CN110342938B

CN110342938B - Preparation method of high-flux porous silicon carbide separation membrane

Info

Publication number: CN110342938B
Application number: CN201910668952.3A
Authority: CN
Inventors: 仲兆祥; 邢卫红; 乔浩; 张峰; 韩峰; 魏巍
Original assignee: Jiangsu Jiulang High Tech Co ltd; Nanjing Tech University
Current assignee: Jiangsu Jiulang High Tech Co ltd; Nanjing Tech University
Priority date: 2019-07-24
Filing date: 2019-07-24
Publication date: 2021-11-19
Anticipated expiration: 2039-07-24
Also published as: CN110342938A

Abstract

The invention relates to a preparation method of a high-flux porous silicon carbide separation membrane. The silicon carbide film with an asymmetric structure is prepared by taking a large-pore silicon carbide support body as a base material, and diethylenetriaminepentaacetic acid aluminum fiber is taken as a sacrificial transition layer, so that the large-pore support body is matched with small-particle separating layer particles, and the phenomenon of intra-particle infiltration of the separating layer is overcome; the separation layer of the silicon carbide film is prepared by a spraying method, and the intermediate fiber transition layer is removed simultaneously in the process of calcining the separation layer at high temperature, so that the structure of the silicon carbide film is simplified, and the high-flux porous silicon carbide separation film is prepared. The silicon carbide separation membrane prepared by the method has the advantages of large-pore support body and small-pore separation layer, no intermediate transition layer, good gas permeability, high filtration precision, simple preparation process operation, easy large-scale production, and wide application prospect in industries such as coal chemical industry, thermal power plants, metal smelting plants and the like.

Description

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 particularly relates to a preparation method of a silicon carbide separation membrane.

Background

In recent years, with the development of industrial technologies, industrial activities are more and more frequent, air pollution phenomena are more and more obvious, and large-area haze phenomena frequently occur in multiple regions of the country. The emission of fine particles exceeds the standard and is considered to be a direct cause of haze phenomenon, but in industrial exhaust gas, a large amount of dust is contained, the temperature of the gas is high, toxic and harmful chemical components such as nitrogen oxides and sulfur oxides are accompanied, the treatment is difficult, and the requirement on equipment materials is high. Silicon carbide has high mechanical strength, good heat resistance and corrosion resistance. The silicon carbide film for gas-solid separation is prepared from the silicon carbide material, has high gas permeability and filtration precision, and is simple in separation operation process and low in operation cost.

Patent CN 103721578A discloses a preparation method of a pure silicon carbide separation membrane with a multi-channel asymmetric structure. The pure silicon carbide film with the asymmetric structure is a tubular multi-channel structure, the number of channels is 7-3000, and the unit film area and the film tube strength are obviously increased. The process adopts a layer-by-layer spraying method, uses a plurality of transition layers, reduces the aperture layer by layer, and can prepare the silicon carbide separation membranes with different apertures. However, when the filtering membrane with small aperture is prepared, the process preparation process is more complicated and the prepared silicon carbide membrane has smaller permeability due to more transition layers. The aperture of the finally prepared silicon carbide film is 1 mu m, the porosity is 50 percent, and the filtration flux of pure water is 6500L/m³H.bar. Patent CN 106083060A discloses a method for preparing a single-channel silicon carbide separation membrane with an asymmetric structure, wherein a support body with the pore diameter of 15 mu m is coated with silicon carbide particles with the particle diameter of 10 mu m, in order to prepare a silicon carbide membrane with a complete surface, the thickness of the separation layer is increased to 1 mm, the pore diameter distribution of the finally prepared silicon carbide membrane is 2.8 mu m, and the gas permeability is 120 m³/m²·h·kPa。

Disclosure of Invention

The invention aims to provide a preparation method of a high-flux porous silicon carbide separation membrane.

In order to achieve the purpose of the invention, the technical scheme of the invention is as follows:

a preparation method of a high-flux porous silicon carbide separation membrane comprises the following specific preparation steps:

(1) mixing aluminum diethylenetriaminepentaacetate fiber with a methylcellulose solution, and uniformly stirring to prepare a fiber transition layer solution;

(2) mixing silicon carbide particles, a sintering aid and a methylcellulose solution, and uniformly stirring to prepare a coating solution;

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

(4) spraying the coating liquid in the step (2) on the surface of the porous silicon carbide support body obtained in the step (3) by using a spray gun to form a silicon carbide separation membrane;

(5) and (4) placing the silicon carbide support body obtained in the step (4) into an atmosphere furnace for high-temperature calcination.

Wherein:

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

The mass concentration of the methyl cellulose solution in the step (2) is 0.5-3 wt%, the grain diameter of silicon carbide particles is 5-15 μm, sintering aids are calcium oxide, zirconium oxide and mullite, and the grain diameter of the sintering aids is 0.5-3 μm; the mass fraction of each substance in the methylcellulose solution is as follows: 10-30 wt% of silicon carbide particles, 0.1-0.5 wt% of calcium oxide, 0.1-0.5 wt% of zirconium oxide and 0.1-0.5 wt% of mullite.

The aperture of the silicon carbide support in the step (3) is 20-35 mu m, the brushing frequency in the step (3) is 1-5 times, and the silicon carbide support is dried for 30 min after each brushing.

And (4) in the spraying process of the step (4), 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, the spraying is carried out for 1-4 times, and the drying is carried out for 10-30 min after each spraying.

The calcining procedure in the step (5) is as follows: calcining at 0-1200 deg.C in air atmosphere at a heating rate of 1-10 deg.C/min, and maintaining at 1200-1500 deg.C for 2-4 h; then, the temperature is kept for 2 to 6 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.

The invention has the beneficial effects that:

(1) the porous silicon carbide separation membrane has the advantages of simple operation steps, stable performance, high repeatability and easily controlled parameters, and can be used for carrying out amplification experiments and large-scale production.

(2) Aluminum diethylenetriaminepentaacetate fiber is used as a transition layer, so that a macroporous support body and small-particle-size separation layer particles can be matched with each other in the preparation process, and the separation layer particles are effectively prevented from infiltrating into the support body; in the process of calcining the separation layer, the fiber transition layer can be effectively removed, only the support body and the separation layer are remained, the structure of the silicon carbide film is simplified, and the fiber transition layer has the characteristic of sacrificial transition layer.

(3) The invention adopts the macroporous support body and the sacrificial transition layer to prepare the silicon carbide film, greatly improves the gas permeability of the silicon carbide film, and ensures the separation efficiency of the silicon carbide film by the separation layer with small aperture.

Drawings

FIG. 1 is a microscopic scanning electron micrograph of a silicon carbide film in example 1, a cross section of a transition layer before calcination; b, the section of the silicon carbide film before calcination; c, calcining the surface of the silicon carbide film; d, the section of the silicon carbide film after calcination.

Fig. 2 is a graph showing the pore size distribution of the silicon carbide film in example 2.

FIG. 3 is a scanning electron micrograph of a silicon carbide film in example 2.

FIG. 4 is a scanning electron micrograph of a silicon carbide film in example 3.

FIG. 5 is a scanning electron micrograph of the surface of the silicon carbide film of example 4.

FIG. 6 is a scanning electron micrograph of the surface of the silicon carbide film of example 5.

Detailed Description

The present invention is further illustrated by the following examples, which are provided only for the purpose of illustration and are not intended to limit the scope of the invention.

Example 1

(1) Mixing the aluminum diethylenetriaminepentaacetate fiber with 0.5 wt% of methyl cellulose, and uniformly stirring to obtain a transition layer fiber solution with the mass concentration of 4 wt%.

(2) Dispersing 10 wt% of silicon carbide, 0.1 wt% of calcium oxide, 0.1 wt% of zirconium oxide and 0.1 wt% of mullite in 0.5 wt% of methyl cellulose solution, wherein the average grain diameter of silicon carbide powder is 5 microns, and the average grain diameters of the calcium oxide, the zirconium oxide and the mullite are all 0.5 microns, and uniformly stirring to obtain the coating liquid.

(3) And (2) brushing the fiber transition layer solution in the step (1) on the surface of a silicon carbide support body with the aperture of 20 mu m, brushing for 5 times, and then drying for 30 min.

(4) And (3) spraying the coating liquid obtained in the step (1) on the surface of the support body in the step (3), wherein the distance between a spray gun opening and the silicon carbide support body in the spraying process is 10 cm, the spraying pressure is 0.1 MPa, the spraying time is 8 s, the spraying is carried out for 4 times, and the drying is carried out for 30 min after each spraying.

(5) Separating the porous silicon carbide obtained in the step (5) and calcining at high temperature in air atmosphere at 0-1200 ℃, wherein the heating rate is 1 ℃/min, and the temperature is kept at 1200 ℃ for 2 h; then, the temperature is kept for 4 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.

The experimental results are as follows: the aperture analyzer PSDA-20 type is adopted to analyze the aperture and the flux of the porous silicon carbide separation membrane, and the gas flux is 135 m³/m²h.kPa, average pore diameter of 2.43 μm, and the scanning electron micrograph of FIG. 1 shows that the thickness of the separation layer is 100 μm, the retention 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) Mixing the aluminum diethylenetriaminepentaacetate fiber with 0.5 wt% of methyl cellulose, and uniformly stirring to obtain the aluminum diethylenetriaminepentaacetate fiber solution with the mass concentration of 0.5 wt%.

(2) Dispersing 25 wt% of silicon carbide, 0.2 wt% of calcium oxide, 0.2 wt% of zirconium oxide and 0.2 wt% of mullite in 2 wt% of methyl cellulose solution, wherein the average grain diameter of silicon carbide powder is 10 microns, and the average grain diameters of the calcium oxide, the zirconium oxide and the mullite are all 1 micron, and uniformly stirring to obtain the coating solution.

(3) And (2) brushing the fiber transition layer solution in the step (1) on the surface of a silicon carbide support with the aperture of 30 mu m for 1 time, and then drying for 30 min.

(4) And (3) spraying the coating liquid obtained in the step (1) onto the surface of the support body in the step (3), wherein the distance between a spray gun port and the silicon carbide support body in the spraying process is 10 cm, the spraying pressure is 0.3 MPa, the spraying time is 8 s, the spraying is carried out for 4 times, and the coating liquid is dried for 30 min after each spraying.

(5) Calcining the porous silicon carbide separation membrane obtained in the step (5) at high temperature, calcining at the temperature of 0-1200 ℃ in the air atmosphere, wherein the heating rate is 1 ℃/min, and keeping the temperature at 1300 ℃ for 2 h; then, the temperature is kept for 2 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.

The experimental results are as follows: FIG. 2 is a diagram showing the aperture and flux analysis of a porous silicon carbide separation membrane by using an aperture analyzer PSDA-20 type, the gas flux is 236 m³/m²h.kPa, the average pore diameter is 3.48 μm, and the scanning electron microscope picture of figure 3 shows that the thickness of the separation layer is 120 μm, the retention rate of alumina dust with the particle size of 0.3 μm is 99.9%, and a good neck connection is formed between the separation layer and the support body.

Example 3

(1) Mixing the aluminum diethylenetriaminepentaacetate fiber with 2 wt% of methyl cellulose, and uniformly stirring to obtain the aluminum diethylenetriaminepentaacetate fiber solution with the mass concentration of 2 wt%.

(2) Dispersing 25 wt% of silicon carbide, 0.3 wt% of calcium oxide, 0.3 wt% of zirconium oxide and 0.3 wt% of mullite in 2 wt% of methyl cellulose solution, wherein the average grain diameter of silicon carbide powder is 10 microns, and the average grain diameters of the calcium oxide, the zirconium oxide and the mullite are all 0.5 microns, and uniformly stirring to obtain the coating liquid.

(3) And (3) brushing the fiber transition layer solution obtained in the step (1) on the surface of a silicon carbide support with the aperture of 30 mu m, and drying for 30 min after each brushing.

(4) And (3) spraying the coating liquid obtained in the step (1) onto the surface of the support body in the step (3), wherein the distance between a spray gun port and the silicon carbide support body in the spraying process is 20 cm, the spraying pressure is 0.3 MPa, the spraying time is 8 s, the spraying is carried out for 3 times, and the drying is carried out for 30 min after each spraying.

(5) Separating the porous silicon carbide obtained in the step (5) and calcining at high temperature in air atmosphere at 0-1200 ℃, wherein the heating rate is 5 ℃/min, and the temperature is kept at 1300 ℃ for 4 h; then, the temperature is kept for 6 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.

The experimental results are as follows: the aperture analyzer PSDA-20 type is adopted to analyze the aperture and the flux of the porous silicon carbide separation membrane, and the gas flux is 245 m³/m²h.kPa, the average pore diameter is 3.65 μm, the thickness of a separation layer in a scanning electron microscope image of FIG. 4 is 120 μm, the retention rate of alumina dust with the particle size of 0.3 μm is 99.9%, and a good neck connection is formed between the separation layer and a support body.

Example 4

(2) Dispersing 30 wt% of silicon carbide, 0.3 wt% of calcium oxide, 0.3 wt% of zirconium oxide and 0.3 wt% of mullite in 2 wt% of methyl cellulose solution, wherein the average grain diameter of silicon carbide powder is 10 microns, and the average grain diameters of the calcium oxide, the zirconium oxide and the mullite are all 1 micron, and uniformly stirring to obtain the coating solution.

(3) And (3) brushing the fiber transition layer solution obtained in the step (1) on the surface of a silicon carbide support body with the aperture of 30 mu m, and brushing for 5 times, wherein the drying is carried out for 30 min after each brushing.

(5) Separating the porous silicon carbide obtained in the step (5) and calcining at high temperature in an air atmosphere at 0-1200 ℃, wherein the heating rate is 1 ℃/min, and the temperature is kept at 1400 ℃ for 2 h; then, the temperature is kept for 4 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.

The experimental results are as follows: analyzing the aperture and the flux of the porous silicon carbide separation membrane by adopting an aperture analyzer PSDA-20 type, wherein the gas flux is 571 m³/m²h.kPa, the average pore diameter is 6.58 μm, the scanning electron microscope image of FIG. 5 shows that the separating layer has a small amount of over-sintering phenomenon, the thickness of the separating layer is 120 μm, the retention rate of alumina dust with the particle size of 0.3 μm is 73.6%, and a good neck connection is formed between the separating layer and the support body.

Example 5

(1) Mixing the aluminum diethylenetriaminepentaacetate fiber with 3 wt% of methyl cellulose, and uniformly stirring to obtain the aluminum diethylenetriaminepentaacetate fiber solution with the mass concentration of 1 wt%.

(2) Dispersing 30 wt% of silicon carbide, 0.5 wt% of calcium oxide, 0.5 wt% of zirconium oxide and 0.5 wt% of mullite in 3 wt% of methyl cellulose solution, wherein the average grain diameter of silicon carbide powder is 15 microns, and the average grain diameters of the calcium oxide, the zirconium oxide and the mullite are all 3 microns, and uniformly stirring to obtain the coating solution.

(3) And (3) brushing the fiber transition layer solution obtained in the step (1) on the surface of a silicon carbide support with the aperture of 35 mu m, and drying for 30 min after each brushing.

(4) And (3) spraying the coating liquid obtained in the step (1) on the surface of the support body in the step (3), wherein the distance between a spray gun port and the silicon carbide support body in the spraying process is 30 cm, the spraying pressure is 0.3 MPa, the spraying time is 4 s, the spraying is carried out for 1 time, and then the drying is carried out for 30 min.

(5) Separating the porous silicon carbide obtained in the step (5) and calcining at high temperature in an air atmosphere at 0-1200 ℃, wherein the heating rate is 10 ℃/min, and the temperature is kept at 1500 ℃ for 2 h; then, the temperature is kept for 4 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.

The experimental results are as follows: the aperture and the flux of the porous silicon carbide separation membrane are carried out by adopting an aperture analyzer PSDA-20 typeAnalyzed, the gas flux is 1167 m³/m²h.kPa, average pore diameter of 32.4 μm; FIG. 6 is a scanning electron micrograph showing that the separation layer is excessively sintered, the thickness of the separation layer is 120 μm, the dust retention rate for a particle size of 0.3 μm is 34.2%, and good neck connection is formed between the separation layer and the support.

Claims

1. A preparation method of a high-flux porous silicon carbide separation membrane is characterized by comprising the following specific preparation steps:

(1) mixing the aluminum diethylenetriaminepentaacetate fiber with a methyl cellulose solution, wherein the mass concentration of the aluminum diethylenetriaminepentaacetate fiber in the methyl cellulose solution is 0.5-4 wt%, and uniformly stirring to prepare a fiber transition layer solution; the mass concentration of the methyl cellulose solution is 0.5-3 wt%;

(2) mixing silicon carbide particles, a sintering aid and a methylcellulose solution, and uniformly stirring to prepare a coating solution; the mass concentration of the methyl cellulose solution in the coating liquid is 0.5-3 wt%, the grain diameter of silicon carbide particles is 5-15 mu m, the sintering aids are calcium oxide, zirconium oxide and mullite, and the grain diameter of the sintering aids is 0.5-3 mu m; the mass fraction of each substance in the methyl cellulose solution is as follows: 10-30 wt% of silicon carbide particles, 0.1-0.5 wt% of calcium oxide, 0.1-0.5 wt% of zirconium oxide and 0.1-0.5 wt% of mullite;

(3) brushing the fiber transition layer solution in the step (1) on the surface of a porous silicon carbide support; the aperture of the silicon carbide support body is 20-35 mu m, the brushing frequency is 1-5 times, and the silicon carbide support body is dried for 30 min after each brushing;

(4) spraying the coating liquid in the step (2) on the surface of the porous silicon carbide support obtained in the step (3) by using a spray gun; in the spraying process, the distance between the nozzle of the spray gun and the silicon carbide support body is 10-30 cm, the spraying pressure is 0.1-0.3 MPa, the spraying time is 4-8 s, the spraying is carried out for 1-4 times, and the drying is carried out for 10-30 min after each spraying;

(5) placing the silicon carbide support body obtained in the step (4) in an atmosphere furnace for high-temperature calcination, calcining at the temperature of 0-1200 ℃ in the air atmosphere at the heating rate of 1-10 ℃/min, and preserving heat for 2-4 h at the temperature of 1200-1500 ℃; then, the temperature is kept for 2 to 6 hours by changing into argon atmosphere, and finally, the temperature is naturally reduced.