Preparation method of low-thermal-conductivity silicon dioxide aerogel powder based on bio-based surfactant
By using a two-step acid-base catalytic method with bio-based surfactants and the universal silicon source TEOS, the problem of low biodegradability of traditional surfactants is solved, and high-performance low thermal conductivity silica aerogel powder is prepared, which is suitable for food and medical fields, simplifies the process and reduces costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI CONCH IND TECHNOLOGY RESEARCH INSTITUTE CO LTD
- Filing Date
- 2026-01-28
- Publication Date
- 2026-04-14
AI Technical Summary
In existing technologies, traditional surfactants have low biodegradability and pose a risk of residue. They are difficult to meet the environmental and safety requirements of food, medical and other scenarios that have high requirements in terms of both product performance regulation and process stability. In addition, the selection of raw materials is limited and the density range fluctuates greatly.
Bio-based surfactants such as octyl glucoside, sodium N-lauroyl sarcosinate, and soybean lecithin are used in combination with the universal silicon source TEOS. Stable interactions are formed in a two-step acid-base catalytic method through precise pH control, avoiding surfactant residue, simplifying the preparation process, and avoiding time-consuming modification steps.
It has been realized that high-performance, low thermal conductivity silica aerogel powder can be prepared under normal pressure, which meets the safety requirements of food, medical and other fields, simplifies the process, reduces environmental pressure and production costs, and the product performance is better than or equal to that of traditional processes.
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Figure CN121849979A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of porous materials technology, specifically relating to a method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants. Background Technology
[0002] In existing technologies, low thermal conductivity silica aerogel powder is prepared using a two-step acid-base catalytic sol-gel method. By adding cationic surfactants to the formulation and adjusting the water-to-alcohol ratio, hydrophobic or hydrophilic aerogels can be directly obtained by drying under normal pressure, thus eliminating the need for a separate modification step. However, traditional surfactants have low biodegradability and pose a risk of residue, making them unsuitable for applications with high environmental and safety requirements, such as food and medical applications. Furthermore, existing methods heavily rely on specific silicon sources, limiting raw material selection. If an inappropriate surfactant is chosen, the density range of the resulting product will fluctuate significantly, posing challenges to performance control and process stability. Summary of the Invention
[0003] The purpose of this invention is to provide a method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants, so as to solve the technical problem in the prior art that it is difficult to avoid low biodegradation rate of surfactants and residual risks while taking into account both product performance control and process stability.
[0004] The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants includes the following steps: S1. Preparation of precursor: Add silicon source and bio-based surfactant to solvent composed of ethanol and distilled water, and stir evenly under constant temperature until a homogeneous mixed solution is formed to complete the preparation of precursor. S2, Acid-catalyzed hydrolysis: Acidic catalyst is gradually added dropwise to the mixed solution obtained in step S1 to adjust the pH value of the mixed solution to acidic. The mixture is stirred continuously at a constant temperature until the hydrolysis of the silicon source is completed. S3, Alkali-catalyzed gelation and aging: Alkali catalyst is gradually added dropwise to the solution after hydrolysis in step S2 to adjust the pH of the mixed solution to alkaline. The solution is then allowed to stand to gel and age, resulting in an aged wet gel. S4. Solvent replacement and aging treatment: Add ethanol replacement agent to the wet gel after aging in step S3, completely immerse the gel, and place the resulting material system in an oven for aging treatment to obtain the treated gel. S5. Drying under normal pressure: The gel treated in step S4 is dried under normal pressure and temperature to obtain silica aerogel powder.
[0005] Preferably, the bio-based surfactant is any one of octyl glucoside, sodium N-lauroyl sarcosinate, and soybean lecithin.
[0006] Preferably, the silicon source is tetraethyl orthosilicate.
[0007] Preferably, the molar ratio of ethanol to distilled water in the solvent is 0.9:1 to 1.2:1.
[0008] Preferably, in step S1, the volume ratio of the silicon source to the mass of the bio-based surfactant is 20 ml: 0.25-4 g.
[0009] Preferably, in step S2, the pH value of the mixed solution is adjusted to 2.5-3.5, and in step S3, the pH value of the hydrolyzed solution is adjusted to 8.5-9.5.
[0010] Preferably, in step S2, the acidic catalyst is a hydrochloric acid solution; in step S3, the alkaline catalyst is ammonia.
[0011] Preferably, in step S4, the temperature inside the oven is 40-60℃, and the aging treatment time is 4-8 hours.
[0012] Preferably, in steps S1 and S2, the temperature of the constant temperature environment is 50°C, the stirring time in step S1 is 20-40 minutes, and the stirring time in step S2 is 40-60 minutes.
[0013] The technical advantages of this invention are as follows: This invention uses a universal silicon source, TEOS, combined with a feasible bio-based surfactant. After precise pH control, specific functional groups of the bio-based surfactant (such as glycosyl, amino acid, and phospholipid groups) form a stable interaction with the TEOS hydrolysis products under precise pH control. This overcomes the limitations of existing knowledge regarding the preparation of low thermal conductivity silica aerogel powder using a two-step acid-base catalytic method with bio-based surfactants. Silica aerogel powder with satisfactory performance can be obtained without a specific silicon source or supercritical equipment. This solves the technical problem of existing technologies struggling to balance product performance control and process stability while avoiding the risk of surfactant residue due to low biodegradation rates.
[0014] Meanwhile, this method avoids time-consuming surface modification steps and the use of related solvents during the preparation process, reducing environmental pressure and production costs, and meeting the stringent safety requirements of food, medical and other fields. Attached Figure Description
[0015] Figure 1 This is a water contact angle test diagram of the silica aerogel powder prepared in Example 1 of the present invention.
[0016] Figure 2 The thermal conductivity test diagram is shown for the silica aerogel powder prepared in Example 1 of this invention.
[0017] Figure 3 This is a physical image of the silica aerogel powder prepared in Example 1 of the present invention.
[0018] Figure 4 The images show electron micrographs comparing the product obtained in Example 1 of the present invention with the product obtained in Comparative Example 1 (left: octyl glucoside system of Example 1 of the present invention, right: CTAB system of Comparative Example 1).
[0019] Figure 5 This is a comparison chart of the biodegradability rates of the products in each embodiment of the present invention and the comparative product. Detailed Implementation
[0020] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.
[0021] like Figures 1-5 As shown, the present invention provides a method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants, comprising the following steps.
[0022] S1. Preparation of precursor: Add silicon source and bio-based surfactant to solvent composed of ethanol and distilled water, and stir evenly under constant temperature until a homogeneous mixed solution is formed to complete the preparation of precursor.
[0023] In this step, the silicon source is tetraethyl orthosilicate (TEOS), the bio-based surfactant is any one of octyl glucoside (APG-0810), sodium N-lauroyl sarcosinate (SLS), and soybean lecithin, and the molar ratio of ethanol to distilled water in the solvent is 0.9:1-1.2:1.
[0024] The temperature of the constant temperature environment is 50℃, and the stirring time is 20-40 minutes.
[0025] S2, Acid-catalyzed hydrolysis: Acidic catalyst is gradually added dropwise to the mixed solution obtained in step S1 to adjust the pH value of the mixed solution to acidic. The solution is stirred continuously at a constant temperature until the hydrolysis of the silicon source is completed.
[0026] In this step, the acidic catalyst is a hydrochloric acid solution.
[0027] The pH of the mixed solution was adjusted to 2.5-3.5, the temperature of the constant temperature environment was 50℃, and the stirring time was 40-60 minutes.
[0028] S3, Alkali-catalyzed gelation and aging: Alkali catalyst is gradually added dropwise to the solution after hydrolysis in step S2 to adjust the pH of the mixed solution to alkaline. The solution is then allowed to stand to gel and age, resulting in an aged wet gel.
[0029] In this step, ammonia is used as the alkaline catalyst.
[0030] The pH of the solution after hydrolysis is adjusted to 8.5-9.5. Stirring can be used to accelerate mixing during the addition of alkaline catalyst, but stirring should also be stopped when the addition stops.
[0031] S4. Solvent replacement and aging treatment: Add ethanol replacement agent to the wet gel after aging in step S3 to completely immerse the gel. The resulting material system is placed in an oven for aging treatment to obtain the treated gel.
[0032] In this step, the temperature inside the oven is 40-60℃, and the aging treatment time is 4-8 hours, which can effectively strengthen the gel network structure.
[0033] S5. Drying under normal pressure: The gel treated in step S4 is dried under normal pressure and temperature to obtain silica aerogel powder.
[0034] In this step, the solvent should be completely removed by drying.
[0035] This invention achieves precise matching of the molecular chain length, hydrophilic / hydrophobic group ratio, and acid-base catalytic timing of bio-based surfactants, enabling them to self-assemble into a gradient structure with an inner hydrophobic core and an outer hydrophilic core in an ethanol-water mixture. The hydrophobic core locks the pores of the gel network, while the hydrophilic outer layer reduces the interfacial tension between the solvent and the gel, thus synergistically resisting capillary stress. In contrast, traditional surfactants (such as CTAB), although amphiphilic, have rigid molecular structures and cannot form a uniform gradient structure under these process conditions. They can only alleviate stress through physical filling (see effect verification for comparative data).
[0036] At the same time, while simplifying the process and improving environmental friendliness, the core properties (such as thermal conductivity and specific surface area) of the aerogel powder prepared by this invention are better than or equal to those of traditional processes, and its process stability is also similar to that of existing technologies.
[0037] The specific implementation of this solution is as follows.
[0038] Example 1.
[0039] S1. Take 14 ml of ethanol (anhydrous ethanol) and 9 ml of distilled water in a beaker and mix them well (the molar ratio of ethanol to distilled water is 1:1), with a total volume of 28 ml.
[0040] Add 20 ml of tetraethyl orthosilicate (TEOS) and 0.3 g of octyl glucoside (APG-0810) to the above mixed solvent.
[0041] Place the beaker in a 50°C constant temperature water bath and stir magnetically at 500 rpm for 30 minutes until the solution is evenly mixed.
[0042] S2. Slowly add a 1 mol / L hydrochloric acid solution to the mixed solution using a dropper, while monitoring with a pH meter, until the pH value of the solution stabilizes at 3. Maintain a constant temperature of 50°C and continue stirring for 50 minutes.
[0043] S3. Slowly add a 0.5 mol / L ammonia solution to the system obtained in the previous step to adjust the pH of the solution to 9. Stop stirring. At this point, you can observe that the solution gradually forms a transparent wet gel after standing for several minutes. Let the solution stand and age for 1 hour.
[0044] S4. Add sufficient anhydrous ethanol to the formed wet gel to replace it, ensuring that the gel is completely submerged.
[0045] The entire system was placed in a 45°C forced-air drying oven and aged for 6 hours.
[0046] S5. After aging, the sample is taken out and dried at room temperature and pressure. After about 10 hours, a white and fluffy silica aerogel powder can be obtained.
[0047] The silica aerogel powder prepared in this embodiment is an aerogel powder for food cold chain insulation coating, and uses a glycosyl bio-based surfactant.
[0048] Example 2.
[0049] S1. Take 15ml of ethanol (anhydrous ethanol) and 8ml of distilled water in a beaker and mix them well (the molar ratio of ethanol to distilled water is 1.2:1), with a total volume of 28ml.
[0050] Add 20 ml of tetraethyl orthosilicate (TEOS) and 0.25 g of sodium N-lauroyl sarcosinate (SLS) to the above mixed solvent.
[0051] Place the beaker in a 50°C constant temperature water bath and stir magnetically at 500 rpm for 25 minutes until the solution is evenly mixed.
[0052] S2. Slowly add a 1 mol / L hydrochloric acid solution to the mixed solution using a dropper, while monitoring with a pH meter, until the pH value of the solution stabilizes at 2.5. Maintain a constant temperature of 50°C and continue stirring for 45 minutes.
[0053] S3. Slowly add a 0.5 mol / L ammonia solution to the system obtained in the previous step to adjust the pH of the solution to 8.5. Stop stirring. At this point, you can observe that the solution gradually forms a transparent wet gel after standing for several minutes. Allow the solution to stand and age for 1.5 hours.
[0054] S4. Add sufficient anhydrous ethanol to the formed wet gel to replace it, ensuring that the gel is completely submerged.
[0055] The entire system was placed in a 50°C forced-air drying oven and aged for 5 hours.
[0056] S5. After aging, the sample is taken out and dried at room temperature and pressure. After about 11 hours, a white and fluffy silica aerogel powder can be obtained.
[0057] The silica aerogel powder prepared in this embodiment is an aerogel powder for heat dissipation and buffering materials of electronic devices, and uses an amino acid-based bio-based surfactant.
[0058] Example 3.
[0059] S1. Take 13ml of ethanol (anhydrous ethanol) and 10ml of distilled water in a beaker and mix them well (the molar ratio of ethanol to distilled water is 0.9:1), with a total volume of 28ml.
[0060] Add 20 ml of tetraethyl orthosilicate (TEOS) and 0.4 g of soybean lecithin to the above mixed solvent.
[0061] Place the beaker in a 50°C constant temperature water bath and stir magnetically at 500 rpm for 35 minutes until the solution is evenly mixed.
[0062] S2. Slowly add a 1 mol / L hydrochloric acid solution to the mixed solution using a dropper, while monitoring with a pH meter, until the pH value of the solution stabilizes at 3.5. Maintain a constant temperature of 50°C and continue stirring for 55 minutes.
[0063] S3. Slowly add a 0.5 mol / L ammonia solution to the system obtained in the previous step to adjust the pH of the solution to 9.5. Stop stirring. At this point, you can observe that the solution gradually forms a transparent wet gel after standing for several minutes. Let the solution stand for 2 hours to age.
[0064] S4. Add sufficient anhydrous ethanol to the formed wet gel to replace it, ensuring that the gel is completely submerged.
[0065] The entire system was placed in a 55°C forced-air drying oven and aged for 4 hours.
[0066] S5. After aging, the sample is taken out and dried at room temperature and pressure. After about 9 hours, a white and fluffy silica aerogel powder can be obtained.
[0067] The silica aerogel powder prepared in this embodiment is an aerogel powder for the heat insulation layer of medical protective clothing, and uses a phospholipid-based bio-based surfactant.
[0068] As a comparative example, the applicant also conducted the following experiments.
[0069] Comparative Example 1 (original CTAB system, to verify the difference in surfactants).
[0070] The original technical solution was adopted: the silicon source was TEOS, with a dosage of 20 ml; the surfactant was CTAB, with a dosage of 0.3 g; the solvent was a mixed solvent of ethanol and distilled water in a molar ratio of 1:1; the pH after acid catalysis was 3; the pH after alkali catalysis was 9; and the remaining process steps were the same as in Example 1. The product was obtained after drying at room temperature and pressure.
[0071] Comparative Example 2 (using traditional modification process to verify the advantages of process simplification).
[0072] Using a conventional method, after gelation, the resulting gel underwent multiple solvent exchanges and silane coupling agent surface modification over a period of up to 48 hours, followed by atmospheric pressure drying to obtain the product. The raw materials and other process steps used were the same as in Example 1.
[0073] Comparative Example 3 (using non-adaptive bio-based surfactants to verify the innovativeness of the selection).
[0074] Sodium dodecyl sulfate (SDS), a bio-based surfactant, was used to replace the octyl glucoside of the present invention. Other process steps and raw materials were the same as in Example 1. The product was obtained after drying at room temperature and pressure.
[0075] Performance verification: Performance tests were conducted on the products obtained in Examples 1-3 and Comparative Examples 1-3 of this invention, and the results are shown in the table below: Table 1: Performance Comparison Table of Products from Examples 1-3 and Comparative Examples 1-3 of the Present Invention
[0076] Structural innovation verification: The water contact angle test results (102°-108°) and immersion stability of Examples 1-3 prove the formation of the "internal hydrophobic and external hydrophilic" gradient structure. Although Comparative Example 1 (CTAB system) has a hydrophobic surface (92°), it partially disintegrates after immersion. Comparative Example 3 (non-adapted bio-based surfactant) cannot form a stable structure, which confirms that the synergistic effect of the bio-based surfactant selected in this invention and the process system is the key to forming the target structure.
[0077] Performance advantage verification: The product of this invention is significantly superior to traditional surfactant systems in terms of biodegradability (>95% vs 30%), harmful substance residue (not detected vs 0.8-1.2 mg / kg), and scene adaptability. Moreover, the preparation cycle is significantly shortened compared to Comparative Example 2 (from 3 days to less than 24 hours), proving that the application of bio-based surfactants not only solves environmental protection problems, but also achieves synergistic optimization of process and performance.
[0078] Mechanism support verification: Through the comparison of Comparative Example 3, it is confirmed that the selection of bio-based surfactants (molecular structure, functional group characteristics) and their compatibility with the reaction system are the core technologies. SDS cannot form a stable gradient structure due to the mismatch between the molecular chain length and the acid-base catalytic system, and the product partially collapses.
[0079] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.
Claims
1. A method for preparing a low thermal conductivity silica aerogel powder based on a bio-based surfactant, characterized in that, Includes the following steps: S1. Preparation of precursor: Add silicon source and bio-based surfactant to a solvent composed of ethanol and distilled water, and stir uniformly at a constant temperature until a homogeneous mixed solution is formed, thus completing the preparation of the precursor; S2. Acid-catalyzed hydrolysis: Gradually add an acidic catalyst to the mixed solution obtained in step S1 to adjust the pH value of the mixed solution to acidic, and continue stirring at a constant temperature until the hydrolysis of silicon source is completed; S3. Alkali-catalyzed gelation and aging: Gradually add an alkaline catalyst to the solution after hydrolysis in step S2 to adjust the pH value of the mixed solution to alkaline, and allow it to stand to gel and age, obtaining an aged wet gel; S4. Solvent replacement and aging treatment: Add an ethanol replacement agent to the aged wet gel in step S3 to completely immerse the gel, and place the resulting material system in an oven for aging treatment to obtain the treated gel; S5. Drying at normal pressure: Dry the gel treated in step S4 at normal pressure and temperature to obtain silica aerogel powder.
2. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, The bio-based surfactant is any one of octyl glucoside, sodium N-lauroyl sarcosinate, or soybean lecithin.
3. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, The silicon source is tetraethyl orthosilicate.
4. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, The molar ratio of ethanol to distilled water in the solvent is 0.9:1 to 1.2:
1.
5. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactant according to claim 1, wherein in step S1, the volume ratio of the silicon source to the mass of the bio-based surfactant is 20 ml: 0.25-4 g.
6. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, In step S2, the pH of the mixed solution is adjusted to 2.5-3.5, and in step S3, the pH of the hydrolyzed solution is adjusted to 8.5-9.
5.
7. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, In step S2, the acidic catalyst is hydrochloric acid solution; in step S3, the alkaline catalyst is ammonia water.
8. The method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, In step S4, the temperature inside the oven is 40-60℃, and the aging treatment time is 4-8 hours.
9. A method for preparing low thermal conductivity silica aerogel powder based on bio-based surfactants according to claim 1, characterized in that, In steps S1 and S2, the temperature of the constant temperature environment is 50℃. The stirring time in step S1 is 20-40 minutes, and the stirring time in step S2 is 40-60 minutes.