Preparation method of hierarchical pore Y-type molecular sieve

Abstract

The present invention provides a method for preparing a multi-level hole Y-type molecular sieve, comprising the steps of: mixing a silicon source, an aluminum source, a carbonate and a Y-type molecular sieve structure directing agent to form a gel, the gel is hydrothermally crystallized, separated, washed, and roasted to obtain the multi-level hole Y-type molecular sieve; wherein the SiO in the silicon source is 100:1-15 in a molar ratio with the carbonate. When the Y molecular sieve forms an initial skeleton unit, the present invention, by adding carbonate, utilizes the coordination of a Y-type molecular sieve directing agent (without organic matter) and carbonate, utilizes sodium ions and carbonate ions to balance the negative charge of the skeleton and enters the initial structural unit, in conjunction with subsequent roasting process, carbonate reacts with the silicon and aluminum in the skeleton to form a mesopore, and realizes omitting an organic template to prepare a multi-level hole Y-type molecular sieve, not only overcomes the pollution problem caused by the organic template, but also greatly reduces cost.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve synthesis, and particularly relates to a preparation method of a multi-level pore Y-type molecular sieve. Background Art

[0002] Y-type molecular sieve is a microporous aluminosilicate. Due to its large specific surface area, strong acidity, ordered microporous structure, good hydrothermal stability, and good shape selectivity, it plays an important role in the fields of petroleum catalytic cracking and hydrocracking. However, its inherent pore structure (generally less than 1 nm) is not conducive to the accessibility of macromolecular compounds to active sites, resulting in reduced reaction activity. Furthermore, the narrow pores are not conducive to the diffusion of reactants and products, thus affecting mass transfer efficiency and catalyst utilization efficiency, resulting in reduced conversion rate and coke deposition. These shortcomings greatly shorten the service life of the catalyst, limiting its industrial application.

[0003] To overcome these shortcomings, the introduction of mesopores is necessary. Meso-microporous molecular sieves not only retain the advantages of microporous molecular sieves but also overcome the disadvantages of microporous channels due to their narrow pores. This significantly improves the catalyst's service life and industrial applications. Therefore, the introduction of mesopores into conventional Y-type molecular sieves is crucial.

[0004] Huang et al. (Angewandte Chemie International Edition, 2017, 56: 12553-12556) combined the dealumination and desiliconization processes for aluminum-rich molecular sieves to construct a hierarchical pore structure (Si / Al = 10-20) in a high-Al content ZSM-5 molecular sieve. By continuously treating ZSM-5 crystals of different particle sizes with steam and alkali, the silicon and aluminum atoms are reconstructed inside the molecular sieve, and the removal of aluminum leads to the formation of mesopores. Although this method of removing framework atoms has been used for industrial-scale production due to its ease of operation and economic benefits, its low crystallinity and pore connectivity have limited further development.

[0005] Chinese patent document CN106809857A discloses a method for synthesizing ordered macroporous-mesoporous-microporous multi-level pore Y-type molecular sieves. Y-type molecular sieve nanocrystals are mixed with macroporous template polymer microspheres and dispersed in water to form a suspension. An organic carbon source and a strong oxidizing acid are added to the suspension, and then ultrasonic evaporation and self-assembly are performed to obtain a mixed solution. The mixture is then carbonized and solidified, and finally calcined at high temperature to obtain an ordered macroporous-mesoporous-microporous multi-level pore Y-type molecular sieve. This method can regulate the silicon-aluminum ratio and macropore diameter of the molecular sieve. However, this method has complex steps, high cost, and pollution problems when preparing the molecular sieve.

[0006] Chinese patent document CN106927479A discloses a method for preparing a mesoporous Y-type molecular sieve, which comprises: (1) mixing a silicon source, an aluminum source, and water, and aging to obtain a directing agent; (2) mixing the silicon source and the directing agent, and then adding an aluminum source and water to obtain a crystallization solution I. (3) adding polyacrylamide to the crystallization solution I, crystallizing, and recovering the product. The pore size of the product is concentrated in the range of 1.5 to 3 nm. However, this method uses an organic polyacrylamide as a template, and the use of organic matter has certain environmental pollution and is not conducive to large-scale production and application.

[0007] Choi et al. (Nature Materials, 2006, 5:718-723) combined traditional surfactants with organosilanes to produce 3-(trimethoxysilyl)propylhexadecyldimethylammonium chloride (TPHAC). The hydrolyzed methoxy groups are stably linked to the silica-alumina species via covalent bonds, effectively mitigating phase separation. Adjusting the length of the hydrophobic alkyl chain can correspondingly alter the size of the mesoporous channels. However, this method uses organic matter to form the mesopores during the preparation process, which is environmentally unfriendly and unsuitable for industrial production.

[0008] Zhao et al. (Catalysis Communications, 2016, 73:98-102) synthesized mesoporous molecular sieve Y using a hydrothermal method using a P123 block copolymer as a template. Evaluation of the catalyst's microactivity revealed that Meso-CAT-3 had the highest microactivity and the lowest coke yield. This was attributed to the mesoporous structure improving the mass transfer of macromolecules. However, this method requires the use of P123 as a template, which is environmentally unfriendly.

[0009] Chinese patent document CN111689504A discloses a method for preparing a Y-type zeolite molecular sieve with a meso-micro hierarchical pore structure. The method process includes: mixing NaY zeolite molecular sieve, ammonium salt and water, and obtaining an ammonium type Y-type zeolite molecular sieve after stirring, filtering and washing; mixing ammonium type Y-type zeolite molecular sieve, a boron-containing compound and water, and then filtering, washing, and finally subjecting to high temperature hydrothermal treatment to obtain a meso-micro hierarchical pore structure Y-type zeolite molecular sieve. Relative to traditional Y-type zeolite molecular sieve, the meso-micro hierarchical pore structure Y-type zeolite molecular sieve provided by the present invention has abundant mesoporous channel structure, and its preparation method process is simple, environmentally friendly and low cost. However, irritating odor is easily generated during the synthesis of the method.

[0010] Chinese patent document CN113003585A discloses a method for preparing a meso-micro hierarchical pore structure Y-type molecular sieve. The method comprises the following steps: (1) mixing and slurrying NaY molecular sieve with deionized water, adjusting the pH of the slurry system to within the range of 3-6 with dilute hydrochloric acid, adding polycarboxylic acid and boron-containing compound, heating to 60-90°C and stirring for 0.5-5 hours, adding water glass solution, stirring for 5-30 minutes, filtering, washing, drying and then performing high-temperature water vapor ultrastabilization treatment; (2) mixing and slurrying the molecular sieve obtained in (1) with deionized water, adding sodium alkyl sulfonic acid salt, stirring for 0.5-3 hours at 50-85°C, filtering, washing, drying and calcining to obtain the meso-micro hierarchical pore structure Y-type molecular sieve. The prepared sample not only has significantly higher mesoporous specific surface area and mesoporous pore volume, but also has significantly higher crystallinity. However, this method uses organic matter in the preparation process, which is not conducive to industrial production.

[0011] Chinese patent document CN110627089A discloses a mesoporous Y-type molecular sieve, its preparation method, and application. The method involves preparing a directing agent using a portion of a silicon source, an aluminum source, a zirconium source, and water; using the remaining raw materials to prepare a mother liquor; mixing the directing agent with the mother liquor to form a gel, and crystallizing the resulting mesoporous Y-type molecular sieve. The mesoporous Y-type molecular sieve prepared by this method has high crystallinity and good catalytic performance, but its external specific surface area is relatively small and needs to be improved.

[0012] Huang et al. (Microporous and Mesoporous Materials, 2010, 127:167-175) used a three-stage temperature control method to synthesize well-crystallized hierarchically porous NaY nanocrystals without adding any organic additives, pore-forming agents, or seed crystals. However, this method takes a long time to synthesize, making it unsuitable for widespread application.

[0013] Chinese patent document CN103172082A discloses a method for preparing a mesoporous Y-type molecular sieve. The molecular sieve is post-treated with an organic acid aqueous solution and a NaOH solution, and a mesoporous Y-type molecular sieve is finally obtained. This method is simple and effective to obtain abundant mesopores, and the microporosity remains unchanged. However, this method uses an organic acid and a strong alkaline solution when post-treating the molecular sieve. This method has certain pollution to the environment and has certain limitations in industrial development.

[0014] Chinese patent document CN107973313A discloses a mesoporous Y molecular sieve and its preparation method. The process involves subjecting a NaY molecular sieve to ammonium exchange, followed by filtration, washing, and calcination. Desiliconization, acid dealumination, and alkaline treatment are then performed, followed by a second dealumination treatment to yield a mesoporous Y molecular sieve. The molecular sieve obtained by this method is used as an active component in the preparation of a catalyst for heavy oil catalytic cracking, demonstrating excellent heavy oil conversion and higher gasoline and liquefied gas yields. However, the process is relatively complex, making it difficult to commercialize. Summary of the Invention

[0015] The purpose of the present invention is to provide a preparation method of a multi-level pore Y-type molecular sieve, which synthesizes the multi-level pore Y-type molecular sieve without using an organic template and does not destroy the overall pore structure. While reducing the synthesis cost of the multi-level pore Y-type molecular sieve, the preparation method is environmentally friendly.

[0016] In order to achieve the above object, the present invention provides the following technical solutions:

[0017] A method for preparing a multi-level pore Y-type molecular sieve comprises the following steps:

[0018] A silicon source, an aluminum source, an alkali source, a carbonate and a Y-type molecular sieve structure directing agent are mixed to form a gel, and the gel is subjected to hydrothermal crystallization, separation, washing, drying and calcination to obtain the multi-level pore Y-type molecular sieve;

[0019] Wherein, the molar ratio of SiO2 in the silicon source to the carbonate is 100:1-15, preferably 100:1-10.

[0020] Optionally, after mixing the silicon source and the carbonate, the aluminum source and the alkali source are added, and finally the Y-type molecular sieve structure directing agent is added; or

[0021] After the silicon source and the aluminum source are mixed, the carbonate and the alkali source are added, and finally the Y-type molecular sieve structure directing agent is added.

[0022] Optionally, the temperature for forming the gel is 25-50° C., and the time is 1-5 hours.

[0023] Optionally, the preparation of the Y-type molecular sieve structure directing agent comprises the following steps: mixing a silicon source, an aluminum source, an inorganic base (sodium hydroxide) and water and then aging; preferably, the aging temperature is 25-80° C. and the time is 12-36 hours.

[0024] Optionally, the molar ratio of the components in the Y-type molecular sieve structure directing agent, calculated as oxides, is: (1-30) Na2O:Al2O3:(1-40)SiO2:(200-800)H2O, preferably (5-20)Na2O:Al2O3:(5-20)SiO2:(200-400)H2O, wherein (the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the inorganic base (sodium hydroxide) is calculated as Na2O, and the water is calculated as H2O).

[0025] Optionally, in the gel, calculated as oxides, the molar ratio of the alkali source (calculated as sodium oxide), the aluminum source (calculated as aluminum oxide), and the silicon source (calculated as silicon oxide) is (0.1-80)Na2O:Al2O3:(1-200)SiO2:(10-800)H2O, preferably (2-30)Na2O:Al2O3:(2-100)SiO2:(50-400)H2O, wherein the H2O includes the water added during the preparation of the gel and the water introduced into the alkali source, the aluminum source, and the silicon source.

[0026] Optionally, the alkali source can be selected from sodium hydroxide and / or a high alkali solution. The preparation of the high alkali solution comprises the following steps: heating an aqueous solution of sodium hydroxide, adding aluminum hydroxide powder and stirring until dissolved, thereby obtaining the high alkali solution. The molar ratio of each component in the high alkali solution, calculated as oxide, is (10-15) Na2O:Al2O3:(100-200)H2O.

[0027] Optionally, the molar ratio of the components in the high alkaline solution calculated as oxides is (10-13)Na2O:Al2O3:(100-160)H2O.

[0028] Optionally, the aqueous solution of sodium hydroxide further contains sodium carbonate, and the molar ratio of the aluminum hydroxide powder, calculated as aluminum oxide, to the sodium carbonate is ≤5.

[0029] Optionally, the hydrothermal crystallization temperature is 90-150° C. and the time is 12-48 hours;

[0030] The calcination temperature is 400-600° C. and the calcination time is 6-10 hours.

[0031] Optionally, the silicon source is selected from one or more of water glass, ethyl orthosilicate and silicon powder;

[0032] The aluminum source is selected from one or more of the above-mentioned high alkaline solution, aluminum sulfate 18-hydrate, aluminum oxide, aluminum chloride and aluminum isopropoxide;

[0033] The carbonate is selected from one or more of sodium carbonate, potassium carbonate and ammonium carbonate.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] The preparation method of the multi-stage hole Y type molecular sieve provided by the present invention, when Y molecular sieve forms initial skeleton unit, by adding carbonate, utilizing the coordination of Y type molecular sieve directing agent (without organic matter) and carbonate, utilizing sodium ion and carbonate ion to balance the negative charge of the skeleton and enter in the initial structural unit, in conjunction with subsequent roasting process, carbonate reacts with the silicon-aluminum in the skeleton to form mesopores, it is achieved that organic template is omitted to prepare multi-stage hole Y type molecular sieve, not only overcomes the pollution problem brought by organic template, also reduces cost to a great extent. If carbonate is directly added to Y type molecular sieve directing agent, it is impossible to play pore expansion effect in Y molecular sieve skeleton growth process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the X-ray diffraction pattern of the multi-level pore Y-type molecular sieve prepared in Example 1 of the present invention;

[0037] Figure 2 1 is a graph showing the N2 adsorption and desorption curves of the multi-level pore Y-type molecular sieve prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above disclosure.

[0039] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0040] Sources of raw materials: Aluminum sulfate and other raw materials were obtained from PetroChina Lanzhou Petrochemical Company, and are all industrial products; the template agent TPHAC was purchased from Anhui Jinao Chemical Co., Ltd., and is an industrial product; sodium carbonate, potassium carbonate, etc. are all commercially available reagents, and are of industrial grade.

[0041] Analytical Method: Phase analysis and confirmation were performed using a Shimadzu XRD-7000 X-ray crystal powder diffractometer. Instrument parameters: Cu-Ka radiation, wavelength 0.1543 nm, tube voltage 40 kV, tube current 30 mA. Test conditions: scanning angle 5-40°, scanning speed 6° / min.

[0042] The adsorption-desorption isotherms of the samples were measured at liquid nitrogen temperature using the ASAP2020M fully automatic adsorption instrument produced by Micromeritics, USA. Nitrogen was used as the adsorbate, and the Brunauer-Emmett-Teller (BET) equation was used to calculate the specific surface area of the samples based on the adsorption equilibrium isotherm between relative pressures of 0.05 and 0.25. The t-plot model was used to distinguish the internal and external surface areas of the samples, and the static capacity method was used to determine the pore volume and pore size distribution, thereby calculating the pore structure parameters.

[0043] Synthesis of structure-directing agent 1:

[0044] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH were mixed in a molar ratio of 16Na2O:Al2O3:15SiO2:320H2O, and the mixture was aged at 35°C for 16 hours to obtain the product.

[0045] Synthesis of structure-directing agent 2:

[0046] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH are mixed in a molar ratio of 5Na2O:Al2O3:5SiO2:200H2O, and the mixture is aged at 80°C for 12 hours to obtain the product.

[0047] Synthesis of structure-directing agent 3:

[0048] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH are mixed in a molar ratio of 16Na2O:Al2O3:15SiO2:320H2O, and the mixture is aged at 25°C for 20 hours to obtain the product.

[0049] Synthesis of structure-directing agent 4:

[0050] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH are mixed in a molar ratio of 16Na2O:Al2O3:15SiO2:320H2O, and the mixture is aged at 45°C for 36 hours to obtain the product.

[0051] Synthesis of structure-directing agent 5:

[0052] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH were mixed in a molar ratio of 30 Na2O:Al2O3:40 SiO2:800 H2O, and the mixture was aged at 80°C for 20 hours to obtain the product.

[0053] Synthesis of structure-directing agent 6:

[0054] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH are mixed in a molar ratio of Na2O:Al2O3:SiO2:200H2O, and the mixture is aged at 60°C for 36 hours to obtain the product.

[0055] Synthesis of structure-directing agent 7:

[0056] Calculated as oxides, silicon powder, aluminum oxide, deionized water, and NaOH are mixed in a molar ratio of 20Na2O:Al2O3:20SiO2:200H2O and aged at 45°C for 20h to obtain the product.

[0057] Preparation of high alkaline solution 1:

[0058] Sodium hydroxide and sodium carbonate are dissolved in deionized water and heated to 95°C. Aluminum hydroxide powder is then added and stirred until dissolved to produce the high-alkali solution. The molar ratio of the materials in the high-alkali solution, calculated as oxides (sodium carbonate is still calculated as sodium carbonate), is: 10 Na2O:Al2O3:150 H2O:2Na2CO3.

[0059] Preparation of high alkaline solution 2:

[0060] Sodium hydroxide and sodium carbonate are dissolved in deionized water and heated to 95°C. Aluminum hydroxide powder is then added and stirred until dissolved to produce the high-alkali solution. The molar ratio of the materials in the high-alkali solution, calculated as oxides (sodium carbonate is still calculated as sodium carbonate), is: 15 Na2O: Al2O3: 200 H2O: 5 Na2CO3.

[0061] The ratio of high alkaline solution 3:

[0062] Sodium hydroxide is dissolved in deionized water and heated to 95°C, followed by the addition of aluminum hydroxide powder and stirring until dissolved to obtain the high alkaline solution. The molar ratio of the materials in the high alkaline solution, calculated as oxides, is: 10 Na2O: Al2O3: 100 H2O.

[0063] Example 1

[0064] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 2.85 Na2O:Al2O3:8.4 SiO2:200 H2O. 46.75g of water glass and 4g of sodium carbonate were mixed and stirred uniformly. A solution of 10.5g of aluminum sulfate 18hydrate and 23.75g of water, followed by 10.64g of high-alkali solution 1, were then added and stirred uniformly to form an initial gel. Finally, 7.4g of structure-directing agent 1 was added and stirred at 35°C for 3 hours to form a gel. The molar ratio of SiO2 to sodium carbonate in the water glass was 100:13. The gel was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 24 hours. The mixture was filtered, washed with water until neutral, dried at 90°C, and calcined at 550°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0065] The multi-level pore Y-type molecular sieve was subjected to X-ray diffraction and N2 adsorption and desorption performance tests. The specific results are as follows Figure 1 and Figure 2As shown. Figure 1 It can be seen that the molecular sieve has the characteristic diffraction peak of Y-type molecular sieve and good crystallinity. Figure 2 It can be seen that the molecular sieve has an obvious mesoporous structure, which indicates that the multi-level pore Y-type molecular sieve provided by the present invention has abundant mesopores and good crystallinity.

[0066] Example 2

[0067] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is Na2O:Al2O3:2SiO2:50H2O. A solution of 4.16g of tetraethyl orthosilicate (TES) with 1.02g of aluminum oxide and 9g of water is mixed and stirred to form an initial gel. 0.02g of sodium carbonate and 0.08g of sodium hydroxide are then added, followed by stirring. Finally, 0.714g of structure-directing agent 2 is added and stirred at 25°C for 3 hours to form a gel. The molar ratio of SiO2 to sodium carbonate in the TOS is 100:1. The gel is transferred to a polytetrafluoroethylene (PTFE) liner and crystallized at 95°C for 15 hours. The resulting mixture is then filtered, washed with water until neutral, dried at 90°C, and calcined at 400°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0068] Example 3

[0069] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 15Na2O:Al2O3:20SiO2:400H2O. After uniformly mixing 20.83g of tetraethyl orthosilicate with 1.38g of potassium carbonate, a solution of 1.33g of aluminum chloride and 36g of water, followed by 6g of sodium hydroxide, is added sequentially and stirred to form an initial gel. Finally, 3.2g of structure-directing agent 3 is added and stirred at 50°C for 1 hour to form a gel. The molar ratio of SiO2 to potassium carbonate in the tetraethyl orthosilicate is 100:10. The gel is transferred to a polytetrafluoroethylene-lined container and crystallized at 120°C for 36 hours. The mixture is then filtered, washed with water until neutral, dried at 90°C, and calcined at 600°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0070] Example 4

[0071] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 2.85Na2O:Al2O3:18SiO2:200H2O. 5.04g of silicon powder was mixed with a solution of 2.67g aluminum chloride and 36g of water, and stirred to form an initial gel. 1.34g of sodium carbonate and 2.28g of sodium hydroxide were then added, followed by stirring. Finally, 2.36g of structure-directing agent 4 was added and stirred at 35°C for 3 hours to form a gel. The molar ratio of SiO2 to sodium carbonate in the silicon powder was 100:15. The gel was transferred to a polytetrafluoroethylene (PTFE) liner and crystallized at 96°C for 24 hours. The gel was then filtered, washed with water until neutral, dried at 90°C, and calcined at 500°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0072] Example 5

[0073] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 2.85Na2O:Al2O3:8.6SiO2:200H2O. 2.4g of silicon powder was mixed with 1.21g of ammonium carbonate and stirred evenly. A solution of 4.08g of aluminum isopropoxide and 36g of water, followed by 2.28g of sodium hydroxide, was then added and stirred evenly to form an initial gel. Finally, 2.43g of structure-directing agent 5 was added and stirred at 35°C for 3 hours to form a gel. The molar ratio of SiO2 to ammonium carbonate in the silicon powder was 100:15. The gel was transferred to a polytetrafluoroethylene (PTFE) liner and crystallized at 120°C for 12 hours. The gel was then filtered, washed with water until neutral, dried at 90°C, and calcined at 600°C for 8 hours to obtain a hierarchical pore Y-type molecular sieve.

[0074] Example 6

[0075] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 2.85Na2O:Al2O3:8.4SiO2:200H2O. 25.65g of water glass was mixed with 4.08g of aluminum isopropoxide and 17g of water to form an initial gel. 2.28g of sodium hydroxide and 1.21g of ammonium carbonate were then added and stirred until uniform. Finally, 2.4g of structure-directing agent 6 was added and stirred at 35°C for 3 hours to form a gel. The molar ratio of SiO2 to ammonium carbonate in the water glass was 100:15. The gel was transferred to a polytetrafluoroethylene (PTFE) liner and crystallized at 100°C for 15 hours. The gel was then filtered, washed with water until neutral, dried at 90°C, and calcined at 500°C for 7 hours to obtain a hierarchical pore Y-type molecular sieve.

[0076] Example 7

[0077] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 5Na2O:Al2O3:15SiO2:200H2O. 45.81g of water glass and 2.16g of ammonium carbonate were mixed and stirred uniformly. Then, 4.08g of aluminum isopropoxide, 4.0g of sodium hydroxide, and 2.33g of water were added sequentially and stirred uniformly to form an initial gel. Finally, 2.72g of structure-directing agent 7 was added and stirred at 35°C for 5 hours to form a gel. The molar ratio of SiO2 to ammonium carbonate in the water glass was 100:15. The gel was transferred to a polytetrafluoroethylene-lined container and crystallized at 120°C for 12 hours. The mixture was then filtered, washed with water until neutral, dried at 90°C, and calcined at 550°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0078] Example 8

[0079] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components was 2.85 Na2O:Al2O3:8.4 SiO2:200 H2O. 25.65g of water glass was mixed with 1.02g of alumina and 17g of water, stirring evenly to form an initial gel. 1.34g of sodium carbonate and 10.64g of high-alkali solution 3 were then added, stirring evenly, and finally 2.25g of structure-directing agent 1 was added and stirred at 35°C for 3 hours. The molar ratio of SiO2 to sodium carbonate in the water glass was 100:15. The gel was transferred to a polytetrafluoroethylene (PTFE) liner and crystallized at 120°C for 12 hours. The gel was then filtered, washed with water until neutral, dried at 90°C, and calcined at 600°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0080] Example 9

[0081] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source components is 40:Na2O:Al2O3:200:SiO2:800:H2O. 5.6g of silicon powder was mixed with 0.21g of sodium carbonate, followed by the addition of 0.67g of aluminum sulfate 18-hydrate, 3.2g of sodium hydroxide, and 14.1g of water, forming an initial gel. Finally, 1.51g of structure-directing agent 6 was added and stirred at 35°C for 3 hours to form a gel. The molar ratio of SiO2 to sodium carbonate in the silicon powder was 100:1. The gel was transferred to a polytetrafluoroethylene (PTFE) liner and crystallized at 120°C for 12 hours. The gel was then filtered, washed to neutrality, dried at 90°C, and calcined at 400°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0082] Example 10

[0083] Calculated as oxides, the molar ratio of the alkali source, aluminum source, and silicon source is Na2O:Al2O3:SiO2:10H2O. After uniformly mixing 2.8g of silicon powder with 0.53g of sodium carbonate, 10.2g of aluminum oxide, 4g of sodium hydroxide, and 18g of water are added sequentially and stirred to form an initial gel. Finally, 1.84g of structure-directing agent 5 is added and stirred at 35°C for 3 hours to form a gel. The molar ratio of SiO2 to sodium carbonate in the silicon powder is 100:5. The gel is transferred to a polytetrafluoroethylene-lined container and crystallized at 120°C for 12 hours. The resulting mixture is then filtered, washed to neutrality, dried at 90°C, and calcined at 600°C for 8 hours to obtain a hierarchical pore Y-type molecular sieve.

[0084] Comparative Example 1

[0085] 46.75g of water glass was mixed with 10.5g of aluminum sulfate 18-hydrate and 23.75g of water and stirred thoroughly. 10.64g of high-alkali solution 3 was then added and stirred thoroughly to form an initial gel. Finally, 7.4g of structure-directing agent 1 was added and stirred at 35°C for 3 hours to form a gel. The gel was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 24 hours. The mixture was then filtered, washed with water until neutral, dried at 90°C, and calcined at 550°C for 10 hours to obtain a conventional Y-type molecular sieve.

[0086] Comparative Example 2

[0087] 46.75g of water glass was mixed with 10.5g of aluminum sulfate 18-hydrate and 23.75g of water and stirred thoroughly. 10.64g of high-alkali solution 2 was then added and stirred thoroughly to form an initial gel. 3.4g of mesoporous template TPHAC was then added, and finally 7.4g of structure-directing agent 1 was added and stirred at 35°C for 3 hours to form a gel. The gel was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 24 hours. The mixture was then filtered, washed with water until neutral, dried at 90°C, and calcined at 550°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0088] The pore structure parameters of the Y-type molecular sieves prepared in the above embodiments and comparative examples are listed in Table 1.

[0089] Table 1 Comparison of pore structure parameters of examples and comparative examples

[0090]

[0091]

[0092] Note: S total Total specific surface area; S mic Micropore specific surface area; S ext External specific surface area; V meso The specific volume of mesopores (the difference between the total pore volume and the micropore volume).

[0093] The results in the table above demonstrate that the multi-level pore Y-type molecular sieves provided by the present invention all possess abundant mesoporous specific surface area. Compared to existing mesoporous Y-type molecular sieves synthesized using organic templates, the multi-level pore Y-type molecular sieves synthesized using inorganic additives / carbonates have a higher specific surface area and larger pore volume, which facilitates mass and heat transfer between reactants and products.

[0094] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a multi-level pore Y-type molecular sieve, characterized in that: The steps include: A silicon source, an aluminum source, an alkali source, a carbonate and a Y-type molecular sieve structure directing agent are mixed to form a gel, and the gel is subjected to hydrothermal crystallization, separation, washing and calcination to obtain the multi-level pore Y-type molecular sieve; Wherein, the molar ratio of SiO2 in the silicon source to the carbonate is 100:1-15; The alkali source can be selected from sodium hydroxide and / or a high alkali solution. The preparation of the high alkali solution comprises the following steps: heating an aqueous solution of sodium hydroxide, adding aluminum hydroxide powder and stirring until dissolved, thereby obtaining the high alkali solution.

2. The method for preparing a multi-level pore Y-type molecular sieve according to claim 1, wherein: After mixing the silicon source and the carbonate, the aluminum source and the alkali source are added, and finally the Y-type molecular sieve structure directing agent is added; or After the silicon source and the aluminum source are mixed, the carbonate and the alkali source are added, and finally the Y-type molecular sieve structure directing agent is added.

3. The method for preparing a multi-level pore Y-type molecular sieve according to claim 2, wherein: The temperature for forming gel is 25-50°C and the time is 1-5 hours.

4. The method for preparing a multi-level pore Y-type molecular sieve according to claim 1, wherein: The molar ratio of each component in the Y-type molecular sieve structure directing agent, calculated as oxide, is: (1-30) Na2O:Al2O3:(1-40)SiO2:(200-800)H2O.

5. The method for preparing a multi-level pore Y-type molecular sieve according to claim 4, wherein: The preparation of the Y-type molecular sieve structure directing agent comprises the following steps: mixing a silicon source, an aluminum source, an inorganic base and water and then aging; preferably, the aging temperature is 25-80° C. and the aging time is 12-36 hours.

6. The method for preparing a multi-level pore Y-type molecular sieve according to claim 1, wherein: Calculated as oxides, the molar ratio of the components of the alkali source, the aluminum source and the silicon source in the gel is (0.1-80) Na2O:Al2O3:(1-200)SiO2:(10-800)H2O.

7. The method for preparing a multi-level pore Y-type molecular sieve according to claim 1, wherein: The molar ratio of each component in the high alkaline solution is (10-15) Na2O:Al2O3:(100-200)H2O in terms of oxides.

8. The method for preparing a multi-level pore Y-type molecular sieve according to claim 7, wherein: The aqueous solution of sodium hydroxide further contains sodium carbonate. The molar ratio of the aluminum hydroxide powder, calculated as aluminum oxide, to the sodium carbonate is ≤5.

9. The method for preparing a multi-level pore Y-type molecular sieve according to claim 1, wherein: The hydrothermal crystallization temperature is 90-150° C. and the time is 12-48 hours; and / or The calcination temperature is 400-600° C. and the calcination time is 6-10 hours.

10. The method for preparing a multi-level pore Y-type molecular sieve according to claim 1, wherein: The silicon source is selected from one or more of water glass, ethyl orthosilicate and silicon powder; The aluminum source is selected from one or more of aluminum sulfate 18hydrate, aluminum oxide, aluminum chloride, aluminum isopropoxide and high alkaline solution; The carbonate is selected from one or more of sodium carbonate, potassium carbonate and ammonium carbonate.

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