A method for rapidly synthesizing high specific surface area silica aerogel

Abstract

The application discloses a method for rapidly synthesizing high specific surface area silicon dioxide aerogel, and relates to the technical field of aerogel material synthesis, and comprises the following steps: constructing a microwave coupling ionic liquid synergistic reaction system to realize the integrated preparation of depolymerization and polycondensation of wet gel; the wet gel is dried by vacuum flash extraction to form a silicon dioxide porous framework; the framework is reinforced and the pore channel is regulated; the hydrophobic modification is performed according to the pore channel characteristics to complete the whole closed-loop preparation from the silicon ester raw material to the high specific surface area hydrophobic silicon dioxide aerogel; by constructing the synergistic reaction system, the integrated preparation of depolymerization and polycondensation of the silicon ester is realized; in combination with the new drying process, the high-efficiency synthesis of the aerogel is realized; the porous framework is in-situ doped and reinforced, the pore channel is optimized and the hydrophobic modification is performed, and the mechanical strength, the hydrophobic performance and the structural stability are improved; the closed-loop linkage continuous process is adopted, the product performance is consistent and stable, and the path is provided for the large-scale production of the high specific surface area silicon dioxide aerogel.

Description

Technical Field

[0001] This invention relates to the field of aerogel material synthesis technology, specifically a method for rapidly synthesizing silica aerogels with high specific surface area. Background Technology

[0002] Silica aerogel, as a novel nanoporous inorganic material, possesses excellent properties such as ultra-high specific surface area, extremely low thermal conductivity, and high porosity, demonstrating significant application value in aerospace thermal insulation, industrial catalyst carriers, and environmental adsorption and separation, thus becoming a research hotspot in the field of new materials. Among them, high specific surface area hydrophobic silica aerogels have a wider range of applications due to their combination of moisture resistance and structural advantages. However, existing preparation processes struggle to balance reaction efficiency and product structural stability. Achieving rapid, high-quality, and continuous synthesis has become a key issue restricting the industrial application of this material.

[0003] Existing silica aerogel preparation technologies have many shortcomings. Traditional solvothermal methods involve depolymerization and polycondensation in separate steps, resulting in long reaction cycles and the need for strong acid and base catalysts, which can easily lead to local agglomeration and structural defects in the silica network. The drying process often uses conventional vacuum drying, which can easily cause the framework to collapse due to capillary forces, resulting in a significant reduction in the specific surface area of ​​the product. Framework reinforcement and pore control are independent of each other, which can easily lead to pore blockage or insufficient framework strength. Furthermore, hydrophobic modification is not designed in conjunction with pore characteristics, resulting in uneven distribution of modifiers and poor hydrophobic effect. At the same time, most processes are intermittent operations, and oxidation and moisture absorption can easily occur during material transfer. Without full-process closed protection, it is difficult to stably prepare hydrophobic products with high specific surface area.

[0004] Current limitations in silica aerogel preparation technology, particularly in reaction efficiency, structural control, and process continuity, restrict the large-scale production and application of high specific surface area hydrophobic products. Existing methods cannot achieve efficient integrated depolymerization and polymerization, nor can they synergistically match drying, reinforcement, pore control, and hydrophobic modification. Furthermore, they lack a stable reaction environment and a closed-loop continuous process throughout the entire process. Therefore, developing a method for synthesizing high specific surface area silica aerogels that enables rapid reaction, precise structural control, and continuous closed-loop preparation has become an urgent technical challenge. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for rapidly synthesizing high specific surface area silica aerogels. This method involves constructing a microwave-coupled ionic liquid system to achieve integrated depolymerization and polycondensation of silica esters, thereby obtaining a wet gel. The gel is then dried and shaped by vacuum flash evaporation and coupled extraction to obtain a complete porous framework. The framework is reinforced by in-situ doping, and the pores are optimized using algorithms. Finally, hydrophobic modification is performed based on the pore characteristics to obtain the final product, achieving a closed-loop preparation process.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for rapidly synthesizing high specific surface area silica aerogel, the specific steps of which are as follows: S100, Construction of the synergistic reaction system: Construct a microwave-coupled ionic liquid synergistic reaction system. The microwave-coupled ionic liquid synergistic reaction system simultaneously provides matching microwave energy input for the depolymerization of silane and provides a stable ionic liquid reaction environment for the polycondensation of silanol, forming a synergistic reaction basis that runs through the entire process of integrated depolymerization and polycondensation preparation. S200, integrated preparation of depolymerization and polycondensation: Silicon ester raw materials are placed in a microwave-coupled ionic liquid synergistic reaction system. Under the action of microwave field, the silicon ester is rapidly depolymerized to generate highly active silanol monomers. The reaction process is controlled in real time by the apparent rate control algorithm of silanol polycondensation reaction to complete the low-temperature directional silanol polycondensation crosslinking and form a uniform three-dimensional silicon-oxygen gel network to obtain wet gel. S300, Coupled Extraction Drying and Shaping: The wet gel prepared by S200 is introduced into the vacuum flash evaporation-coupled extraction process. First, most of the liquid phase components in the wet gel are quickly removed by vacuum flash evaporation, and then the residual solvent and impurities are removed by coupled extraction to obtain a complete silica porous framework. S400, skeleton reinforcement and precise control of pores: The porous skeleton obtained by S300 is subjected to structural reinforcement. Based on the structural parameters of the reinforced skeleton, the pore distribution is optimized by the specific surface area directional control correlation algorithm of the porous skeleton, and the specific surface area is coordinated to achieve mutual adaptation between the skeleton structure and the pore characteristics. S500 and pore matching hydrophobic modification: Combining the pore characteristics of the porous framework after S400 regulation, the surface of the framework and the inner wall of the pores are hydrophobically modified to finally obtain a high specific surface area hydrophobic silica aerogel, completing the closed-loop preparation from silicone ester raw materials to finished products.

[0007] Furthermore, the microwave-coupled ionic liquid synergistic reaction system includes a microwave generating module and an ionic liquid circulation supply module: the microwave generating module outputs a microwave power of 200 to 800 W and a microwave frequency of 2450 ± 50 MHz. This frequency band matches the resonant frequency of the polar groups of the ionic liquid, which can maximize the absorption and transfer efficiency of microwave energy; the ionic liquid provided by the ionic liquid circulation supply module is one or more of imidazole, pyridine, or piperidine ionic liquids. The ionic liquid simultaneously serves as a microwave sensitizer, reaction medium, and structural template agent. It can efficiently absorb microwave energy and uniformly transfer it to the reaction system, improving the depolymerization efficiency of silicone esters. It can also provide a stable polar environment for the polycondensation reaction, regulate the crosslinking mode of the silicon-oxygen network, and avoid local agglomeration or structural defects.

[0008] Furthermore, the silicone ester raw material is one or a mixture of tetraethyl orthosilicate, propyl orthosilicate, and methyltriethoxysilane; the reaction temperature for rapid depolymerization of the silicone ester is 60 to 80°C, and the reaction time is 10 to 30 minutes. During the depolymerization process, the mass ratio of ionic liquid to silicone ester raw material is 1:1 to 3:1. Through uniform input of microwave energy, the silicon-oxygen bonds of the silicone ester raw material are broken to generate highly active hydroxyl-terminated silanol monomers; the reaction temperature for low-temperature directional silanol condensation crosslinking is 30 to 60°C, and the reaction time is 20 to 40 minutes. No additional strong acid or strong base catalyst is required. The hydroxyl groups of the silanol monomers are activated by the anions and cations of the ionic liquid, guiding the silanol monomers to undergo directional dehydration condensation to form a continuous and uniform three-dimensional silicone-oxygen gel network. The porosity of the obtained wet gel is 70% to 85%, and the gel particle size is 50 to 200 nm.

[0009] Furthermore, the calculation formula for the apparent rate control algorithm of the silanol polycondensation reaction is as follows: , in, The apparent rate constant for the polycondensation of silanol monomers is given in units of 1000 m³ / s. The adjustment range is 0.05 to 0.2. ; It is the pre-exponential factor for the polycondensation reaction of silanol monomers and is positively correlated with the number of hydroxyl groups and activity of the highly active silanol monomers generated in S200. The apparent activation energy for the polycondensation reaction of silanol monomers is expressed in kJ / mol and ranges from 20 to 40 kJ / mol. The value is the microwave energy coupling coefficient, which is related to the microwave frequency matching degree of the microwave-coupled ionic liquid synergistic reaction system in S100, and ranges from 0.8 to 1.2. The microwave power input to the microwave-coupled ionic liquid synergistic reaction system in S100 is expressed in W. The effective dielectric loss factor of the reaction system at the corresponding microwave frequency is mainly determined by the dielectric loss characteristics of the ionic liquid, and its value ranges from 0.2 to 0.8. This is the universal gas constant, with a fixed value of 8.314 J / mol·K; The temperature of the low-temperature directional polycondensation crosslinking reaction is expressed in K. By controlling the apparent rate of the polycondensation reaction in real time, we can ensure that the silanol monomers are directionally crosslinked to form a uniform three-dimensional silica gel network, thus avoiding local agglomeration caused by excessively fast polycondensation rate or loose network structure caused by excessively slow rate.

[0010] Furthermore, the vacuum flash evaporation-coupled extraction process is a continuous closed-loop process. The wet gel is directly transported to the flash evaporator through a closed pipeline to complete vacuum flash evaporation, and then directly transported to the coupled extraction vessel through a closed pipeline to complete extraction, with no material exposure throughout the process. The vacuum degree of vacuum flash evaporation is -0.08 to -0.095 MPa, the flash temperature is 40 to 50°C, and the flash time is 30 to 60 min, which can remove 80% to 90% of the liquid phase components in the wet gel. Through low-temperature flash evaporation under low vacuum environment, the capillary force during solvent evaporation is significantly reduced, avoiding the collapse of the gel skeleton. The coupled extraction uses food-grade carbon dioxide as the extractant, with an extraction pressure of 8 to 15 MPa, an extraction temperature of 31 to 40°C, and an extraction time of 60 to 120 min. The strong solubility and high fluidity of carbon dioxide are utilized to remove residual ionic liquids, unreacted monomers, and by-products in the porous skeleton.

[0011] Furthermore, the structural reinforcement treatment employs an in-situ doping process with nano-reinforcers. The nano-reinforcers are one or more of nano-silica, nano-alumina, and carbon nanotubes, with a particle size of 5 to 20 nm, matching the pore size of the porous framework. They can be uniformly dispersed on the inner walls and nodes of the porous framework's pores to form a rigid support structure. The amount of nano-reinforcers added is 1% to 5% of the dry basis mass of the porous framework. The reinforcement treatment temperature is 100 to 150°C, and the treatment time is 60 to 90 minutes. Through heat treatment, the nano-reinforcers bond with the silicon-oxygen bonds of the porous framework to form an integrated structure, which can effectively avoid framework shrinkage and pore blockage during subsequent pore regulation and hydrophobic modification processes.

[0012] Furthermore, the calculation formula for the porous skeleton specific surface area directional control correlation algorithm is as follows: , in, The target specific surface area after porous framework regulation is expressed in m². 2 / g, with a target control range of 800 to 1200m 2 / g; It is an empirical structure constant, which is related to the material of the reinforced porous framework, the doping amount of the nano-reinforcement and the degree of bonding, and its value ranges from 150 to 250. The initial pore volume of the reinforced porous framework is expressed in cm. 3 / g; The initial porosity of the reinforced porous framework; The initial average pore size of the reinforced porous framework is expressed in nm. The thermodynamic temperature for heat treatment controlled by specific surface area, in K, with a control range of 373 to 473 K; For reference thermodynamic temperature, a fixed value of 298K is used; The heat preservation time is controlled by specific surface area, in hours, and the control range is 1 to 3 hours. By establishing a correlation model between the initial structural parameters of the reinforced porous skeleton and the heat treatment control parameters through formulas, the heat treatment temperature and holding time are optimized to achieve directional control of the specific surface area and pore distribution of the porous skeleton.

[0013] Furthermore, the hydrophobic modification is performed using vapor deposition. Combined with the pore characteristics regulated by S400, the modifier is uniformly diffused to the inner wall of the porous framework by controlling the deposition temperature and time, thus completing the hydrophobic modification of the inner surface of the pores. The modifier used for hydrophobic modification is one or a mixture of methyltriethoxysilane, trimethylchlorosilane, and hexamethyldisilazane. The dry-basis mass ratio of the modifier to the porous framework is 0.05:1 to 0.15:1, the modification temperature is 80 to 100°C, and the modification time is 60 to 120 minutes. During the modification process, the siloxane groups of the modifier undergo dehydration condensation with the hydroxyl groups on the surface of the porous framework, forming a uniformly grafted hydrophobic alkyl layer on the framework surface and the inner wall of the pores, achieving a match between the pore regulation parameters and the hydrophobic modification effect.

[0014] Furthermore, the entire process from S100 to S500 uses closed pipelines to achieve continuous material transport. The material transport between each process is protected by inert gas, which is nitrogen or argon, and the transport pressure is 0.1 to 0.3 MPa. This can prevent the material from oxidizing, absorbing moisture, becoming contaminated, or suffering structural damage during transport. The output product of the previous process is directly used as the input raw material for the next process. There are no intermediate settling, secondary transfer, or pretreatment steps, forming a continuous preparation with a closed-loop linkage throughout the entire process.

[0015] Compared with existing technologies, this method for rapidly synthesizing high specific surface area silica aerogels has the following advantages: I. This invention constructs a synergistic reaction system coupled with microwaves and ionic liquids, providing a suitable full-process reaction foundation for the depolymerization of silanes and the polycondensation of silanols. This enables integrated preparation of depolymerization and polycondensation, and relies on a reaction rate control algorithm to monitor the reaction process in real time, guiding the directional polycondensation and crosslinking of silanol monomers to form a uniform three-dimensional silica gel network, avoiding problems such as local agglomeration and loose structure. Simultaneously, a drying and molding process combining vacuum flash evaporation and coupled extraction is employed, reducing damage to the gel skeleton during drying and ensuring the structural integrity of the porous framework. The reaction process requires no additional acid or base catalysts, reducing the generation of byproducts and impurities. The entire process involves closed-loop material transport, avoiding oxidation and moisture absorption, significantly improving overall preparation efficiency and achieving efficient and rapid synthesis of aerogels.

[0016] II. This invention strengthens a porous framework through in-situ doping, and optimizes the pore distribution using a directional control algorithm based on the strengthened framework parameters. This achieves a perfect match between the framework structure and pore characteristics, effectively improving the mechanical strength of the porous framework and avoiding problems such as framework shrinkage and pore blockage in subsequent processes. Simultaneously, hydrophobic modification is performed based on the regulated pore characteristics, allowing the modifier to diffuse uniformly and graft onto the framework surface and pore inner walls. This achieves a precise match between pore parameters and the hydrophobic modification effect, significantly improving the product's hydrophobic properties and structural stability. The entire process employs a closed-loop, continuous manufacturing process, with direct connection between products from each step without intermediate processing, ensuring consistent and stable product performance. This provides a reliable path for the large-scale industrial production of high specific surface area silica aerogels.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 A flowchart illustrating the steps of a method for rapidly synthesizing silica aerogels with high specific surface area; Figure 2 Flowchart for constructing a microwave-coupled ionic liquid synergistic reaction system for a rapid synthesis of high specific surface area silica aerogels; Figure 3 This is a detailed flow chart of the vacuum flash evaporation-coupled extraction process for a method of rapidly synthesizing high specific surface area silica aerogels. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below. Example

[0021] S100. Construction of the Synergistic Reaction System: A microwave-coupled ionic liquid synergistic reaction system was constructed. This system comprises two core modules: a microwave generation module and an ionic liquid circulation and supply module. The microwave generation module outputs a microwave power of 600W and a microwave frequency of 2460MHz. This frequency band is precisely matched with the resonant frequency of the polar groups of the ionic liquid, enabling the ionic liquid to maximize the absorption and transfer of microwave energy. This provides a highly suitable microwave energy input for the subsequent depolymerization of silicone esters. The ionic liquid circulation and supply module provides the system with an imidazole ionic liquid, which simultaneously serves as a microwave sensitizer, reaction medium, and structural template agent. This system plays multiple roles, efficiently absorbing microwave energy released by the microwave generator module and uniformly transferring the energy to the entire reaction system. This accelerates the overall process of silicone ester depolymerization and creates a stable polar environment for subsequent silanol polycondensation. It precisely controls the crosslinking mode of the silicon-oxygen network, avoiding potential local agglomeration or structural defects during the reaction process from the source. This microwave-coupled ionic liquid synergistic reaction system simultaneously provides matching microwave energy input for silicone ester depolymerization and a stable ionic liquid reaction environment for silanol polycondensation. Ultimately, it forms a synergistic reaction foundation that runs through the entire preparation process, laying a solid and unified reaction environment foundation for the efficient and stable implementation of subsequent processes.

[0022] S200, Integrated Depolymerization and Polycondensation Preparation: Tetraethyl orthosilicate, a silicone ester raw material, is placed in a fully sealed microwave-coupled ionic liquid synergistic reaction system. The energy released by the microwave field is uniformly applied to the entire reaction system, initiating the rapid depolymerization process of the silicone ester. The reaction temperature for rapid depolymerization of silicone ester is precisely controlled at 75℃, and the reaction time is set to 25 min. During the depolymerization process, the mass ratio of imidazole ionic liquid to tetraethyl orthosilicate is strictly controlled at 3:1. The uniform and continuous input of microwave energy can efficiently break the silicon-oxygen bonds in the tetraethyl orthosilicate molecule, promoting its rapid and complete decomposition to generate hydroxyl-terminated highly active silanol monomers. The highly active silanol monomers can provide sufficient and high-quality reaction building blocks for the subsequent polycondensation reaction, allowing the polycondensation reaction to proceed in an orderly manner. Subsequently, the apparent rate control algorithm for the silanol polycondensation reaction is used to control the reaction process in real time and with precision. The formula is: ,in, is the apparent rate constant for the polycondensation reaction of silanol monomers; It is the pre-exponential factor for the polycondensation reaction of silanol monomers; It represents the apparent activation energy of the polycondensation reaction of silanol monomers; The microwave energy coupling coefficient; The microwave power input to the microwave-coupled ionic liquid synergistic reaction system in S100; The effective dielectric loss factor of the reaction system at the corresponding microwave frequency; This is the universal gas constant; The reaction thermodynamic temperature for low-temperature directional polycondensation crosslinking is defined by this algorithm. The reaction temperature is controlled at 50℃, and the reaction time is set to 35 minutes. The entire polycondensation process requires no additional strong acid or base catalysts, fundamentally avoiding the impurity residue problem caused by the introduction of exogenous catalysts and eliminating unnecessary interference from the catalyst on the silicon-oxygen network structure. The cations and anions of imidazole ionic liquids efficiently activate the hydroxyl groups of the silanol monomers, guiding them to undergo dehydration condensation reactions in a predetermined direction, gradually forming a continuous and uniform three-dimensional silicon-oxygen gel network. Finally, a wet gel with a porosity of 80% and a gel particle size of 150 nm is obtained. The uniform three-dimensional silicon-oxygen gel network provides the wet gel with a regular and interconnected pore structure, reserving sufficient structural space for subsequent drying, extraction, and framework control processes, ensuring further optimization of the pore structure in subsequent steps.

[0023] S300, Coupled Extraction and Drying: The prepared wet gel is directly transported to the flash evaporator through a closed pipeline without contact. The entire process adopts a continuous, closed vacuum flash evaporation-coupled extraction process. From entering the flash evaporator to completing the extraction, the wet gel is kept in a closed environment without any exposure, fundamentally avoiding oxidation, moisture absorption, and contamination problems caused by contact with outside air. It also prevents damage to the initial structure of the gel caused by the external environment. First, a vacuum flash evaporation operation is carried out. The vacuum degree of the vacuum flash evaporation is strictly controlled at -0.095MPa, the flash evaporation temperature is set at 48℃, and the flash evaporation time is controlled at 55min. The combination of low vacuum and low temperature flash evaporation conditions can significantly reduce the capillary force generated during solvent evaporation, effectively preventing the collapse of the gel skeleton due to capillary force, and maximizing the integrity of the original structure of the gel skeleton. Under this process condition, 90% of the liquid phase component in the wet gel can be quickly removed, significantly reducing the liquid phase content in the wet gel, which reduces the processing load of the subsequent extraction process. This process also allows the porous structure of the gel skeleton to initially emerge. After vacuum flash evaporation, the material is directly transported to the coupling extraction vessel via a closed pipeline for coupling extraction. Food-grade carbon dioxide is used as the extractant in the coupling extraction. Food-grade carbon dioxide has the characteristics of being residue-free and pollution-free, and will not have any negative impact on the structure and subsequent performance of the porous skeleton. The extraction pressure is controlled at 14 MPa, the extraction temperature is set at 38℃, and the extraction time is controlled at 110 min. The strong solubility and high fluidity of carbon dioxide itself can penetrate into the various micropores of the porous skeleton, fully dissolve and remove residual ionic liquids, unreacted silicon ester monomers, and by-products generated during the reaction, achieving deep and comprehensive removal of impurities inside the porous skeleton. Finally, a silica porous skeleton with a complete structure, interconnected pores, and high purity is obtained. The high-purity porous skeleton provides a high-quality structural base for subsequent skeleton reinforcement and precise pore control, allowing subsequent control operations to be carried out more accurately.

[0024] S400, Framework Reinforcement and Precise Pore Control: The obtained structurally complete porous silica framework undergoes structural reinforcement treatment. This reinforcement operation is carried out using an in-situ doping process with nano-reinforcers. 15nm nano-silica particles are selected as the nano-reinforcers. This particle size highly matches the pore size of the porous framework, allowing it to smoothly enter the pores and be uniformly dispersed on the pore walls and at key locations such as framework nodes, forming a uniform rigid support structure at these locations. The amount of nano-silica added is strictly set to 4% of the dry basis mass of the porous framework. This amount ensures effective reinforcement of the porous framework without causing pore blockage due to excessive addition, thus avoiding affecting the pore structure characteristics of the porous framework. The reinforcement treatment temperature is controlled at... At 140℃ and a processing time of 85 minutes, the appropriate heat treatment temperature and time allow for a stable bonding reaction between the silicon-oxygen bonds of the nano-silica and the porous framework, forming a tight integrated structure. This significantly enhances the mechanical strength of the porous framework at the structural level, effectively avoiding framework shrinkage and pore blockage problems that easily occur during subsequent pore control and hydrophobic modification. This ensures the stability of the framework structure and the connectivity of the pores. Subsequently, the actual structural parameters of the reinforced porous framework are accurately detected and obtained. Based on these parameters, a porous framework specific surface area directional control correlation algorithm is activated. This algorithm systematically and accurately optimizes the pore distribution of the porous framework, achieving synergistic control of the specific surface area through scientific algorithm regulation. The formula is: ,in, The target specific surface area after the porous framework is regulated; These are empirical structure constants; The initial pore volume of the reinforced porous framework; The initial porosity of the reinforced porous framework; The initial average pore size of the reinforced porous framework; Thermodynamic temperature for heat treatment controlled by specific surface area; Reference thermodynamic temperature; The heat preservation time is adjusted to control the specific surface area; the overall structure of the skeleton is highly adapted to the characteristics of pore size distribution, pore volume, and porosity of the pores, so that the porous skeleton has better pore structure characteristics, creating favorable structural conditions for the uniform and comprehensive development of subsequent hydrophobic modification.

[0025] S500, Pore-Matching Hydrophobic Modification: Combining the pore characteristics of the porous skeleton optimized by a specific surface area-oriented control correlation algorithm, a vapor deposition method is used to comprehensively and uniformly modify the outer surface of the skeleton and the inner walls of the pores. Hexamethyldisilazane is selected as the hydrophobic modifier, and the mass ratio of the modifier to the dry basis of the porous skeleton is precisely set to 0.12:1. The modification temperature is controlled at 95℃, and the modification time is set to 110 min. The temperature and time of vapor deposition are precisely controlled according to the pore size distribution, pore volume, and other pore characteristics of the porous skeleton, allowing the hexamethyldisilazane modifier to diffuse smoothly and uniformly to all the inner walls of the pores of the porous skeleton in the gas phase, without any... In cases of excessive local deposition or incomplete deposition in some pores, ensuring comprehensive hydrophobic modification is crucial. During the modification process, the siloxane groups of hexamethyldisilazane undergo a spontaneous and stable dehydration condensation reaction with the hydroxyl groups on the porous framework surface, forming a uniformly grafted and firmly bonded hydrophobic alkyl layer on the outer surface of the framework and the inner wall of the pores. This hydrophobic alkyl layer endows the porous framework with excellent and durable hydrophobic properties, while simultaneously achieving a precise match between pore control parameters and the hydrophobic modification effect. This allows the final high specific surface area hydrophobic silica aerogel to possess multiple core characteristics, including high specific surface area, regular pore structure, and excellent hydrophobic properties, successfully completing the closed-loop preparation process from silicone ester raw materials to finished product. Figure 1 As shown.

[0026] In this embodiment, the entire process from the construction of the S100 synergistic reaction system to the S500 pore matching hydrophobic modification adopts a closed pipeline to achieve continuous and contactless material transportation. Nitrogen is used as an inert gas for protection during the material transportation between each process. The nitrogen transportation pressure is strictly controlled at 0.25MPa. The stable inert gas protective atmosphere can completely isolate the material from contact with oxygen and water vapor in the air, avoiding oxidation, moisture absorption, and contamination of the material during transportation. At the same time, it prevents the destruction of the skeleton structure caused by external environmental interference. In the entire process, the output product of the previous process is directly used as the input raw material of the next process, without any intermediate standing, secondary transfer, or pretreatment links, forming a continuous preparation mode with closed-loop linkage throughout the process. This mode can significantly improve the overall preparation efficiency, reduce material loss during transportation, and ensure the continuity of reaction between each process, so that the prepared silica aerogel has more stable and better comprehensive performance indicators. In this embodiment, the parameters of each process are precisely controlled and the links between each step are closely connected. The resulting high specific surface area hydrophobic silica aerogel has a regular pore structure and excellent hydrophobic properties. Moreover, no additional impurities are introduced during the preparation process, and the purity and performance stability of the product are at a high level. The overall preparation process is efficient and environmentally friendly, and meets the basic requirements of industrial continuous production. Example

[0027] S100. Construction of the Synergistic Reaction System: A microwave-coupled ionic liquid synergistic reaction system was constructed. This system consists of a microwave generating module and an ionic liquid circulation supply module. The two work synergistically to form an integrated reaction system. The microwave generating module outputs a microwave power of 250W and a microwave frequency of 2430MHz. This frequency band is highly matched with the resonant frequency of the polar groups of the ionic liquid, enabling the ionic liquid to efficiently absorb microwave energy and uniformly transfer the energy to all regions of the reaction system. This provides the system with a highly matched microwave energy input for the depolymerization of silicone esters. The ionic liquid circulation supply module provides the system with pyridine. This ionic liquid, acting as a microwave sensitizer, reaction medium, and structural template, rapidly absorbs the microwave energy released by the microwave generator and uniformly distributes it throughout the reaction system. This effectively improves the reaction efficiency of silicone ester depolymerization and simultaneously creates a stable polar environment for subsequent silanol polycondensation. By scientifically controlling the crosslinking mode of the silicon-oxygen network, it avoids problems such as localized agglomeration or structural defects from the initial reaction stage. This microwave-coupled ionic liquid synergistic reaction system simultaneously provides matching microwave energy input for silicone ester depolymerization and a stable ionic liquid reaction environment for silanol polycondensation, ultimately forming a synergistic reaction foundation throughout the entire preparation process. Figure 2 As shown, this allows each subsequent preparation step to be carried out in a unified and stable reaction environment, ensuring the consistency and stability of the reactions in each step.

[0028] S200, Integrated Depolymerization and Polycondensation Preparation: The silicone ester raw material, methyltriethoxysilane, is placed in a sealed microwave-coupled ionic liquid synergistic reaction system. The energy released by the microwave field is uniformly applied to the reaction system, initiating the rapid depolymerization process of the silicone ester. The reaction temperature for rapid depolymerization is precisely controlled at 62℃, and the reaction time is set to 12 minutes. During the depolymerization process, the mass ratio of pyridine ionic liquid to methyltriethoxysilane is controlled at 1.2:1. The uniform input of microwave energy can efficiently and rapidly break the silicon-oxygen bonds of methyltriethoxysilane, promoting its complete decomposition to generate hydroxyl-terminated highly active silanol monomers. These highly active silanol monomers provide sufficient reactants for subsequent polycondensation reactions, ensuring the smooth progress of the polycondensation reaction. Subsequently, an apparent rate control algorithm for silanol polycondensation is used to precisely control the reaction process in real time and dynamically. The algorithm conducts a low-temperature directional polycondensation and crosslinking reaction of silanols. The reaction temperature is controlled at 32℃ and the reaction time is set to 22 minutes. The entire polycondensation process does not require the addition of strong acid or strong base catalysts, avoiding the impurities caused by exogenous catalysts and preventing the adverse effects of catalysts on the three-dimensional siloxane gel network structure. The cations and anions of pyridine ionic liquids efficiently activate the hydroxyl groups of silanol monomers, guiding the silanol monomers to undergo dehydration condensation reactions in a preset direction, gradually forming a continuous, uniform, and dense three-dimensional siloxane gel network. Finally, a wet gel with a porosity of 73% and a gel particle size of 60nm is obtained. The dense and uniform three-dimensional siloxane gel network makes the pore structure of the wet gel more refined, providing a refined structural basis for subsequent drying extraction and pore channel control, making it easier to achieve precise control of the pores.

[0029] S300, Coupled Extraction and Drying: The prepared wet gel is directly transported to a flash evaporator through a closed pipeline. The entire process is a continuous, closed-loop vacuum flash evaporation-coupled extraction process. The material remains in a completely sealed environment throughout this process, with no contact with the outside world, completely preventing oxidation, moisture absorption, and contamination. It also prevents damage to the initial pore structure of the wet gel from the external environment. First, a vacuum flash evaporation operation is performed. The vacuum level is controlled at -0.082 MPa, the flash temperature is set at 41℃, and the flash time is controlled at 35 minutes. The low vacuum and low temperature process conditions effectively reduce the capillary forces generated during solvent evaporation, fundamentally preventing the collapse of the gel skeleton due to capillary forces, and preserving the original pore structure of the wet gel to the greatest extent. Under these conditions, 82% of the liquid phase components in the wet gel can be rapidly removed, significantly reducing the amount of wet gel. The high liquid content in the liquid phase allows the porous framework of the gel to initially take shape, while reducing the processing pressure of the subsequent coupled extraction process. After vacuum flash evaporation, the material is directly transported to the coupled extraction vessel through a closed pipeline for coupled extraction. Food-grade carbon dioxide is used as the extractant in the coupled extraction. Food-grade carbon dioxide is residue-free and pollution-free, and will not have any adverse effects on the structure and properties of the porous framework. The extraction pressure is controlled at 9 MPa, the extraction temperature is set at 32℃, and the extraction time is controlled at 70 min. The strong solubility and high fluidity of carbon dioxide can penetrate deep into the fine pores of the porous framework, fully dissolving and carrying away residual ionic liquids, unreacted methyltriethoxysilane monomers, and reaction byproducts within the framework, achieving comprehensive removal of impurities inside the porous framework. Finally, a silica porous framework with a complete structure, fine pores, and high purity is obtained. Figure 3 As shown, the high-purity fine-pore porous skeleton provides a high-quality structural carrier for subsequent skeleton reinforcement and precise control of the pores, allowing subsequent control operations to be carried out in a way that better matches the characteristics of the pores.

[0030] S400, Framework Reinforcement and Precise Pore Control: The obtained porous silica framework underwent structural reinforcement using an in-situ nano-reinforcement doping process. A mixture of 6nm alumina nanoparticles and carbon nanotubes was selected as the nano-reinforcement. This particle size highly matches the fine pore size of the porous framework, allowing it to smoothly enter the pores and be uniformly dispersed on the pore walls and at key locations such as framework nodes, forming a uniform rigid support structure. The addition amount of the nano-reinforcement mixture was set at 2% of the dry basis mass of the porous framework. This amount effectively reinforces the porous framework, improving its mechanical strength, without causing blockage of the fine pores due to excessive addition, thus ensuring the connectivity and precision of the porous framework's pores. The reinforcement treatment temperature was controlled at 115℃, and the treatment time was set at 70 minutes. Appropriate heat treatment temperature and time allow the nano-reinforcement mixture to effectively reinforce the porous framework and improve its mechanical strength. The silicon-oxygen bonds of the reinforced composite and the porous framework undergo a stable bonding reaction, forming a tight integrated structure. This structurally enhances the mechanical strength of the porous framework, effectively preventing framework shrinkage and pore blockage during subsequent pore control and hydrophobic modification. This ensures the stability and pore precision of the porous framework structure. Subsequently, the actual structural parameters of the reinforced porous framework are precisely detected. Based on these parameters, a specific surface area-oriented control algorithm is employed. This algorithm systematically and precisely optimizes the pore distribution of the porous framework. Through scientific algorithmic control, the specific surface area is synergistically controlled, achieving a high degree of fit between the overall framework structure and the pore size distribution and pore volume characteristics. This further optimizes the pore structure characteristics of the porous framework, making its pore features more suitable for subsequent hydrophobic modification requirements, laying a solid structural foundation for the uniform implementation of hydrophobic modification.

[0031] S500, Pore-Matching Hydrophobic Modification: Combining the pore characteristics of the porous skeleton optimized by a specific surface area-oriented control correlation algorithm, a comprehensive hydrophobic modification of the skeleton surface and pore inner walls is carried out using vapor deposition. A mixture of methyltriethoxysilane and trimethylchlorosilane is selected as the hydrophobic modifier. The mass ratio of the modifier mixture to the dry basis of the porous skeleton is precisely set to 0.06:1. The modification temperature is controlled at 82℃, and the modification time is set to 70min. The temperature and time of vapor deposition are precisely controlled according to the fine pore characteristics of the porous skeleton, allowing the modifier mixture to diffuse uniformly into all pore inner walls of the porous skeleton in gaseous form, even the fine pores. To achieve uniform deposition of the modifier and avoid insufficient local modification, ensuring the comprehensiveness and uniformity of hydrophobic modification, during the modification process, the siloxane groups of the modifier mixture undergo a stable dehydration condensation reaction with the hydroxyl groups on the surface of the porous framework, forming a uniformly grafted and firmly bonded hydrophobic alkyl layer on the surface of the framework and the inner wall of the pores. This hydrophobic alkyl layer enables the porous framework to have excellent hydrophobic properties, while achieving precise matching between pore control parameters and hydrophobic modification effects. This allows the final high specific surface area hydrophobic silica aerogel to possess the core characteristics of high specific surface area, fine pore structure, and excellent hydrophobic properties, successfully completing the closed-loop preparation process from silicone ester raw materials to finished products.

[0032] In this embodiment, the entire process from the construction of the S100 synergistic reaction system to the S500 pore matching hydrophobic modification is carried out using closed pipelines to achieve continuous material transportation. Argon is used as an inert gas for protection throughout the material transportation between each process. The argon transportation pressure is controlled at 0.12 MPa. The stable inert gas protective atmosphere can completely isolate the material from contact with oxygen and water vapor in the air, avoiding oxidation, moisture absorption, and contamination of the material during transportation. At the same time, it prevents damage to the porous framework structure caused by the external environment. In the entire process, the output product of the previous process is directly used as the input raw material of the next process, without any intermediate settling, secondary transfer, or pretreatment links, forming a continuous preparation mode with closed-loop linkage throughout the process. This mode can not only greatly improve the preparation efficiency and reduce the loss of materials during transportation, but also ensure the continuity of the reaction between each process, so that the prepared silica aerogel has more stable performance indicators. This embodiment addresses the needs for preparing fine-pore silica aerogels by precisely controlling the process parameters of each step. The preparation process is closely linked, resulting in high specific surface area hydrophobic silica aerogels with fine pores, stable structure, and excellent hydrophobic properties. Furthermore, no additional impurities are introduced during the entire preparation process, resulting in high product purity. The overall preparation process is efficient and environmentally friendly, making it suitable for the continuous preparation of fine high specific surface area hydrophobic silica aerogels.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for rapidly synthesizing high specific surface area silica aerogels, characterized in that, The specific steps of this method are as follows: S100, Construction of the synergistic reaction system: Construct a microwave-coupled ionic liquid synergistic reaction system. The microwave-coupled ionic liquid synergistic reaction system simultaneously provides matching microwave energy input for the depolymerization of silane and provides a stable ionic liquid reaction environment for the polycondensation of silanol, forming a synergistic reaction basis that runs through the entire process of integrated depolymerization and polycondensation preparation. S200, integrated preparation of depolymerization and polycondensation: Silicon ester raw materials are placed in a microwave-coupled ionic liquid synergistic reaction system. Under the action of microwave field, the silicon ester is rapidly depolymerized to generate highly active silanol monomers. The reaction process is controlled in real time by the apparent rate control algorithm of silanol polycondensation reaction to complete the low-temperature directional silanol polycondensation crosslinking and form a uniform three-dimensional silicon-oxygen gel network to obtain wet gel. S300, Coupled Extraction Drying and Shaping: The wet gel prepared by S200 is introduced into the vacuum flash evaporation-coupled extraction process. First, most of the liquid phase components in the wet gel are quickly removed by vacuum flash evaporation, and then the residual solvent and impurities are removed by coupled extraction to obtain a complete silica porous framework. S400, skeleton reinforcement and precise control of pores: The porous skeleton obtained by S300 is subjected to structural reinforcement. Based on the structural parameters of the reinforced skeleton, the pore distribution is optimized by the specific surface area directional control correlation algorithm of the porous skeleton, and the specific surface area is coordinated to achieve mutual adaptation between the skeleton structure and the pore characteristics. S500 and pore matching hydrophobic modification: Combining the pore characteristics of the porous framework after S400 regulation, the surface of the framework and the inner wall of the pores are hydrophobically modified to finally obtain a high specific surface area hydrophobic silica aerogel, completing the closed-loop preparation from silicone ester raw materials to finished products.

2. The method for rapidly synthesizing high specific surface area silica aerogel according to claim 1, characterized in that, In step S100, the microwave-coupled ionic liquid synergistic reaction system includes a microwave generating module and an ionic liquid circulation supply module: the microwave generating module outputs a microwave power of 200 to 800W and a microwave frequency of 2450±50MHz; the ionic liquid provided by the ionic liquid circulation supply module is one or more of imidazole, pyridine, or piperidine ionic liquids.

3. The method for rapidly synthesizing high specific surface area silica aerogel according to claim 1, characterized in that, In step S200, the silicone ester raw material is one or more of tetraethyl orthosilicate, propyl orthosilicate, and methyltriethoxysilane; the reaction temperature for rapid depolymerization of silicone ester is 60 to 80°C, and the reaction time is 10 to 30 minutes. During the depolymerization process, the mass ratio of ionic liquid to silicone ester raw material is 1:1 to 3:

1. Through uniform input of microwave energy, the silicon-oxygen bonds of silicone ester raw material are broken to generate hydroxyl-terminated highly active silanol monomers; the reaction temperature for low-temperature directional silanol condensation crosslinking is 30 to 60°C, and the reaction time is 20 to 40 minutes. No additional strong acid or strong base catalyst is required. The hydroxyl groups of silanol monomers are activated by the anions and cations of the ionic liquid, guiding the silanol monomers to undergo directional dehydration condensation to form a continuous and uniform three-dimensional silicone-oxygen gel network. The porosity of the obtained wet gel is 70% to 85%, and the gel particle size is 50 to 200 nm.

4. A method for rapidly synthesizing high specific surface area silica aerogel according to claim 1 or 3, characterized in that, In step S200, the calculation formula for the apparent rate control algorithm of the silanol polycondensation reaction is as follows: ， in, is the apparent rate constant for the polycondensation reaction of silanol monomers; It is the pre-exponential factor for the polycondensation reaction of silanol monomers; It represents the apparent activation energy of the polycondensation reaction of silanol monomers; The microwave energy coupling coefficient; The microwave power input to the microwave-coupled ionic liquid synergistic reaction system in S100; The effective dielectric loss factor of the reaction system at the corresponding microwave frequency; This is the universal gas constant; The reaction thermodynamic temperature is the low-temperature directional polycondensation crosslinking temperature.

5. The method for rapidly synthesizing high specific surface area silica aerogel according to claim 1, characterized in that, In step S300, the vacuum flash evaporation-coupled extraction process is a continuous closed process. The wet gel is directly transported to the flash evaporator through a closed pipeline to complete the vacuum flash evaporation, and then directly transported to the coupled extraction vessel through a closed pipeline to complete the extraction. There is no material exposure throughout the process. The vacuum degree of the vacuum flash evaporation is -0.08 to -0.095 MPa, the flash temperature is 40 to 50°C, and the flash time is 30 to 60 min. The coupled extraction uses food-grade carbon dioxide as the extractant, the extraction pressure is 8 to 15 MPa, the extraction temperature is 31 to 40°C, and the extraction time is 60 to 120 min. The strong solubility and high fluidity of carbon dioxide are used to remove residual ionic liquids, unreacted monomers, and by-products in the porous framework.

6. The method for rapidly synthesizing high specific surface area silica aerogel according to claim 1, characterized in that, In step S400, the structural reinforcement treatment employs an in-situ doping process with nano-reinforcement. The nano-reinforcement is one or more of nano-silica, nano-alumina, and carbon nanotubes, with a particle size of 5 to 20 nm, matching the pore size of the porous framework. It can be uniformly dispersed on the inner wall and nodes of the porous framework to form a rigid support structure. The amount of nano-reinforcement added is 1% to 5% of the dry basis mass of the porous framework. The reinforcement treatment temperature is 100 to 150°C, and the treatment time is 60 to 90 min. Through heat treatment, the nano-reinforcement bonds with the silicon-oxygen bonds of the porous framework to form an integrated structure.

7. A method for rapidly synthesizing high specific surface area silica aerogel according to claim 1 or 6, characterized in that, In step S400, the calculation formula for the porous skeleton specific surface area directional control correlation algorithm is as follows: ， in, The target specific surface area after the porous framework is regulated; These are empirical structure constants; The initial pore volume of the reinforced porous framework; The initial porosity of the reinforced porous framework; The initial average pore size of the reinforced porous framework; Thermodynamic temperature for heat treatment controlled by specific surface area; Reference thermodynamic temperature; The heat preservation time is controlled by the specific surface area. By establishing a correlation model between the initial structural parameters of the reinforced porous skeleton and the heat treatment control parameters through formulas, the heat treatment temperature and holding time are optimized to achieve directional control of the specific surface area and pore distribution of the porous skeleton.

8. The method for rapidly synthesizing high specific surface area silica aerogel according to claim 1, characterized in that, In step S500, the hydrophobic modification is performed using vapor deposition. Combined with the pore characteristics regulated in S400, the modifier is uniformly diffused to the inner wall of the porous framework by controlling the deposition temperature and time, thus completing the hydrophobic modification of the inner surface of the pores. The modifier used for hydrophobic modification is one or a mixture of methyltriethoxysilane, trimethylchlorosilane, and hexamethyldisilazane. The dry mass ratio of the modifier to the porous framework is 0.05:1 to 0.15:1, the modification temperature is 80 to 100°C, and the modification time is 60 to 120 min. During the modification process, the siloxane groups of the modifier undergo dehydration condensation with the hydroxyl groups on the surface of the porous framework, forming a uniformly grafted hydrophobic alkyl layer on the surface of the framework and the inner wall of the pores.

9. The method for rapidly synthesizing high specific surface area silica aerogel according to claim 1, characterized in that, The entire process from S100 to S500 uses closed pipelines to achieve continuous material transport. The material transport between each process is protected by inert gas, which is nitrogen or argon, and the transport pressure is 0.1 to 0.3 MPa. The output product of the previous process is directly used as the input raw material of the next process. There are no intermediate settling, secondary transfer or pretreatment links, forming a continuous preparation with a closed loop linkage throughout the process.

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