Aerogel and preparation method thereof
The formulation and processing of gas gels with specific components and methods improve mechanical strength and thermal stability, allowing their use in challenging environments.
Patent Information
- Application Number
- CN202510633330.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-16
- Publication Date
- 2025-07-15
AI Technical Summary
The existing aerogel materials have shortcomings in mechanical properties and thermal stability, especially in high-temperature environments, which limit their application in aerospace and high-temperature industrial insulation.
A certain proportion of silica source, organic modifier and crosslinking agent are used to construct a stable three-dimensional network structure through dynamic aging treatment and vacuum staged heating and drying processes, and optimize the internal structure and pore structure of the aerogel.
It significantly enhances the mechanical properties and thermal stability of the aerogel, allowing it to maintain good performance under external forces and high temperature environments, and broadens the scope of application.
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Figure CN120309307A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of aerogel materials, and particularly to an aerogel and a preparation method thereof. Background Art
[0002] As a nano-porous material with a high specific surface area, low density, and good heat insulation performance, aerogel exhibits broad application prospects in many fields such as aerospace, building energy conservation, and environmental protection.
[0003] However, there are many problems in the preparation and performance of existing aerogel materials. In terms of mechanical properties, due to its ultra-high porosity, aerogel shows fragile characteristics in its microstructure. The ability of its solid skeleton to withstand stress is limited. When subjected to external forces, the larger the porosity, the greater the stress borne by the solid skeleton, and the lower the strength of the aerogel, which makes the aerogel highly brittle and fragile in mechanical properties. Especially for many inorganic aerogels, the fragile mechanical properties seriously hinder their wide application in actual scenarios. For example, in some industrial heat insulation applications that need to withstand a certain amount of mechanical external force, existing aerogel materials are easily damaged by external force impacts, resulting in a decrease or even failure of the heat insulation performance.
[0004] From the perspective of thermal stability, traditional aerogel materials have obvious limitations in high-temperature environments. Taking the traditional SiO2 aerogel commonly used in heat insulation fields below 650°C as an example, when the temperature rises, its structure is prone to collapse, which then leads to the densification of the material and ultimately the loss of its original excellent properties. Other oxide-based aerogels also face the problem of insufficient high-temperature thermal stability, which greatly limits the application of oxide-based aerogels in high-temperature fields. In the aerospace field, during the high-speed flight of aircraft, high temperatures are generated due to air friction. At this time, existing aerogel materials are difficult to meet the heat insulation requirements in long-term and high-temperature environments; in the heat insulation applications of high-temperature industrial furnaces, existing aerogels cannot stably maintain their heat insulation performance in long-term high-temperature environments either.
[0005] Therefore, it is necessary to provide an aerogel and a preparation method thereof with a simple preparation process, low cost, and excellent mechanical properties and thermal stability to solve the above technical problems. Summary of the Invention
[0006] The purpose of the present invention is to provide an aerogel and a preparation method thereof to solve the problems of poor mechanical properties and thermal stability of existing aerogels.
[0007] To achieve the above purpose, the present invention provides the following technical solutions:
[0008] In a first aspect, the present invention provides an aerogel. By weight, the raw materials of the aerogel include 20-30 parts of a silica source, 5-10 parts of an organic modifier, 2-5 parts of a crosslinking agent, 0.5-2 parts of a catalyst, and 50-80 parts of a solvent. Among them, the organic modifier is composed of a first silane compound and a second silane compound. The first silane compound is an alkyltrimethoxysilane, and the second silane compound is a fluorosilane; the crosslinking agent includes tetraethoxysilane and a bifunctional silane, and the bifunctional silane contains an active group that can react with silanol groups.
[0009] Preferably, the fluorosilane accounts for 5%-20% of the total mass of the organic modifier, and the bifunctional silane accounts for 20%-40% of the total mass of the crosslinking agent. This specific proportion setting helps to optimize the performance of the aerogel. For example, the fluorosilane can enhance the hydrophobicity of the aerogel, and an appropriate proportion of the bifunctional silane can effectively improve the crosslinking degree of the aerogel, thereby enhancing its mechanical properties.
[0010] Preferably, the silica source can be selected from at least one of tetraethyl orthosilicate and silica sol; the alkyltrimethoxysilane is methyltrimethoxysilane or ethyltrimethoxysilane, the fluorosilane is tridecafluorooctyltrimethoxysilane or perfluorodecyltrimethoxysilane, the bifunctional silane is a silane containing an amino group, a mercapto group or an epoxy group; the catalyst is hydrochloric acid or ammonia water; the solvent is ethanol or a mixture of ethanol and water. The selection of these specific raw materials is determined based on their chemical properties and functions in the preparation process of the aerogel. They cooperate with each other to jointly promote the formation and performance optimization of the aerogel.
[0011] In terms of the raw material composition of the present invention, the aerogel uses specific proportions of a silica source, an organic modifier, a crosslinking agent, etc. The bifunctional silane in the crosslinking agent, with its active group that can react with silanol groups, can build a more stable three-dimensional network structure with other components. The organic modifier composed of the fluorosilane and the alkyltrimethoxysilane helps to stabilize the internal structure while improving the surface properties of the aerogel. The bifunctional silane accounts for 20%-40% of the total mass of the crosslinking agent, and this proportion ensures that the crosslinking reaction proceeds fully, enhancing the overall strength of the aerogel. When subjected to external forces, the aerogel can better disperse the stress and avoid breakage due to stress concentration.
[0012] On the other hand, the raw materials selected in the present invention itself have a certain thermal stability basis. For example, the silica source, as the framework component of the aerogel, has good high-temperature resistance; while forming a stable structure, the organic modifier and the crosslinking agent also help to improve the overall thermal stability of the aerogel, enabling the aerogel to maintain good performance at high temperatures.
[0013] In a second aspect, the present invention provides a method for preparing an aerogel, including:
[0014] Step 1: Preparation of the precursor solution: Mix the above-mentioned raw materials and stir them using a magnetic stirrer. During stirring, place the reaction vessel in a constant temperature water bath at 25 - 30 °C to form a uniform precursor solution. This temperature condition helps to ensure the uniformity of the raw material mixture and the stability of the reaction.
[0015] Step 2: Generation of the wet gel: Carry out a catalytic reaction using hydrochloric acid or ammonia water. When using hydrochloric acid as a catalyst, continuously drip it until the pH reaches 2; when using ammonia water as a catalyst, continuously drip it until the pH reaches 10, thereby generating a wet gel. Precise control of the pH value during the catalytic process has a crucial impact on the formation and structure of the wet gel.
[0016] Step 3: Dynamic aging treatment: Carry out dynamic aging treatment on the wet gel, including gradient adjustment of the solvent vapor pressure and application of mechanical vibration. Among them, the rate of decrease in the solvent vapor pressure gradient is 5 - 10 kPa / 2h, the mechanical vibration frequency is 50 - 100 Hz, and the aging time is 6 - 10 h. This treatment method can improve the internal structure of the wet gel, making it more uniform and stable, and thus enhancing the performance of the aerogel.
[0017] Step 4: Solvent replacement: Use ultrasonic assistance and ethyl acetate or acetone as the replacement solvent for solvent replacement. The number of replacement times is 2 - 3 times, and the single replacement time is 1 - 2 h. Ultrasonic assistance can improve the replacement efficiency and effectively remove the original solvent in the wet gel, laying a good foundation for the subsequent drying process.
[0018] Step 5: Vacuum staged heating drying: Carry out staged heating drying under vacuum conditions. The initial temperature is 80 - 90 °C for drying for 1 - 2 h, the intermediate temperature is 100 - 110 °C for drying for 4 - 6 h, and the final temperature is 120 - 130 °C and the pressure is 0.01 - 0.03 MPa for drying for 2 - 4 h. Use a programmed heating vacuum drying oven. The initial stage vacuum degree is 0.06 - 0.08 MPa, the intermediate stage is 0.04 - 0.06 MPa, and in the final stage, the sample is dried on a rotating tray at 1 - 2 r / min. Staged heating drying and specific vacuum degree control can avoid problems such as structural collapse of the aerogel during the drying process and ensure that it has a good pore structure and performance.
[0019] In the dynamic aging treatment link of the preparation method of the present invention, by gradient adjusting the solvent vapor pressure and applying mechanical vibration, the internal structure of the wet gel is made more uniform and orderly. The rate of decrease in the solvent vapor pressure gradient is 5 - 10 kPa / 2h, the mechanical vibration frequency is 50 - 100 Hz, and the aging time is 6 - 10 h. Under such conditions, the pore structure inside the wet gel is optimized, reducing defects and weak points, and further enhancing the mechanical properties of the aerogel.
[0020] On the other hand, vacuum staged heating drying is a key step to improve thermal stability. Dry at an initial temperature of 80 - 90°C for 1 - 2 h, at an intermediate temperature of 100 - 110°C for 4 - 6 h, and at a final temperature of 120 - 130°C and a pressure of 0.01 - 0.03 MPa for 2 - 4 h. At the same time, cooperate with a programmed heating vacuum drying oven, and set appropriate vacuum degrees at different stages, from 0.06 - 0.08 MPa in the initial stage to 0.04 - 0.06 MPa in the intermediate stage. This drying method enables the aerogel to slowly remove the solvent during the drying process, avoiding the collapse of the pore structure caused by rapid drying, forming a stable pore structure, and enhancing the stability of the aerogel in a high-temperature environment.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0022] 1. The present invention realizes the optimization of the internal structure of the aerogel. The bifunctional silane in the cross-linking agent fully reacts with the silanol groups to construct a stable three-dimensional network structure, effectively enhancing the overall strength of the aerogel. At the same time, the organic modifier acts synergistically to stabilize the internal structure and improve the ability of the aerogel to disperse stress. In the dynamic aging treatment process, the internal pore structure of the wet gel is further optimized, reducing defects and weak points. This makes the prepared aerogel have excellent anti-breakage ability. When subjected to external forces, it can effectively resist deformation and rupture, greatly extending the service life and meeting the requirements of many application scenarios with strict requirements for the mechanical properties of materials.
[0023] 2. The vacuum staged heating drying process adopted by the present invention enables the aerogel to slowly remove the solvent during the drying process, avoiding the collapse of the pore structure, thereby forming a stable pore structure. The selected raw materials themselves have a good thermal stability foundation. During the construction of a stable structure, the overall thermal stability of the aerogel is further enhanced. This enables the aerogel to maintain good performance in a high-temperature environment and will not cause structural damage or performance deterioration due to thermal expansion and contraction or high-temperature chemical reactions, broadening the application scope of the aerogel in high-temperature fields such as aerospace and high-temperature industrial heat insulation. Description of the Drawings
[0024] Figure 1 It is a broken line graph comparing the compressive strengths of the aerogels prepared in the examples and comparative examples provided by the present invention;
[0025] Figure 2 It is a broken line graph comparing the mass loss rates of the aerogels prepared in the examples and comparative examples provided by the present invention in a high-temperature environment of 150°C. Detailed Embodiments
[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the protection scope of the present invention.
[0027] Example 1
[0028] 1. Raw material preparation: Accurately weigh 20 parts of tetraethyl orthosilicate as the silicon dioxide source, 5 parts of organic modifier (wherein fluorosilane accounts for 5% of the total mass of the organic modifier, and the first silane compound is methyltrimethoxysilane), 2 parts of crosslinking agent (bifunctional silane accounts for 20% of the total mass of the crosslinking agent, and the crosslinking agent includes tetraethoxysilane and bifunctional silane containing amino group), 0.5 part of hydrochloric acid as the catalyst, and 50 parts of ethanol as the solvent.
[0029] 2. Preparation process:
[0030] Add the above raw materials into a reaction vessel, place it in a constant temperature water bath at 25°C, and stir with a magnetic stirrer to form a precursor solution.
[0031] Catalyze with hydrochloric acid, continuously drip, monitor the pH value of the solution, and stop dripping when the pH reaches 2 to generate a wet gel.
[0032] Perform dynamic aging treatment on the wet gel, and treat it for 6 hours under the conditions of a solvent vapor pressure gradient reduction rate of 5 kPa / 2 h and a mechanical vibration frequency of 50 Hz.
[0033] Adopt ultrasonic assistance, and perform 2 times of solvent replacement with ethyl acetate as the replacement solvent, with each replacement time of 1 h.
[0034] Put the sample into a programmed temperature vacuum drying oven. In the initial stage, the vacuum degree is 0.06 MPa, and the temperature is 80°C for drying for 1 h; in the intermediate stage, the vacuum degree is 0.04 MPa, and the temperature is 100°C for drying for 4 h; in the final stage, the temperature is 120°C and the pressure is 0.01 MPa for drying for 2 h. The sample is dried on a rotating tray at 1 r / min to obtain an aerogel product.
[0035] Example 2
[0036] 1. Raw material preparation: Weigh 25 parts of silica sol as the silicon dioxide source, 8 parts of organic modifier (fluorosilane accounts for 12% of the total mass of the organic modifier, and the first silane compound is ethyltrimethoxysilane), 3 parts of crosslinking agent (bifunctional silane accounts for 30% of the total mass of the crosslinking agent, and the crosslinking agent includes tetraethoxysilane and bifunctional silane containing mercapto group), 1 part of ammonia water as the catalyst, and 65 parts of a mixed solvent of ethanol and water (the volume ratio of ethanol to water is 3:1).
[0037] 2. Preparation process:
[0038] In a constant temperature water bath at 28 °C, the raw materials are mixed and stirred by a magnetic stirrer to form a precursor solution.
[0039] Catalyzed by ammonia water, 2 - 3 drops are added per second until the pH reaches 10 to form a wet gel.
[0040] Dynamic aging treatment is carried out with a solvent vapor pressure gradient reduction rate of 8 kPa / 2 h, a mechanical vibration frequency of 80 Hz, and an aging time of 8 h.
[0041] Using acetone as the replacement solvent, ultrasonic - assisted replacement is carried out 3 times, with a single replacement time of 1.5 h.
[0042] During drying, in the initial stage, the vacuum degree is 0.07 MPa, the temperature is 85 °C, and drying is carried out for 1.5 h; in the middle stage, the vacuum degree is 0.05 MPa, the temperature is 105 °C, and drying is carried out for 5 h; in the final stage, the temperature is 125 °C and the pressure is 0.02 MPa, and drying is carried out for 3 h. The sample is dried on a rotating tray at 1.5 r / min to obtain an aerogel.
[0043] Example 3
[0044] 1. Raw material preparation: Take 30 parts of a mixture of tetraethyl orthosilicate and silica sol (mass ratio 1:1) as the silica source, 10 parts of an organic modifier (fluorosilane accounts for 20% of the total mass of the organic modifier, and the first silane compound is methyltrimethoxysilane), 5 parts of a cross - linker (bifunctional silane accounts for 40% of the total mass of the cross - linker, and the cross - linker includes tetraethoxysilane and a bifunctional silane containing an epoxy group), 2 parts of hydrochloric acid as a catalyst, and 80 parts of ethanol as a solvent.
[0045] 2. Preparation process:
[0046] The reaction vessel is placed in a constant temperature water bath at 30 °C, and the raw materials are stirred by a magnetic stirrer to form a precursor solution.
[0047] Catalyzed by hydrochloric acid, 1 - 2 drops are added per second, and a wet gel is formed when the pH reaches 2.
[0048] During dynamic aging treatment, the solvent vapor pressure gradient reduction rate is 10 kPa / 2 h, the mechanical vibration frequency is 100 Hz, and the aging time is 10 h.
[0049] Under ultrasonic assistance, ethyl acetate is used for replacement 3 times, with each replacement time of 2 h.
[0050] The drying process is as follows: in the initial stage, the vacuum degree is 0.08 MPa, the temperature is 90 °C, and drying is carried out for 2 h; in the middle stage, the vacuum degree is 0.06 MPa, the temperature is 110 °C, and drying is carried out for 6 h; in the final stage, the temperature is 130 °C and the pressure is 0.03 MPa, and drying is carried out for 4 h. The sample is dried on a rotating tray at 2 r / min to obtain an aerogel.
[0051] Comparative Example 1: Preparation of aerogel using traditional process
[0052] 1. Raw material preparation: Prepare raw materials according to the conventional aerogel preparation method. Select 20 parts of tetraethyl orthosilicate as the silicon dioxide source, 3 parts of ordinary organic modifiers (without fluorosilane), 1 part of ordinary crosslinking agent (without bifunctional silane), 0.3 part of catalyst (hydrochloric acid), and 40 parts of ethanol as the solvent.
[0053] 2. Preparation process: Simply mix and stir the raw materials, carry out catalytic reaction at room temperature to generate wet gel, without dynamic aging treatment, directly replace with conventional solvent once, and heat up to 100 °C at one time in an ordinary drying oven and dry to constant weight.
[0054] 3. Performance comparison: Compare the performance of the aerogel prepared in Comparative Example 1 with that of the aerogels prepared in Examples 1-3. The results show that the mechanical properties of the aerogel in Comparative Example 1 are significantly worse, and it breaks under a small external force; the thermal stability is also not good. After being placed in a high-temperature environment of 150 °C for a period of time, its structure and properties change significantly. While the aerogels prepared in Examples 1-3 can maintain good integrity and performance stability under the same external force and high-temperature conditions, fully reflecting the advantages of the present invention.
[0055] Comparative Example 2: Changing the proportion of key raw material components
[0056] Raw material preparation: Select 20 parts of tetraethyl orthosilicate as the silicon dioxide source, 5 parts of organic modifiers (where fluorosilane accounts for 1% of the total mass of organic modifiers, and the first silane compound is methyltrimethoxysilane), 2 parts of crosslinking agent (bifunctional silane accounts for 10% of the total mass of crosslinking agent, and the crosslinking agent includes tetraethoxysilane and bifunctional silane containing amino group), 0.5 part of hydrochloric acid as the catalyst, and 50 parts of ethanol as the solvent. This comparative example mainly changes the proportion of fluorosilane and bifunctional silane, deviating from the range set in the examples of the invention.
[0057] Preparation process: Operate according to the preparation method of Example 1, that is, place it in a constant temperature water bath at 25 °C, use a magnetic stirrer to stir to form a precursor solution; catalyze with hydrochloric acid, continuously drip until the pH reaches 2 to generate wet gel; during dynamic aging treatment, the solvent vapor pressure gradient reduction rate is 5 kPa / 2 h, the mechanical vibration frequency is 50 Hz, and treat for 6 h; use ultrasonic assistance, use ethyl acetate as the replacement solvent for 2 times of solvent replacement, and each replacement time is 1 h; put it into a programmed temperature vacuum drying oven, the initial stage vacuum degree is 0.06 MPa, the temperature is 80 °C and dry for 1 h; the middle stage vacuum degree is 0.04 MPa, the temperature is 100 °C and dry for 4 h; the final stage temperature is 120 °C, the pressure is 0.01 MPa and dry for 2 h, and the sample is dried on a rotating tray at 1 r / min to obtain an aerogel product.
[0058] Performance analysis: Since the proportion of fluorosilane is too low, the hydrophobicity of the aerogel will decrease significantly, affecting its stability in a humid environment. The insufficient proportion of bifunctional silane leads to insufficient crosslinking degree, resulting in a significant reduction in the mechanical properties of the aerogel, and it is prone to breakage under a small external force.
[0059] Comparative Example 3: Simplify the key steps of the preparation process
[0060] Raw material preparation: The same as in Example 1, weigh 20 parts of tetraethyl orthosilicate as the silicon dioxide source, 5 parts of organic modifier (where the fluorosilane accounts for 5% of the total mass of the organic modifier, and the first silane compound is methyltrimethoxysilane), 2 parts of crosslinking agent (the bifunctional silane accounts for 20% of the total mass of the crosslinking agent, and the crosslinking agent includes tetraethoxysilane and an amino-containing bifunctional silane), 0.5 part of hydrochloric acid as a catalyst, and 50 parts of ethanol as a solvent.
[0061] Preparation process: Add the raw materials into a reaction vessel and stir at room temperature to form a precursor solution; catalyze with hydrochloric acid and continuously drip until the pH reaches 2 to generate a wet gel; the wet gel is not subjected to dynamic aging treatment; adopt a common stirring method, use ethyl acetate as a replacement solvent for 1 solvent replacement, and the replacement time is 1 h; in a common drying oven, raise the temperature to 100 °C at one time and dry to a constant weight. This comparative example simplifies the dynamic aging treatment, solvent replacement, and drying steps in the preparation process.
[0062] Performance analysis: Omitting the dynamic aging treatment results in poor uniformity and stability of the internal structure of the aerogel and a reduction in mechanical properties. Reducing the number and time of solvent replacement will cause residual original solvents in the wet gel, affecting the pore structure and thermal stability of the aerogel. Drying the aerogel by raising the temperature at one time in a common drying oven easily causes the structure of the aerogel to collapse due to too rapid temperature change, resulting in a significant decline in both its mechanical properties and thermal stability. The experimental data of each of the above examples and comparative examples are compared in the following table:
[0063]
[0064] As can be seen from the data, the aerogels prepared in Examples 1-3 are significantly superior to the comparative examples in terms of mechanical properties and thermal stability. Example 3 has the highest compressive strength, reaching 4.5 MPa, and the mass loss rate is only 2.0% at high temperature, indicating that its mechanical properties and thermal stability are the best. In Comparative Example 1, due to the use of traditional processes, key raw materials and treatment steps are lacking, resulting in the worst mechanical properties and thermal stability. In Comparative Example 2, after changing the proportion of key components of the raw materials, the crosslinking degree and hydrophobicity are affected, leading to a decrease in mechanical properties and thermal stability. In Comparative Example 3, the key steps of the preparation process are simplified, and the internal structure and pore structure of the aerogel are damaged, and the mechanical properties and thermal stability are also greatly reduced. These data fully verify the effectiveness of the present invention in improving the mechanical properties and thermal stability of aerogels.
[0065] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced by the present invention.
Claims
1. Aerogel, characterized in that, By weight parts, the raw materials include: 20 - 30 parts of silica source, 5 - 10 parts of organic modifier, 2 - 5 parts of crosslinking agent, 0.5 - 2 parts of catalyst, and 50 - 80 parts of solvent; The organic modifier contains a first silane compound and a second silane compound, where the first silane compound is an alkyltrimethoxysilane and the second silane compound is a fluorosilane; The crosslinking agent contains tetraethoxysilane and a bifunctional silane, and the bifunctional silane contains an active group that can react with silanol groups.
2. The aerogel according to claim 1, wherein, The fluorosilane accounts for 5% - 20% of the total mass of the organic modifier, and the bifunctional silane accounts for 20% - 40% of the total mass of the crosslinking agent.
3. The aerogel according to claim 1 or 2, characterized in that, The silica source is selected from at least one of tetraethyl orthosilicate and silica sol; The alkyltrimethoxysilane is methyltrimethoxysilane or ethyltrimethoxysilane, the fluorosilane is tridecafluorooctyltrimethoxysilane or perfluorodecyltrimethoxysilane, and the bifunctional silane is a silane containing amino, mercapto, or epoxy groups; The catalyst is hydrochloric acid or ammonia water; The solvent is ethanol or a mixture of ethanol and water.
4. A method for preparing the aerogel according to any one of claims 1-3, characterized in that, It includes the following steps: (1) Mix and stir the raw materials to form a precursor solution; (2) Catalyze the reaction to generate a wet gel; (3) Perform dynamic aging treatment on the wet gel, and the dynamic aging treatment includes gradient - regulating the solvent vapor pressure and applying mechanical vibration; (4) Perform solvent replacement using an environmentally friendly solvent; (5) Dry by step - wise heating under vacuum conditions.
5. The preparation method according to claim 4, characterized in that, In step (1), use a magnetic stirrer to stir, and place the reaction vessel in a constant - temperature water bath at 25 - 30 °C during stirring.
6. The preparation method according to claim 4, wherein, In step (2), catalyze with hydrochloric acid or ammonia water; When catalyzing with hydrochloric acid, continuously drip until the pH reaches 2; When catalyzing with ammonia water, continuously drip until the pH reaches 10.
7. The preparation method according to claim 4, wherein In step (3), in the dynamic aging treatment, the rate of gradient reduction of the solvent vapor pressure is 5 - 10 kPa / 2h, the mechanical vibration frequency is 50 - 100 Hz, and the aging time is 6 - 10 h.
8. The preparation method according to claim 4, characterized in that: In step (4), the solvent replacement is assisted by ultrasound, the replacement solvent is ethyl acetate or acetone, the number of replacement times is 2 - 3 times, and the single - time replacement time is 1 - 2 h.
9. The preparation method according to claim 4, characterized in that: In step (5), the step - wise heating drying includes: drying at an initial temperature of 80 - 90 °C for 1 - 2 h, drying at an intermediate temperature of 100 - 110 °C for 4 - 6 h, and drying at a final temperature of 120 - 130 °C and a pressure of 0.01 - 0.03 MPa for 2 - 4 h.
10. The preparation method according to claim 4, characterized in that: In step (5), use a programmable - temperature vacuum drying oven. The initial - stage vacuum degree is 0.06 - 0.08 MPa, the intermediate - stage is 0.04 - 0.06 MPa, and in the final stage, the sample is dried on a rotating tray at 1 - 2 r / min.