Vacuum dynamic graded drying aerogel equipment and process

Abstract

The invention relates to a vacuum dynamic graded drying aerogel device and technology, and belongs to the technical field of aerogel material preparation. Comprising a drying kettle, a baffle plate, a rotating motor, a heating device, a second solvent storage tank, a second solvent injection pipeline, a mixed solvent discharge switch, a mixed solvent recovery storage tank, a mixed solvent discharge pipeline, a vacuum port and a fan, when in use, a mixture containing the wet gel and the first solvent is placed in a drying kettle; vacuumizing the interior of the drying kettle; injecting a second solvent into the drying kettle, standing, removing the mixed solvent, and repeating the operation for 3-5 times; a rotating motor of the drying kettle is started, the baffle plate keeps rotating, then the wet gel is subjected to graded drying in a vacuum state, and the dried aerogel is obtained. The problems that in the current aerogel drying process, efficiency is low, and the shrinkage rate is high can be effectively solved.

Description

Technical Field

[0001] The invention relates to vacuum dynamic graded drying aerogel equipment and process, belonging to the technical field of aerogel material preparation. Background Art

[0002] Aerogel is a low-density solid material composed of a nanoscale porous three-dimensional network structure, with excellent properties such as high specific surface area, low volume density, high specific strength and stiffness, low thermal conductivity and low dielectric constant. Due to its unique structure and properties, aerogel has broad application prospects in the fields of thermal insulation, sound insulation, lightweight structure, impact damping, electrodes, catalysts and catalyst carriers, and sensors.

[0003] In the preparation process of aerogel, the drying step is one of the key links. Currently, the commonly used drying methods include supercritical drying and atmospheric pressure drying. Although supercritical drying can effectively maintain the porous network structure of aerogel, it has complex processes, strict equipment requirements, high costs and great safety hazards. Although atmospheric pressure drying is low in cost, it is easy to cause aerogel to shrink and deform during the drying process, affecting the performance of aerogel. Chinese patent CN112672819A discloses a method for drying gel particles, in particular a method for preparing aerogel. The method includes injecting a suspension containing gel particles and a solvent into a tower through which carbon dioxide flows in a countercurrent manner, and separating the dried aerogel particles from the tower. The pressure and temperature in the tower are set so that the mixture of carbon dioxide and solvent is almost supercritical or supercritical. In order to increase the porosity and specific surface area of ​​aerogel, improve its thermal insulation performance and mechanical strength, the patent needs to further optimize the supercritical drying conditions. Chinese patent CN107709424A discloses a system and method for producing aerogel materials, which does not require supercritical drying as part of the manufacturing process. In some cases, certain combinations of materials, solvents and / or processing steps can be used synergistically to enable the manufacture of large, substantially crack-free and / or mechanically strong aerogel materials. In order to improve the production efficiency and quality of aerogel materials, the patent needs to further optimize the solvent replacement and sublimation steps. In general, the existing aerogel drying process has problems such as low drying efficiency and high aerogel shrinkage. It is urgent to develop a new drying process to improve the aerogel drying efficiency and reduce the aerogel shrinkage, so as to obtain aerogel materials with excellent performance. Summary of the invention

[0004] In view of the above-mentioned defects in the prior art, the present invention proposes a vacuum dynamic graded drying aerogel device and process, which is used to solve the problems of low efficiency and high shrinkage rate in the current aerogel drying process.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A vacuum dynamic graded drying aerogel device, the vacuum dynamic graded drying aerogel device comprising: a drying kettle, a baffle, a rotating motor, a heating device, a second solvent storage tank, a second solvent injection pipeline, a mixed solvent discharge switch, a mixed solvent recovery storage tank, a mixed solvent discharge pipeline, a vacuum port and a fan;

[0007] A mixture of wet gel and a first solvent is arranged in the drying kettle, and a second solvent injection port is arranged at the top and bottom of the drying kettle for injecting the second solvent into the top surface and the bottom of the wet gel in the drying kettle, and the second solvent injection port is connected to the second solvent storage tank through a second solvent injection pipe; a mixed solvent discharge port is arranged at the bottom of the drying kettle, a mixed solvent discharge switch is arranged on the mixed solvent discharge port, and the mixed solvent discharge port is connected to the mixed solvent recovery storage tank through the mixed solvent discharge pipe; the vacuum port and the fan are arranged side by side at the top of the drying kettle; the baffle is arranged inside the drying kettle, one end of the baffle extends out of the drying kettle and is coaxially connected to the rotating motor; the heating device is arranged on the inner surface of the drying kettle shell, and can realize 360° uniform heating of the inside of the drying kettle.

[0008] Furthermore, the second solvent is a drying medium with low surface tension.

[0009] Furthermore, the second solvent is n-hexane, tert-butanol, acetone, isopropanol, perfluorohexane or fluorinated ether.

[0010] Furthermore, the rotating motor drives the baffles to rotate, and each baffle can provide heating to ensure that the wet gels in the drying kettle are heated evenly and fully; the baffles are coaxially and staggeredly arranged.

[0011] Furthermore, the vacuum port is connected to a vacuum pump to perform a vacuum operation.

[0012] Furthermore, the fan drives the air flow in the drying kettle to promote the diffusion of various solvent vapors.

[0013] A process for vacuum dynamic graded drying of aerogel, which uses the above vacuum dynamic graded drying aerogel device, and the specific steps are as follows:

[0014] Step 1, placing a mixture containing wet gel and a first solvent in a drying kettle;

[0015] Step 2, evacuate the interior of the drying kettle to make the interior of the drying kettle in a vacuum state;

[0016] Step 3, inject the second solvent into the drying kettle, let it stand for 2 hours and then remove the mixed solvent; continue to inject the second solvent into the drying kettle, let it stand for 2 hours and then remove the mixed solvent, repeating the operation 3 to 5 times;

[0017] Step 4, start the rotating motor of the drying kettle to keep the baffle rotating at a speed of 1 to 3 r / min; then grade the wet gel under vacuum to gradually evaporate the second solvent from the inside of the wet gel to obtain a dried aerogel.

[0018] Furthermore, in step 1, the first solvent is the solvent immersed in the wet gel preparation process.

[0019] Furthermore, in step 2, the vacuum degree inside the drying kettle is 0.1 to 0.5 bar.

[0020] Furthermore, in step 4, the method of graded drying is specifically as follows:

[0021] First stage: adjust the vacuum degree inside the drying kettle to 0.1-0.5 bar, and dry at a temperature of 30-50°C for 3-5 hours;

[0022] Second stage: adjust the vacuum degree inside the drying kettle to 0.01-0.1 bar, and dry at 50-80°C for 2-3 hours;

[0023] The third stage: adjust the vacuum degree inside the drying kettle to 0.01-0.1 bar, and dry at a temperature of 80-120°C for 1-2 hours.

[0024] After adopting the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0025] 1. Vacuum dynamic graded drying can evenly remove the solvent and moisture in the aerogel, avoid problems such as uneven pores and pore collapse caused by uneven local drying or sudden pressure changes, reduce the shrinkage rate of aerogel during the drying process, reduce the deformation of aerogel, maintain the nanoporous structure of aerogel, and the prepared aerogel has a more uniform pore size distribution and higher structural stability, which improves the quality and consistency of aerogel.

[0026] 2. Compared with traditional supercritical drying, vacuum dynamic graded drying does not require high-pressure equipment, avoids expensive equipment investment, and reduces equipment complexity and operating costs. At the same time, the dynamic graded drying process can adjust the drying parameters in real time according to the drying state of the aerogel, improves drying efficiency, and shortens the production cycle.

[0027] 3. By optimizing the drying process, the vacuum dynamic grading drying equipment has lower requirements and simple process operation, which reduces the use and emission of solvents, reduces the environmental governance costs in the production process, and is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1This is a schematic diagram of the structure of a vacuum dynamic graded drying aerogel device of the present invention.

[0029] Wherein: 1. Drying kettle; 2. Baffle; 3. Rotating motor; 4. Second solvent storage tank; 5. Second solvent injection pipeline; 501. Second solvent injection port A; 502. Second solvent injection port B; 503. Second solvent injection port C; 504. Second solvent injection port D; 6. Mixed solvent discharge switch; 601. Mixed solvent discharge port; 7. Mixed solvent recovery tank; 8. Mixed solvent discharge pipeline; 9. Vacuum port; 10. Fan. DETAILED DESCRIPTION

[0030] The following is combined with Figure 1 The present invention is further described in detail with specific implementations to facilitate a clear understanding of the present invention, but they do not constitute a limitation on the present invention.

[0031] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] As attached Figure 1 As shown, a vacuum dynamic graded aerogel drying device of this embodiment comprises: a drying kettle 1, a baffle 2, a rotating motor 3, a heating device, a second solvent storage tank 4, a second solvent injection pipeline 5, a mixed solvent discharge switch 6, a mixed solvent recovery storage tank 7, a mixed solvent discharge pipeline 8, a vacuum port 9 and a fan 10.

[0034] A mixture of wet gel and the first solvent is arranged in the drying kettle 1. A second solvent injection port is arranged at the top and bottom of the drying kettle 1 for injecting the second solvent into the top surface and the bottom of the wet gel in the drying kettle 1. The second solvent injection port is connected to the second solvent storage tank 4 through the second solvent injection pipe 5. In this embodiment, the second solvent is a drying medium with low surface tension, specifically any one of n-hexane, tert-butyl alcohol, acetone, isopropanol, perfluorohexane, and fluorinated ether. In addition, as Figure 1 As shown, there are four second solvent injection ports, namely, second solvent injection port A501, second solvent injection port B502, second solvent injection port C503, and second solvent injection port D504.

[0035] A mixed solvent outlet 601 is provided at the bottom of the drying kettle 1, and a mixed solvent outlet switch 6 is provided on the mixed solvent outlet 601. The mixed solvent outlet 601 is connected to the mixed solvent recovery tank 7 through a mixed solvent outlet pipe 8. A vacuum port 9 and a blower 10 are arranged side by side at the top of the drying kettle 1, and the vacuum port 9 is connected to a vacuum pump for vacuuming. The blower 10 drives the air flow in the drying kettle 1 to promote the diffusion of various solvent vapors. The baffle 2 is arranged inside the drying kettle 1, and one end of the baffle 2 extends out of the drying kettle 1 and is coaxially connected to the rotating motor 3. The heating device is arranged on the inner surface of the shell of the drying kettle 1, and can achieve 360° uniform heating of the inside of the drying kettle 1.

[0036] In this embodiment, the baffles 2 are coaxially arranged in an interlaced manner. The rotating motor 3 drives the baffles 2 to rotate, and each baffle 2 can provide heating to ensure that the wet gel in the drying kettle 1 is heated evenly and fully.

[0037] The above-mentioned vacuum dynamic graded drying process of aerogel uses the above-mentioned vacuum dynamic graded drying aerogel equipment, and the specific steps are as follows:

[0038] Step 1: placing a mixture containing wet gel and a first solvent in a drying kettle 1. The first solvent is the solvent immersed in the wet gel during the preparation process.

[0039] Step 2: evacuate the interior of the drying kettle 1 to make the interior of the drying kettle 1 in a vacuum state. The vacuum degree inside the drying kettle 1 is 0.1-0.5 bar.

[0040] Step 3: inject the second solvent into the drying kettle 1, let it stand for 2 hours, then remove the mixed solvent. Continue to inject the second solvent into the drying kettle 1, let it stand for 2 hours, then remove the mixed solvent, and repeat the operation 3 to 5 times.

[0041] Step 4: Start the rotating motor 3 of the drying kettle 1 to keep the baffle 2 rotating at a speed of 1 to 3 r / min. Then, the wet gel is graded and dried under vacuum to gradually evaporate the second solvent from the inside of the wet gel to obtain a dried aerogel. The specific method of graded drying is as follows:

[0042] Stage 1: Adjust the vacuum degree inside the drying kettle 1 to 0.1-0.5 bar, and dry at a temperature of 30-50°C for 3-5 hours.

[0043] Second stage: adjust the vacuum degree inside the drying kettle 1 to 0.01-0.1 bar, and dry at a temperature of 50-80°C for 2-3 hours.

[0044] The third stage: adjust the vacuum degree inside the drying kettle 1 to 0.01-0.1 bar, and dry at a temperature of 80-120°C for 1-2 hours.

[0045] Example 1

[0046] Place the pure SiO2 wet gel in a drying kettle, evacuate the inside of the drying kettle to a vacuum degree of 0.5 bar, and make the inside of the drying kettle in a vacuum state. Inject tert-butyl alcohol into the drying kettle, let it stand for 2 hours, then remove the mixed solvent, and repeat the operation 4 times. Then start the rotating motor of the drying kettle to keep the baffle rotating at a speed of 2r / min. Then, grade the wet gel under vacuum. The first stage: adjust the vacuum degree to 0.3 bar and dry at a temperature of 40°C for 4.2 hours. The second stage: adjust the vacuum degree to 0.07 bar and dry at a temperature of 80°C for 2.8 hours. The third stage: adjust the vacuum degree to 0.04 bar and dry at a temperature of 100°C for 1.8 hours. Then, alumina aerogel is obtained.

[0047] According to SEM and TEM tests, the dried SiO2 aerogel is a low-density porous aerogel material with a continuous network structure composed of uniform spherical nanoparticles, and the shrinkage rate is 4.1%.

[0048] Example 2

[0049] Place the SiO2 / cellulose wet gel in a drying kettle, evacuate the inside of the drying kettle to a vacuum degree of 0.2 bar, and make the inside of the drying kettle in a vacuum state. Inject perfluorohexane into the drying kettle, let it stand for 2 hours, then remove the mixed solvent, and repeat the operation twice. Then start the rotating motor of the drying kettle to keep the baffle rotating at a speed of 3r / min. Then, dry the wet gel in a vacuum state in stages. The first stage: adjust the vacuum degree to 0.1 bar and dry at a temperature of 50°C for 3.7 hours. The second stage: adjust the vacuum degree to 0.05 bar and dry at a temperature of 60°C for 2.3 hours. The third stage: adjust the vacuum degree to 0.08 bar and dry at a temperature of 110°C for 1.3 hours. Then, cellulose aerogel is obtained.

[0050] According to SEM and TEM tests, the cellulose aerogel obtained by drying is a low-density porous aerogel material with a continuous network structure composed of uniform spherical nanoparticles, and the shrinkage rate is 4.5%.

[0051] Example 3

[0052] Place the SiO2 / alumina wet gel in a drying kettle, evacuate the inside of the drying kettle to a vacuum degree of 0.4 bar, and make the inside of the drying kettle in a vacuum state. Inject isopropanol into the drying kettle, remove the mixed solvent after standing for 2 hours, and repeat the operation 3 times. Then start the rotating motor of the drying kettle to keep the baffle rotating at a speed of 1r / min. Then, the wet gel is graded and dried under vacuum. The first stage: adjust the vacuum degree to 0.5 bar and dry at a temperature of 30°C for 4.8 hours. The second stage: adjust the vacuum degree to 0.03 bar and dry at a temperature of 70°C for 2.6 hours. The third stage: adjust the vacuum degree to 0.02 bar and dry at a temperature of 90°C for 1.5 hours. Then, alumina aerogel is obtained.

[0053] According to SEM and TEM tests, the alumina aerogel obtained by drying is a low-density porous aerogel material composed of uniform spherical nanoparticles and having a continuous network structure, and the shrinkage rate is 3.8%.

[0054] The above is only a preferred embodiment of the present invention, and does not impose any formal limitation on the structure of the present invention. The layout type and the number of uses of the present invention are not limited to this example, and can be optimized and selected according to the actual project. Any modification, equivalent change and decoration of the above embodiment based on the technical principle of the present invention that does not deviate from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A vacuum dynamic graded drying aerogel device, characterized in that: The vacuum dynamic graded drying aerogel device comprises: a drying kettle (1), a baffle (2), a rotating motor (3), a heating device, a second solvent storage tank (4), a second solvent injection pipeline (5), a mixed solvent discharge switch (6), a mixed solvent recovery storage tank (7), a mixed solvent discharge pipeline (8), a vacuum port (9) and a fan (10); The drying kettle (1) is provided with a mixture of wet gel and a first solvent. The top and bottom of the drying kettle (1) are both provided with second solvent injection ports for injecting the second solvent into the top surface and the bottom of the wet gel in the drying kettle (1). The second solvent injection port is connected to the second solvent storage tank (4) via a second solvent injection pipe (5). The bottom of the drying kettle (1) is provided with a mixed solvent discharge port (601). The mixed solvent discharge port (601) is provided with a mixed solvent discharge switch (6). The mixed solvent discharge port (601) is connected to the mixed solvent recovery storage tank (7) via a mixed solvent discharge pipe (8). The vacuum port (9) and the fan (10) are arranged side by side at the top of the drying kettle (1). The baffle (2) is arranged inside the drying kettle (1). One end of the baffle (2) extends out of the drying kettle (1) and is coaxially connected to the rotating motor (3). The heating device is arranged on the inner surface of the shell of the drying kettle (1) to achieve 360° uniform heating of the inside of the drying kettle (1).

2. A vacuum dynamic graded drying aerogel device according to claim 1, characterized in that: The second solvent is a drying medium with low surface tension.

3. A vacuum dynamic graded drying aerogel device according to claim 2, characterized in that: The second solvent is n-hexane, tert-butyl alcohol, acetone, isopropanol, perfluorohexane or fluorinated ether.

4. The vacuum dynamic graded drying aerogel device according to claim 1, characterized in that: The rotating motor (3) drives the baffles (2) to rotate, and each baffle (2) can provide heating to ensure that the wet gel in the drying kettle (1) is heated evenly and fully; the baffles (2) are coaxially and staggeredly arranged.

5. The vacuum dynamic graded drying aerogel device according to claim 1, characterized in that: The vacuum port (9) is connected to a vacuum pump and can perform a vacuum operation.

6. The vacuum dynamic graded drying aerogel device according to claim 1, characterized in that: The fan (10) drives the air flow in the drying kettle (1) to promote the diffusion of various solvent vapors.

7. A process for vacuum dynamic graded drying of aerogel, which uses a vacuum dynamic graded drying of aerogel device according to any one of claims 1 to 6, characterized in that: The specific steps are as follows: Step 1, placing a mixture containing a wet gel and a first solvent in a drying kettle (1); Step 2, evacuating the interior of the drying kettle (1) to place the interior of the drying kettle (1) in a vacuum state; Step 3, injecting the second solvent into the drying kettle (1), leaving it to stand for 2 hours, and then removing the mixed solvent; continuing to inject the second solvent into the drying kettle (1), leaving it to stand for 2 hours, and then removing the mixed solvent, and repeating the operation 3 to 5 times; Step 4, start the rotating motor (3) of the drying kettle (1) to keep the baffle (2) rotating at a speed of 1 to 3 r / min; then grade the wet gel under vacuum to gradually evaporate the second solvent from the inside of the wet gel to obtain a dried aerogel.

8. The process for vacuum dynamic graded drying of aerogel according to claim 7, characterized in that: In the step 1, the first solvent is the solvent immersed in the wet gel during the preparation process.

9. A process for vacuum dynamic graded drying of aerogel according to claim 8, characterized in that: In the step 2, the vacuum degree inside the drying kettle (1) is 0.1 to 0.5 bar.

10. A process for vacuum dynamic graded drying of aerogel according to claim 9, characterized in that: In step 4, the method of graded drying is specifically as follows: First stage: adjusting the vacuum degree inside the drying kettle (1) to 0.1-0.5 bar, and drying at a temperature of 30-50°C for 3-5 hours; The second stage: adjusting the vacuum degree inside the drying kettle (1) to 0.01-0.1 bar, and drying at a temperature of 50-80°C for 2-3 hours; Stage 3: Adjust the vacuum degree inside the drying kettle (1) to 0.01-0.1 bar, and dry at a temperature of 80-120°C for 1-2 hours.

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