A method for producing a silicon-based aerogel material at ambient pressure

Abstract

This invention discloses a method for producing silicon-based aerogel materials under normal pressure drying, comprising the following steps: mixing silicate and sulfuric acid in a certain proportion to prepare a coating solution; coating a prepared substrate with the coating solution, then immersing it in the coating solution for a period of time to allow gelation; thoroughly cleaning the gelled substrate sequentially with water and alcohol solutions; modifying the cleaned gelled substrate; and finally drying it under normal pressure to obtain the silicon-based aerogel material. This invention achieves the production of aerogel materials under normal pressure conditions, which differs from the supercritical drying method for producing aerogels. The low-pressure production conditions are easier to control, safer, and can reduce equipment investment.

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology, and more specifically to a method for producing silicon-based aerogel materials by atmospheric pressure drying. Background Technology

[0002] In existing technologies, the post-processing for producing silicon-based aerogel materials includes supercritical drying and freeze-drying. However, supercritical drying requires high temperature and high pressure (e.g., ethanol's supercritical temperature is 243℃, and its supercritical pressure is 6.3 MPa; carbon dioxide's supercritical temperature is 31.1℃, and its supercritical pressure is 7.29 MPa), placing high demands on the drying containers and making continuous and large-scale production difficult, significantly increasing the cost of aerogels. Furthermore, the operation is highly dangerous. The organic raw materials used are flammable, explosive, toxic, and volatile, resulting in drawbacks such as high equipment investment, high safety risks, and complex control systems. A tragic explosion of a high-pressure aerogel drying device occurred in Europe. Traditional freeze-drying methods suffer from problems such as aerogel structure damage, difficulty in controlling pore size, and excessively long drying times.

[0003] CN201110100550.7 discloses a low-cost method for preparing silica-based aerogels with different contact angles by atmospheric pressure drying. The method involves mixing sodium silicate and deionized water, adjusting the pH to acidic, and allowing the gel to form. After aging for 2-6 days, the gel is soaked and washed in a water bath at 35-60°C for 24 hours. The wet gel is then immersed in a modification solution and surface modified at 50°C for 24 hours. A certain amount of n-hexane is added to exchange the unreacted modifier twice within 24 hours. The gel is then subjected to graded drying at atmospheric pressure and finally cooled to room temperature to obtain the modified silica-based aerogel. However, in this process, the acid is added dropwise to the sodium silicate solution, making it difficult to control the pH to acidic. At pH 9-10, the aerogel easily solidifies into solid silica without an aerogel structure, hindering industrialization. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for producing silicon-based aerogel materials by atmospheric pressure drying, which solves the defects of existing drying processes for preparing aerogels, such as high requirements for drying containers, large investment, and the use of flammable and explosive organic raw materials.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for producing silicon-based aerogel materials by atmospheric pressure drying includes the following steps:

[0007] S1. Coating: Sodium silicate and sulfuric acid are mixed evenly in a certain proportion to obtain a coating solution; and the coating solution is used to coat the substrate.

[0008] S2, Immersion: The coated substrate is immersed in an immersion tank containing the coating solution.

[0009] S3, Gel: Gel treatment is performed on the substrate after S2 treatment;

[0010] S4. Preparation of roll / sheet materials: The gelled substrate is made into roll materials or kept as gelled sheets;

[0011] S5. Water washing: Place the roll / sheet material obtained in S4 into the aerogel roll material preparation tank and / or aerogel sheet material preparation box, wash with water, and use a self-circulating pump to circulate and wash the gel substrate in the aerogel roll material preparation tank and / or aerogel sheet material preparation box.

[0012] S6. Alcohol washing: After water washing, a certain amount of alcohol solution is introduced into the aerogel roll material preparation tank and / or aerogel sheet material preparation box for alcohol washing, and the alcohol solution is circulated and washed on the gel substrate using a self-circulating pump.

[0013] S7. Modification: After alcohol washing, the modification solution is introduced into the aerogel roll material preparation tank and / or aerogel sheet material preparation box to modify the gel substrate; wherein, the modification solution is prepared by mixing the modifier and the modifying solvent in a mass ratio of 1~10:90~99;

[0014] S8. Drying: After modification, inert gas is introduced into the aerogel roll preparation tank and / or aerogel sheet preparation box, and the gel substrate is dried at normal pressure at 70~150℃ to obtain silicon-based aerogel material.

[0015] Furthermore, the coating solution of S1 is obtained by thoroughly mixing 5%~50wt% sodium silicate and 10%~50wt% sulfuric acid at a volume ratio of 3~6:1.

[0016] Furthermore, in step S2, the sample is soaked at 30-80°C for 3-6 minutes and then removed; in step S3, the gel treatment is gelled at 30-60°C for 0.5-1 hour.

[0017] Furthermore, S5 and S6 involve washing the gelled substrate with water and alcohol solutions 3 to 5 times at 30 to 65°C.

[0018] Furthermore, step S7 involves placing the cleaned gel substrate into a modification solution for modification, with the modification temperature being 45~60℃ and the modification time being 2~6h.

[0019] Furthermore, in S7, the modifier is any one of trimethylchlorosilane, dimethyldichlorosilane, and trimethylmethoxysilane, and the modifying solvent is any one of hexamethyldisiloxane, n-hexane, and n-heptane.

[0020] Furthermore, in step S5, the wastewater after cleaning is discharged into the first return tank, a neutralizing agent is added to the first return tank to neutralize the acidic substances in the water, and a cooling medium is introduced into the cooling device to control the temperature at 5~15℃. After the solids in the aqueous solution are precipitated, the water is recovered and reused.

[0021] Furthermore, in step S6, the cleaned wastewater alcohol solution is transferred from the first return tank to the second return tank, and then the waste liquid is transported to the distillation column using the first pump. The operating pressure of the distillation column is controlled at -10~50 kPa(G); the top temperature of the column is controlled at 30~90℃; and the bottom temperature of the column is controlled at 70~150℃. The alcohol in the mixed solution is recovered and reused.

[0022] Furthermore, in step S7, the modified solution is returned to the modified solution preparation tank. After separation, the upper layer is recovered as a modified solvent for reuse. The lower layer flows into the second return tank, and a neutralizing agent is introduced into the second return tank to neutralize the acidic substances in the solution. Then, the waste liquid is sent to the distillation column by the first pump for recycling.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention enables the drying of aerogel materials under normal pressure. Compared to existing supercritical drying technologies for aerogel production, low-pressure production conditions are easier to control, safer, and require less equipment investment, making them more suitable for mass production of aerogels. Furthermore, compared to supercritical drying technology, this normal-pressure drying technology offers significant cost advantages in terms of equipment investment and silicon source, making it suitable for large-scale production of low-cost aerogels. The establishment of this process route can greatly reduce the production cost of aerogel composite materials and has significant demonstrative value in terms of the systematic nature of product manufacturing processes.

[0025] 2. The method of the present invention uses inorganic raw materials, which are non-flammable and do not easily volatilize, have low toxicity, and are relatively inexpensive.

[0026] 3. The aerogel prepared by the method of the present invention can recycle and reuse key auxiliary materials such as organic solvents, water and inert gases, which can reduce raw material costs. The overall process is simple and reliable, and the product has excellent quality indicators and is easy to mass-produce industrially. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the equipment structure for the preparation and transfer of the gel substrate, which is applicable to the method of the present invention.

[0028] Figure 2 This is a schematic diagram of the post-processing equipment for the gel substrate used in the method of the present invention.

[0029] In the diagram, 1 is a sol mixer, 2 is an impregnation tank, 3 is a heat preservation device, 4 is a first conveying device, 5 is a second conveying device, 6 is a roll material preparation machine, 7 is a sheet transport vehicle, 8 is an aerogel roll material preparation tank, 9 is an aerogel sheet material preparation box, 10 is a modified solution preparation tank, 11 is a first unloading tank, 12 is a second unloading tank, 13 is a distillation column, 14 is a first heating device, 15 is a second heating device, 16 is a first self-circulating pump, 17 is a second self-circulating pump, 18 is a hoisting mechanism, 19 is a first condensing device, 20 is a second condensing device, 21 is a stirrer, 22 is a cooling device, 23 is a first liquid pump, and 24 is a shutter. Detailed Implementation

[0030] The embodiments of the present invention will be described in further detail below with reference to specific examples.

[0031] The numerical ranges in this invention should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended, meaning that they include but are not limited to.

[0033] Unless otherwise specified, the experimental methods used in this invention are all conventional methods.

[0034] Unless otherwise specified, all materials and reagents used in this invention can be purchased or synthesized by known methods.

[0035] In the quantitative experiments of this invention, each experiment was repeated three times, and the average value of the results was taken.

[0036] Example 1

[0037] See Figure 1 and Figure 2 A method for preparing silicon-based aerogel materials by atmospheric pressure drying specifically includes the following steps:

[0038] S1. Coating: 5 wt% sodium silicate and 10 wt% sulfuric acid are mixed evenly at a volume ratio of 3:1. The mixing temperature is controlled at 30℃ and the mixing time is 1 minute to obtain the coating solution. The discharge port of the sol mixer is controlled by the controller to ensure that the coating solution flows evenly onto the substrate laid by the first conveying device for coating.

[0039] S2, Immersion: The first conveyor moves forward at a constant speed and sends the coated substrate into an immersion tank containing the coating solution for immersion at 30°C for 3 minutes; the speed of the first conveyor is controlled to be 0.1~5m / s, preferably 0.5~3m / s.

[0040] S3, Gel: The impregnated substrate is then sent to the second conveying device by the hoisting mechanism. The substrate is then gelled by the heat preservation device. The gelation temperature is 30℃ and the gelation time is 1 hour. The speed of the second conveying device is controlled to be 0.1~5m / s, preferably 0.5~3m / s.

[0041] S4. Preparation of roll / sheet materials: The gelled substrate is sent to the vicinity of the gel roll material preparation machine through the second conveying device, and the roll material preparation machine is used to roll the gelled substrate; or the gelled substrate is directly dropped into the sheet transport vehicle for later use.

[0042] S5. Lifting: The gel roll is lifted into the aerogel roll preparation tank by a lifting mechanism, or the transport vehicle carrying the gel sheet is driven into the aerogel sheet preparation box for post-processing.

[0043] S6. Water Washing: Water is piped into the aerogel roll preparation tank and / or aerogel sheet preparation box, and a self-circulating pump is used to circulate and wash the aerogel substrate within the device. Specifically, the amount of water added is controlled to be 2-10 times the volume of the aerogel substrate, preferably 3-5 times; the water washing temperature is controlled to be 30-65℃, preferably 40-60℃; the number of cycles is controlled to be 2-10 times, preferably 3-5 times; and the water washing process time is controlled to be 2-8 hours, preferably 3-6 hours. In this embodiment, the washing water volume is 3 times the volume of the aerogel substrate; the water washing temperature is controlled to be 30℃; the number of cycles is controlled to be 3; and the water washing process time is controlled to be 3 hours.

[0044] Then, the wastewater after cleaning is discharged into the first return tank. A neutralizing agent is added to the first return tank to neutralize the acidic substances in the water. Cooling medium is introduced into the cooling device to control the temperature at 5~15℃. After the solids in the aqueous solution are precipitated, the water is recovered and reused.

[0045] S7. Alcohol Washing: After water washing, a certain amount of alcohol solution is introduced into the aerogel roll material preparation tank and / or aerogel sheet material preparation box, and a self-circulating pump is used to circulate and wash the gel substrate in the device. Specifically, the amount of alcohol added is controlled to be 2-10 times the volume of the substrate, preferably 3-5 times; the alcohol washing temperature is controlled to be 30-80℃, preferably 40-60℃; the number of cycles is controlled to be 2-10 times, preferably 3-5 times; and the alcohol washing process time is controlled to be 2-8 hours, preferably 3-6 hours. In this embodiment, the amount of alcohol is 3 times the volume of the gel substrate; the alcohol washing temperature is controlled to be 30℃; the number of cycles is controlled to be 3 times; and the alcohol washing process time is controlled to be 3 hours.

[0046] The cleaned wastewater alcohol solution is then transferred from the first return tank to the second return tank. The waste liquid is then transported to the distillation column using the first pump. The operating pressure of the distillation column is controlled at -10~50 kPa(G), preferably 20~30 kPa(G); the top temperature is controlled at 30~90℃, preferably 50~80℃; and the bottom temperature is controlled at 70~150℃, preferably 90~120℃. The alcohol in the mixed solution is recovered and reused.

[0047] S8. Modification: Add modifier (trimethylmethoxysilane) and modifying solvent (n-heptane) to the modification solution preparation tank at a mass ratio of 1:99 and stir evenly with a stirrer to obtain the modified solution.

[0048] After alcohol washing, the modified solution is piped to an aerogel roll preparation tank and / or an aerogel sheet preparation box to modify the gel substrate. Specifically, the amount of modified solution added is controlled to be 2-10 times the volume of the substrate, preferably 3-5 times; the modification reaction temperature is controlled to be 45-60℃; the number of cycles is controlled to be 2-10 times, preferably 3-5 times; and the modification process time is controlled to be 2-6 hours, preferably 3-5 hours. In this embodiment, the modification treatment temperature is 45℃ and the modification treatment time is 2 hours.

[0049] The modified solution is circulated within the apparatus using a self-circulating pump. The modified solution is returned to a modified solution preparation tank. After separation, the upper layer is recovered as a modified solvent for reuse, while the lower layer flows into a second return tank. A neutralizing agent is introduced into the second return tank to neutralize the acidic substances in the solution. Finally, the waste liquid is sent to a distillation column using a first pump for recycling.

[0050] S9. Drying: After modification, nitrogen gas is introduced into the aerogel roll preparation tank and / or aerogel sheet preparation box. The gel substrate is dried under normal pressure in a nitrogen atmosphere at 60°C to obtain the silicon-based aerogel material.

[0051] The principle of atmospheric pressure drying is to reduce capillary forces by solvent replacement and surface modification, thereby preventing the gel from shrinking and collapsing during the drying process.

[0052] The performance parameters of the aerogel roll and aerogel sheet prepared in Example 1 are shown in Table 1.

[0053] Table 1 Performance parameters of silicon-based aerogel material in Example 1

[0054]

[0055] This invention enables the drying and production of silicon-based aerogels under low or normal pressure conditions. These conditions are easily controlled, safer, and reduce equipment investment. Furthermore, the system used in this invention allows for the recycling of key auxiliary materials such as organic solvents, water, and inert gases, significantly reducing raw material costs. The overall process is simple and reliable, producing products with excellent quality indicators, and is suitable for large-scale industrial production.

[0056] The method described in this invention can be implemented using the following equipment system, with the specific structure as follows.

[0057] See Figure 1 This invention provides a system for preparing silicon-based aerogel materials by atmospheric pressure drying, comprising a sol mixer 1, an impregnation tank 2, and a heat preservation device 3. A first conveying device 4 is disposed below the sol mixer 1, directly opposite the outlet of the sol mixer 2. The output end of the first conveying device 4 is connected to the impregnation tank 2. The impregnation tank 2 is adjacent to a second conveying device 5. The heat preservation device 3 is disposed on the second conveying device 5. A roll forming machine 6 and / or a sheet transport vehicle 7 are disposed at the output end of the second conveying device 5. The first conveying device 4 and the second conveying device 5 are high-temperature resistant belt conveyors.

[0058] See Figure 2 The system also includes a processing system for post-processing the roll / sheet material. This processing system comprises an aerogel roll material preparation tank 8 and / or an aerogel sheet preparation box 9, a modified solution preparation tank 10, a first unloading tank 11, a second unloading tank 12, and a distillation column 13. The aerogel roll material preparation tank 8 and / or the aerogel sheet preparation box 9 are connected to water, alcohol, and inert gas delivery units via pipes and three-way valves, and are also connected to the modified solution preparation tank 10 via pipes. The aerogel roll material preparation tank 8 is equipped with a first heating device 14 for heat preservation. The first heating device 14 is wrapped around the outside of the aerogel roll material preparation tank 8 and can be a jacketed or coiled type. The aerogel sheet preparation box 9 is equipped with a second heating device 15 for heat preservation. The second heating device 15 is located at the bottom inner side of the aerogel sheet preparation box 9 and can be a jacketed or coiled type. The aerogel roll preparation tank 8 and the aerogel sheet preparation box 9 are respectively connected to a first self-circulating pump 16 and a second self-circulating pump 17 via self-circulating pipes.

[0059] The outlets of the aerogel roll material preparation tank 8 and the aerogel sheet material preparation box 9 are sequentially connected to the first unloading tank 11, the second unloading tank 12, and the distillation column 13 via pipes; the outlet of the distillation column 13 is connected to the aerogel roll material preparation tank 8 and the aerogel sheet material preparation box 9 via pipes respectively. A first liquid pump 23 is provided between the second unloading tank 12 and the distillation column 13.

[0060] Furthermore, the aerogel roll preparation tank 8 is a vertical tank structure. The aerogel sheet preparation box 9 is a box structure that can accommodate a mobile sheet transport vehicle 7. The aerogel sheet preparation box 9 is equipped with a quick-opening door 24 at the entrance for the sheet transport vehicle 7 to enter and exit, allowing the aerogel sheet transport vehicle 7 to drive into the aerogel sheet preparation box 9 through the quick-opening door 24.

[0061] To improve work efficiency, hoisting mechanisms 18 are respectively provided above the impregnation tank 2 and the aerogel roll preparation tank 8.

[0062] The outlets of the aerogel roll preparation tank 8 and the aerogel sheet preparation box 9 are sequentially connected to a first condensing device 19 and a second condensing device 20 via pipelines. The outlet of the second condensing device 20 is connected to an inert gas conveying unit. The outlets of both the first condensing device 19 and the second condensing device 20 are connected to the modified solution preparation tank 10. During the drying process using the method of this invention, the generated waste gas flows sequentially through the first condensing device 19 and the second condensing device 20 into the modified solution preparation tank 10 and the inert gas conveying unit for recycling. Specifically, the primary condensation control temperature is 0~80℃; the secondary condensation control temperature is -30~0℃.

[0063] In practice, the pipeline can be used simultaneously as a liquid inlet and a gas inlet, and the outlet can be used simultaneously as a gas outlet and a liquid outlet. Each pipeline is equipped with a three-way valve, which can be adjusted as needed.

[0064] The modified solution preparation tank 10 is equipped with a stirrer 21, which can be a paddle stirrer or an anchor stirrer.

[0065] In practice, the inlets of the first discharge tank 11, the second discharge tank 12, and the modified solution preparation tank 10 are all equipped with inlet valves to facilitate control of the waste liquid flow. A cooling device 22 is fitted around the outside of the first discharge tank 11; the cooling device 22 is either a jacketed type or a coil type. When cooling is required, a cooling medium can be introduced into the jacket or the coil.

[0066] Example 2

[0067] This embodiment provides a method for producing silicon-based aerogel materials by atmospheric pressure drying, which is mainly the same as in Embodiment 1, except that:

[0068] 1. Preparation of coating solution: Mix 25wt% sodium silicate and 30wt% sulfuric acid at a volume ratio of 5:1 until homogeneous, control the mixing temperature at 50℃ and the mixing time at 6min.

[0069] 2. Immersion and gelation: The coated substrate is completely immersed in the coating solution prepared in step 1 and soaked at 50°C for 5 minutes. After removal, it is gelled at 50°C for 1 hour.

[0070] 3. The gelled substrate is washed four times with water and alcohol solutions at 50°C to remove impurities such as sodium salts from the gel.

[0071] 4. The cleaned gel substrate is placed in the modification solution for modification. The modification treatment temperature is 50℃ and the modification treatment time is 4h. The modification solution is prepared by mixing the modifier (dimethyldichlorosilane) and the modifying solvent (hexamethyldisiloxane) in a mass ratio of 5:90.

[0072] 5. The modified gel substrate is dried at 120°C and nitrogen atmosphere under normal pressure to obtain the silicon-based aerogel material.

[0073] The performance parameters of the aerogel roll and aerogel sheet prepared in Example 2 are shown in Table 2.

[0074] Table 2 Performance parameters of silicon-based aerogel material in Example 2

[0075]

[0076] Example 3

[0077] This embodiment provides a method for producing silicon-based aerogel materials by atmospheric pressure drying, which is mainly the same as in Embodiment 1, except that:

[0078] 1. Preparation of coating solution: Mix 50wt% sodium silicate and 50wt% sulfuric acid at a volume ratio of 6:1 until homogeneous. Control the mixing temperature at 80℃ and the mixing time at 10min to obtain the coating solution.

[0079] 2. Immersion and gelation: The coated substrate is completely immersed in the coating solution prepared in step 1 and soaked at 80°C for 6 minutes. After removal, it is gelled at 60°C for 0.5 hours.

[0080] 3. The gelled substrate is washed five times with water and alcohol solutions at 65°C to remove impurities.

[0081] 4. The cleaned gel substrate is placed in the modification solution for modification. The modification treatment temperature is 55℃ and the modification treatment time is 6h. The modification solution is prepared by mixing the modifier (trimethylchlorosilane) and the modifying solvent (n-hexane) in a mass ratio of 10:90.

[0082] 5. The modified gel substrate is dried at 160°C and nitrogen atmosphere under normal pressure to obtain the silicon-based aerogel material.

[0083] The performance parameters of the aerogel roll and aerogel sheet prepared in Example 3 are shown in Table 3.

[0084] Table 3 Performance parameters of silicon-based aerogel material in Example 3

[0085]

[0086] In summary, the method of this invention enables the drying and production of silicon-based aerogels under low or normal pressure conditions. These conditions are easy to control, safer, and reduce equipment investment. Furthermore, the apparatus of this invention allows for the recycling of key auxiliary materials such as organic solvents, water, and inert gases, reducing raw material costs. The overall process is simple and reliable, producing high-quality products suitable for large-scale industrial production.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for producing silicon-based aerogel materials by atmospheric pressure drying, characterized in that, Includes the following steps: S1. Coating: Sodium silicate and sulfuric acid are mixed evenly in a certain proportion to obtain a coating solution; and the coating solution is used to coat the substrate. S2, Immersion: The coated substrate is immersed in an immersion tank containing the coating solution. S3, Gel: Gel treatment is performed on the substrate after S2 treatment; S4. Preparation of roll / sheet materials: The gelled substrate is made into roll materials or kept as gelled sheets; S5. Water washing: Place the roll / sheet material obtained in S4 into the aerogel roll material preparation tank and / or aerogel sheet material preparation box, wash with water, and use a self-circulating pump to circulate and wash the gel substrate in the aerogel roll material preparation tank and / or aerogel sheet material preparation box. S6. Alcohol washing: After water washing, an alcohol solution is introduced into the aerogel roll material preparation tank and / or aerogel sheet material preparation box for alcohol washing, and the alcohol solution is circulated and washed on the gel substrate using a self-circulating pump. S7. Modification: After alcohol washing, the modification solution is introduced into the aerogel roll material preparation tank and / or aerogel sheet material preparation box to modify the gel substrate; wherein, the modification solution is prepared by mixing the modifier and the modifying solvent in a mass ratio of 1~10:90~99; S8. Drying: After modification, inert gas is introduced into the aerogel roll preparation tank and / or aerogel sheet preparation box, and the gel substrate is dried at normal pressure at 70~150℃ to obtain silicon-based aerogel material. In step S5, the wastewater after cleaning is discharged into the first return tank, and a neutralizing agent is added to the first return tank to neutralize the acidic substances in the water. A cooling medium is then introduced into the cooling device to control the temperature at 5~15℃. After the solids in the aqueous solution are precipitated, the water is recovered and reused. In step S6, the cleaned wastewater alcohol solution is transferred from the first return tank to the second return tank, and then the waste liquid is transported to the distillation column using the first pump. The operating pressure of the distillation column is controlled at -10~50 kPa; the top temperature of the column is controlled at 30~90℃; and the bottom temperature of the column is controlled at 70~150℃. The alcohol in the mixed solution is recovered and reused. In step S7, the modified solution is returned to the modified solution preparation tank. After separation, the upper layer is recovered as a modified solvent for reuse. The lower layer flows into the second return tank, and a neutralizing agent is introduced into the second return tank to neutralize the acidic substances in the solution. Then, the waste liquid is sent to the distillation column by the first pump for recycling.

2. The method for producing silicon-based aerogel materials by atmospheric pressure drying according to claim 1, characterized in that, The coating solution of S1 is obtained by thoroughly mixing 5%~50wt% sodium silicate and 10%~50wt% sulfuric acid at a volume ratio of 3~6:

1.

3. The method for producing silicon-based aerogel materials by atmospheric pressure drying according to claim 1, characterized in that, S2 involves soaking at 30-80℃ for 3-6 minutes and then removing the sample; S3 involves gelling at 30-60℃ for 0.5-1 hour.

4. The method for producing silicon-based aerogel materials by atmospheric pressure drying according to claim 1, characterized in that, S5 and S6 involve washing the gelled substrate with water and alcohol solutions 3 to 5 times at 30 to 65°C.

5. The method for producing silicon-based aerogel materials by atmospheric pressure drying according to claim 1, characterized in that, S7 involves immersing the cleaned gel substrate in a modification solution for modification. The modification temperature is 45-60℃, and the modification time is 2-6 hours.

6. The method for producing silicon-based aerogel materials by atmospheric pressure drying according to claim 1, characterized in that, In S7, the modifier is any one of trimethylchlorosilane, dimethyldichlorosilane, and trimethylmethoxysilane, and the modifying solvent is any one of hexamethyldisiloxane, n-hexane, and n-heptane.

Images