Carbon particle stacked carbon template and application thereof in synthesis of grade porous SAPO-34 molecular sieve single crystal

Abstract

The invention relates to a carbon particle stacked carbon template and application thereof in synthesis of grade porous SAPO-34 molecular sieve single crystals. Firstly, sugar, water, ethanol, ammonia water and the like are used as raw materials, and a carbon particle stacked carbon template is prepared through the steps of hydrothermal crystallization, high-temperature carbonization in a protective atmosphere and the like; then preparing molecular sieve precursor gel by taking an aluminum source, a phosphorus source, a silicon source and a structure-directing agent as raw materials; and finally, uniformly mixing the carbon particle stacked carbon template with the molecular sieve precursor gel, and carrying out aging, hydrothermal crystallization, high-temperature roasting and the like to prepare the grade pore SAPO-34 molecular sieve single crystal with through pore channels. The preparation method solves the common problems of poor controllability, difficult penetration of pore channels and the like in the existing preparation method, and ensures that mesopore and macropore structure pore channels of the grade pore SAPO-34 molecular sieve are communicated and are connected with the outer surfaces of the grade pore SAPO-34 molecular sieve by introducing a carbon particle accumulation carbon template with a novel structure. The method has the remarkable advantages of low cost, high controllability, suitability for large-scale industrial production and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, specifically to the technical field of porous materials, and particularly to a carbon particle-packed carbon template and its application in the synthesis of hierarchical pore SAPO-34 molecular sieve single crystals. Background Art

[0002] Lower olefins such as ethylene and propylene are important basic chemical raw materials. At present, lower olefins are mainly obtained through the petroleum-based route of naphtha cracking. Considering China's energy structure of "rich in coal, poor in oil, and short in gas", it is imperative to develop a coal-to-olefins route. The main route of coal-to-olefins is divided into the following three steps: (1) Coal reacts with water in a water-gas shift reaction to produce syngas carbon monoxide and hydrogen; (2) Carbon monoxide and hydrogen are pressurized and hydrogenated to produce methanol; (3) Methanol undergoes a methanol-to-olefins reaction (MTO) to obtain light olefins with ethylene and propylene as the main products. The methanol-to-olefins technology is a key step among them. Therefore, developing a high-performance MTO reaction catalyst is the key to the coal-to-olefins technology, which is of great significance to China's energy security.

[0003] Silicoaluminophosphate (SAPO) molecular sieve is a crystalline silicoaluminophosphate salt with a regular pore structure. SAPO molecular sieves with specific structures have pore structures of different sizes and shapes and mild acidity, and have good shape selectivity for specific reaction products, and are commonly used solid acid catalysts in industrial catalysis. Among them, the SAPO-34 molecular sieve with a CHA structure is the most ideal catalyst for the current MTO reaction due to its pore size of 0.38×0.38 nm and suitable acidity, and is also a catalyst support for tail gas denitrification (SCR), and is widely used as a solid acid catalyst for glycerol dehydration. However, conventional micron-sized SAPO-34 molecular sieves only have a microporous structure. As a catalyst for the MTO reaction, carbon is easily deposited in the pores during the reaction. These carbon deposits cover the acidic site centers of the molecular sieve, resulting in the inactivation of the molecular sieve catalyst and requiring frequent regeneration during the reaction. In addition, when the pure microporous SAPO-34 molecular sieve is used as a denitrification catalyst support, there is a problem of poor low-temperature denitrification performance, which further restricts its application in the MTO and SCR reactions.

[0004] For the above problems, there are currently two solutions: (1) nanosizing the micron-sized SAPO-34 molecular sieve crystals; (2) introducing mesopores (2 - 50 nm) or macropores (greater than 50 nm) into the single crystals of micron-sized SAPO-34 molecular sieves to synthesize hierarchical pore SAPO-34 molecular sieves. Both of the above methods can increase the specific surface area of the molecular sieve, thereby exposing more active centers and ultimately improving the pore utilization rate of the molecular sieve catalyst. In addition, nanosizing the molecular sieve crystals or introducing hierarchical pore structures into their single crystals can effectively shorten the diffusion distance of reaction intermediates, thereby reducing the carbon deposition rate during the MTO reaction and effectively extending the service life of the catalyst. However, the nanomolecular sieves in the first solution have problems such as low crystallinity and difficult separation during production and use, which hinder their development. Relatively speaking, the second solution can effectively improve its diffusion performance during catalysis while retaining the crystallinity and larger crystal particle size by introducing hierarchical pore structures into the single crystal SAPO-34 molecular sieve. At the same time, it also avoids problems such as difficult separation existing in the production and use of nanomolecular sieves. Therefore, the second solution is more effective and promising.

[0005] Currently, the methods for preparing hierarchical pore SAPO-34 molecular sieves mainly include post-treatment methods, soft template methods, hard template methods, etc. Among them, the post-treatment method usually uses acids or alkalis to post-treat micron-sized microporous molecular sieves to remove silicon atoms or aluminum atoms in the crystal framework of the molecular sieve, thereby introducing mesopores or macropores. Although the post-treatment method has advantages such as simple operation and low cost and is widely used in actual industrial production, it is often difficult to effectively control the degree of desilication and dealumination during the post-treatment of the molecular sieve with acids and alkalis. In addition, compared with silica-alumina molecular sieves, SAPO molecular sieves have poor framework stability and are prone to excessive removal of framework elements, ultimately resulting in the destruction of the microporous structure of the molecular sieve and the loss of a large number of active centers. CN115010147A has achieved the regulation of the morphology and active centers of the molecular sieve to a certain extent through strategies such as chemical etching post-treatment, mother liquor etching based on crystal metastability, and seed-assisted synthesis.

[0006] The soft template method involves uniformly mixing surfactants, polyelectrolytes, etc. with the molecular sieve precursor gel. By utilizing the hydrogen bonding or electrostatic forces between the molecular chains of the soft template and the molecular sieve precursor gel, the template agent molecules are embedded into the molecular sieve crystal. After crystallization, the soft template is removed by means such as calcination, and finally hierarchical pore molecular sieves are obtained. CN118479493A reports a method for synthesizing hierarchical pore SAPO-34 molecular sieves with both microporous and mesoporous structures using a cationic surfactant as the soft template. This scheme can form a micro-mesoporous composite structure without the need for acid-base post-treatment or the addition of expensive mesoporous template agents such as organosilanes. Although it has advantages such as simple process and low raw material cost, it also has disadvantages such as high price of the soft template and difficulty in large-scale industrial production.

[0007] Similar to the soft template method, the hard template method usually mixes rigid particles (such as carbon materials, starch particles, calcium carbonate, etc.) with the molecular sieve precursor gel. After crystallization, the hard template is removed by means of calcination or dissolution, thereby introducing mesopores or macropores. However, a large number of "dead pores" that do not communicate with the outer surface easily appear in the existing hard template method. The key to synthesizing high-performance hierarchical pore molecular sieves lies in the hierarchical pore channels of the molecular sieve being interconnected and connected to the outer surface of the molecular sieve crystal (i.e., trying to avoid the formation of "dead pores"), enabling reactants to diffuse more quickly into the microporous active centers of the molecular sieve, and at the same time enabling product molecules to diffuse more quickly out of the molecular sieve crystal after the reaction, ultimately effectively improving the diffusion performance of the catalyst and achieving an extended catalytic life. Although the above three methods have been widely reported and applied in the synthesis process of hierarchical pore molecular sieves, in actual experiments and production processes, it is still impossible to ensure that the introduced mesopores or macropores can be well interconnected and connected to the outer surface of the molecular sieve crystal. Summary of the Invention

[0008] The present invention mainly solves the problem that the pore channels cannot be guaranteed to be interconnected when synthesizing hierarchical pore SAPO-34 molecular sieves by existing methods. By developing a new type of carbon particle-packed carbon material as the hard template, single crystals of hierarchical pore SAPO-34 molecular sieves with highly interconnected pore channels are prepared. The molecular sieve exhibits a regular single crystal morphology. More importantly, the pore channels are completely interconnected and connected to the outer surface, effectively improving the problems such as high cost and difficulty in interconnecting pore channels that are commonly present in existing synthesis methods.

[0009] One object of the present invention is to provide a preparation method of a carbon particle-packed carbon template, including: uniformly mixing sucrose with a solvent, then adding ammonia water for hydrothermal crystallization reaction, and then performing high-temperature carbonization under a protective atmosphere to finally obtain the carbon particle-packed carbon template.

[0010] Furthermore, the solvent is selected from at least one of water and alcohol solvents, where the alcohol solvents include methanol, ethanol, and isopropanol.

[0011] Further, the solvent is specifically a mixed solution of water and an alcohol solvent, wherein the volume ratio of water to the alcohol solvent is 25% - 100%.

[0012] Further, the dosage ratio of sucrose, solvent, and ammonia water required for the reaction is 5 - 25 g: 10 - 25 mL: 1 mL.

[0013] Further, the concentration of the ammonia water is 5 - 30 mol / L.

[0014] Further, after sucrose is mixed with the solvent, it is first heated to 30 - 70 °C, then ammonia water is added and stirred evenly, and then the mixed solution is transferred to a hydrothermal crystallization kettle and fully crystallized at 120 - 220 °C. The obtained solid is crushed and then transferred to a tubular furnace, and heated to 500 - 900 °C under a protective atmosphere to make it fully carbonized, and finally cooled with the furnace to obtain a carbon particle-packed carbon template.

[0015] The second object of the present invention is to provide a carbon particle-packed carbon template having a rich mesoporous and macroporous structure prepared by the above method. The carbon particles are interconnected and stacked into a block shape, and the particle size of the carbon particles is 20 nm - 300 nm.

[0016] The third object of the present invention is to provide the application of the above carbon particle-packed carbon template in the preparation of a hierarchically porous SAPO-34 molecular sieve single crystal with highly interconnected pores.

[0017] Further, the specific process of the application is as follows: A molecular sieve precursor gel is prepared using an aluminum source, a phosphorus source, a silicon source, an organic structure-directing agent, and a solvent. The carbon particle-packed carbon template is mixed evenly with the molecular sieve precursor gel, and the obtained mixture is heated for a hydrothermal crystallization reaction. Finally, the carbon template and the organic structure-directing agent are removed by high-temperature calcination to obtain a hierarchically porous SAPO-34 molecular sieve single crystal with completely interconnected pores.

[0018] Further, the aluminum source is selected from at least one of pseudo-boehmite, aluminum isopropoxide, and aluminum hydroxide; the phosphorus source is selected from at least one of phosphoric acid, ammonium phosphate, and ammonium dihydrogen phosphate; the silicon source is selected from at least one of silica sol, fumed silica, and tetraethyl orthosilicate; the organic structure-directing agent is selected from at least one of morpholine, triethylamine, tetraethylammonium hydroxide, and diethylamine; and the solvent is specifically water.

[0019] Further, the molar ratio of phosphorus to aluminum (P / Al) in the molecular sieve precursor gel is 0.5 to 2.0, preferably 0.8 to 1.2; the molar ratio of silicon to aluminum (Si / Al) does not exceed 1.0, preferably does not exceed 0.5; the ratio of the organic structure-directing agent to the sum of the amounts of aluminum, phosphorus, and silicon elements (i.e., organic structure-directing agent: (nSi + nAl + nP)) is 0.05 to 2.0, preferably 0.5 to 1.2; the ratio of the solvent to the amount of aluminum element (i.e., H 2 O / Al) is 2 to 800, preferably 100 to 200.

[0020] Further, the mass ratio of the carbon particle-packed carbon template to the molecular sieve precursor gel is 1:1 - 100, preferably 1:5 - 10.

[0021] Further, the mixture needs to be aged before hydrothermal crystallization, and the crystallinity of the molecular sieve after aging is higher.

[0022] Further, the equipment used for aging is a blast drying oven, the aging temperature is 40 to 150 °C, preferably 40 to 80 °C; the aging time is controlled within 5 to 60 hours, preferably 10 to 24 hours.

[0023] Further, the equipment used for hydrothermal crystallization is a hydrothermal crystallization autoclave, the hydrothermal crystallization reaction temperature is 150 to 250 °C, preferably 180 to 220 °C; the hydrothermal crystallization reaction time is 1 to 200 hours, preferably 12 h to 72 hours.

[0024] Further, after the hydrothermal crystallization reaction of the mixture is completed, it is cooled to room temperature, then repeatedly washed clean with the solvent required for the reaction, and then placed at 60 to 150 °C (preferably 80 to 110 °C) for sufficient drying.

[0025] Further, the equipment used for calcination is a muffle furnace, the calcination temperature is 400 to 750 °C (preferably 500 to 650 °C), the calcination atmosphere is air, and it is cooled to room temperature with the furnace after calcination.

[0026] The fourth object of the present invention is to provide a hierarchical pore SAPO-34 molecular sieve single crystal, which has a regular single crystal morphology, and all the pore channels are completely interconnected and connected to the outer surface of the molecular sieve.

[0027] Compared with existing similar products and technologies, the progressiveness of the present invention is mainly reflected in the following points:

[0028] (1) A new type of template agent is developed. This template agent uses sucrose, ammonia water, etc. as raw materials, and has the advantages of cheap and easily available raw materials, simple preparation process, etc. It can synthesize hierarchical pore SAPO-34 molecular sieve single crystals with excellent performance on a large scale at a low cost.

[0029] (2) Using the newly developed carbon particle-packed carbon template as a hard template, a hierarchically porous SAPO-34 molecular sieve single crystal with completely interconnected pores was synthesized, solving the common problems of poor controllability and non-interconnected pores in existing synthesis methods at a low cost and in an easily achievable manner, which is helpful for the popularization and application of the hierarchically porous SAPO-34 molecular sieve single crystal.

[0030] (3) The obtained hierarchically porous SAPO-34 molecular sieve single crystal has excellent performance. The macroporous structures inside are interconnected and connected to the outer surface of the molecular sieve, showing excellent catalytic activity.

[0031] (4) Compared with the previous preparation process of ZSM-5 molecular sieve single crystal in the research group (CN106283187B), the product, structure and synthesis method of the present invention are quite different from it. On the one hand, the preparation steps of the present invention are simpler and the overall cost is more advantageous. On the other hand, the secondary pores introduced in the hierarchically porous SAPO-34 molecular sieve with completely interconnected pores prepared by the present invention are disordered and interconnected mesoporous and macroporous structures, while the secondary pores of the ZSM-5 molecular sieve prepared by CN106283187B are ordered and uniform interconnected mesoporous and macroporous structures. Description of the Drawings

[0032] Figure 1 SEM image of the carbon particle-packed carbon template prepared in Example 1.

[0033] Figure 2 XRD patterns of the molecular sieve single crystals prepared in Example 4 and Comparative Example 1.

[0034] Figure 3 SEM image of the hierarchically porous SAPO-34 molecular sieve single crystal prepared in Example 4.

[0035] Figure 4 TEM and electron diffraction photos of the hierarchically porous SAPO-34 molecular sieve single crystal prepared in Example 4.

[0036] Figure 5 Methanol-to-olefins performance diagrams of the hierarchically porous SAPO-34 molecular sieves prepared in Example 1 and Example 4. Detailed Description of the Embodiments

[0037] To enable those of ordinary skill in the art to fully understand the technical solutions and beneficial effects of the present invention, the following further details are provided in conjunction with specific embodiments and the accompanying drawings.

[0038] Example 1

[0039] (1) Add 26.2 g of sucrose to a mixed solution composed of 15 mL of water and 20 mL of ethanol. Heat the resulting mixture to 50 °C and stir evenly. Then add 2 mL of ammonia water with a concentration of 13.3 mol / L and continue stirring for 4 hours. Next, transfer the mixed solution to a hydrothermal crystallization kettle, heat it to 180 °C, and keep it for crystallization for 48 hours. After the reaction, cool the hydrothermal crystallization kettle to room temperature to obtain a blocky carbon precursor. Crush it and transfer it to a tube furnace. Heat it to 850 °C in a nitrogen or argon atmosphere and keep it for carbonization for 5 hours. After cooling, a carbon particle-packed carbon template with a rich mesoporous and macroporous structure is obtained. Its scanning electron microscope (SEM) photograph is as Figure 1 shown.

[0040] (2) Add an appropriate amount of water to a beaker. Then, add aluminum isopropoxide, phosphoric acid, silica sol, and triethylamine (TEA) in sequence, and stir for 5 hours to make them evenly mixed to obtain a molecular sieve precursor gel. The molar ratio of this gel is P 2 O 5 :Al 2 O 3 :SiO 2 :TEA:H 2 O = 1:1:0.6:4:70.

[0041] Then, mix the molecular sieve precursor gel with the carbon template prepared in step (1) evenly according to a mass ratio of 6:1. Heat the resulting mixture to 60 °C and keep it for aging overnight to obtain a dry gel of the mixture.

[0042] Transfer the dry gel to a vial, fix the vial in a hydrothermal kettle with a polytetrafluoroethylene liner, and add a small amount of water outside the vial to facilitate steam-assisted crystallization. Heat the hydrothermal kettle to 200 °C and keep it for crystallization at this temperature for 24 hours. After the hydrothermal crystallization is completed, take out the sample in the vial, wash it by centrifugation with water until it is neutral, and then transfer it to an oven and dry it overnight at 100 °C. Finally, transfer the dried solid to a muffle furnace, heat it to 550 °C in an air atmosphere, and keep it for roasting at this temperature for 7 hours to remove the template agent and the organic structure-directing agent, obtaining a hierarchically porous single-crystalline SAPO-34 molecular sieve with through pores.

[0043] Example 2

[0044] (1) Add 35 g of sucrose to a mixed solution composed of 15 mL of water and 20 mL of ethanol. Heat the resulting mixture to 50 °C and stir evenly. Then add 2 mL of ammonia water with a concentration of 14.8 mol / L and continue stirring for 4 hours. Transfer the mixed solution to a hydrothermal crystallization kettle, heat it to 180 °C, and keep it for crystallization for 48 hours. After the reaction, cool the hydrothermal crystallization kettle to room temperature to obtain a blocky carbon precursor. Crush it and transfer it to a tubular furnace. Heat it to 850 °C under a nitrogen or argon atmosphere and keep it for carbonization for 5 hours. After cooling, a carbon template with carbon particles piled up is obtained.

[0045] (2) Add an appropriate amount of water to a beaker. Then, add pseudo-boehmite, phosphoric acid, silica sol, and triethylamine (TEA) in sequence, and stir for 5 hours to make them mix evenly, obtaining a molecular sieve precursor gel. The molar ratio of the components of this gel is P 2 O 5 :Al 2 O 3 :SiO 2 :TEA:H 2 O = 1:1:0.6:4:70.

[0046] Then, mix the molecular sieve precursor gel and the carbon template prepared in step (1) evenly according to a mass ratio of 6:1. Heat the resulting mixture to 60 °C and keep it for aging overnight to obtain a dry gel of the mixture.

[0047] Transfer the dry gel to a vial, fix the vial in a hydrothermal kettle with a polytetrafluoroethylene liner, and add a small amount of water outside the vial for steam-assisted crystallization. Heat the hydrothermal kettle to 200 °C and keep it for crystallization at this temperature for 24 hours. After the hydrothermal crystallization is completed, take out the sample in the vial, wash it with water by centrifugation until it is neutral, and then transfer it to an oven and dry it overnight at 100 °C. Finally, transfer the dried solid to a muffle furnace, heat it to 550 °C under an air atmosphere, and keep it for roasting for 7 hours to obtain a hierarchically porous single-crystalline SAPO-34 molecular sieve with interconnected pores.

[0048] Example 3

[0049] (1) Add 26.2 g of sucrose to a mixed solution composed of 15 mL of water and 20 mL of ethanol. Heat the resulting mixture to 50 °C and stir evenly. Then add 2 mL of ammonia water with a mass percentage concentration of 7.4% and continue stirring for 4 hours. Transfer the mixed solution to a hydrothermal crystallization kettle, heat it to 180 °C, and keep it for crystallization for 48 hours. After the reaction, cool the hydrothermal crystallization kettle to room temperature to obtain a blocky porous carbon precursor. Crush it and transfer it to a tubular furnace. Heat it to 850 °C under a nitrogen or argon atmosphere and keep it for carbonization for 5 hours. After cooling, a carbon template with carbon particles piled up is obtained.

[0050] (2) Add an appropriate amount of water to a beaker, and then successively add boehmite, phosphoric acid, tetraethyl orthosilicate, and morpholine (MOR), and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The molar ratio of the components of this gel is P 2 O 5 :Al 2 O 3 :SiO 2 :MOR:H 2 O = 1:1:0.4:4:70.

[0051] Then, mix the molecular sieve precursor gel with the carbon template prepared in step (1) evenly according to a mass ratio of 6:1, heat the resulting mixture to 60 °C and keep it warm and aged overnight to obtain a mixture xerogel.

[0052] Transfer the xerogel to a vial, fix the vial in a hydrothermal autoclave lined with polytetrafluoroethylene, and add a small amount of water outside the vial for steam-assisted crystallization. Heat the hydrothermal autoclave to 200 °C and keep it at this temperature for hydrothermal crystallization for 24 hours. After the crystallization is completed, take out the sample in the vial, wash it by centrifugation with water until it is neutral, and then transfer it to an oven and dry it overnight at 100 °C. Finally, transfer the dried solid to a muffle furnace, heat it to 550 °C in an air atmosphere and keep it calcined for 7 hours to obtain a hierarchically porous single-crystalline SAPO-34 molecular sieve with interconnected pores.

[0053] Example 4

[0054] (1) Add 26.2 g of sucrose to a mixed solution composed of 15 mL of water and 20 mL of ethanol, heat the resulting mixture to 50 °C and stir it evenly. Then add 2 mL of ammonia water with a concentration of 13.3 mol / L and continue to stir for 4 hours. Transfer the mixed solution to a hydrothermal crystallization autoclave, heat it to 180 °C and keep it for hydrothermal crystallization for 48 hours. After the reaction, cool the hydrothermal crystallization autoclave to room temperature to obtain a blocky carbon precursor, crush it and transfer it to a tubular furnace, heat it to 850 °C in a nitrogen or argon atmosphere and keep it carbonized for 5 hours, and then cool it to obtain a carbon template with carbon particles stacked.

[0055] (2) Add an appropriate amount of water to a beaker, and then successively add boehmite, phosphoric acid, tetraethyl orthosilicate, and morpholine, and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The molar ratio of the components of this gel is P 2 O 5 :Al 2 O 3 :SiO 2 :MOR:H 2 O = 1:1:0.6:4:70.

[0056] Next, the molecular sieve precursor gel was mixed evenly with the carbon template prepared in step (1) according to a mass ratio of 6:1. The obtained mixture was heated to 60 °C and aged overnight to obtain a dry gel of the mixture.

[0057] The dry gel was transferred to a vial, and the vial was fixed in a hydrothermal autoclave lined with polytetrafluoroethylene. A small amount of water was added outside the vial for steam-assisted crystallization. The hydrothermal autoclave was heated to 200 °C and crystallized at this temperature for 24 hours. After the crystallization was completed, the sample in the vial was taken out, centrifugally washed with water until neutral, and then transferred to an oven and dried overnight at 100 °C. Finally, the dried solid was transferred to a muffle furnace and heated to 550 °C in an air atmosphere and calcined for 7 hours to obtain a hierarchically porous single-crystalline SAPO-34 molecular sieve with interconnected pores, denoted as H-SAPO-34-4.

[0058] Example 5

[0059] (1) 26.2 g of sucrose was added to a mixed solution composed of 15 mL of water and 20 mL of ethanol. The obtained mixture was heated to 50 °C and stirred evenly. Then 2 mL of ammonia water with a concentration of 26.6 mol / L was added and stirring was continued for 4 hours. The mixed solution was transferred to a hydrothermal crystallization autoclave and heated to 180 °C for crystallization for 48 hours. After the reaction, the hydrothermal crystallization autoclave was cooled to room temperature to obtain a massive carbon precursor, which was crushed and then transferred to a tubular furnace and heated to 850 °C in a nitrogen or argon atmosphere and carbonized for 5 hours. After cooling, a carbon template with carbon particles piled up was obtained.

[0060] (2) An appropriate amount of water was added to a beaker, and then pseudoboehmite, phosphoric acid, silica sol, and morpholine were added in sequence and stirred for 5 hours to mix evenly to obtain a molecular sieve precursor gel. The molar ratio of the gel was P 2 O 5 :Al 2 O 3 :SiO 2 :MOR:H 2 O = 1:1:0.6:4:70.

[0061] Next, the molecular sieve precursor gel was mixed evenly with the carbon template prepared in step (1) according to a mass ratio of 6:1. The obtained mixture was transferred to a hydrothermal autoclave lined with polytetrafluoroethylene. The hydrothermal autoclave was heated to 200 °C and crystallized for 24 hours. After the crystallization was completed, the sample in the vial was taken out, centrifugally washed with water until neutral, and then transferred to an oven and dried overnight at 100 °C. Finally, the dried solid was transferred to a muffle furnace and heated to 550 °C in an air atmosphere and calcined for 7 hours to obtain a hierarchically porous single-crystalline SAPO-34 molecular sieve.

[0062] Comparative Example

[0063] Add an appropriate amount of water into a beaker, and then sequentially add pseudoboehmite, phosphoric acid, silica sol, and morpholine, and stir for 5 hours to make them evenly mixed, obtaining a molecular sieve precursor gel. The molar ratio of the substances in this gel is P 2 O 5 :Al 2 O 3 :SiO 2 :MOR:H 2 O = 1:1:0.6:3:70.

[0064] Transfer the molecular sieve precursor gel to a hydrothermal autoclave lined with polytetrafluoroethylene, heat it to 200 °C, and keep it crystallizing for 24 hours. After the crystallization is completed, take out the sample, wash it by centrifugation with water until it is neutral, and then transfer it to an oven and dry it overnight at 100 °C. Finally, transfer the dried solid to a muffle furnace, heat it to 550 °C in an air atmosphere, and keep it calcined for 7 hours, thereby obtaining micro-sized SAPO-34 molecular sieves with only microporous channels, denoted as C-SAPO-34.

[0065] To fully understand the performance of each molecular sieve sample prepared by the present invention, SEM, XRD and other analytical tests were carried out taking the products of Example 4 and the comparative examples as examples, and the results are as Figures 1-5 shown.

[0066] The XRD test results of the molecular sieves prepared in Example 4 and the comparative examples are as Figure 2 shown. It can be seen from the figure that both samples show typical diffraction peaks of the CHA structure, indicating that these samples are all pure phases.

[0067] The scanning electron microscope (SEM) photograph of the H-SAPO-34-4 molecular sieve sample prepared in Example 4 is as Figure 3 shown. It can be observed from the figure that the sample has an obvious macroporous structure, and its morphology shows the typical single crystal structure of SAPO-34 molecular sieves, indicating that the hierarchical pore SAPO-34 molecular sieves have been successfully synthesized.

[0068] The transmission electron microscope (TEM) photograph and electron diffraction results of the H-SAPO-34-4 molecular sieve sample prepared in Example 4 are as Figure 4 shown. It can be observed from the figure that the macroporous structures inside the crystal are interconnected and connected to the outer surface of the molecular sieve, and at the same time, the electron diffraction is dot-like, indicating that the molecular sieve sample particles prepared in Example 4 are single crystals.

[0069] The methanol-to-olefins (MTO) reaction performance tests were carried out using the molecular sieves prepared in the comparative examples and Example 4, the reaction temperature was 400 °C, and the methanol space velocity was 1 h -1 . The test results are as Figure 5 shown.

[0070] As can be seen from the figure, the MTO lifetime (conversion rate > 99%) of the hierarchical pore H-SAPO-34-4 molecular sieve sample prepared in Example 4 is 505 minutes, which is more than three times that of the C-SAPO-34 molecular sieve sample (155 minutes) prepared in the comparative example. This result shows that the hierarchical pore SAPO-34 single crystal molecular sieve sample with through pores provided by the present invention indeed has a high MTO catalytic lifetime.

Claims

1. A carbon template for carbon particle accumulation with rich mesoporous and macroporous structures, characterized in that: The particle size of the carbon particles is 20-300 nm, and the carbon particles are interconnected and stacked into blocks.

2. The method for preparing the carbon template of carbon particle accumulation according to claim 1, characterized in that The method comprises: mixing sucrose and a solvent uniformly, adding ammonia water to carry out a hydrothermal crystallization reaction, and then carbonizing at a high temperature under a protective atmosphere to obtain a carbon particle accumulation carbon template.

3. The method according to claim 2, characterized in that: The solvent is selected from at least one of water and alcohol solvents, the alcohol solvents include methanol, ethanol, and isopropanol, and the concentration of the ammonia water is 5-30 mol / L.

4. The method according to claim 2, characterized in that: The dosage ratio of sucrose, solvent and ammonia water required for the reaction is 5-25g:10-25mL:1mL.

5. The method according to claim 2, characterized in that: After the sucrose and the solvent are mixed, they are first heated to 30-70°C, and then ammonia water is added and fully stirred. The mixed solution is then transferred to a hydrothermal crystallization kettle and continued to be heated to 120-220°C for hydrothermal crystallization. The obtained solid is crushed and heated to 500-900°C under a protective atmosphere for carbonization. After cooling in the furnace, a carbon template for carbon particle accumulation is obtained.

6. A method for preparing hierarchical pore SAPO-34 molecular sieve single crystals with highly interconnected pores by using the carbon particle stacking carbon template according to claim 1, characterized in that The method comprises: preparing a molecular sieve precursor gel by using an aluminum source, a phosphorus source, a silicon source, an organic structure directing agent and a solvent, uniformly mixing the carbon particle stacking carbon template with the molecular sieve precursor gel, and sequentially subjecting the obtained mixture to a hydrothermal crystallization treatment and a high-temperature calcination treatment to obtain a hierarchical pore SAPO-34 molecular sieve single crystal with completely connected pores.

7. The method according to claim 6, characterized in that: The aluminum source is selected from at least one of pseudo-boehmite, aluminum isopropoxide, and aluminum hydroxide; the phosphorus source is selected from at least one of phosphoric acid, ammonium phosphate, and ammonium dihydrogen phosphate; the silicon source is selected from at least one of silica sol, fumed silica, and tetraethyl silicate; the organic structure directing agent is selected from at least one of morpholine, triethylamine, tetraethylammonium hydroxide, and diethylamine; and the solvent is specifically water.

8. The method according to claim 6, characterized in that: The mass ratio of phosphorus to aluminum (P / Al) in the molecular sieve precursor gel is 0.5-2.0, the mass ratio of silicon to aluminum (Si / Al) does not exceed 1.0, the ratio of the organic structure directing agent to the sum of the mass of aluminum, phosphorus and silicon is 0.05-2.0, the mass ratio of the solvent to the aluminum element is 2-800, and the mass ratio of the carbon particle stacking carbon template to the molecular sieve precursor gel is 1:1-100.

9. The method according to claim 6, characterized in that: The mixture needs to be aged before the hydrothermal crystallization treatment. The aging treatment temperature is 40 to 150° C. and the aging treatment time is 5 to 60 hours.

10. The method according to claim 6, characterized in that: The hydrothermal crystallization treatment temperature is 150-250°C, the hydrothermal crystallization treatment time is 1-200h, and after the hydrothermal crystallization treatment, the mixture is cooled to room temperature, then washed and fully dried at 60-150°C; the roasting treatment temperature is 400-750°C, the roasting treatment atmosphere is air, and after roasting, it is cooled to room temperature with the furnace.

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