Elastic silicon dioxide aerogel material as well as preparation method and application thereof

Abstract

The invention discloses an elastic silicon dioxide aerogel material and a preparation method and application thereof, and relates to the field of aerogel materials.The preparation method comprises the following steps that a silicon source is added into a mixed solution of alcohol acidified by glacial acetic acid, water and N, N-dimethylformamide for a hydrolysis reaction, and sol is obtained; placing the sol above a pyridine-containing ammonia water mixed solution, and carrying out fumigation treatment to obtain a gel body; the gel is subjected to aging treatment, normal hexane replacement solvent treatment and drying, and the elastic silicon dioxide aerogel material is obtained. Compared with an existing preparation process of silicon dioxide aerogel, the preparation method has the advantages that a proper amount of pyridine is introduced into alkali liquor, and the mode is further adjusted into a fumigation treatment mode, so that the mechanical properties such as the maximum compression strain capacity and the maximum compressive strength of the elastic silicon dioxide aerogel material are remarkably improved; in addition, the elastic silicon dioxide aerogel material has excellent adsorption performance on gases such as carbon dioxide and the like, and is wide in application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerogel materials, in particular to an elastic silica aerogel material and a preparation method and application thereof. BACKGROUND

[0002] Aerogel is a kind of solid material with unique three-dimensional nano-porous network structure, which is formed by mutual aggregation of colloidal particles or polymer molecules, has high porosity, and the pore size is generally in the range of nanometers to microns. This unique structure endows aerogel with many excellent properties, and shows great application potential in many fields such as aerospace, building energy saving, environmental protection, energy storage, etc. Among them, silica aerogel, as an important member of the aerogel family, is one of the most widely and deeply studied aerogel materials. It inherits the general characteristics of aerogel materials with silica as the skeleton structure, and further expands its application range due to the good chemical stability and thermal stability of silica itself.

[0003] Although silica aerogel has many excellent properties, poor mechanical properties have been one of the key problems restricting its large-scale application. Traditional silica aerogel usually presents brittleness, low maximum compressive strain and maximum compressive strength, and is easy to break and collapse when subjected to external force, so it cannot meet the use requirements of fields with high requirements for material mechanical properties. SUMMARY

[0004] To solve the above problems, the present application provides an elastic silica aerogel material and a preparation method and application thereof.

[0005] In a first aspect, the present application provides a preparation method of an elastic silica aerogel material, as shown in the following formula: Figure 1 The preparation method comprises the following steps:

[0006] adding a silicon source into an acidified alcohol, water and N,N-dimethylformamide mixed solution to carry out a hydrolysis reaction, to obtain a sol body;

[0007] placing the sol body above an ammonia water mixed solution containing pyridine to carry out a fumigation treatment, to obtain a gel body;

[0008] carrying out an aging treatment, a n-hexane solvent replacement treatment and drying on the gel body, to obtain the elastic silica aerogel material;

[0009] The molar concentration M1 of pyridine in the ammonia water mixed solution containing pyridine and the molar concentration M2 of ammonia in the ammonia water mixed solution containing pyridine satisfy the following relationship: 1.5≤M2 / M1≤2.3.

[0010] Further, the molar ratio of the silicon source, the glacial acetic acid, the alcohol, the water and the N,N-dimethylformamide is 1: (0.55-0.70): (6.5-8.0): (8.0-10.0): (0.70-0.85).

[0011] Further, the silicon source comprises methyltrimethoxysilane, and the alcohol comprises ethanol.

[0012] Further, the working condition parameter of the hydrolysis reaction comprises a temperature of 24-28℃ and a time of 7.5-8.5h.

[0013] Further, the step of placing the sol in the pyridine-containing ammonia water mixed solution to obtain the gel comprises the following process:

[0014] The sol is placed at a distance of 4-6cm above the liquid surface of the pyridine-containing ammonia water mixed solution, the pyridine-containing ammonia water mixed solution is heated to 98-103℃ to realize vaporization in a closed environment, and the gel is obtained after the fumigation treatment for 30-60min and then transferred to a constant-temperature environment of 40-50℃ for standing for 1-2h.

[0015] Further, the molar concentration of pyridine in the pyridine-containing ammonia water mixed solution is 3.0-4.0mol / L, and the molar concentration of ammonia in the pyridine-containing ammonia water mixed solution is 5-8.5mol / L.

[0016] Further, the value of M2 / M1 is 2.

[0017] Further, the working condition parameter of the aging treatment comprises a temperature of 58-65℃ and a time of ≥48h.

[0018] In a second aspect, based on the same inventive concept, the present application provides an elastic silica aerogel material, which is prepared by the preparation method of the first aspect.

[0019] In a third aspect, based on the same inventive concept, the present application provides the application of the elastic silica aerogel material of the second aspect in greenhouse gas adsorption treatment, energy-saving buildings, aerospace thermal insulation, environmental protection and new energy systems.

[0020] Compared with the prior art, the above technical solution provided by the embodiments of the present application has at least the following advantages:

[0021] The embodiment of the present application provides a kind of elastic silica aerogel material and its preparation method and application, compared with the preparation process of existing silica aerogel, the present application is mainly by introducing appropriate pyridine in lye, and further adjustment is smoked and steamed processing mode, significantly improve the maximum compressive strain of elastic silica aerogel material, maximum compressive strength and other mechanical properties;In addition, the elastic silica aerogel material shows excellent adsorption performance to carbon dioxide and other gases, and has wide application prospect.Specifically:

[0022] Hydrolysis stage: the silicon source (such as methyltrimethoxysilane) is subjected to acid hydrolysis in an alcohol / acetic acid acidified water / DMF mixed solution to generate Si-OH active monomers and preliminarily form a sol.

[0023] Polycondensation and gelation: the mixed solution of ammonia containing pyridine is subjected to fumigation and steaming treatment, and under the synergistic catalysis of pyridine-ammonia, the Si-OH polycondensation is triggered to form a Si-O-Si three-dimensional network in an alkaline environment; in addition, pyridine can adjust the local pH value and inhibit phase separation caused by local overalkalization, and its aromatic ring structure can stabilize the gel skeleton through π-π interaction. Compared with the traditional direct soaking or rapid direct mixing and other alkaline liquid direct contact treatment methods, the present application adopts a gas phase mass transfer method to slowly penetrate the alkaline substance, which is more gentle in kinetics, avoids the gel inhomogeneity caused by concentration gradient in the traditional soaking method, and thus improves the comprehensive performance of the elastic silica aerogel material. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows, and obviously, other drawings can also be obtained by those skilled in the art without creative labor under the premise of these drawings.

[0026] Figure 1 The flow chart of the preparation method of the elastic silica aerogel material provided in the embodiments of the present application. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods, such as silicon sources and solvents. Furthermore, unless otherwise specified or detailed, the steps and parameters involved, such as aging treatment, hexane replacement solvent treatment, and drying, can be performed according to the existing technology's disclosed process steps and parameters for preparing elastic silica aerogel materials, or directly using existing equipment according to the instruction manual. These will not be elaborated upon further in this invention document.

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0030] Example 1

[0031] This example provides an elastic silica aerogel material, the preparation method of which includes the following steps:

[0032] Step (1): Methyltrimethoxysilane was added to a mixed solution of ethanol, water and N,N-dimethylformamide acidified with glacial acetic acid and hydrolyzed at room temperature (25°C) for 8.0 h to obtain a sol; wherein the molar ratio of methyltrimethoxysilane, glacial acetic acid, ethanol, water and N,N-dimethylformamide was 1:0.65:7.2:9.5:0.8;

[0033] Step (2): Place the sol obtained in step (1) 5 cm above the surface of the pyridine-containing ammonia solution; in a closed environment, heat the pyridine-containing ammonia solution to 100°C to achieve vaporization, fumigate for 45 min, and then transfer it to a constant temperature environment of 45°C for 1.5 h to obtain a gel; wherein, the molar concentration of pyridine M1 in the pyridine-containing ammonia solution is 3.5 mol / L and the molar concentration of ammonia M2 in the pyridine-containing ammonia solution is 7.0 mol / L, satisfying the following relationship: M2 / M1=2.0;

[0034] Step (3): The gel obtained in step (2) is aged in an ethanol solution at an aging temperature of 60°C for 72 hours. After aging, the ethanol solvent is replaced with n-hexane for 24 hours, and the n-hexane is replaced every 6 hours. Finally, the gel is dried at 35°C for 2 hours, at 55°C for 5 hours, and at 100°C for 24 hours to obtain an elastic silica aerogel material.

[0035] Example 2

[0036] This example provides an elastic silica aerogel material and its preparation method, which differs from Example 1 only in that:

[0037] (1) The molar concentration of pyridine in the pyridine-containing ammonia solution M1 is 4.0 mol / L and the molar concentration of ammonia in the pyridine-containing ammonia solution M2 is 6.0 mol / L, which satisfies the following relationship: M2 / M1=1.5.

[0038] Example 3

[0039] This example provides an elastic silica aerogel material and its preparation method, which differs from Example 1 only in that:

[0040] (1) The molar concentration of pyridine M1 in the pyridine-containing ammonia water mixed solution is 3.5 mol / L and the molar concentration of ammonia M2 in the pyridine-containing ammonia water mixed solution is 8.05 mol / L, which satisfies the following relationship: M2 / M1=2.3.

[0041] Comparative Example 1

[0042] This example provides an elastic silica aerogel material and its preparation method, which differs from Example 1 only in that:

[0043] (1) The molar concentration of pyridine M1 in the pyridine-containing ammonia water mixed solution is 3.5 mol / L and the molar concentration of ammonia M2 in the pyridine-containing ammonia water mixed solution is 2.8 mol / L, which satisfies the following relationship: M2 / M1=0.8.

[0044] Comparative Example 2

[0045] This example provides an elastic silica aerogel material and its preparation method, which differs from Example 1 only in that:

[0046] (1) The molar concentration of pyridine M1 in the pyridine-containing ammonia water mixed solution is 2.0 mol / L and the molar concentration of ammonia M2 in the pyridine-containing ammonia water mixed solution is 7.0 mol / L, which satisfies the following relationship: M2 / M1=3.5.

[0047] Comparative Example 3

[0048] This example provides a traditional elastic silica aerogel material with methyltrimethoxysilane as the silicon source and its preparation method, which differs from Example 1 only in that:

[0049] (1) Step (2) is adjusted to the traditional alkaline treatment method, specifically: slowly add 10 mol / L ammonia solution to the sol obtained in step (1) to adjust the pH to 6, and then transfer it to a constant temperature environment of 45℃ for standing for 1.5 h to obtain a gel.

[0050] Test Example 1

[0051] This example demonstrates the mechanical property testing of the elastic silica aerogel materials obtained in the above embodiments and comparative examples. The testing method is as follows: A universal testing machine was used to test the compression-rebound characteristics and the maximum compressive stress that the material can withstand. The indenter descent speed was 0.2 mm / min, the inlet force was 0.2 N, and the surface of the test sample needed to be flat. The formula for calculating the maximum compressive strength is: σ = F / S; where F is the maximum compressive stress (N) that the elastic aerogel can withstand under maximum compressive strain, and S is the surface area (cm²) of the sample under pressure. 2 σ represents the maximum compressive strength that the test sample can withstand.

[0052] The test results are shown in Table 1.

[0053] Table 1

[0054] Test sample Maximum compressive strain (%) Maximum compressive strength (MPa) Example 1 65 0.163 Example 2 51 0.128 Example 3 58 0.150 Comparative Example 1 42 0.067 Comparative Example 2 46 0.079 Comparative Example 3 38 0.055

[0055] As shown in Table 1:

[0056] 1) Compared with comparative examples 1 to 3, the maximum compressive strain and maximum compressive strength of the elastic silica aerogel materials provided in Examples 1 to 3 of the present invention are better, indicating that the present invention can significantly improve the comprehensive mechanical properties of silica aerogel materials by introducing an appropriate amount of pyridine into the alkaline solution and further adjusting it to a fumigation treatment method.

[0057] 2) By comparing and analyzing the test results of Comparative Example 1, Comparative Example 2 and Example 1, it is shown that if the concentration of ammonia is too low (such as when M2 / M1=0.8 in Comparative Example 1) or the concentration of pyridine is too low (such as when M2 / M1=3.5 in Comparative Example 2), the gelation effect will be affected, resulting in the inability to form a complete gel network, damaging the network stability and reducing the strength of the silica aerogel material.

[0058] Test Example 2

[0059] This example demonstrates the dynamic adsorption performance of the elastic silica aerogel material obtained in the above embodiments for carbon dioxide. The test method is as follows: 0.3 g of the prepared elastic silica aerogel material was packed into an adsorption column. Before testing, the sample was pretreated in a high-purity nitrogen adsorption bed at 150°C and a flow rate of 100 ml / min. The dynamic adsorption conditions for carbon dioxide were as follows: temperature 25°C, test atmosphere of 10% (v / v) CO2 and 90% (v / v) N2, with 1% water vapor introduced into the adsorbed gas, and a gas flow rate of 30 ml / min. The composition of the gas after passing through the adsorption column was measured by gas chromatography to obtain the corresponding breakthrough curve. The dynamic adsorption capacity (mmol / g) of the elastic silica aerogel material at 25°C can be calculated from the breakthrough curve.

[0060] The test results are shown in Table 2.

[0061] Table 2

[0062] Test sample Dynamic adsorption capacity (mmol / g) Example 1 6.2 Example 2 5.3 Example 3 5.6

[0063] As shown in Table 2, the elastic silica aerogel material provided in the embodiments of the present invention exhibits excellent adsorption performance for gases such as carbon dioxide, with a maximum dynamic adsorption capacity of 6.2 mmol / g.

[0064] In summary, the embodiments of the present invention provide an elastic silica aerogel material, its preparation method, and its application. Compared with the existing silica aerogel preparation process, the present invention mainly improves the mechanical properties of the elastic silica aerogel material, such as maximum compressive strain and maximum compressive strength, by introducing an appropriate amount of pyridine into the alkaline solution and further adjusting it to a fumigation treatment method. In addition, the elastic silica aerogel material exhibits excellent adsorption performance for gases such as carbon dioxide, and has broad application prospects.

[0065] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0066] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing an elastic silica aerogel material, characterized in that, The preparation method includes the following steps: A silicon source was added to a mixed solution of alcohol, water, and N,N-dimethylformamide acidified with glacial acetic acid for hydrolysis to obtain a sol. The sol was placed above a mixture of ammonia and pyridine for fumigation treatment to obtain a gel. The gel was subjected to aging treatment, hexane replacement solvent treatment, and drying to obtain the elastic silica aerogel material. The molar concentrations of pyridine (M1) and ammonia (M2) in the pyridine-containing ammonia solution satisfy the following relationship: 1.5 ≤ M2 / M1 ≤ 2.

3.

2. The method for preparing the elastic silica aerogel material according to claim 1, characterized in that, The molar ratio of the silicon source, the glacial acetic acid, the alcohol, the water, and the N,N-dimethylformamide is 1:(0.55~0.70):(6.5~8.0):(8.0~10.0):(0.70~0.85).

3. The method for preparing the elastic silica aerogel material according to claim 2, characterized in that, The silicon source includes methyltrimethoxysilane, and the alcohol includes ethanol.

4. The method for preparing the elastic silica aerogel material according to claim 1, characterized in that, The operating conditions for the hydrolysis reaction include: a temperature of 24~28℃ and a time of 7.5~8.5h.

5. The method for preparing the elastic silica aerogel material according to claim 1, characterized in that, The step of fumigating the sol above a pyridine-containing ammonia solution to obtain a gel includes the following process: The sol is placed 4-6 cm above the surface of the pyridine-containing ammonia solution. In a sealed environment, the pyridine-containing ammonia solution is heated to 98-103°C to achieve vaporization. After fumigation for 30-60 minutes, it is transferred to a constant temperature environment of 40-50°C and left to stand for 1-2 hours to obtain the gel.

6. The method for preparing the elastic silica aerogel material according to claim 5, characterized in that, The molar concentration of pyridine in the pyridine-containing ammonia solution is 3.0~4.0 mol / L, and the molar concentration of ammonia in the pyridine-containing ammonia solution is 5~8.5 mol / L.

7. The method for preparing the elastic silica aerogel material according to claim 5, characterized in that, The value of M2 / M1 is 2.

8. The method for preparing the elastic silica aerogel material according to claim 1, characterized in that, The working conditions for the aging treatment include: temperature of 58~65℃ and time of ≥48h.

9. An elastic silica aerogel material, characterized in that, The elastic silica aerogel material is prepared by any one of claims 1 to 8.

10. The application of the elastic silica aerogel material according to claim 9 in greenhouse gas adsorption and treatment, energy-saving buildings, aerospace insulation, environmental protection and new energy systems.

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