A porous recrystallized silicon carbide-based catalytic module and a preparation method and application thereof

Abstract

The application provides a porous recrystallized silicon carbide-based catalytic module and a preparation method and application thereof, and belongs to the technical field of catalytic materials. The porous recrystallized silicon carbide-based catalytic module provided by the application comprises a carrier and an active component loaded on the carrier; the carrier is porous recrystallized silicon carbide; and the active component comprises a metal single active component and / or a metal oxide active component. The porous recrystallized silicon carbide-based catalytic module provided by the application has the carrier of porous recrystallized silicon carbide, high porosity, large specific surface area and excellent corrosion resistance, and has excellent catalytic effect and long service life.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a porous recrystallized silicon carbide-based catalytic module, its preparation method, and its application. Background Technology

[0002] In supported catalysts, the support material has a significant impact on the catalytic effect of the active component and the catalyst's lifespan. Support materials for supported catalysts mainly include activated carbon, alumina, or diatomaceous earth, but these materials suffer from poor corrosion resistance.

[0003] Silicon carbide materials exhibit improved corrosion resistance compared to the aforementioned carrier materials and possess excellent high-temperature stability, high mechanical strength, good thermal conductivity, and a low coefficient of thermal expansion, making them considered ideal catalyst carrier materials. However, traditional silicon carbide materials are typically prepared through reaction sintering processes, resulting in products with high density, low porosity (around 10%), and small specific surface area (<7m²). 2 Moreover, the high amount of free silicon reduces its corrosion resistance, making it unable to meet the requirements of high specific surface area and corrosion resistance for industrial catalytic reactions. Summary of the Invention

[0004] The purpose of this invention is to provide a porous recrystallized silicon carbide-based catalytic module, its preparation method, and its application. The porous recrystallized silicon carbide-based catalytic module provided by this invention uses porous recrystallized silicon carbide as a carrier, has high porosity, large specific surface area, and excellent corrosion resistance. The porous recrystallized silicon carbide-based catalytic module has excellent catalytic effect and long service life.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a porous recrystallized silicon carbide-based catalytic module, wherein the porous recrystallized silicon carbide-based catalytic module includes a support and an active component supported on the support; the support is porous recrystallized silicon carbide; the active component includes a metal elemental active component and / or a metal oxide active component;

[0007] The preparation method includes the following steps:

[0008] Silicon carbide, cellulose, dextran, vegetable oil, glycerol, and water are mixed to obtain a slurry. The slurry comprises 65-70% first silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the first silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 10±1 μm accounts for more than 50% of the total mass of the first silicon carbide.

[0009] The slurry is extruded to obtain a preform;

[0010] The blank is dried and subjected to a first sintering to obtain a first sintered body;

[0011] The first sintered body is subjected to a first coating treatment using a first coating reagent to obtain a first coated sintered body. The first coating reagent includes 65-70% second silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the second silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 5±0.5 μm accounts for more than 50% of the total mass of the second silicon carbide.

[0012] The first coated sintered body is subjected to a second sintering to obtain the porous recrystallized silicon carbide.

[0013] Using the porous recrystallized silicon carbide as a support, active components are loaded onto the support to obtain the porous recrystallized silicon carbide-based catalytic module.

[0014] Preferably, the active metal element component includes one or more of platinum, palladium, ruthenium, gold, silver, copper, nickel, cobalt, and molybdenum; the active metal oxide component includes one or more of iron oxide, molybdenum oxide, zirconium oxide, cerium oxide, manganese oxide, copper oxide, cobalt oxide, titanium oxide, and vanadium oxide.

[0015] Preferably, the loading of the active component in the porous recrystallized silicon carbide-based catalytic module is 1~20wt%.

[0016] Preferably, the active component forms an active layer on the carrier, and the thickness of the active layer is 0.1~10μm.

[0017] Preferably, the porous recrystallized silicon carbide has a structure including a foam-like structure, a honeycomb structure, or a corrugated structure; the macroscopic shape of the porous recrystallized silicon carbide includes a plate-like, columnar, or tubular shape; the pore size of the porous recrystallized silicon carbide is 0.05~10μm, the porosity is 45~85%, and the specific surface area is 18~80m². 2 / g.

[0018] Preferably, the temperature of the first sintering is 2440~2460℃, and the holding time is 1~3h; the temperature of the second sintering is 2190~2210℃, and the holding time is 1~3h.

[0019] Preferably, after the second sintering, the material obtained after the second sintering is further subjected to a second coating-sintering to obtain the porous recrystallized silicon carbide; the second coating-sintering includes sequentially performing a second coating treatment and a third sintering, wherein the coating reagent used in the second coating treatment includes 65-70% third silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol and the balance water, wherein the particle size of the third silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 0.6±0.1 μm accounts for more than 50% of the total mass of the third silicon carbide;

[0020] Preferably, after the second coating-sintering, the material obtained after the third sintering is further subjected to a third coating-sintering to obtain the porous recrystallized silicon carbide; the third coating-sintering includes sequentially performing a third coating treatment and a fourth sintering, wherein the coating reagent used in the third coating treatment includes 65-70% fourth silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance being water, wherein the particle size of the fourth silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 0.5±0.07 μm accounts for more than 50% of the total mass of the fourth silicon carbide.

[0021] The present invention provides a porous recrystallized silicon carbide-based catalytic module prepared by the preparation method described above.

[0022] This invention provides the application of the porous recrystallized silicon carbide-based catalytic module described above in wastewater catalytic ozone oxidation, catalytic hydrogenation reaction, indoor air purification, or catalytic decomposition of oil fumes.

[0023] Beneficial effects: The porous recrystallized silicon carbide-based catalytic module provided by the present invention uses porous recrystallized silicon carbide as a carrier, which has high porosity, large specific surface area and excellent corrosion resistance. The porous recrystallized silicon carbide-based catalytic module has excellent catalytic effect and long service life.

[0024] Furthermore, the raw materials for the porous recrystallized silicon carbide described in this invention are readily available, the preparation method is simple, no harmful templates and reagents are required, the environmental impact is small, and it can be directly molded into various complex configurations, making it suitable for large-scale production. Attached Figure Description

[0025] Figure 1 This is a photograph of a foam-like porous recrystallized silicon carbide.

[0026] Figure 2 This is a photograph of honeycomb-shaped porous recrystallized silicon carbide.

[0027] Figure 3Microscopic and macroscopic images of tubular porous recrystallized silicon carbide;

[0028] Figure 4 A physical image of a porous recrystallized silicon carbide-based catalytic module suitable for use in pipelines;

[0029] Figure 5 This is a structural diagram of the porous recrystallized silicon carbide support in Example 1. Detailed Implementation

[0030] The present invention provides a porous recrystallized silicon carbide-based catalytic module, comprising a support and an active component supported on the support; the support is porous recrystallized silicon carbide; the active component comprises a metal elemental active component and / or a metal oxide active component.

[0031] The porous recrystallized silicon carbide-based catalytic module provided by this invention includes a support, wherein the support is porous recrystallized silicon carbide. In one embodiment of this invention, the pore size of the porous recrystallized silicon carbide can be 0.05~10 μm, specifically 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 5 μm, or 10 μm; the porosity can be 45~85%, specifically 45%, 50%, 55%, 60%, 70%, 80%, or 85%; and the specific surface area is 18~80 m². 2 / g, which can be further increased to 20m 2 / g、30m 2 / g、40m 2 / g, 50m 2 / g、53m 2 / g、60m 2 / g、70m 2 / g or 80m 2 / g; The structure of the porous recrystallized silicon carbide may include a foam-like structure, a honeycomb structure, or a corrugated structure. The macroscopic shape of the porous recrystallized silicon carbide may include a plate-like, columnar, or tubular shape, or other irregular shapes. The plate-like shape may be a flat plate. The columnar shape may include a square columnar shape, a fan-shaped columnar shape, or a cylindrical shape. The tubular shape may be a single-channel tubular shape or a multi-channel tubular shape. The present invention does not have any special limitations on this. The appropriate structure and macroscopic shape can be selected according to actual needs.

[0032] Figure 1 This is a photograph of a foam-like porous recrystallized silicon carbide, which has a macroscopic shape of a flat plate. Figure 2 The image shows a honeycomb porous recrystallized silicon carbide. The macroscopic shapes on the left are square columnar and fan-shaped columnar, while the macroscopic shape on the right is square columnar. Figure 3The images show microscopic and macroscopic views of tubular porous recrystallized silicon carbide. The left side shows the microscopic view, which shows the pore structure on the surface of the pore walls in the porous recrystallized silicon carbide. The right side shows macroscopic views of single-channel and multi-channel tubular porous recrystallized silicon carbide. Figure 4 The images show actual models of porous recrystallized silicon carbide-based catalytic modules suitable for use in pipes. The left image shows a model of a porous recrystallized silicon carbide-based catalytic module suitable for use in circular pipes, while the right image shows a model of a porous recrystallized silicon carbide-based catalytic module suitable for use in square pipes.

[0033] The porous recrystallized silicon carbide-based catalytic module provided by this invention includes an active component supported on the support, wherein the active component includes a metallic elemental active component and / or a metal oxide active component. As one embodiment of this invention, the metallic elemental active component may include one or more of platinum, palladium, ruthenium, gold, silver, copper, nickel, cobalt, and molybdenum, specifically platinum; the metallic elemental active component may be metal nanoparticles. As one embodiment of this invention, the metal oxide active component may include one or more of iron oxide, molybdenum oxide, zirconium oxide, cerium oxide, manganese oxide, copper oxide, cobalt oxide, titanium oxide, and vanadium oxide, specifically iron oxide (e.g., Fe2O3), molybdenum oxide (e.g., MoO2), a complex formed by zirconium oxide and cerium oxide, or a complex formed by manganese oxide, copper oxide, and cerium oxide (e.g., Mn). 1.5 Cu 1.5 Ce 0.2 O x ).

[0034] As one embodiment of the present invention, the loading of the active component in the porous recrystallized silicon carbide-based catalytic module can be 1 to 20 wt%, specifically 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, or 20 wt%.

[0035] In one embodiment of the present invention, the active component forms an active layer on the carrier, and the thickness of the active layer can be 0.1~10μm.

[0036] This invention provides a method for preparing the porous recrystallized silicon carbide-based catalytic module described above, comprising the following steps:

[0037] Silicon carbide, cellulose, dextran, vegetable oil, glycerol, and water are mixed to obtain a slurry. The slurry comprises 65-70% first silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the first silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 10±1 μm accounts for more than 50% of the total mass of the first silicon carbide.

[0038] The slurry is extruded to obtain a preform;

[0039] The blank is dried and subjected to a first sintering to obtain a first sintered body;

[0040] The first sintered body is subjected to a first coating treatment using a first coating agent to obtain a first coated sintered body. The first coating treatment includes 65-70% second silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the second silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 5±0.5 μm accounts for more than 50% of the total mass of the second silicon carbide.

[0041] The first coated sintered body is subjected to a second sintering to obtain porous recrystallized silicon carbide.

[0042] Using porous recrystallized silicon carbide as a support, active components are loaded onto the support to obtain the porous recrystallized silicon carbide-based catalytic module.

[0043] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0044] This invention involves mixing silicon carbide, cellulose, dextran, vegetable oil, glycerol, and water to obtain a slurry. In one embodiment of the present invention, the slurry comprises, by mass fraction, 65-70% silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance being water; further, the slurry comprises 68% silicon carbide, 5% cellulose, 2% dextran, 1% vegetable oil, 2% glycerol, and 22% water; the silicon carbide may specifically be α-SiC, the purity of the silicon carbide is 99.8 wt%, the particle size of the silicon carbide is 0.1-15 μm, wherein silicon carbide with a particle size of 10 ± 1 μm accounts for more than 50% of the total mass of the silicon carbide; the glycerol is food-grade glycerol with a purity of 98%; the dextran is dextran XT300; the vegetable oil may include one or more of soybean oil, corn oil, and rice bran oil, specifically rice bran oil; and the water is purified water. In this invention, silicon carbide is used as the matrix skeleton material; glycerol and dextran are used as binders; cellulose can form binding force; and vegetable oil and water are used as dispersants to ensure that the raw materials can be dispersed and mixed evenly. This invention controls the amount of each component within the above range, which is conducive to forming a stable molding material and to forming a more uniform pore size during the subsequent sintering process.

[0045] After obtaining the slurry, the present invention extrudes the slurry to obtain a preform. The present invention does not impose special limitations on the extrusion molding operation conditions; conditions well known to those skilled in the art can be used.

[0046] After obtaining the green body, the present invention dries and first sinterstensibly sinterstensibly to obtain a first sintered body. In this invention, degumming is further performed between drying and the first sintering. The degumming temperature can be 115~125℃, specifically 115℃, 118℃, 120℃, 122℃, or 125℃; the degumming time can be 2~4 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. This invention effectively removes vegetable oil and glycerol through degumming.

[0047] In one embodiment of the present invention, the temperature of the first sintering can be 2440~2460℃, specifically 2450℃; the holding time can be 1~3h, specifically 2h; the present invention preferably uses a gradient heating program to raise the temperature to the first sintering temperature, the gradient heating program being as follows: raising the temperature from room temperature to 590~610℃ at a rate of 1~2℃ / min and holding for 0.5~1.5h, then raising the temperature from 590~610℃ to 1590~1610℃ at a rate of 5~10℃ / min and holding for 0.5~1.5h, then raising the temperature from 1590~610℃ to 1590~1610℃ at a rate of 3~5℃ / min. The temperature is raised from 90~1610℃ to 2190~2210℃ and held for 1.5~2.5h, then raised to the first sintering temperature at a rate of 3~5℃ / min. In this embodiment, the gradient heating program is as follows: the temperature is raised from room temperature to 600℃ at a rate of 1.5℃ / min and held for 1h, then raised to 1600℃ at a rate of 8℃ / min and held for 1h, then raised to 2200℃ at a rate of 4℃ / min and held for 2h, and finally raised to the first sintering temperature at a rate of 4℃ / min. After the first sintering, the present invention preferably further includes cooling to room temperature at a rate of 2~5℃ / min, specifically 3℃ / min. The porous recrystallized silicon carbide prepared by the above method of the present invention has a pore size of 5~10μm.

[0048] After obtaining the first sintered body, the present invention uses a first coating agent to perform a first coating treatment on the first sintered body to obtain a first coated sintered body. The first coating agent includes 65-70% second silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the second silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 5±0.5 μm accounts for more than 50% of the total mass of the second silicon carbide. Further, the first coating agent comprises 68% silicon carbide, 5% cellulose, 2% dextran, 1% vegetable oil, 2% glycerol, and 22% water; the silicon carbide may specifically be α-SiC, and the purity of the silicon carbide is 99.8 wt%; the glycerol is food-grade glycerol with a purity of 98%; the dextran is dextran XT300; the vegetable oil may include one or more of soybean oil, corn oil, and rice bran oil, specifically rice bran oil; and the water is purified water.

[0049] After obtaining the first coated sintered body, the present invention performs a second sintering on the first coated sintered body to obtain porous recrystallized silicon carbide.

[0050] In this invention, the second sintering temperature can be 2190~2210℃, specifically 2200℃; the holding time can be 1~3h, specifically 2h; this invention preferably uses a gradient heating program to raise the temperature to the second sintering temperature, the gradient heating program is as follows: raising the temperature from room temperature to 590~610℃ at a rate of 1~2℃ / min and holding for 0.5~1.5h, then raising the temperature from 590~610℃ to 1 at a rate of 5~10℃ / min. The temperature is initially set at 590~1610℃ and held for 0.5~1.5h, then increased from 1590~1610℃ to the second sintering temperature at a rate of 3~5℃ / min. In this embodiment, the gradient heating program is as follows: the temperature is increased from room temperature to 600℃ at a rate of 1.5℃ / min and held for 1h, then increased from 600℃ to 1600℃ at a rate of 8℃ / min and held for 1h, and then increased from 1600℃ to the second sintering temperature at a rate of 4℃ / min. After the second sintering, the invention preferably further includes cooling to room temperature at a rate of 2~5℃ / min, specifically 3℃ / min. The average pore size of the porous recrystallized silicon carbide prepared by the above method of the present invention is 1μm.

[0051] In one embodiment of the present invention, the second sintering preferably further includes a second coating-sintering of the material obtained after the second sintering to obtain the porous recrystallized silicon carbide. In another embodiment of the present invention, the second coating-sintering includes sequentially performing a second coating treatment and a third sintering. The components and proportions of the coating reagent used in the second coating treatment are consistent with the slurry described in the above technical solution, except that the silicon carbide with a particle size of 0.6±0.1μm accounts for more than 50% of the total mass of silicon carbide (the particle size of silicon carbide is 0.1~15μm) in the coating reagent used in the second coating treatment. The temperature of the third sintering can be 2190~2210℃, specifically 2200℃; the holding time can be 1.5~2.5h, specifically 2h. The present invention preferably employs a gradient heating program to raise the temperature to the third sintering temperature, specifically the same gradient heating program used to raise the temperature of the second sintering. After the third sintering, the present invention preferably further includes cooling to room temperature, wherein the cooling rate can be 2~5℃ / min, specifically 3℃ / min. The average pore size of the porous recrystallized silicon carbide prepared by the above method of the present invention is 100 nm.

[0052] In one embodiment of the present invention, the second coating-sintering preferably further includes a third coating-sintering of the material obtained after the third sintering to obtain the porous recrystallized silicon carbide. In another embodiment of the present invention, the third coating-sintering includes sequentially performing a third coating treatment and a fourth sintering. The composition and proportion of the coating reagent used in the third coating treatment are consistent with the slurry described in the above technical solution, except that the silicon carbide with a particle size of 0.5±0.07μm accounts for more than 50% of the total mass of silicon carbide (the particle size of silicon carbide is 0.1~15μm) in the coating reagent used in the third coating treatment. The temperature of the fourth sintering can be 1800~1900℃, specifically 1850℃; the holding time can be 0.5~1.5h, specifically 1h. The present invention preferably employs a gradient heating program to raise the temperature to the fourth sintering temperature, specifically the same gradient heating program used to raise the temperature of the second sintering. After the fourth sintering, the present invention preferably further includes cooling to room temperature, wherein the cooling method can be furnace cooling. The average pore size of the porous recrystallized silicon carbide prepared by the above method of the present invention is 50 nm.

[0053] The porous recrystallized silicon carbide of this invention possesses a dual continuous pore structure (macropore-mesopore composite structure), exhibiting high specific surface area, strong resistance to acid and alkali corrosion, excellent mass transfer performance, high mechanical strength, good thermal conductivity, and excellent high-temperature resistance and thermal shock resistance. Using it as a carrier to load active components ensures that the active components do not detach while retaining the characteristics of porous structure and large specific surface area. The resulting porous recrystallized silicon carbide-based catalytic module exhibits excellent catalytic effect and a long service life. Specifically, the porous recrystallized silicon carbide of this invention has a composite structure of macropores (0.45~10μm) and mesopores (<50nm), with good pore connectivity, a porosity of 45~85%, and a specific surface area of ​​18~80m². 2 / g, which is beneficial for improving mass transfer. At the same time, the porous recrystallized silicon carbide of the present invention has good thermal conductivity (thermal conductivity coefficient 270W / (m·K)) and electrical conductivity, which is beneficial for the diffusion of reaction heat and avoidance of hot spot formation; it has high mechanical strength, with a compressive strength of up to 224MPa, a three-point bending strength ≥15MPa, and a long service life; the open structure is beneficial for reducing fluid resistance.

[0054] After obtaining porous recrystallized silicon carbide, this invention uses porous recrystallized silicon carbide as a support, and loads active components onto the support to obtain the porous recrystallized silicon carbide-based catalytic module. As one embodiment of this invention, the loading method may include impregnation, spraying, precipitation, or chemical vapor deposition. As one embodiment of this invention, the impregnation method may specifically be an equal-volume impregnation method, which includes: using a solution containing a precursor material as the impregnation liquid to impregnate the porous recrystallized silicon carbide, followed by drying and calcination to obtain the porous recrystallized silicon carbide-based catalytic module; wherein the precursor material is the precursor material corresponding to the active component, and this invention does not specifically limit the type of precursor material, as long as the target active component is obtained; to improve the dispersibility of the precursor material, the solution containing the precursor material may include a dispersant, specifically sodium polyacrylate; to improve the porous recrystallized silicon carbide... Regarding the interaction between crystalline silicon carbide and precursor materials, the porous recrystallized silicon carbide can be pre-hydroxylated on its surface before use. This invention does not specifically limit the method of surface hydroxylation; any method well-known to those skilled in the art can be used. The calcination temperature can be 300~1050℃, specifically 350℃, 450℃, 550℃, or 1000℃, and the holding time can be 3~5h, specifically 3h, 4h, or 5h. Depending on the type of target active component, this invention can also perform reduction after impregnation and drying, or reduction after calcination. This invention does not specifically limit the reagents and conditions used for reduction. In one embodiment of the present invention, the spraying method includes: spraying a liquid containing a precursor material onto the porous recrystallized silicon carbide, followed by drying and calcination to obtain the porous recrystallized silicon carbide-based catalytic module; wherein the precursor material is the precursor material corresponding to the active component, and the present invention does not have a special limitation on the type of precursor material, as long as the target active component is obtained; the calcination temperature can be 550~850℃, specifically 600℃, 700℃ or 800℃, and the holding time can be 3~5h, specifically 3h, 4h or 5h. The present invention does not have a special limitation on the specific operating steps and conditions of the precipitation method and chemical vapor deposition method, and operating steps and conditions well known to those skilled in the art can be used.

[0055] This invention provides the application of the porous recrystallized silicon carbide-based catalytic module described above in wastewater catalytic ozone oxidation, catalytic hydrogenation, indoor air purification, or catalytic decomposition of cooking fumes. This invention does not specifically limit the application method of the porous recrystallized silicon carbide-based catalytic module; for example, the porous recrystallized silicon carbide-based catalytic module can be assembled into a specific reactor (such as a reaction vessel or pipeline) to carry out catalytic reactions according to specific application scenarios.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] The silicon carbide (specifically α-SiC) used in the following experiments had a purity of 99.8% and was purchased from Shenyang Changxin New Materials Co., Ltd.; the glycerol used was food-grade glycerol with a purity of 98%; the dextran used was dextran XT300; the vegetable oil used was rice bran oil; and the water used was purified water.

[0058] Example 1

[0059] (1) Preparation of porous recrystallized silicon carbide support:

[0060] Silicon carbide (with a particle size of 0.1~15μm, of which 50% is silicon carbide with a particle size of 10±1μm), glycerol, dextran, cellulose, vegetable oil, and water are mixed in a mass ratio of 68:2:2:5:1:22 to obtain a mixed slurry. The mixed slurry is fed into a vacuum extruder for extrusion to obtain a preform (specifically a multi-channel preform, where the inner diameter of each channel in the multi-channel preform is 4mm). The preform is placed in a degumming furnace and degummed at 120℃ for 3 hours to remove vegetable oil and glycerol, resulting in a degummed preform.

[0061] The degummed preform was placed in a vacuum induction sintering furnace and heated from room temperature (25°C) to 600°C at a rate of 1.5°C / min and held for 1 hour. Then, the temperature was increased from 600°C to 1600°C at a rate of 8°C / min and held for 1 hour. After that, the temperature was increased from 1600°C to 2200°C at a rate of 4°C / min and held for 2 hours. Then, the temperature was increased from 2200°C to 2450°C at a rate of 4°C / min and held for the first sintering for 2 hours. Finally, the temperature was decreased to room temperature at a rate of 3°C / min to obtain the first sintered body (pore size of 5~10μm).

[0062] The first sintered body was subjected to a first coating treatment using a first coating reagent to obtain a first coated sintered body. The formulation of the first coating reagent was the same as that of the above-mentioned mixed slurry, except that the silicon carbide with a particle size of 5±0.5μm accounted for 50% of the total mass of silicon carbide (the particle size of silicon carbide was 0.1~15μm). The first coated sintered body was placed in a vacuum induction sintering furnace and heated from room temperature to 600℃ at a rate of 1.5℃ / min and held for 1h. Then, the temperature was increased from 600℃ to 1600℃ at a rate of 8℃ / min and held for 1h. Then, the temperature was increased from 1600℃ to 2200℃ at a rate of 4℃ / min and held for a second sintering for 2h. Finally, the temperature was decreased to room temperature at a rate of 3℃ / min to obtain a second sintered body with an average pore size of 1μm.

[0063] The second sintered body was subjected to a second coating treatment using a second coating agent to obtain a second coated sintered body. The formulation of the second coating agent was the same as that of the above-mentioned mixed slurry, except that silicon carbide with a particle size of 0.6±0.1μm accounted for 50% of the total mass of silicon carbide (the particle size of silicon carbide is 0.1~15μm) in the second coating agent. The second coated sintered body was placed in a vacuum induction sintering furnace and heated from room temperature to 600℃ at a rate of 1.5℃ / min and held for 1 hour. Then, the temperature was increased from 600℃ to 1600℃ at a rate of 8℃ / min and held for 1 hour. Then, the temperature was increased from 1600℃ to 2200℃ at a rate of 4℃ / min and held for a third sintering for 2 hours. Finally, the temperature was decreased to room temperature at a rate of 3℃ / min to obtain a porous recrystallized silicon carbide support (specifically, a multi-channel porous recrystallized silicon carbide support, the structure of which is shown in the figure). Figure 5 As shown, a support layer is formed after the first sintering, a transition layer is formed after the first coating treatment and the second sintering, and a separation layer is formed after the second coating treatment and the third sintering. The average pore size is 100 nm, the porosity is 50%, and the specific surface area is 20 m². 2 / g, the three-point flexural strength is 37MPa;

[0064] (2) Loaded active components:

[0065] The active component raw material, dispersant, and deionized water are mixed in a mass ratio of 40:2:58 to obtain a mixed solution. The active component raw material is a compound of zirconium oxide and cerium oxide in a mass ratio of 40:60, and the dispersant is sodium polyacrylate. The mixed solution is used as an impregnation liquid to impregnate the porous recrystallized silicon carbide support in an equal volume. After that, it is allowed to stand for 12 hours at a temperature of 30°C and a relative humidity of 70%. Finally, it is calcined in air at 1000°C for 4 hours to obtain a porous recrystallized silicon carbide-based catalytic module (specifically including a porous recrystallized silicon carbide support and an active component supported on the porous recrystallized silicon carbide support, wherein the active component is zirconium oxide and cerium oxide, and the active component forms an active layer with a thickness of 0.1~10 μm on the porous recrystallized silicon carbide support).

[0066] The porosity of the porous recrystallized silicon carbide-based catalytic module was determined using a mercury porosimeter. The results showed a porosity of 45%, primarily consisting of interconnected pores. The specific surface area (BET) of the porous recrystallized silicon carbide-based catalytic module was 18 m². 2 / g.

[0067] The performance of the porous recrystallized silicon carbide-based catalytic module prepared in Example 1 was tested, as follows:

[0068] The porous recrystallized silicon carbide-based catalytic module was used for ozone catalytic oxidation treatment of pharmaceutical factory wastewater (COD: 4000~5000mg / L, BOD5: 1000~1200mg / L, SS: 1200~1500mg / L, color: 100~300), wherein the treatment conditions included: wastewater pH value of 10, ozone concentration of 200mg / h, treatment temperature of 35℃, and treatment time of 1000h.

[0069] The results showed that the oxidation decomposition rates of COD and BOD5 in the effluent were both >99.5%, and the SS in the effluent was <1 mg / L, with a color <5. After continuous operation at 35℃ for 1000 h, the porous recrystallized silicon carbide-based catalytic module showed no significant deactivation. This indicates that the porous recrystallized silicon carbide-based catalytic module prepared in Example 1 has excellent ozone catalytic oxidation performance.

[0070] Example 2

[0071] (1) Preparation of porous recrystallized silicon carbide support: Refer to step (1) of Example 1, that is, the porous recrystallized silicon carbide support in this example is a multi-channel porous recrystallized silicon carbide support.

[0072] (2) Loading active components: The porous recrystallized silicon carbide support was ultrasonically cleaned with deionized water to remove surface impurities, then dried at 110°C for 3 hours, and then calcined at 600°C for 3 hours in air. After calcination, the obtained material was immersed in a 0.5 mol / L sodium hydroxide (NaOH) solution and treated at 80°C with continuous stirring for 12 hours to achieve surface hydroxylation. Afterwards, it was washed with deionized water until neutral and then dried. The surface hydroxylation formed abundant silanol groups (-Si-OH), thereby improving the interaction between the support and the subsequently introduced iron precursor. Ferric nitrate nonahydrate (Fe(NO3)3·9H2O) was used as the iron precursor and dissolved in deionized water to prepare a ferric nitrate solution. The ferric nitrate solution was used as the impregnation solution. The porous recrystallized silicon carbide support treated as described above was impregnated with an equal volume, and then allowed to stand for 12 hours at 30°C and 70% relative humidity to ensure that the ferric nitrate solution fully penetrated into the pores of the porous recrystallized silicon carbide support. The impregnated material was then dried at 100°C for 10 hours, and subsequently calcined in air at 450°C for 4 hours to decompose the ferric nitrate into catalytically active Fe2O3 and firmly anchor it to the surface of the porous recrystallized silicon carbide support, thus obtaining a porous recrystallized silicon carbide-based catalytic module (specifically including a porous recrystallized silicon carbide support and an active component loaded on the porous recrystallized silicon carbide support, wherein the active component is Fe2O3, and the active component forms an active layer with a thickness of 0.1~10 μm on the porous recrystallized silicon carbide support).

[0073] The performance of the porous recrystallized silicon carbide-based catalytic module prepared in Example 2 was tested, as follows:

[0074] The porous recrystallized silicon carbide-based catalytic module (denoted as Fe2O3 / SiC catalyst) was used for ozone catalytic oxidation treatment of coking wastewater (pH value 10±0.5, COD 4000~15000mg / L). The treatment conditions included: ozone concentration of 30mg / L, ensuring full gas-liquid contact through stirring, treatment temperature of 30℃, and treatment time of 3h.

[0075] The results showed that compared with ozone alone without the addition of Fe2O3 / SiC catalyst, the COD removal rate was increased by 71% when ozone oxidation was catalyzed by the Fe2O3 / SiC catalyst prepared in Example 2. Furthermore, because the Fe2O3 / SiC catalyst promoted the decomposition of ozone to generate more oxidizing free radicals (such as ·OH), the ozone utilization rate increased from 0.44 g-COD / g-O3 when ozone oxidation was used alone to 1.42 g-COD / g-O3, an efficiency improvement of more than 3 times. In practical large-scale applications, using the Fe2O3 / SiC catalyst to catalyze ozone oxidation can reduce ozone consumption to below 60 mg / L, while simultaneously reducing operating costs by approximately 50%.

[0076] The porous recrystallized silicon carbide support in this invention possesses high mechanical strength and hardness, enabling it to maintain its integrity for extended periods in reactors with high hydraulic shear forces, such as fluidized beds, exhibiting excellent wear resistance. Due to the strong interaction between the active component Fe2O3 and the porous recrystallized silicon carbide support, the leaching of the active component iron is extremely low. This means the catalyst can maintain good activity for a long time, has a long service life, and a low risk of secondary pollution. After use, the Fe2O3 / SiC catalyst can be recovered through simple sedimentation or filtration. After cleaning, drying, and calcination, under the aforementioned operating conditions, its catalytic activity does not significantly decrease after 10 cycles.

[0077] Example 3

[0078] (1) Preparation of porous recrystallized silicon carbide support: Refer to step (1) of Example 1, that is, the porous recrystallized silicon carbide support in this example is a multi-channel porous recrystallized silicon carbide support.

[0079] (2) Loading active components: The porous recrystallized silicon carbide support was treated at 90°C and under vacuum for 10 min to remove surface-adsorbed impurities and increase surface active sites; the porous recrystallized silicon carbide support was impregnated with an equal volume of chloroplatinic acid (H2PtCl6) aqueous solution (Pt concentration of 8 mg / mL) as the impregnation solution, and then allowed to stand at 30°C and 70% relative humidity for 12 h to promote the dispersion of H2PtCl6 on the surface of the porous recrystallized silicon carbide support. It was then air-dried and dried at 100°C for 10 h to obtain the precursor material; The precursor material was placed in a 3 wt% sodium formate (NaCOOH) aqueous solution, wherein the molar ratio of sodium formate to platinum was 10:1. The solution was refluxed at 95°C for 3 h to achieve platinum reduction. After reflux, the solution was filtered, and the filter cake was washed with deionized water and dried at 100°C for 5 h to obtain a porous recrystallized silicon carbide-based catalytic module (specifically including a porous recrystallized silicon carbide support and an active component loaded on the porous recrystallized silicon carbide support, wherein the active component is Pt nanoparticles and the loading amount of the active component on the porous recrystallized silicon carbide support is 5 wt%).

[0080] The porous recrystallized silicon carbide-based catalytic module prepared in Example 3 was used for catalytic hydrogenation reaction, as follows:

[0081] (1) Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol: The porous recrystallized silicon carbide-based catalytic module (denoted as Pt / SiC catalyst) prepared in Example 3 was used. Isopropanol-water mixture (volume ratio of isopropanol to water was 1:1) was used as solvent. The initial concentration of cinnamaldehyde was 0.05M. The reaction was carried out at room temperature and hydrogen pressure of 2MPa for 60min. The results showed that the conversion rate of cinnamaldehyde could reach 90.5%, and the selectivity of the target product cinnamyl alcohol was 85.2%. In comparison, under the same conditions, the conversion rate and selectivity of Pt / Al2O3 and Pt / C catalysts were significantly lower than those of Pt / SiC catalyst. The Pt / Al2O3 catalyst (Pt content 0.5 wt%) was purchased from Shaanxi Kaida Chemical Co., Ltd., with a conversion rate of 40.6% for cinnamaldehyde and a selectivity of 73.2% for cinnamyl alcohol. The Pt / C catalyst (Alfa-A11186.06, Pt content 0.5 wt%) was purchased from Sinopharm Chemical Reagent Co., Ltd., with a conversion rate of 73.4% for cinnamaldehyde and a selectivity of 55.3% for cinnamyl alcohol.

[0082] Stability is a key indicator for evaluating the practical application value of a catalyst. After the Pt / SiC catalyst was used 10 times consecutively in the hydrogenation reaction of cinnamaldehyde, its catalytic activity (conversion rate) and selectivity showed virtually no decrease, indicating that the Pt / SiC catalyst possesses excellent stability. This is mainly attributed to the excellent chemical stability and mechanical strength of the porous recrystallized silicon carbide support, which effectively prevents the active components from agglomerating or being lost during the reaction.

[0083] (2) Preparation of furfural alcohol by hydrogenation: The porous recrystallized silicon carbide-based catalytic module prepared in Example 3 was used with water as solvent and an initial furfural concentration of 1 wt%. The reaction was carried out at room temperature and a hydrogen pressure of 2 MPa for 6 h. The results showed that the conversion rate of furfural was 95% and the selectivity of furfural alcohol was 98%. This indicates that the porous recrystallized silicon carbide-based catalytic module prepared in Example 3 can efficiently convert furfural to furfural alcohol, showing excellent green catalytic performance.

[0084] Example 4

[0085] (1) Preparation of porous recrystallized silicon carbide carrier: Refer to step (1) of Example 1, except that the porous recrystallized silicon carbide carrier in this example is a honeycomb porous recrystallized silicon carbide carrier with a size of 100 mesh / square inch, a wall thickness of about 0.3 mm, and a three-point bending strength of 5 MPa.

[0086] (2) Loading the active component: The porous recrystallized silicon carbide support was soaked in dilute nitric acid (concentration of 5wt%) at room temperature for 2h, then rinsed with deionized water until neutral, and finally dried at 110℃ for 2h to remove any impurities on the surface and increase the surface hydroxyl groups, which is beneficial for the subsequent anchoring of the active component Pt; the dried porous recrystallized silicon carbide support was impregnated with an equal volume of chloroplatinic acid (H2PtCl6) aqueous solution (Pt concentration of 8mg / mL), then stood at room temperature and relative humidity of 70% for 4h, and then dried at 80℃ for 6h. The dried material was placed in a muffle furnace and heated from room temperature to 350℃ at a rate of 2℃ / min in air atmosphere and calcined for 3h to allow chloroplatinic acid to form PtO. x The sintered material was placed in a tube furnace and, in a mixed atmosphere of hydrogen and nitrogen (hydrogen fraction 5%), the temperature was increased from room temperature to 300°C at a rate of 5°C / min and held for 3 hours for reduction activation, so that PtO x The species were reduced to highly catalytically active Pt nanoparticles to obtain a porous recrystallized silicon carbide-based catalytic module (specifically including a porous recrystallized silicon carbide support and an active component supported on the porous recrystallized silicon carbide support, wherein the active component is Pt nanoparticles and the loading amount of the active component on the porous recrystallized silicon carbide support is 8 wt%).

[0087] The porous recrystallized silicon carbide-based catalytic module prepared in Example 4 was used for catalytic purification of indoor air, and compared with a porous recrystallized silicon carbide support (denoted as blank SiC support), as follows:

[0088] Set up a test gas path system, including a mass flow controller, a gas mixing chamber, a fixed-bed reactor, a temperature control system, and an online gas chromatograph or Fourier transform infrared spectrometer for exhaust gas analysis;

[0089] Simulated indoor air conditions: room temperature (25℃), relative humidity 50%;

[0090] Test gas conditions: The target pollutants were formaldehyde and toluene, with an initial formaldehyde concentration of 1 ppm and an initial toluene concentration of 1 ppm (simulating typical indoor pollution levels); the air velocity was set to GHSV 20000 h⁻¹. -1 (Simulating the working conditions of a high-volume air purifier).

[0091] Table 1 shows the test results of the catalytic purification of indoor air. It can be seen that the porous recrystallized silicon carbide-based catalytic module provided by this invention has an extremely high removal rate of formaldehyde at room temperature and can achieve complete conversion of toluene at a relatively low temperature of 150℃, far lower than the temperature required for traditional thermal combustion (usually >400℃), demonstrating significant energy-saving advantages. Furthermore, after 100 hours of continuous testing, the catalytic activity decay was minimal (<0.1%), proving that the strong interaction between the porous recrystallized silicon carbide support and Pt nanoparticles gives the porous recrystallized silicon carbide-based catalytic module excellent stability. In addition, the high porosity and interconnected structure of the porous recrystallized silicon carbide-based catalytic module ensure low airflow resistance, making it suitable for indoor air purification equipment requiring low airflow resistance; combined with an electric heating module, the air can be preheated to approximately 150℃, achieving efficient and continuous purification of recalcitrant VOCs.

[0092] Table 1. Test results of catalytic purification of indoor air

[0093]

[0094] Example 5

[0095] (1) Preparation of porous recrystallized silicon carbide carrier: Refer to step (1) of Example 1, except that the porous recrystallized silicon carbide carrier in this example is a honeycomb porous recrystallized silicon carbide carrier with a size of 100 mesh / square inch, a wall thickness of about 0.3 mm, and a three-point bending strength of 20 MPa.

[0096] (2) Loading active components: The bulk honeycomb porous recrystallized silicon carbide support was cut into cylinders with a size of Φ20mm×30mm. The cylinders were ultrasonically cleaned for 30min each with dilute nitric acid (concentration of 3wt%), deionized water and anhydrous ethanol to remove impurities and dust adsorbed on the surface. The cleaned material was dried at 110℃ for 4h and then placed in a desiccator to cool to room temperature for later use. Manganese nitrate (Mn(NO3)2·4H2O), copper nitrate (Cu(NO3)2·3H2O) and cerium nitrate (Ce(NO3)2·6H2O) were accurately weighed and prepared into a mixed salt solution according to the molar ratio of Mn, Cu and Ce of 1.5:1.5:0.2. The mixed salt solution was used as the impregnation liquid to impregnate the dried porous recrystallized silicon carbide support in equal volume. Then, the mixture was heated at a warm temperature. The material was allowed to stand for 12 hours at 30°C and 70% relative humidity to allow nitrates to fully diffuse and adsorb within the porous recrystallized silicon carbide support. The settled material was then heated from room temperature to 110°C at a rate of 1°C / min and dried for 4 hours to slowly remove moisture and prevent rapid salt migration to the surface for crystallization. Subsequently, the material was calcined in air at a rate of 2°C / min from room temperature to 550°C for 4 hours to decompose the nitrates into the corresponding metal oxides (Mn₂O₃ / Mn₃O₄, CuO, CeO₂) and form a stable crystalline structure. These steps were repeated until the active component reached the target loading, yielding a porous recrystallized silicon carbide-based catalytic module (specifically comprising a porous recrystallized silicon carbide support and an active component supported on the support, wherein the active component is Mn₂O₃ / Mn₃O₄). 1.5 Cu 1.5 Ce 0.2 O x The active component is loaded at a rate of 10 wt% on the porous recrystallized silicon carbide support.

[0097] The performance of the porous recrystallized silicon carbide-based catalytic module prepared in Example 5 was tested, and compared with a porous recrystallized silicon carbide support (referred to as blank SiC support), a porous recrystallized silicon carbide-based catalytic module with CeO2 as the active component (referred to as CeO2 / SiC catalyst, operated according to the method of Example 5, except that manganese nitrate and copper nitrate were omitted in the impregnation solution), and a catalyst with Mn as the active component. 1.5 Cu 1.5 O x Porous recrystallized silicon carbide-based catalytic module (denoted as Mn) 1.5 Cu 1.5 O x The SiC catalyst was operated according to the method in Example 5, except that cerium nitrate was omitted from the impregnation solution. For comparison, the loading of the active component in each porous recrystallized silicon carbide-based catalytic module was 10 wt%, as detailed below:

[0098] (1) Catalytic activity: Under heating conditions, each porous recrystallized silicon carbide-based catalytic module was used to catalyze the oxidation and degradation of toluene to produce CO2 and H2O. Table 2 shows the catalytic activity (conversion rate-temperature) test results of each sample. It can be seen that the addition of Ce (Mn 1.5 Cu 1.5 Ce 0.2 O x Although it may reduce the complete conversion temperature (T) 90 The concentration of nitrous oxide (T) increased slightly, but significantly improved ignition activity (T). 50 reduce).

[0099] Table 2. Catalytic activity (conversion-temperature) test results for each sample.

[0100]

[0101] (2) Stability:

[0102] In T 90 Under temperature conditions (~300℃), an air stream containing toluene (50ppm) was continuously passed through for 100 hours. The results showed that Mn... 1.5 Cu 1.5 Ce 0.2 O x The toluene conversion rate of the SiC catalyst remained consistently at 90% ± 2%, with no significant deactivation; while the Mn catalyst... 1.5 Cu 1.5 O x The SiC catalyst was tested under the same conditions for 100 hours, and the toluene conversion rate decreased from the initial 90% to about 82%.

[0103] (3) Water resistance:

[0104] In T 90 Under temperature conditions (~300℃), an air stream containing toluene (50ppm) was continuously passed through, and 5vol% water vapor was introduced into the toluene for 100 hours. The results showed that after introducing water vapor, Mn... 1.5 Cu 1.5 Ce 0.2 O x The toluene conversion rate of the SiC catalyst only decreased slightly to 87%, and was fully recovered (toluene conversion rate was 90%) after the removal of water vapor; while the Mn catalyst... 1.5 Cu 1.5 O x When the SiC catalyst was tested under the same conditions for 100 hours, the toluene conversion rate dropped rapidly to 75% after the introduction of water vapor, and the toluene conversion rate could not be fully recovered after the water vapor was removed (the toluene conversion rate was 80.5%).

[0105] The results above show that the addition of Ce greatly improves the effect of Mn. 1.5 Cu 1.5 Ce 0.2 O x The catalyst's stability and water resistance are likely due to CeO2's excellent oxygen storage and release capabilities, which allow it to pass through Ce... 4+ / Ce 3+ The redox cycle regulates the concentration of oxygen species on the catalyst surface, promoting the deep oxidation of VOCs. Simultaneously, CeO2 effectively inhibits the sintering of active components (such as CuO) and preferentially adsorbs water vapor, protecting the Mn-Cu active sites, thereby significantly improving the catalyst's stability and resistance to poisoning.

[0106] Example 6

[0107] (1) Preparation of corrugated porous recrystallized silicon carbide support (e.g.) Figure 1 As shown): Refer to step (1) of Example 1, except that the porous recrystallized silicon carbide support in this example is a corrugated porous recrystallized silicon carbide support (average pore size is 1 μm). Specifically, follow step (1) of Example 1. After completing the second sintering and cooling to room temperature, the resulting second sintered body is a corrugated porous recrystallized silicon carbide support with an average pore size of 1 μm, a porosity of 85%, and a specific surface area of ​​53 m². 2 / g, with a three-point flexural strength of 15MPa;

[0108] (2) Loading active components: The active component raw material, dispersant and deionized water are mixed in a mass ratio of 40:2:58 to obtain a mixed liquid. The active component raw material is molybdenum dioxide powder and the dispersant is sodium polyacrylate. The mixed liquid is sprayed onto the porous recrystallized silicon carbide support, and then allowed to stand for 12 hours at a temperature of 30°C and a relative humidity of 70%. Finally, it is sintered at 700°C for 4 hours in an argon atmosphere to obtain a porous recrystallized silicon carbide-based catalytic module (specifically including a porous recrystallized silicon carbide support and an active component loaded on the porous recrystallized silicon carbide support, wherein the active component is molybdenum dioxide and the active component forms an active layer with a thickness of 0.1~10μm on the porous recrystallized silicon carbide support).

[0109] The porosity of the porous recrystallized silicon carbide-based catalytic module was determined using a mercury porosimeter. The results showed that the porosity was 80%, and the pores were mainly interconnected. The specific surface area (BET) of the porous recrystallized silicon carbide-based catalytic module was 50 m². 2 / g.

[0110] The porous recrystallized silicon carbide-based catalytic module prepared in Example 6 was used to catalyze the hydrogenation reaction of vegetable oil (specifically soybean oil) to produce vegetable butter. The reaction temperature was 300±50℃, and the hydrogen pressure was 5±1 MPa. The efficiency of vegetable butter synthesis from vegetable oil was >90%. After continuous operation at 300±50℃ for 1000 hours, the porous recrystallized silicon carbide-based catalytic module showed no significant deactivation. This indicates that the porous recrystallized silicon carbide-based catalytic module of the present invention has excellent catalytic hydrogenation effect.

[0111] Comparative Example 1

[0112] Similar to Example 6, except that the porous recrystallized silicon carbide support was replaced with a conventional silicon carbide support, ultimately yielding a conventional silicon carbide-based catalytic module. The conventional silicon carbide support was prepared by mixing silicon carbide (particle size 0.1~15 μm, with 10±1 μm particle size accounting for 50% of the total silicon carbide mass) with a binder (polyvinyl alcohol solution) at a mass ratio of 95:5, followed by kneading and aging, and then extruding using the same mold as in Example 6. A preform was formed and dried at 80°C for 24 hours. Then, it was placed in a sintering furnace and heated from room temperature to 1450°C at a rate of 5°C / min under nitrogen protection and held for 2 hours to obtain a pre-sintered porous SiC framework material. Then, following the method in Example 6, it underwent a first coating treatment and a second sintering to obtain a conventional silicon carbide support with an average pore size of 1 μm. Finally, following the method in Example 6, the active component molybdenum dioxide was loaded onto the conventional silicon carbide support to obtain a conventional silicon carbide-based catalytic module.

[0113] The porosity of the conventional silicon carbide-based catalytic module was determined using a mercury porosimeter. The results showed a porosity of 15%, with most pores being closed pores or slit pores. The specific surface area (BET) of the conventional silicon carbide-based catalytic module was 6.7 m². 2 / g, the three-point flexural strength is 18MPa.

[0114] The performance of the conventional silicon carbide-based catalytic module was tested according to the method in Example 6. The results showed that under the same reaction conditions, the catalytic efficiency was only 80%, which was significantly reduced. The catalytic efficiency began to decrease after 500 hours of operation and was 68% after 1000 hours of operation.

[0115] Comparative Example 2

[0116] Similar to Example 6, except that the porous recrystallized silicon carbide support was replaced with a conventional alumina support in a plate shape, ultimately yielding a conventional alumina-based catalytic module. The conventional alumina support was a commercially available product with a porosity of 30%, an alumina purity of 95%, an average pore size of 1 μm, and a specific surface area of ​​8.8 m². 2 / g.

[0117] The performance of the alumina-based catalytic module was tested according to the method in Example 6. The results showed that in the first stage (50-150 hours of operation), the catalytic efficiency rapidly decreased from the initial 88% to 75%, during which the reactor pressure differential began to rise slowly. In the second stage (150-200 hours of operation), the catalytic efficiency plummeted, dropping below 50% after about 180 hours of operation. At the same time, the bed pressure differential increased sharply, and the reactor outlet flow rate became unstable. Finally, at about 200 hours, the pressure safety valve alarm was triggered due to local blockage of the bed, and the experiment was forced to stop. Upon disassembling the reactor, it was found that the alumina-based catalytic module had caking on the upper part of the bed, with a large number of particles broken into fine powder, forming a viscous oil-catalyst powder mixture, indicating severe bed collapse and blockage.

[0118] The results above show that this invention uses porous recrystallized silicon carbide as a carrier, forming a framework through SiC evaporation-condensation "recrystallization." This results in a large specific surface area, excellent corrosion resistance and high-temperature resistance, as well as strong bonding with active components and strong resistance to spalling. Conventional silicon carbide carriers typically contain sintering aids (such as SiO2, Al2O3, clay, etc.) and have almost zero recrystallized SiC content, resulting in a small specific surface area. Furthermore, they contain many impurities and have poor adaptability to high-temperature, highly corrosive, and strongly acidic / alkaline environments.

[0119] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous recrystallized silicon carbide-based catalytic module, characterized in that, The porous recrystallized silicon carbide-based catalytic module comprises a support and an active component loaded on the support; the support is porous recrystallized silicon carbide with a pore size of 0.05~10 μm, a porosity of 45~85%, and a specific surface area of ​​18~80 m². 2 / g; The active component is a metal oxide active component, which is iron oxide, or molybdenum oxide, or a complex formed by zirconium oxide and cerium oxide, or a complex formed by manganese oxide, copper oxide and cerium oxide. The preparation method includes the following steps: Silicon carbide, cellulose, dextran, vegetable oil, glycerol, and water are mixed to obtain a slurry. The slurry comprises 65-70% first silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the first silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 10±1 μm accounts for more than 50% of the total mass of the first silicon carbide. The slurry is extruded to obtain a preform; The blank is dried and subjected to a first sintering to obtain a first sintered body; the temperature of the first sintering is 2440~2460℃, and the holding time is 1~3h; The first sintered body is subjected to a first coating treatment using a first coating reagent to obtain a first coated sintered body. The first coating reagent includes 65-70% second silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol, and the balance water. The particle size of the second silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 5±0.5 μm accounts for more than 50% of the total mass of the second silicon carbide. The first coated sintered body is subjected to a second sintering, and the material obtained after the second sintering is subjected to a second coating-sintering to obtain the porous recrystallized silicon carbide; the temperature of the second sintering is 2190~2210℃, and the holding time is 1~3h; the second coating-sintering includes a second coating treatment and a third sintering in sequence, the coating reagent used in the second coating treatment includes 65~70% third silicon carbide, 4~6% cellulose, 1.5~2.5% dextran, 0.5~1.5% vegetable oil, 1.5~2.5% glycerol and the balance water, the particle size of the third silicon carbide is 0.1~15μm, and the silicon carbide with a particle size of 0.6±0.1μm accounts for more than 50% of the total mass of the third silicon carbide; Using the porous recrystallized silicon carbide as a support, active components are loaded onto the support to obtain the porous recrystallized silicon carbide-based catalytic module.

2. The preparation method according to claim 1, characterized in that, The loading of the active component in the porous recrystallized silicon carbide-based catalytic module is 1~20wt%.

3. The preparation method according to claim 1, characterized in that, The active component forms an active layer on the carrier, and the thickness of the active layer is 0.1~10μm.

4. The preparation method according to claim 1, characterized in that, The porous recrystallized silicon carbide has a structure including a foam-like structure, a honeycomb structure, or a corrugated structure; the macroscopic shape of the porous recrystallized silicon carbide includes a plate-like, columnar, or tubular shape.

5. The preparation method according to claim 1, characterized in that, The second coating-sintering process further includes a third coating-sintering of the material obtained after the third sintering to obtain the porous recrystallized silicon carbide; the third coating-sintering process includes a third coating treatment and a fourth sintering in sequence, wherein the coating reagent used in the third coating treatment includes 65-70% fourth silicon carbide, 4-6% cellulose, 1.5-2.5% dextran, 0.5-1.5% vegetable oil, 1.5-2.5% glycerol and the balance water, wherein the particle size of the fourth silicon carbide is 0.1-15 μm, and the silicon carbide with a particle size of 0.5±0.07 μm accounts for more than 50% of the total mass of the fourth silicon carbide.

6. The porous recrystallized silicon carbide-based catalytic module prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the porous recrystallized silicon carbide-based catalytic module of claim 6 in wastewater catalytic ozone oxidation, catalytic hydrogenation reaction, indoor air purification, or catalytic decomposition of oil fumes.

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