A method for preparing high-temperature resistant silicon-aluminum aerogel using coal gangue in one step

Abstract

The present invention relates to the technical field of silica-alumina aerogel preparation, specifically a method for preparing high-temperature resistant silica-alumina aerogel using coal gangue in a one-step process, comprising the following steps: S1, crushing, grinding, and screening the coal gangue, mixing it with an alkaline solid, and then calcining it to obtain an alkali-fused powder; S2, treating the alkali-fused powder with an acid, and filtering it to obtain a silica-alumina solution; S3, adding polystyrene-coated zirconium oxide particles to the silica-alumina solution, and successively undergoing gelation, primary aging, solvent washing, water washing, and secondary aging; S4, washing, replacing, and modifying the gel; S5, drying the hydrophobic wet gel obtained in step S4 at normal pressure to obtain a silica-alumina aerogel. The silica-alumina aerogel prepared by the present invention has low density, good thermal stability, high specific surface area, strong hydrophobicity, and high strength.

Description

Technical Field

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

[0002] Aerogel is a lightweight nano-solid material with nano-scale solid phase and void structure. It is often used as a thermal insulation material in many fields such as aerospace. Aerogel has a very low density, which can reach as low as 0.16mg / cm -3 . The thermal conductivity of aerogel is extremely low. At room temperature and pressure, the thermal conductivity of aerogel is generally less than 0.02W / (m·K), while it can be as low as 0.004W / (m·K) under vacuum conditions. In addition, aerogel has excellent properties such as high specific surface area, light transmittance and strong hydrophobicity. Therefore, aerogel can be used as an excellent thermal insulation material. It can almost block the three modes of heat transfer: heat conduction, heat convection and heat radiation. The pore size in aerogel is between 1-100nm, which can effectively prevent the flow of air. The raw materials currently used to produce silicon and aluminum aerogels are usually ethyl orthosilicate, methyltriethoxysilane, aluminum chloride hexahydrate and industrial water glass. These raw materials, especially silanes, are relatively expensive, and some raw materials are highly toxic. The preparation process mostly involves preparing two solutions of silicon and aluminum separately and mixing them for use, which is a complicated process. In addition, the supercritical drying equipment used for drying is costly, the process is complex and dangerous, which restricts its large-scale commercial production and application. Studies have shown that the addition of aluminum elements weakens the structural collapse tendency of SiO2-Al2O3 aerogel after heat treatment compared with SiO2 aerogel, increases the specific surface area, and reduces the bulk density. The increase in aluminum content can improve the thermal stability of the aerogel.

[0003] Gangue is a waste and byproduct generated during coal mining and processing. Large piles of gangue occupy a significant amount of land, polluting surrounding land and water bodies. Furthermore, the escape or leaching of sulfides from gangue can pollute the atmosphere. Therefore, the treatment and comprehensive utilization of gangue are crucial during coal mining and utilization to reduce environmental pollution and resource waste. Gangue contains significant amounts of silicon and aluminum, with SiO2 content reaching 40-65% and Al2O3 content reaching 15-45%. Therefore, using gangue as a raw material to prepare aerogels, whether ultra-light silica aerogels or silica-alumina composite aerogels, not only reduces production costs compared to producing chemical products such as alumina and water glass from organic raw materials, but also achieves environmental protection in mining areas and energy conservation and emission reduction.

[0004] At present, the main method of preparing aerogel from coal gangue is to extract silicon and aluminum from the gangue to prepare SiO2 aerogel or SiO2-Al2O3 aerogel. However, the aerogel preparation method still has the following disadvantages: (1) In the traditional process of preparing SiO2-Al2O3 aerogel, the extraction of silicon and aluminum from the gangue is mainly through the reaction of acid and alkali with the raw materials to obtain silicon and aluminum solutions respectively, and then mixing them to prepare silicon-aluminum aerogel. The process is complicated and the cost is high; (2) In the process of preparing SiO2-Al2O3 aerogel, there is a lack of additives, and the strength of the prepared SiO2-Al2O3 aerogel is not high enough. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing high-temperature resistant silica-alumina aerogel using coal gangue in one step, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing high-temperature resistant silicon-alumina aerogel using coal gangue in one step comprises the following steps:

[0008] S1, uniformly mixing the gangue powder obtained by crushing, grinding and screening the gangue with the alkaline solid mixture, placing the mixture in a muffle furnace for calcination and activation to obtain an alkali-fused powder;

[0009] S2, the alkali-fused powder obtained in step S1 and deionized water are mixed in proportion and stirred for 10-30 minutes, and then hydrochloric acid solution is added. After the reaction is complete, vacuum filtration is performed to obtain a solution obtained by filtration to obtain a silicon-aluminum solution;

[0010] S3, adding polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in an oven at 50°C for gelation, and performing a first aging process. After the first aging process, the gel is placed in an organic solvent and repeatedly treated twice. After the treatment, the gel is washed three times with deionized water. The gel is again placed in a nanocellulose dispersion for a second aging process to obtain a wet gel.

[0011] S4, taking out the wet gel after the secondary aging in step S3, washing it three times with deionized water, then replacing it three times with 50 wt % ethanol, 80 wt % ethanol and anhydrous ethanol in sequence, and placing it in a mixed solution of n-hexane, trimethylsilane and anhydrous ethanol for surface modification to obtain a hydrophobic wet gel (hydrophobic SiO2-Al2O3 wet gel);

[0012] S5. Drying the hydrophobic wet gel obtained in step S4 at normal pressure to obtain a silicon-aluminum aerogel (SiO2-Al2O3 aerogel).

[0013] Furthermore, in step S1, the coal gangue is crushed and ground and then passed 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.

[0014] Furthermore, in step S1, the alkaline solid is one of sodium carbonate, sodium hydroxide, and calcium carbonate; and the mass ratio of the gangue powder to the alkaline solid is (1.5-2):1.

[0015] Furthermore, 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 hydrochloric acid solution treatment time is 0.5-2.5 h.

[0016] Furthermore, in step S3, the primary aging temperature is 40° C., and the primary aging time is 15-20 h; the gel after the primary aging is treated with an organic solvent for 30-60 min each time; the secondary aging temperature is 50° C., and the secondary aging time is 10-15 h.

[0017] Furthermore, 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.

[0018] Furthermore, 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 concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3 for 45 minutes.

[0019] Furthermore, the mass ratio of the nanocellulose to deionized water in the nanocellulose dispersion in step S3 is 1:150; and the mass ratio of the nanocellulose to the alkali-fused powder used in step S2 is 1:(8-20).

[0020] Furthermore, the time for each of the three replacements in step S4 is 6 hours; the volume ratio of n-hexane, trimethylsilane and anhydrous ethanol is 8:2:1; the time for surface modification is 6-48 hours, and the temperature for surface modification is 20-60°C.

[0021] Furthermore, the normal pressure drying in step S5 is carried out by drying at 60° C., 90° C., 120° C., and 150° C. in sequence for 2 h.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention realizes a one-step preparation of silicon-aluminum aerogel by using solid waste such as coal gangue, thereby reducing the raw material cost of the material, simplifying the process, and improving the high-value utilization of silicon and aluminum elements in the coal gangue; the atmospheric pressure drying method adopted for drying is more economical and safer than the supercritical drying method commonly used in industry; the obtained aerogel has low density, good thermal stability, high specific surface area and strong hydrophobicity; the SiO2-Al2O3 aerogel prepared by the present invention effectively improves the disadvantage of low operating temperature and improves high-temperature stability compared to SiO2 aerogel.

[0024] 2. In the present invention, polystyrene-coated zirconia particles are dispersed and added during the primary aging process. The polystyrene-coated zirconia increases the volume of the zirconia, facilitating its dispersion. The polystyrene is eventually removed by the organic solvent, leaving nanoscale zirconia as a rigid core, thereby increasing the strength of the aerogel. Furthermore, the polystyrene-coated zirconia removes the polystyrene shell, leaving a richer pore structure within the gel.

[0025] 3. During the secondary aging process of the present invention, in the dispersion containing nanocellulose, nanocellulose is more easily incorporated into the gel having a rich pore structure, combined with the silicon-aluminum network, and combined with zirconium oxide as a rigid core, further improving the strength of the prepared aerogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart for preparing silica-alumina aerogel according to the present invention;

[0027] Figure 2 Graph showing the hydrophobic properties of the silica-alumina aerogel in Example 1 of the present invention;

[0028] Figure 3 This is a microstructure diagram of the silica-alumina aerogel in Example 1 of the present invention;

[0029] Figure 4 This is a physical picture of the silica-alumina aerogel in Example 1 of the present invention;

[0030] Figure 5 These are the appearance pictures of Example 1 of the present invention and SiO2 aerogel after calcination at 800°C for 2h ((a) is SiO2 aerogel, (b) is aerogel prepared in Example 1). DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] See also Figures 1 to 5 , the present invention provides:

[0033] Example 1

[0034] A method for preparing high-temperature resistant silicon-alumina aerogel using coal gangue in one step comprises the following steps:

[0035] S1. 24.6 g of coal gangue powder obtained by crushing, grinding, and passing through a 200-mesh sieve was uniformly mixed with a mixture of 15.2 g of alkaline solid (sodium hydroxide), and the mixture was placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace was 900° C. and the calcination time was 2.2 h.

[0036] 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 to obtain a silica-alumina solution;

[0037] S3, adding 0.89g of polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in an oven at 50°C to allow 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 lasting 45min, and washing the solution with deionized water three times after treatment; placing the solution in a nanocellulose dispersion for a second 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;

[0038] S4, taking out the wet gel after the secondary aging in step S3, washing it three times with deionized water, and then replacing it three times with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol 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, and the surface modification temperature is 45°C to obtain a hydrophobic wet gel;

[0039] 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 h in sequence to obtain a silica-alumina aerogel; the density of the aerogel 3 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°.

[0040] Example 2

[0041] A method for preparing high-temperature resistant silicon-alumina aerogel using coal gangue in one step comprises the following steps:

[0042] S1. 24.6 g of coal gangue powder obtained by crushing, grinding, and passing through a 100-mesh sieve was uniformly mixed with a mixture of 16.4 g of alkaline solid (calcium carbonate), and the mixture was placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace was 700° C. and the calcination time was 0.5 h.

[0043] S2, 22.4g of alkali-fused powder obtained in step S1 and 134.4g of deionized water were mixed in proportion and stirred for 10min, and then 11.2g of 3mol / L hydrochloric acid solution was added and treated for 0.5h. After the reaction was complete, vacuum filtration was performed to obtain a silica-alumina solution;

[0044] S3, adding 1.49g of polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in an oven at 50°C to gel, aging the solution at 40°C for 15h, placing the solution in an organic solvent for repeated treatment twice after aging, with each treatment lasting 30min, and washing the solution with deionized water three times after treatment; placing the solution in a nanocellulose dispersion for a second aging at 50°C for 15h to obtain a wet gel, wherein the amounts of nanocellulose and deionized water in the nanocellulose dispersion are 2.8g and 420g, respectively;

[0045] S4, taking out the wet gel after the secondary aging in step S3, washing it three times with deionized water, and then replacing it three times with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol 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 6 hours, and the surface modification temperature is 20°C to obtain a hydrophobic wet gel;

[0046] S5. Dry the hydrophobic wet gel obtained in step S4 at 60°C, 90°C, 120°C, and 150°C at normal pressure for 2 h to obtain a silica-alumina aerogel; the density of the aerogel is 0.124 g / cm 3 , thermal conductivity is 0.032W / (m·K), specific surface area is 658.8m 2 / g, and the hydrophobic angle is 139°.

[0047] Example 3

[0048] S1. 24.6 g of coal gangue powder obtained by crushing, grinding, and passing through a 300-mesh sieve was uniformly mixed with a mixture of 12.3 g of alkaline solid (sodium carbonate), and the mixture was placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace was 1000° C. and the calcination time was 3.0 h.

[0049] 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 30min, and then 5.6g of 7mol / L hydrochloric acid solution was added and treated for 2.5h. After the reaction was complete, vacuum filtration was performed to obtain a silica-alumina solution;

[0050] S3, adding 0.75g of polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in an oven at 50°C to gel, 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 a second time at 50°C for 15h to obtain a wet gel, wherein the amounts of nanocellulose and deionized water in the nanocellulose dispersion are 1.12g and 168g, respectively;

[0051] S4, taking out the wet gel after the secondary aging in step S3, washing it three times with deionized water, and then replacing it three times with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol in sequence, each replacement time is 6 hours, and 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, and the surface modification temperature is 60°C to obtain a hydrophobic wet gel;

[0052] S5. Dry the hydrophobic wet gel obtained in step S4 at 60°C, 90°C, 120°C, and 150°C at normal pressure for 2 h 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°.

[0053] Example 4

[0054] A method for preparing high-temperature resistant silicon-alumina aerogel using coal gangue in one step comprises the following steps:

[0055] S1. 24.6 g of coal gangue powder obtained by crushing, grinding, and passing through a 200-mesh sieve was uniformly mixed with a mixture of 13.6 g of alkaline solid (sodium hydroxide), and the mixture was placed in a muffle furnace for calcination and activation to obtain an alkali-fused powder. The calcination temperature in the muffle furnace was 850° C. and the calcination time was 1.8 h.

[0056] S2, 22.4g of 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 to obtain a silica-alumina solution;

[0057] S3, adding 1.24g of polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in an oven at 50°C to gel, aging the solution at 40°C for 20h, placing the solution in an organic solvent for repeated treatment twice after aging, each treatment time of the organic solvent being 50min, and washing the solution with deionized water three times after treatment; placing the solution in a nanocellulose dispersion for a second aging at 50°C for 13h to obtain a wet gel, wherein the amounts of nanocellulose and deionized water in the nanocellulose dispersion are 1.5g and 225g, respectively;

[0058] S4, taking out the wet gel after the secondary aging in step S3, washing it three times with deionized water, and then replacing it three times with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol in sequence, each replacement time is 6 hours, and 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 30 hours, and the surface modification temperature is 35°C to obtain a hydrophobic wet gel;

[0059] S5. Dry the hydrophobic wet gel obtained in step S4 at 60°C, 90°C, 120°C, and 150°C at normal pressure for 2 h to obtain a silica-alumina aerogel; the density of the aerogel is 0.114 g / cm 3 , thermal conductivity is 0.035W / (m·K), specific surface area is 587.4m 2 / g, and the hydrophobic angle is 140°.

[0060] 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 of N,N-dimethylformamide, tetrahydrofuran and deionized water is 1:3:2.5, and the amount of organic solvent used is more than 5 times the volume of the gel formed after one aging.

[0061] In step S3 of the above embodiment, the polystyrene-coated zirconia particles are treated with concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3 for 45 minutes, the concentration of concentrated sulfuric acid is 95wt%, the concentration of concentrated nitric acid is 68wt%, and the total mass of concentrated nitric acid and concentrated sulfuric acid is 10 times the mass of the polystyrene-coated zirconia particles; the hydrophilicity of the polystyrene treated with concentrated nitric acid and concentrated sulfuric acid is enhanced, thereby improving the dispersion ability of the polystyrene-coated zirconia particles in the gel.

[0062] The preparation of the polystyrene-coated zirconium oxide particles in the above embodiment is carried out by the following steps:

[0063] Polystyrene particles are dispersed in a mixed solution of anhydrous ethanol and acetonitrile in a volume ratio of 4:1, and the mass ratio between the polystyrene particles and the mixed solution of anhydrous ethanol and acetonitrile is 1:600. Then, deionized water is added, and the volume ratio between the deionized water and acetonitrile is 1:8 to obtain a polystyrene dispersion. Zirconium isopropoxide is added to a mixed solution of anhydrous ethanol and acetonitrile in a volume ratio of 5:1 to obtain a zirconium isopropoxide dispersion, and the mass ratio between the zirconium isopropoxide and the mixed solution of anhydrous ethanol and acetonitrile is 1:25. The zirconium isopropoxide dispersion is added to the polystyrene dispersion, and the volume ratio between the zirconium isopropoxide dispersion and the polystyrene dispersion is 2:1. After stirring for 12 hours, the mixture is centrifuged to obtain polystyrene-coated zirconium oxide particles.

[0064] In step S4 of the above embodiment, the gel is replaced three times in sequence with 50 wt% ethanol, 80 wt% ethanol, and anhydrous ethanol. The volumes of 50 wt% ethanol, 80 wt% ethanol, and anhydrous ethanol used are more than 3 times the volume of the wet gel. The volume of the mixed solution of n-hexane, trimethylsilane, and anhydrous ethanol used as the modifying liquid is more than 5 times the volume of the wet gel.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 1 is that the polystyrene-coated zirconia particles used in step S3 are replaced by directly adding nano-zirconia, and the particle size of the nano-zirconia is 50 nm. The remaining steps are exactly the same as in Example 1.

[0067] Comparative Example 2

[0068] The difference between Comparative Example 2 and Example 1 is that the polystyrene-coated zirconia particles used in step S3 are replaced by directly adding nano-zirconia with a particle size of 200 nm. The remaining steps are exactly the same as those in Example 1.

[0069] Comparative Example 3

[0070] The difference between Comparative Example 3 and Example 1 is that the polystyrene-coated zirconia particles used in step S3 are replaced by directly adding nano-zirconia with a particle size of 500 nm. The remaining steps are exactly the same as in Example 1.

[0071] Comparative Example 4

[0072] The difference between Comparative Example 4 and Example 1 is that the polystyrene-coated zirconia particles added in step S3 are completely omitted, and the remaining steps are exactly the same as those in Example 1.

[0073] Comparative Example 5

[0074] The difference between Comparative Example 5 and Example 1 is that the nanocellulose dispersion in step S3 is changed to deionized water, and the remaining steps are exactly the same as in Example 1.

[0075] Comparative Example 6

[0076] The difference between Comparative Example 6 and Example 1 is that the treatment process of the polystyrene-coated zirconia particles in concentrated nitric acid and concentrated sulfuric acid is omitted, and the remaining steps are exactly the same as those in Example 1.

[0077] Ten groups of silica-alumina aerogels were prepared through the above Examples 1-4 and Comparative Examples 1-6. The compressive stress and tensile strength of the ten groups of silica-alumina aerogels were tested. The test results are shown in Table 1 below:

[0078] Table 1: Tensile strength test table of 10 groups of aerogels prepared in Examples 1-4 and Comparative Examples 1-6

[0079]

[0080] From Table 1 above, it can be clearly seen that the tensile strength of Comparative Examples 1-3 is significantly reduced compared to that of Example 1, indicating that after the polystyrene-coated zirconia is dispersed into the gel, the nano-scale zirconia as a rigid core can provide more strength to the aerogel compared to directly dispersing the zirconia; and in Comparative Example 5, the strength of the aerogel decreases due to the lack of the addition of nanocellulose; in Comparative Example 6, the hydrophilicity of the polystyrene-coated zirconia particles decreases after the lack of treatment with a mixed solution of concentrated nitric acid and concentrated sulfuric acid, which affects their dispersion in the gel and reduces their strength.

[0081] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-temperature resistant silicon-alumina aerogel using coal gangue in one step, characterized in that: The following steps are involved: S1, uniformly mixing the gangue powder obtained by crushing, grinding and screening the gangue with the alkaline solid mixture, placing the mixture in a muffle furnace for calcination and activation to obtain an alkali-fused powder; S2, the alkali-fused powder obtained in step S1 and deionized water are mixed in proportion and stirred for 10-30 minutes, and then hydrochloric acid solution is added. After the reaction is complete, vacuum filtration is performed to obtain a solution obtained by filtration to obtain a silicon-aluminum solution; S3, adding polystyrene-coated zirconium oxide particles to the silica-alumina solution obtained in step S2, placing the solution in an oven at 50°C for gelation, and performing a first aging process. After the first aging process, the gel is placed in an organic solvent and repeatedly treated twice. After the treatment, the gel is washed three times with deionized water. The gel is again placed in a nanocellulose dispersion for a second aging process to obtain a wet gel. S4, taking out the wet gel after the secondary aging in step S3, washing it three times with deionized water, then replacing it three times with 50wt% ethanol, 80wt% ethanol and anhydrous ethanol in sequence, and placing it in a mixed solution of n-hexane, trimethylsilane and anhydrous ethanol for surface modification to obtain a hydrophobic wet gel; S5. Drying the hydrophobic wet gel obtained in step S4 at normal pressure to obtain silica-alumina aerogel.

2. The method for preparing high temperature resistant silicon aluminum aerogel by using coal gangue in one step according to claim 1, characterized in that: In step S1, the coal gangue is crushed and ground and then passed 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 silicon aluminum aerogel by using coal gangue in one step 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 gangue powder to the alkaline solid is (1.5-2):

1.

4. The method for preparing high temperature resistant silicon aluminum aerogel by using coal gangue in one step according to claim 1, characterized in that: In step S2, the mass ratio of the alkali-fused powder to the 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 hydrochloric acid solution treatment time is 0.5-2.5 h.

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

6. The method for preparing high temperature resistant silicon aluminum aerogel by using coal gangue in one step 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 silicon aluminum aerogel by using coal gangue in one step according to claim 1, characterized in that: 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 concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3 for 45 minutes.

8. The method for preparing high temperature resistant silicon aluminum aerogel by using coal gangue in one step according to claim 1, characterized in that: The mass ratio of the nanocellulose to deionized water in the nanocellulose dispersion in step S3 is 1:150; the mass ratio of the nanocellulose to the alkali-fused powder in step S2 is 1:(8-20).

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

10. The method for preparing high temperature resistant silicon aluminum aerogel by using coal gangue in one step according to claim 1, characterized in that: The normal pressure drying in step S5 is carried out by drying at 60° C., 90° C., 120° C., and 150° C. in sequence for 2 hours.

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