CN110342938A - Preparation method of high-flux porous silicon carbide separation membrane - Google Patents

Abstract

The invention relates to a preparation method of a high-throughput porous silicon carbide separation membrane. A silicon carbide membrane with an asymmetric structure is prepared by using a large-pore silicon carbide support as a substrate, and aluminum diethylenetriaminepentaacetate fibers are used as a sacrificial transition layer to make the large-pore support and the small-size separation layer particles Match each other to overcome the infiltration phenomenon of the separation layer particles; the separation layer of the silicon carbide film is prepared by spraying, and the intermediate fiber transition layer is removed at the same time during the process of calcination of the separation layer at high temperature, which simplifies the structure of the silicon carbide film and prepares a high Flux porous silicon carbide separation membrane. The silicon carbide separation membrane prepared by this method has both a large-pore support and a small-pore separation layer, without an intermediate transition layer, good gas permeability, high filtration accuracy, simple preparation process, and easy large-scale production , can be used in industrial dust purification devices, and has broad application prospects in industries such as coal chemical industry, thermal power plants and metal smelters.

Description

A kind of preparation method of high flux porous silicon carbide separation membrane

technical field

The invention belongs to the field of high-temperature dust removal materials, and in particular relates to the preparation of a silicon carbide separation membrane.

Background technique

In recent years, with the development of industrial technology, industrial activities have become more and more frequent, and air pollution has become more and more obvious. Large areas of smog have frequently appeared in many areas of the country. The excessive emission of fine particles is considered to be the direct cause of the smog phenomenon. However, in the industrial waste gas, it not only contains a large amount of dust, but also the temperature of the gas is relatively high, and it is accompanied by toxic substances such as nitrogen oxides and sulfur oxides. Harmful chemical components are difficult to deal with, and the requirements for equipment materials are high. Silicon carbide has high mechanical strength, good heat resistance and corrosion resistance. The silicon carbide membrane used for gas-solid separation is prepared by using silicon carbide material, which has high gas permeability and filtration accuracy, simple separation operation process and low operation cost.

Patent CN 103721578 A discloses a method for preparing a multi-channel asymmetric structure pure silicon carbide separation membrane. The pure silicon carbide membrane with asymmetric structure is a tubular multi-channel structure with the number of channels ranging from 7 to 3000, which significantly increases the unit membrane area and membrane tube strength. In the process, the layer-by-layer spraying method is adopted, and multiple transition layers are used to reduce the pore size layer by layer, so that silicon carbide separation membranes with different pore sizes can be prepared. However, when a filter membrane with a small pore size is prepared, due to the large number of transition layers, not only the process of preparation is more complicated, but also the prepared silicon carbide membrane has low permeability. The final prepared silicon carbide membrane has a pore size of 1 μm, a porosity of 50%, and a pure water filtration flux of 6500 L/m ³ ·h·bar. Patent CN 106083060 A discloses a method for preparing a single-channel asymmetric silicon carbide separation membrane, in which silicon carbide particles with a particle size of 10 μm are coated on a support with a pore size of 15 μm, in order to prepare silicon carbide with a complete surface For the membrane, the thickness of the separation layer was increased to 1 mm, and the pore size distribution of the finally prepared silicon carbide membrane was 2.8 μm, and the gas permeability was 120 m ³ /m ² ·h·kPa.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a high-throughput porous silicon carbide separation membrane.

In order to achieve the purpose of the invention, the technical solution of the present invention is:

A method for preparing a high-throughput porous silicon carbide separation membrane, the specific preparation steps are as follows:

(1) Mix aluminum diethylenetriaminepentaacetate fiber and methyl cellulose solution, stir evenly, and prepare fiber transition layer solution;

(2) Mix silicon carbide particles and sintering aids with methylcellulose solution, stir evenly to prepare a coating solution;

(3) Brushing the fiber transition layer solution in step (1) on the surface of the porous silicon carbide support;

(4) Spray the coating solution in step (2) on the surface of the porous silicon carbide support obtained in step (3) with a spray gun to form a silicon carbide separation membrane;

(5) The silicon carbide support body obtained in step (4) is placed in an atmosphere furnace for high-temperature calcination.

in:

The mass concentration of the methyl cellulose solution described in step (1) is 0.5-3 wt%, and the mass concentration of aluminum diethylenetriamine pentaacetate fiber in the methyl cellulose solution is 0.5-4 wt%.

The mass concentration of the methylcellulose solution described in step (2) is 0.5-3 wt%, the particle size of silicon carbide particles is 5-15 μm, the sintering aids are calcium oxide, zirconia and mullite, and the sintering aid particles are The diameter is 0.5-3 μm; the mass fraction of each substance in the methylcellulose solution is: silicon carbide particles 10-30 wt%, calcium oxide 0.1-0.5 wt%, zirconia 0.1-0.5 wt%, mullite Stone is 0.1-0.5 wt%.

The pore size of the silicon carbide support in step (3) is 20-35 μm, the number of times of brushing in step (3) is 1-5 times, and it is dried for 30 minutes after each brushing.

Step (4) During the spraying process, the distance between the nozzle of the spray gun and the silicon carbide support is 10-30 cm, the spraying pressure is 0.1-0.3 MPa, the spraying time is 4-8 s, spraying 1-4 times, after each spraying Dry for 10-30 min.

The calcination procedure in step (5) is: calcining in an air atmosphere at 0-1200 °C, the heating rate is 1-10 °C/min, and holding at 1200-1500 °C for 2-4 h; then transfer to argon Air atmosphere, continue to keep warm for 2-6 h, and finally cool down naturally.

Beneficial effects of the present invention:

(1) The operation steps of the invention are simple, the performance of the porous silicon carbide separation membrane is stable, the repeatability is high, the parameters are easy to control, and scale-up experiments and large-scale production can be carried out.

(2) Aluminum diethylenetriaminepentaacetate fibers are used as the transition layer. During the preparation process, the macroporous support can be matched with the particles of the small particle size separation layer, effectively preventing the separation layer particles from infiltrating into the support; During the process of calcining the separation layer, the fiber transition layer can be effectively removed, leaving only the support body and the separation layer, which simplifies the structure of the silicon carbide membrane and has the characteristics of a sacrificeable transition layer.

(3) The present invention uses a macroporous support and a sacrificial transition layer to prepare a silicon carbide membrane, which greatly improves the gas permeability of the silicon carbide membrane, and the separation layer with a small pore size ensures the separation efficiency of the silicon carbide membrane.

Description of drawings

1 is a microscopic scanning electron microscope image of the silicon carbide film in Example 1, a section of the transition layer before calcination; b section of the silicon carbide film before calcination; c surface of the silicon carbide film after calcination; d section of the silicon carbide film after calcination.

FIG. 2 is a pore size distribution diagram of the silicon carbide film in Example 2. FIG.

FIG. 3 is a scanning electron microscope image of a cross-section of a silicon carbide film in Example 2. FIG.

FIG. 4 is a scanning electron microscope image of a cross-section of a silicon carbide film in Example 3. FIG.

5 is a scanning electron microscope image of the surface of the silicon carbide film in Example 4.

6 is a scanning electron microscope image of the surface of the silicon carbide film in Example 5.

Detailed ways

The present invention will be further explained below in conjunction with the examples, the following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Example 1

(1) Mix aluminum diethylenetriaminepentaacetate fiber with 0.5 wt% methyl cellulose, and stir evenly to obtain a transition layer fiber solution with a mass concentration of 4 wt%.

(2) Disperse 10 wt% silicon carbide, 0.1 wt% calcium oxide, 0.1 wt% zirconia and 0.1 wt% mullite in 0.5 wt% methyl cellulose solution, in which the average The particle size is 5 μm, and the average particle size of calcium oxide, zirconia and mullite is 0.5 μm, and the coating liquid is obtained after stirring evenly.

(3) Brush the fiber transition layer solution in step (1) onto the surface of the silicon carbide support with a pore size of 20 μm, brush for 5 times, and then dry for 30 min.

(4) Spray the coating solution obtained in step (1) onto the surface of the support in step (3). During the spraying process, the distance between the nozzle of the spray gun and the carbonized intersilicon support is 10 cm, and the spraying pressure is 0.1 MPa. The spraying time is 8 s, spraying 4 times, and drying for 30 min after each spraying.

(5) Separate the porous silicon carbide obtained in step (5) and perform high-temperature calcination at a temperature of 0-1200 °C in an air atmosphere with a heating rate of 1 °C/min and keep it at 1200 °C for 2 h; In an argon atmosphere, keep warm for 4 h, and finally cool down naturally.

Experimental results: The pore size and flux of the porous silicon carbide separation membrane were analyzed using a pore size analyzer PSDA-20. The gas flux was 135 m ³ /m ² ·h·kPa, and the average pore size was 2.43 μm. Figure 1 SEM The figure shows that the thickness of the separation layer is 100 μm, and the interception rate of alumina dust with a particle size of 0.3 μm is 99.9%, but the connection between the separation layer and the support is poor.

Example 2

(1) Mix aluminum diethylenetriamine pentaacetate fiber with 0.5 wt% methyl cellulose, and stir evenly to obtain a solution of aluminum diethylenetriamine pentaacetate fiber with a mass concentration of 0.5 wt%.

(2) Disperse 25 wt% silicon carbide, 0.2 wt% calcium oxide, 0.2 wt% zirconia and 0.2 wt% mullite in a 2 wt% methylcellulose solution, in which the average The particle size is 10 μm, and the average particle size of calcium oxide, zirconia and mullite is 1 μm, and the coating liquid is obtained after stirring evenly.

(3) Brush the fiber transition layer solution in step (1) onto the surface of the silicon carbide support with a pore size of 30 μm, brush once, and then dry for 30 min.

(4) Spray the coating solution obtained in step (1) onto the surface of the support in step (3). During the spraying process, the distance between the nozzle of the spray gun and the silicon carbide support is 10 cm, and the spraying pressure is 0.3 MPa. The spraying time is 8 s, spraying 4 times, and drying for 30 min after each spraying.

(5) Calcining the porous silicon carbide separation membrane obtained in step (5) at a high temperature at 0-1200 °C in an air atmosphere with a heating rate of 1 °C/min and holding at 1300 °C for 2 h; then Change to argon atmosphere, continue to keep warm for 2h, and finally cool down naturally.

Experimental results: Figure 2. The pore size and flux of the porous silicon carbide separation membrane were analyzed using a pore size analyzer PSDA-20. The gas flux was 236 m ³ /m ² h·kPa, and the average pore size was 3.48 μm. Figure 3 Scanning electron microscope pictures show that the thickness of the separation layer is 120 μm, the interception rate of alumina dust with a particle size of 0.3 μm is 99.9%, and a good neck connection is formed between the separation layer and the support.

Example 3

(1) Mix aluminum diethylenetriamine pentaacetate fiber with 2 wt% methyl cellulose, and stir evenly to obtain a solution of aluminum diethylenetriamine pentaacetate fiber with a mass concentration of 2 wt%.

(2) Disperse 25 wt% silicon carbide, 0.3 wt% calcium oxide, 0.3 wt% zirconia and 0.3 wt% mullite in a 2 wt% methylcellulose solution, in which the average The particle size is 10 μm, and the average particle size of calcium oxide, zirconia and mullite is 0.5 μm, and the coating liquid is obtained after stirring evenly.

(3) Brush the fiber transition layer solution in step (1) onto the surface of the silicon carbide support with a pore size of 30 μm, brush three times, and dry for 30 min after each brushing.

(4) Spray the coating solution obtained in step (1) onto the surface of the support in step (3). During the spraying process, the distance between the nozzle of the spray gun and the silicon carbide support is 20 cm, and the spraying pressure is 0.3 MPa. The spraying time is 8 s, spraying 3 times, and drying for 30 min after each spraying.

(5) Separate the porous silicon carbide obtained in step (5) and perform high-temperature calcination at a temperature of 0-1200 °C in an air atmosphere at a heating rate of 5 °C/min and keep it at 1300 °C for 4 h; then transfer to In an argon atmosphere, keep warm for 6 h, and finally cool down naturally.

Experimental results: The pore size and flux of the porous silicon carbide separation membrane were analyzed using a pore size analyzer PSDA-20. The gas flux was 245 m ³ /m ² ·h·kPa, and the average pore size was 3.65 μm. Figure 4 SEM The thickness of the separation layer is 120 μm, the interception rate of alumina dust with a particle size of 0.3 μm is 99.9%, and a good neck connection is formed between the separation layer and the support.

Example 4

(1) Mix aluminum diethylenetriamine pentaacetate fiber with 2 wt% methyl cellulose, and stir evenly to obtain a solution of aluminum diethylene triamine pentaacetate fiber with a mass concentration of 2 wt%.

(2) Disperse 30 wt% silicon carbide, 0.3 wt% calcium oxide, 0.3 wt% zirconia and 0.3 wt% mullite in a 2 wt% methylcellulose solution, in which the average The particle size is 10 μm, and the average particle size of calcium oxide, zirconia and mullite is 1 μm, and the coating liquid is obtained after stirring evenly.

(3) Brush the fiber transition layer solution in step (1) onto the surface of the silicon carbide support with a pore size of 30 μm, brush for 5 times, and dry for 30 min after each brushing.

(4) Spray the coating solution obtained in step (1) onto the surface of the support in step (3). During the spraying process, the distance between the nozzle of the spray gun and the silicon carbide support is 20 cm, and the spraying pressure is 0.3 MPa. The spraying time is 8 s, spraying 3 times, and drying for 30 min after each spraying.

(5) Separate the porous silicon carbide obtained in step (5) and perform high-temperature calcination at a temperature of 0-1200 °C in an air atmosphere at a heating rate of 1 °C/min, and keep it at 1400 °C for 2 h; In an argon atmosphere, keep warm for 4 h, and finally cool down naturally.

Experimental results: The pore size and flux of the porous silicon carbide separation membrane were analyzed using a pore size analyzer PSDA-20. The gas flux was 571 m ³ /m ² ·h·kPa, and the average pore size was 6.58 μm. Figure 5 SEM The figure shows that there is a small amount of over-sintering phenomenon in the separation layer, the thickness of the separation layer is 120 μm, the interception rate of alumina dust with a particle size of 0.3 μm is 73.6%, and a good neck connection is formed between the separation layer and the support.

Example 5

(1) Mix aluminum diethylenetriamine pentaacetate fiber with 3 wt% methyl cellulose, and stir well to obtain a solution of aluminum diethylenetriamine pentaacetate fiber with a mass concentration of 1 wt%.

(2) Disperse 30 wt% silicon carbide, 0.5 wt% calcium oxide, 0.5 wt% zirconia and 0.5 wt% mullite in a 3 wt% methylcellulose solution, in which the average The particle size is 15 μm, and the average particle size of calcium oxide, zirconia and mullite is 3 μm, and the coating liquid is obtained after stirring evenly.

(3) Brush the fiber transition layer solution in step (1) onto the surface of the silicon carbide support with a pore size of 35 μm, brush for 3 times, and dry for 30 min after each brushing.

(4) Spray the coating solution obtained in step (1) onto the surface of the support in step (3). During the spraying process, the distance between the nozzle of the spray gun and the silicon carbide support is 30 cm, and the spraying pressure is 0.3 MPa. The spraying time is 4 s, spray once, and then dry for 30 min.

(5) Separate the porous silicon carbide obtained in step (5) and perform high-temperature calcination at a temperature of 0-1200 °C in an air atmosphere at a heating rate of 10 °C/min and keep it at 1500 °C for 2 h; In an argon atmosphere, continue to keep warm for 4h, and finally cool down naturally.

Experimental results: The pore size and flux of the porous silicon carbide separation membrane were analyzed using a pore size analyzer PSDA-20. The gas flux was 1167 m ³ /m ² h·kPa, and the average pore size was 32.4 μm; Fig. 6 SEM The figure shows that the separation layer is over-sintered, the thickness of the separation layer is 120 μm, the interception rate of dust with a particle size of 0.3 μm is 34.2%, and a good neck connection is formed between the separation layer and the support.

Claims (7)

1. A method for preparing a high-flux porous silicon carbide separation membrane, characterized in that the specific preparation steps are as follows: (1) Mix aluminum diethylenetriamine pentaacetate fiber with methyl cellulose solution, the mass concentration of aluminum diethylene triamine pentaacetate fiber in methyl cellulose solution is 0.5-4 wt%, and prepare fiber after stirring evenly transition layer solution; (2) Mix silicon carbide particles and sintering aids with methylcellulose solution, stir evenly to prepare a coating solution; (3) Brushing the fiber transition layer solution in step (1) on the surface of the porous silicon carbide support; (4) Spray the coating solution in step (2) on the surface of the porous silicon carbide support obtained in step (3) with a spray gun; (5) The silicon carbide support body obtained in step (4) is placed in an atmosphere furnace for high-temperature calcination. 2 . The method for preparing a high-throughput porous silicon carbide separation membrane according to claim 1 , wherein the mass concentration of the methylcellulose solution in step (1) is 0.5-3 wt%. 3. The method for preparing a high-throughput porous silicon carbide separation membrane according to claim 1, wherein the mass concentration of methylcellulose solution in the coating liquid in step (2) is 0.5-3 wt%, The silicon carbide particles have a particle size of 5-15 μm, the sintering aids are calcium oxide, zirconia and mullite, and the sintering aids have a particle size of 0.5-3 μm. 4. The method for preparing a high-throughput porous silicon carbide separation membrane according to claim 3, wherein the mass fraction of each substance in the methylcellulose solution in step (2) is: silicon carbide particles 10-30 wt%, calcium oxide 0.1-0.5 wt%, zirconia 0.1-0.5 wt%, mullite 0.1-0.5 wt%. 5. The method for preparing a high-flux porous silicon carbide separation membrane according to claim 1, characterized in that the pore diameter of the silicon carbide support in step (3) is 20-35 μm, and the step (3) brushing The number of times is 1-5 times, and it is dried for 30 minutes after each brushing. 6. The method for preparing a high-throughput porous silicon carbide separation membrane according to claim 1, wherein the distance between the nozzle of the spray gun and the silicon carbide support during step (4) spraying is 10-30 cm , the spraying pressure is 0.1-0.3 MPa, the spraying time is 4-8 s, spray 1-4 times, and dry for 10-30 minutes after each spraying. 7. The method for preparing a high-throughput porous silicon carbide separation membrane according to claim 1, characterized in that the calcination procedure in step (5) is: calcination in an air atmosphere at 0-1200 °C, The heating rate is 1-10 ℃/min, and the temperature is kept at 1200-1500 ℃ for 2-4 hours; then it is changed to argon atmosphere, and the temperature is continued for 2-6 hours, and finally the temperature is naturally lowered.