Method for preparing high-temperature-resistant silicon-aluminum aerogel by using coal gangue one-step method

Abstract

The invention relates to the technical field of silicon-aluminum aerogel preparation, in particular to a method for preparing high-temperature-resistant silicon-aluminum aerogel by using a coal gangue one-step method, which comprises the following steps: S1, crushing, grinding and sieving coal gangue, mixing the coal gangue with an alkaline solid, and calcining to obtain alkali fusion powder; s2, the alkali fusion powder is subjected to acid treatment and suction filtration, and a silicon-aluminum solution is obtained; s3, adding polystyrene-coated zirconium oxide particles into the silicon-aluminum solution, and sequentially carrying out gelation, primary aging, solvent washing, water washing and secondary aging; s4, washing, replacing and modifying the gel; and S5, drying the hydrophobic wet gel obtained in the step S4 at normal pressure to obtain the silicon-aluminum aerogel. The silicon-aluminum aerogel prepared by the method has the advantages of low density, good thermal stability, high specific surface area, strong hydrophobic property and high strength.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of silica-alumina aerogel, and specifically to a method for preparing high-temperature resistant silica-alumina aerogel by a one-step method using coal gangue. Background Art

[0002] As a lightweight nano-solid material, aerogel has both solid phase and void structures at the nano-scale and is often used as a thermal insulation material in many fields such as aerospace. Aerogel has a very low density, which can be as low as 0.16 mg / cm -3 ³. The thermal conductivity of aerogel is extremely low. Under normal temperature and pressure, the thermal conductivity of aerogel is generally less than 0.02 W / (m·K), and it can be as low as 0.004 W / (m·K) in a vacuum state. In addition, aerogel also has excellent properties such as a high specific surface area, light transmittance, and strong hydrophobicity. Therefore, aerogel can be used as an excellent thermal insulation material, and it can almost block the three heat transfer methods: heat conduction, heat convection, and heat radiation. The pore size in aerogel ranges from 1 to 100 nm, which can effectively prevent the flow of air. The raw materials currently used for the production of silica and alumina aerogels are usually tetraethyl orthosilicate, methyltriethoxysilane, aluminum chloride hexahydrate, and industrial water glass, etc. These raw materials, especially silane-based ones, are relatively expensive, and some of the raw materials are highly toxic. In the preparation process, most of them use the method of separately preparing two solutions of silicon and aluminum and then mixing them for use, and the process flow is complex. Moreover, the supercritical drying equipment used for drying has high costs, complex processes, and great risks, which restricts its large-scale commercial production and application. Research shows that the addition of aluminum elements weakens the tendency of the structure to collapse of SiO₂-Al₂O₃ aerogel compared with SiO₂ aerogel after heat treatment, increases the specific surface area, and the bulk density shows a decreasing trend. The increase in aluminum content can improve the thermal stability of aerogel.

[0003] Coal gangue is a waste and by-product generated during coal mining and processing. The large-scale stacking of coal gangue will occupy a large amount of land area, pollute the surrounding land and water bodies, and the escape or leaching of sulfides in coal gangue will pollute the atmosphere. Therefore, in the process of coal mining and utilization, the treatment and comprehensive utilization of coal gangue are very important to reduce environmental pollution and resource waste. Coal gangue contains a large amount of silicon and aluminum elements, with the SiO₂ content reaching 40 - 65%, and the Al₂O₃ content reaching 15 - 45%. Therefore, using coal gangue as a raw material to prepare aerogel, whether it is to prepare ultra-light silica aerogel or silica-alumina composite aerogel, not only reduces the production cost compared with using organic raw materials to produce chemical products such as alumina and water glass, but also realizes the environmental protection of mining areas and energy conservation and emission reduction.

[0004] At present, the preparation of aerogels from coal gangue mainly involves extracting silicon and aluminum elements from coal gangue to prepare SiO2 aerogels or SiO2-Al2O3 aerogels. However, the existing methods for preparing aerogels still have the following disadvantages: (1) In the traditional process of preparing SiO2-Al2O3 aerogels, the extraction of silicon and aluminum elements from coal gangue mainly involves the reaction of acids and bases with raw materials to obtain silicon and aluminum solutions respectively, and then mixing them to prepare silicon-aluminum aerogels. The process is complex and costly; (2) During the preparation of SiO2-Al2O3 aerogels, no additives are added, resulting in insufficient strength of the prepared SiO2-Al2O3 aerogels. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing high-temperature resistant silicon-aluminum aerogels from coal gangue by a one-step method to solve the problems raised in the above background technology.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A method for preparing high-temperature resistant silicon-aluminum aerogels from coal gangue by a one-step method, comprising the following steps: S1. Uniformly mix the coal gangue powder obtained after crushing, grinding, and sieving coal gangue with an alkaline solid mixture, and calcine and activate it in a muffle furnace to obtain an alkali-fused powder; S2. Mix the alkali-fused powder obtained in step S1 with deionized water in a certain proportion and stir for 10 - 30 minutes, then add a hydrochloric acid solution. After the reaction is complete, perform vacuum filtration. The filtered solution is a silicon-aluminum solution; S3. Add polystyrene-coated zirconia particles to the silicon-aluminum solution obtained in step S2, place it in an oven at 50 °C for gelation. After gelation, perform one-time aging. After one-time aging, put the gel into an organic solvent and treat it repeatedly twice. After treatment, wash it three times with deionized water; then place the gel in a nanofibrillated cellulose dispersion for secondary aging to obtain a wet gel; S4. Take out the wet gel after secondary aging in step S3, wash it three times with deionized water, then replace it three times successively with 50wt% ethanol, 80wt% ethanol, and absolute ethanol. Place it in a mixed solution of n-hexane, trimethylsilane, and absolute ethanol for surface modification to obtain a hydrophobic wet gel (hydrophobic SiO2-Al2O3 wet gel); S5. Perform atmospheric drying on the hydrophobic wet gel obtained in step S4 to obtain a silicon-aluminum aerogel (SiO2-Al2O3 aerogel).

[0007] Furthermore, in step S1, the coal gangue is sieved through a 100 - 300 mesh sieve after crushing and grinding; the calcination temperature in the muffle furnace is 700 - 1000 °C, and the calcination time is 0.5 - 3.0 hours.

[0008] Further, the alkaline solid in step S1 is one of sodium carbonate, sodium hydroxide, and calcium carbonate; the mass ratio of the coal gangue powder to the alkaline solid is (1.5 - 2):1.

[0009] Further, in step S2, the mass ratio of the alkali-fused powder to deionized water is 1:6; the concentration of the hydrochloric acid solution is 3 - 7 mol / L, the mass ratio between the hydrochloric acid solution and the alkali-fused powder is (2 - 4):1, and the treatment time of the hydrochloric acid solution is 0.5 - 2.5 h.

[0010] Further, in step S3, the temperature of the first aging is 40°C, and the time of the first aging is 15 - 20 h; the treatment time of the gel after the first aging with the organic solvent each time is 30 - 60 min; the temperature of the second aging is 50°C, and the time of the second aging is 10 - 15 h.

[0011] Further, the organic solvent in step S3 is a mixed solution of N,N-dimethylformamide, tetrahydrofuran, and deionized water, and the volume ratio of N,N-dimethylformamide, tetrahydrofuran, and deionized water is 1:3:2.5.

[0012] Further, the mass ratio of the polystyrene-coated zirconia particles in step S3 to the alkali-fused powder used in step S2 is 1:(15 - 30); the polystyrene-coated zirconia particles in step S3 are treated with a concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 1:3 for 45 min.

[0013] Further, in the nanofibrillated cellulose dispersion in step S3, the mass ratio of the nanofibrillated cellulose to deionized water is 1:150; the mass ratio of the used nanofibrillated cellulose to the alkali-fused powder used in step S2 is 1:(8 - 20).

[0014] Further, the time of each replacement in the three replacements in step S4 is 6 h; the volume ratio of n-hexane, trimethylsilane, and absolute ethanol is 8:2:1; the surface modification time is 6 - 48 h, and the surface modification temperature is 20 - 60°C.

[0015] Further, the atmospheric drying in step S5 is carried out at 60°C, 90°C, 120°C, and 150°C successively for 2 h under normal pressure.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. In the present invention, silica-alumina aerogel is prepared by a one-step method using coal gangue, a solid waste, which reduces the raw material cost of the material, has a simple process, and further improves the high-value utilization of silicon and aluminum elements in coal gangue. The atmospheric drying method used for drying is more economical and safe compared to the commonly used supercritical drying in industry. The obtained aerogel has low density, good thermal stability, high specific surface area, and strong hydrophobic properties. The SiO2-Al2O3 aerogel prepared by the present invention effectively improves the disadvantage of low service temperature and enhances the high-temperature stability compared to SiO2 aerogel.

[0017] 2. In the present invention, zirconia particles coated with polystyrene are dispersedly added during the first aging process. The polystyrene coating on zirconia increases the volume of zirconia, facilitating its dispersion. Finally, the polystyrene is removed by an organic solvent, leaving nanoscale zirconia as a rigid core, which improves the strength of the aerogel. Moreover, with the polystyrene coating on zirconia, the polystyrene shell is removed, leaving a more abundant pore structure in the gel. 3. During the second aging process of the present invention, in a dispersion containing nanocellulose, the nanocellulose more easily enters the gel with a rich pore structure and combines in the silicon-aluminum network. Together with the zirconia as a rigid core, the strength of the prepared aerogel is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the process flow chart for preparing silica-alumina aerogel of the present invention; Figure 2 is the hydrophobic property diagram of the silica-alumina aerogel in Example 1 of the present invention; Figure 3 is the microscopic structure diagram of the silica-alumina aerogel in Example 1 of the present invention; Figure 4 is the physical diagram of the silica-alumina aerogel in Example 1 of the present invention; Figure 5 is the apparent diagram of the silica-alumina aerogel in Example 1 of the present invention and SiO2 aerogel after calcination at 800 °C for 2 h ((a) is SiO2 aerogel, (b) is the aerogel prepared in Example 1). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Please refer to Figures 1 to 5 , the present invention provides: Example 1 A method for preparing high temperature resistant silicon-alumina aerogel by one-step method using coal gangue comprises the following steps: S1. 24.6 g of coal gangue powder obtained by crushing, grinding and passing through a 200-mesh sieve and 15.2 g of alkaline solid (sodium hydroxide) mixture are uniformly mixed, and the mixture is placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace is 900° C. and the calcination time is 2.2 h. S2, 22.4g of the alkali-fused powder obtained in step S1 and 134.4g of deionized water were mixed and stirred in proportion for 25min, and then 7.5g of 5mol / L hydrochloric acid solution was added and treated for 2.0h. After the reaction was complete, vacuum filtration was performed, and the solution obtained by filtration was a silicon-aluminum solution; S3, adding 0.89g of polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in a 50°C oven for gelation, aging the solution at 40°C for 18h, placing the solution in an organic solvent for repeated treatment twice after aging, with each treatment time of 45min, and washing the solution with deionized water three times after treatment; placing the solution in a nanocellulose dispersion for secondary aging at 50°C for 14h to obtain a wet gel, wherein the amounts of nanocellulose and deionized water in the nanocellulose dispersion are 2.24g and 336g, respectively; S4, taking out the wet gel after the secondary aging in step S3, washing it with deionized water three times, and then replacing it with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol three times in sequence, each replacement time is 6 hours, placing it in a mixed solution of n-hexane, trimethylsilane and anhydrous ethanol with a volume ratio of 8:2:1 for surface modification, the surface modification time is 28 hours, the surface modification temperature is 45°C, and a hydrophobic wet gel is obtained; S5, drying the hydrophobic wet gel obtained in step S4 at 60°C, 90°C, 120°C, and 150°C at normal pressure for 2 hours in sequence to obtain a silica-alumina aerogel; the density of the aerogel 3 aerogel is 0.131 g / cm 3 , thermal conductivity is 0.035W / (m·K), specific surface area is 612.2m 2 / g, and the hydrophobic angle is 142°.

[0021] Example 2 A method for preparing high temperature resistant silicon-alumina aerogel by one-step method using coal gangue comprises the following steps: S1. 24.6 g of coal gangue powder obtained by crushing, grinding and passing through a 100-mesh sieve and 16.4 g of alkaline solid (calcium carbonate) mixture are uniformly mixed, and the mixture is placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace is 700° C. and the calcination time is 0.5 h. S2. Mix the 22.4 g of alkali-fused powder obtained in step S1 and 134.4 g of deionized water in proportion and stir for 10 min. Then add 11.2 g of 3 mol / L hydrochloric acid solution and treat for 0.5 h. After the reaction is complete, perform vacuum filtration. The filtered solution is the silicon-aluminum solution; S3. Add 1.49 g of polystyrene-coated zirconia particles to the silicon-aluminum solution obtained in step S2, place it in an oven at 50 °C for gelation. After gelation, age it once at 40 °C for 15 h. After the first aging, put the gel into an organic solvent and treat it repeatedly twice. The treatment time of the organic solvent each time is 30 min. After treatment, wash it three times with deionized water. Then place the gel in a nanocellulose dispersion and age it twice at 50 °C for 15 h to obtain a wet gel. The amounts of nanocellulose and deionized water in the nanocellulose dispersion are 2.8 g and 420 g respectively; S4. Take out the wet gel after the second aging in step S3, wash it three times with deionized water, and then replace it successively three times with 50 wt% ethanol, 80 wt% ethanol, and absolute ethanol. The replacement time for each time is 6 h. Place it in a mixed solution of n-hexane, trimethylsilane, and absolute ethanol with a volume ratio of 8:2:1 for surface modification. The surface modification time is 6 h, and the surface modification temperature is 20 °C to obtain a hydrophobic wet gel; S5. Dry the hydrophobic wet gel obtained in step S4 at 60 °C, 90 °C, 120 °C, and 150 °C successively under normal pressure for 2 h to obtain a silicon-aluminum aerogel; the density of this aerogel is 0.124 g / cm 3 , the thermal conductivity is 0.032 W / (m·K), the specific surface area is 658.8 m 2 / g, and the hydrophobic angle is 139°.

[0022] Example 3 S1. Uniformly mix the coal gangue powder obtained by crushing, grinding, and passing through a 300-mesh sieve of 24.6 g of coal gangue and 12.3 g of alkaline solid (sodium carbonate), and place it in a muffle furnace for calcination activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace is 1000 °C, and the calcination time is 3.0 h; S2. Mix the 22.4 g of alkali-fused powder obtained in step S1 and 134.4 g of deionized water in proportion and stir for 30 min. Then add 5.6 g of 7 mol / L hydrochloric acid solution and treat for 2.5 h. After the reaction is complete, perform vacuum filtration. The filtered solution is the silicon-aluminum solution; S3, adding 0.75g of polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in a 50°C oven for gelation, aging the solution at 40°C for 20h, placing the solution in an organic solvent for repeated treatment twice after aging, and washing the solution with deionized water three times after treatment; placing the solution in a nanocellulose dispersion for 15h at 50°C to obtain a wet gel, wherein the amounts of nanocellulose and deionized water in the nanocellulose dispersion are 1.12g and 168g, respectively; S4, taking out the wet gel after the secondary aging in step S3, washing it with deionized water three times, and then replacing it with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol three times in sequence, each replacement time is 6 hours, placing it in a mixed solution of n-hexane, trimethylsilane and anhydrous ethanol with a volume ratio of 8:2:1 for surface modification, the surface modification time is 48 hours, the surface modification temperature is 60°C, and a hydrophobic wet gel is obtained; S5, drying the hydrophobic wet gel obtained in step S4 at 60°C, 90°C, 120°C, and 150°C at normal pressure for 2 hours in sequence to obtain a silica-alumina aerogel; the density of the aerogel is 0.154 g / cm 3 , thermal conductivity is 0.045W / (m·K), specific surface area is 570.6m 2 / g, and the hydrophobic angle is 138°.

[0023] Example 4 A method for preparing high temperature resistant silicon-alumina aerogel by using coal gangue in one step, comprising the following steps: S1. 24.6 g of coal gangue powder obtained by crushing, grinding and passing through a 200-mesh sieve and 13.6 g of alkaline solid (sodium hydroxide) mixture are uniformly mixed, and the mixture is placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace is 850° C. and the calcination time is 1.8 h. S2, 22.4g of the alkali-fused powder obtained in step S1 and 134.4g of deionized water were mixed and stirred in proportion for 20min, and then 7.6g of 4mol / L hydrochloric acid solution was added and treated for 1.2h. After the reaction was complete, vacuum filtration was performed, and the solution obtained by filtration was a silicon-aluminum solution; S3. Add 1.24 g of polystyrene-coated zirconia particles to the silicon-aluminum solution obtained in step S2, place it in an oven at 50 °C for gelation. After gelation, age it once at 40 °C for 20 h. After the first aging, put the gel into an organic solvent and treat it repeatedly twice. The treatment time of the organic solvent each time is 50 min. After the treatment, wash it three times with deionized water; then place the gel in a nanocellulose dispersion and age it twice at 50 °C for 13 h to obtain a wet gel. The amounts of nanocellulose and deionized water in the nanocellulose dispersion are 1.5 g and 225 g respectively; S4. Take out the wet gel after the second aging in step S3, wash it three times with deionized water, and then replace it three times successively with 50 wt% ethanol, 80 wt% ethanol and absolute ethanol. The replacement time each time is 6 h. Place it in a mixed solution of n-hexane, trimethylsilane and absolute ethanol with a volume ratio of 8:2:1 for surface modification. The surface modification time is 30 h and the surface modification temperature is 35 °C to obtain a hydrophobic wet gel; S5. Dry the hydrophobic wet gel obtained in step S4 at 60 °C, 90 °C, 120 °C and 150 °C successively under normal pressure for 2 h to obtain a silicon-aluminum aerogel; the density of the aerogel is 0.114 g / cm 3 , the thermal conductivity is 0.035 W / (m·K), the specific surface area is 587.4 m 2 / g, and the hydrophobic angle is 140°.

[0024] The organic solvent in step S3 of the above embodiment is a mixed solution of N,N-dimethylformamide, tetrahydrofuran and deionized water. The volume ratio between N,N-dimethylformamide, tetrahydrofuran and deionized water is 1:3:2.5. The amount of the organic solvent is more than 5 times the volume of the gel formed after the first aging.

[0025] The polystyrene-coated zirconia particles in step S3 of the above embodiment are treated with concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 1:3 for 45 min. The concentration of the concentrated sulfuric acid is 95 wt%, the concentration of the concentrated nitric acid is 68 wt%, and the total mass of the concentrated nitric acid and concentrated sulfuric acid is 10 times the mass of the polystyrene-coated zirconia particles; the hydrophilicity of the polystyrene is enhanced by the treatment with concentrated nitric acid and concentrated sulfuric acid, and the dispersion ability of the polystyrene-coated zirconia particles in the gel is improved.

[0026] The preparation of the polystyrene-coated zirconia particles in the above embodiment is carried out through the following steps: Disperse polystyrene particles into a mixed solution of absolute ethanol and acetonitrile with a volume ratio of 4:1. The mass ratio between the polystyrene particles and the mixed solution of absolute ethanol and acetonitrile is 1:600. Then add deionized water. The volume ratio between the deionized water and acetonitrile is 1:8 to obtain a polystyrene dispersion; add zirconium isopropoxide to a mixed solution of absolute ethanol and acetonitrile with a volume ratio of 5:1 to obtain a zirconium isopropoxide dispersion. The mass ratio between the zirconium isopropoxide and the mixed solution of absolute ethanol and acetonitrile is 1:25; add the zirconium isopropoxide dispersion to the polystyrene dispersion. The volume ratio between the zirconium isopropoxide dispersion and the polystyrene dispersion is 2:1. After stirring and reacting for 12 h, centrifuge to obtain zirconia particles coated with polystyrene.

[0027] In step S4 of the above embodiment, it is replaced three times successively with 50wt% ethanol, 80wt% ethanol, and absolute ethanol. The volumes of the 50wt% ethanol, 80wt% ethanol, and absolute ethanol used are more than 3 times the volume of the wet gel; the volume of the mixed solution of n-hexane, trimethylsilane, and absolute ethanol used as the modification liquid is more than 5 times the volume of the wet gel.

[0028] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the zirconia particles coated with polystyrene used in step S3 are changed to directly add nano-zirconia with a particle size of 50 nm, and the remaining steps are exactly the same as those in Example 1.

[0029] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the zirconia particles coated with polystyrene used in step S3 are changed to directly add nano-zirconia with a particle size of 200 nm, and the remaining steps are exactly the same as those in Example 1.

[0030] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the zirconia particles coated with polystyrene used in step S3 are changed to directly add nano-zirconia with a particle size of 500 nm, and the remaining steps are exactly the same as those in Example 1.

[0031] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the zirconia particles coated with polystyrene added in step S3 are completely cancelled, and the remaining steps are exactly the same as those in Example 1.

[0032] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the nano-cellulose dispersion in step S3 is changed to deionized water, and the remaining steps are exactly the same as those in Example 1.

[0033] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the treatment process of polystyrene-coated zirconia particles in concentrated nitric acid and concentrated sulfuric acid was cancelled, and the remaining steps were exactly the same as those in Example 1.

[0034] A total of 10 groups of silica-alumina aerogels were prepared through Examples 1-4 and Comparative Examples 1-6 above. The compressive stress and tensile strength of these 10 groups of silica-alumina aerogels were tested, and the test results are shown in Table 1 below: Table 1: Tensile strength test table of 10 groups of aerogels prepared in Examples 1-4 and Comparative Examples 1-6

[0035] From Table 1 above, it can be clearly seen that the tensile strength of Comparative Examples 1-3 decreased significantly compared with that of Example 1, indicating that when zirconia is dispersed into the gel through polystyrene coating, compared with directly dispersing zirconia, nanoscale zirconia as a rigid core can provide more strength for the aerogel; in Comparative Example 5, due to the lack of addition of nanocellulose, the strength of the aerogel decreased; in Comparative Example 6, after the polystyrene-coated zirconia particles were treated without the mixed solution of concentrated nitric acid and concentrated sulfuric acid, the hydrophilicity decreased, and their dispersion in the gel was affected, resulting in a decrease in strength.

[0036] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-temperature resistant silica-alumina aerogel by a one-step method using coal gangue, characterized in that, It includes the following steps: S1. Uniformly mix the coal gangue powder obtained by crushing, grinding, and sieving coal gangue with an alkaline solid mixture, and place it in a muffle furnace for calcination activation to obtain an alkali-fused powder; S2. Mix the alkali-fused powder obtained in step S1 with deionized water in a certain proportion and stir for 10 - 30 min, then add a hydrochloric acid solution. After the reaction is complete, perform vacuum filtration. The filtered solution is a silicon-aluminum solution; S3. Add polystyrene-coated zirconia particles to the silicon-aluminum solution obtained in step S2, place it in an oven at 50 °C for gelation. After gelation, perform primary aging. After primary aging, the gel is repeatedly treated twice in an organic solvent, and then washed three times with deionized water. Again, place the gel in a nanofibrillated cellulose dispersion for secondary aging to obtain a wet gel; S4. Take out the wet gel after secondary aging in step S3, wash it three times with deionized water, then replace it three times successively with 50 wt% ethanol, 80 wt% ethanol, and absolute ethanol. Place it in a mixed solution of n-hexane, trimethylsilane, and absolute ethanol for surface modification to obtain a hydrophobic wet gel; S5. Perform atmospheric drying on the hydrophobic wet gel obtained in step S4 to obtain a silicon-aluminum aerogel.

2. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, characterized in that In step S1, after the coal gangue is crushed and ground, it is sieved through a 100 - 300 mesh sieve; the calcination temperature in the muffle furnace is 700 - 1000 °C, and the calcination time is 0.5 - 3.0 h.

3. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, characterized in that, In step S1, the alkaline solid is one of sodium carbonate, sodium hydroxide, and calcium carbonate; the mass ratio of the coal gangue powder to the alkaline solid is (1.5 - 2):

1.

4. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, characterized in that, In step S2, the mass ratio of the alkali-fused powder to deionized water is 1:6; the concentration of the hydrochloric acid solution is 3 - 7 mol / L, the mass ratio of the hydrochloric acid solution to the alkali-fused powder is (2 - 4):1, and the treatment time of the hydrochloric acid solution is 0.5 - 2.5 h.

5. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, characterized in that, In step S3, the temperature of the primary aging is 40 °C, and the time of the primary aging is 15 - 20 h; the treatment time of the gel with the organic solvent each time after primary aging is 30 - 60 min; the temperature of the secondary aging is 50 °C, and the time of the secondary aging is 10 - 15 h.

6. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 5, characterized in that, The organic solvent in step S3 is a mixed solution of N,N-dimethylformamide, tetrahydrofuran, and deionized water, and the volume ratio of N,N-dimethylformamide, tetrahydrofuran, and deionized water is 1:3:2.

5.

7. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, characterized in that, In step S3, the mass ratio of the polystyrene-coated zirconia particles to the alkali-fused powder used in step S2 is 1:(15 - 30); the polystyrene-coated zirconia particles in step S3 are treated with a concentrated sulfuric acid and concentrated nitric acid mixture with a volume ratio of 1:3 for 45 min.

8. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, wherein In step S3, the mass ratio of the nanofibrillated cellulose to deionized water in the nanofibrillated cellulose dispersion is 1:150; the mass ratio of the used nanofibrillated cellulose to the alkali-fused powder used in step S2 is 1:(8 - 20).

9. The method for preparing a high-temperature resistant silica-alumina aerogel by a one-step method using coal gangue according to claim 1, characterized in that, In step S4, the replacement time for each of the three replacements is 6 h; the volume ratio of n-hexane, trimethylsilane, and absolute ethanol is 8:2:1; the surface modification time is 6 - 48 h, and the surface modification temperature is 20 - 60 °C.

10. The method for preparing high-temperature resistant silica-alumina aerogel by one-step using coal gangue according to claim 1, characterized in that, The atmospheric drying in step S5 is successively carried out at 60°C, 90°C, 120°C, and 150°C for 2 hours under atmospheric pressure.

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