Alumina foamed ceramic structured packing as well as preparation method and application thereof

Abstract

The invention relates to an aluminum oxide foamed ceramic structured packing and a preparation method and application thereof, the preparation method comprises the following steps: mixing pseudo-boehmite, gibbsite, alpha-aluminum oxide, concentrated nitric acid and water to obtain ceramic slurry; organic foam is coated with the ceramic slurry, then the organic foam is put into a mold to be subjected to mold closing curing, and a corrugated plate sheet is obtained; a corrugated plate is soaked in the ceramic slurry, then drying and curing are conducted, and a pretreated corrugated plate is obtained; stacking a plurality of pretreated corrugated plates according to a specified sequence, then integrally dipping in ceramic slurry, and then drying and curing to obtain a primary filler body; and roasting the primary filler body to obtain the aluminum oxide foamed ceramic structured filler. Alpha-aluminum oxide in the aluminum oxide foamed ceramic structured packing provided by the invention is relatively high in purity, excellent in corrosion resistance and mechanical property and not easy to deform and crack, the wall thickness of a single piece is less than or equal to 1.5 mm, and the aluminum oxide foamed ceramic structured packing has a good mass transfer effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical separation technology, in particular to a kind of alumina foam ceramic structured packing and its preparation method and application. BACKGROUND

[0002] Industrial ceramic structured packing as the core material of chemical separation, its structural regularity, performance stability and cost economy directly affect the efficiency and comprehensive benefit of industrial production. The mainstream ceramic structured packing on the market is mainly divided into two categories, both of which have technical defects that are difficult to balance.

[0003] Among them, the traditional clay-based ceramic structured packing takes natural clay as the core raw material and relies on the excellent plasticity of clay to ensure the forming effect. The preparation of clay-based ceramic structured packing mainly includes mixing high clay, montmorillonite and other core clay with alumina powder to form a blank, and then extruding, rolling, cutting, pasting, drying and baking to obtain the product. Because the core component of clay is hydrous aluminum silicate (general formula is xSiO2·yAl2O3·zH2O), the finished product forms a silicon-aluminum composite structure, and the SiO2 content is generally 15-30wt.%, which further leads to a significant shortcoming in corrosion resistance. It cannot be used in strong acid media such as concentrated sulfuric acid, concentrated nitric acid and hydrofluoric acid environment. In addition, clay-based ceramic structured packing mainly uses extrusion rolling process, and the wall thickness is generally thick due to the limitation of structural strength and forming precision, the specific surface area is low, which affects the heat transfer efficiency and makes it difficult to meet the demand of high-efficiency separation, limiting its adaptability in high-end chemical devices.

[0004] Foamed silicon carbide structured packing has excellent corrosion resistance due to the strong covalent nature of Si-C bond. The three-dimensional network structure and ultra-thin skeleton (≤1.5mm) of foamed silicon carbide structured packing make the specific surface area larger, and the structure is regular, which can ensure the uniformity of fluid distribution and smaller mass transfer resistance. In high temperature and strong corrosion environment, the mass transfer efficiency and structural stability are outstanding. However, due to the limitation of preparation process, the production cost of foamed silicon carbide structured packing is high, and the market popularization is difficult. Due to the use of carbon-silicon reaction sintering process, the sintering temperature is as high as 1600℃ or above, and it must be carried out in a vacuum furnace, which has high equipment investment and energy consumption cost, and is difficult to be widely accepted by medium and high-end industrial scenes.

[0005] Therefore, the current industrial field puts forward the demand for ceramic structured packing such as ultra-thin wall thickness, high specific surface area, strong corrosion resistance and low cost mass production, and the traditional clay-based ceramic structured packing is difficult to balance the wall thickness and performance. Foamed silicon carbide structured packing has excellent performance but high cost, so it is necessary to provide a new type of ceramic packing with high α-alumina content, excellent performance, simple preparation and controllable cost, which is a technical problem to be solved in the current industrial ceramic field. SUMMARY

[0006] In view of the above problems, the present application aims to provide an alumina foam ceramic structured packing, a preparation method and application thereof.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a preparation method of an alumina foam ceramic structured packing, which comprises the following steps:

[0009] S1, mixing pseudo-boehmite, gibbsite, alpha-alumina, concentrated nitric acid and water to obtain a ceramic slurry;

[0010] S2, coating the ceramic slurry obtained in step S1 on an organic foam, and then placing it in a mold for mold closing and curing to obtain a corrugated sheet;

[0011] S3, immersing the corrugated sheet obtained in step S2 in the ceramic slurry obtained in step S1, and then drying and curing to obtain a pretreated corrugated sheet;

[0012] S4, stacking a plurality of the pretreated corrugated sheets obtained in step S3 according to a specified order, and then immersing the whole in the ceramic slurry obtained in step S1, and then drying and curing to obtain a packing preliminary body;

[0013] S5, firing the packing preliminary body obtained in step S4 to obtain an alumina foam ceramic structured packing.

[0014] In the preparation method, pseudo-boehmite, gibbsite, alpha-alumina, concentrated nitric acid and water are compounded, wherein the pseudo-boehmite can quickly form a stable colloid under the action of concentrated nitric acid, the stable colloid can wrap gibbsite and alpha-alumina to improve the dispersibility of the powder in the slurry, in the firing process, the gibbsite can slowly dehydrate and phase change to reduce the risk of cracking, and the alpha-alumina as a skeleton reinforcing phase can improve the mechanical properties and chemical stability of the product.

[0015] In the present application, the organic foam can be commonly used in the art, including but not limited to polyurethane sponge foam, and the pore size is 1-3 mm.

[0016] Preferably, the mass ratio of pseudo-boehmite, gibbsite and alpha-alumina in step S1 is (1.5-2.0):(3-4):(8-15), for example, it can be 1.5:3:8, 1.5:4:10, 1.5:3:12, 1.5:4:14, 1.5:4:15, 2:3:8, 2:4:9, 2:3:12, 2:4:11 or 2:4:15, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0017] Preferably, the pseudo-boehmite comprises industrial grade pseudo-boehmite.

[0018] Preferably, the pseudo-boehmite has a purity of ≥98.5%, such as 98.5%, 98.6%, 98.8%, 99.0%, 99.2%, 99.4%, 99.6%, 99.8%, or 99.9%, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0019] Preferably, the pseudo-boehmite has a particle size of 1-3 μm, such as 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, or 3 μm, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0020] Preferably, the pseudo-boehmite has a peptization index of ≥90%, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0021] In the present application, the peptization index of the pseudo-boehmite is the peptization index at 25°C with a solid content of 10%.

[0022] Preferably, the gibbsite comprises industrial grade gibbsite.

[0023] Preferably, the gibbsite has a purity of ≥97.5%, such as 97.5%, 98%, 98.5%, 99%, 99.5%, or 99.9%, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0024] Preferably, the gibbsite has a particle size of 2-4 μm, such as 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, or 4 μm, but is not limited to the listed values, other unlisted values within the range of values are also applicable.

[0025] In the present application, the gibbsite slowly dehydrates and phase changes during the calcination stage, and is able to form an active alumina phase with the pseudo-boehmite.

[0026] Preferably, the α-alumina comprises industrial grade α-alumina.

[0027] Preferably, the purity of the α-alumina is ≥99.2%, for example, it can be 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8% or 99.9%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the α-alumina comprises α-alumina with a first particle size or a combination of α-alumina with a first particle size and α-alumina with a second particle size.

[0029] Preferably, the particle size of the first α-alumina is 3-5 μm, for example, it can be 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm or 5 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the particle size of the second α-alumina is 1-2 μm, for example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, when the first-size α-alumina and the second-size α-alumina are used in combination, their mass ratio is (6-7):(4-3), for example, it can be 6:4, 6.5:3.5 or 7:3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] In this invention, the α-alumina serves as a framework reinforcing phase, ensuring the mechanical properties and chemical stability of the product.

[0033] Preferably, the concentrated nitric acid includes industrial-grade concentrated nitric acid.

[0034] Preferably, the mass concentration of the concentrated nitric acid is 65-68%, for example, it can be 65%, 65.5%, 66%, 66.5%, 67%, 67.5% or 68%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the solid content of the ceramic slurry is 55-60%, for example, it can be 55%, 56%, 57%, 58%, 59% or 60%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the viscosity of the ceramic slurry is 180-300 mPa·s, for example, it can be 180 mPa·s, 200 mPa·s, 220 mPa·s, 240 mPa·s, 260 mPa·s, 280 mPa·s or 300 mPa·s, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] In this invention, the ceramic slurry is uniform and stable, shows no stratification after standing for 24 hours, and has a settling rate of ≤1.5%.

[0038] Preferably, the preparation of the ceramic slurry in step S1 specifically includes the following steps:

[0039] S11, mixed with water and concentrated nitric acid, is subjected to the first stirring process to obtain the first slurry;

[0040] S12, add boehmite to the first slurry obtained in step S11, and perform a second stirring treatment to obtain a second slurry;

[0041] S13, add gibbsite and α-alumina to the second slurry obtained in step S12, and perform a third stirring treatment to obtain a ceramic slurry.

[0042] Preferably, the stirring speed in step S11 is 1000-1400 r / min, for example, it can be 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min or 1400 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the time for the first stirring treatment in step S11 is 8-12 minutes, for example, it can be 8 minutes, 9 minutes, 10 minutes, 11 minutes or 12 minutes, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the pH value after the first stirring treatment in step S11 is 3.8-4.2, for example, it can be 3.8, 3.9, 4, 4.1 or 4.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] In this invention, in step S11, a certain amount of deionized water is generally added to the stirred tank first, concentrated nitric acid is slowly added and stirring is started, and the system is adjusted to a suitable pH value.

[0046] Preferably, the stirring speed in step S12 is 200-1000 r / min, for example, it can be 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min or 1000 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the second stirring time in step S12 is 25-35 min, for example, it can be 25 min, 26 min, 28 min, 30 min, 32 min, 34 min or 35 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] In this invention, adding boehmite in step S12 and stirring it can promote the formation of a uniform colloid by using concentrated sulfuric acid, and the particle size of the colloid is ≤500nm.

[0049] Preferably, the third stirring process in step S13 includes high-speed stirring and low-speed stirring performed sequentially.

[0050] In this invention, the gibbsite and α-alumina mentioned in step S13 can be added in batches or all at once. By stirring, the dispersibility of the powder is improved by the encapsulation effect of the colloid.

[0051] Preferably, the high-speed stirring speed is 1800-2200 r / min, for example, it can be 1800 r / min, 1850 r / min, 1900 r / min, 1950 r / min, 2000 r / min, 2050 r / min, 2100 r / min, 2150 r / min or 2200 r / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0052] Preferably, the high-speed stirring time is 80-100 min, for example, it can be 80 min, 85 min, 90 min, 95 min or 100 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, the speed of the low-speed stirring is 600-800 r / min, for example, it can be 600 r / min, 650 r / min, 700 r / min, 750 r / min or 800 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] Preferably, the low-speed stirring time is 20-30 minutes, for example, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes or 30 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] Preferably, ultrasonic dispersion is performed during the high-speed stirring.

[0056] Preferably, the power of the ultrasonic dispersion is 400-600W, for example, it can be 400W, 420W, 450W, 480W, 500W, 520W, 550W, 580W or 600W, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] Preferably, the ultrasonic dispersion time is 30-40 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min or 40 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] Preferably, the frequency of the ultrasonic dispersion is 20-25Hz, for example, it can be 20Hz, 21Hz, 22Hz, 23Hz, 24Hz or 25Hz, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] In this invention, ultrasonic dispersion is used during high-speed stirring to completely eliminate the agglomeration of ultrafine powders.

[0060] Preferably, the mold is preheated before being placed into the mold as described in step S2.

[0061] Preferably, the preheating temperature is 120-180℃, for example, it can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0062] Preferably, the temperature for mold closing and curing is 120-180℃, for example, it can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0063] Preferably, the curing time of the mold is 10-30s, for example, it can be 10s, 12s, 14s, 16s, 18s, 20s, 22s, 24s, 26s, 28s or 30s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] Preferably, in step S3, the sequential impregnation and drying curing are considered as one operation, and the operation is repeated 3-4 times to obtain a pretreated corrugated sheet, for example, 3 or 4 times.

[0065] In this invention, by optimizing and controlling the number of repeated operations, the wall thickness of a single piece in the alumina foam ceramic structured packing can be further precisely controlled to ≤1.5mm, thereby increasing the surface area of ​​the alumina foam ceramic structured packing and thus improving the mass transfer effect.

[0066] Preferably, the removal of excess slurry between the impregnation and drying curing process allows the foam to open up.

[0067] Preferably, the method for removing excess slurry includes centrifugation or air blowing.

[0068] Preferably, the drying and curing temperature in step S3 is 120-180℃, for example, it can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0069] Preferably, the drying and curing time in step S3 is 3-10 min, for example, it can be 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] Preferably, the drying and curing temperature in step S4 is 120-180℃, for example, it can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0071] Preferably, the drying and curing time in step S4 is 3-10 min, for example, it can be 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] Preferably, in step S4, the sequential impregnation and drying curing are considered as one operation, and the operation is repeated 1-2 times to obtain the filler precursor, for example, it can be done once or twice.

[0073] In this invention, by optimizing and controlling the number of repeated operations, the wall thickness of a single piece in the alumina foam ceramic structured packing can be further precisely controlled to ≤1.5mm, thereby increasing the surface area of ​​the alumina foam ceramic structured packing and thus improving the mass transfer effect.

[0074] Preferably, the roasting in step S5 includes a first heating to a first endpoint temperature, a first holding at the first endpoint temperature, a second heating to a second endpoint temperature, a second holding at the second endpoint temperature, and then cooling.

[0075] Preferably, the first heating rate is 1-10℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0076] Preferably, the first endpoint temperature is 600-800℃, for example, it can be 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃ or 800℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0077] Preferably, the first heat preservation time is 0.5-2h, for example, it can be 0.5h, 0.6h, 0.8h, 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] Preferably, the second heating rate is 5-15℃ / min, for example, it can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min or 15℃ / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0079] Preferably, the second endpoint temperature is 1200-1400℃, for example, it can be 1200℃, 1220℃, 1250℃, 1280℃, 1300℃, 1320℃, 1350℃, 1380℃ or 1400℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0080] Preferably, the second heat preservation time is 0.5-5h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] Preferably, the cooling rate is 10-30℃ / min, for example, it can be 10℃ / min, 12℃ / min, 15℃ / min, 18℃ / min, 20℃ / min, 22℃ / min, 25℃ / min, 28℃ / min or 30℃ / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0082] In this invention, by adopting the above-mentioned calcination process, the dehydration phase change can be completed in an air atmosphere without the need for a vacuum environment and inert gas protection, which simplifies the process and reduces energy consumption and equipment costs.

[0083] As a preferred embodiment of the first aspect of the present invention, the preparation method includes the following steps:

[0084] S1 is prepared by mixing boehmite, gibbsite, α-alumina, concentrated nitric acid, and water to obtain a ceramic slurry.

[0085] S11, mix water and concentrated nitric acid, then stir for 8-12 minutes at a speed of 1000-1400 r / min to obtain the first slurry with a pH of 3.8-4.2;

[0086] S12, add boehmite to the first slurry obtained in step S11, and then perform a second stirring treatment at a speed of 200-1000 r / min for 25-35 min to obtain a second slurry;

[0087] S13, add gibbsite and α-alumina to the second slurry obtained in step S12, then stir at high speed for 80-100 min at 1800-2200 r / min, then stir at low speed for 20-30 min at 600-800 r / min. During the high-speed stirring, ultrasonically disperse at 400-600 W and 20-25 Hz for 30-40 min to obtain ceramic slurry;

[0088] S2, the ceramic slurry obtained in step S1 is coated onto organic foam, and then placed into a mold preheated at 120-180°C for molding and curing at 120-180°C for 10-30 seconds to obtain a corrugated sheet.

[0089] S3, Immerse the corrugated sheet obtained in step S2 in the ceramic slurry obtained in step S1, remove excess slurry to open the foam, and then dry and cure at 120-180℃ for 3-10 minutes. Repeat the operation 3-4 times to obtain the pretreated corrugated sheet.

[0090] S4, stack the pretreated corrugated plates obtained in several steps S3 in a specified order, then immerse the whole plate in the ceramic slurry obtained in step S1, and then dry and cure at 120-180℃ for 3-10 minutes. Repeat the operation 1-2 times to obtain the filler primary body.

[0091] S5, the initial filler obtained in step S4 is calcined, including a first heating at a rate of 1-10℃ / min to a first endpoint temperature of 600-800℃, a first holding at the first endpoint temperature for 0.5-2h, a second heating at a rate of 5-15℃ / min to a second endpoint temperature of 1200-1400℃, a second holding at the second endpoint temperature for 0.5-5h, and then cooling at a rate of 10-30℃ / min to obtain alumina foam ceramic structured filler.

[0092] In a second aspect, the present invention provides an alumina foam ceramic structured packing, wherein the alumina foam ceramic structured packing is obtained by the preparation method of the alumina foam ceramic structured packing described in the first aspect of the present invention.

[0093] The alumina foam ceramic structured filler provided by this invention has an α-alumina purity of over 99%, is corrosion resistant, has high mechanical strength, is not easily deformed or cracked, and has a single-piece wall thickness of ≤1.5mm, thus exhibiting good mass transfer performance.

[0094] Thirdly, the present invention provides an application of the alumina foam ceramic structured packing as described in the second aspect of the present invention, wherein the alumina foam ceramic structured packing is used for chemical separation.

[0095] The alumina foam ceramic structured packing provided by this invention has superior overall performance compared to traditional clay-based ceramic structured packing, and has a cost advantage compared to traditional foam silicon carbide structured packing. It can directly replace existing ceramic-based packing in distillation columns without adjusting the column structure, and can be widely used in corrosive distillation systems, high-temperature distillation, and precision distillation scenarios.

[0096] Compared with the prior art, the present invention has the following beneficial effects:

[0097] (1) The alumina foam ceramic structured filler provided by the present invention has a purity of α-alumina of more than 99% and a porosity of more than 61.0% under optimal conditions. The mass loss rate after soaking in a 20% sulfuric acid solution for 3 weeks is less than 0.40%. It has good chemical stability and mechanical properties, good flatness, is not easy to deform and crack, and the single-piece wall thickness is ≤1.5mm, which has good mass transfer effect.

[0098] (2) The preparation method of alumina foam ceramic structured filler provided by the present invention is simple to operate, the equipment is easy to obtain, and it can be industrialized.

[0099] (3) The alumina foam ceramic structured packing provided by the present invention is suitable for harsh working environments, such as corrosive distillation systems, high-temperature distillation and precision distillation scenarios. Detailed Implementation

[0100] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0101] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0102] Example 1

[0103] This embodiment provides a method for preparing alumina foam ceramic structured filler, the preparation method including the following steps:

[0104] S1, a ceramic slurry is obtained by mixing boehmite, gibbsite, α-alumina, concentrated nitric acid, and water; wherein the mass ratio of boehmite, gibbsite, and α-alumina is 1.8:3.5:11, the purity of boehmite is 98.5%, the particle size is 1-3 μm, and the colloidal index is 90%, the purity of gibbsite is 97.5%, the particle size is 2-4 μm, the purity of α-alumina is 99.3%, the particle size is 3-5 μm, the mass concentration of concentrated nitric acid is 66%, the solid content of the ceramic slurry is 58%, and the viscosity is 240 mPa·s; the preparation of the ceramic slurry specifically includes the following steps:

[0105] S11, mixed with water and concentrated nitric acid, was then stirred for 10 minutes at a speed of 1200 r / min to obtain the first slurry with a pH of 4.0;

[0106] S12, add boehmite to the first slurry obtained in step S11, and then perform a second stirring treatment at a speed of 600 r / min for 30 min to obtain a second slurry;

[0107] S13, add gibbsite and α-alumina to the second slurry obtained in step S12, then stir at high speed for 90 minutes at 2000 r / min, then stir at low speed for 25 minutes at 700 r / min. During the high-speed stirring, ultrasonically disperse at 500 W and 22 Hz for 35 minutes to obtain ceramic slurry.

[0108] S2, the ceramic slurry obtained in step S1 is coated onto polyurethane foam (the pore size is 1-3mm), and then placed into a mold preheated at 150°C for molding and curing at 150°C for 30s to obtain a corrugated sheet.

[0109] S3, the corrugated sheet obtained in step S2 is immersed in the ceramic slurry obtained in step S1, the excess slurry is removed to open the foam, and then it is dried and cured at 150°C for 6 minutes. The operation is repeated 4 times to obtain the pretreated corrugated sheet.

[0110] S4, stack the pretreated corrugated plates obtained in several steps S3 in a specified order, then immerse the whole plate in the ceramic slurry obtained in step S1, and then dry and cure at 150°C for 6 minutes. Repeat the operation once to obtain the filler initial body.

[0111] S5, the initial filler obtained in step S4 is calcined, including a first heating at a rate of 3℃ / min to a first endpoint temperature of 600℃, a first holding at the first endpoint temperature for 1h, a second heating at a rate of 10℃ / min to a second endpoint temperature of 1380℃, a second holding at the second endpoint temperature for 3h, and then cooling to room temperature at a rate of 15℃ / min to obtain alumina foam ceramic structured filler.

[0112] In this embodiment, the α-alumina purity in the alumina foam ceramic structured filler is ≥99%, and the porosity reaches 62.0%.

[0113] Example 2

[0114] This embodiment provides a method for preparing alumina foam ceramic structured filler, the preparation method including the following steps:

[0115] S1, a ceramic slurry is prepared by mixing boehmite, gibbsite, α-alumina, concentrated nitric acid, and water; wherein the mass ratio of boehmite, gibbsite, and α-alumina is 2:3:8; the purity of boehmite is 98.5%, the particle size is 1-3 μm, and the colloidal index is 90%; the purity of gibbsite is 97.5%, the particle size is 2-4 μm; the purity of α-alumina is 99.3%; α-alumina with a first particle size of 3-5 μm and a second particle size of 1-2 μm are compounded in a mass ratio of 7:3; the mass concentration of concentrated nitric acid is 65%; the solid content of the ceramic slurry is 59%; and the viscosity is 290 mPa·s. The preparation of the ceramic slurry specifically includes the following steps:

[0116] S11, mixed with water and concentrated nitric acid, was then stirred for 8 minutes at a speed of 1400 r / min to obtain the first slurry with a pH of 4.2;

[0117] S12, add boehmite to the first slurry obtained in step S11, and then perform a second stirring treatment at a speed of 1000 r / min for 25 min to obtain a second slurry;

[0118] S13, add gibbsite and α-alumina to the second slurry obtained in step S12, then stir at high speed for 80 minutes at 2200 r / min, then stir at low speed for 30 minutes at 600 r / min. During the high-speed stirring, ultrasonically disperse at 400 W and 25 Hz for 30 minutes to obtain ceramic slurry.

[0119] S2, the ceramic slurry obtained in step S1 is coated onto polyurethane foam (the pore size is 1-3mm), and then placed into a mold preheated at 180°C for molding and curing at 180°C for 10s to obtain a corrugated sheet.

[0120] S3, Immerse the corrugated sheet obtained in step S2 in the ceramic slurry obtained in step S1, remove excess slurry to open the foam, and then dry and cure at 180°C for 3 minutes. Repeat the operation 3 times to obtain the pretreated corrugated sheet.

[0121] S4, stack the pretreated corrugated plates obtained in several steps S3 in a specified order, then immerse the whole plate in the ceramic slurry obtained in step S1, and then dry and cure at 180°C for 3 minutes. Repeat the operation twice to obtain the filler initial body.

[0122] S5, the initial filler obtained in step S4 is calcined, including a first heating at a rate of 1℃ / min to a first endpoint temperature of 700℃, a first holding at the first endpoint temperature for 2 hours, a second heating at a rate of 15℃ / min to a second endpoint temperature of 1400℃, a second holding at the second endpoint temperature for 0.5 hours, and then cooling to room temperature at a rate of 10℃ / min to obtain alumina foam ceramic structured filler.

[0123] In this embodiment, the alumina foam ceramic structured filler has an α-alumina purity of ≥99% and a porosity of 61.0%.

[0124] Example 3

[0125] This embodiment provides a method for preparing alumina foam ceramic structured filler, the preparation method including the following steps:

[0126] S1, a ceramic slurry is prepared by mixing boehmite, gibbsite, α-alumina, concentrated nitric acid, and water; wherein the mass ratio of boehmite, gibbsite, and α-alumina is 1.5:4:15; the purity of boehmite is 98.5%, the particle size is 1-3 μm, and the colloidal index is 90%; the purity of gibbsite is 97.5%, the particle size is 2-4 μm; the purity of α-alumina is 99.3%; α-alumina with a first particle size of 3-5 μm and a second particle size of 1-2 μm are compounded in a mass ratio of 6:4; the mass concentration of concentrated nitric acid is 68%; the solid content of the ceramic slurry is 56%; and the viscosity is 260 mPa·s. The preparation of the ceramic slurry specifically includes the following steps:

[0127] S11, mixed with water and concentrated nitric acid, was then stirred for 12 minutes at a speed of 1000 r / min to obtain the first slurry with a pH of 3.8;

[0128] S12, add boehmite to the first slurry obtained in step S11, and then perform a second stirring treatment at a speed of 200 r / min for 35 min to obtain a second slurry;

[0129] S13, add gibbsite and α-alumina to the second slurry obtained in step S12, then stir at high speed for 100 min at 1800 r / min, then stir at low speed for 20 min at 800 r / min. During the high-speed stirring, ultrasonically disperse at 600 W and 20 Hz for 40 min to obtain ceramic slurry.

[0130] S2, the ceramic slurry obtained in step S1 is coated onto polyurethane foam (the pore size is 1-3mm), and then placed into a mold preheated at 120°C for molding and curing at 120°C for 20s to obtain a corrugated sheet.

[0131] S3, the corrugated sheet obtained in step S2 is immersed in the ceramic slurry obtained in step S1, excess slurry is removed to open the foam, and then dried and cured at 120°C for 10 minutes. The operation is repeated 3 times to obtain the pretreated corrugated sheet.

[0132] S4, stack the pretreated corrugated plates obtained in several steps S3 in a specified order, then immerse the whole plate in the ceramic slurry obtained in step S1, and then dry and cure at 120°C for 10 minutes. Repeat the operation twice to obtain the filler initial body.

[0133] S5, the initial filler obtained in step S4 is calcined, including a first heating at a rate of 10℃ / min to a first endpoint temperature of 800℃, a first holding at the first endpoint temperature for 0.5h, a second heating at a rate of 5℃ / min to a second endpoint temperature of 1200℃, a second holding at the second endpoint temperature for 5h, and then cooling to room temperature at a rate of 30℃ / min to obtain alumina foam ceramic structured filler.

[0134] In this embodiment, the purity of α-alumina in the alumina foam ceramic structured filler is ≥99%, and the porosity reaches 64.2%.

[0135] Example 4

[0136] This embodiment provides a method for preparing alumina foam ceramic structured filler. The only difference from Example 1 is that the mass ratio of boehmite, gibbsite, and α-alumina is adjusted to 0.5:3.5:11, while the total mass of the three remains unchanged.

[0137] Example 5

[0138] This embodiment provides a method for preparing alumina foam ceramic structured filler. The only difference from Example 1 is that the mass ratio of boehmite, gibbsite, and α-alumina is adjusted to 1.8:2:11, while the total mass of the three remains unchanged.

[0139] Example 6

[0140] This embodiment provides a method for preparing alumina foam ceramic structured filler. The only difference from Embodiment 1 is that step S3, which involves impregnation, removal of excess slurry, and drying and curing, is considered as one operation, and the operation is repeated 6 times.

[0141] Example 7

[0142] This embodiment provides a method for preparing alumina foam ceramic structured filler. The only difference from Embodiment 1 is that step S3, which involves impregnation, removal of excess slurry, and drying and curing, is considered as one operation, and the operation is repeated once.

[0143] The performance of the alumina foam ceramic structured filler obtained in the above embodiments was tested, and the results are shown in Table 1:

[0144] Visual inspection was performed on the alumina foam ceramic structured filler to observe for surface cracks and measure the wall thickness of individual sheets.

[0145] The corrosion resistance of alumina foam ceramic structured filler was tested by immersing it in a 20% sulfuric acid solution for 3 weeks and calculating the mass loss rate.

[0146] Table 1

[0147]

[0148] The following points can be observed from the data in Table 1:

[0149] (1) As can be seen from the data of Examples 1-3, the alumina foam ceramic structured filler provided by the present invention can achieve a purity of α-alumina of more than 99% under better conditions, a single sheet thickness of less than 1.5 mm, no surface cracks, a porosity of more than 61.0%, and a mass loss rate of less than 0.40% after soaking in a 20% mass concentration sulfuric acid solution for 3 weeks.

[0150] (2) As can be seen from the comparison between Example 1 and Examples 4-5, by optimizing the mass ratio of boehmite, gibbsite and α-alumina in this invention, surface cracking can be further avoided and corrosion resistance can be improved.

[0151] (3) As can be seen from the comparison between Example 1 and Example 6-7, the present invention can further control the thickness of a single piece by optimizing the number of times the impregnation and other operations are repeated in step S3, thereby increasing the specific surface area and enhancing the mass transfer effect, while avoiding the single piece thickness being too thin, which would affect the strength of the overall alumina foam ceramic structured filler.

[0152] In summary, the alumina foam ceramic structured filler provided by this invention has high α-alumina purity, excellent corrosion resistance and mechanical properties, is not easily deformed or cracked, and has a single-piece wall thickness of ≤1.5mm, resulting in good mass transfer performance.

[0153] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing alumina foam ceramic structured filler, characterized in that, The preparation method includes the following steps: S1 is prepared by mixing boehmite, gibbsite, α-alumina, concentrated nitric acid, and water to obtain a ceramic slurry. S2, the ceramic slurry obtained in step S1 is coated onto organic foam, and then placed into a mold for molding and curing to obtain a corrugated sheet; S3, the corrugated sheet obtained in step S2 is immersed in the ceramic slurry obtained in step S1, and then dried and cured to obtain a pretreated corrugated sheet; S4, the pretreated corrugated plates obtained in several steps S3 are stacked in a specified order, and then the whole plate is immersed in the ceramic slurry obtained in step S1, and then dried and cured to obtain the filler primary body; S5, the initial filler obtained in step S4 is calcined to obtain alumina foam ceramic structured filler.

2. The preparation method according to claim 1, characterized in that, The mass ratio of boehmite, gibbsite, and α-alumina in step S1 is (1.5-2.0):(3-4):(8-15); Preferably, the pseudoboehmite includes industrial-grade pseudoboehmite; Preferably, the purity of the pseudoboehmite is ≥98.5%; Preferably, the particle size of the pseudoboehmite is 1-3 μm; Preferably, the gel solubility index of the pseudoboehmite is ≥90%; Preferably, the gibbsite includes industrial-grade gibbsite; Preferably, the purity of the gibbsite is ≥97.5%; Preferably, the particle size of the gibbsite is 2-4 μm; Preferably, the α-alumina comprises industrial-grade α-alumina; Preferably, the purity of the α-alumina is ≥99.2%; Preferably, the α-alumina comprises α-alumina with a first particle size or a combination of α-alumina with a first particle size and α-alumina with a second particle size; Preferably, the particle size of the first α-alumina is 3-5 μm; Preferably, the particle size of the second α-alumina is 1-2 μm; Preferably, when the first-size α-alumina and the second-size α-alumina are used in combination, the mass ratio of the two is (6-7):(4-3); Preferably, the concentrated nitric acid includes industrial-grade concentrated nitric acid; Preferably, the concentrated nitric acid has a mass concentration of 65-68%; Preferably, the solid content of the ceramic slurry is 55-60%; Preferably, the viscosity of the ceramic slurry is 180-300 mPa·s.

3. The preparation method according to claim 1 or 2, characterized in that, The preparation of the ceramic slurry in step S1 specifically includes the following steps: S11, mixed with water and concentrated nitric acid, is subjected to the first stirring process to obtain the first slurry; S12, add boehmite to the first slurry obtained in step S11, and perform a second stirring treatment to obtain a second slurry; S13, add gibbsite and α-alumina to the second slurry obtained in step S12, and perform a third stirring treatment to obtain a ceramic slurry.

4. The preparation method according to claim 3, characterized in that, Step S11: The stirring speed for the first stirring process is 1000-1400 r / min; Preferably, the time for the first stirring treatment in step S11 is 8-12 minutes; Preferably, the pH value after the first stirring treatment in step S11 is 3.8-4.2; Preferably, the stirring speed in step S12 is 200-1000 r / min; Preferably, the second stirring process in step S12 takes 25-35 minutes; Preferably, the third stirring process in step S13 includes high-speed stirring and low-speed stirring performed sequentially; Preferably, the high-speed stirring speed is 1800-2200 r / min; Preferably, the high-speed stirring time is 80-100 minutes; Preferably, the low-speed stirring speed is 600-800 r / min; Preferably, the low-speed stirring time is 20-30 minutes; Preferably, ultrasonic dispersion is performed during the high-speed stirring; Preferably, the power of the ultrasonic dispersion is 400-600W; Preferably, the ultrasonic dispersion time is 30-40 minutes; Preferably, the frequency of the ultrasonic dispersion is 20-25 Hz.

5. The preparation method according to any one of claims 1-4, characterized in that, Before placing the item into the mold as described in step S2, preheat the mold. Preferably, the preheating temperature is 120-180℃; Preferably, the temperature for mold closing and curing is 120-180℃; Preferably, the curing time of the mold is 10-30 seconds.

6. The preparation method according to any one of claims 1-5, characterized in that, In step S3, the sequential impregnation and drying curing are considered as one operation. The operation is repeated 3-4 times to obtain a pretreated corrugated sheet. Preferably, the removal of excess slurry between the impregnation and drying / curing processes allows the foam to open up. Preferably, the method for removing excess slurry includes centrifugation or air blowing; Preferably, the drying and curing temperature in step S3 is 120-180℃; Preferably, the drying and curing time in step S3 is 3-10 minutes.

7. The preparation method according to any one of claims 1-6, characterized in that, The drying and curing temperature in step S4 is 120-180℃; Preferably, the drying and curing time in step S4 is 3-10 minutes; Preferably, in step S4, the impregnation and drying curing are performed sequentially as one operation, and the operation is repeated 1-2 times to obtain the filler primary body.

8. The preparation method according to any one of claims 1-7, characterized in that, The roasting in step S5 includes a first heating to a first endpoint temperature, a first holding at the first endpoint temperature, a second heating to a second endpoint temperature, a second holding at the second endpoint temperature, and then cooling. Preferably, the first heating rate is 1-10℃ / min; Preferably, the first endpoint temperature is 600-800℃; Preferably, the first heat preservation time is 0.5-2 hours; Preferably, the second heating rate is 5-15℃ / min; Preferably, the second endpoint temperature is 1200-1400℃; Preferably, the second heat preservation time is 0.5-5 hours; Preferably, the cooling rate is 10-30℃ / min.

9. A structured alumina foam ceramic filler, characterized in that, The alumina foam ceramic structured filler is obtained by the preparation method of the alumina foam ceramic structured filler according to any one of claims 1-8.

10. An application of the alumina foam ceramic structured filler as described in claim 9, characterized in that, The alumina foam ceramic structured packing is used for chemical separation.

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