A method for preparing low-cost low thermal conductivity aerogel by coal spontaneous combustion

Abstract

The application provides a method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion, and relates to the technical field of low-cost aerogel preparation. The method is as follows: firstly, siloxane is hydrolyzed to obtain a silane hydrolysis solution; then, the unburned coal is modified by using the silane hydrolysis solution as a glue adhesive, so that the coal particles are mutually adhered to form a coal product; and then, the coal product is fully combusted in oxygen or air, wherein the combustible carbon leaves a hole after combustion, and the incombustible silicon dioxide and the glue adhesive jointly form the aerogel with low thermal conductivity and high compressive strength. The coal raw material of the application has low cost compared with traditional carbon aerogel powder, the siloxane can be selected from components with wide sources and low cost, the preparation process only needs three steps, the consumption of organic solvents is small, the process flow is simple, the heat energy consumption is small, and the heat energy is derived from the full combustion of the coal, so the method is beneficial to industrial large-scale production and popularization and use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel low-cost preparation, and particularly relates to a method for preparing low-cost low-thermal-conductivity aerogel by using coal self-combustion. BACKGROUND

[0002] At present, the degree and duration of extremely high temperature and extremely low temperature caused by extreme weather are increasing, in order to provide suitable living temperature and maintain the normal service life of buildings, the energy consumption for building heating and cooling is also increasing year by year, so it is urgent to provide a low-cost and large-scale building insulation material to reduce energy consumption and carbon emissions.

[0003] As a new type of insulation material, aerogel has the properties of light weight, low density and low thermal conductivity, and is an ideal insulation material, which can be widely used in many fields of life. There are currently four main methods for preparing aerogel: supercritical drying, subcritical drying, freeze drying and atmospheric drying. However, these preparation methods are either complex and expensive equipment, high energy consumption and high risk, or complicated process, large solvent consumption.

[0004] Chinese patent CN104446334A discloses a preparation method of low-cost carbon aerogel thermal insulation composite material, which uses carbon aerogel powder, dispersant and fiber, and is prepared by stage forming and drying. The raw material cost is high, the stage forming and drying process is complex, and the production cost is high, which is not conducive to large-scale industrial production.

[0005] Chinese patent CN108329046A discloses a preparation method of carbon aerogel thermal insulation composite material. Although the prepared aerogel material has high compressive strength, the atmospheric drying process and carbonization cracking process equipment are expensive, the three-step heating program operation is complex, the solvent consumption is large, the control difficulty is large, the heat energy and production cost are high, and the process cycle is long.

[0006] Chinese patent CN110862258A discloses a bearing type carbon aerogel-porous silica composite material and a preparation method thereof. Block porous silica is added into a carbon aerogel precursor solution to form a gel, and then the composite material is obtained by supercritical drying and carbonization. Obviously, the supercritical drying and carbonization process is complex, the operation cost is high, the control difficulty is large, and the process cycle is long.

[0007] Chinese patent CN1583555A discloses a method for preparing carbon aerogel, which uses resorcinol and formaldehyde as reaction monomers, organic surfactant as emulsifier and catalyst, and water as solvent to obtain organic gel by heating and curing, and then directly natural drying or heating drying to obtain organic aerogel. Obviously, the method uses normal pressure drying method to prepare, consumes more solvent, and the prepared organic aerogel has poor heat resistance.

[0008] Therefore, the limitations of the preparation method of aerogel limit the industrialized large-scale preparation and wide application of aerogel, and a low-cost large-scale preparation method of aerogel is urgently needed. SUMMARY

[0009] The technical problem to be solved by the present application is that the current aerogel preparation method has the technical defects of complex equipment, complicated process, high cost, high consumption of heat energy, complex operation process, large amount of organic solvent consumption, high cost, not suitable for batch production, and the like, and the comprehensive performance of the prepared aerogel such as density, strength, heat insulation and heat resistance is not ideal.

[0010] To solve the above technical problems, the technical solutions of the present application are as follows:

[0011] A method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal, which comprises the following steps: first, obtaining a silane hydrolysate by hydrolyzing siloxane; then, modifying unburned coal with the silane hydrolysate as an adhesive to make the coal particles adhere to each other and form a coal product; and then, fully combusting the coal product in oxygen or air, wherein the combustible carbon leaves holes after combustion, and the incombustible silicon dioxide and the adhesive together form an aerogel with low thermal conductivity and high compressive strength. This method has the characteristics of "one arrow with two targets", that is, on the one hand, it can fully utilize the heat energy of coal, and on the other hand, it directly obtains aerogel after the completion of coal combustion.

[0012] Preferably, the method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal comprises the following specific steps:

[0013] S1, hydrolysis of siloxane

[0014] The components of coal powder and siloxane are selected, the siloxane is added to deionized water, a surfactant and a surfactant aid are added to promote dissolution, and then an acid or a base is added and continuously stirred to initiate the hydrolysis of siloxane, thereby obtaining a siloxane hydrolysate;

[0015] S2, processing of coal

[0016] Mixing the coal powder and siloxane hydrolysis solution in S1, and then aging and drying to obtain a coal processing product;

[0017] S3, Preparation of aerogel

[0018] Igniting the coal processing product in S2 in a fire, and then fully burning to obtain an aerogel.

[0019] Preferably, the siloxane in S1 is at least one of ethyl silicate, sodium silicate, methyl silicate, propyl silicate, methyl trimethoxysilane, methyl triethoxysilane, dimethyl dimethoxysilane, dimethyl diethoxysilane, KH550, KH560, KH570, and other silane products with hydrolyzable siloxane bonds.

[0020] Preferably, the siloxane in S1 is ethyl silicate, and the concentration of ethyl silicate in water can be adjusted in the range of 0.001-0.95 mg / mL.

[0021] Preferably, the surfactant in S1 is at least one of cetyl trimethyl ammonium chloride, cetyl trimethyl ammonium bromide, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.

[0022] Preferably, the surfactant in S1 is cetyl trimethyl ammonium chloride, and the concentration of cetyl trimethyl ammonium chloride can be between 0-1000 mg / ml.

[0023] Preferably, the surfactant auxiliary in S1 is at least one of ethanol, tetrahydrofuran, DMF, DMSO, and methanol.

[0024] Preferably, the surfactant auxiliary in S1 is ethanol, and the concentration of ethanol can be between 0-1000 mg / ml.

[0025] Preferably, the acid in S1 is at least one of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, oxalic acid, citric acid, tannic acid, and other acidic substances that can provide H + .

[0026] Preferably, the acid in S1 is hydrochloric acid, and the concentration of hydrochloric acid can be adjusted in the range of 0-12 mol / L, and the concentration of hydrochloric acid is not 0.

[0027] Preferably, the base in S1 is at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, lithium hydroxide, and ammonia.

[0028] Preferably, the base in S1 is sodium hydroxide, and the concentration of sodium hydroxide can be adjusted in the range of 0-5 mol / L

[0029] Preferably, the ratio of the mixing of the coal powder and the siloxane hydrolysis solution in S2 is 10:0.1-10:10.

[0030] Preferably, the coal processing method in the method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion is simple, stirring at room temperature, and standing and aging, and the time required from the coal processing product to the formation of the aerogel is only 0.5-2 h, and the aerogel is obtained in the process of using the heat of coal combustion, and the preparation cost is greatly reduced compared with the traditional process.

[0031] Preferably, the processed coal contains about 80% carbon elements, and the density is 1.0 g / cm 3 , the specific surface area is 1.3 m 2 / g; the density of the obtained aerogel in S3 is 0.2 g / cm 3 , the component is silicon dioxide, the specific surface area is 9.7 m 2 / g, the compressive strength is not less than 200 kPa, the thermal conductivity is lower than 0.05 W / m·k, and the high temperature resistance is 30-1200 DEG C.

[0032] Compared with the prior art, the technical scheme has at least the following beneficial effects:

[0033] The above scheme provides a method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion, which can solve the technical defects of the prior art, such as high heat consumption, complex operation process, high cost, large amount of organic solvent consumption, long process cycle, and unsuitable for batch production.

[0034] The siloxane is hydrolyzed to obtain a silane hydrolysis solution, the unburned coal is modified by using the silane hydrolysis solution as an adhesive, the coal particles are mutually adhered to form a coal processing product, and then the coal processing product is fully burned in oxygen or air, wherein the combustible carbon leaves a hole after being burned, and the incombustible silicon dioxide and the adhesive jointly constitute the aerogel with low thermal conductivity and certain strength.

[0035] The method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion has a simple coal processing method, stirring at room temperature, standing and aging, and the time required from the coal processing product to the formation of the aerogel is only 0.5-2 h, and the aerogel is obtained in the process of using the heat of coal combustion, and the preparation cost is greatly reduced compared with the traditional process.

[0036] The processed coal contains about 80% carbon elements, and the density is 1.0 g / cm 3 , the specific surface area is 1.3 m 2 / g; the density of the obtained aerogel in S3 is 0.2 g / cm 3 , the component is silicon dioxide, the specific surface area is 9.7 m 2 / g, compressive strength is not less than 200kPa, thermal conductivity is lower than 0.05W / m·k, and can resist high temperature of 30-1200 DEG C.

[0037] In addition, as a comparison, currently most carbon aerogel preparation adopts high-cost carbon aerogel powder, and the present application adopts unprocessed coal, although unprocessed coal obtains coal ash without mechanical strength and cannot form aerogel, but the method does not affect the combustion heat value of coal, and the aerogel appears as a product of coal combustion, does not affect the value of coal itself, so the preparation cost of the aerogel can be greatly reduced.

[0038] In summary, compared with other traditional methods, the present application has the advantages that the coal raw material is low in cost compared with traditional carbon aerogel powder, the siloxane can be selected from components with wide sources and low cost, the preparation process only needs three steps, the consumption of organic solvent is small, the process flow is simple, the heat energy consumed is from the full combustion of coal, the heat energy consumption is small, and the present application is beneficial to industrial large-scale production and popularization and use. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows, obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0040] Figure 1 A schematic diagram of a method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0042] Embodiment 1

[0043] A method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal, as shown in Figure 1 The specific steps of the method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal are as follows:

[0044] S1, hydrolysis of siloxane

[0045] Add 1 g of ethyl silicate into 10 mL of deionized water, add 0.05 g of cetyl trimethyl ammonium chloride and 2 mL of ethanol to promote dissolution, add 100 μL of hydrochloric acid (0.1 mol / L) and stir for 1 h to initiate hydrolysis of siloxane, to obtain a siloxane hydrolysate;

[0046] S2, processing of coal

[0047] Mix coal powder and the siloxane hydrolysate of S1 at a mass ratio of 5:2, then age and dry at room temperature for 22 h to obtain a coal processing product;

[0048] S3, preparation of aerogel

[0049] Place the coal processing product of S2 in a fire to ignite, and fully burn for 2 h to obtain an aerogel.

[0050] The density of the aerogel prepared in this example is 0.2 g / cm 3 , the compressive strength is 230 kPa, the thermal conductivity is 0.036 W / m·k, and it can withstand a high temperature of 1200°C.

[0051] Example 2

[0052] A method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal, as shown in Figure 1 , the specific steps of the method are as follows:

[0053] S1, hydrolysis of siloxane

[0054] Add 4 g of ethyl silicate into 10 mL of deionized water, add 0.05 g of sodium dodecyl sulfate and 2 mL of ethanol to promote dissolution, add 100 μL of hydrochloric acid (0.1 mol / L) and stir for 1 h to initiate hydrolysis of siloxane, to obtain a siloxane hydrolysate;

[0055] S2, processing of coal

[0056] Mix coal powder and the siloxane hydrolysate of S1 at a mass ratio of 5:2, then age and dry at room temperature for 22 h to obtain a coal processing product;

[0057] S3, preparation of aerogel

[0058] Place the coal processing product of S2 in a fire to ignite, and fully burn for 1 h to obtain an aerogel.

[0059] The density of the aerogel prepared in this example is 0.2 g / cm 3 , the compressive strength is 240 kPa, the thermal conductivity is 0.042 W / m·k, and it can withstand a high temperature of 1200°C.

[0060] Example 3

[0061] A method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion, as shown in the figure, the method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion specific steps are as follows: Figure 1

[0062] S1, hydrolysis of siloxane

[0063] 1g methyltrimethoxysilane was added to 10mL deionized water, 0.05g cetyltrimethylammonium chloride and 2mL ethanol were added to promote dissolution, 100μL hydrochloric acid(0.1mol / L) was added and stirred for 0.5h, the hydrolysis of siloxane was initiated, and the siloxane hydrolysate was obtained;

[0064] S2, processing of coal

[0065] The coal powder and the siloxane hydrolysate of S1 were mixed in a mass ratio of 5:2, and then aged in an oven at 60℃ for 8h to obtain a coal processing product;

[0066] S3, preparation of aerogel

[0067] The coal processing product of S2 was ignited in a furnace fire, and after 1h of sufficient combustion, an aerogel was obtained.

[0068] The density of the aerogel prepared in this example was 0.199g / cm 3 , the compressive strength was 260kPa, the thermal conductivity was 0.036W / m·k, and it could withstand high temperature of 1200℃.

[0069] Example 4

[0070] A method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion, as shown in the figure, the method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion specific steps are as follows: Figure 1

[0071] S1, hydrolysis of siloxane

[0072] 1g ethyl silicate was added to 10mL deionized water, 0.05g sodium dodecylbenzenesulfonate and 2mL ethanol were added to promote dissolution, 10μL hydrochloric acid(0.1mol / L) was added and stirred for 1h, the hydrolysis of siloxane was initiated, and the siloxane hydrolysate was obtained;

[0073] S2, processing of coal

[0074] The coal powder and the siloxane hydrolysate of S1 were mixed in a mass ratio of 5:2, and then aged in an oven at 80℃ for 6h to obtain a coal processing product;

[0075] S3, preparation of aerogel ​​

[0076] The coal processing product of S2 is ignited in a fire and after 1h of full combustion, aerogel is obtained.

[0077] The density of the aerogel prepared in this example is 0.205 g / cm 3 , the compressive strength is 210 kPa, the thermal conductivity is 0.045 W / m·k, and it can withstand high temperatures of 1200℃.

[0078] Example 5

[0079] A method for preparing low-cost low-thermal-conductivity aerogel by using coal self-combustion, as shown in the figure, the specific steps of the method are as follows: Figure 1

[0080] S1, hydrolysis of siloxane

[0081] 1 g of ethyl silicate is added to 10 mL of deionized water, 0.05 g of cetyltrimethylammonium chloride and 2 mL of ethanol are added to promote dissolution, 100 μL of nitric acid (0.1 mol / L) is added and stirred for 0.5 h to initiate the hydrolysis of siloxane, and a siloxane hydrolysis solution is obtained;

[0082] S2, processing of coal

[0083] Coal powder and the siloxane hydrolysis solution of S1 are mixed in a mass ratio of 5:2, and then aged and dried at room temperature for 22 h to obtain a coal processing product;

[0084] S3, preparation of aerogel

[0085] The coal processing product of S2 is ignited in a fire and after 2h of full combustion, aerogel is obtained.

[0086] The density of the aerogel prepared in this example is 0.201 g / cm 3 , the compressive strength is 230 kPa, the thermal conductivity is 0.036 W / m·k, and it can withstand high temperatures of 1200℃.

[0087] Example 6

[0088] A method for preparing low-cost low-thermal-conductivity aerogel by using coal self-combustion, as shown in the figure, the specific steps of the method are as follows: Figure 1

[0089] S1, hydrolysis of siloxane

[0090] ​​1 g of ethyl silicate was added to 10 mL of deionized water, 0.05 g of cetyltrimethylammonium bromide and 2 mL of ethanol were added to promote dissolution, 100 μL of sodium hydroxide solution (0.1 mol / L) was added and stirred for 1 h to initiate hydrolysis of siloxane, and a siloxane hydrolysis solution was obtained;

[0091] S2, processing of coal

[0092] The coal powder and the siloxane hydrolysis solution of S1 were mixed in a mass ratio of 5:2, and then dried in an aging oven at 60°C for 8 h to obtain a coal processing product;

[0093] S3, preparation of aerogel

[0094] The coal processing product of S2 was ignited in a fire and burned for 1 h to obtain an aerogel.

[0095] The density of the aerogel prepared in this example was 0.2 g / cm 3 , the compressive strength was 230 kPa, the thermal conductivity was 0.036 W / m·k, and it could withstand a high temperature of 1200°C.

[0096] Example 7

[0097] A method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal, as shown in Figure 1 , the specific steps of the method for preparing low-cost low-thermal-conductivity aerogel by self-combustion of coal are as follows:

[0098] S1, hydrolysis of siloxane

[0099] 1 g of ethyl silicate was added to 10 mL of deionized water, 0.05 g of cetyltrimethylammonium chloride and 2 mL of ethanol were added to promote dissolution, 100 μL of hydrochloric acid (0.1 mol / L) was added and stirred for 1 h to initiate hydrolysis of siloxane, and a siloxane hydrolysis solution was obtained;

[0100] S2, processing of coal

[0101] The coal powder and the siloxane hydrolysis solution of S1 were mixed in a mass ratio of 5:2, and then dried in an aging oven at 60°C for 8 h to obtain a coal processing product;

[0102] S3, preparation of aerogel

[0103] The coal processing product of S2 was ignited in a fire and burned for 2 h to obtain an aerogel.

[0104] The density of the aerogel prepared in this example was 0.198 g / cm 3 , the compressive strength was 230 kPa, the thermal conductivity was 0.036 W / m·k, and it could withstand a high temperature of 1200°C.

[0105] Example 8

[0106] A method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion, as shown in Figure 1 , the method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion has the following specific steps:

[0107] S1, hydrolysis of siloxane

[0108] 1g of ethyl silicate was added to 10mL of deionized water, 0.05g of sodium dodecyl sulfate and 2mL of DMF were added to promote dissolution, 100μL of hydrochloric acid (0.1mol / L) was added and stirred for 1h to initiate the hydrolysis of siloxane, and a siloxane hydrolysis solution was obtained;

[0109] S2, processing of coal

[0110] The coal powder and the siloxane hydrolysis solution of S1 were mixed in a mass ratio of 5:2, and then aged and dried at room temperature for 22h to obtain a coal processing product;

[0111] S3, preparation of aerogel

[0112] The coal processing product of S2 was ignited in a furnace fire, and after 1h of sufficient combustion, an aerogel was obtained.

[0113] The density of the aerogel prepared in this example was 0.2g / cm 3 , the compressive strength was 210kPa, the thermal conductivity was 0.041W / m·k, and it could withstand a high temperature of 1200℃.

[0114] Example 9

[0115] A method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion, as shown in Figure 1 , the method for preparing low-cost low-thermal-conductivity aerogel by using coal spontaneous combustion has the following specific steps:

[0116] S1, hydrolysis of siloxane

[0117] 1g of ethyl silicate was added to 10mL of deionized water, 0.05g of sodium dodecyl sulfate and 2mL of DMF were added to promote dissolution, 100μL of hydrochloric acid (0.1mol / L) was added and stirred for 1h to initiate the hydrolysis of siloxane, and a siloxane hydrolysis solution was obtained;

[0118] S2, processing of coal

[0119] The coal powder and the siloxane hydrolysis solution of S1 were mixed in a mass ratio of 5:2, and then aged and dried at room temperature for 22h to obtain a coal processing product;

[0120] S3, preparation of aerogel

[0121] The coal processing product of S2 is ignited in a fire, and after being fully burned for 2h, aerogel is obtained.

[0122] The density of the aerogel prepared in this embodiment is 0.2g / cm 3 , the compressive strength is 260kPa, the thermal conductivity is 0.046W / m·k, and it can withstand high temperature of 1200℃.

[0123] The above scheme, the present application provides a kind of low-cost low thermal conductivity aerogel prepared by coal spontaneous combustion method, can solve the technical defects of existing aerogel preparation method, such as high heat consumption, complex operation process, difficult control, long process cycle, large consumption of organic solvent, high cost, not suitable for batch production etc.

[0124] The present application obtains silane hydrolysate by hydrolysis of siloxane, and modifies unburned coal with silane hydrolysate as adhesive, so that the coal particles are mutually adhered to form coal processing product, and then the coal processing product is fully burned in oxygen or air, wherein the combustible carbon leaves holes after burning, and the incombustible silicon dioxide and adhesive together constitute aerogel with low thermal conductivity and certain strength.

[0125] The coal processing method in the present application is simple, stirring at room temperature, and aging after standing, and the time required from coal processing product to aerogel is only 0.5-2h, and the aerogel is obtained in the process of utilizing coal combustion heat, so the preparation cost is greatly reduced compared with traditional process.

[0126] The processed coal contains about 80% carbon element, with density of 1.0g / cm 3 , specific surface area of 1.3m 2 / g; the density of the obtained aerogel is 0.2g / cm 3 , the composition is silicon dioxide, the specific surface area is 9.7m 2 / g, the compressive strength is not less than 200kPa, the thermal conductivity is less than 0.05W / m·k, and it can withstand high temperature of 30-1200℃.

[0127] In addition, as a comparison, most of the carbon aerogel powders prepared at present are high-cost, while the present application uses unprocessed coal, although the unprocessed coal produces coal ash without mechanical strength and cannot form aerogel, but this method does not affect the calorific value of coal, and the aerogel appears as a product of coal combustion, which does not affect the value of coal itself, so the preparation cost of aerogel can be greatly reduced.

[0128] In summary, compared with other conventional methods, the coal raw material is low in cost relative to conventional carbon aerogel powder, the siloxane can be selected from a widely-sourced and low-cost component, the preparation process only needs three steps, the consumption of organic solvent is small, the process flow is simple, the thermal energy consumption is small due to the full combustion of coal, and the industrial large-scale production and popularization are facilitated.

[0129] The above is the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for producing low cost, low thermal conductivity aerogels from coal spontaneous combustion, characterized in that, First, a silane hydrolysis solution is obtained by hydrolyzing siloxane; then, the unburned coal is modified by using the silane hydrolysis solution as a glue to make the coal particles adhere to each other, and the coal processing product is formed after aging and drying; the processed coal contains about 80% carbon element, and the density is 1.0 g / cm 3 , the specific surface area is 1.3 m 2 / g; then the coal processing product is fully burned in oxygen or air, wherein the combustible carbon is left with holes after burning, and the incombustible silicon dioxide and the glue together form aerogel with low thermal conductivity and high compressive strength; the density of the obtained aerogel is 0.2 g / cm 3 , the composition is silicon dioxide, the specific surface area is 9.7 m 2 / g, the compressive strength is not less than 200 kPa, and the thermal conductivity is less than 0.05 W / m•k.

2. The method of claim 1, wherein the coal is prepared by a method comprising: The specific steps are as follows: S1, hydrolysis of siloxane The components of coal powder and siloxane are selected, the siloxane is added into deionized water, a surfactant and a surfactant aid are added to promote dissolution, then an acid or a base is added and stirred constantly to initiate the hydrolysis of siloxane, and a siloxane hydrolysis solution is obtained; S2, processing of coal The coal powder and the siloxane hydrolysis solution of S1 are mixed, and then aged and dried to obtain a coal processing product; S3, preparation of aerogel The coal processing product of S2 is ignited in a furnace fire, and after sufficient combustion, an aerogel is obtained.

3. The method of claim 2, wherein the coal is heated to a temperature of 450-550°C. The siloxane in S1 is at least one of ethyl silicate, methyl silicate, propyl silicate, methyl trimethoxysilane, methyl triethoxysilane, dimethyl dimethoxysilane, dimethyl diethoxysilane, KH550, KH560, and KH570.

4. The method of claim 2, wherein the coal is heated to a temperature of 450-550°C. The surfactant in S1 is at least one of cetyl trimethyl ammonium chloride, cetyl trimethyl ammonium bromide, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.

5. The method of claim 2, wherein the coal is heated to a temperature of about 400 °C to about 600 °C. The surfactant aid in S1 is at least one of ethanol, tetrahydrofuran, DMF, DMSO, and methanol.

6. The method of claim 2, wherein the coal is heated to a temperature of about 400 °C to about 600 °C. The acid in S1 is at least one of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, oxalic acid, citric acid, and tannic acid.

7. The method of claim 2, wherein the coal is heated to a temperature of about 400 °C to about 600 °C. The base in S1 is at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, lithium hydroxide, and ammonia.

8. The method of claim 2, wherein the coal is heated to a temperature of about 400 °C to about 600 °C. The mass ratio of the mixing of the coal powder and the siloxane hydrolysis solution in S2 is 10:0.1-10:

10.

9. The method of claim 2, wherein the coal is heated to a temperature of about 400°C to about 600°C. The processing of coal is stirred at room temperature, and the coal processing product is obtained by standing and aging. The time required from the coal processing product to the formation of aerogel is only 0.5-2 h, and the aerogel is obtained in the process of utilizing the heat of coal combustion.

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