阅读说明：本技术 一种常温常压干燥氧化铝气凝胶的制备方法及其制得的产品 (Preparation method of alumina aerogel dried at normal temperature and normal pressure and product prepared by preparation method ) 是由 胡学兵 刘鑫 何佳军 于 2021-10-20 设计创作，主要内容包括：本发明公开了一种常温常压干燥氧化铝气凝胶的制备方法及其制得的产品,以廉价环保的无机铝盐为前驱体,去离子水和乙醇为溶剂,环氧丙烷为促凝剂,添加适量的干燥控制剂,在常温常压下实现了气凝胶的原位无收缩干燥,所制得的气凝胶产品密度低、比表面积大、性能优异。本发明解决了氧化铝气凝胶在常温常压干燥过程中,发生的大幅度体积收缩而导致产品性能恶化的关键瓶颈问题,同时,本发明具有工艺简便、成本低廉、绿色环保且易规模化量产等诸多优势,对氧化铝气凝胶制造业的技术发展具有重要推动意义。(The invention discloses a preparation method of normal temperature and pressure drying alumina aerogel and a prepared product thereof, wherein cheap and environment-friendly inorganic aluminum salt is used as a precursor, deionized water and ethanol are used as solvents, propylene oxide is used as a coagulant, a proper amount of drying control agent is added, in-situ non-shrinkage drying of the aerogel is realized at normal temperature and pressure, and the prepared aerogel product has low density, large specific surface area and excellent performance. The method solves the key bottleneck problem that the product performance is deteriorated due to large-scale volume shrinkage of the alumina aerogel in the normal-temperature normal-pressure drying process, has the advantages of simple and convenient process, low cost, environmental protection, easiness in large-scale mass production and the like, and has important promotion significance on the technical development of the alumina aerogel manufacturing industry.)

1. A preparation method of alumina aerogel dried at normal temperature and normal pressure is characterized by comprising the following steps:

(1) adding inorganic aluminum salt into a mixed solvent of deionized water and ethanol according to the molar ratio of 1: 3-5, and stirring in a water bath at the temperature of 40-50 ℃ to completely dissolve the inorganic aluminum salt, the deionized water and the ethanol to form a precursor solution;

(2) adding a drying control agent into the precursor solution, wherein the amount of the drying control agent is 5-15 wt% of the precursor solution, and uniformly stirring the precursor solution in a water bath at the temperature of 40-50 ℃ to obtain a mixed solution I;

(3) adding propylene oxide into the mixed solution I according to the molar ratio of inorganic aluminum salt to propylene oxide of 1: 5-10, and uniformly stirring in a water bath at the temperature of 40-50 ℃ to obtain a mixed solution II;

(4) standing and aging the mixed solution II to obtain alumina gel;

(5) and drying the alumina gel at normal temperature under normal pressure, and roasting after drying to obtain the alumina aerogel.

2. The method for preparing an alumina aerogel dried at normal temperature and pressure according to claim 1, wherein the method comprises the following steps: the inorganic aluminum salt is aluminum nitrate nonahydrate or aluminum chloride hexahydrate.

3. The method for preparing an alumina aerogel dried at normal temperature and pressure according to claim 1, wherein the method comprises the following steps: the drying control agent is a mixture of tridecane, 1-methyl-4-isopropylcyclohex-3-ol and ethanol in a mass ratio of 1: 2-6: 10-20.

4. The method for preparing an alumina aerogel dried at normal temperature and pressure according to claim 1, wherein the method comprises the following steps: the stirring time in the step (1) is 30-50 minutes; the stirring time of the step (2) is 5-15 minutes; and (4) stirring time of the step (3) is 5-10 minutes.

5. The method for preparing an alumina aerogel dried at normal temperature and pressure according to claim 1, wherein the method comprises the following steps: and (4) standing and aging at 50-60 ℃ for 5-8 hours.

6. The method for preparing an alumina aerogel dried at normal temperature and pressure according to claim 1, wherein the method comprises the following steps: the drying time in the step (5) is 120-240 hours; the roasting treatment temperature is 500-1000 ℃, and the heat preservation time is 0-20 minutes.

7. A product obtained by the method for producing an alumina aerogel dried under normal temperature and pressure according to any one of claims 1 to 6.

8. The product of claim 7, wherein: the alumina aerogel product has a density of less than 0.1g/cm³Specific surface area of more than 500m²·g^-1。

Technical Field

The invention relates to the technical field of aerogel preparation, in particular to a preparation method of normal-temperature normal-pressure dried alumina aerogel and a product prepared by the method.

Background

The aerogel is used as a novel light nano mesoporous solid with low density, high porosity and high specific surface area, and is widely used in the fields of energy, environmental protection, catalysis, buildings and the like. As a high-performance inorganic oxide aerogel, the alumina aerogel not only has the characteristics of unique three-dimensional network structure, high specific surface area, high porosity, low thermal conductivity coefficient, low density and the like, but also has higher heat resistance (the highest use temperature can exceed 1000 ℃), higher mechanical strength, higher chemical stability and the like compared with other aerogel products, is a novel aerogel material with particularly outstanding temperature resistance and heat insulation performance in the current aerobic environment, and has great application prospects in the fields of heat insulation, energy conservation, high-temperature catalysis and the like.

The drying process is particularly critical in the preparation of alumina aerogel. Because the alumina gel has a high water content (generally over 50%), if no other auxiliary means are adopted, the drying at normal temperature and normal pressure inevitably causes severe shrinkage and cracking of the gel, and finally the product performance is deteriorated, so that a high-quality aerogel product cannot be obtained. To solve the key technical problem, at present, the drying process of alumina aerogel is usually realized by supercritical drying process or freeze drying, but these methods still exist such as: expensive equipment, strict control of process conditions, long period, no contribution to large-scale production of aerogel materials and the like, thereby limiting the implementation of the industrial production of the alumina aerogel. Therefore, the development of an alumina aerogel preparation technology, particularly a drying technology, which is environment-friendly, low in cost and easy to implement in a process, and the obtainment of an alumina aerogel product with excellent performance is a key problem to be solved urgently at the present stage.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation method of normal-temperature normal-pressure dried alumina aerogel, which is green and environment-friendly, low in cost and simple and convenient in process. The invention also aims to provide a product prepared by the preparation method of the alumina aerogel dried at normal temperature and normal pressure.

The purpose of the invention is realized by the following technical scheme:

the invention provides a preparation method of alumina aerogel dried at normal temperature and normal pressure, which comprises the following steps:

(1) adding inorganic aluminum salt into a mixed solvent of deionized water and ethanol according to the molar ratio of 1: 3-5, and stirring in a water bath at the temperature of 40-50 ℃ to completely dissolve the inorganic aluminum salt, the deionized water and the ethanol to form a precursor solution;

(2) adding a drying control agent into the precursor solution, wherein the amount of the drying control agent is 5-15 wt% of the precursor solution, and uniformly stirring the precursor solution in a water bath at the temperature of 40-50 ℃ to obtain a mixed solution I;

(3) adding propylene oxide into the mixed solution I according to the molar ratio of inorganic aluminum salt to propylene oxide of 1: 5-10, and uniformly stirring in a water bath at the temperature of 40-50 ℃ to obtain a mixed solution II;

(4) standing and aging the mixed solution II to obtain alumina gel;

(5) and drying the alumina gel at normal temperature under normal pressure, and roasting after drying to obtain the alumina aerogel.

In the above scheme, the inorganic aluminum salt in the preparation method of the present invention is aluminum nitrate nonahydrate or aluminum chloride hexahydrate. The drying control agent is a mixture of tridecane, 1-methyl-4-isopropylcyclohex-3-ol and ethanol in a mass ratio of 1: 2-6: 10-20.

Further, the stirring time in the step (1) of the preparation method is 30-50 minutes; the stirring time of the step (2) is 5-15 minutes; and (4) stirring time of the step (3) is 5-10 minutes. And (4) standing and aging at 50-60 ℃ for 5-8 hours. The drying time in the step (5) is 120-240 hours; the roasting treatment temperature is 500-1000 ℃, and the heat preservation time is 0-20 minutes.

The density of the product prepared by the preparation method of the alumina aerogel dried at normal temperature and normal pressure is lower than 0.1g/cm³Specific surface area of more than 500m²·g^-1。

The invention has the following beneficial effects:

aiming at the key bottleneck problem that the product performance is deteriorated due to large-scale volume shrinkage of the conventional alumina aerogel in the normal-temperature normal-pressure drying process, the invention takes inorganic aluminum salt as a main raw material and combines the introduction of a drying control agent to realize the in-situ non-shrinkage drying of the alumina aerogel under normal temperature and normal pressure, and the obtained alumina aerogel product has the characteristics of low density, high specific surface area and the like. The method has a plurality of leading advantages of easy process, environmental protection, obvious reduction of the production cost of the alumina aerogel and the like, and has important significance for promoting the scale production, popularization and application of corresponding aerogel products.

Drawings

The invention will now be described in further detail with reference to the following examples and the accompanying drawings:

FIG. 1 is a flow chart of a process for preparing an alumina aerogel according to an embodiment of the present invention;

FIG. 2 is a pictorial representation of an alumina aerogel product (placed on green bristlegrass) in accordance with an embodiment of the present invention;

FIG. 3 is a micrograph of an alumina aerogel product according to an embodiment of the present invention.

Detailed Description

The first embodiment is as follows:

this embodiment is a method for preparing an alumina aerogel dried at normal temperature and pressure, as shown in fig. 1, and the method includes the following steps:

(1) adding aluminum chloride hexahydrate into a mixed solvent of deionized water and ethanol according to the molar ratio of the aluminum chloride hexahydrate to the deionized water to the ethanol of 1: 3, and stirring for 50 minutes in a water bath at the temperature of 40 ℃ to completely dissolve the aluminum chloride hexahydrate and the ethanol to form a precursor solution;

(2) adding a drying control agent into the precursor solution, wherein the drying control agent is a mixture of tridecane, 1-methyl-4-isopropylcyclohexan-3-ol and ethanol in a mass ratio of 1: 2: 10, the using amount of the drying control agent is 15 wt% of the precursor solution, and stirring the mixture in a water bath at the temperature of 50 ℃ for 5 minutes to obtain a mixed solution I;

(3) adding propylene oxide into the mixed solution I according to the molar ratio of aluminum chloride hexahydrate to propylene oxide being 1: 5, and stirring in a water bath at the temperature of 40 ℃ for 10 minutes to obtain a mixed solution II;

(4) standing and aging the mixed solution II at the temperature of 60 ℃ for 5 hours to obtain alumina gel;

(5) drying the alumina gel at normal temperature under normal pressure for 120 hours, heating to 500 ℃ after drying, and keeping the temperature for 20 minutes to obtain the alumina gel with the density of 0.03g/cm³A specific surface area of 589m²·g^-1The alumina aerogel product of (a).

Example two:

this embodiment is a method for preparing an alumina aerogel dried at normal temperature and pressure, as shown in fig. 1, and the method includes the following steps:

(1) adding aluminum nitrate nonahydrate into a mixed solvent of deionized water and ethanol according to the mol ratio of 1: 5, and stirring in a water bath at the temperature of 50 ℃ for 30 minutes to completely dissolve the aluminum nitrate nonahydrate into a precursor solution;

(2) adding a drying control agent into the precursor solution, wherein the drying control agent is a mixture of tridecane, 1-methyl-4-isopropylcyclohexan-3-ol and ethanol in a mass ratio of 1: 6: 20, the using amount of the drying control agent is 5 wt% of the precursor solution, and stirring the mixture in a water bath at the temperature of 40 ℃ for 15 minutes to obtain a mixed solution I;

(3) adding propylene oxide into the mixed solution I according to the molar ratio of aluminum nitrate nonahydrate to propylene oxide being 1: 8, and stirring the mixture in a water bath at the temperature of 50 ℃ for 5 minutes to obtain a mixed solution II;

(4) standing and aging the mixed solution II at the temperature of 50 ℃ for 8 hours to obtain alumina gel;

(5) drying the alumina gel at normal temperature for 240 hours under normal pressure, heating to 800 ℃ after drying, and keeping the temperature for 10 minutes to obtain the alumina gel with the density of 0.05g/cm³And a specific surface area of 537m²·g^-1The alumina aerogel product of (a).

Example three:

this embodiment is a method for preparing an alumina aerogel dried at normal temperature and pressure, as shown in fig. 1, and the method includes the following steps:

(1) adding aluminum chloride hexahydrate into a mixed solvent of deionized water and ethanol according to the molar ratio of the aluminum chloride hexahydrate, the deionized water and the ethanol being 1: 4, and carrying out water bath stirring at the temperature of 45 ℃ for 40 minutes to completely dissolve the aluminum chloride hexahydrate and the ethanol to form a precursor solution;

(2) adding a drying control agent into the precursor solution, wherein the drying control agent is a mixture of tridecane, 1-methyl-4-isopropylcyclohexan-3-ol and ethanol in a mass ratio of 1: 4: 15, the using amount of the drying control agent is 10 wt% of the precursor solution, and stirring the mixture in a water bath at the temperature of 45 ℃ for 10 minutes to obtain a mixed solution I;

(3) adding propylene oxide into the mixed solution I according to the molar ratio of aluminum chloride hexahydrate to propylene oxide being 1: 10, and stirring in a water bath at the temperature of 45 ℃ for 8 minutes to obtain a mixed solution II;

(4) standing and aging the mixed solution II at the temperature of 55 ℃ for 6 hours to obtain alumina gel;

(5) drying the alumina gel at normal temperature for 180 hours under normal pressure, and heating to the roasting temperature of 1000 ℃ after drying is finished to obtain the alumina gel with the density of 0.08g/cm³The specific surface area of the alloy is 509m²·g^-1The alumina aerogel product of (a).

The alumina aerogel product prepared by the embodiment of the invention has the characteristic of low density (see figure 2), and the product contains a large number of micro-nano holes and has the characteristic of high specific surface area (see figure 3).