for 2 hours to obtain an aluminum oxide aerogel product.

[0068] Example 2

[0069] According to the molar ratio, 1.15 moles of Bayer process produced aluminum oxide trihydrate, 0.15 moles of high-temperature calcined Bayer process aluminum oxide trihydrate as a directing control agent, and 1% ammonium sulfate as a grain control agent were mixed uniformly with water, and the pH value was adjusted to about 3 by nitric acid. The stirring speed was 150 rpm for 40 minutes, and then the temperature was raised to 200°C and kept for 2 hours. After the reaction was completed, a first slurry was obtained;

[0070] The 60 grams of wet solid obtained by centrifugation of the first slurry, 180 milliliters of anhydrous ethanol, 8 milliliters of formamide, and 60 milliliters of propylene oxide were mixed and stirred at a temperature of 25°C and a stirring speed of 1000 r / min to obtain a second slurry. A solution of an ethanol regulator was prepared by mixing 3 milliliters of ammonia water with 20 milliliters of anhydrous ethanol, and the solution was gradually added to the second slurry while adjusting the pH value with ammonia water to obtain a third slurry with a pH value of 5.

[0071] The third slurry is sealed until it becomes a gel;

[0072] The gel is dried at 30°C for 24h, the wet gel is dried by supercritical drying or other drying method, the dried product is calcined at 500°C for 2h to obtain the alumina aerogel product.

[0073] Example 3

[0074] 25.6 moles of Bayer process produced alumina trihydrate, 0.25 moles of ammonium sulfate as grain control agent, and 5.12 moles of aluminum-containing hydrate as directing control agent are mixed in a molar ratio, and water is added to obtain a first slurry. The pH value of the first slurry is adjusted to about 3 by using nitric acid as a pH value adjusting agent. The mixture is stirred at 150 rpm for 30 minutes at room temperature, and then the temperature is increased to 180°C and the stirring is continued at the same speed for 3h. After the reaction is completed, a second slurry is obtained.

[0075] The 60g of wet solid obtained by centrifuging the first slurry, 240ml of anhydrous ethanol, 8ml of formamide, and 60ml of propylene oxide are mixed and stirred at a temperature of 25°C and a stirring speed of 1100r / min to obtain a third slurry. 3ml of ammonia water and 20ml of anhydrous ethanol are added dropwise to the third slurry, and the pH value is adjusted to 6 by using ammonia water.

[0076] The third slurry is sealed until it becomes a gel;

[0077] The gel is dried at 80°C for 8h, the wet gel is dried by supercritical drying or other drying method, the dried product is calcined at 500°C for 2h to obtain the alumina aerogel product.

[0078] Comparative Example 1

[0079] 6g of aluminum nitrate is dissolved in a mixture of 5ml of water and 30ml of anhydrous ethanol, and the mixture is continuously stirred at 25°C until it is completely dissolved. After the dissolution is completed, 1ml of formamide and 10ml of propylene oxide are added, and the mixture is sealed until it becomes a gel.

[0080] The gel is dried at 60°C for 12h, the wet gel is dried by supercritical drying or other drying method, the dried product is calcined at 500°C for 2h to obtain the alumina aerogel product.

[0081] Examples 1 to 3 and Comparative Example 1 are subjected to performance tests, and the test results are shown in Table 1.

[0082] Table 1: Performance indicators of alumina aerogel

[0083]

[0084] By analyzing Table 1, the alumina aerogels prepared in Examples 1-3 have excellent properties (temperature resistance, heat insulation and block forming), and 1.2-3 moles of alumina containing water can be produced in industrial aluminum-containing raw materials by adding solvents and additives through hydrothermal reaction. With this product with its own unique structure and performance as raw material, excellent alumina aerogel can be prepared by using ethanol as solvent, ammonia as pH regulator and propylene oxide as network enhancer, which can realize industrial production and be applied in different fields such as thermal insulation, catalysis, aerospace, etc. Comparative Example 1 is a conventional method for preparing alumina aerogel, and its comprehensive performance is far inferior to Examples 1-3. Specifically, please refer to the microstructure of the alumina aerogel prepared by the method of Examples 1-3, please refer to Figures 2 to 4 ; wherein, Figure 2 The alumina aerogel of Example 1 has a small fibrous morphology, which is disordered and can offset stress and is not easy to crack, and has good block forming performance; Figure 3 The alumina aerogel of Example 2 has a columnar morphology, and the alumina aerogel has a certain force inside and is not easy to crack, and has good block forming performance; Figure 4 The alumina aerogel of Example 3 has a large fibrous morphology, which is intertwined and stacked, can offset stress and is not easy to crack, and has good block forming performance. Due to the difference in the added components, the uniformity is slightly different; the microstructure of the alumina aerogel prepared by the method of Comparative Example 1 is spherical, please refer to Figure 5 , which is easy to crack and powder, and has poor performance in Table 1.

[0085] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing alumina aerogel, characterized in that, The method includes: The industrial aluminum-containing raw material, the first solvent, and the additives are mixed and stirred, and then a chemical reaction is carried out to obtain the first slurry. The first slurry is further processed to obtain a wet solid, which contains 1.2 to 3 moles of hydrated alumina. A second solvent is added to the wet solid, and a second mixing and stirring is performed to obtain a second slurry; A regulator was added to the second slurry, and then the pH was adjusted to obtain the third slurry. The third slurry is sealed to obtain a gel; The gel was dried and then calcined to obtain alumina aerogel; The first solvent includes one or more of formic acid, acetic acid, oxalic acid, and citric acid; the auxiliary agents include pH adjusters and control agents; the control agents include one or more of grain control agents, directing control agents, and specific surface area control agents; the grain control agents include one or more of ammonium salts, acids, or bases; the directing control agents include one or more of aluminum nitrate, aluminum chloride, ammonium chloride, alumina with a water of crystallization molar ratio of 0.01 to 2.5, formic acid, and acetic acid. The pH of the third slurry is 3-8; The solute is 0.01 to 0.5 parts by weight relative to 1 part by weight of the second slurry; The process parameters for the second mixing and stirring include: stirring temperature of 15℃~40℃, and stirring speed of 500r / min~2000r / min; The second solvent includes alcohol solvents, amine solvents, and alkane solvents; The pH of the regulator is 7-10.

2. The method according to claim 1, characterized in that, The regulator comprises a third solvent. Agents and pH adjusters.

3. The method according to claim 2, characterized in that, The third solvent includes one of the following: ethanol, methanol, propanol, or acetone.

4. An alumina aerogel, characterized in that, The alumina aerogel is prepared by the method according to any one of claims 1 to 3.

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