Preparation method and application of mesoporous silicate-based monatomic catalyst and derivative porous ceramic thereof

Abstract

The invention discloses a mesoporous silicate-based monatomic catalyst and a preparation method and application of porous ceramic of a derivative of the mesoporous silicate-based monatomic catalyst. According to the method disclosed by the invention, on the basis of the structural advantages of layered silicate, a high-density and uniformly dispersed monatomic active center precursor is firstly constructed on the surface of the layered silicate through a two-step strategy of anchoring and ceramization, and then the layered silicate is converted into the monolithic catalyst with a stable ceramic skeleton and a hierarchical porous structure through molding and controllable sintering. According to the method provided by the invention, an extremely strong range limiting effect is provided for metal single atoms, migration and agglomeration at high temperature and in the use process are effectively prevented, the leaching rate of cobalt is reduced, the stability of the catalyst is remarkably improved, and the service life of the catalyst is prolonged. Besides, the method can also be used for preparing catalytic particles or devices with determined macroscopic shapes and sizes, and the catalytic particles or devices can be directly put into fluidized beds, microreactors and other devices for use, so that the catalyst is stable and easy to reuse.

Description

Preparation method and application of a mesoporous silicate-based single-atom catalyst and its derivative porous ceramics Technical Field

[0001] This invention relates to the field of heterogeneous catalytic materials and porous ceramic materials, specifically to a method for preparing a mesoporous silicate-based single-atom catalyst and its derivative porous ceramics, and their applications. Background Technology

[0002] Single-atom catalysts, with their high atom utilization rate and highly dispersed, uniform, and unique active sites, have shown great potential in energy conversion, environmental protection, and chemical catalysis. However, achieving controllable and low-cost synthesis of high-density single-atom catalysts remains a key challenge restricting their widespread application. Furthermore, the interaction between conventional supports (such as metal oxides and carbon materials) and single atoms is sometimes insufficient to prevent leaching, aggregation, and deactivation of single atoms during the reaction process, posing a significant challenge to the stable loading of high-density single atoms.

[0003] Layered silicates, with their unique layered structure and abundant surface hydroxyl groups, provide ideal active sites for anchoring metal single atoms; simultaneously, their silicate framework can be further transformed into a ceramic phase at high temperatures. Layered silicates (such as montmorillonite, kaolinite, and talc) are abundant in nature, and through artificial synthesis, not only can multiphase composites be achieved, but functional materials with specific mesoporous structures can also be obtained through process control. These mesoporous structures help expose more active sites, promote reactant diffusion, and provide more ample loading and catalytic space. However, layered silicate powders and their supported single-atom catalysts generally suffer from problems such as poor sedimentation, easy loss, and difficulty in filtration and separation in liquid-phase reactions, which restricts their large-scale application. Therefore, constructing them into macroscopic materials is one of the key paths to achieving industrial-scale promotion.

[0004] Macroporous ceramics, due to their high porosity, low density, high specific surface area, excellent thermal stability and mechanical strength, as well as their open mesoporous structure, have shown potential as structured catalyst supports in continuous flow reaction systems. However, current research on the effective integration of high-density, high-stability single-atom catalysts with macroporous ceramics remains relatively limited.

[0005] Therefore, developing a method for preparing ceramic catalytic materials that can stably immobilize high-density single atoms and further construct them into macroscopic porous structures and can be used directly is of great scientific significance and industrial application value. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art by providing a method for preparing mesoporous silicate-based single-atom catalysts and their derivative porous ceramics, as well as their applications.

[0007] The present invention discloses a method for preparing a mesoporous silicate-based single-atom catalyst and its derivative porous ceramics, comprising the following steps: (1) dissolving hexadecyltrimethylammonium bromide (CTAB) in a mixed solvent of deionized water and anhydrous ethanol, adding an alkaline substance and stirring for 1-2 hours until the solution is clear, then adding 1,3,5-trimethylbenzene (TMB) and stirring for 30-60 minutes to form a homogeneous system; subsequently adding tetraethyl silicate (TEOS) and continuing to stir for 30-60 minutes to obtain a mixed solution.

[0008] (2) Add magnesium salt and soluble salt of target metal to the mixture obtained in step (1) and stir continuously for 20-24 hours to obtain a mixture; in this step, magnesium ions react with tetraethyl silicate to generate hydrated magnesium silicate precursor, and target metal ions react with tetraethyl silicate to generate corresponding hydrated metal silicate precursor.

[0009] (3) The mixture obtained in step (2) is transferred to a hydrothermal reactor and crystallized at 80-100°C for 24-28 hours to obtain a crystallized product. After cooling, filtering, washing with deionized water and anhydrous ethanol, the product is dried at 80-100°C for 8-24 hours to obtain an uncalcined mesoporous silicate-based single-atom catalyst precursor. In this step, the hydrated magnesium silicate precursor obtained above undergoes preliminary Mg–O–Si bonding to form hydrated magnesium silicate, and the hydrated metal silicate precursor undergoes preliminary M–O–Si (M is the target metal) bonding.

[0010] (4) The precursor obtained in step (3) is calcined in static air at 500-600°C for 4-5 hours to obtain silicate-supported single-atom catalyst powder with mesoporous structure, namely mesoporous silicate-based single-atom catalyst.

[0011] Further, (5) the precursor obtained in step (3) or the catalyst powder obtained in step (4) is mixed with binder, pore-forming agent, dispersant and deionized water to obtain a uniform slurry or plastic clay; the uniform slurry is dropped into sodium alginate aqueous solution, or the plastic clay is extruded or 3D printed to obtain a preform; the preform is slowly heated from room temperature to 200-400℃, and then sintered at 500-600℃ for 3-5 hours to obtain a macroscopic porous ceramic catalyst material.

[0012] Furthermore, in step (1), the mass-to-volume ratio of hexadecyltrimethylammonium bromide to deionized water and anhydrous ethanol is 1 g: 20-30 mL: 20-30 mL, and the mass ratio of hexadecyltrimethylammonium bromide to 1,3,5-trimethylbenzene and tetraethyl silicate is 1: 0.5-0.7: 2-2.5.

[0013] Furthermore, in step (1), the alkaline substance is ammonia or urea, and the mass concentration of the ammonia is 25-28%.

[0014] Furthermore, in step (1), the mass-to-volume ratio of hexadecyltrimethylammonium bromide to ammonia is 1 g: 20-25 mL, and the mass-to-volume ratio of hexadecyltrimethylammonium bromide to urea is 1: 5-7.

[0015] Furthermore, in step (2), the magnesium salt is magnesium nitrate hexahydrate or magnesium chloride, and the soluble salt of the target metal is a nitrate or chloride salt of cobalt, copper, iron, platinum, palladium or ruthenium.

[0016] Furthermore, in step (2), the mass ratio of the magnesium salt, the soluble salt of the target metal, and the tetraethyl silicate in step (1) is 1.1-1.5:0.22-0.30:1.

[0017] Furthermore, in step (5), the binder is aluminum dihydrogen phosphate, the pore-forming agent is sodium carboxymethyl cellulose, and the dispersing agent is polyethylene glycol 400.

[0018] Furthermore, in step (5), the mass ratio of the binder, dispersant, pore-forming agent, deionized water to the precursor obtained in step (3) or the catalyst powder obtained in step (4) is 1.5-2:0.02-0.03:0.05-0.06:3-6:1.

[0019] Furthermore, in step (5), the mass concentration of the sodium alginate aqueous solution is 1-2%.

[0020] Furthermore, in step (5), the temperature is increased from room temperature to 200-400°C at a rate of 1-2°C / min.

[0021] The present invention also discloses the application of porous ceramics prepared by the above method in fluidized beds and microreactors.

[0022] The beneficial effects of the present invention are as follows: (1) The abundant anchoring points of mesoporous silicate and the stable ceramic matrix formed after sintering provide a strong confinement effect for metal single atoms, effectively preventing migration and agglomeration at high temperature and during use, reducing the leaching rate of cobalt, significantly improving the stability of the catalyst, and extending the service life of the catalyst.

[0023] (2) The mesoporous silicate-based single-atom catalyst prepared by the present invention has a high specific surface area and micro-mesopores (providing high specific surface area and dispersion of active sites), ensuring efficient diffusion of reactants / products and improving overall catalytic efficiency.

[0024] (3) The hydrated magnesium silicate synthesized by the method of the present invention provides abundant sites for anchoring single atoms. At the same time, the synergistic use of each raw material avoids the polymerization and crystallization of cobalt in the alkaline system, thus maintaining its highly dispersed and highly active state. High-temperature calcination further enhances the stability of the bond between hydrated magnesium silicate and single-atom cobalt.

[0025] (4) The method of the present invention can prepare catalytic particles or devices with a defined macroscopic shape and size, which can be directly placed into fluidized beds, microreactors and other devices, thus achieving catalyst stability and easy reusability.

[0026] (5) The preparation process of this invention does not require complex equipment. The composite of hydrated magnesium silicate and target single atom can be achieved in one step. The calcination temperature and sintering temperature are both low, no solid waste is generated, the raw materials are cheap and readily available, and it has good feasibility for large-scale production, which is in line with the concept of green manufacturing.

[0027] (6) By adjusting the ratio of magnesium salt and the soluble salt of the target metal, as well as the calcination temperature, this invention can flexibly control the chemical composition and catalytic performance of the final material, adapting to the needs of different catalytic reaction systems. The use of magnesium salt can improve the specific surface area of ​​mesoporous silicate-based single-atom catalysts and reduce harmful ions (such as Co). 2+ Leaching played a crucial role.

[0028] (7) As an inorganic ceramic binder, aluminum dihydrogen phosphate contains aluminum ions that can both initiate sodium alginate gelation, promote the formation of porous ceramic blanks, and promote the high-temperature sintering of porous ceramics. Attached Figure Description

[0029] Figure 1 is the XRD pattern of the catalyst prepared in Example 1; Figure 2 is the XRD pattern of the catalyst prepared in Example 2; Figure 3 is the XRD pattern of the catalyst precursor prepared in Comparative Example 1; Figure 4 is the XRD pattern of the catalyst prepared in Comparative Example 2; Figure 5 is the XRD pattern of the catalyst prepared in Comparative Example 4; Figure 6 is the XRD pattern of the catalyst prepared in Comparative Example 7; Figure 7 is the transmission electron microscope and EDS image of the catalyst prepared in Example 1; Figure 8 is the high-angle annular dark-field image-scanning transmission electron microscope image of the catalyst prepared in Example 1; Figures 9a and 9b are schematic diagrams of the porous ceramic wet blank and the calcined porous ceramsite prepared in Example 4, respectively. Detailed Implementation

[0030] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] Example 1 (1) 1.0 g CTAB was dissolved in a mixed solvent of 20 mL deionized water and 30 mL anhydrous ethanol. About 23 mL ammonia was added, and the mixture was magnetically stirred at room temperature for 2 h until CTAB was completely dissolved and the solution was clear. Then 0.67 g TMB was added, and the mixture was stirred for 30 min to form a homogeneous system. Subsequently, 2.0 g TEOS was added, and the mixture was stirred for 30 min to perform preliminary hydrolysis and obtain a mixed solution.

[0032] (2) Add 2.30 g Mg(NO3)2·6H2O and 0.443 g Co(NO3)2·6H2O to the mixture obtained in step (1), and stir continuously at room temperature for 20 h to obtain the mixture.

[0033] (3) The mixture obtained in step (2) was transferred to a hydrothermal reactor and crystallized in an oven at 100°C for 24 h to obtain a crystallized product. The product was cooled, filtered, washed with deionized water and anhydrous ethanol, and dried in an oven at 60°C for 8 h to obtain an uncalcined mesoporous silicate-based single-atom catalyst precursor.

[0034] (4) The precursor obtained in step (3) is calcined in static air at 600°C for 5 h (the heating rate is usually 2°C / min) to completely remove the CTAB template agent and obtain a mesoporous silicate-based single-atom catalyst.

[0035] The catalyst prepared in Example 1 was subjected to N2 adsorption-desorption tests, and its BET specific surface area was determined to be 457 m². 2 / g.

[0036] As shown in Figure 1, the XRD pattern of the catalyst prepared in this embodiment shows a peak at 2θ=20°, indicating that the catalyst prepared in this embodiment has an amorphous phase. Characteristic peaks of hydrated magnesium silicate phase appear near 2θ=35° and 59°. This shows that the catalyst does not contain crystalline cobalt or its compound phases, but contains a small amount of hydrated magnesium silicate phase. This indicates that cobalt does not exist as a crystalline phase of cobalt oxide or cobalt silicate. The single atoms are dispersed and smaller than unit cells and grains. The absence of a crystalline phase indirectly indicates that the cobalt particles are very small (existing as single atoms).

[0037] As shown in Figure 7, the catalyst prepared in this embodiment has a uniform distribution of elements such as cobalt and magnesium, without obvious aggregation.

[0038] As shown in Figures 7 and 8, the catalyst prepared in this embodiment does not exhibit crystalline phases such as lattice striations.

[0039] Example 2 The difference between this example and Example 1 is that the calcination temperature in step (4) is changed to 500℃, while the other conditions are the same as in Example 1.

[0040] As shown in Figure 2, the XRD pattern of the catalyst 500-meso-CoMg prepared in this embodiment shows that there is a peak at 2θ=20°, indicating that the catalyst prepared in this embodiment has an amorphous phase. Characteristic peaks of hydrated magnesium silicate phase appear near 2θ=35° and 59°, indicating that the catalyst does not contain crystalline cobalt and its compound phases, but contains a small amount of hydrated magnesium silicate phase.

[0041] Example 3 The difference between this example and Example 1 is that the crystallization reaction temperature in step (3) is changed to 80°C, while the other conditions are the same as in Example 1.

[0042] Example 4 (1) 1.2g of the uncalcined mesoporous silicate-based single-atom catalyst precursor prepared in step (3) of Example 1 was mixed with 2g of aluminum dihydrogen phosphate, 6g of deionized water, 0.03g of polyethylene glycol 400 and 0.06g of sodium carboxymethyl cellulose and stirred gently to obtain a uniform slurry.

[0043] (2) Dissolve 1.5g of sodium alginate in 98.5g of deionized water to prepare a sodium alginate aqueous solution with a mass concentration of 1.5%. The uniform slurry obtained in step (1) is added dropwise to the sodium alginate aqueous solution using the drop-gel method to obtain a porous ceramic wet blank. After drying in an oven at 60-80℃ for 8 h, the temperature is slowly raised from room temperature to 300℃ (heating rate of 1℃ / min) to remove organic matter and form initial pores. Then, it is sintered at 600℃ for 3.5 h (heating rate of about 2℃ / min) to obtain calcined porous ceramic particles.

[0044] In the above reaction process, aluminum dihydrogen phosphate first undergoes a dehydration condensation reaction to form chain-like or network-like inorganic polymers, which initially bind the catalyst precursor particles and give the green body a certain strength. As the calcination temperature increases, aluminum dihydrogen phosphate activates the silicon dioxide component through the generated silicon pyrophosphate, and then generates aluminum phosphate that is highly compatible with the silicon dioxide crystal structure at high temperature, thereby firmly binding the entire system together through chemical bonds.

[0045] As shown in Figures 9a and 9b, the porous ceramic wet blanks and porous ceramsite prepared in this embodiment have an appearance and morphology similar to microspheres.

[0046] Example 5 The difference between this example and Example 1 is that the ammonia in step (1) is replaced with 6g of urea, and the other conditions are the same as in Example 1.

[0047] The difference between Comparative Example 1 and Example 1 is that step (4) is omitted, that is, calcination is not performed, and the other conditions are the same as those in Example 1.

[0048] As shown in Figure 3, the XRD pattern of the catalyst prepared in this comparative example shows a peak at 2θ=20°, indicating that the catalyst prepared in this comparative example has an amorphous phase. Characteristic peaks of hydrated magnesium silicate phase appear near 2θ=35° and 59°, indicating that the catalyst does not contain crystalline cobalt and its compounds. Compared with Examples 1 and 2, this catalyst contains obvious hydrated magnesium silicate phase.

[0049] The difference between Comparative Example 2 and Example 1 is that the calcination temperature in step (4) is changed to 400°C, while the other conditions are the same as in Example 1.

[0050] As shown in Figure 4, the XRD pattern of the catalyst prepared in this comparative example shows a peak at 2θ = 20°, indicating the presence of an amorphous phase. Characteristic peaks of hydrated magnesium silicate phase appear near 2θ = 35° and 59°, indicating that the catalyst does not contain crystalline cobalt or its compounds. Compared to Examples 1 and 2, this catalyst contains a significant hydrated magnesium silicate phase, indicating that the X-ray diffraction peak intensity of hydrated magnesium silicate gradually decreases with increasing calcination temperature. This suggests that this phase decomposes or transforms into other phases at high temperatures, potentially generating new substances that contribute to the stabilization of Co single atoms.

[0051] The difference between Comparative Example 3 and Example 1 is that Co(NO3)2·6H2O in step (2) is replaced with Ni(NO3)2·6H2O, while the other conditions are the same as in Example 1.

[0052] The difference between Comparative Example 4 and Example 1 is that Mg(NO3)2·6H2O is not added in step (2), while the other conditions are the same as in Example 1.

[0053] As shown in Figure 5, the XRD pattern of the catalyst prepared in this comparative example shows a peak at 2θ=20°, indicating that the catalyst prepared in this comparative example has an amorphous phase. This shows that the catalyst does not contain crystalline cobalt and its compounds, nor does it contain hydrated magnesium silicate.

[0054] The catalyst prepared in this comparative example was subjected to N2 adsorption-desorption tests, and its BET specific surface area was measured to be 43 m². 2 / g, compared with Example 1, the specific surface area of ​​the sample prepared in Comparative Example 4 decreased significantly, indicating that hydrated magnesium silicate plays an important role in increasing the specific surface area of ​​the sample.

[0055] The difference between Comparative Example 5 and Example 1 is that the template agent CTAB in step (1) is replaced with the block copolymer P123(EO). 20 PO 70 EO 20The remaining conditions are the same as in Example 1.

[0056] The difference between Comparative Example 6 and Example 1 is that no pore-expanding agent TMB is added in step (1), while the other conditions are the same as in Example 1.

[0057] The difference between Comparative Example 7 and Example 1 is that Co(NO3)2·6H2O is not added in step (2), while the other conditions are the same as in Example 1.

[0058] As shown in Figure 6, the XRD pattern of the catalyst prepared in this comparative example shows that the catalyst does not contain crystalline cobalt or its compounds, but contains hydrated magnesium silicate.

[0059] The catalyst prepared in this comparative example was subjected to N2 adsorption-desorption tests, and its BET specific surface area was determined to be 353 m². 2 / g. Compared with the catalyst prepared in Example 9, this demonstrates that the catalyst prepared using only a magnesium source can have a higher specific surface area.

[0060] To evaluate the catalytic performance, microstructure, composition, and specific surface area of ​​the mesoporous silicate-based single-atom catalysts prepared in the above examples and comparative examples, the following tests were conducted: (1) Degradation experiment of the mesoporous silicate-based single-atom catalyst: To evaluate its catalytic performance, 25 mg of the catalyst sample and 25 mg of potassium persulfate (PMS) were added to 50 mL of 20 mg / L 5-fluorouracil solution and stirred. Samples were taken at 10 min or 30 min after the start of the reaction to detect the degradation rate of the target substance. Finally, after the degradation reaction, the solution was filtered through a microporous membrane, and the concentration of cobalt ions in the solution was tested to compare the leaching of cobalt in the catalyst.

[0061] (2) Degradation experiment of the derived porous ceramic particles: The catalytic performance of the derived porous ceramic particles was evaluated by a similar method: 0.5 g of porous ceramic particle sample from Example 4 and 12.5 mg of potassium persulfate (PMS) were added to 25 mL of 5-fluorouracil solution with a concentration of 20 mg / L and stirred. The degradation rate was detected at 30 min.

[0062] (3) Sample characterization: X-ray diffractometer, high-resolution transmission electron microscope, X-ray energy dispersive spectroscopy and nitrogen adsorption surface area tester were used to characterize and analyze the microstructure and morphology of the prepared samples.

[0063] Table 1 Comparison of Sample Degradation Performance and Co Leaching Performance Table 2 Comparison of Sample Degradation Performance As shown in Table 1, compared with Example 1, Comparative Example 1 was not calcined, and the catalyst precursor prepared in Comparative Example 1 had poor degradation performance and a high Co leaching concentration (2.33 mg / L), which could lead to secondary pollution of water by cobalt ions. The catalyst prepared in Example 1 achieved 97% degradation of pollutants in 10 minutes, and after extending the time to 30 minutes, the degradation rate was 98%, indicating that the degradation rate of the catalyst slows down when the pollutant concentration becomes lower.

[0064] The catalyst prepared in Example 1, after being reused 4 times, still had a degradation rate of 95% after 30 minutes of degradation. Compared with the first time (98% degradation rate at 30 minutes), the catalytic performance decline was not significant.

[0065] Compared with Example 1, the degradation rates of the catalysts prepared in Comparative Examples 2 and 4 were lower than those in Example 1 after 30 min of degradation. Furthermore, the leaching levels of Co ions in the degraded solutions were higher than the limit (1 mg / L) specified in the Surface Water Environmental Quality Standard (GB 3838-2002). This indicates that hydrated magnesium silicate can help anchor Co single atoms, and the degree of stabilization of Co single atoms varies with the calcination temperature. High Co ion leaching levels can also easily lead to secondary pollution problems caused by harmful cobalt ions.

[0066] As shown in Table 2, the catalysts prepared in Examples 3, 4 and 5 all showed higher degradation rates at 30 min than those in Comparative Examples 3, 5, 6 and 7, demonstrating certain advantages.

[0067] Compared with Example 1, the crystallization reaction temperature of Example 3 was lower, and the degradation rate of the catalyst obtained in Example 3 decreased slightly at 30 min. This indicates that lowering the crystallization reaction temperature will slightly weaken the catalytic performance of the catalyst. The main reason is that lowering the crystallization reaction temperature will lead to a decrease in the crystal order of the porous silicate-based single-atom catalyst precursor, which will affect the dispersion of metal single atoms.

[0068] Compared to Example 1, Example 4, where the catalyst was shaped and sintered into ceramic particles, showed a slight decrease in degradation rate after 30 minutes. This indicates that while the catalytic performance of the powdered catalyst is somewhat affected by the shaping process, the decrease is relatively small.

[0069] Compared to Example 1, Example 5 used urea as a pH adjuster, and the degradation rate of the resulting catalyst decreased slightly after 30 minutes. This indicates that ammonia can be replaced by urea in the synthesis process, but using ammonia as a pH adjuster yields better results.

[0070] Compared with Example 1, the catalyst prepared in Comparative Example 3 showed a significant decrease in catalytic performance at 30 min, indicating that the effect of introducing Ni / Mg source in catalyst synthesis is not as good as that of Co / Mg source.

[0071] Compared with Example 1, Comparative Example 5 changed the template agent, and the catalyst prepared by it showed a decrease in catalytic performance at 30 min, indicating that the sample with added template agent had better catalytic performance.

[0072] Compared with Example 1, Comparative Example 6 did not use a pore expander, and the catalyst prepared there showed a decrease in catalytic performance after 30 min, indicating that the sample with the pore expander had better catalytic performance.

[0073] Compared with Example 1, Comparative Example 7 did not use a cobalt source, and the catalyst prepared there showed a significant decrease in catalytic performance after 30 min, indicating that cobalt single atoms play a key role in improving catalytic performance.

[0074] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a mesoporous silicate-based single-atom catalyst, characterized in that, Includes the following steps: (1) Dissolve hexadecyltrimethylammonium bromide in a mixed solvent of deionized water and anhydrous ethanol, add an alkaline substance and stir for 1-2 hours until the solution is clear, then add 1,3,5-trimethylbenzene and stir for 30-60 minutes to form a homogeneous system; then add tetraethyl silicate and continue stirring for 30-60 minutes to obtain a mixture; (2) Add magnesium salt and soluble salt of the target metal to the mixture obtained in step (1) and continue stirring for 20-24 hours to obtain a mixture; (3) Add the mixture obtained in step (2) The compound is transferred into a hydrothermal reactor and crystallized at 80-100°C for 24-28 hours to obtain a crystallized product. After cooling, filtering, washing with deionized water and anhydrous ethanol, the product is dried at 80-100°C for 8-24 hours to obtain an uncalcined mesoporous silicate-based single-atom catalyst precursor. (4) The precursor obtained in step (3) is calcined in static air at 500-600°C for 4-5 hours to obtain silicate-supported single-atom catalyst powder with a mesoporous structure, i.e., mesoporous silicate-based single-atom catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of hexadecyltrimethylammonium bromide to deionized water and anhydrous ethanol is 1 g: 20-30 mL: 20-30 mL, and the mass ratio of hexadecyltrimethylammonium bromide to 1,3,5-trimethylbenzene and tetraethyl silicate is 1: 0.5-0.7: 2-2.

5.

3. The preparation method according to claim 1, characterized in that, In step (1), the alkaline substance is ammonia or urea, and the mass concentration of the ammonia is 25-28%.

4. The preparation method according to claim 1 or 3, characterized in that, In step (1), the mass-to-volume ratio of hexadecyltrimethylammonium bromide to ammonia is 1 g: 20-25 mL, and the mass-to-volume ratio of hexadecyltrimethylammonium bromide to urea is 1: 5-7.

5. The preparation method according to claim 1, characterized in that, In step (2), the magnesium salt is magnesium nitrate hexahydrate or magnesium chloride, and the soluble salt of the target metal is a nitrate or chloride salt of cobalt, copper, iron, platinum, palladium or ruthenium.

6. The preparation method according to claim 1 or 5, characterized in that, In step (2), the mass ratio of the magnesium salt, the soluble salt of the target metal and the tetraethyl silicate in step (1) is 1.1-1.5:0.22-0.30:

1.

7. A method for preparing porous ceramics supported on mesoporous silicate-based single-atom catalysts, characterized in that, The method includes the following steps: (1) Dissolving hexadecyltrimethylammonium bromide in a mixed solvent of deionized water and anhydrous ethanol, adding an alkaline substance and stirring for 1-2 hours until the solution is clear, then adding 1,3,5-trimethylbenzene and stirring for 30-60 minutes to form a homogeneous system; then adding tetraethyl silicate and continuing to stir for 30-60 minutes to obtain a mixture; (2) adding magnesium salt and a soluble salt of the target metal to the mixture obtained in step (1) and continuing to stir for 20-24 hours to obtain a mixture; (3) transferring the mixture obtained in step (2) into a hydrothermal reactor and crystallizing at 80-100°C for 24-28 hours to obtain a crystallized product, which is then cooled, filtered, washed with deionized water and anhydrous ethanol, and dried at 80-100°C. (3) Calcine the precursor obtained in step (3) in static air at 500-600℃ for 4-5 hours to obtain silicate-supported single-atom catalyst powder with mesoporous structure, i.e., mesoporous silicate-based single-atom catalyst; (4) Calcine the precursor obtained in step (3) or the catalyst powder obtained in step (4) with binder, pore-forming agent, dispersant and deionized water to obtain uniform slurry or plastic clay; add the uniform slurry to sodium alginate aqueous solution, or extrude the plastic clay or 3D print it to obtain a preform; slowly heat the preform from room temperature to 200-400℃, and then sinter it at 500-600℃ for 3-5 hours to obtain macroporous ceramic catalyst material.

8. The preparation method according to claim 7, characterized in that, In step (5), the binder is aluminum dihydrogen phosphate, the pore-forming agent is sodium carboxymethyl cellulose, and the dispersing agent is polyethylene glycol 400.

9. The preparation method according to claim 7 or 8, characterized in that, In step (5), the mass concentration of the sodium alginate aqueous solution is 1-2%, and the temperature is increased from room temperature to 200-400℃ at a heating rate of 1-2℃ / min.

10. The application of the porous ceramic prepared according to claims 7-9 in fluidized beds and microreactors.

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