CN113683389B - Method for producing silica aerogel felt by repeatedly utilizing supercritical waste liquid - Google Patents

Abstract

The invention belongs to the field of waste liquid reuse, and discloses a method for repeatedly utilizing supercritical waste liquid to produce silica airgel felt. Based on the principle of gas-phase catalysis, the waste liquid produced in the supercritical process is placed in a steam generator The gas-phase gel catalyst is prepared, and then the gas-phase gel catalyst is passed into a silica sol device to carry out a catalytic gel reaction to prepare a silica airgel felt with excellent performance. In the present invention, the hydrolysis and polycondensation reactions of the silicon source are carried out in different reactors respectively, which avoids the inconsistent situation of the gel degree caused by the simultaneous hydrolysis and polycondensation, and avoids the comparison caused by the simultaneous hydrolysis and polycondensation of the silicon source. The strong network microstructure solids are attached to the inner wall of the reactor, thereby shortening the operating life of the equipment; at the same time, the recovered supercritical waste liquid is reused in the silica sol-gel process through gasification, ensuring the reuse of waste liquid , rational use of resources to save costs.

Description

A method for reusing supercritical waste liquid to produce silica airgel felt

technical field

The invention belongs to the field of waste liquid reuse, and in particular relates to a method for repeatedly utilizing supercritical waste liquid to produce silica airgel felt.

Background technique

Airgel is a highly porous material composed of nanoparticles, and has high porosity, specific surface area, and low thermal conductivity, thereby attracting attention as an efficient heat insulating material, sound insulating material, and the like. However, due to the high production cost of the airgel blanket, the airgel blanket is not widely used in the market although it has excellent thermal insulation performance when compared with conventional thermal insulation materials. Due to the expensive raw materials, complicated production process and the treatment cost of a large amount of waste liquid generated in the production process, the product price of airgel felt is relatively higher than that of other heat insulation materials.

The method of reducing the cost by changing the raw material or changing the production process in the above price increase factors will directly affect the quality of the product, so it is not suitable for application. The easiest way to reduce the cost is to reuse the waste liquid generated during the production process.

On the other hand, in the prior art, the preparation process of airgel is usually as follows: inject the liquid phase silicon source material and a certain proportion of other raw materials into the reactor, mix and stir evenly at room temperature, and add a certain solution as a catalyst to make The liquid-phase silicon source material is fully hydrolyzed, and after a certain period of time, an appropriate amount of another liquid-phase catalyst is added. Thereafter, the sol is sprayed onto various prepared fiber substrates through a dipping machine, and the prepared gel mat is left to age for several hours to make it fully gel and form a relatively strong network microstructure. In the above-mentioned process, the two production processes of sol and gel are almost carried out at the same time, which means that the raw material will undergo polycondensation when hydrolysis occurs, the sol is in the form of a solid-liquid mixture, and the sol that is undergoing hydrolysis-polycondensation reaction Spraying on various fiber substrates will lead to uneven dipping, which in turn will lead to uneven bonding between the airgel and the substrate, and poor uniformity of thermal conductivity of the final product. And because the two production processes of sol and gel are carried out in the same reactor, some relatively solid network microstructure solids will be attached to the inner wall of the reactor, which will affect the normal operation of the equipment over time.

Therefore, in the present invention, the supercritical waste liquid is used to prepare the gas-phase catalyst for the gel process, and the hydrolysis and polycondensation reactions of the silicon source are carried out separately, so that the supercritical waste liquid can be reused, the cost can be reduced, and an airgel with excellent performance can be prepared. .

Contents of the invention

The object of the present invention is to provide a method for reusing supercritical waste liquid to produce silica airgel felt, reusing the supercritical waste liquid produced in the supercritical drying process of silica wet gel, and reclaiming the supercritical waste The liquid is reused in the silica sol-gel process through gasification.

In order to achieve the above object, the technical scheme that the present invention takes is as follows:

A method for reusing supercritical waste liquid to produce silica airgel blanket, the steps are as follows:

(1) Recycling the supercritical waste liquid produced in the supercritical drying process of silica wet gel;

(2) Mix silicon source, ethanol, and water according to silicon source: ethanol: water = 1: (2~60): (1~30) to obtain silica sol;

(3), impregnating the fiber material in the silica sol obtained in step (2) for 8-24 hours to obtain a sol composite material;

(4) Transfer the sol composite material impregnated in step (3) to the gel reactor, and pass the supercritical waste liquid in step (1) into the gel reactor after gasification for catalytic gelling reaction , to obtain the gel composite material;

(5) The gel composite material obtained in step (4) is subjected to supercritical drying to obtain a silica airgel felt.

The silicon source is one or more of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or alkylalkoxysilane.

Preferably, the supercritical waste liquid in the step (1) contains water, organic solvent and ammonium ion NH ₄ ⁺ .

Preferably, the recovery of the supercritical waste liquid in step (1) also includes a process of distilling it; the temperature of the distillation is 70-80°C.

Preferably, the alkylalkoxysilane includes methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, vinyltriethyl One or more of oxysilane, propyltrimethoxysilane or propyltriethoxysilane.

Preferably, the fiber material is fiber wadding, fiber mat, fiber roll; the fiber is pre-oxidized silk fiber, glass fiber, aluminum silicate fiber, quartz fiber, high silica fiber, carbon fiber, mullite fiber , basalt fiber, silicon carbide fiber, alumina fiber, boron nitride fiber.

Preferably, the supercritical waste liquid is gasified and passed into the sol composite material so that the pH value of the sol composite material is 7-10.

Preferably, the gasification process in step (4) is to place supercritical waste liquid in a steam generator to prepare a gas-phase gel catalyst, and pass the generated gas into a gel reactor for catalytic gelation reaction.

Preferably, an aging process is also included before the gel composite material is dried in step (5), specifically aging the gel composite material at room temperature or at a temperature of 30-60° C. for 8-24 hours.

Preferably, before the gel composite material is dried in step (5), a hydrophobic treatment process is also included, specifically placing the gel composite material in an absolute ethanol solution containing a volume fraction of 0.2-10% hydrophobizing agent, Stand at room temperature for 1-24h, and the hydrophobizing agent is one or both of hexamethyldisilazane or trimethoxymethylsilane.

Preferably, the solvent replacement process is also included before the gel composite material is dried in step (5), specifically placing the silica wet gel sheet in absolute ethanol for solvent replacement, and the number of replacements is 1-4 times , the time of each replacement is 2-12h.

Preferably, in the preparation process, after the step (5) of supercritical drying, it also includes continuing to recycle the supercritical waste liquid, and use it in the sol-gel process of silica airgel.

The silica airgel felt produced by supercritical waste liquid is obtained by the above preparation method.

Beneficial effect:

In the present invention, based on the principle of gas-phase catalysis, the waste liquid produced in the supercritical drying process is placed in a steam generator to prepare a gas-phase gel catalyst by gasification, and then the gas-phase gel catalyst is passed into the silica sol for compounding In the material, a catalytic gel reaction is carried out to prepare a silica airgel felt with good thermal insulation performance.

The invention reuses the supercritical waste liquid produced in the supercritical drying process, and reuses the recovered supercritical waste liquid in the silica sol-gel process through gasification, thereby ensuring the reuse of the waste liquid and rationally utilizing resources to save costs .

When the method provided by the present invention prepares airgel composite materials, the hydrolysis and polycondensation reactions of the silicon source can be carried out in different reactors respectively, avoiding the situation of inconsistencies in the degree of gel caused by simultaneous hydrolysis and polycondensation, and avoiding the situation caused by The relatively solid network microstructure solids produced by the simultaneous hydrolysis and polycondensation of the silicon source adhere to the inner wall of the reactor, thereby shortening the operating life of the equipment.

The preparation process of the present invention does not require additional investment in equipment, the preparation process is simple and economical, and is beneficial to provide new ideas and directions for improving the preparation process of the airgel felt.

detailed description

The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following examples are only used to illustrate the present invention but not to limit the scope of the present invention.

Example 1:

(1) Recycling the supercritical waste liquid produced in the supercritical drying process of silica wet gel;

(2) Mix silicon source, ethanol, and water according to silicon source: ethanol: water = 1:6:2 to obtain silica sol;

(3), impregnating the fiber material in the silica sol obtained in step (2) for 16 hours to obtain a sol composite material;

(4) Transfer the sol composite material impregnated in step (3) to the gel reactor, and pass the supercritical waste liquid in step (1) into the gel reactor after gasification for catalytic gelling reaction , to obtain the gel composite material;

(5) The gel composite material obtained in step (4) is subjected to supercritical drying to obtain a silica airgel felt.

The supercritical waste liquid in step (1) contains water, organic solvent and ammonium ion (NH ₄ ⁺ ), and the organic solvent is mainly ethanol.

The silicon source is tetraethyl orthosilicate; the fiber material is glass fiber rolls.

The supercritical waste liquid is gasified and passed into the sol composite material so that the pH value of the sol composite material is 8.

The gasification process described in step (4) is to place the supercritical waste liquid in a steam generator to prepare a gas-phase gel catalyst, and pass the generated gas into a gel reactor for catalytic gelation reaction.

The silica airgel felt prepared by the above preparation method.

The thermal conductivity of the silica airgel mat obtained in this example is 0.02w/(m·°C).

Example 2:

(1) Recycling the supercritical waste liquid produced in the supercritical drying process of silica wet gel;

(2) Mix silicon source, ethanol, and water according to silicon source: ethanol: water = 1:30:10 to obtain silica sol;

(3), impregnating the fiber material in the silica sol obtained in step (2) for 20 hours to obtain a sol composite material;

(4) Transfer the sol composite material impregnated in step (3) to the gel reactor, and pass the supercritical waste liquid in step (1) into the gel reactor after gasification for catalytic gelling reaction , to obtain the gel composite material;

(5) Aging: Aging the gel composite material obtained in step (4) at 40°C for 16 hours;

(6) The gel composite material obtained in step (5) is subjected to supercritical drying to obtain a silica airgel felt.

The supercritical waste liquid in step (1) contains water, organic solvent and ammonium ion (NH ₄ ⁺ ), and the organic solvent is mainly ethanol.

The silicon source is methyltrimethoxysilane; the fiber material is aluminum silicate fiber mat.

The supercritical waste liquid is gasified and passed into the sol composite material so that the pH value of the sol composite material is 7.

The gasification process described in step (4) is to place the supercritical waste liquid in a steam generator to prepare a gas-phase gel catalyst, and pass the generated gas into a gel reactor for catalytic gelation reaction.

The silica airgel felt prepared by the above preparation method.

The thermal conductivity of the silica airgel mat obtained in this example is 0.018w/(m·°C).

Example 3:

(1) Recycling the supercritical waste liquid produced in the supercritical drying process of silica wet gel;

(2) Mix silicon source, ethanol, and water according to silicon source: ethanol: water = 1:8:3 to obtain silica sol;

(3), impregnating the fiber material in the silica sol obtained in step (2) for 20 hours to obtain a sol composite material;

(4) Transfer the sol composite material impregnated in step (3) to the gel reactor, and pass the supercritical waste liquid in step (1) into the gel reactor after gasification for catalytic gelling reaction , to obtain the gel composite material;

(5) Hydrophobizing treatment: place the gel composite material obtained in step (4) in absolute ethanol solution containing 8% hydrophobizing reagent by volume fraction, and let it stand at room temperature for 6 hours;

(6) The gel composite material obtained in step (5) is subjected to supercritical drying to obtain a silica airgel felt.

The supercritical waste liquid in step (1) contains water, organic solvent and ammonium ion (NH ₄ ⁺ ), and the organic solvent is mainly ethanol.

The silicon source is tetraethyl orthosilicate; the fiber material is glass fiber mat.

The supercritical waste liquid is gasified and passed into the sol composite material so that the pH value of the sol composite material is 9.

The gasification process described in step (4) is to place the supercritical waste liquid in a steam generator to prepare a gas-phase gel catalyst, and pass the generated gas into a gel reactor for catalytic gelation reaction.

The hydrophobizing agent is hexamethyldisiloxane.

The silica airgel felt prepared by the above preparation method.

The thermal conductivity of the silica airgel mat obtained in this example is 0.019w/(m·°C).

Example 4:

(1) Recycling the supercritical waste liquid produced in the supercritical drying process of silica wet gel;

(2) After recovering the supercritical waste liquid, it also includes the process of distilling it; the temperature of the distillation is 76°C.

(3) Mix silicon source, ethanol, and water according to silicon source: ethanol: water = 1:10:6 to obtain silica sol;

(4), impregnating the fiber material in the silica sol obtained in step (3) for 18 hours to obtain a sol composite material;

(5) Transfer the sol composite material impregnated in step (4) to the gel reactor, and pass the supercritical waste liquid in step (1) into the gel reactor after gasification for catalytic gelling reaction , to obtain the gel composite material;

(6) Hydrophobizing treatment: place the gel composite material obtained in step (5) in absolute ethanol solution containing 8% hydrophobizing reagent by volume fraction, and let stand at room temperature for 12 hours;

(7) The gel composite material obtained in step (6) is subjected to supercritical drying to obtain a silica airgel felt.

The supercritical waste liquid in step (1) contains water, organic solvent and ammonium ion (NH ₄ ⁺ ), and the organic solvent is mainly ethanol.

The silicon source is ethyl orthosilicate; the fiber material is aluminum silicate fiber mat.

The supercritical waste liquid is gasified and passed into the sol composite material so that the pH value of the sol composite material is 8.

The gasification process described in step (4) is to place the supercritical waste liquid in a steam generator to prepare a gas-phase gel catalyst, and pass the generated gas into a gel reactor for catalytic gelation reaction.

The hydrophobizing agent is trimethylchlorosilane.

The silica airgel felt prepared by the above preparation method.

The thermal conductivity of the silica airgel mat obtained in this example is 0.021w/(m·°C).

Example 5

The difference from Example 3 is that before the supercritical drying in step (6), the gel composite material is placed in absolute ethanol for solvent replacement, and the replacement is performed 3 times, each time 10 h.

The silica airgel felt prepared by the above preparation method.

The thermal conductivity of the silica airgel mat obtained in the embodiment is 0.019w/(m·°C).

Claims (7)

1. A method for producing silica aerogel felt by recycling supercritical waste liquid is characterized in that the supercritical waste liquid generated in the supercritical drying process of silica wet gel is recycled, and the recycled supercritical waste liquid is recycled in the silica sol-gel process through gasification;

the method comprises the following specific steps:

(1) Recovering supercritical waste liquid generated in the supercritical drying process of the wet silica gel;

(2) Mixing a silicon source, ethanol and water according to the ratio of the silicon source to the ethanol to the water = 1: 2 to 60: 1 to 30 to obtain a silica sol;

(3) Soaking the fiber material in the silica sol obtained in the step (2) for 8-24h to obtain a sol composite material;

(4) Transferring the sol composite material impregnated in the step (3) into a gel reactor, gasifying the supercritical waste liquid obtained in the step (1), and introducing the gasified supercritical waste liquid into the gel reactor to perform catalytic gelling reaction to obtain a gel composite material;

(5) Carrying out supercritical drying on the gel composite material obtained in the step (4) to obtain a silicon dioxide aerogel felt;

the silicon source is one or more than two of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or alkyl alkoxy silane;

the supercritical waste liquid in the step (1) contains water, organic solvent and ammonium ion NH4 ⁺ ；

Introducing the gasified supercritical waste liquid into the sol composite material to ensure that the pH value of the sol composite material is 7-10;

and (4) putting the supercritical waste liquid into a steam generator to prepare a gas-phase gel catalyst in the gasification process, and introducing the generated gas into a gel reactor to perform a catalytic gelling reaction.

2. The method for producing the silica aerogel felt by recycling the supercritical waste liquid as claimed in claim 1, wherein the method comprises the following steps: after the supercritical waste liquid in the step (1) is recovered, the process of distilling the supercritical waste liquid is also included; the distillation temperature is 70-80 ℃.

3. The method for producing the silica aerogel felt by recycling the supercritical waste liquid as claimed in claim 1, wherein the method comprises the following steps: the alkyl alkoxy silane comprises one or more than two of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane, propyl trimethoxy silane or propyl triethoxy silane.

4. The method for producing the silica aerogel felt by recycling the supercritical waste liquid as claimed in claim 1, wherein the method comprises the following steps: the fiber material is fiber batting, fiber cushion and fiber coiled material; the fiber is one of pre-oxidized fiber, glass fiber, aluminum silicate fiber, quartz fiber, high silica fiber, carbon fiber, mullite fiber, basalt fiber, silicon carbide fiber, alumina fiber and boron nitride fiber.

5. The method for producing the silica aerogel felt by recycling the supercritical waste liquid as claimed in claim 1, wherein the method comprises the following steps: and (3) before drying the gel composite material in the step (5), an aging process is also included, and specifically, the gel composite material is subjected to aging treatment for 8-24h at room temperature or under the condition of heating at 30-60 ℃.

6. The method for producing the silica aerogel felt by recycling the supercritical waste liquid as claimed in claim 1, wherein the method comprises the following steps: and (4) before drying the gel composite material in the step (5), a hydrophobization treatment process is also included, specifically, the gel composite material is placed in an absolute ethyl alcohol solution containing 0.2-10% of a hydrophobization reagent in volume fraction, and is kept standing for 1-24h at room temperature.

7. The silica aerogel felt produced by using the supercritical waste liquid prepared by the method of any one of claims 1 to 5.