阅读说明：本技术 一种改进型二氧化硅气凝胶的制备方法及二氧化硅气凝胶 (Preparation method of improved silicon dioxide aerogel and silicon dioxide aerogel ) 是由 翁朝阳 于 2020-05-25 设计创作，主要内容包括：本发明属于气凝胶领域,具体是一种改进型二氧化硅气凝胶的制备方法及二氧化硅气凝胶,在二氧化硅气凝胶制备步骤的水解步骤后加入3-氨丙基三羟基硅烷参与缩合反应,经过老化、置换和修饰剂修饰后,获得氨基改性二氧化硅湿凝胶,浸泡入多酰氯化合物中,氨基与酰氯快速反应在二氧化硅湿凝胶表面形成薄层的交联型聚酰胺化合物,干燥后即获得薄层交联型聚酰胺化合物包覆的二氧化硅气凝胶,除去外层的聚酰胺化合物,即可获得较纯的二氧化硅气凝胶,本发明为制备纯度较高的二氧化硅气凝胶提供了一个新的思路。(The invention belongs to the field of aerogel, and particularly relates to an improved silicon dioxide aerogel and a preparation method thereof.)

1. A preparation method of improved silicon dioxide aerogel is characterized by comprising the following steps,

s1, uniformly mixing tetraethoxysilane, absolute ethyl alcohol and deionized water according to a molar ratio of 1:15:5, adding acid to adjust the pH value to 2-4, hydrolyzing for 1-3 hours, adding 3-aminopropyl trihydroxysilane, uniformly stirring, adding alkali to adjust the pH value to 8.5-10, and condensing to form wet gel;

s2, carrying out aging and absolute ethyl alcohol replacement on the wet gel for 2 times in the step S1, modifying the wet gel in a trimethylchlorosilane or hexamethyldisilazane normal hexane solution, taking out the wet gel, putting the wet gel in a polyacyl chloride compound solution for 10-30 min, taking out the wet gel, putting the wet gel in absolute ethyl alcohol, taking out and drying the wet gel to obtain the improved silicon dioxide aerogel.

2. The method according to claim 1, wherein the molar ratio of the ethyl orthosilicate to the 3-aminopropyltrihydroxysilane in the step S1 is 1: 0.01-5.

3. The preparation method according to claim 2, wherein the molar ratio of the ethyl orthosilicate to the 3-aminopropyltrihydroxysilane is 1: 0.05-3.

4. The preparation method according to claim 3, wherein the molar ratio of the ethyl orthosilicate to the 3-aminopropyltrihydroxysilane is 1: 0.1-1.

5. The method according to claim 1, wherein the polyacyl chloride compound in step S2 is at least one selected from the group consisting of 1,3, 5-benzenetricarbonyl chloride, isophthaloyl chloride, terephthaloyl chloride, 1, 6-adipoyl chloride, malonyl chloride, 1, 4-succinyl chloride, 1, 5-glutaryl chloride, 1, 7-pimeloyl chloride, 1, 8-suberoyl chloride, 1, 9-azelaioyl chloride, and 1, 10-sebacoyl chloride.

6. The method according to claim 1, wherein the concentration of the polyacyl chloride compound in the polyacyl chloride compound solution in step S2 is 5-300 g/L, and the solvent used is n-hexane.

7. Silica aerogel, characterized by being obtained by the preparation process according to any one of claims 1 to 6.

Technical Field

The invention belongs to the technical field of aerogel, and relates to an improved silicon dioxide aerogel and a preparation method thereof.

Background

The silicon dioxide aerogel has the characteristics of low density, low thermal conductivity coefficient, high porosity, large specific surface area and the like, is a novel material with very large application prospect, can be widely applied to the fields of heat insulation and heat preservation, catalysis and adsorption, but has low mechanical strength, needs supercritical drying or freeze drying in the preparation process, has high equipment cost, long drying period and low capacity, and greatly limits the application of the silicon dioxide aerogel, so that the normal pressure drying is an important direction for breaking through the silicon dioxide aerogel. At present, various methods are used for improving the mechanical strength of the silicon dioxide aerogel to realize normal pressure drying, but the method is at the cost of greatly sacrificing the performance of low density and low heat conductivity coefficient.

Therefore, the realization of the normal pressure drying preparation of the silica aerogel and the great maintenance of the properties of low density, low thermal conductivity, high surface area and the like are of great significance and are the focus of the industry.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation method of an improved silicon dioxide aerogel, wherein 3-aminopropyl trihydroxy silane is added in the preparation process of the silicon dioxide aerogel to participate in condensation reaction to obtain amino modified silicon dioxide wet gel; the amino and the acyl chloride can quickly react at room temperature to form an amide compound, so that the amino and the polyacyl chloride compound on the surface interface of the amino modified silica wet gel quickly react to form a cross-linked amide compound, and the polyacyl chloride compound is prevented from further entering the silica wet gel to react with the amino, so that the cross-linked amide compound coated modified silica wet gel is obtained. Because the cross-linked polyamide compound has higher strength, when the silica wet gel is subjected to freeze drying, supercritical drying or normal pressure drying, the shrinkage and collapse of a wet gel three-dimensional network structure caused by solvent volatilization can be effectively resisted, the cross-linked amide compound coated modified silica aerogel is obtained, and the cross-linked amide compound on the surface layer is removed, so that the purer silica aerogel is obtained.

Another object of the present invention is to provide a silica aerogel which can be used as it is or after removing a crosslinked amide compound on the surface layer thereof, since the crosslinked amide compound on the surface layer is very thin.

The technical scheme of the invention is as follows:

a preparation method of improved silicon dioxide aerogel comprises the following steps,

s1, uniformly mixing tetraethoxysilane, absolute ethyl alcohol and deionized water according to a molar ratio of 1:15:5, adding acid to adjust the pH value to 2-4, hydrolyzing for 1-3 hours, adding 3-aminopropyl trihydroxysilane, uniformly stirring, adding alkali to adjust the pH value to 8.5-10, and condensing to form wet gel;

s2, carrying out aging and absolute ethyl alcohol replacement on the wet gel for 2 times in the step S1, modifying the wet gel in a trimethylchlorosilane or hexamethyldisilazane normal hexane solution, taking out the wet gel, putting the wet gel in a polyacyl chloride compound solution for 10-30 min, taking out the wet gel, putting the wet gel in absolute ethyl alcohol, taking out and drying the wet gel to obtain the improved silicon dioxide aerogel.

Preferably, the molar ratio of the ethyl orthosilicate to the 3-aminopropyltrihydroxysilane in the step S1 is 1: 0.01-5.

More preferably, the molar ratio of the ethyl orthosilicate to the 3-aminopropyltrihydroxysilane is 1: 0.05-3.

More preferably, the molar ratio of the ethyl orthosilicate to the 3-aminopropyltrihydroxysilane is 1: 0.1-1.

Preferably, the poly-acid chloride compound in step S2 is at least one selected from the group consisting of 1,3, 5-benzenetricarbonyl chloride, isophthaloyl chloride, terephthaloyl chloride, 1, 6-adipoyl chloride, malonyl chloride, 1, 4-succinyl chloride, 1, 5-glutaryl chloride, 1, 7-pimeloyl chloride, 1, 8-suberoyl chloride, 1, 9-azelaioyl chloride, and 1, 10-sebacoyl chloride. More preferably, the poly-acid chloride compound is composed of a triacyl chloride compound and a diacyl chloride compound, and specifically, may be a combination of 1,3, 5-benzenetricarboxylic acid chloride and isophthaloyl chloride, a combination of 1,3, 5-benzenetricarboxylic acid chloride and terephthaloyl chloride, a combination of 1,3, 5-benzenetricarboxylic acid chloride and 1, 4-butanedicarboxylic acid chloride, or a combination of 1,3, 5-benzenetricarboxylic acid chloride and 1, 6-hexanedioyl chloride.

Preferably, the concentration of the polyacyl chloride compound in the polyacyl chloride compound solution in the step S2 is 5-300 g/L, and the solvent used is n-hexane.

A silica aerogel obtained by the preparation method according to any one of the above embodiments.

The invention has the beneficial effects that:

(1) according to the invention, 3-amino trihydroxy silane is added in the preparation of silicon dioxide aerogel to participate in condensation reaction, and the obtained wet gel has amino groups; and then the wet gel is placed in a polyacyl chloride compound solution, and the amino and the polyacyl chloride compound react on the surface of the wet gel to form a layer of thin cross-linking amide compound with higher strength by utilizing the high reactivity of the amino and the acyl chloride, so that the problem of silicon dioxide three-dimensional network shrinkage collapse caused by solvent volatilization can be effectively solved, the silicon dioxide aerogel with a more regular shape can be obtained even in normal pressure drying, and the problems of high drying equipment cost, long drying time and high cost can be solved by realizing the normal pressure drying.

(2) The formed cross-linked amide compound is on the outer surface of the silicon dioxide aerogel, the silicon dioxide aerogel is mainly internally provided with a silicon-oxygen chain three-dimensional structure, and the characteristics of low density, low heat conductivity coefficient and high specific surface area of the silicon dioxide aerogel are kept inside the silicon dioxide aerogel. In the prior art, the reinforced material is uniformly distributed in the whole silica aerogel, so that the performance of the silica aerogel is influenced.

(3) According to the silicon dioxide aerogel disclosed by the invention, because the chemical reaction of acyl chloride and amino mainly occurs on the outer surface interface of the wet gel, and the acyl chloride can be prevented from entering the silicon dioxide wet gel, the formed cross-linked amide compound is mainly on the outer surface of the silicon dioxide aerogel, and the thickness of the formed cross-linked amide compound is very thin, and after the cross-linked amide compound on the surface layer is removed, the pure silicon dioxide aerogel can be obtained, and the silicon dioxide aerogel has an important significance for preparing large silicon dioxide aerogels.

Detailed Description

The technical solution of the present invention is further illustrated and described by the following detailed description.

Unless otherwise specified, the parts in the following embodiments are parts by weight.