Porous ceramics and preparation method and application thereof

Abstract

The present invention relates to the field of solid-gas separation, and specifically discloses a porous ceramic and a preparation method and application thereof. Wherein, the preparation method comprises: step S1. first contacting an oxide ceramic material and a diatomaceous earth composite material to obtain a first precursor; step S2. mixing the first precursor with an alkali metal silicate to obtain a second precursor; step S3. subjecting the second precursor to multi-step heat treatment, multi-step cooling and liquid immersion to obtain the porous ceramic; wherein the temperature of the liquid immersion is 45-60°C. In the porous ceramic of the present invention, the occupancy rate of large pores with an average pore size of 60-90 μm can reach 25-40%, and the occupancy rate of small pores with an average pore size of ≤25 μm can be as low as 20-25%, and the porous ceramic of the present invention has a high solid-gas separation efficiency, and the filtration rate of the porous ceramic under a pressure difference of 7 kPa on both sides can reach 16-20 L / min.

Description

Technical Field

[0001] The invention relates to the field of solid-gas separation, and in particular to a porous ceramic and a preparation method and application thereof. Background Art

[0002] Porous ceramic materials play an important role in many industries due to their unique physical and chemical properties. Specifically, these materials have shown irreplaceable application value in the fields of filtration technology, acoustic control, electrode materials, catalyst carriers, thermal insulation and biomedical materials.

[0003] The pore structure characteristics of porous ceramic materials determine their performance. The integrity of the pore structure and the pore size have an important influence on the performance of porous ceramics.

[0004] Existing porous ceramic materials for solid-gas separation are mainly sintered from silicon carbide, zirconium oxide, alumina or cordierite particles, which have the advantages of high mechanical strength and high temperature resistance. However, during the sintering process, pore shrinkage is easily produced, resulting in pore defects, which greatly reduces the gas permeation flux and poor solid-gas separation efficiency.

[0005] At the same time, in these porous ceramic materials, the occupancy rate of small pores with an average pore size of ≤25μm is relatively high, generally 40-70%; the occupancy rate of pores with an average pore size of 60-90μm is relatively low, generally 3-10%. Therefore, the small pores in these porous ceramic materials dominate, resulting in a decrease in gas permeation flux, thereby reducing the solid-gas separation efficiency.

[0006] Therefore, how to increase the pore occupancy rate of larger pore sizes in porous ceramic materials while making the pores formed in the porous ceramic materials complete, thereby improving the gas permeation flux and solid-gas separation efficiency of the porous ceramic materials, has become an urgent problem to be solved in the field of porous ceramic materials. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of high occupancy of small pores and large number of pore defects in existing porous ceramic materials, which lead to reduced gas permeation flux and decreased solid-gas separation efficiency, and to provide a porous ceramic and its preparation method and application.

[0008] In order to achieve the above object, the present invention provides a method for preparing a porous ceramic, wherein the preparation method comprises:

[0009] Step S1. bringing the oxide ceramic material and the diatomaceous earth composite material into first contact to obtain a first precursor;

[0010] Step S2. mixing the first precursor with an alkali metal silicate to obtain a second precursor;

[0011] Step S3. subjecting the second precursor to multi-step heat treatment, multi-step cooling and liquid immersion to obtain the porous ceramic;

[0012] Wherein, the temperature of the liquid immersion is 45-60°C.

[0013] The second aspect of the present invention provides a porous ceramic prepared according to the preparation method as described above, wherein, in the porous ceramic, the occupancy rate of pores with an average pore size of 60-90 μm is 25-30%, and the occupancy rate of pores with an average pore size ≤ 25 μm is 20-25% as measured by a bubble pressure method;

[0014] And / or, the filtration rate measured by the bubble pressure method at a pressure difference of 7 kPa on both sides of the porous ceramic is 16-20 L / min.

[0015] A third aspect of the present invention provides a use of the porous ceramic as described above in solid-gas separation.

[0016] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0017] The present invention makes the pores of the porous ceramics more complete and less defective by specifically selecting the type of diatomite composite material, the ratio of oxide ceramic material and diatomite composite material, the amount of alkali metal silicate, the temperature and heating rate of multi-step heat treatment, the temperature and cooling rate reached in multi-step cooling, and the temperature of liquid immersion, etc., and also improves the pore occupancy rate of larger pores in the porous ceramic material. The above two points make the porous ceramics of the present invention have high solid-gas separation efficiency. The porous ceramics of the present invention are tested by the bubble pressure method, and it is measured that the occupancy rate of large pores with an average pore size of 60-90μm can reach 25-40%, and the occupancy rate of small pores with an average pore size of ≤25μm can be as low as 20-25%. At the same time, the porous ceramics of the present invention have a stable pore structure, are not easy to shrink during multi-step heat treatment and multi-step cooling, and thus have relatively complete pores and fewer defects. The above two points make the porous ceramic of the present invention have high solid-gas separation efficiency. The filtration rate of the porous ceramic under the pressure difference of 7 kPa on both sides measured by the bubble pressure method can reach 16-20 L / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the pore size distribution of the porous ceramic A obtained in Example 1;

[0019] Figure 2 is a graph of the gas flow rate of the porous ceramic A obtained in Example 1 versus the pressure difference on both sides of the porous ceramic;

[0020] Figure 3is a schematic diagram of the pore size distribution of the porous ceramic R obtained in Comparative Example 15;

[0021] Figure 4 is a graph of the gas flow rate of the porous ceramic R obtained in Comparative Example 15 versus the pressure difference on both sides of the porous ceramic;

[0022] Figure 5 is a schematic diagram of the pore size distribution of the porous ceramic T obtained in Comparative Example 17;

[0023] Figure 6 3 is a graph showing the gas flow rate of the porous ceramic T obtained in Comparative Example 17 versus the pressure difference across the porous ceramic. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] It can be understood that the porous ceramic of the present invention is a diatomite composite material formed by melting and calcining diatomite and nano-silicon dioxide under the action of a flux sodium carbonate, and the first precursor is obtained by mixing and homogenizing with an oxide ceramic material. The above-mentioned diatomite composite material has a high porosity, which can not only improve the open porosity and the occupancy rate of large pores of the first precursor, but also stabilize the pore structure of the first precursor, which is conducive to resisting the shrinkage of the pore structure in subsequent heat treatment.

[0026] It can be understood that the first precursor and the alkali metal silicate are mixed and homogenized to form a second precursor; the second precursor undergoes multi-step heat treatment and multi-step cooling to obtain the porous ceramic of the present invention. First, the alkali metal silicate regulates the viscosity of the second precursor, which can avoid the second precursor from forming too large pores due to too low viscosity, resulting in uneven structure of the porous ceramic formed in the end, and the problem of decreased solid-gas separation efficiency. Secondly, during the multi-step heat treatment and multi-step cooling process, the pore structure of the second precursor remains stable and is not easy to shrink, so that the pore structure of the porous ceramic formed in the end is relatively complete and has fewer defects; at the same time, in the porous ceramic formed in the end, the occupancy rate of large pores with an average pore size of 60-90μm is greatly improved, and the occupancy rate of small pores with an average pore size of ≤25μm is reduced.

[0027] One aspect of the present invention provides a method for preparing a porous ceramic, wherein the preparation method comprises:

[0028] Step S1. bringing the oxide ceramic material and the diatomaceous earth composite material into first contact to obtain a first precursor;

[0029] Step S2. mixing the first precursor with an alkali metal silicate to obtain a second precursor;

[0030] Step S3. subjecting the second precursor to multi-step heat treatment, multi-step cooling and liquid immersion to obtain the porous ceramic;

[0031] Wherein, the temperature of the liquid immersion is 45-60°C.

[0032] It can be understood that the present invention is that since the pores in the porous ceramics are filled with solid sodium silicate and a small amount of sodium carbonate after heat treatment and cooling, these pores are in a closed or semi-closed state, and the sodium carbonate and sodium silicate in the porous ceramics must be cleaned out by liquid immersion to make the internal pore structure fully connected.

[0033] It is understood that the temperature of the liquid immersion must be adjusted within the range of 45-60° C. In the present invention, if the temperature of the liquid immersion is lower than 45° C., the sodium silicate and sodium carbonate remaining in the pores of the porous ceramic cannot be completely dissolved, causing some pores to remain in a closed or semi-closed state, thereby reducing the gas permeation flux of these pores, thereby reducing the solid-gas separation efficiency of the porous ceramic.

[0034] The inventors found that if the temperature of the liquid immersion is adjusted within the range of 45-60° C., the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0035] According to a preferred embodiment of the present invention, the weight ratio of the oxide ceramic material to the diatomaceous earth composite material is (0.5-2):1.

[0036] It is understood that the weight ratio of the oxide ceramic material and the diatomaceous earth composite material must be adjusted within the range of (0.5-2): 1. If the weight ratio is less than 0.5: 1 or greater than 2: 1, the pore structure of the porous ceramic formed in the end is easily shrunk during heat treatment, resulting in more pore defects and a significant decrease in solid-gas separation efficiency.

[0037] The inventors found that if the weight ratio of the oxide ceramic material and the diatomaceous earth composite material is adjusted within the range of (0.5-2):1, the pore structure of the porous ceramic finally formed is relatively complete and the solid-gas separation efficiency is relatively high.

[0038] According to a preferred embodiment of the present invention, the oxide ceramic material is zirconium oxide or aluminum oxide.

[0039] According to a preferred embodiment of the present invention, the amount of alkali metal silicate used is (4-6) wt.% of the first precursor.

[0040] It is understood that the amount of alkali metal silicate used in the present invention must be adjusted within the range of (4-6) wt.% of the first precursor. If the amount of alkali metal silicate used is less than 4 wt.% of the first precursor, the viscosity of the second precursor is too low, and too large pores are formed in the second precursor, resulting in an uneven and incomplete porous ceramic structure, which will eventually lead to a decrease in solid-gas separation efficiency; if the amount of alkali metal silicate used is greater than 6 wt.% of the first precursor, the viscosity of the second precursor is too high, which will deteriorate the processing performance of the second precursor and make the final porous ceramic difficult to form.

[0041] The inventors have found that if the amount of alkali metal silicate is adjusted within the range of (4-6) wt.% of the first precursor, the porous ceramic structure finally formed is relatively complete and the solid-gas separation efficiency is relatively high.

[0042] According to a preferred embodiment of the present invention, the alkali metal silicate includes one or more of sodium silicate, potassium silicate, sodium metasilicate and potassium metasilicate, preferably includes sodium silicate.

[0043] According to a preferred embodiment of the present invention, the preparation method of the diatomite composite material comprises: subjecting diatomite, nano-silicon dioxide and sodium carbonate to a second contact and calcination to obtain the diatomite composite material.

[0044] The obtained diatomite composite material is a calcined product and is pink. In the present invention, pink can be defined in the CIELAB color space (according to standards CIE No. 15, ISO 7724 / 1, DIN 5033 Part 7, ASTM E-1164), wherein component L is +50 to +80, component a is +10 to +80, and component b is -70 to +20.

[0045] The calcination temperature is 800-830°C.

[0046] The weight ratio of diatomaceous earth, nano-silicon dioxide and sodium carbonate may be (6-9):(10-12.5):1, for example, 7.5:10:1, 7.5:12.5:1 or 7.5:11.5:1.

[0047] It can be understood in the present invention that the calcination temperature must be adjusted within the range of 800-830°C. If the calcination temperature is lower than 800°C, diatomaceous earth and nano-silicon dioxide cannot be melted at too low a temperature to form a composite structure with high porosity, resulting in a decrease in the solid-gas separation efficiency of the porous ceramics formed in the end; if the calcination temperature is higher than 830°C, sodium carbonate as a flux will decompose rapidly, resulting in the shrinkage of the composite structure formed by diatomaceous earth and nano-silicon dioxide, a sharp decrease in porosity, and only small pores with an average pore size of 28-52nm exist in the diatomaceous earth composite material, which ultimately results in a decrease in the solid-gas separation efficiency of the porous ceramics.

[0048] The inventors have found that if the calcination temperature is adjusted within the range of 800-830° C., the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0049] It can be understood in the present invention that the weight ratio of diatomaceous earth and sodium carbonate must be adjusted within the range of (6-9):1. If the weight ratio of diatomaceous earth and sodium carbonate is lower than 6:1, the porosity of the composite structure formed by diatomaceous earth and nano-silica will be reduced, and the occupancy rate of pores with an average pore size of 60-90 μm will be reduced, thereby reducing the solid-gas separation efficiency of the final porous ceramic.

[0050] The inventors found that when the weight ratio of diatomaceous earth to sodium carbonate is adjusted within the range of (6-9):1, the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0051] It can be understood in the present invention that the weight ratio of nano-silicon dioxide and sodium carbonate must be adjusted within the range of (10-12.5):1. If the weight ratio of nano-silicon dioxide and sodium carbonate is lower than 10:1, the occupancy rate of small pores with an average pore size of ≤25 μm in the final porous ceramic will increase significantly, thereby reducing the solid-gas separation efficiency of the final porous ceramic.

[0052] The inventors found that when the weight ratio of nano-silicon dioxide to sodium carbonate is adjusted in the range of (10-12.5):1, the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0053] According to a preferred embodiment of the present invention, step S1 further comprises performing a first homogenization after the first contact.

[0054] The first homogenization may be a conventional homogenization method in the art, such as resonance homogenization, mechanical stirring homogenization or air flow homogenization.

[0055] The first homogenization temperature is 150-180°C, for example, 150°C, 165°C or 180°C.

[0056] It can be understood in the present invention that the temperature of the first homogenization needs to be adjusted within the range of 150-180° C. If the temperature of the first homogenization is less than 150° C., the residual water in the first precursor cannot be completely evaporated and removed, causing the sodium silicate in the second precursor to hydrolyze, resulting in the deterioration of the dispersion of the particles in the second precursor, and some particles agglomerating, resulting in a part of the dense structure of the porous ceramics finally formed, which will eventually lead to a decrease in the solid-gas separation efficiency.

[0057] The inventors have found that if the temperature of the first homogenization is adjusted within the range of 150-180° C., the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0058] It is understood that the pH value of the second precursor must be ≥ 8. If the pH value of the second precursor is < 8, the dispersibility of the particles in the second precursor deteriorates, and some particles agglomerate, resulting in a partially dense structure in the porous ceramic formed, which ultimately leads to a decrease in solid-gas separation efficiency.

[0059] The inventors have found that if the pH value of the second precursor is ≥8, the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0060] According to a preferred embodiment of the present invention, step S2 further comprises performing a second homogenization after the mixing.

[0061] The second homogenization may be a conventional homogenization method in the art, such as resonance homogenization, mechanical stirring homogenization or air flow homogenization.

[0062] According to a preferred embodiment of the present invention, the second precursor is further shaped before the multi-step heat treatment.

[0063] The shaping may be conventional in the art, such as mold shaping or 3D printing shaping.

[0064] According to a preferred embodiment of the present invention, the 3D printing finalization includes:

[0065] Preparing for printing. Performing 3D printing. Preferably, preparing for printing includes: establishing a model of the appearance and internal structure of the porous ceramic, simulating and verifying the model; exporting and loading the model into the 3D printer software, and setting printing parameters; delivering the second precursor to the printing nozzle through the printer barrel.

[0066] Preferably, the 3D printing also includes curing the second precursor.

[0067] The curing method may be microwave heating or circulating hot air heating.

[0068] According to a preferred embodiment of the present invention, the multi-step heat treatment includes a first heat treatment, a second heat treatment, a third heat treatment and a fourth heat treatment.

[0069] Among them, the temperature of the first heat treatment is 100-145°C, such as 120°C, 130°C or 140°C; the heating rate is 6-8°C / min, such as 5°C, 6°C, 7°C or 8°C; the insulation time is 0.4-0.6h, such as 0.4h, 0.5h or 0.6h.

[0070] Among them, the temperature of the second heat treatment is 410-630℃, for example, 410℃, 520℃ or 600℃; the heating rate is 2-8℃ / min, for example, 2℃, 3℃, 4℃, 5℃, 6℃, 7℃ or 8℃; the holding time is 0.7-1h, for example, 0.7h, 0.8h or 1h.

[0071] Among them, the temperature of the third heat treatment is 660-980°C, for example, 660°C, 820°C or 900°C; the heating rate is 5-10°C / min, for example, 5°C, 6°C, 7°C, 8°C, 9°C or 10°C; the holding time is 0.1-0.2h, for example, 0.1h, 0.15h or 0.2h.

[0072] Among them, the temperature of the fourth heat treatment is 1100-1150°C, for example, 1100°C, 1120°C or 1150°C; the heating rate is 3-10°C / min, for example, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C or 10°C; the holding time is 4.8-7.2h, for example, 4.8h, 6.5h or 7.2h.

[0073] It is understood that the temperature of the second heat treatment must be adjusted within the range of 410-630° C. If the temperature of the second heat treatment is higher than 630° C. or lower than 410° C., the oxide ceramic material cannot undergo a crystal transformation, resulting in the crystal form of the original oxide ceramic material that has not undergone a crystal transformation in the subsequent third heat treatment being unable to form a high-porosity eutectic structure with the diatomaceous earth composite material, resulting in a decrease in the solid-gas separation efficiency of the porous ceramic finally formed.

[0074] The inventors have found that if the temperature of the second heat treatment is adjusted within the range of 410-630° C., the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0075] It can be understood in the present invention that the temperature of the third heat treatment must be adjusted within the range of 660-980° C. If the temperature of the third heat treatment is higher than 980° C. or lower than 660° C., the oxide ceramic material cannot reach the specific temperature at which a high-porosity eutectic structure is formed with the diatomite composite material; at the same time, the morphology and distribution of the pores inside the second precursor cannot be effectively regulated, and the internal pores cannot be made uniform and regular, resulting in a decrease in the solid-gas separation efficiency of the porous ceramic finally formed.

[0076] The inventors found that if the temperature of the third heat treatment is adjusted within the range of 660-980° C., the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0077] It can be understood in the present invention that the heating rate of the third heat treatment must be adjusted to 5-10°C / minute. If the heating rate of the third heat treatment is higher than 10°C / minute, it will cause uneven temperature distribution in different areas inside the second precursor, resulting in different expansion rates in different areas inside the second precursor, thereby inducing thermal stress and causing cracks, warping or cracking inside the porous ceramic finally formed; in addition, it will also cause the pores in certain areas inside the second precursor to expand rapidly, while the pores in other areas may not react in time, which will lead to uneven pore morphology, and the occupancy rate of pores with an average pore size of 60-90μm will decrease, and the occupancy rate of pores with an average pore size of ≤25μm will increase significantly, resulting in a decrease in the solid-gas separation efficiency of the final porous ceramic product.

[0078] The inventors have found that if the heating rate of the third heat treatment is adjusted within 5-10° C. / min, the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0079] It is understood that the temperature of the fourth heat treatment must be adjusted within the range of 1100-1150° C. If the temperature of the fourth heat treatment is lower than 1100° C., the sodium silicate in the second precursor cannot be melted to form a liquid phase, so that the particles in the second precursor cannot be rearranged to form pores with uniform pore sizes due to the formation of liquid sodium silicate, and the liquid sodium silicate cannot be filled into the pores formed above, which results in that the pores inside the finally formed porous ceramic cannot be evenly distributed, and the pores are spaced relatively large from each other, and the solid-gas separation efficiency is reduced.

[0080] The inventors have found that if the temperature of the fourth heat treatment is adjusted within the range of 1100-1150° C., the solid-gas separation efficiency of the porous ceramic finally formed is higher.

[0081] According to a preferred embodiment of the present invention, the multi-step cooling includes a first cooling, a second cooling, a third cooling and a fourth cooling.

[0082] The temperature reached by the first cooling is 640-960°C, such as 640°C, 800°C or 960°C; the cooling rate is 4-6°C / min, such as 4°C, 5°C or 6°C; the insulation time is 0.1-0.2h, such as 0.1h, 0.15h or 0.2h.

[0083] The temperature reached by the second cooling is 400-600°C, such as 400°C, 500°C or 600°C; the cooling rate is 3-6°C / min, such as 3°C, 4°C, 5°C or 6°C; the holding time is 0.2-0.4h, such as 0.2h, 0.3h or 0.4h.

[0084] Wherein, the temperature reached by the third cooling is 175-270°C, such as 175°C, 220°C or 270°C; the cooling rate is 2-5°C / min, such as 2°C, 3°C, 4°C or 5°C; the insulation time is 0.05-0.1h, such as 0.05h, 0.07h or 0.1h.

[0085] Wherein, the temperature reached by the fourth cooling is 70-110°C, such as 70°C, 90°C or 110°C; the cooling rate is 5-10°C / min, such as 5°C, 6°C, 7°C, 8°C, 9°C or 10°C.

[0086] It can be understood in the present invention that, due to the different specific gravities of different crystal forms in the eutectic structure, the arrangement of particles inside the eutectic structure is different, so the crystal form transition is accompanied by volume change and affects the pore size distribution of the pores inside the second precursor. Therefore, the temperature reached by the first cooling must be adjusted within the range of 640-960°C. If the temperature reached by the first cooling is lower than 640°C, the eutectic structure formed in the third heat treatment will be unstable, and thus the crystal form transition will occur, making the pore size distribution of the pores inside the second precursor uneven, and the occupancy rate of small pores with an average pore size of ≤25μm will increase sharply, thereby reducing the solid-gas separation efficiency.

[0087] The inventors found that if the temperature reached by the first cooling is adjusted within the range of 640-960° C., the eutectic structure formed in the third heat treatment is relatively stable, and the solid-gas separation efficiency of the porous ceramic finally formed is relatively high.

[0088] It can be understood in the present invention that the cooling rate of the first cooling must be adjusted to 4-6°C / minute. If the cooling rate of the first cooling is higher than 6°C / minute, it will cause the temperature difference inside and outside the second precursor to be too large, resulting in different shrinkage rates of different regions inside and outside the second precursor. Some regions shrink too fast, which will produce greater thermal stress and cause cracks inside or on the surface of the ceramic body. In addition, if the cooling rate of the first cooling is higher than 6°C / minute, the pores in different parts of the ceramic will shrink at different rates, resulting in uneven pore distribution and the generation of pore defects, causing the occupancy rate of small pores with an average pore size of ≤25μm to increase significantly, resulting in a decrease in the solid-gas separation efficiency of the final porous ceramic product.

[0089] It is understood that the temperature reached by the second cooling must be adjusted within the range of 400-600° C. If the temperature reached by the second cooling is higher than 600° C., the liquid phase sodium silicate produced in the fourth heat treatment cannot solidify into a solid in the pores, and thus the pore structure cannot be stabilized, which will cause the pore size difference of different parts in a single pore in the finally formed porous ceramic to become larger, thereby reducing the gas permeation flux of a single pore, thereby reducing the solid-gas separation efficiency.

[0090] The inventors found that if the temperature reached by the second cooling is adjusted within the range of 400-600°C, the pore sizes of different parts of a single pore in the finally formed porous ceramic will have a smaller difference, and the solid-gas separation efficiency of the porous ceramic will be higher.

[0091] In the present invention, the above-mentioned multi-step heat treatment and multi-step cooling can be a heat treatment system as a whole, specifically: the second precursor is heated from room temperature (which can be 25-40°C) to the first heat treatment temperature (100-145°C), and kept warm for 0.4-0.6h; then heated to the second heat treatment temperature (410-630°C), and kept warm for 0.7-1h; then heated to the third heat treatment temperature (660-980°C), and kept warm for 0.1-0.2h; then heated to the fourth heat treatment temperature Temperature (1100-1150℃), and keep it warm for 4.8-7.2h; after the insulation time is over, drop from the fourth heat treatment temperature to the temperature reached by the first cooling (640-960℃), and keep it warm for 0.1-0.2h; then drop to the temperature reached by the second cooling (400-600℃), and keep it warm for 0.2-0.4h; then drop to the temperature reached by the third cooling (175-270℃), and keep it warm for 0.05-0.1h; finally drop to the temperature reached by the fourth cooling (70-110℃).

[0092] According to a preferred embodiment of the present invention, step S3 further comprises drying after soaking in the liquid.

[0093] The drying may be conventional in the art, such as hot air drying or microwave drying.

[0094] According to a preferred embodiment of the present invention, the temperature of the liquid immersion may be 45°C, 55°C or 60°C.

[0095] According to a preferred embodiment of the present invention, the liquid immersion time may be 24-48 hours, such as 24 hours, 48 ​​hours or 36 hours.

[0096] According to a preferred embodiment of the present invention, the liquid immersion may be immersion in water.

[0097] The second aspect of the present invention provides a porous ceramic prepared according to the preparation method as described above, wherein, in the porous ceramic, the occupancy rate of pores with an average pore size of 60-90 μm is 25-30%, and the occupancy rate of pores with an average pore size ≤ 25 μm is 20-25% as measured by a bubble pressure method;

[0098] And / or, the filtration rate measured by the bubble pressure method at a pressure difference of 7 kPa on both sides of the porous ceramic is 16-20 L / min.

[0099] A third aspect of the present invention provides a use of the porous ceramic as described above in solid-gas separation.

[0100] According to a particularly preferred embodiment of the present invention, the method for preparing the porous ceramic comprises:

[0101] Step S1. bringing the oxide ceramic material and the diatomaceous earth composite material into first contact to obtain a first precursor;

[0102] Step S2. mixing the first precursor with an alkali metal silicate to obtain a second precursor;

[0103] Step S3. subjecting the second precursor to multi-step heat treatment, multi-step cooling, and liquid immersion to obtain a porous ceramic;

[0104] The preparation method of the diatomite composite material comprises: performing a second contact and calcining on diatomite, nano-silicon dioxide and sodium carbonate until the calcined product is pink, thereby obtaining the diatomite composite material;

[0105] Wherein, the calcination temperature is 830°C;

[0106] Wherein, the weight ratio of the oxide ceramic material to the diatomaceous earth composite material is 1.2:1;

[0107] Wherein, the amount of the alkali metal silicate is 4.2wt.% of the first precursor;

[0108] Wherein, the temperature of the first homogenization is 150°C;

[0109] Wherein, the pH of the second precursor is 8.5;

[0110] The multi-step heat treatment includes a first heat treatment, a second heat treatment, a third heat treatment and a fourth heat treatment.

[0111] The temperature of the first heat treatment is 105°C, the heating rate is 7°C / min, and the holding time is 0.4h; the temperature of the second heat treatment is 520°C, the heating rate is 5°C / min, and the holding time is 0.8h; the temperature of the third heat treatment is 820°C, the heating rate is 10°C / min, and the holding time is 0.1h; the temperature of the fourth heat treatment is 1100°C, the heating rate is 7.5°C / min, and the holding time is 6h;

[0112] The multi-step cooling includes the first cooling, the second cooling, the third cooling and the fourth cooling.

[0113] The temperature reached by the first cooling is 800°C, the cooling rate is 4°C / min, and the holding time is 0.1h; the temperature reached by the second cooling is 500°C, the cooling rate is 4.5°C / min, and the holding time is 0.2h; the temperature reached by the third cooling is 220°C, the cooling rate is 3.5°C / min, and the holding time is 0.05h; the temperature reached by the fourth cooling is 90°C, and the cooling rate is 10°C / min;

[0114] Wherein, the temperature of the liquid immersion is 55°C.

[0115] The present invention will be described in detail below through examples and comparative examples.

[0116] In the following examples and comparative examples, the pore occupancy of the porous ceramic and its gas flow rate (ie, filtration rate) at a pressure of 7 kPa are specifically measured by the following method:

[0117] 1. Test instrument: Bubble pressure membrane pore size analyzer produced by Best Instrument Technology (Beijing) Co., Ltd., model: BSD-PB.

[0118] 2. Test method: The bubble pressure method is used for testing, specifically, a pressure difference is applied to both sides of the porous ceramic to overcome the surface tension of the infiltration liquid in the membrane pores and drive the infiltration liquid through the pores, thereby obtaining the pore size data and gas flow rate data of the porous ceramic, including the occupancy rate of pores with different pore sizes and the flow rate curves of gas passing through the porous ceramic under different pressure differences, including dry curves, wet curves and semi-dry curves.

[0119] Among them, the dry curve is defined as the gas pressure-flow rate relationship curve obtained by porous ceramics in a dry state;

[0120] The wet curve is defined as the gas pressure-flow rate relationship curve obtained when the pores of the porous ceramic are infiltrated with the infiltration liquid;

[0121] The semi-dry curve is defined as plotting half of the flow rate value of the dry curve against the gas pressure, that is, the semi-dry curve is obtained.

[0122] 3. Principle of the bubble pressure method: Taking a certain membrane material as an example, the membrane is fully wetted with a liquid that can be infiltrated with it. Due to the existence of surface tension, the infiltrating liquid will be bound in the pores of the membrane; a gradually increasing gas pressure is applied to one side of the membrane. When the gas pressure reaches a pressure greater than the pressure generated by the surface tension of the infiltrating liquid in a certain pore, the infiltrating liquid in the pore will be pushed out by the gas; since the smaller the pore size, the higher the pressure generated by the surface tension, the higher the gas pressure required to push out the infiltrating liquid; similarly, it can be seen that the infiltrating liquid in the pore with the largest pore size will be pushed out first, allowing the gas to pass through the pore, and then as the pressure increases, the pore size decreases from large to small, and the infiltrating liquid in the pore is pushed out in turn, allowing the gas to pass through, until all the pores are opened, reaching the same gas flow rate as the membrane in the dry state.

[0123] 4. The pore size determination formula of porous ceramics: D = 4γCosθ / p,

[0124] Wherein, D is the pore diameter; γ is the surface tension of the infiltration liquid; θ is the contact angle between the infiltration liquid and the pore surface of the porous ceramic; and p is the pressure difference on both sides of the porous ceramic.

[0125] The following are the sources of raw materials in the embodiments and comparative examples:

[0126] Alumina ceramic powder is a commercial product of Hebei Xieyao Metal Co., Ltd. with a brand number of 1344-28 and a specification of 200 mesh;

[0127] Zirconia ceramic powder is a commercial product of Qinghe County Huichu Welding Materials Co., Ltd. with the brand name Huichu 456271, specification: 200 mesh;

[0128] Diatomaceous earth is a commercial product of Gongyi Haoxin Water Purification Material Co., Ltd., specification: 325 mesh;

[0129] The calcined diatomite is a commercial product of Shijiazhuang Yunshi New Building Materials Co., Ltd. with the brand name of gzt 325 and the specification of 325 mesh;

[0130] Nano-silicon dioxide is a commercial product of Henan Haiborui Silicon Material Technology Co., Ltd. with the brand name NPS-L;

[0131] Sodium carbonate was a commercial product of Tianjin Zhiyuan Chemical Reagent Co., Ltd.

[0132] Sodium silicate is a commercial product of Tianjin Zhiyuan Chemical Reagent Co., Ltd.

[0133] Preparation Example 1

[0134] Preparation of diatomite composite material: 90g diatomite, 138g nano-silicon dioxide and 12g sodium carbonate were mixed evenly and calcined at 830°C. The calcined product was pink, and the diatomite composite material was obtained. SEM image analysis showed that the porosity of the diatomite composite material was high, among which the pores with an average pore size of 60-90μm had a high occupancy rate.

[0135] Preparation of Control Example 1

[0136] The method of Preparation Example 1 was followed, except that the calcination temperature was 700° C. The obtained diatomite composite material was light yellow. SEM image analysis showed that there were almost no pores in the diatomite composite material.

[0137] Preparation of Control Example 2

[0138] The method of Preparation Example 1 was followed, except that the calcination temperature was 860° C. The obtained diatomite composite material was light gray. SEM image analysis showed that the porosity of the diatomite composite material was low, and only small pores with an average pore size of 28-52 nm existed in the diatomite composite material.

[0139] Preparation of Control Example 3

[0140] The method of Preparation Example 1 was followed, except that the amount of diatomaceous earth used was 48 g, and the weight ratio of diatomaceous earth, nano-silicon dioxide and sodium carbonate was 4:11.5:1. The obtained diatomaceous earth composite material was pink, wherein the porosity of the diatomaceous earth composite material was low, and the occupancy rate of pores with an average pore size of 60-90 μm was low.

[0141] Preparation of Control Example 4

[0142] The method of Preparation Example 1 is followed, except that the amount of nano-silicon dioxide used is 96 g, and the weight ratio of diatomaceous earth, nano-silicon dioxide and sodium carbonate is 7.5:8:1. The obtained diatomaceous earth composite material is pink, wherein the porosity of the diatomaceous earth composite material is low, the occupancy rate of pores with an average pore diameter of 60-90 μm is low, and the occupancy rate of small pores with an average pore diameter ≤25 μm is high.

[0143] Example 1

[0144] 55g of alumina ceramic powder and 45g of diatomaceous earth composite material in the above-mentioned Preparation Example 1 were mixed uniformly at 150°C to obtain a first precursor. 50g of the first precursor was mixed uniformly with 2.1g of sodium silicate to obtain a second precursor, and the pH value of the second precursor was 8.5. After the second precursor was finalized by 3D printing, multi-step heat treatment and multi-step cooling were performed.

[0145] In the multi-step heat treatment, the second precursor is heated from 25°C to the first heat treatment temperature of 105°C, with a heating rate of 7°C / min, and kept warm for 0.4h; then heated to the second heat treatment temperature of 520°C, with a heating rate of 5°C / min, and kept warm for 0.8h; then heated to the third heat treatment temperature of 820°C, with a heating rate of 10°C / min, and kept warm for 0.1h; then heated to the fourth heat treatment temperature of 1100°C, with a heating rate of 7.5°C / min, and kept warm for 6h.

[0146] In the multi-step cooling process, the second precursor was cooled from 1100°C to the temperature of 800°C reached by the first cooling process, with a cooling rate of 4°C / min, and kept warm for 0.1h; then cooled from 800°C to the temperature of 500°C reached by the second cooling process, with a cooling rate of 4.5°C / min, and kept warm for 0.2h; then cooled from 500°C to the temperature of 220°C reached by the third cooling process, with a cooling rate of 3.5°C / min, and kept warm for 0.05h; then cooled from 220°C to the temperature of 90°C reached by the fourth cooling process, with a cooling rate of 10°C / min.

[0147] Afterwards, the second precursor obtained through the above process was immersed in water at 55° C. and taken out after 24 hours to obtain porous ceramic A.

[0148] Depend on Figure 1 It can be seen that in porous ceramic A, the pore occupancy rate of pores with an average pore size of 60-90 μm measured by the bubble pressure method is 28.1%, and the pore occupancy rate of pores with an average pore size ≤ 25 μm is 24.4%; Figure 2 It can be seen that the filtration rate of porous ceramic A measured by the bubble pressure method when the pressure difference on both sides is 7 kPa is 18.3 L / min.

[0149] Example 2

[0150] 55g of zirconium oxide ceramic powder and 27.5g of diatomaceous earth composite material in the above-mentioned Preparation Example 1 were mixed uniformly at 180°C to obtain a first precursor. 50g of the first precursor was mixed uniformly with 3g of sodium silicate to obtain a second precursor, and the pH value of the second precursor was 8.2. After the second precursor was finalized by 3D printing, multi-step heat treatment and multi-step cooling were performed.

[0151] In the multi-step heat treatment, the second precursor is heated from 25°C to the temperature of 140°C for the first heat treatment, with a heating rate of 6°C / min, and kept warm for 0.6h; then heated to the temperature of 600°C for the second heat treatment, with a heating rate of 8°C / min, and kept warm for 1h; then heated to the temperature of 660°C for the third heat treatment, with a heating rate of 7.5°C / min, and kept warm for 0.2h; then heated to the temperature of 1120°C for the fourth heat treatment, with a heating rate of 3°C / min, and kept warm for 7.2h.

[0152] In the multi-step cooling process, the second precursor was cooled from 1120°C to 640°C, the temperature reached by the first cooling, at a cooling rate of 5°C / min, and kept warm for 0.2h; then cooled from 640°C to 600°C, the temperature reached by the second cooling, at a cooling rate of 6°C / min, and kept warm for 0.4h; then cooled from 600°C to 175°C, the temperature reached by the third cooling, at a cooling rate of 2°C / min, and kept warm for 0.1h; then cooled from 175°C to 110°C, the temperature reached by the fourth cooling, at a cooling rate of 8°C / min.

[0153] Afterwards, the second precursor obtained through the above process was immersed in water at 45° C. and taken out after 48 hours to obtain porous ceramic B.

[0154] In porous ceramic B, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 25.7%, and the occupancy rate of pores with an average pore size ≤25μm to be 24.6%; the bubble pressure method was used to measure the filtration rate of porous ceramic B at a pressure difference of 7kPa on both sides to be 16.2L / min.

[0155] Example 3

[0156] 22.5 g of alumina ceramic powder was mixed with 45 g of the diatomite composite material in the above-mentioned Preparation Example 1, and a first homogenization was performed at 165° C. to obtain a first precursor. 50 g of the first precursor was mixed with 2.5 g of sodium silicate, and a second homogenization was performed to obtain a second precursor, and the pH value of the second precursor was 8.0. After the second precursor was finalized by 3D printing, a multi-step heat treatment and a multi-step cooling were performed.

[0157] In the multi-step heat treatment, the second precursor is heated from 25°C to the temperature of 130°C for the first heat treatment, with a heating rate of 8°C / min, and kept warm for 0.5h; then heated to the temperature of 410°C for the second heat treatment, with a heating rate of 2°C / min, and kept warm for 0.7h; then heated to the temperature of 900°C for the third heat treatment, with a heating rate of 5°C / min, and kept warm for 0.15h; then heated to the temperature of 1150°C for the fourth heat treatment, with a heating rate of 10°C / min, and kept warm for 6.5h.

[0158] In the multi-step cooling process, the second precursor was cooled from 1150°C to 960°C, the temperature reached by the first cooling, at a cooling rate of 6°C / min, and kept at this temperature for 0.15h; then cooled from 960°C to 400°C, the temperature reached by the second cooling, at a cooling rate of 3.5°C / min, and kept at this temperature for 0.3h; then cooled from 400°C to 270°C, the temperature reached by the third cooling, at a cooling rate of 5°C / min, and kept at this temperature for 0.07h; then cooled from 270°C to 70°C, the temperature reached by the fourth cooling, at a cooling rate of 5.5°C / min.

[0159] Afterwards, the second precursor obtained through the above process was immersed in water at 60° C. and taken out after 36 hours to obtain porous ceramic C.

[0160] In porous ceramic C, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 26.1%, and the occupancy rate of pores with an average pore size ≤25μm to be 23.7%; the bubble pressure method was used to measure the filtration rate of porous ceramic C at a pressure difference of 7kPa on both sides to be 17.1L / min.

[0161] Comparative Example 1

[0162] The porous ceramic D was obtained by following the method of Example 1 except that the weight ratio of the oxide ceramic material to the diatomaceous earth composite material was 3:1.

[0163] In porous ceramic D, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 6.2%, and the occupancy rate of pores with an average pore size ≤25μm to be 65.4%. The bubble pressure method was used to measure the filtration rate of porous ceramic B at a pressure difference of 7kPa on both sides to be 5.3L / min.

[0164] Comparative Example 2

[0165] The porous ceramic E was obtained by following the method of Example 1, except that the amount of sodium silicate used was 1 g.

[0166] In porous ceramic E, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 8.6%, and the occupancy rate of pores with an average pore size ≤25μm to be 53.7%; the bubble pressure method was used to measure the filtration rate of porous ceramic B at a pressure difference of 7kPa on both sides to be 7.2L / min.

[0167] Comparative Example 3

[0168] The porous ceramic F was obtained by following the method of Example 1, except that the amount of sodium silicate used was 7 g.

[0169] In porous ceramic F, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90 μm to be 17.1%, and the occupancy rate of pores with an average pore size ≤ 25 μm to be 40.5%; the bubble pressure method was used to measure the filtration rate of porous ceramic F at a pressure difference of 7 kPa on both sides to be 11.7 L / min.

[0170] Comparative Example 4

[0171] According to the preparation methods of Comparative Example 1 and Example 2, porous ceramic G was obtained.

[0172] In porous ceramic G, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 7.4%, and the occupancy rate of pores with an average pore size ≤25μm to be 59.7%; the bubble pressure method was used to measure the filtration rate of porous ceramic G at a pressure difference of 7kPa on both sides to be 7.2L / min.

[0173] Comparative Example 5

[0174] According to the preparation methods of Comparative Example 2 and Example 2, porous ceramic H was obtained.

[0175] In porous ceramic H, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90 μm to be 3.6%, and the occupancy rate of pores with an average pore size ≤ 25 μm to be 68.9%; the bubble pressure method was used to measure the filtration rate of porous ceramic H at a pressure difference of 7 kPa on both sides to be 4.1 L / min.

[0176] Comparative Example 6

[0177] The method of Example 2 is followed, except that the temperature of the first homogenization is 90° C., to obtain porous ceramic I.

[0178] In porous ceramic I, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90 μm to be 16.7%, and the occupancy rate of pores with an average pore size ≤ 25 μm to be 51.5%; the bubble pressure method was used to measure the filtration rate of porous ceramic I at a pressure difference of 7 kPa on both sides to be 9.4 L / min.

[0179] Comparative Example 7

[0180] The method of Example 2 is followed, except that the pH value of the second precursor is 6, to obtain porous ceramic J.

[0181] In porous ceramic J, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 18.3%, and the occupancy rate of pores with an average pore size ≤25μm to be 49.3%; the bubble pressure method was used to measure the filtration rate of porous ceramic J at a pressure difference of 7kPa on both sides of the porous ceramic to be 10.8L / min.

[0182] Comparative Example 8

[0183] The method of Example 2 is followed, except that the temperature of the second heat treatment is 300° C., to obtain porous ceramic K.

[0184] In porous ceramic K, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 14.9%, and the occupancy rate of pores with an average pore size ≤25μm to be 57.1%; the bubble pressure method was used to measure the filtration rate of porous ceramic K at a pressure difference of 7kPa on both sides of the porous ceramic K to be 9.6L / min.

[0185] Comparative Example 9

[0186] The method of Example 2 is followed, except that the temperature of the second heat treatment is 650° C., to obtain porous ceramic L.

[0187] In porous ceramic L, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 13.7%, and the occupancy rate of pores with an average pore size ≤25μm to be 59.4%; the bubble pressure method was used to measure the filtration rate of porous ceramic L at a pressure difference of 7kPa on both sides to be 9.0L / min.

[0188] Comparative Example 10

[0189] The method of Example 2 is followed, except that the temperature of the third heat treatment is 500° C., to obtain porous ceramics M.

[0190] In porous ceramic M, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 6.5%, and the occupancy rate of pores with an average pore size ≤25μm to be 64.7%; the bubble pressure method was used to measure the filtration rate of porous ceramic M at a pressure difference of 7kPa on both sides to be 5.4L / min.

[0191] Comparative Example 11

[0192] The method of Example 2 is followed, except that the temperature of the third heat treatment is 1050° C., to obtain porous ceramic N.

[0193] In porous ceramic N, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 5.3%, and the occupancy rate of pores with an average pore size ≤25μm to be 67.2%; the bubble pressure method was used to measure the filtration rate of porous ceramic N at a pressure difference of 7kPa on both sides to be 4.1L / min.

[0194] Comparative Example 12

[0195] The method of Example 2 is followed, except that the temperature of the fourth heat treatment is 1050° C., to obtain porous ceramic O.

[0196] In porous ceramic O, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 4.3%, and the occupancy rate of pores with an average pore size ≤25μm to be 37.5%; the bubble pressure method was used to measure the filtration rate of porous ceramic O at a pressure difference of 7kPa on both sides of the porous ceramic O to be 5.6L / min.

[0197] Comparative Example 13

[0198] The method of Example 2 is followed, except that the temperature reached by the first cooling is 500° C., to obtain porous ceramic P.

[0199] In the porous ceramic P, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 18.4%, and the occupancy rate of pores with an average pore size ≤25μm to be 67.2%; the bubble pressure method was used to measure the filtration rate of the porous ceramic P at a pressure difference of 7kPa on both sides to be 8.5L / min.

[0200] Comparative Example 14

[0201] The method of Example 2 is followed, except that the temperature reached by the second cooling is 700° C., to obtain porous ceramic Q.

[0202] In the porous ceramic Q, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 20.9%, and the occupancy rate of pores with an average pore size ≤25μm to be 35.7%; the bubble pressure method was used to measure the filtration rate of the porous ceramic Q at a pressure difference of 7kPa on both sides to be 13.4L / min.

[0203] Comparative Example 15

[0204] The porous ceramic R was obtained by following the method of Example 2 except that the temperature of the water was 25° C. during the soaking process.

[0205] like Figure 3 As shown in FIG. 1 , in porous ceramic R, the pore occupancy rate of pores with an average pore size of 60-90 μm measured by the bubble pressure method is 0%, and the pore occupancy rate of pores with an average pore size ≤ 25 μm is 24.2%; Figure 4 As shown, the filtration rate of the porous ceramic R measured by the bubble pressure method when the pressure difference on both sides was 7 kPa was 8.3 L / min.

[0206] Comparative Example 16

[0207] The porous ceramic S was obtained by following the method of Example 2, except that the diatomite composite material was replaced with commercially available calcined diatomite.

[0208] In porous ceramic S, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 4.1%, and the occupancy rate of pores with an average pore size ≤25μm to be 68.5%; the bubble pressure method was used to measure the filtration rate of porous ceramic S at a pressure difference of 7kPa on both sides to be 2.9L / min.

[0209] Comparative Example 17

[0210] The method of Example 2 is followed, except that after the multi-step cooling, the second precursor is not soaked in water to obtain the porous ceramic T.

[0211] Depend on Figure 5It can be seen that in porous ceramic T, the pore occupancy rate of pores with an average pore size of 60-90 μm measured by the bubble pressure method is 0%, and the pore occupancy rate of pores with an average pore size ≤ 25 μm is 27.4%; Figure 6 It can be seen that the filtration rate of the porous ceramic T measured by the bubble pressure method when the pressure difference on both sides is 7 kPa is 7.6 L / min.

[0212] Comparative Example 18

[0213] The method of Example 2 is followed, except that the heat treatment is a single-step heat treatment, the temperature is 1150° C., and the holding time is 6 hours, to obtain porous ceramic U.

[0214] In the porous ceramic U, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 7.3%, and the occupancy rate of pores with an average pore size ≤25μm to be 53.6%; the bubble pressure method was used to measure the filtration rate of the porous ceramic U at a pressure difference of 7kPa on both sides to be 7.8L / min.

[0215] Comparative Example 19

[0216] The method of Example 2 is followed, except that the cooling step is a single-step cooling step at a temperature of 90° C., to obtain porous ceramic V.

[0217] In porous ceramic V, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 2.5%, and the occupancy rate of pores with an average pore size ≤25μm to be 66.1%; the bubble pressure method was used to measure the filtration rate of porous ceramic V at a pressure difference of 7kPa on both sides to be 2.3L / min.

[0218] Comparative Example 20

[0219] The porous ceramic W is obtained by the method of Example 2, except that the diatomaceous earth composite material is the diatomaceous earth composite material prepared in Comparative Example 3.

[0220] In porous ceramic W, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 12.8%, and the occupancy rate of pores with an average pore size ≤25μm to be 35.9%; the bubble pressure method was used to measure the filtration rate of porous ceramic W at a pressure difference of 7kPa on both sides to be 11.4L / min.

[0221] Comparative Example 21

[0222] The porous ceramic X is obtained by following the method of Example 2, except that the diatomaceous earth composite material is the diatomaceous earth composite material prepared in Comparative Example 4.

[0223] In the porous ceramic X, the occupancy rate of pores with an average pore size of 60-90 μm was measured by the bubble pressure method to be 11.2%, and the occupancy rate of pores with an average pore size ≤ 25 μm was 65.5%; the filtration rate of the porous ceramic X was measured by the bubble pressure method at a pressure difference of 7 kPa on both sides thereof to be 6.8 L / min.

[0224] Comparative Example 22

[0225] The method of Example 2 was followed, except that the heating rate of the third heat treatment was set to 13° C. / min, to obtain porous ceramic Y.

[0226] In porous ceramic Y, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 13.9%, and the occupancy rate of pores with an average pore size ≤25μm to be 54.5%; the bubble pressure method was used to measure the filtration rate of porous ceramic Y at a pressure difference of 7kPa on both sides to be 9.2L / min.

[0227] Comparative Example 23

[0228] The method of Example 2 is followed, except that the cooling rate of the first cooling is set to 8° C. / min, to obtain porous ceramic Z.

[0229] In the porous ceramic Z, the bubble pressure method was used to measure the occupancy rate of pores with an average pore size of 60-90μm to be 23.7%, and the occupancy rate of pores with an average pore size ≤25μm to be 46.5%; the bubble pressure method was used to measure the filtration rate of the porous ceramic Z at a pressure difference of 7kPa on both sides to be 14.1L / min.

[0230] Table 1

[0231]

[0232] By comparing the effects of Example 1 and Comparative Example 1 in Table 1, it can be seen that when the weight ratio of the oxide ceramic material to the diatomaceous earth composite material is not in the range of (0.5-2):1, the occupancy rate of pores with an average pore size of 60-90 μm is significantly reduced, the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, and the solid-gas separation efficiency of the porous ceramic finally formed is significantly reduced; by comparing the effects of Example 1 and Comparative Examples 2 and 3 in Table 1, it can be seen that when the amount of alkali metal silicate is not in the range of (4-6) wt.% of the first precursor, the occupancy rate of pores with an average pore size of 60-90 μm is significantly reduced, the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, and the solid-gas separation efficiency of the porous ceramic finally formed is significantly reduced. The occupancy rate of the pores is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 4 and Comparative Example 5 in Table 1, it can be seen that when the calcination temperature for preparing the diatomite composite material is not in the range of 800-830°C, the occupancy rate of the pores with an average pore size of 60-90 μm is significantly decreased, and the occupancy rate of the pores with an average pore size of ≤25 μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 6 in Table 1, it can be seen that when the temperature of the first homogenization is not in the range of 150-180°C, the occupancy rate of the pores with an average pore size of ≤25 μm is significantly increased. Increase, eventually leading to a significant decrease in the solid-gas separation efficiency of the porous ceramic; through the comparison of the effects of Example 2 and Comparative Example 7 in Table 1, it can be seen that when the pH value of the second precursor is less than 8, the occupancy rate of pores with an average pore size of ≤25μm increases significantly, eventually leading to a significant decrease in the solid-gas separation efficiency of the porous ceramic; through the comparison of the effects of Example 2 and Comparative Examples 8 and 9 in Table 1, it can be seen that when the temperature of the second heat treatment is not in the range of 410-630°C, the occupancy rate of pores with an average pore size of 60-90μm decreases significantly, and the occupancy rate of pores with an average pore size of ≤25μm increases significantly, eventually leading to a significant decrease in the solid-gas separation efficiency of the porous ceramic. It can be seen from the comparison of the effects of Example 2, Comparative Examples 10 and 11 in Table 1 that when the temperature of the third heat treatment is not in the range of 660-980°C, the occupancy rate of pores with an average pore size of 60-90 μm is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; It can be seen from the comparison of the effects of Example 2 and Comparative Example 12 in Table 1 that when the temperature of the fourth heat treatment is not in the range of 1100-1150°C, the occupancy rate of pores with an average pore size of 60-90 μm is sharply reduced, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic;By comparing the effects of Example 2 and Comparative Example 13 in Table 1, it can be seen that when the temperature reached by the first cooling is not in the range of 640-960°C, the occupancy rate of pores with an average pore size of ≤25μm increases significantly, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 14 in Table 1, it can be seen that when the temperature reached by the second cooling is not in the range of 400-600°C, the occupancy rate of pores with an average pore size of ≤25μm decreases slightly, and the occupancy rate of pores with an average pore size of ≤25μm increases to a certain extent, which leads to a decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 15 in Table 1, it can be seen that during the immersion process, When the water temperature is lower than 45°C, the occupancy rate of pores with an average pore size of 60-90 μm drops sharply to 0, resulting in a sharp drop in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 16 in Table 1, it can be seen that if the diatomaceous earth composite material is replaced with commercially available calcined diatomaceous earth, the occupancy rate of pores with an average pore size of 60-90 μm is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, ultimately resulting in a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 17 in Table 1, it can be seen that if the second precursor is not soaked in water after multi-step cooling, the occupancy rate of pores with an average pore size of 60-90 μm drops sharply to 0, resulting in the porous ceramic The solid-gas separation efficiency of the porous ceramic drops sharply; by comparing the effects of Example 2 and Comparative Example 18 in Table 1, it can be seen that in the porous ceramics obtained by single-step heat treatment, the occupancy rate of pores with an average pore size of 60-90 μm is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 19 in Table 1, it can be seen that in the porous ceramics obtained by single-step cooling, the occupancy rate of pores with an average pore size of 60-90 μm is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 19 in Table 1, From the effect comparison of Example 20, it can be seen that when the weight ratio of diatomaceous earth and sodium carbonate is not within the range of (6-9): 1, the occupancy rate of pores with an average pore size of 60-90 μm in the porous ceramic is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; from the effect comparison of Example 2 and Comparative Example 21 in Table 1, it can be seen that when the weight ratio of nano-silicon dioxide and sodium carbonate is not within the range of (10-12.5): 1, the occupancy rate of pores with an average pore size of 60-90 μm in the porous ceramic is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25 μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic;By comparing the effects of Example 2 and Comparative Example 22 in Table 1, it can be seen that when the heating rate of the third heat treatment is not within the range of 5-10°C / min, the occupancy rate of pores with an average pore size of 60-90μm in the porous ceramic is significantly reduced, and the occupancy rate of pores with an average pore size of ≤25μm is significantly increased, which ultimately leads to a significant decrease in the solid-gas separation efficiency of the porous ceramic; by comparing the effects of Example 2 and Comparative Example 23 in Table 1, it can be seen that when the cooling rate of the first cooling is not within the range of 4-6°C / min, the occupancy rate of pores with an average pore size of ≤25μm is significantly increased, which ultimately leads to a decrease in the solid-gas separation efficiency of the porous ceramic. ;

[0233] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a porous ceramic, wherein: The preparation method comprises: Step S1. uniformly mixing the oxide ceramic material and the diatomaceous earth composite material to obtain a first precursor; Step S2. mixing the first precursor with an alkali metal silicate to obtain a second precursor; Step S3. The second precursor is subjected to a multi-step heat treatment, a multi-step cooling, and a liquid immersion to obtain the porous ceramic; Wherein, the temperature of the liquid immersion is 45-60°C; Step S1 also includes performing a first homogenization after the mixing is uniform; Step S2 also includes performing a second homogenization after the mixing; Step S3 also includes drying after the liquid is soaked; The weight ratio of the oxide ceramic material to the diatomaceous earth composite material is (0.5-2):1; The oxide ceramic material is zirconium oxide or aluminum oxide; The alkali metal silicate includes one or more of sodium silicate, potassium silicate, sodium metasilicate and potassium metasilicate; The preparation method of the diatomite composite material comprises: uniformly mixing diatomite, nano silicon dioxide and sodium carbonate, and calcining to obtain the diatomite composite material; The weight ratio of diatomaceous earth, nano-silicon dioxide and sodium carbonate is (6-9): (10-12.5): 1; The calcination temperature is 800-830°C; The temperature of the first homogenization is 150-180°C; The amount of the alkali metal silicate is 4-6wt.% of the first precursor; The pH of the second precursor is ≥ 8; The multi-step heat treatment includes a first heat treatment, a second heat treatment, a third heat treatment and a fourth heat treatment; The multi-step cooling includes a first cooling, a second cooling, a third cooling, and a fourth cooling; The temperature of the first heat treatment is 100-145°C, the heating rate is 6-8°C / min, and the holding time is 0.4-0.6h; the temperature of the second heat treatment is 410-630°C, the heating rate is 2-8°C / min, and the holding time is 0.7-1h; the temperature of the third heat treatment is 660-980°C, the heating rate is 5-10°C / min, and the holding time is 0.1-0.2h; the temperature of the fourth heat treatment is 1100-1150°C, the heating rate is 3-10°C / min, and the holding time is 4.8-7.2h; The temperature reached by the first cooling is 640-960°C, the cooling rate is 4-6°C / minute, and the holding time is 0.1-0.2h; the temperature reached by the second cooling is 400-600°C, the cooling rate is 3-6°C / minute, and the holding time is 0.2-0.4h; the temperature reached by the third cooling is 175-270°C, the cooling rate is 2-5°C / minute, and the holding time is 0.05-0.1h; the temperature reached by the fourth cooling is 70-110°C, and the cooling rate is 5-10°C / minute; The liquid immersion time is 24-48h; The liquid immersion is immersion in water.

2. A porous ceramic obtained by the preparation method according to claim 1, wherein: The bubble pressure method is used to measure that in the porous ceramic, the occupancy rate of pores with an average pore size of 60-90 μm is 25-30%, and the occupancy rate of small pores with an average pore size of ≤25 μm is 20-25%; And / or, the filtration rate measured by the bubble pressure method at a pressure difference of 7 kPa on both sides of the porous ceramic is 16-20 L / min.

3. Use of the porous ceramic according to claim 2 in solid-gas separation.

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