Sol precursor, silicon dioxide aerogel, heat insulation sheet, and preparation method

Abstract

The present application discloses a sol precursor, a silicon dioxide aerogel, a heat insulation sheet, and a preparation method. The preparation method is used to prepare the sol precursor for preparing the silicon dioxide aerogel. The preparation method comprises: a solution configuration step in which a catalyst is added to solvent under the condition of hydrolysis temperature and stirred evenly to obtain a mixed solution; a sol formation step in which a silicon source and a gel accelerator are added to the mixed solution and the hydrolysis temperature is maintained to perform a hydrolysis reaction to obtain the sol precursor. The hydrolysis temperature is 0-25°C. The solvent comprises alcohol substance, and the mixed solution contains water. The catalyst is an acidic catalyst, and the gel accelerator is an epoxy compound. According to the preparation method of the present application, the whole hydrolysis reaction process is mild and uniform.

Description

SOL PRECURSOR, SILICON DIOXIDE AEROGEL, HEAT INSULATION SHEET, AND PREPARATION METHODCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Chinese Patent Application No. 202410149706.8 filed on February 1, 2024, the disclosure of which is incorporated by reference herein in its entirety.BACKGROUND

[0002] The present application relates to the technical field of composite materials, and specifically to a preparation method of a sol precursor, a silicon dioxide aerogel, a heat insulation sheet, and a preparation method.

[0003] With the continuous development of construction, electronics, chemical industry and national defense and other industries, the requirements for thermal insulation performance of materials are becoming more and more stringent, and the development of porous materials based on thermal insulation materials has gradually received widespread attention. Among them, with its three-dimensional network porous structure and up to 90% porosity, silicon dioxide aerogel can effectively reduce the heat transfer of gas and solid phase and has excellent thermal insulation performance, which has important application prospects in important industrial fields such as machinery production, building insulation, aerospace, and so on.

[0004] However, the weak mechanical properties of silicon dioxide aerogel itself restrict its application in the field of thermal insulation. At present, in order to enhance its mechanical properties, a fiber felt is often used as a reinforced phase to compound, and by this means the application range of silicon dioxide aerogel is significantly improved, so that aerogel materials can be widely used in thermal insulation in the fields of building materials, aerospace, and industrial pipeline.

[0005] However, the current silicon dioxide aerogel is limited to the preparation process, whose porous structure is not distributed evenly, and especially the distribution of aperture is not uniform, resulting in uneven properties and performances of final composite sheets and thereby limiting its application.

[0006] Therefore, a sol precursor, a silicon dioxide aerogel, a heat insulation sheet, and a preparation method are needed to at least partially solve the above problems.SUMMARY

[0007] A series of simplified concepts is introduced into the portion of Summary, which would be further illustrated in the portion of the detailed description. The Summary of the present application does not mean attempting to define the key feature and essentialtechnical feature of the claimed technical solution, let alone determining the protection scope thereof.

[0008] To at least partially solve the problems, the first aspect of the present application provides a preparation method for preparing a sol precursor, wherein the sol precursor is used for preparing a silicon dioxide aerogel, and the preparation method comprises: a solution configuration step in which a catalyst is added to an alcohol solvent at a hydrolysis temperature and stirred evenly to obtain a mixed solution; and a sol formation step in which a silicon source and a gel accelerator are added to the mixed solution and the hydrolysis temperature is maintained to perform a hydrolysis reaction to obtain the sol precursor; wherein the hydrolysis temperature is 0-10°C; the solvent comprises alcohol substance, and the mixed solution contains water; the catalyst is an acidic catalyst; the gel accelerator is an epoxy compound.

[0009] According to the preparation method of the present application, in the process of preparing the sol precursor, a low hydrolysis temperature is used to slow down the reaction rate, while the epoxy compound is used as the gel accelerator to slowly and uniformly simplify the system to promote the hydrolysis reaction, thus making the whole hydrolysis reaction process mild and uniform. The precipitation or agglomeration caused by the sharp change of pH is eliminated, which is thereby conducive to improving the uniformity of aperture distribution of the silicon dioxide aerogel made by the sol precursor.

[0010] Optionally, the silicon source has a dosage of 18.75-100 volume parts; the solvent has a dosage of 150-200 volume parts; the gel accelerator has a dosage of greater than or equal to 0.6 volume parts.

[0011] Optionally, the epoxy compound has a dosage of greater than or equal to 0.8 volume parts.

[0012] Optionally, the silicon source has a dosage of 25-37.5 volume parts.

[0013] Optionally, the hydrolysis temperature is 0-3°C.

[0014] Optionally, the acidic catalyst is a hydrochloric acid aqueous solution with a molar concentration of 0.09-0.1 Imol / L and a dosage of 22-25 volume parts.

[0015] Optionally, the silicon source is selected from at least one of silicate, silicate ester, silane, siloxane, silyl-ether, and a silicon coupling.

[0016] Optionally, the silicon source is selected from at least one of sodium silicate, methyl orthosilicate, and ethyl orthosilicate.

[0017] Optionally, the silicon source is ethyl orthosilicate.

[0018] Optionally, the gel accelerator is selected from at least one of ethylene oxide, propylene oxide, epoxybutane, and epichlorohydrin.

[0019] Optionally, the gel accelerator is propylene oxide.

[0020] Optionally, the alcohol substance is anhydrous ethanol.

[0021] Optionally, the solution configuration step includes: adding the acidic catalyst and solvent to a reactor and stirring for 20-40min at a hydrolysis temperature to obtain the mixed solution.

[0022] The sol formation step includes: adding a silicon source to the mixed solution, stirring for 3-5h at the hydrolysis temperature, and then adding a gel accelerator and stirring for 3-8 min to obtain the sol precursor.

[0023] The second aspect of the present application provides a sol precursor used to prepare a silicon dioxide aerogel, and the sol precursor is prepared by the preparation method of the first aspect.

[0024] According to the sol precursor of the present application, the aperture of the prepared silicon dioxide aerogel is distributed uniformly.

[0025] The third aspect of the present application provides a preparation method for preparing a silicon dioxide aerogel, wherein the preparation method comprises the following steps: providing the sol precursor of the second aspect; forming the sol precursor into a gel through a gel formation step; aging the gel through an aging step; drying an aged gel through a drying step.

[0026] According to the preparation method of the present application, the aperture of the silicon dioxide aerogel made by the sol precursor is distributed uniformly.

[0027] Optionally, the gel formation step includes: reacting the sol precursor at 70-90°C for 0.5-1.5h to form a gel.

[0028] Optionally, the aging step includes: aging the gel at 50-70°C for 36-60h.

[0029] Optionally, the drying step includes: a solvent replacement step in which the aged gel is subjected to solvent replacement with an anhydrous ethanol at 50-70°C, wherein the anhydrous ethanol is replaced every 12-36h for a total of 36-60h; a supercritical drying step in which the gel after solvent replacement is dried by using a CO2 supercritical drying device.

[0030] Optionally, the CO2 supercritical drying device has a drying kettle and a separating kettle, and the drying process comprises: the gel after solvent replacement is placed in the drying kettle, and CO2 is injected into the CO2 supercritical drying device with a flow rate of 20-40L / h for 5-1 Oh, wherein a temperature in the drying kettle is controlled to be 70-80°C, and a pressure therein is controlled to be 14-18MPa such that CO2 enters a supercritical state and replaces ethanol in a gel aged sheet; a temperature in the separating kettle is controlled to be 30-50°C, and a pressure therein is controlled to be 7-8MPa such that CO2 and ethanol entering the separating kettle can be separated.

[0031] The fourth aspect of the present application provides a silicon dioxide aerogelprepared by the preparation method of the third aspect.

[0032] The silicon dioxide aerogel according to the present application has excellent skeleton structure and aperture distribution.

[0033] Optionally, the silicon dioxide aerogel has a specific surface area of greater than or equal to 1000m2 / g.

[0034] Optionally, a pore volume of the silicon dioxide aerogel is greater than or equal to 2.0cm3 / g.

[0035] Optionally, an adsorption volume of the silicon dioxide aerogel is greater than or equal to 2000cm3 / g.

[0036] The fifth aspect of the present application provides a preparation method for preparing a heat insulation sheet, and the preparation method comprises the following steps: providing a fiber sheet; providing the sol precursor of the second aspect to impregnate the fiber sheet with the sol precursor; subjecting the fiber sheet impregnated with the sol precursor to a gel formation step, an aging step and a drying step to obtain the heat insulation sheet.

[0037] According to the preparation method of the present application, the prepared heat insulation sheet has uniformly distributed thermal insulation properties.

[0038] The sixth aspect of the present application provides a heat insulation sheet.

[0039] The heat insulation sheet comprises a fiber sheet and the silicon dioxide aerogel of the fourth aspect; or the heat insulation sheet is prepared by the preparation method of the fifth aspect.

[0040] The heat insulation sheet according to the present application has good uniformity.DETAILED DESCRIPTION

[0041] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. However, it is obvious to those skilled in this art that the present application may be implemented without one or more of these details. Some technical features well-known in this art are not described in other examples in order to avoid confusion with the present application.

[0042] It shall be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present application. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprising" and / or "including," when used in this specification, specify the presence of stated features, wholes, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features,wholes, steps, operations, elements, components and / or combinations thereof.

[0043] Ordinals such as "first" and "second" quoted in this application are merely identifiers and do not carry any other meaning, such as a specific order. Moreover, for example, the term "first component" itself does not imply the presence of "second component", and the term "second component" itself does not imply the presence of "first component." It should be noted that the terms "up", "down", "front", "back", "left", "right", "inside", "outside" and similar expressions used herein are for illustrative purposes only and are not restrictive.

[0044] The present application provides a preparation method for preparing a sol precursor, a sol precursor, a preparation method for preparing a silicon dioxide aerogel, a silicon dioxide aerogel, a preparation method for preparing a heat insulation sheet, and a heat insulation sheet.

[0045] Wherein, the preparation method for preparing a sol precursor comprises a solution configuration step and a sol formation step. The solution configuration step comprises adding a catalyst to an alcohol solvent under the condition of a hydrolysis temperature and stirring evenly to obtain a mixed solution. The sol formation step comprises adding a silicon source and a gel accelerator to the mixed solution and maintaining the hydrolysis temperature to perform a hydrolysis reaction to obtain the sol precursor.

[0046] The solvent comprises alcohol substance, and the mixed solution contains water. The catalyst is an acidic catalyst, which is used to adjust a pH value of the mixed solution. The hydrolysis temperature is 0-10°C. The gel accelerator is an epoxy compound. It is to be understood that the mixed solution is at least a mixture of water, acidoid, and alcohol.

[0047] According to the preparation method of the present application, in the process of preparing the sol precursor, a low hydrolysis temperature is used to slow down the reaction rate, while the epoxy compound is used as the gel accelerator to slowly and uniformly alkalize the system to promote the hydrolysis reaction, thus making the whole hydrolysis reaction process mild and uniform. The precipitation or agglomeration caused by the sharp change of pH is eliminated, which is thereby conducive to improving the uniformity of aperture distribution of the silicon dioxide aerogel made by the sol precursor.

[0048] As an alternative embodiment, the solvent has a dosage of 150-200 volume parts. The silicon source has a dosage of 18.75-100 volume parts. The gel accelerator has a dosage of greater than or equal to 0.6 volume parts.

[0049] Further, the preparation method for preparing a sol precursor comprises: a solution configuration step in which the acidic catalyst and solvent are added to a reactor and stirred for 20-40min at a hydrolysis temperature to obtain the mixed solution; a sol formation step in which a silicon source is added to the mixed solution, stirred for 3-5h at the hydrolysis temperature, and then a gel accelerator is added and stirred for 3-8 min to obtain the solprecursor.

[0050] Wherein, the hydrolysis temperature is preferably 0-3°C. The silicon source preferably has a dosage of 25-37.5 volume parts. The epoxy compound preferably has a dosage of greater than or equal to 0.8 volume parts.

[0051] The acid catalyst can be hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, nitric acid, acetic acid, carbonic acid, oxalic acid, formic acid, acetic acid, butyric acid, or the like. Preferably, the acid catalyst is hydrochloric acid. More specifically, the acidic catalyst may be an aqueous solution of hydrochloric acid, with the water preferably deionized. Thus, water in hydrochloric acid aqueous solution can be used as a part of the solvent.

[0052] As an alternative embodiment, the acidic catalyst is a hydrochloric acid aqueous solution with a molar concentration of 0.09-0.11 mol / L and a dosage of 22-25 volume parts. Accordingly, when water in the hydrochloric acid aqueous solution exists as a part of the solvent, the amount of alcohol substance in the solvent is 128-175 volume parts.

[0053] Alcohol substance can be compounds containing hydrocarbon groups in molecule or compounds with carbon bound hydroxyl groups on the side chain of benzene ring. For example, the alcohol substance may be selected from at least one of methanol, ethanol, propanol, butanol, octanol, amyl alcohol, hexanol, heptanol, anthritol, glycol, glycerol, propylene glycol, pentaerythritol, allyl alcohol, vinyl alcohol, and benzyl alcohol. Preferably, the alcohol substance is anhydrous ethanol.

[0054] The silicon source is selected from at least one of silicate, silicate ester, silane, siloxane, silyl-ether, and a silicon coupling. Preferably, the silicon source is selected from at least one of sodium silicate, methyl orthosilicate, and ethyl orthosilicate. Further preferably, the silicon source is ethyl orthosilicate.

[0055] The gel accelerator is selected from at least one of ethylene oxide, propylene oxide, epoxybutane, and epichlorohydrin. Preferably, the gel accelerator is propylene oxide.

[0056] As an alternative embodiment, the preparation method for preparing a sol precursor comprises: a solution configuration step in which hydrochloric acid aqueous solution of 0.09-0.11 mol / L in a dosage of 22-25 volume parts and 128-175 volume parts of anhydrous ethanol are added into the reactor and stirred at a hydrolysis temperature of 0-3°C for 20-40min to obtain a mixed solution; a sol formation step in which 25-37.5 volume parts of ethyl orthosilicate are added to the mixed solution and stirred at the hydrolysis temperature of 0-3°C for 3-5h, and then more than 0.8 volume parts of propylene oxide are added and stirred for 3-8min to obtain the sol precursor.

[0057] The second aspect of the present application provides a sol precursor prepared by the preparation method for the preparation of the sol precursor. The sol precursor is used to prepare the silicon dioxide aerogel.

[0058] According to the sol precursor of the present application, the prepared silicon dioxide aerogel has uniform aperture distribution.

[0059] The third aspect of the present application provides a preparation method for preparing a silicon dioxide aerogel, wherein the preparation method comprises the following steps: providing the sol precursor of the second aspect; forming the sol precursor into a gel through a gel formation step, wherein the gel formation step includes reacting the sol precursor at 70-90°C for 0.5-1.5h to form a gel; aging the gel through an aging step, wherein the aging step includes aging the gel at 50-70°C for 36-60h; and drying an aged gel through a drying step.

[0060] Preferably, the drying step includes a solvent replacement step and a supercritical drying step, wherein the aged gel is subjected to solvent replacement with an anhydrous ethanol at 50-70°C, wherein the anhydrous ethanol is replaced every 12-36h for a total of 36-60h. The gel after solvent replacement is dried by using a CO2 supercritical drying device. The CO2 supercritical drying device has a drying kettle and a separating kettle.

[0061] The drying process specifically comprises: the gel after solvent replacement is placed in the drying kettle, and CCh is injected into the CO2 supercritical drying device with a flow rate of 20-40L / h for 5-1 Oh, wherein a temperature in the drying kettle is controlled to be 70-80°C, and a pressure therein is controlled to be 14-18MPa such that CO2 enters a supercritical state and replaces ethanol in a gel aged sheet. A temperature in the separating kettle is controlled to be 30-50°C, and a pressure therein is controlled to be 7-8MPa such that CO2 and ethanol entering the separating kettle can be separated.

[0062] According to the preparation method of the present application, the silicon dioxide aerogel prepared by the sol precursor has uniform aperture distribution.

[0063] The fourth aspect of the present application provides a silicon dioxide aerogel prepared by the preparation method of the third aspect. The silicon dioxide aerogel according to the present application has excellent skeleton structure and aperture distribution.

[0064] Exemplarily, the silicon dioxide aerogel has a specific surface area of greater than 1000m2 / g. The pore volume of the intermediate pore of the silicon dioxide aerogel is greater than or equal to 2.0cm3 / g. The adsorption volume of the silicon dioxide aerogel is greater than or equal to 2000cm3 / g.

[0065] The present application will be further explained in detail in combination with Examples and Contrast Examples below.Example 1

[0066] The temperature of the reactor is controlled to be 3°C; 22.5ml of O.lmol / L hydrochloric acid aqueous solution is added into the reactor with a measuring cylinder; 150ml of anhydrous ethanol is added into the reactor with the measuring cylinder and stirredfor 30min. After that, 18.75ml of ethyl orthosilicate is added into the reactor with the measuring cylinder and continued to stir for 4h. 0.8ml of propylene oxide is added and stirred for 5min. The reactor is sealed and transferred to an oven at 80°C for heat treatment for Ih, and then transferred to an oven at 60°C for aging for 48h. After the end of aging, the product is subjected to solvent replacement with ethanol, once every 24h, and twice in total. The product after solvent replacement is placed in the drying kettle of the CO2 supercritical drying device, and CO2 is injected with a flow rate of 20-40L / h for 5-10h. The temperature in the drying kettle is controlled to be 75°C, and the pressure therein is controlled to be 15MPa. The temperature in the separating kettle is controlled to be 40°C, and the pressure therein is controlled to be 7.5MPa.

[0067] Afterwards, the tests of silicon dioxide aerogel, such as specific surface area and adsorption volume, are performed by the automatic specific surface area analyzer of model Mike 2460.Example 2

[0068] The amount of ethyl orthosilicate added is 25ml. The other components and process steps are the same as those of Example 1.Example 3

[0069] The ethyl orthosilicate is added with an amount of 37.5ml. The other components and process steps are the same as those of Example EExample 4

[0070] The ethyl orthosilicate is added with an amount of 50ml. The other components and process steps are the same as those of Example 1.Example 5

[0071] The ethyl orthosilicate is added with an amount of 100ml. The other components and process steps are the same as those of Example 1.Example 6

[0072] The propylene oxide is added with an amount of 0.6ml. The other components and process steps are the same as those of Example 2.Example 7

[0073] The propylene oxide is added with an amount of 1.6ml. The other components and process steps are the same as those of Example 2.Example 8

[0074] The addition amount of propylene oxide is 20ml. The other components and process steps are the same as those of Example 2.Example 9

[0075] The temperature of the reactor is controlled at 0°C. The other components and process steps are the same as those of Example 2.Example 10

[0076] The temperature of the reactor is controlled at 10°C. The other components and process steps are the same as those of Example 2.Contrast Example 1

[0077] The ethyl orthosilicate is added with an amount of 6.25ml. The other components and process steps are the same as those of Example 1.Contrast Example 2

[0078] The ethyl orthosilicate is added with an amount of 12.5ml. The other components and process steps are the same as those of Example 1.Contrast Example 3

[0079] The ethyl orthosilicate is added with an amount of 250ml. The other components and process steps are the same as those of Example 1.Contrast Example 4

[0080] The propylene oxide is added with an amount of 0.4ml. The other components and process steps are the same as those of Example 2. The gelling does not occur finally in Contrast Example 4, and no test is performed.Contrast Example 5

[0081] The temperature of the reactor is controlled at 25°C. The other components and process steps are the same as those of Example 2.

[0082] The differences between Examples 1-10 and Contrast Examples 1-5 and test results are summarized in Table 1 below.Table 1

[0083] In practical use, it can be considered that the case in which the specific surface area of the silicon dioxide aerogel is greater than 1000m2 / g and the pore volume of the intermediate pore of the silicon dioxide aerogel is greater than or equal to 2.0cm3 / g is a preferred case. Preferably, the adsorption volume of the silicon dioxide aerogel should be greater than or equal to 2000cm3 / g.

[0084] It can be known, in conjunction with the above Examples 1-5 and Contrast Examples 1-3, that too much ethyl orthosilicate and too little ethyl orthosilicate both are not conducive to the formation of the silicon dioxide aerogel.

[0085] In combination with the above Contrast Example 4 and Examples 6, 2, 7 and 8, it can be seen that the ring-opening reaction of propylene oxide greater than 0.6ml can effectively adjust the pH value of the system, which can play a positive role in the reaction and promote the gel. With the increase of the dosage of propylene oxide, the performance change is no longer obvious at the dosage of more than 0.8ml. Accordingly, the gel promotion effect of propylene oxide is relatively gentle, which can play the gel promotion effect as long as the basic dosage is reached, and excessive propylene oxide will not play a negative effect on the reaction, especially suitable for industrial production.

[0086] Combined with the above Examples 9, 2, 10 and Contrast Example 5, the influence of hydrolysis reaction temperature on the properties of the silicon dioxide aerogel ultimately obtained can be illustrated. Among them, the silicon dioxide aerogel has better performance at 3 °C and below. Although the specific surface area and pore volume show a certain degree of decrease at 10°C, they are still in the acceptable range. However, at room temperature (25°C in Contrast Example 5), the structure of the silicon dioxide aerogel shrinks severely, and the performance declines significantly. Accordingly, the lower the temperature will make the hydrolysis reaction slower, which has a positive promotion effect on the formation of the skeleton structure of the silicon dioxide aerogel. However, due to the presence of a small amount of water in the solvent, there is a possibility of condensation below 0°C, which is not conducive to carrying out production.

[0087] The fifth aspect of the present application provides a preparation method for preparing a heat insulation sheet, wherein the preparation method comprises the followingsteps:

[0088] A fiber sheet is provided. For example, the fiber sheet can be made of a glass fiber sheet, and more specifically, a needled glass fiber felt can be used.

[0089] The sol precursor of the second aspect to impregnate the fiber sheet with the sol precursor is provided. As an alternative embodiment, an impregnation method can be used to directly impregnate the fiber sheet and then extrude it. Alternatively, a vacuum perfusion method can also be used, which is to place the fiber sheet in a sealed container, provide negative pressure to the sealed container and inject the sol precursor, such that the sol precursor can fully impregnate the fiber sheet under the action of negative pressure.

[0090] Afterwards, the fiber sheet impregnated with the sol precursor is subjected to a gel formation step, an aging step and a drying step to obtain the heat insulation sheet, wherein the gel formation step, aging step and drying step can be similar to the gel formation step, aging steps and drying step in the preparation method for preparing the silicon dioxide aerogel of the third aspect, which will not be repeated here.

[0091] According to the preparation method of the present application, the thermal insulation properties of the prepared heat insulation sheet have uniform distribution.

[0092] The sixth aspect of the present application provides a heat insulation sheet, wherein the heat insulation sheet may be made by the preparation method of the fifth aspect.

[0093] Alternatively, the heat insulation sheet comprises a fiber sheet and the silicon dioxide aerogel of the fourth aspect.

[0094] Exemplarily, the powder of the silicon dioxide aerogel of the fourth aspect can be directly compounded into the pores of the fiber sheet. For example, the powder of the silicon dioxide aerogel can be filled into the void of the fiber sheet by applying an alternating electric field.

[0095] The heat insulation sheet according to the present application has good uniformity.

[0096] The processes and steps described above in all preferred embodiments are examples only. Unless an adverse effect occurs, the various processing operations can be performed in a different order from the order of the above processes. The sequence of steps in the processes can also be added, combined, or subtracted according to actual needs.

[0097] Unless otherwise defined, the technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the technical field of the present application. The terms used herein are only for describing specific implementation purposes, and are not intended to limit the present application. A feature described in one embodiment herein can be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or otherwise stated.

[0098] The present application has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of illustration and description. The present application is not limited to the above embodiments. More variations and modifications can be made according to the teachings of the present application, and these variations and modifications fall within the protection scope claimed by the present application.

Claims

WHAT IS CLAIMED IS:

1. A preparation method for preparing a sol precursor, wherein the sol precursor is used for preparing a silicon dioxide aerogel, and the preparation method comprises: a solution configuration step in which a catalyst is added to a solvent at a hydrolysis temperature and stirred evenly to obtain a mixed solution; and a sol formation step in which a silicon source and a gel accelerator are added to the mixed solution and the hydrolysis temperature is maintained to perform a hydrolysis reaction to obtain the sol precursor; wherein the hydrolysis temperature is 0-10°C; the solvent comprises alcohol substance, and the mixed solution contains water; the catalyst is an acidic catalyst; the gel accelerator is an epoxy compound.

2. The preparation method of claim 1, wherein the silicon source has a dosage of 18.75-100 volume parts; the solvent has a dosage of 150-200 volume parts; the gel accelerator has a dosage of greater than or equal to 0.6 volume parts.

3. The preparation method of claim 2, wherein the epoxy compound has a dosage of greater than or equal to 0.8 volume parts.

4. The preparation method of claim 2, wherein the silicon source has a dosage of 25-37.5 volume parts.

5. The preparation method of claim 1, wherein the hydrolysis temperature is 0-3°C.

6. The preparation method of claim 1, wherein the acidic catalyst is a hydrochloric acid aqueous solution with a molar concentration of 0.09-0.11 mol / L and a dosage of 22-25 volume parts.

7. The preparation method of claim 1, wherein the silicon source is selected from at least one of silicate, silicate ester, silane, siloxane, silyl-ether, and a silicon coupling.

8. The preparation method of claim 7, wherein the silicon source is selected from at least one of sodium silicate, methyl orthosilicate, and ethyl orthosilicate.

9. The preparation method of claim 8, wherein the silicon source is ethyl orthosilicate.

10. The preparation method of claim 1, wherein the gel accelerator is selected from at least one of ethylene oxide, propylene oxide, epoxybutane, and epichlorohydrin.

11. The preparation method of claim 10, wherein the gel accelerator is propylene oxide.

12. The preparation method of claim 1, wherein the alcohol substance is anhydrous ethanol.

13. The preparation method of any one of claims 1-12, wherein the solution configuration step includes: adding the acidic catalyst and solvent to a reactor and stirring for 20-40min at a hydrolysis temperature to obtain the mixed solution; the sol formation step includes: adding a silicon source to the mixed solution, stirring for 3-5h at the hydrolysis temperature, and then adding a gel accelerator and stirring for 3-8 min to obtain the sol precursor.

14. A sol precursor, wherein the sol precursor is used to prepare a silicon dioxide aerogel, and the sol precursor is prepared by the preparation method of any one of claims 1-12.

15. A preparation method for preparing a silicon dioxide aerogel, wherein the preparation method comprises the following steps: providing the sol precursor of claim 14; forming the sol precursor into a gel through a gel formation step; aging the gel through an aging step; drying an aged gel through a drying step.

16. The preparation method of claim 15, wherein the gel formation step includes: reacting the sol precursor at 70-90°C for 0.5-1.5h to form a gel.

17. The preparation method of claim 15, wherein the aging step includes: aging the gelat 50-70°C for 36-60h.

18. The preparation method of claim 15, wherein the drying step includes: a solvent replacement step in which the aged gel is subjected to solvent replacement with an anhydrous ethanol at 50-70°C, wherein the anhydrous ethanol is replaced every 12-36h for a total of 36-60h; a supercritical drying step in which the gel after solvent replacement is dried by using a CO2 supercritical drying device.

19. The preparation method of claim 18, wherein the CO2 supercritical drying device has a drying kettle and a separating kettle, and the drying process comprises: the gel after solvent replacement is placed in the drying kettle, and CCh is injected into the CO2 supercritical drying device with a flow rate of 20-40L / h for 5-10h, wherein a temperature in the drying kettle is controlled to be 70-80°C, and a pressure therein is controlled to be 14-18MPa such that CO2 enters a supercritical state and replaces ethanol in a gel aged sheet; a temperature in the separating kettle is controlled to be 30-50°C, and a pressure therein is controlled to be 7-8MPa such that CO2 and ethanol entering the separating kettle can be separated.

20. A silicon dioxide aerogel, wherein the silicon dioxide aerogel is prepared by the preparation method of any one of claims 15-19.

21. The silicon dioxide aerogel of claim 20, wherein the silicon dioxide aerogel has a specific surface area of greater than or equal to 1000m2 / g.

22. The silicon dioxide aerogel of claim 20, wherein a pore volume of the silicon dioxide aerogel is greater than or equal to 2.0cm3 / g.

23. The silicon dioxide aerogel of claim 20, wherein an adsorption volume of the silicon dioxide aerogel is greater than or equal to 2000cm3 / g.

24. A preparation method for preparing a heat insulation sheet, wherein the preparation method comprises the following steps: providing a fiber sheet; providing the sol precursor of claim 14 to impregnate the fiber sheet with the solprecursor; subjecting the fiber sheet impregnated with the sol precursor to a gel formation step, an aging step and a drying step to obtain the heat insulation sheet.

25. A heat insulation sheet, wherein the heat insulation sheet comprises a fiber sheet and the silicon dioxide aerogel of any one of claims 20-23; or the heat insulation sheet is prepared by the preparation method of claim 24.

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