Methods for producing aerogels and aerogel slurries, and aerogels and slurries produced thereby

Abstract

The present invention relates to methods for producing aerogels and aerogel slurries, and the aerogels and slurries produced thereby. More particularly, the present invention relates to environmentally friendly methods for producing aerogels and aerogel slurries that utilize carbon dioxide as a reactant and consume it during the process.

Description

[Technical Field]

[0001] The present invention relates to methods for producing aerogels and aerogel slurries, and the aerogels and slurries produced thereby. More particularly, the present invention relates to environmentally friendly methods for producing aerogels and aerogel slurries that utilize carbon dioxide as a reactant and consume it during the process. [Background technology]

[0002] Aerogels are porous materials with high specific surface areas and have a wide range of commercial applications in diverse fields such as construction, thermal insulation, catalysis, and drug delivery. For example, aerogels can be used as aggregates in cement applications to reduce weight and provide insulation, while aerogel slurries can be used as building primers or water-repellent coats for various applications.

[0003] Traditionally, aerogels are prepared by a sol-gel process to obtain a three-dimensional 'wet-gel' structure, followed by a solvent exchange step in which the original sol-gel solvent within the pores of the wet gel is replaced with a dry solvent. In a final step, drying is performed to obtain a porous aerogel structure. Aerogel slurries are typically prepared from the porous aerogel. For example, following the preparation of the aerogel by the manufacturing methods described above, the porous aerogel is prepared by mixing it with an infiltrating binder (i.e., the wet gel (WG) becomes the aerogel (A) and the aerogel slurry (AS)).

[0004] Traditional aerogel manufacturing methods are environmentally challenging, often resulting in CO2 and air pollutant emissions and / or the use of hazardous volatile organic compounds (VOCs) or acids. For example, supercritical drying requires the infusion of large amounts of CO2 into the aerogel. Ambient drying techniques release large amounts of VOCs, and even those employing aqueous drying solvents (Han et al., Bioinspired Synthesis of Monolithic and Layered Aerogels, Advanced Materials: 2018, 30 (23)) release CO2 as a by-product. These drawbacks mean that aerogel manufacturing is limited to skilled technicians and can only be performed in environments with established safety procedures for handling hazardous materials.

[0005] A method for producing silica aerogels using CO2 as a gelling agent has been reported (Wu et al., Silica Aerogels formed from Soluble Silicates and Methyltrimethoxysilane (MTMS) using CO2 gas as a gelation agent, Ceramics International: 2018, 44, 821-829). In this method, sodium silicate (water glass), CO2 2、 and water react to form silica wet gel. However, the by-product sodium carbonate is removed by washing with water, so the CO2 is not used as part of the aerogel product, but is removed as a wastewater discharge.

[0006] A more environmentally friendly method for producing aerogel has been reported by Plank et al. (Plank et al., Preparation and Characterization of a Calcium Carbonate Aerogel, Research Letters in Materials Science: 2009, 1-3). However, this method uses supercritical drying, which has the drawbacks mentioned above, and the resulting calcium carbonate aerogel has lower refractoriness, lower porosity, and higher density than conventional silica aerogel.

[0007] The present invention aims to avoid or mitigate one or more of the drawbacks of the prior art. Environmentally friendly methods for producing aerogels and aerogel slurries would be useful, as would methods that could achieve an overall reduction in CO2 emissions, or even net-zero CO2 emissions. Flexible manufacturing methods that reduce processing or drying times and / or can be performed at ambient temperature would be particularly beneficial. Direct methods for producing aerogel slurries that avoid the need to prepare and incorporate finished aerogel into a slurry would also be useful. Methods that avoid the need for hazardous chemicals, do not require specialized equipment, and / or can be performed in a non-laboratory environment would be useful. Summary of the Invention

[0008] The present invention relates to methods for producing aerogels and aerogel slurries, as well as the aerogels and slurries produced thereby. The preparation of both aerogels and aerogel slurries by the inventive manufacturing methods consumes CO as a reactant and retains CO in the resulting aerogel and aerogel slurry products. This offers significant environmental advantages over prior art manufacturing methods, which typically emit CO. In embodiments, the present invention provides a direct route to preparing aerogel slurries from wet gels (i.e., AS from WG). Advantageously, the inventive manufacturing methods avoid the use of toxic, volatile organic solvents or strong acids, providing a simple, energy-efficient, and environmentally friendly method for preparing both aerogels and aerogel slurries. In certain aspects, the methods do not use volatile or hazardous liquid chemicals and do not require specialized equipment, allowing them to be carried out in a typical work environment or outside of a laboratory.

[0009] The present invention therefore relates to a method for producing a silica or alumina wet gel for use in preparing an aerogel or an aerogel slurry, the method comprising: providing a precursor solution comprising an alkylsilane and / or a metal alkoxide; and reacting the precursor solution in the presence of a sol-gel solvent to form a reaction mixture; and adding a gelling agent to the reaction mixture to form a wet gel; and the gelling agent is an alkaline earth metal oxide solid.

[0010] Thus, in a first aspect of the present invention there is provided a method for preparing a silica or alumina wet gel for the production of an aerogel or aerogel slurry, the method comprising: providing a precursor solution comprising an alkylsilane and / or a metal alkoxide; and reacting the precursor solution in the presence of a sol-gel solvent to form a reaction mixture having a pH of 3 to 9; Adding a gelling agent to the reaction mixture to form a wet gel wherein the gelling agent is an alkaline earth metal oxide solid.

[0011] The gelling agent is added in the solid form of an alkaline earth metal oxide, ie, is not formed in situ.

[0012] The pH of the reaction mixture is 3 to 9. This production method does not use an acid. In one embodiment, the reaction mixture does not contain an acid. Advantageously, this production method can avoid the use of acids, particularly strong acids, which have traditionally been considered necessary when preparing silica gel.

[0013] In one embodiment, the pH of the reaction mixture is 3-7.

[0014] In one embodiment, the pH of the reaction mixture is 4-9.

[0015] In one embodiment, the pH of the reaction mixture is 4.5-9.

[0016] In one embodiment, the pH of the reaction mixture is from 5 to 8.75.

[0017] The wet gel comprises a gel framework of silicon dioxide (silica) or alumina and an alkaline earth metal hydrate solution containing alkaline earth metal hydroxide.

[0018] The alkaline earth metal solids may be selected from calcium oxide, magnesium oxide, barium oxide and strontium oxide.

[0019] In one embodiment, the alkaline earth metal solid is calcium oxide.

[0020] In one embodiment, the alkaline earth metal solid is added to the reaction mixture at a molar concentration of 0.002M to 195M.

[0021] In one embodiment, the alkaline earth metal solid is added to the reaction mixture at a molar concentration of 0.002M to 20M.

[0022] In one embodiment, alkaline earth metal solids are added to the reaction mixture at a molar concentration of 0.01M to 2M.

[0023] In one embodiment, the precursor solution comprises an alkylsilane.

[0024] The alkylsilane may be selected from triethoxymethylsilane (MTES) and trimethoxymethylsilane (MTMS). Mixtures of alkylsilanes may also be used.

[0025] In one embodiment, the alkylsilane is triethoxymethylsilane (MTES).

[0026] In one embodiment, the precursor solution comprises a metal alkoxide.

[0027] The metal alkoxide may be selected from tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), polyethoxydisiloxane (PEDS) and aluminum tri-sec-butoxide. Mixtures of metal alkoxides may also be used.

[0028] In one embodiment, the precursor solution includes an alkylsilane and a metal alkoxide.

[0029] In one embodiment, the metal alkoxide is a liquid.

[0030] In one embodiment, the sol-gel solvent comprises an alcohol.

[0031] Suitable alcohols are known to those skilled in the art and include, but are not limited to, C1-C4 alcohols, ethanol, methanol, propanol, and butanol.

[0032] In one embodiment, the sol-gel solvent is a mixture of water and alcohol.

[0033] In one embodiment, the sol-gel solvent is a mixture of carbonated water and alcohol.

[0034] In one embodiment, the alcohol is ethanol, preferably bioethanol. "Bioethanol" refers to ethanol produced in an environmentally friendly manner by fermentation of biomass, such as plant by-products containing sugar and starch components.

[0035] In one embodiment, the molar ratio of water or carbonated water to alcohol in the sol-gel solvent is within the range of 100:1 to 1:100, 50:1 to 1:50, or 20:1 to 1:20, or 10:1 to 1:10, or 5:1 to 1:5.

[0036] The method of manufacture involves reacting a precursor solution in the presence of a sol-gel solvent. When the precursor solution is reacted in the presence of a sol-gel solvent, the precursor:sol-gel solvent molar ratio can be in the range of 100:1 to 1:100, 50:1 to 1:50, or 20:1 to 1:20. In one embodiment, the ratio is 10:1 to 1:10, or 1:4 to 1:10.

[0037] The inventors have advantageously demonstrated that when alkaline earth metal oxide solids are used as gelling agents, wet gels are produced that include a gel framework of silicon dioxide (silica) or alumina and an alkaline earth metal hydrate solution. The excess alkaline earth metal oxide solids, along with their alkaline earth metal hydroxide products, react with carbon dioxide to produce the corresponding alkaline earth metal carbonates, which are ultimately retained in the aerogel or aerogel slurry product. Advantageously, unlike other methods that use CO (e.g., as reported by Wu et al., in which CO is used as a gelling agent and then released as a by-product), in the process of the present invention, the alkaline earth metal oxide and hydroxide products in the wet gel react with and consume CO, which is retained in the final aerogel and aerogel slurry product in the carbonate form. This represents a net consumption of CO in the preparation of aerogels and aerogel slurries, which offers significant environmental benefits when using atmospheric CO. For example, if CaO is used as the alkaline earth metal solid, one mole of CO2 will be trapped by one mole of CaO, resulting in one mole of CaCO3, which is retained or trapped in the final aerogel or aerogel slurry product. CO2 can be introduced before gelation (e.g., by adding carbonated water to the reaction mixture, as part of the sol-gel solvent, or otherwise) and / or after gelation (e.g., in an aging step).

[0038] In a first aspect, the wet gel prepared by the method of the present invention can be used in the production of an aerogel or an aerogel slurry.

[0039] When a wet gel is used to make the aerogel slurry, the method of making may include mixing the wet gel to form a slurry mixture.

[0040] Mixing of the wet gel can be accomplished by any suitable means, such as by breaking up the gel with a spoon or stirrer, by mechanical means, or by other suitable means apparent to one skilled in the art. As will be appreciated by those skilled in the art, a mixing step is not required, but mixing the wet gel breaks up the gel and exposes more surface area for further reaction to occur.

[0041] In one embodiment, the method of manufacture includes adding a desiccant, and optionally water, to a slurry mixture.

[0042] In one embodiment, the desiccant may be an alkaline earth metal oxide. The alkaline earth metal oxide solid used as the desiccant may be the same as the alkaline earth metal oxide solid used as the gelling agent. However, this is not necessary, and in embodiments, different alkaline earth metal solids may be used. This may be advantageous to impart desired properties to the resulting aerogel product.

[0043] In one embodiment, the desiccant is an alkaline earth metal solid selected from calcium oxide, magnesium oxide, barium oxide, and strontium oxide.

[0044] Advantageously, the alkaline earth metal oxide solids react exothermically with water within the pores of the wet gel in the slurry mixture, self-heating the slurry and accelerating drying. Additional water can be added if necessary or desired to maximize the exothermic reaction and shorten drying times. Residual water can be absorbed by the hydroxide by-product.

[0045] In one embodiment, the desiccant is calcium oxide.

[0046] The desiccant can be added at a molar concentration of 0.016 to 162.114 M relative to the wet gel.

[0047] The desiccant can be added at a molar concentration of 0.016 to 35M relative to the wet gel.

[0048] The desiccant can be added at a molar concentration of 0.016 to 20M relative to the wet gel.

[0049] In one embodiment, the method further comprises introducing carbonated water to the reaction mixture and / or introducing carbon dioxide to the wet gel or wet or dry slurry mixture to form an aerogel or aerogel slurry.

[0050] In one embodiment, the step of introducing carbon dioxide into the wet gel, or wet or dry slurry mixture comprises introducing CO 2 gas or exposing the wet gel or slurry mixture to atmospheric CO 2 .

[0051] In one embodiment, carbon dioxide gas is introduced into the wet gel or slurry mixture. High-purity or industrial-grade CO can be used; i.e., CO can be introduced into the wet gel or slurry mixture from a cylinder or similar suitable means. Advantageously, CO can be obtained from the atmosphere. In this embodiment, the wet gel or slurry mixture can be aged by exposure to the atmosphere. In an embodiment, aging is carried out at ambient temperature and pressure. During aging, CO reacts with the alkaline earth metal hydroxide to form the corresponding carbonate, which is trapped within the pores of the aerogel, as well as within the pores of the aerogel slurry and around the silica framework.

[0052] In one embodiment, CO2 in carbonated water or CO2 added to the wet gel or slurry mixture reacts with the alkaline earth metal hydroxide to produce carbonate, which is retained within the aerogel or aerogel slurry.

[0053] In one embodiment, when producing an aerogel, the production method further comprises drying the wet gel or aged wet gel to form an aerogel. In one embodiment, the production method comprises one or more drying steps. The drying step can be carried out by conventional means, such as in an oven or on a heated plate. Suitable heating methods will be apparent to those skilled in the art. In one embodiment, the drying step can be selected from subcritical drying, ambient pressure drying (or atmospheric pressure drying), supercritical drying, and freeze drying. Subcritical and ambient pressure drying techniques may be preferred due to their reduced environmental impact.

[0054] In one embodiment, the drying step comprises heating under ambient pressure.

[0055] The heating may be carried out at a temperature of 60 to 500°C. In one embodiment, the heating is carried out at a temperature of 60 to 150°C.

[0056] Since the boiling point of the liquid phase is below 100°C, a temperature of about 100°C (eg, 80°C to 120°C) may be preferred.

[0057] The drying step may be carried out for 15 minutes to 24 hours. As will be understood by those skilled in the art, the length of the drying step depends on the heating temperature, with lower temperatures requiring longer drying times. In one embodiment, the drying step is carried out for 15 minutes to 12 hours, or 15 minutes to 6 hours. In one embodiment, the drying step is carried out for 20 minutes to 3 hours, or 30 minutes to 2 hours. When the drying temperature is 60°C to 150°C, the drying time may be 30 minutes to 12 hours, 30 minutes to 8 hours, 30 minutes to 6 hours, or 30 minutes to 2 hours.

[0058] If the aerogel slurry has undergone a drying step prior to aging with CO, the aerogel slurry product does not need to undergo a separate drying step, however, as will be explained in more detail below, dried slurry products may exhibit different water absorption characteristics, and therefore a subsequent drying step may be performed if desired.

[0059] In one embodiment of the present invention, aerogels may be prepared using fibers, thereby enabling the production of fiber-reinforced products. In these embodiments, the fibers can be added during the wet-gel formation process, i.e., by adding the fibers during the reaction of the precursor solution in the presence of a sol-gel solvent and adding a gelling agent. Alternatively, or in addition, the fibers can be added at a later stage, for example, during mixing of the wet-gel into a slurry. Suitable fibers for use in the manufacturing methods of the present invention include ceramic fibers, organic fibers, carbon fibers, and glass fibers.

[0060] In one embodiment, the fibers are ceramic fibers. TM Ceramic chopped fibers are an example of a fiber that can be used. In one embodiment, the fiber is fiberglass. 6 mm fiberglass strands are another example of a fiber that can be used. Those skilled in the art will understand that these examples are illustrative and that other fibers can be used.

[0061] Advantageously, when fibers are used, the manufacturing method of the present invention allows for the rapid production of reinforced aerogel or aerogel slurry composites, the term composite being used to describe aerogels having one or more additional elements, such as fibers, that may be incorporated into the aerogel structure. [Brief explanation of the drawings]

[0062] The present invention will now be described by way of example only with reference to the accompanying figures, in which: FIG. 1 shows a reaction scheme for preparing an aerogel according to one embodiment of the present invention. FIG. 2 shows a reaction scheme for preparing an aerogel slurry according to one embodiment of the present invention. FIG. 3 shows the elasticity test of the aerogel prepared in Example 1.2. FIG. 4 shows the results of X-ray diffraction performed on the aerogel prepared in Example 1.2. Figure 5 shows an SEM image of the aerogel prepared in Example 1.2. FIG. 6 shows the aerogel slurry (after drying) prepared in Example 3.2. FIG. 7 shows the results of X-ray diffraction performed on the aerogel slurry (after drying) prepared in Example 3.2. FIG. 8 shows an SEM image of the aerogel slurry (after drying) prepared in Example 1.2. FIG. 9 shows a photograph of the aerogel prepared in Example 2. FIG. 10 shows a photograph of the fiber-reinforced aerogel prepared in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0063] One embodiment of the present invention will be described in detail with reference to FIG. 1. FIG. 1 is a schematic diagram illustrating the production of an aerogel according to the present invention. In FIG. 1, a wet oxide gel is obtained by a sol-gel process using a precursor and a solvent. The precursor is an alkylsilane, a metal alkoxide, or a mixture thereof. The sol-gel solvent is a mixture of alcohol and water, for example, bioethanol and water. In some embodiments, CO2 can be introduced in this process, for example, in the form of carbonated water. The carbonated water may constitute part of the sol-gel solvent. No acid is used in the reaction mixture, and the pH of the mixture is in the range of 4 to 9.

[0064] As shown in Figure 1, the wet-gel reaction results in the formation of a wet oxide gel comprising an oxide gel framework and an alkaline earth metal hydrate solution. Both during the sol-gel process and after the formation of the wet oxide gel, the alkaline earth metal solid (e.g., calcium oxide in Figure 1) and its hydroxide product (e.g., calcium hydroxide in Figure 1) capture carbon dioxide and react with it to produce an alkaline earth metal carbonate, e.g., calcium carbonate in Figure 1. One mole of CaO captures one mole of CO2 and produces one mole of CaCO3. The CO2 can be high-purity or industrial-grade CO2, such as introduced from a cylinder, or preferably from the atmosphere to which the reaction is exposed.

[0065] The carbonates formed are trapped within the pores of the aerogel, meaning that CO2 is consumed during the process and, unlike conventional methods, is retained within the aerogel rather than released. This has significant environmental benefits, allowing the method to function as a carbon capture and utilization process. The method can be used as a direct air capture technology for atmospheric CO2. The aerogel can then be dried to the final aerogel product using any of the conventional drying methods, including atmospheric drying, subcritical drying, supercritical drying, or freeze drying.

[0066] Therefore, the process can be summarized as follows: TIFF2025539025000002.tif40122

[0067] In the above scheme, CO2 is introduced into the system during the aging step, where it reacts with the alkaline earth metal oxides and their hydroxide products in the wet gel to produce carbonates, which are retained in the final aerogel product and the final aerogel slurry product. However, alternatively or additionally, CO2 can be introduced prior to the gelation step, for example, by introducing carbonated water into the reaction mixture. When carbonated water is introduced into the reaction mixture, it can be used, for example, in the sol-gel solvent.

[0068] One embodiment of the present invention using a wet gel in the preparation of an aerogel slurry is described below with reference to FIG. 2. In FIG. 2, a wet oxide gel is obtained by a sol-gel process carried out using precursors and solvents in a manner similar to that described in FIG. 1. The precursors are alkylsilanes, metal alkoxides, or mixtures thereof. The sol-gel solvent is a mixture of alcohol and water, such as bioethanol and water (alternatively, carbonated water can again be used). The reaction mixture is acid-free and has a pH of 4-9.

[0069] The wet-gel reaction produces a wet oxide gel containing an oxide gel framework and an alkaline earth metal hydrate solution (Figure 2). An alkaline earth metal oxide solid is then added to the resulting wet oxide gel to act as a desiccant. The alkaline earth metal oxide solid reacts exothermically with the water in the pores of the wet oxide gel, which can self-heat the slurry mixture and accelerate drying. If necessary or desired, additional water can be added to maximize the exothermic reaction and shorten drying times. Residual water can be absorbed by the hydroxide by-product.

[0070] The alkaline earth metal solids (e.g., calcium oxide in Figure 2) and their hydroxide products (calcium hydroxide in Figure 2) in the slurry mixture capture carbon dioxide and react to produce the corresponding alkaline earth metal carbonates (e.g., calcium carbonate in Figure 2). The CO2 can be high-purity or industrial-grade CO2, e.g., from a cylinder, or, preferably, CO2 from the atmosphere to which the reaction is exposed. The resulting carbonates are captured within the pores of the slurry and around the silica framework. This means that CO2 is consumed during the process and, unlike prior art methods, is retained in the final product without being released. This has significant environmental advantages. Furthermore, this method allows for the direct preparation of aerogel slurries. That is, it allows for the direct preparation of aerogel slurries (AS) from wet gels (WG) without the need to prepare the aerogel product and then mix it with a wet binder. This has important advantages in terms of commercialization and scale-up. The wet slurry can be used directly in coating applications, such as primers.

[0071] Alternatively, it can be dried and used in the form of a dried slurry. If drying is required, the aerogel slurry may be dried using known techniques, such as atmospheric drying, subcritical drying, supercritical drying, freeze drying, etc. For environmental benefits, an optional drying step at ambient pressure (or atmospheric pressure) and ambient temperature (or ambient temperature) may be preferred.

[0072] Therefore, the process can be summarized as follows: TIFF2025539025000003.tif55123

[0073] In the above scheme, when CO2 is introduced into the system during the aging step, it reacts with the alkaline earth metal oxides and their hydroxide products in the wet gel to form carbonates that are retained in the final aerogel product and the final aerogel slurry product. However, alternatively or additionally, CO2 can be introduced prior to the gelation step, for example, by introducing carbonated water into the reaction mixture. When carbonated water is introduced into the reaction mixture, it can be used in the sol-gel solvent.

[0074] The preparation of the present invention will now be illustrated by examples, which are intended to be illustrative only.

[0075] Example material Methyltriethoxysilane (MTES 99%) was purchased from Hubei Co-Formula Material Tech Co., Ltd (China). Bioethanol (ethanol, 96.6%) was purchased from Bioethanol Fireplace (UK). Calcium oxide (CaO, 99%) was purchased from Minerals Water (UK). Carbon dioxide (CO2, 100%) was purchased from AUTOart (UK). Carbonated water was purchased from Aqua Vale. TM Sparkling Spring Water was used.

[0076] method pH was measured directly using a Vleoak pH meter with a high accuracy of 0.01 and a measuring range of 0-14.

[0077] Example 1: 1.1 Preparation of wet gel MTES was used as a precursor and mixed with a sol-gel solvent consisting of bioethanol and water at a molar ratio of 1:8:22. The pH of the reaction mixture was measured and found to be 8.75. CaO powder was added as a gelling agent to the precursor mixture at a molar concentration of 0.016 M.

[0078] 1.2 Preparation of aerogel from wet gel The silica wet gel prepared in Example 1.1 was aged in CO gas by covering the container containing the wet gel with plastic wrap and blowing CO gas into the container from a cylinder. The aging was carried out for 7 days.

[0079] Finally, the aged wet gel was directly dried in a sealed container at 100 °C for 2 h to obtain silica aerogel.

[0080] Based on the fact that 1 mol of CaO captures 1 mol of CO2, the amount of CO2 captured in this method was theoretically estimated to be 0.013 g of CO2 per gram of silica aerogel produced.

[0081] 1.3 Aerogel characterization 1.3.1 The bulk density of the aerogel of Example 1.2 was calculated by dividing the measured weight by the measured volume and was found to be 0.08 g / cm 3 This is what happened.

[0082] The porosity of the aerogel was calculated from the bulk density using the following formula: Porosity = (1 - (bulk density / theoretical density)) x 100 As a result, the porosity was 96%.

[0083] The flexibility of the aerogel was confirmed by manual compression, as shown in Figure 3.

[0084] The hydrophobicity of the aerogel was measured using open-source analysis (Stalder et al., "Low-Bond Axisymmetric Drop Shape Analysis for Surface Tension and Contact Angle Measurements of Sessile Drops," Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2010), and the product exhibited a contact angle of 141°.

[0085] X-ray diffraction of the aerogel was performed using an Empyrean Powder XRD with a scan rate of 1.3° / min and a step width of 0.02° using Cu radiation. The results, shown in Figure 4, indicate that the aerogel product contains amorphous silica gel as the main component, with the peak at 29.5° indicating calcium carbonate (CaCO).

[0086] SEM observations were performed using a Zeiss 500 scanning electron microscope with a field emission gun, imaging the samples in high vacuum mode at an accelerating voltage of 5 keV. To enhance electrical conductivity, all samples were gold-coated prior to SEM observation. The results, shown in Figure 5, reveal a clear nanoporous structure composed of a silica framework.

[0087] Example 2 2.1 Preparation of wet gel MTES was used as a precursor and mixed with a sol-gel solvent consisting of MTES, bioethanol, and carbonated water (pH 4.6) at a molar ratio of 1:8:22. The pH of the reaction mixture was measured and found to be 5.14. CaO powder was added as a gelling agent to the precursor mixture at a molar concentration of 0.016 M.

[0088] 2.2 Preparation of aerogel from wet gel The silica wet gel prepared in Example 2.1 was aged in CO gas by covering the container containing the wet gel with plastic wrap and blowing CO gas into the container from a cylinder. The aging was carried out for 7 days.

[0089] Finally, the aged wet gel was directly dried in a sealed container at 100 °C for 2 h to obtain silica aerogel.

[0090] Based on the fact that 1 mol of CaO captures 1 mol of CO2, the amount of CO2 captured in this method was theoretically estimated to be 0.013 g of CO2 per gram of silica aerogel produced.

[0091] 2.3 Aerogel characterization 2.3.1 The bulk density of the aerogel of Example 2.2 was calculated by dividing the measured weight by the measured volume and was found to be 0.089 g / cm 3 This is what happened.

[0092] Example 3 3.1 Preparation of wet gel MTES was used as a precursor and mixed with a sol-gel solvent consisting of MTES, bioethanol, and water in a molar ratio of 1:8:22. The pH of the reaction mixture was measured and found to be 8.75. CaO powder was added as a gelling agent to the precursor mixture at a molar concentration of 0.016 M.

[0093] 3.2 Preparation of aerogel slurry directly from wet gel (WG to AS): The resulting silica wet gel was mixed to break down the gel structure and form a slurry. It was then mixed with 5.9 g of CaO as a desiccant. Here, both the desiccant properties of CaO and the exothermic reaction between CaO and water accelerated the drying process and dried the internal pores. After mixing with CaO, the outer surface of the slurry began to warm (a 2–5°C increase). After 1 hour, the external temperature of the slurry returned to ambient temperature, and the slurry became partially dry but still appeared moist. After completing the mixing process with the alkaline earth metal solid as a desiccant, the container containing the dried slurry mixture was covered with plastic wrap and an aging process was performed by blowing CO2 from a cylinder into the container. The aging process was carried out for 7 days, at which point an aerogel slurry was obtained without further drying.

[0094] In this example, the aging step was carried out after the internal pores had dried to obtain a partially dried slurry, however, as one skilled in the art will appreciate, the aging step can begin at any time after addition of the alkaline earth metal solid desiccant.

[0095] Based on the fact that 1 mol of CaO captures 1 mol of CO2, the amount of CO2 captured during the process was theoretically calculated to be 1.56 g per gram of silica aerogel slurry produced.

[0096] 3.3 Characterization of aerogel slurry To perform wet gel characterization, the slurry was first dried in air at ambient pressure and temperature for 14 days without additional heating.

[0097] The bulk density of the dried aerogel slurry of Example 3.2 was calculated by dividing the measured weight by the measured volume and was found to be 0.04 g / cm 3 This is what happened.

[0098] The porosity of the aerogel was calculated from the bulk density using the following formula: Porosity = (1 - (bulk density / theoretical density)) x 100 As a result, the porosity was 85%.

[0099] Figure 6 is a photograph showing the external structure of the dried slurry. The dried slurry exhibited a monolithic nature, i.e., it was found to be porous with a biscuit-like texture. The monolithic nature indicates that the resulting calcium carbonate acts as a binder in the aerogel slurry.

[0100] The hydrophilicity of the aerogel was measured using open-source analysis (Stalder et al., "Low-Bond Axisymmetric Drop Shape Analysis for Surface Tension and Contact Angle Measurements of Sessile Drops," Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2010), and the product exhibited a contact angle of 80°.

[0101] X-ray diffraction was performed using an Empyrean Powder XRD with a scan rate of 1.3° / min and a step width of 0.02° using Cu radiation. The results, shown in Figure 7, indicate that the aerogel product contains amorphous silica gel and that calcium carbonate (CaCO3) is present as the major component along with the amorphous silica gel.

[0102] SEM observations were performed using a Zeiss 500 scanning electron microscope with a field emission gun, imaging the samples in high vacuum mode at an accelerating voltage of 5 keV. To enhance electrical conductivity, all samples were gold-coated prior to SEM observation. The results, shown in Figure 8, demonstrate the formation of nanoporous microstructures, implicating the formation of calcium carbonate in the resulting structure. The method of the present invention can be used to prepare silica or alumina wet gels for use in preparing aerogels or aerogel slurries. This method has many advantages, particularly its CO2 consumption, which is highly beneficial from an environmental perspective. This method avoids the use of volatile chemicals, does not require specialized equipment, and can be used in domestic and commercial environments, such as homes and construction sites, for in-situ primer preparation. In embodiments, this method can be used to prepare aerogel slurries directly from wet gels (i.e., WG to AS), eliminating the need to prepare an aerogel intermediate and then mix it with a wet binder.

[0103] Example 4 4.1 Preparation of wet gel MTES was used as a precursor and mixed with a sol-gel solvent consisting of bioethanol and water in a molar ratio of 1:8:22. The pH of the reaction mixture was measured and found to be 8.75. CaO powder (1.6 g) was added to the precursor mixture as a gelling agent at a molar concentration of 0.016 M. Additionally, 2.36 g of short ceramic fibers (Triton TM Kaowol Epsilon Ceramic Fiber, Pure, Fisher Chemical TM ) was added.

[0104] 4.2 Preparation of aerogel from wet gel The fiber-reinforced silica wet gel prepared in Example 4.1 was aged in CO gas by covering the container containing the wet gel with plastic wrap and blowing CO gas into the container from a cylinder. The aging was carried out for 7 days.

[0105] Finally, the aged fiber-reinforced wet gel was directly dried in a sealed container at 100 °C for 2 h to obtain a fiber-reinforced silica aerogel.

[0106] Based on the fact that 1 mol of CaO captures 1 mol of CO2, the amount of CO2 captured in this method was theoretically estimated to be 0.013 g of CO2 per gram of fiber-reinforced silica aerogel produced.

[0107] All features and / or steps of any method or process disclosed in this specification (including the accompanying claims, abstract, and drawings) may be combined in any combination, except where at least some of the features and / or steps are mutually exclusive. Each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each disclosed feature is only an example of a generic series of equivalent or similar features. The invention is not limited to the details of the foregoing embodiments. The invention also extends to any novel, or any novel combination of, features disclosed in this specification (including the accompanying claims, abstract, and drawings), or any novel, or any novel combination of steps of the disclosed methods or processes.

[0108] With respect to the use of plural and / or singular forms herein, those skilled in the art will be able to translate from plural to singular and vice versa as appropriate depending on the context and / or appropriateness. For clarity, various singular / plural combinations may be expressly stated.

[0109] Those skilled in the art will understand that the terms used in this specification, and particularly in the appended claims, are generally intended to be "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," "having" should be interpreted as "having at least," "includes" should be interpreted as "includes but is not limited to," etc.). Those skilled in the art will further understand that if a specific number of recitations in a claim is intended, that intention will be explicitly recited in the claim; and, in the absence of such recitation, no such intention exists. For example, to aid in understanding, the following appended claims may include the introductory phrases "at least one" and "one or more" to introduce the claim recitations. However, the use of such phrases should not be interpreted as meaning that when a claim is introduced by the indefinite article "a" or "an," the claim is limited to embodiments containing only one of that recitation (e.g., "a" and / or "an" should be interpreted as "at least one" or "one or more"), even if the claim includes an introductory phrase such as "one or more" or "at least one" or an indefinite article such as "a" or "an"). The same applies to definite articles used to introduce claim recitations. Moreover, even when a specific number of introduced claim recitations is explicitly recited, those skilled in the art will understand that such recitation should be interpreted to mean "more than" the recited number (e.g., the simple recitation "two recitations," without any other modifier, means at least two recitations, i.e., two or more recitations).

[0110] While various embodiments of the present disclosure have been described for purposes of illustration, it will be understood that various changes may be made without departing from the scope of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope being indicated by the following claims.

Claims

1. A method for producing a silica or alumina wet gel for use in producing an aerogel or an aerogel slurry, comprising: (i) providing a precursor solution comprising an alkylsilane and / or a metal alkoxide, and reacting the precursor solution in the presence of a sol-gel solvent to form a reaction mixture having a pH of 3 to 9; and (ii) adding a gelling agent to the reaction mixture to form a wet gel; wherein the gelling agent is an alkaline earth metal solid.

2. 2. The method of claim 1, wherein the alkaline earth metal solid is selected from calcium oxide, magnesium oxide, barium oxide, and strontium oxide.

3. 3. The manufacturing method according to claim 1 or claim 2, wherein the precursor solution contains an alkylsilane selected from triethoxymethylsilane (MTES) and trimethoxymethylsilane (MTMS), a metal alkoxide selected from tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), aluminum tri-sec-butoxide, and polyethoxydisiloxane (PEDS), and mixtures thereof.

4. The method according to any one of claims 1 to 3, wherein the sol-gel solvent comprises an alcohol.

5. 5. The method according to claim 4, wherein the sol-gel solvent is a mixture of alcohol and water or alcohol and carbonated water.

6. 6. The method according to claim 4, wherein the alcohol is selected from the group consisting of ethanol, methanol, propanol, and butanol.

7. The method of any one of claims 1 to 6, wherein the silica or alumina wet gel is used to produce an aerogel, and further comprising mixing the wet gel to form a slurry mixture.

8. 8. The method of claim 7, further comprising adding a desiccant, and optionally water, to the slurry mixture.

9. The method of claim 8, wherein the desiccant is an alkaline earth metal solid.

10. The method of claim 9, wherein the desiccant is calcium oxide.

11. The method according to any one of claims 1 to 10, comprising introducing carbonated water into the reaction mixture according to any one of claims 1 to 6, and / or introducing carbon dioxide into the wet gel according to any one of claims 1 to 6 or the slurry mixture according to any one of claims 7 to 10, to form an aerogel or an aerogel slurry.

12. The step of introducing carbon dioxide into the wet gel or slurry mixture may include: ２ A gas is introduced into the wet gel or slurry mixture, or the wet gel or slurry mixture is immersed in atmospheric CO ２ 12. The method of claim 11, comprising exposing the

13. A method according to any one of claims 1 to 12, comprising adding fibres.

14. reacting a precursor solution in the presence of a sol-gel solvent and adding a gelling agent to form a wet gel; and / or mixing the wet gel to form a slurry mixture; The method of claim 13, wherein the step (a) is carried out in the presence of fibers.

15. 15. The method of claim 13 or claim 14, wherein the fibers are ceramic fibers, organic fibers, carbon fibers, or fiberglass.

16. The method of any one of claims 11 to 15, further comprising drying the aerogel.

17. alkylsilanes and / or metal alkoxides, alkaline earth metal solids, Alcohol, and A kit comprising instructions for carrying out the method of any one of claims 1 to 16.

18. CO in silica or alumina aerogel or aerogel slurry ２ 1. A method for capturing CO in a process for producing a silica or alumina aerogel or aerogel slurry, comprising: ２ with an alkaline earth metal solid to obtain an alkaline earth metal carbonate entrapped within the pores of the aerogel or aerogel slurry product.

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