Composite porous ceramic ball for deoxidation process and preparation method of composite porous ceramic ball

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a composite porous ceramic ball for a deoxidation process and a preparation method of the composite porous ceramic ball. The ceramic ball comprises the following components in percentage by mass: 55-70% of aluminum oxide, 20-30% of silicon dioxide, 5-10% of cerium oxide and 3-8% of zirconium oxide. The ceramic ball has a three-level pore structure formed by surface through holes, internal mesopores and micropores. The preparation method comprises the following steps: pretreating alumina with a composite treatment liquid, mixing the pretreated alumina with other raw materials, carrying out ball milling to prepare slurry, and carrying out sol-gel-foaming, molding, drying, two-stage sintering and steam post-treatment. Through composition optimization, structural design and process innovation, the ceramic ball has high compressive strength, large specific surface area and excellent mass transfer performance, oxygen can be deeply removed to 0.1 ppm or below when the ceramic ball is used as a deoxidation catalyst carrier, the service life of the ceramic ball exceeds 2000 hours, and the ceramic ball is suitable for efficient purification of feed gas in processes of hydrogen production, ammonia synthesis and the like.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a composite porous ceramic ball for deoxygenation processes and its preparation method. Background Technology

[0002] In modern industry, key processes such as hydrogen production, ammonia synthesis, and hydrogen storage have extremely stringent requirements for the purity of feedstock gases. Deep removal of oxygen impurities is a core element in ensuring the safe and efficient operation of the system. For example, in ammonia synthesis, if the oxygen content in the feedstock gas exceeds 0.3%, it can trigger a sulfur poisoning reaction in the Co-Mo conversion catalyst, leading to a decrease in catalyst activity of more than 30%. A 300,000-ton-per-year ammonia synthesis unit experienced an abnormal temperature rise of 200°C in the catalyst bed due to excessive oxygen content, resulting in an emergency shutdown and a single economic loss exceeding 5 million yuan. In the water electrolysis hydrogen production process, trace amounts of oxygen (typically 0.5%-1%) introduced through the electrolyzer diaphragm not only reduce hydrogen purity but may also form explosive gas mixtures during subsequent compression and storage. A certain green hydrogen project experienced a hydrogen storage tank leak due to incomplete deoxygenation, resulting in direct economic losses of 20 million yuan.

[0003] According to relevant industrial standards, the oxygen content in the refined gas from ammonia synthesis must be controlled below 10 cm⁻¹. 3 / m 3 Furthermore, in the process of hydrogen energy storage and transportation, the oxygen content is required to be no more than 0.1 ppm. This places extremely high demands on the performance of deoxygenation catalyst support materials.

[0004] Currently, the most widely used deoxygenation catalyst supports in industry are alumina ceramic spheres. While these supports possess high mechanical strength (compressive strength up to 180 MPa), their specific surface area is generally less than 100 m² due to their typically monopore structure. 2 / g, at high air velocities (e.g., exceeding 10,000 h⁻¹) -1 Under certain conditions, gas diffusion paths are restricted, leading to a decrease in deoxygenation efficiency of over 40%. Furthermore, pure alumina supports are prone to phase transformation in complex environments containing sulfur and water vapor, causing the shedding of supported active components such as palladium and platinum, resulting in a generally short support lifespan. Tracking data shows that the lifespan of traditional alumina ceramic balls in ammonia synthesis units is only about 800 hours, with replacement costs accounting for approximately 35% of equipment maintenance expenses. In the high-temperature and high-humidity water electrolysis hydrogen production environment, the water absorption rate of the alumina support increases from 0.5% to 3%, causing catalyst bed pulverization and further increasing system resistance.

[0005] As a deoxygenation catalyst support, ceramic balls must simultaneously meet three major performance requirements: high mechanical strength to support the reaction bed, large specific surface area to ensure high dispersion of active components, and excellent mass transfer performance to adapt to high space velocity operating conditions. However, existing support materials struggle to achieve an effective balance among these properties, becoming a key bottleneck restricting the development of deoxygenation technology.

[0006] Existing improvement methods still have significant shortcomings: for example, although porous ceramic spheres prepared by spray drying can increase the specific surface area to 200 m², they still have significant limitations. 2 / g, but the mechanical strength is significantly reduced (compressive strength is less than 120MPa), making it difficult to meet the requirements of high-pressure reactors; although the hard template method can construct a multi-level porous structure, the process is complex and costly, which is not conducive to industrial promotion; although single-component doping (such as adding cerium oxide) can improve catalytic activity to a certain extent, it often leads to a decrease in support strength of more than 20%, and cannot achieve synergistic optimization of performance.

[0007] In summary, although deoxygenation catalyst support technology has made some progress, existing materials still cannot fully meet the comprehensive requirements of industrial applications for high strength, high specific surface area, efficient mass transfer, and long lifespan. Therefore, developing a novel composite porous ceramic ball support that can balance mechanical strength, pore structure optimization, and catalytic performance is of great significance for promoting the development of deoxygenation technology. Summary of the Invention

[0008] The purpose of this invention is to provide a composite porous ceramic ball for deoxygenation processes and its preparation method, so as to solve the technical problem that existing deoxygenation catalyst supports are difficult to achieve high mechanical strength, large specific surface area and excellent mass transfer performance.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] The first aspect of this invention provides a composite porous ceramic ball for a deoxidation process, wherein the raw material composition, by mass percentage, includes: 55%-70% alumina, 20%-30% silicon dioxide, 5%-10% cerium oxide, and 3%-8% zirconium oxide; the ceramic ball has a three-level pore structure that extends from the surface to the interior, including: surface pores with a diameter of 50-200 μm, internal mesopores with a diameter of 2-50 nm, and micropores with a diameter of 0.5-2 nm.

[0011] Furthermore, the mass ratio of cerium oxide to zirconium oxide is (1.5-2.5):1.

[0012] Furthermore, the total porosity of the ceramic spheres is 45%-60%, and the specific surface area is ≥300m². 2 / g, crushing strength ≥100N / particle.

[0013] The composite porous ceramic spheres provided by this invention utilize a mullite phase framework formed primarily of alumina and silica to ensure the mechanical strength and structural stability of the carrier at high temperatures. The added cerium oxide, with its oxygen storage-release capability, dynamically regulates the local oxygen concentration during the reaction, promoting the activation and migration of oxygen species, thereby enhancing the deoxidation depth and stability. Zirconia, through a phase transformation toughening mechanism, effectively inhibits microcrack propagation, enhancing the thermal shock resistance of the ceramic spheres and enabling them to adapt to fluctuations in operating conditions. In terms of structural design, the 50-200 μm surface pores serve as the main airflow channels, significantly reducing diffusion resistance at high space velocities. The 2-50 nm internal mesopores provide a highly dispersed loading platform for active components, while the 0.5-2 nm micropores further increase the specific surface area, strengthening the capture and activation capabilities of reactant molecules. These three types of channels are interconnected, achieving a balance between efficient mass transfer and high active site density, overcoming the contradiction inherent in traditional carriers that struggle to balance strength, specific surface area, and mass transfer efficiency.

[0014] A second aspect of this invention provides a method for preparing the aforementioned composite porous ceramic spheres for a deoxidation process, comprising the following steps:

[0015] (1) Disperse alumina powder in a composite treatment solution consisting of ammonium molybdate, citric acid, ethanol and water, stir under ultrasonication, filter, dry and calcine to obtain pretreated alumina;

[0016] (2) The pretreated alumina is mixed with fumed silica, cerium oxide and zirconium oxide in proportion, deionized water and dispersant are added, and the mixture is ball-milled to obtain a slurry;

[0017] (3) Add silica sol and nitric acid to the slurry, adjust the pH value to 3-4, stir to form a sol, then add organic foaming agent and stir to foam;

[0018] (4) Inject the foamed sol into a spherical mold, let it stand for 2-4 hours, demold to obtain a gel blank, dry the gel blank to obtain a ceramic ball blank;

[0019] (5) The ceramic ball blank is sintered in two stages. After sintering, it is cooled to 300-400℃ and steam-treated. After treatment, it is dried to obtain the composite porous ceramic ball.

[0020] Further, the mass percentage of each component in the composite treatment solution in step (1) is: ammonium molybdate 0.5%-1.5%, citric acid 1.0%-2.0%, ethanol 10%-20%, and the remainder water.

[0021] Alumina powder was treated in an aqueous solution composed of ammonium molybdate, citric acid, and ethanol. During subsequent calcination, ammonium molybdate was converted into high-melting-point molybdenum oxide, which distributed at the alumina grain boundaries, inhibiting abnormal grain growth during sintering, refining the microstructure of the ceramic, and thus improving overall mechanical strength. Citric acid, as an organic complexing agent, adsorbed onto the alumina surface, leaving uniformly distributed nanoscale pores after sintering decomposition. These pores interconnected with the macropores formed during subsequent foaming, optimizing pore connectivity. The addition of ethanol reduced the surface tension of the treatment solution, improving its wetting and penetration effects in the powder aggregates, ensuring uniform adhesion of the modifying components. This pretreatment constructed a regulating interfacial layer on the surface of the alumina particles, endowing the final ceramic with superior strength, more uniform pore distribution, and more stable surface properties.

[0022] Furthermore, the calcination temperature in step (1) is 700-900℃, and the calcination time is 1-3 hours.

[0023] Further, the dispersant in step (2) is sodium polyacrylate or sodium hexametaphosphate, and the ball milling time is 2-4 hours.

[0024] Further, the solid content of the silica sol in step (3) is 20-40%, and the amount of silica sol used is 10%-20% of the total mass of alumina, silicon dioxide, cerium oxide, and zirconium oxide; the organic foaming agent is a compound of sodium dodecyl sulfate and ammonium bicarbonate in a mass ratio of 1:(2-4), and the amount of organic foaming agent added is 5%-8% of the total mass of alumina, silicon dioxide, cerium oxide, and zirconium oxide.

[0025] Further, the two-stage heating sintering in step (5) is as follows: first, the temperature is raised to 500-700℃ at a heating rate of 2-5℃ / min and held for 1-2 hours; then the temperature is raised to 1300-1500℃ and held for 3-5 hours.

[0026] Further, the steam treatment in step (5) specifically involves transferring the ceramic balls at 300-400°C to a steam environment with a relative humidity of 80%-95% and treating them at 250-350°C for 0.5-1 hour.

[0027] The post-sintering steam treatment optimizes the pore structure and surface chemistry of the ceramic spheres. When the ceramic spheres are placed in a high-humidity steam environment at 300-400℃, water molecules selectively etch away some of the amorphous silicate phase on the surface, clearing the entrance regions of mesopores and micropores, reducing the risk of pore blockage, and exposing the internal surface area more fully, thereby effectively increasing the loading area of ​​the active component. Simultaneously, this treatment introduces abundant hydroxyl functional groups on the ceramic sphere surface, improving the hydrophilicity of the support. This allows the metal precursor solution to more uniformly wet the support and penetrate deep into the pores during subsequent impregnation and loading of the active component, ultimately resulting in more dispersed and more firmly bonded active metal particles, significantly improving the initial activity and long-term stability of the catalyst.

[0028] The composite porous ceramic spheres of this invention are used as a deoxygenation catalyst support as follows: Palladium-ruthenium bimetallic active components are loaded onto the ceramic sphere support via an impregnation method, with the loading amount of the active components being 1% to 5% of the support mass; the loaded catalyst is then packed into the deoxygenation reactor of a water electrolysis hydrogen production system or a synthetic ammonia feed gas pretreatment system; the operation is carried out at a temperature of 150-300℃, a system pressure of 0.1-3 MPa, and a gas space velocity of 5000-20000 h⁻¹. -1 Under the specified process conditions, a feed gas containing 0.5%-1% oxygen is passed through the catalyst bed to complete the deoxygenation process.

[0029] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0030] 1. By forming a mullite phase in an alumina-silica matrix to enhance mechanical strength, improving catalytic activity through the oxygen storage capacity of cerium oxide, and improving thermal shock resistance through phase transformation toughening of zirconium oxide, the functional complementarity and synergistic enhancement of the material composition are achieved.

[0031] 2. A three-level pore system consisting of surface through-pores, internal mesopores, and micropores was constructed, which effectively balances gas diffusion efficiency at high space velocities with active site loading at high specific surface areas, thus resolving the contradiction between mass transfer and specific surface area in traditional carriers.

[0032] 3. A special process combining pretreatment with composite liquid and posttreatment with controllable steam significantly improves the strength uniformity, pore connectivity and surface wettability of the carrier, thereby enhancing the dispersibility and stability of the active components and extending the service life of the catalyst.

[0033] 4. The ceramic ball maintains excellent performance under harsh conditions such as high temperature, high pressure, and high air velocity, and has good prospects for industrial application and economic benefits. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Unless otherwise specified, all raw materials used in the embodiments are commercially available products. The following sources are for illustrative purposes only:

[0036] Alumina was purchased from Aluminum Corporation of China Limited, with an average particle size of approximately 3-4 μm; fumed silica was purchased from Guangzhou Jibisheng Technology Co., Ltd., with an average particle size of approximately 80 nm; cerium oxide was purchased from Zibo Yujing New Materials Co., Ltd., with an average particle size ≤1.0 μm; zirconium oxide was purchased from Shanghai Yuejiang Titanium Dioxide Chemical Products Co., Ltd., with an average particle size of approximately 0.8 μm; sodium polyacrylate was purchased from Henan Xinghan Biotechnology Co., Ltd., with a molecular weight of 2000-5000; and silica sol was purchased from Qingdao Haiyang Chemical Co., Ltd., with a solid content of 30%.

[0037] Example 1

[0038] This embodiment provides a composite porous ceramic ball for the deoxidation process, whose raw material composition by mass percentage includes: 60% alumina, 25% silicon dioxide, 10% cerium oxide, and 5% zirconium oxide.

[0039] The method for preparing the composite porous ceramic spheres includes the following steps:

[0040] (1) Raw material pretreatment and modification: 600 g of alumina powder was weighed and dispersed in a composite treatment solution consisting of ammonium molybdate (1.0% by mass), citric acid (1.5% by mass), ethanol (15% by volume), and the remainder deionized water. The solution was ultrasonically stirred at 60 °C for 1.5 hours, then filtered and dried at 110 °C. The dried powder was calcined at 800 °C for 2 hours to obtain pretreated alumina.

[0041] (2) Slurry preparation: The pretreated alumina was mixed with 250 g of fumed silica, 100 g of cerium oxide powder and 50 g of zirconium oxide powder. 1000 mL of deionized water and 20 g of sodium polyacrylate (dispersant) were added, and the mixture was ball-milled for 3 hours to obtain a uniform slurry with a particle size of about 0.8 μm.

[0042] (3) Sol-gel and foaming: Add 150 g of silica sol with a solid content of 30% to the slurry, and adjust the pH to 3.5 by adding nitric acid dropwise. Stir at 70°C for 1.5 hours to form a stable sol. Then add 60 g of organic foaming agent (a mixture of sodium dodecyl sulfate and ammonium bicarbonate in a mass ratio of 1:3) and stir until foaming is uniform.

[0043] (4) Molding and drying: The foamed sol is injected into a spherical mold with a diameter of 5 mm and allowed to stand at 50°C for 3 hours to complete gelation. After demolding, the gelled preform is placed in a vacuum drying oven at 80°C and dried for 20 hours to obtain the ceramic ball preform.

[0044] (5) Sintering and Steam Post-treatment: The ceramic ball blanks were placed in a muffle furnace and heated to 600℃ at a rate of 3℃ / min and held for 1 hour to remove organic matter. Then, the temperature was increased to 1400℃ and held for 4 hours for high-temperature sintering. After sintering, the blanks were cooled to 350℃ in the furnace and immediately transferred to a steam environment with a relative humidity of 90% for 0.8 hours at 300℃. After treatment, the blanks were dried to obtain composite porous ceramic balls.

[0045] Example 2

[0046] This embodiment provides a composite porous ceramic ball for deoxidation process, whose raw material composition by mass percentage includes: 70% alumina, 20% silicon dioxide, 6% cerium oxide, and 4% zirconium oxide.

[0047] The method for preparing the composite porous ceramic spheres includes the following steps:

[0048] (1) Raw material pretreatment and modification: 700 g of alumina powder was weighed and dispersed in a composite treatment solution consisting of ammonium molybdate (0.8% by mass), citric acid (1.2% by mass), ethanol (12% by volume), and the remainder deionized water. The solution was ultrasonically stirred at 55°C for 2 hours, then filtered and dried at 105°C. The dried powder was calcined at 780°C for 2.5 hours to obtain pretreated alumina.

[0049] (2) Slurry preparation: The pretreated alumina was mixed with 200 g of fumed silica, 60 g of cerium oxide powder and 40 g of zirconium oxide powder. 1000 mL of deionized water and 15 g of sodium hexametaphosphate (dispersant) were added, and the mixture was ball-milled for 2 hours to obtain a uniform slurry with a particle size of about 0.6 μm.

[0050] (3) Sol-gel and foaming: Add 100 g of silica sol with a solid content of 30% to the slurry, and adjust the pH to 3.0 by adding nitric acid dropwise. Stir at 60°C for 2 hours to form a stable sol. Then add 50 g of organic foaming agent (a mixture of sodium dodecyl sulfate and ammonium bicarbonate in a mass ratio of 1:3) and stir to foam.

[0051] (4) Molding and drying: The foamed sol was injected into a spherical mold with a diameter of 8 mm and allowed to stand at 40°C for 4 hours to complete gelation. After demolding, the gelled preform was placed in a vacuum drying oven at 100°C and dried for 12 hours to obtain the ceramic ball preform.

[0052] (5) Sintering and steam post-treatment: The ceramic ball blanks were sintered by programmed temperature rise: the temperature was increased to 600℃ at 5℃ / min and held for 1 hour, then increased to 1500℃ and held for 3 hours. After sintering, the blanks were cooled to 400℃ in the furnace and immediately transferred to a steam environment with a relative humidity of 85% and treated at 350℃ for 0.5 hours. After treatment, the blanks were dried to obtain composite porous ceramic balls.

[0053] Example 3

[0054] This embodiment provides a composite porous ceramic ball for the deoxidation process, whose raw material composition by mass percentage includes: 55% alumina, 28% silicon dioxide, 10% cerium oxide, and 7% zirconium oxide.

[0055] The method for preparing the composite porous ceramic spheres includes the following steps:

[0056] (1) Raw material pretreatment and modification: 550 g of alumina powder was weighed and dispersed in a composite treatment solution consisting of ammonium molybdate (1.2% by mass), citric acid (1.8% by mass), ethanol (18% by volume), and the remainder deionized water. The solution was ultrasonically stirred at 65°C for 1 hour, then filtered and dried at 115°C. The dried powder was calcined at 820°C for 1.5 hours to obtain pretreated alumina.

[0057] (2) Slurry preparation: The pretreated alumina was mixed with 280 g of fumed silica, 100 g of cerium oxide powder and 70 g of zirconium oxide powder. 1200 mL of deionized water and 25 g of sodium polyacrylate (dispersant) were added, and the mixture was ball-milled for 4 hours to obtain a uniform slurry with a particle size of about 0.7 μm.

[0058] (3) Sol-gel and foaming: Add 180 g of silica sol with a solid content of 30% to the slurry, and adjust the pH to 4.0 by adding nitric acid dropwise. Stir at 80°C for 1 hour to form a stable sol. Then add 70 g of organic foaming agent (a mixture of sodium dodecyl sulfate and ammonium bicarbonate in a mass ratio of 1:3), and stir at high speed for 15 minutes until foaming is uniform.

[0059] (4) Molding and drying: The foamed sol was injected into a spherical mold with a diameter of 6 mm and allowed to stand at 60°C for 2 hours to complete gelation. After demolding, the gelled preform was placed in a vacuum drying oven at 90°C and dried for 18 hours to obtain the ceramic ball preform.

[0060] (5) Sintering and steam post-treatment: The ceramic ball blanks were sintered by programmed temperature rise: the temperature was increased to 600℃ at 2℃ / min and held for 1 hour, then increased to 1350℃ and held for 5 hours. After sintering, the blanks were cooled to 300℃ in the furnace and immediately transferred to a steam environment with a relative humidity of 95% and treated at 250℃ for 1 hour. After treatment, the blanks were dried to obtain composite porous ceramic balls.

[0061] Example 4

[0062] This embodiment provides a composite porous ceramic ball for the deoxidation process, whose raw material composition by mass percentage includes: 65% alumina, 22% silicon dioxide, 8% cerium oxide, and 5% zirconium oxide.

[0063] The method for preparing the composite porous ceramic spheres includes the following steps:

[0064] (1) Raw material pretreatment and modification: 650 g of alumina powder was weighed and dispersed in a composite treatment solution consisting of ammonium molybdate (0.5% by mass), citric acid (1.0% by mass), ethanol (10% by volume), and the remainder deionized water. The solution was ultrasonically stirred at 70 °C for 1 hour, then filtered and dried at 120 °C. The dried powder was calcined at 750 °C for 3 hours to obtain pretreated alumina.

[0065] (2) Slurry preparation: The pretreated alumina was mixed with 220 g of fumed silica, 80 g of cerium oxide powder and 50 g of zirconium oxide powder. 1100 mL of deionized water and 20 g of sodium hexametaphosphate (dispersant) were added, and the mixture was ball-milled for 3 hours to obtain a uniform slurry with a particle size of about 0.5 μm.

[0066] (3) Sol-gel and foaming: Add 120 g of silica sol with a solid content of 30% to the slurry, and adjust the pH to 3.2 by adding nitric acid dropwise. Stir at 75°C for 1.2 hours to form a stable sol. Then add 55 g of organic foaming agent (a mixture of sodium dodecyl sulfate and ammonium bicarbonate in a mass ratio of 1:3), and stir until the foaming system is stable.

[0067] (4) Molding and drying: The foamed sol was injected into a spherical mold with a diameter of 4 mm and allowed to stand at 55°C for 2.5 hours to complete gelation. After demolding, the gelled preform was placed in a vacuum drying oven at 85°C and dried for 16 hours to obtain the ceramic ball preform.

[0068] (5) Sintering and steam post-treatment: The ceramic ball blanks were sintered by programmed temperature rise: the temperature was increased to 600℃ at 4℃ / min and held for 1 hour, then increased to 1450℃ and held for 3.5 hours. After sintering, the blanks were cooled to 380℃ in the furnace and immediately transferred to a steam environment with a relative humidity of 80% and treated at 280℃ for 0.7 hours. After treatment, the blanks were dried to obtain composite porous ceramic balls.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is that the raw material composition of the composite porous ceramic balls includes: 55% alumina, 35% silicon dioxide, 3% cerium oxide, and 7% zirconium oxide.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that the raw material composition of the composite porous ceramic balls includes: 60% alumina, 25% silicon dioxide, 10% magnesium oxide, and 5% zirconium oxide.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that the composition and mass percentage of the composite treatment solution in step (1) are: ammonium molybdate 3.0%, citric acid 0.5%, ethanol 15% and the remainder deionized water.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 1 is that the composite treatment solution in step (1) is replaced with a citric acid aqueous solution with a mass fraction of 1.5%.

[0077] Comparative Example 5

[0078] The difference between this comparative example and Example 1 is that step (5) does not involve steam treatment, and composite porous ceramic balls are obtained after high-temperature sintering.

[0079] Comparative Example 6

[0080] The difference between this comparative example and Example 1 is that after sintering in step (5), the ceramic balls were cooled to room temperature in the furnace, and then transferred to a steam environment with a relative humidity of 90% for 2 hours at room temperature. After treatment, they were dried to obtain composite porous ceramic balls.

[0081] Performance testing

[0082] Test samples: Composite porous ceramic balls prepared in Examples 1-4 and Comparative Examples 1-6.

[0083] Test method:

[0084] 1. Specific surface area and porosity: The specific surface area of ​​the ceramic ball powder was determined by nitrogen adsorption-desorption method (BET method), and its pore size distribution and total porosity were determined by mercury porosimetry.

[0085] 2. Mechanical strength: 30 ceramic balls with a diameter of 5 mm were randomly selected and their crush resistance was measured using a universal testing machine. The average value was taken.

[0086] 3. Deoxidation performance: All ceramic ball samples were loaded with equal volumes in a micro fixed-bed reactor, and 3.0% palladium-ruthenium (Pd:Ru = 4:1) active component was loaded using an equal-volume impregnation method. The reactor was tested at 200℃, 0.5 MPa, and a space velocity of 10000 h⁻¹. -1Under these conditions, a deoxygenation test was conducted on a nitrogen-hydrogen mixture (simulating hydrogen production feed gas) with an initial oxygen content of 0.8%. The outlet oxygen concentration during stable operation was recorded as an indicator of deoxygenation depth, and continuous operation was performed to examine its lifespan (with the outlet oxygen concentration rising above 0.1 ppm as the end of the lifespan).

[0087] The test results are shown in Table 1.

[0088] Table 1 Performance Test Results

[0089]

[0090]

[0091] The performance test results above show that the ceramic balls prepared within the raw material ratios and process parameters determined in this invention exhibit a series of excellent and balanced properties. The specific surface area of ​​all embodiments remains stable at 290-320 m². 2 The samples exhibit a high specific surface area and high mechanical strength, with crush resistance reaching or exceeding 100 N / particle. In terms of deoxygenation performance, all four examples effectively reduced the outlet oxygen concentration to below 0.1 ppm, and showed minimal activity decay after 2000 hours of continuous operation, indicating excellent initial activity and an exceptionally long operating life.

[0092] In Comparative Example 1, the low cerium oxide content resulted in insufficient oxygen storage-release capacity, leading to a poor deoxidation depth. Simultaneously, the excessive silica content may have affected the quality of mullite phase formation, causing a decrease in strength. This component imbalance ultimately resulted in poor catalyst stability and a shortened lifespan. In Comparative Example 2, the magnesium oxide lacked the ability to dynamically regulate oxygen concentration, severely impacting the catalyst's deoxidation depth. In Comparative Example 3, the excessively high ammonium molybdate and low citric acid ratios caused the treatment solution to form an excessively thick or unevenly distributed modification layer on the alumina surface, potentially leading to stress concentration or blockage of some pores during sintering. In Comparative Example 4, while citric acid treatment created pores, it completely lacked the grain boundary strengthening effect of ammonium molybdate, resulting in severely insufficient strength of the ceramic ball skeleton. In Comparative Example 5, the lack of steam post-treatment to unblock pore inlets and achieve surface hydroxylation resulted in some internal pores not being effectively utilized, leading to a low specific surface area. The uniformity and binding strength of the active component loading were affected, resulting in poor initial deoxygenation depth. Furthermore, with prolonged operation, the pores were more prone to failure due to slight blockage, leading to a shorter lifespan. Comparative Example 6, with room temperature steam treatment, could not provide sufficient energy for effective chemical reactions between water molecules and the amorphous phase on the ceramic ball surface. The treatment effect was limited to physical adsorption of water, with almost no optimization of pore and surface properties, demonstrating that steam post-treatment requires specific temperature conditions to be effective.

[0093] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite porous ceramic ball for deoxidation processes, comprising, by mass percentage: Alumina 55%-70%, silicon dioxide 20%-30%, cerium oxide 5%-10%, zirconium oxide 3%-8%; The ceramic ball has a three-level pore structure that extends from the surface to the interior, including: surface pores with a diameter of 50-200 μm, internal mesopores with a diameter of 2-50 nm, and micropores with a diameter of 0.5-2 nm.

2. The composite porous ceramic ball according to claim 1, characterized in that, The mass ratio of cerium oxide to zirconium oxide is (1.5-2.5):

1.

3. The composite porous ceramic ball according to claim 1, characterized in that, The total porosity of the ceramic spheres is 45%-60%, and the specific surface area is ≥300 m². 2 / g, crushing strength ≥100N / particle.

4. A method for preparing the composite porous ceramic spheres according to any one of claims 1-3, comprising the following steps: (1) Disperse alumina powder in a composite treatment solution consisting of ammonium molybdate, citric acid, ethanol and water, stir under ultrasonication, filter, dry and calcine to obtain pretreated alumina; (2) The pretreated alumina is mixed with fumed silica, cerium oxide and zirconium oxide in proportion, deionized water and dispersant are added, and the mixture is ball-milled to obtain a slurry; (3) Add silica sol and nitric acid to the slurry, adjust the pH value to 3-4, stir to form a sol, then add organic foaming agent and stir to foam; (4) Inject the foamed sol into a spherical mold, let it stand for 2-4 hours, demold to obtain a gel blank, dry the gel blank to obtain a ceramic ball blank; (5) The ceramic ball blank is sintered in two stages. After sintering, it is cooled to 300-400℃ and steam-treated. After treatment, it is dried to obtain the composite porous ceramic ball.

5. The preparation method according to claim 4, characterized in that, The mass percentage of each component in the composite treatment solution in step (1) is: ammonium molybdate 0.5%-1.5%, citric acid 1.0%-2.0%, ethanol 10%-20%, and the remainder is water.

6. The preparation method according to claim 4, characterized in that, The calcination temperature in step (1) is 700-900℃, and the calcination time is 1-3 hours.

7. The preparation method according to claim 4, characterized in that, The dispersant in step (2) is sodium polyacrylate or sodium hexametaphosphate, and the ball milling time is 2-4 hours.

8. The preparation method according to claim 4, characterized in that, The solid content of the silica sol in step (3) is 20-40%, and the amount of silica sol used is 10%-20% of the total mass of alumina, silicon dioxide, cerium oxide, and zirconium oxide; the organic foaming agent is a compound of sodium dodecyl sulfate and ammonium bicarbonate in a mass ratio of 1:(2-4), and the amount of organic foaming agent added is 5%-8% of the total mass of alumina, silicon dioxide, cerium oxide, and zirconium oxide.

9. The preparation method according to claim 4, characterized in that, The two-stage heating sintering in step (5) is as follows: First, the temperature is raised to 500-700℃ at a heating rate of 2-5℃ / min and held for 1-2 hours; then the temperature is raised to 1300-1500℃ and held for 3-5 hours.

10. The preparation method according to claim 4, characterized in that, The steam treatment in step (5) specifically involves transferring the ceramic balls at 300-400℃ to a steam environment with a relative humidity of 80%-95% and treating them at 250-350℃ for 0.5-1 hours.

Images