1. A silica aerogel, comprising: the catalyst comprises water glass, deionized water and an acid catalyst, wherein the volume ratio of the water glass to the deionized water is 1: 2-1: 4.

2. the silica aerogel according to claim 1, wherein the water glass is an aqueous solution of sodium silicate having a modulus of 2.8 to 3.5 and a mass fraction of 35 to 45%.

3. The silica aerogel according to claim 1, wherein the acidic catalyst is a mixture of one or more of hydrochloric acid, sulfuric acid and acetic acid, and the concentration of the acidic catalyst is 1-5 mol/L.

4. The low-corrosion preparation method of silica aerogel according to claim 1, characterized by comprising the following steps:

1) preparation of silica aerogel precursor

Stirring water glass serving as a silicon source and deionized water at room temperature until the water glass and the deionized water are uniformly mixed, then slowly adding an acid catalyst, and continuously stirring under a closed condition to obtain a silicon dioxide aerogel precursor;

2) gelling and aging of silica aerogel precursor

Placing the silicon dioxide aerogel precursor into a constant-temperature oven for gelling to obtain silicon dioxide gel, and aging the gelled silicon dioxide gel;

3) solvent displacement and base neutralization of silica gels

Carrying out solvent replacement on the aged silica gel for multiple times by adopting ethanol, and carrying out alkali neutralization on the silica gel by utilizing an alkaline alcohol solution to obtain neutral wet gel;

4) drying of silica wet gels

And placing the neutral silica wet gel obtained after the solvent replacement in a carbon dioxide supercritical drying kettle for supercritical drying to prepare the silica aerogel.

5. The low-corrosion preparation method of the silicon dioxide aerogel according to claim 4, wherein the temperature of the constant-temperature oven in the step 2) is 40-60 ℃, and the aging time is 12-24 hours.

6. The low-corrosion preparation method of the silica aerogel according to claim 4, wherein the ethanol concentration used for solvent replacement in the step 3) is 99.5%, and the ethanol is replaced every 24 hours for 3-5 times.

7. The low-corrosion preparation method of the silica aerogel according to claim 4, wherein the alkaline alcohol solution neutralized by alkali in the step 3) is one of ammonia water and sodium hydroxide, and the concentration of the alkaline alcohol solution is 0.01-0.05 mol/L.

8. The low-corrosion preparation method of the silicon dioxide aerogel according to claim 4, wherein during the supercritical drying of the carbon dioxide in the step 4), the drying temperature is 50-70 ℃, the cavity pressure is 10-15 MPa, and the drying time is 6-12 h.

Background

The silicon dioxide aerogel is a light three-dimensional nano porous material which is formed by aggregating colloidal particles or high polymer molecules and takes air as a dispersion medium, and has low density (3-500 kg/m)³) Large porosity (80-99.8%), large specific surface area (20-1000 m)²The material has excellent performances of low thermal conductivity (0.013-0.025W/(m.K)), and the like, and has wide application prospects in the fields of military industry, medical use, building materials and the like.

In the application of the thermal insulation material, the silicon dioxide aerogel blocks the thermal convection of gas molecules in holes by virtue of the aperture smaller than the mean free path of the air molecules, and simultaneously, the three-dimensional nano framework of the silicon dioxide aerogel further weakens the thermal conduction, thereby showing great thermal insulation application potential.

Currently, organic silicon sources are mainly used for preparing the silicon dioxide aerogel. In patent CN108609621A "a method for preparing silica aerogel", ethyl orthosilicate is used as a silicon source, and methyltriethoxysilane is used as a co-precursor to prepare silica aerogel. The organosilane used in the process weakens the flame retardant property of the aerogel, and the cost is high. Meanwhile, hydrochloric acid and ammonia water are used as catalysts, and an acid-base two-step catalysis method is adopted, so that the production process is complicated, the production cost is increased, and the environmental friendliness of ammonia water to a production workshop is poor.

Patent CN111807374A "a low-cost water glass-based silica aerogel and preparation method" discloses a preparation method of silica aerogel by using water glass as silicon source and tartaric acid for one-step catalysis. In the subsequent solvent displacement, n-hexane was selected to replace the original liquid in the wet gel. In order to ensure the smooth generation of gel, the pH value of the system is adjusted to be 1-3 by tartaric acid in the process, so that the threat of corrosion to equipment is generated in a long time, and particularly, the acidic corrosion which lasts for a long time has serious damage to precise supercritical drying equipment.

Disclosure of Invention

The invention mainly solves the technical problem of providing the silicon dioxide aerogel which has low production cost, simple preparation process, environmental protection and small corrosion to equipment and the low-corrosion preparation method thereof.

In order to solve the technical problems, the invention adopts a technical scheme that: providing a silica aerogel comprising: the catalyst comprises water glass, deionized water and an acid catalyst, wherein the volume ratio of the water glass to the deionized water is 1: 2-1: 4.

in a preferred embodiment of the invention, the water glass is a sodium silicate aqueous solution with a modulus of 2.8-3.5 and a mass fraction of 35-45%.

In a preferred embodiment of the invention, the acidic catalyst is a mixture of one or more of hydrochloric acid, sulfuric acid and acetic acid, and the concentration is 1-5 mol/L.

In order to solve the technical problem, the invention adopts another technical scheme that: the low-corrosion preparation method of the silicon dioxide aerogel comprises the following steps:

1) preparation of silica aerogel precursor

Stirring water glass serving as a silicon source and deionized water at room temperature until the water glass and the deionized water are uniformly mixed, then slowly adding an acid catalyst, and continuously stirring under a closed condition to obtain a silicon dioxide aerogel precursor;

2) gelling and aging of silica aerogel precursor

Placing the silicon dioxide aerogel precursor into a constant-temperature oven for gelling to obtain silicon dioxide gel, and aging the gelled silicon dioxide gel;

3) solvent displacement and base neutralization of silica gels

Carrying out solvent replacement on the aged silica gel for multiple times by adopting ethanol, and carrying out alkali neutralization on the silica gel by utilizing an alkaline alcohol solution to obtain neutral wet gel;

4) drying of silica wet gels

And placing the neutral silica wet gel obtained after the solvent replacement in a carbon dioxide supercritical drying kettle for supercritical drying to prepare the silica aerogel.

In a preferred embodiment of the invention, the temperature of the constant-temperature oven in the step 2) is 40-60 ℃, and the aging time is 12-24 hours.

In a preferred embodiment of the present invention, the concentration of ethanol used for solvent replacement in step 3) is 99.5%, and the ethanol is replaced every 24 hours for 3 to 5 times.

In a preferred embodiment of the present invention, the alkaline alcohol solution neutralized by the alkali in the step 3) is one of ammonia water and sodium hydroxide, and the concentration of the alkaline alcohol solution is 0.01 to 0.05 mol/L. The pH of the wet gel after neutralization by the alkaline alcohol solution is 6-8.

In a preferred embodiment of the invention, during the supercritical drying of the carbon dioxide in the step 4), the drying temperature is 50-70 ℃, the pressure of the cavity is 10-15 MPa, and the drying time is 6-12 hours.

The invention has the beneficial effects that: according to the invention, the silicon dioxide aerogel material is obtained by a green low-corrosion preparation method, raw materials with high friendliness are produced by using water glass, hydrochloric acid and the like, and an alkaline alcohol solution is used for neutralization treatment, so that the corrosion of acidic wet gel on supercritical drying equipment is reduced; the controllability of each parameter in the preparation process is high, the product is stable, the large-scale production is feasible, and the method is environment-friendly.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:

FIG. 1 is an SEM photograph of a silica aerogel prepared in example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "front" and "back" and the like indicate orientations and positional relationships based on orientations and positional relationships shown in the drawings or orientations and positional relationships where the products of the present invention are conventionally placed in use, and are used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements to be referred must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, the first feature may be present on or under the second feature in direct contact with the first and second feature, or may be present in the first and second feature not in direct contact but in contact with another feature between them. Also, the first feature being above, on or above the second feature includes the first feature being directly above and obliquely above the second feature, or merely means that the first feature is at a higher level than the second feature. A first feature that underlies, and underlies a second feature includes a first feature that is directly under and obliquely under a second feature, or simply means that the first feature is at a lesser level than the second feature.

The embodiment of the invention comprises the following steps:

example 1: with reference to FIG. 1

A low-corrosion preparation method of silicon dioxide aerogel comprises the following steps:

1) preparation of silica aerogel precursor

Taking water glass with the modulus of 3.37 and the mass fraction of 40% as a silicon source and deionized water, and mixing the silicon source and the deionized water in a ratio of 1: 2 at room temperature, stirring for 2 h until the mixture is uniform, then slowly adding 3 mol/L of an acid catalyst, and continuously stirring for 30 min under a closed condition until the mixture is uniform to obtain a silicon dioxide aerogel precursor;

2) gelling and aging of silica aerogel precursor

Putting the silicon dioxide aerogel precursor into a constant-temperature oven at 60 ℃, and after the precursor is gelled, continuing to age in the constant-temperature oven at 60 ℃ for 24 hours to obtain silicon dioxide gel;

3) solvent displacement and base neutralization of silica gels

Performing solvent replacement on the aged silica gel by using 99.5% ethanol every 24 hours, and performing alkali neutralization by using 0.01 mol/L alkaline alcohol solution after the solvent replacement is performed for three times to obtain neutral wet gel;

4) drying of silica wet gels

And (3) placing the neutral wet gel obtained after solvent replacement and alkali neutralization in a carbon dioxide supercritical drying kettle for supercritical drying at the temperature of 70 ℃ and the pressure of 13MPa, and finally preparing the silicon dioxide aerogel with a uniform structure.

Example 2

A low-corrosion process for producing silica aerogel was carried out in the same manner as in example 1 except that the concentration of the alkali alcohol solution used in the alkali neutralization was 0.05 mol/L.

Example 3

A low-corrosion process for producing silica aerogel, which comprises the same steps as in example 1 except that the order of addition of the alkali alcohol solution used in the alkali neutralization is advanced to the order before the solvent substitution.

The gels obtained after solvent displacement in examples 1-3 were tested for pH using a wide range of pH paper, with the following results:

examples	pH value
		Example 1	7
Example 2	8
		Example 3	6

In conclusion, the silicon dioxide aerogel material is obtained by a green low-corrosion preparation method, the raw materials with high production friendliness such as water glass and hydrochloric acid are utilized, and the alkaline alcohol solution is used for neutralization treatment, so that the corrosion of acidic wet gel on supercritical drying equipment is reduced; the controllability of each parameter in the preparation process is high, the product is stable, the large-scale production is feasible, and the method is environment-friendly.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.