A Preparation Method of High-Temperature Catalytic Filtration Silicon Carbide Ceramic Membrane

Abstract

The present invention discloses a preparation method of a high-temperature catalytic filtration silicon carbide ceramic membrane, which includes preparing a silicon carbide ceramic support body, then coating a fiber transition layer on the outside of the silicon carbide ceramic support body, drying it, and then obtaining a catalytic layer by dip-coating a catalyst layer, and then forming an intermetallic compound layer outside the catalytic layer. After drying in an oven at 100-120 °C and then sintering at a high temperature above 1200 °C, the catalytic filtration silicon carbide ceramic membrane is obtained. The silicon carbide ceramic membrane in the present invention has good filtration performance on the premise of ensuring the gas permeation flux, improves the flexural strength of the silicon carbide ceramic membrane, and simultaneously has the function of catalytic degradation and removal of various pollutants. It has the characteristics of high temperature resistance, corrosion resistance, high dust removal efficiency, and the ability to remove various pollutants. It can be mass-produced, reduce costs, is suitable for a wide temperature range, has a long service life, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical fields of coal chemical industry flue gas pollution control and functional new materials, and relates to a preparation method of a high-temperature catalytic filtration silicon carbide ceramic membrane. Background Art

[0002] In industrial production processes such as coal chemical industry, waste incineration, cement and metallurgy, and biomass gasification, a large amount of high-temperature tail gas with complex components is generated, along with a large amount of ultrafine particulate matter and corrosive gas components such as VOCs, NOx, SO2, CO2, and H2S. Direct emission causes relatively large environmental pollution and must be purified to meet the standards before emission.

[0003] Silicon carbide porous ceramics can operate at high temperatures (>500°C) for a long time, and have excellent thermal shock resistance, corrosion resistance, creep resistance, and relatively high mechanical strength. They are high-temperature flue gas dust removal materials with broad application prospects. However, silicon carbide ceramics belong to brittle materials, and their low room temperature strength and poor fracture toughness limit the application range of silicon carbide ceramics. Therefore, the preparation of silicon carbide-based composite ceramics with higher strength and higher fracture toughness has always been one of the main research contents of silicon carbide ceramics.

[0004] Since the technical concept of ceramic filter tube catalysts was proposed, there has been no research report on large-scale industrial production. Researchers in Germany, Italy, South Korea, etc. have carried out theoretical and experimental exploration research, and Germany has formed related ceramic filter tube catalyst products, while domestic research on this has just started and is still in the experimental exploration stage. For example, the existing public technology: CN201110104548.7, which provides a preparation method of silicon carbide porous ceramics that can be used as high-temperature soot filters. Although it can significantly increase the pore number and specific surface area of silicon carbide porous ceramics, there are still problems such as the brittleness of ceramics, corrosion resistance, and lifespan. Summary of the Invention

[0005] In order to solve at least one of the above problems, the present invention provides a preparation method of a high-temperature catalytic filtration silicon carbide ceramic membrane, which increases the anti-bending strength of the silicon carbide ceramic membrane, and also provides the application of the high-temperature catalytic filtration silicon carbide ceramic membrane in catalytic degradation of various pollutants such as dust, CO2, VOCs, NOx, SO2, and H2S in flue gas.

[0006] In order to achieve the above purpose, the present invention adopts the following technical means:

[0007] The first aspect of the present invention provides a preparation method of a high-temperature catalytic filtration silicon carbide ceramic membrane, including the following steps:

[0008] (1) Prepare a silicon carbide ceramic support

[0009] Using silicon carbide micropowder as the aggregate, zirconia as the sintering aid, silicon carbide whiskers and mullite fibers as the reinforcing agents, and polyvinyl alcohol as the binder, after mechanically mixing the raw materials evenly, adding additives and then quickly mixing to obtain granulated powder, forming it by cold isostatic pressing, drying in an oven at 100 - 120 °C, and sintering at a high temperature above 1500 °C, a silicon carbide ceramic support is obtained;

[0010] (2)Coating the fiber transition layer

[0011] Mix mullite fibers, aluminosilicate fibers, activated carbon fibers, polyvinyl alcohol, and deionized water into a slurry, and evenly coat the slurry on the surface of the silicon carbide ceramic support in step (1). After drying at 60 - 80 °C for 2 - 4 h, a ceramic support with a fiber transition layer is obtained;

[0012] (3)Dipping and coating the catalyst layer

[0013] Mix vanadium molybdenum cerium titanium catalyst, sodium tripolyphosphate, and polyvinyl alcohol to form a suspension solution. Immerse the ceramic support prepared in (2) into the suspension solution, and ultrasonically vibrate the suspension solution for dipping and coating. After drying in an oven at 100 - 120 °C, a ceramic support with a catalytic layer is obtained;

[0014] (4)Forming the intermetallic compound layer

[0015] Put silicon carbide micropowder, iron oxide, aluminum oxide, zirconia, boron oxide, and mullite whiskers into a mixer. After fully mixing evenly, put them into a heating kettle, spread and heat to melt to form a suspension solution, add additives, formulate a casting solution, and use the method of rotary thermal spraying to spray it on the surface of the ceramic support completed in step (3) multiple times. After drying in an oven at 100 - 120 °C and sintering at a high temperature above 1200 °C, a ceramic / FeAl intermetallic compound composite coating is formed, and a catalytic filtration silicon carbide ceramic membrane is obtained.

[0016] In some embodiments of the present invention, in the step (1), the mass percentage of the aggregate is 80% - 90%, the mass percentage of the sintering aid is 5% - 10%, the mass percentage of the reinforcing agent is 5% - 10%, and the mass percentage of the binder is 1% - 2%.

[0017] The mass percentage of silicon carbide whiskers in the reinforcing agent is 5%, and the mass percentage of mullite fibers is 3%.

[0018] In some embodiments of the present invention, in the step (2), the mass percentage of mullite fibers is 2% - 10%, the mass percentage of aluminosilicate fibers is 2% - 10%, the mass percentage of activated carbon fibers is 5% - 10%, the mass percentage of polyvinyl alcohol is 3% - 5%, and the mass percentage of deionized water is 60% - 80%.

[0019] In some embodiments of the present invention, in step (3), the mass percentage of the catalyst is 8% - 12%, the mass percentage of the dispersant is 50% - 80%, and the mass percentage of the binder is 5% - 10%.

[0020] In some embodiments of the present invention, in step (4), the mass percentage of silicon carbide micropowder is 20% - 30%, the mass percentage of iron oxide is 15% - 25%, the mass percentage of alumina is 15% - 25%, the mass percentage of zirconia is 1% - 5%, the mass percentage of boron oxide is 1% - 5%, and the mass percentage of mullite whiskers is 10% - 20%.

[0021] In some embodiments of the present invention, the length of the activated carbon fiber is 100 - 400 microns.

[0022] In some embodiments of the present invention, the additive is one or more of paraffin wax and polyvinyl alcohol. In some specific embodiments of the present invention, the mass percentage of paraffin wax is 1% - 5%, and the mass percentage of polyvinyl alcohol is 1% - 5%.

[0023] The second aspect of the present invention provides a catalytic filtration silicon carbide ceramic membrane prepared by the method according to the first aspect.

[0024] The third aspect of the present invention provides the application of the catalytic filtration silicon carbide ceramic membrane described in the second aspect in catalytic removal of various pollutants in high-temperature waste gas.

[0025] In some embodiments of the present invention, the various pollutants in the high-temperature waste gas include dust, CO2, VOCs, NOx, SO2, and H2S.

[0026] Advantages of the present invention

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention adds activated carbon fibers to the fiber transition layer, making its surface have a microporous structure, which can not only serve as the attachment point of the catalyst but also play a connecting role between the silicon carbide fibers and the catalyst. Therefore, the activated carbon fibers enable the catalyst to be tightly combined with the support, greatly improving the catalyst loading and the firmness of the combination.

[0029] 2. The present invention uniformly disperses and loads the catalyst onto the fiber layer of the silicon carbide ceramic support by the impregnation method, which not only ensures the gas permeation rate, reduces the pressure drop, but also can catalytically degrade CO2, VOCs, NOx, SO2, H2S, etc. in the flue gas while filtering dust.

[0030] 3. The present invention introduces metals such as iron oxide and aluminum oxide to form a ceramic / FeAl intermetallic compound composite coating, effectively improving the brittle characteristics of the ceramic membrane, enhancing the mechanical properties of the ceramic membrane, and extending its service life.

[0031] 4. The catalytic filtration silicon carbide ceramic membrane prepared by the method of the present invention has high temperature resistance, corrosion resistance, a dust removal efficiency as high as 99.9%, can remove various pollutants, can be mass-produced, has a reduced cost, is applicable to a wide temperature range, has a long service life, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shows the comparison of the anti-bending strength of the materials prepared in Examples 1-2 and Comparative Examples 1-2 of the present invention;

[0033] Figure 2 Shows the comparison of the catalytic removal effects of the materials prepared in Examples 1-2 and Comparative Examples 1-2 of the present invention on various pollutants. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following examples are used herein to demonstrate the preferred embodiments of the present invention. Those skilled in the art will understand that the techniques disclosed in the following examples represent techniques discovered by the inventors that can be used to implement the present invention, and thus can be regarded as preferred embodiments for implementing the present invention. However, those skilled in the art should understand from this specification that the specific embodiments disclosed here can be modified in many ways and still obtain the same or similar results without departing from the spirit or scope of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. The references cited herein and the materials they cite will be incorporated by reference. Those skilled in the art will recognize or can learn many equivalent techniques to the specific embodiments of the invention described herein through routine experimentation. These equivalents will be included in the claims.

[0036] A method for preparing a high-temperature catalytic filtration silicon carbide ceramic membrane, comprising the following steps:

[0037] (1) Prepare a silicon carbide ceramic support

[0038] Using silicon carbide micropowder as the aggregate, zirconia as the sintering aid, silicon carbide whiskers and mullite fibers as the reinforcing agents, and polyvinyl alcohol as the binder, after mechanically mixing the raw materials evenly, adding additives and then quickly mixing to obtain granulated powder, forming with a cold isostatic press, drying in an oven at 100 - 120 °C, and sintering at a high temperature above 1500 °C, a silicon carbide ceramic support is obtained; among them, the mass percentage of the aggregate is 80% - 90%, the mass percentage of the sintering aid is 5% - 10%, the mass percentage of the reinforcing agents is 5% - 10%, the mass percentage of the binder is 1% - 2%, the mass percentage of silicon carbide whiskers in the reinforcing agents is 5%, and the mass percentage of mullite fibers is 3%; the additive is paraffin with a mass percentage of 1% - 5%.

[0039] (2)Coating the fiber transition layer

[0040] Mix mullite fibers, aluminum silicate fibers, activated carbon fibers, polyvinyl alcohol, and deionized water into a slurry, evenly coat the slurry on the surface of the silicon carbide ceramic support in step (1), and obtain a ceramic support with a fiber transition layer after drying at 60 - 80 °C for 2 - 4 h; among them, the mass percentage of mullite fibers is 2% - 10%, the mass percentage of aluminum silicate fibers is 2% - 10%, the mass percentage of activated carbon fibers is 5% - 10%, the mass percentage of polyvinyl alcohol is 3% - 5%, and the mass percentage of deionized water is 60% - 80%; the length of the activated carbon fibers is 100 - 400 microns.

[0041] (3)Dipping and coating the catalyst layer

[0042] Mix vanadium molybdenum cerium titanium catalyst, dispersant sodium tripolyphosphate, and binder polyvinyl alcohol to form a suspension solution, immerse the ceramic support prepared in (2) into the suspension solution, and dip - coat with ultrasonic vibration of the suspension solution, and obtain a ceramic support with a catalytic layer after drying in an oven at 100 - 120 °C; among them, the mass percentage of vanadium molybdenum cerium titanium catalyst is 8% - 12%, the mass percentage of dispersant sodium tripolyphosphate is 50% - 80%, and the mass percentage of binder polyvinyl alcohol is 5% - 10%.

[0043] (4)Forming an intermetallic compound layer

[0044] Put silicon carbide micropowder, iron oxide, alumina, zirconia, boron oxide, and mullite whiskers into a mixer. After fully mixing, put them into a heating kettle, and conduct exothermic heating and melting to form a suspension. Then add additives to prepare a casting solution. The casting solution is sprayed onto the surface of the ceramic support that has completed step (3) by means of rotary thermal spraying multiple times. After drying in an oven at 100 - 120°C and then sintering at a high temperature above 1200°C, a ceramic / FeAl intermetallic compound composite coating is formed, and thus a catalytic filtration silicon carbide ceramic membrane is obtained. Among them, the mass percentage of silicon carbide micropowder is 20% - 30%, the mass percentage of iron oxide is 15% - 25%, the mass percentage of alumina is 15% - 25%, the mass percentage of zirconia is 1% - 5%, the mass percentage of boron oxide is 1% - 5%, the mass percentage of mullite whiskers is 10% - 20%, and the additives are paraffin with a mass percentage of 1% - 5% and polyvinyl alcohol with a mass percentage of 1% - 5%.

[0045] The present invention also provides a catalytic filtration silicon carbide ceramic membrane prepared by the method described above.

[0046] The present invention also provides the application of the catalytic filtration silicon carbide ceramic membrane described above in catalytic removal of various pollutants in high-temperature waste gas; the various pollutants in the high-temperature waste gas include dust, CO2, VOCs, NOx, SO2, and H2S.

[0047] The technical solutions of the present application will be further described in detail below in conjunction with specific implementation embodiments.

[0048] Example 1

[0049] (1) Prepare a silicon carbide ceramic support

[0050] Using silicon carbide micropowder as the aggregate, zirconia as the sintering aid, silicon carbide whiskers and mullite fibers as the reinforcing agents, polyvinyl alcohol as the binder, and paraffin as the additive. Among them, the mass percentages of the aggregate, sintering aid, reinforcing agents, and binder are 85%, 5%, 8%, and 2% respectively. The mass percentage of silicon carbide whiskers in the reinforcing agents is 5%, and the mass percentage of mullite fibers is 3%. After mechanical mixing evenly, add paraffin with a mass percentage of 3% and quickly mix to obtain granulated powder. Then form it and dry it in an oven at 105°C, and sinter it in a muffle furnace in an air atmosphere at 1600°C to obtain a silicon carbide ceramic membrane support.

[0051] (2) Coat the fiber transition layer

[0052] Using mullite fiber, aluminum silicate fiber, activated carbon fiber with a length of 300 microns, polyvinyl alcohol, and deionized water as raw materials, the mass percentages of each raw material are 2%, 2%, 5%, 3%, and 80% respectively. Mix and stir evenly. Mix the mixed slurry and zirconia balls in a mass ratio of 1:1.5 and put them into a ball mill tank. Ball mill for half an hour at a speed of 200 revolutions per minute to obtain a uniformly mixed slurry, and add silicon carbide micropowder.

[0053] Use the spin coating method to evenly coat the surface of the silicon carbide ceramic membrane support to form a fiber transition layer. Dry it in an oven at 80 °C and sinter it in a muffle furnace at 1300 °C to obtain the fiber transition layer.

[0054] (3) Dip-coat the catalyst layer

[0055] Mix vanadium molybdenum cerium titanium catalyst, sodium tripolyphosphate, and polyvinyl alcohol to form a mixed slurry according to the mass percentages of 10%, 70%, and 10%. Immerse the ceramic support prepared in step (2) into the suspension, perform ultrasonic impregnation on the silicon carbide ceramic membrane for 1 h, dry it in an oven at 105 °C, and sinter it in a muffle furnace at 600 °C to obtain a ceramic support with a catalyst layer.

[0056] (4) Intermetallic compound layer

[0057] Put silicon carbide micropowder, iron oxide, alumina, zirconia, boron oxide, and mullite whiskers into a mixer according to the mass percentages of 20%, 30%, 28%, 7%, 5%, and 10%. After fully mixing, put it into a heating kettle, and carry out combustion synthesis heating and melting to form a suspension. Add 3% by mass of polyvinyl alcohol and 1% by mass of paraffin to prepare a casting solution. Use the rotary thermal spraying method to spray it on the surface of the ceramic support coated with the transition layer catalyst layer multiple times. Dry it in an oven at 105 °C and sinter it in a muffle furnace at 1300 °C to form a ceramic / FeAl intermetallic compound composite coating, and obtain a catalytic filtration silicon carbide ceramic membrane.

[0058] Example 2

[0059] The steps are the same as those in Example 1, except that the length of the activated carbon fiber in step (2) is 200 microns.

[0060] Comparative Example 1

[0061] The steps are the same as those in steps (1), (2), and (4) of Example 1, except that there is no step (3) and no catalytic layer is coated.

[0062] Comparative Example 2

[0063] The steps are the same as those in Example 1, except that in step (2), iron oxide and alumina are not added, and there is no FeAl intermetallic compound layer.

[0064] Performance Test

[0065] 1. Physical Performance Test

[0066] The porosity, pore size, air flux, compressive and flexural strengths of the catalytic filtration silicon carbide ceramic membranes obtained from Example 1 and Comparative Examples 1 to 3 were tested respectively. The results are shown in Table 1, and the comparison of flexural strengths is as Figure 1 shown.

[0067] Table 1 Physical Properties of Catalytic Filtration Silicon Carbide Ceramic Membranes

[0068]

[0069] The results show that after adding iron oxide and alumina, the flexural strength of the prepared catalytic filtration silicon carbide ceramic membrane increases significantly.

[0070] 2. Dust Removal Performance and Pollutant Catalytic Degradation Performance Test

[0071] One silicon carbide ceramic membrane was taken from each of Example 1, Example 2, Comparative Example 1 and Comparative Example 2. A circular disc with a diameter of 36 mm was placed in the reactor respectively. The reaction temperature was 300 °C, the toluene concentration was 100 ppm, the NOx concentration was 500 ppm, the SO2 concentration was 100 ppm, the CO2 concentration was 500 ppm, and the H2S concentration was 100 ppm. Nitrogen and oxygen were introduced with an oxygen content of 11% and a total gas flow rate of 1000 ml / min to test their catalytic degradation performance; the dust filtration efficiency test was carried out with reference to the standard ISO 11057 using a filtration simulation test device. The test results are shown in Table 2 and Figure 2 shown.

[0072] Table 2 Removal Efficiencies of Silicon Carbide Ceramic Membranes for Dust and Various Pollutants

[0073]

[0074] The results show that during the preparation of the catalytic filtration silicon carbide ceramic membrane, without dip-coating the catalyst layer, its removal efficiencies for toluene, NOx, SO 2、 CO2 and H2S decrease significantly, and the catalytic degradation performance for pollutants decreases while performing dust filtration.

[0075] All documents mentioned in the present invention are incorporated herein by reference as if each document was individually incorporated by reference. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by this application.

Claims

1. A method for preparing a high-temperature catalytic filtration silicon carbide ceramic membrane, characterized in that, It includes the following steps: (1) Prepare a silicon carbide ceramic support Using silicon carbide micropowder as the aggregate, zirconia as the sintering aid, silicon carbide whiskers and mullite fibers as the reinforcing agents, and polyvinyl alcohol as the binder. After mechanically mixing the raw materials, adding additive paraffin and then quickly mixing to obtain granulated powder. It is formed by cold isostatic pressing, dried in an oven at 100 - 120 °C, and sintered at a high temperature above 1500 °C to obtain the silicon carbide ceramic support; (2) Coat the fiber transition layer Mix mullite fiber, aluminum silicate fiber, activated carbon fiber, polyvinyl alcohol, and deionized water to form a mixed slurry. Mix the mixed slurry with zirconia balls at a mass ratio of 1:1.5 and put them into a ball mill tank. Ball mill for half an hour at a rotation speed of 200 revolutions per minute, add silicon carbide micropowder to obtain a slurry. Uniformly coat the slurry on the surface of the silicon carbide ceramic support in step (1), and dry it at 60 - 80 °C for 2 - 4 h to obtain a ceramic support with a fiber transition layer; (3) Dip - coat the catalyst layer Mix vanadium - molybdenum - cerium - titanium catalyst, dispersant sodium tripolyphosphate, and binder polyvinyl alcohol to form a suspension solution. Immerse the ceramic support prepared in (2) into the suspension solution, and ultrasonically oscillate the suspension solution for dip - coating. Dry it in an oven at 100 - 120 °C to obtain a ceramic support with a catalytic layer; (4) Form an intermetallic compound layer Put silicon carbide micropowder, iron oxide, aluminum oxide, zirconia, boron oxide, and mullite whiskers into a mixer. After fully mixing, put them into a heating kettle, and spread - heat and melt to form a suspension solution. Add additives polyvinyl alcohol and paraffin to prepare a casting solution, and use the method of rotary thermal spraying to spray it on the surface of the ceramic support completed in step (3) multiple times. Dry it in an oven at 100 - 120 °C and then sinter at a high temperature above 1200 °C to form a ceramic / FeAl intermetallic compound composite coating, that is, obtain a catalytic - filtering silicon carbide ceramic membrane.

2. The preparation method according to claim 1, characterized in that, In the step (1), the mass percentage of the aggregate is 80% - 90%, the mass percentage of the sintering aid is 5% - 10%, the mass percentage of the reinforcing agent is 5% - 10%, the mass percentage of the binder is 1% - 2%, the mass percentage of silicon carbide whiskers in the reinforcing agent is 5%, and the mass percentage of mullite fiber is 3%.

3. The preparation method according to claim 1, characterized in that, In the step (2), the mass percentage of mullite fiber is 2% - 10%, the mass percentage of aluminum silicate fiber is 2% - 10%, the mass percentage of activated carbon fiber is 5% - 10%, the mass percentage of polyvinyl alcohol is 3% - 5%, and the mass percentage of deionized water is 60% - 80%.

4. The preparation method according to claim 1, characterized in that In the step (3), the mass percentage of the catalyst is 8% - 12%, the mass percentage of the dispersant sodium tripolyphosphate is 50% - 80%, and the mass percentage of the binder polyvinyl alcohol is 5% - 10%.

5. The preparation method according to claim 1, characterized in that, In the step (4), the mass percentage of silicon carbide micropowder is 20% - 30%, the mass percentage of iron oxide is 15% - 25%, the mass percentage of aluminum oxide is 15% - 25%, the mass percentage of zirconia is 1% - 5%, the mass percentage of boron oxide is 1% - 5%, and the mass percentage of mullite whiskers is 10% - 20%.

6. The preparation method according to claim 1, wherein, The length of the activated carbon fiber is 100 - 400 microns.

7. A catalytic filtration silicon carbide ceramic membrane prepared by the method according to any one of claims 1-6.

8. Use of the catalytic filtration silicon carbide ceramic membrane according to claim 7 in catalytic removal of various pollutants in high-temperature waste gas.

9. The application according to claim 8, wherein: The various pollutants in the high-temperature waste gas include dust, CO2, VOCs, NOx, SO2, and H2S.

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