A method for preparing high-silicon multi-level pore Y-type molecular sieve

Abstract

The present invention relates to a method for preparing a high-silicon multi-level pore Y-type molecular sieve, comprising: mixing sodium hydroxide, a first silicon source, a first aluminum source, and deionized water and stirring them uniformly, allowing them to age statically to obtain a Y-type molecular sieve structure directing agent; mixing a second silicon source, a second aluminum source, a sodium-containing alkali solution, and water and stirring them uniformly to form a gel, then reinforcing an oxidant, a carbonate, and a Y-type molecular sieve structure directing agent, stirring to form a mixed component; transferring the mixed component to a polytetrafluoroethylene liner, crystallizing, filtering, washing, drying, and calcining to obtain a high-silicon multi-level pore Y-type molecular sieve. The method for preparing a high-silicon multi-level pore Y-type molecular sieve of the present invention can adopt environmentally friendly technical means without ammonia nitrogen emission pollution, realize the introduction of in-situ generated mesopores into microporous molecular sieves, and can avoid the defects of large diffusion resistance, low active site utilization, and easy carbon deposition and deactivation in the catalytic cracking process caused by the molecular sieve pore structure, thereby being used as a catalyst support material.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve preparation, and in particular relates to a method for preparing a high-silicon multi-level pore Y-type molecular sieve. Background Art

[0002] Y-type molecular sieve is a faujasite (FAU)-type molecular sieve with a three-dimensional twelve-membered ring pore system and a large pore volume, as well as strong acidity and high hydrothermal stability. Due to its unique structural characteristics and performance advantages, Y-type molecular sieve is widely used in fields such as FCC and gas adsorption separation. However, its inherent microporous structure hinders the internal diffusion of macromolecular reactants and the external diffusion of products, resulting in secondary reactions, carbon deposition, and deactivation of the molecular sieve.

[0003] The introduction of mesopores into microporous molecular sieves can effectively solve the problems of high diffusion resistance, low utilization of active sites, and easy carbon deposition and deactivation in the catalytic cracking process of microporous molecular sieves. Therefore, the introduction of mesopores is of great help to their industrial application.

[0004] Patent CN107973312A discloses a mesoporous Y molecular sieve and its preparation method. This patent involves subjecting a NaY molecular sieve to two ammonium exchanges and hydrothermal treatments, as well as acid and alkali treatments, to produce a mesoporous Y molecular sieve. This method uses a large amount of acid and alkali for post-treatment and involves numerous steps, which is detrimental to its industrial development.

[0005] Valtchev et al. (Angewandte Chemie International Edition, 2016, 55: 15049-15052) used NH4F as a mineralizer to break the Si-O and Al-O bonds in the molecular sieve framework, producing a rectangular multi-level pore mosaic structure. HF and HF-2 produced by NH4F hydrolysis and secondary hydrolysis extract silicon and aluminum atoms from the framework at the same rate. The molecular sieve framework and the crystals that grow and connect to each other are bound by F. - With the increase of etching time, these structures transform into highly interconnected mesopores.

[0006] Zhao et al. (Microporous and Mesoporous Materials, 2018, 264:92-103) introduced TPHAC into an aluminosilicate sol to form an organically modified sol. After aging, this sol served as the SDA in the raw gel, generating well-aligned hierarchical NaY aggregates. This method not only used organic materials as templates, causing some pollution, but also took a long time to crystallize, making it unsuitable for industrial production.

[0007] Patent CN106927479A discloses a method for preparing mesoporous Y-type molecular sieves, which includes: (1) mixing a silicon source, an aluminum source, and water, and aging for 0.2-40 hours to obtain a directing agent; (2) mixing the silicon source and the directing agent, then adding an aluminum source and water, and crystallizing for 15-20 hours 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 organic polyacrylamide as a template. The use of organic matter has certain environmental pollution, and the crystallization process is cumbersome and time-consuming, which is not conducive to large-scale production and application. Zhao et al. (Catalysis Communications, 2016, 73:98-102) used P123 block copolymer as a template and synthesized mesoporous molecular sieve Y by hydrothermal synthesis. When evaluating the microactivity of the catalyst, the results showed that the microactivity of the Meso-CAT-3 catalyst was higher and the coke yield was the lowest. This is attributed to the fact that the mesoporous structure can improve the mass transfer of macromolecules. However, this method requires the use of P123 as a template, which is not environmentally friendly. Choi et al. (Nature Materials, 2006, 5 (9): 718-723) obtained 3-(trimethoxysilyl)propyl hexadecyldimethylammonium chloride (TPHAC) by combining traditional surfactants with organosilanes. The hydrolyzed methoxy groups are stably connected to the silicon-aluminum species through covalent bonds, effectively improving the occurrence of phase separation. Adjusting the length of the hydrophobic alkyl chain can correspondingly change the size of the mesoporous channels. Shen et al. (Chemical Communications, 2014, 50 (20): 2660-2663) successfully prepared a multi-level pore Y-type molecular sieve with adjustable pore size by introducing Fe cations into the NaY molecular sieve framework as unstable sites, and then performing ammonium ion exchange and water vapor deferrification and dealumination treatment in sequence. The ultra-stable Y-type molecular sieve (USY) obtained by water vapor treatment after the introduction of iron atoms Fe ) Compared with the USY molecular sieve obtained by ordinary hydrothermal treatment, the acidity is increased by 53%. It is also found that with the increase of iron content in the framework, the mesopore size obtained after steam treatment reaches 8-50nm. In the macromolecular catalytic cracking of 1,3,5-triisopropylbenzene, as the operation time increases, the mesopore-enriched USY Fe It has higher activity and longer service life than USY. FeThe product will contain some iron, which is easy to form "iron nodules" during the actual catalytic cracking process, making the product fluidization worse and the heavy oil conversion capacity decreased. Yu et al. (Journal of Materials Chemistry A, 2016, 4 (39): 14978-14982; ChemSusChem, 2018, 11 (21): 3812-3820) introduced a small amount of molecular sieve seeds when preparing SAPO-34 molecular sieves. During the synthesis process, some of the seeds dissolved into fragments, and the growth material epitaxially crystallized on the surface of the fragments, forming a multi-level pore structure of interconnected mesopores and macropores. However, the seed-assisted method still faces challenges in the preparation of multi-level pore molecular sieves with adjustable mesopores / macropores. There is no universal scientific mechanism to explain how to accurately guide the seeds to form a hierarchical structure. Feng et al. (Journal of the American Chemical Society, 2018, 140: 4770-4773) used chemical or physical methods to generate hydroxyl radicals in the synthesis system of mesoporous molecular sieve SBA-15 instead of inorganic acid, and used its strong oxidizing property to catalyze the hydrolysis and polymerization of silicon-oxygen-silicon bonds to prepare high-quality products. However, expensive ethyl orthosilicate was used in the synthesis process, and the acidity of the product was low. Miao et al. (Microporous and Mesoporous Materials, 2019, 289: 109640) prepared Cu-SBA-15 by adding sodium persulfate as a hydroxyl radical initiator and using Cu(NO3)2 as a copper source. The synthesized product has good catalytic activity for the oxidative degradation of organic dyes. However, expensive silicon sources and templates still limit its large-scale industrial application. Sodium persulfate has weak oxidizing properties and is not the best hydroxyl radical initiator. Yu et al. (Science, 2016, 351:1188-1191) reported that hydroxyl radicals significantly promote the depolymerization of Si-O-Si bonds in the synthetic gel and the repolymerization of Si-O-Si bonds in the silicon species during the crystallization process of the molecular sieve, thereby accelerating the nucleation of the molecular sieve. Based on this, they utilized a free radical route to synthesize highly ordered mesoporous silica in an acid-free system. While these reports suggest that hierarchical Y-type molecular sieves overcome the shortcomings of their pore structure, further research is needed to improve their environmental friendliness.

[0008] Patent CN104760973A discloses a Y-type molecular sieve with an ultra-high mesoporous content and its preparation method. The method comprises: pretreating Y-type zeolite at 300-600°C for 1-5 hours, cooling the temperature to 200-600°C, introducing a dry gas saturated with a dealuminated siliconizing agent into the pretreated Y-type zeolite in an anhydrous dry environment, and reacting for 0.5-7 hours to obtain a crude product; or, while uniformly heating the temperature to 250-700°C in an anhydrous dry environment, introducing a dry gas saturated with a dealuminated siliconizing agent into the pretreated Y-type zeolite for 0.5-7 hours to obtain a crude product; the introduction rate of the dealuminated siliconizing agent-saturated dry gas is 50 mL / min; acid-treating the crude product; and alkaline-treating the acid-treated crude product to obtain a multi-level pore Y-type molecular sieve. The patent requires high temperatures and extensive acid and alkali treatments during the production process, which is not conducive to industrial application. Schmidt et al. (Chemistry of Materials, 2001, 13(12): 4416-4418) first used porous-walled carbon nanotubes (12 nm in diameter and several microns in length) to prepare Silicalite-1 molecular sieves with thin, straight, and uniform multi-level pores. The crystal size is limited by the diameter of the carbon nanotubes, so the controllable pore size distribution of the multi-level pore molecular sieve can be achieved by adjusting the size and size of the carbon nanomaterial. However, the cost of carbon nanomaterials has limited their industrial application. Huang et al. (Microporous and Mesoporous Materials, 2010, 127: 167-175) used a three-stage temperature control method to synthesize well-crystallized multi-level pore NaY nanocrystals through three stages of crystallization at different temperatures without adding any organic additives, pore-forming agents, or crystal seeds. However, this method takes a long time during the synthesis process, which is not conducive to widespread application. Wang et al. (Angewandte Chemie International Edition, 2020, 59:1-5) reported a hydroxyl radical and post-treatment-assisted method for the synthesis of high-silicon Y-type molecular sieves. This method uses hydroxyl radicals to promote the depolymerization of Si-O-Si bonds in the gel and the repolymerization of Si-O-Si bonds in the silicon material, thereby accelerating nucleation. After treatment with citric acid, aluminum in the framework and non-framework aluminum are removed to obtain high-silicon Y. However, its crystallization time is long, and the use of citric acid and subsequent secondary crystallization under alkaline conditions are not friendly to industrialization. Summary of the Invention

[0009] In view of the defects of the above-mentioned technology, the purpose of the present invention is to propose a method for preparing a high-silicon multi-level pore Y-type molecular sieve, which can adopt environmentally friendly technical means without ammonia nitrogen emission pollution to introduce in situ generated mesopores into the microporous molecular sieve, and can avoid the defects of the molecular sieve pore structure causing large diffusion resistance, low active site utilization and easy carbon deposition and deactivation in the catalytic cracking process, so that it can be used as a catalyst support material.

[0010] To achieve the above object, the present invention provides a method for preparing a high-silicon multi-level pore Y-type molecular sieve, the method comprising the following steps:

[0011] (1) Preparation of a structure directing agent: Sodium hydroxide, a first silicon source, a first aluminum source, and deionized water are mixed and stirred uniformly, and then aged to obtain a Y-type molecular sieve structure directing agent; wherein the sodium hydroxide is calculated as Na2O, the first silicon source is calculated as SiO2, and the first aluminum source is calculated as Al2O3, and the molar ratio of each component in the Y-type molecular sieve structure directing agent is (5-30) Na2O:Al2O3:(5-40)SiO2:(200-800)H2O;

[0012] (2) Preparation of molecular sieve: The second silicon source, the second aluminum source, the sodium-containing alkali solution and water are mixed and stirred evenly to form a gel, and then the oxidant, carbonate and Y-type molecular sieve structure directing agent are strengthened and stirred to form a mixed component; the mixed component is transferred to a polytetrafluoroethylene liner, crystallized, filtered, washed, dried and calcined to obtain a high-silicon multi-level pore Y-type molecular sieve; wherein the second silicon source is calculated as SiO2, the second aluminum source is calculated as Al2O3, and the sodium-containing alkali solution is calculated as Na2O, and the molar ratio of each component in the gel is (2-80)Na2O:Al2O3:(2-200)SiO2:(10-800)H2O.

[0013] Preferably, in step (2), the sodium-containing alkali solution is sodium hydroxide or a high-alkali solution; the high-alkali solution is prepared by mixing sodium hydroxide, sodium aluminate and water and stirring until dissolved; wherein sodium hydroxide is calculated as Na2O and sodium aluminate is calculated as Al2O3, and in the high-alkali solution, the molar ratio of sodium hydroxide, sodium aluminate and water is (10-15)Na2O:Al2O3:(100-200)H2O, preferably (10-13)Na2O:Al2O3:(100-160)H2O.

[0014] Preferably, the first aluminum source or the second aluminum source is selected from at least one of aluminum sulfate 18hydrate, aluminum oxide, aluminum chloride, and aluminum isopropoxide; the first silicon source or the second silicon source is selected from at least one of water glass, ethyl orthosilicate, and silicon powder.

[0015] Preferably, in step (2), the carbonate is selected from at least one of sodium carbonate, potassium carbonate, and ammonium carbonate, preferably sodium carbonate; the amount of the carbonate added is 1-15%, preferably 1-10%, of the molar amount of SiO2 added in the gel; the carbonate is added after the gel is formed or during the gel formation process, that is, the preparation process of the mixed component can be: the second silicon source, the second aluminum source, the sodium-containing alkali solution, and water are mixed and stirred to form a gel, and then the oxidant, carbonate, and Y-type molecular sieve structure directing agent are strengthened and stirred to form a mixed component, or it can be: the second silicon source, the second aluminum source, the sodium-containing alkali solution, carbonate, and water are mixed and stirred to form a gel, and then the oxidant and Y-type molecular sieve structure directing agent are strengthened and stirred to form a mixed component.

[0016] Preferably, in step (2), the strong oxidant is sodium persulfate; the amount of the strong oxidant added is 1-5%, preferably 2-5%, of the molar amount of SiO2 added in the gel.

[0017] The addition of sodium persulfate accelerates the breaking and formation of Si-O-Si bonds, further facilitating the introduction of carbonates into the molecular sieve framework. By combining carbonates with an inorganic directing agent, the carbonates are introduced into the molecular sieve framework. The resulting product undergoes a calcination process, where the association of carbonates with the framework's silica and alumina species removes the silica and alumina, leading to the in-situ formation of mesopores. Furthermore, the amount of aluminum removed is significantly greater than that of silicon, enabling the in-situ preparation of highly silicate mesoporous Y-type molecular sieves.

[0018] Preferably, in step (1), the temperature of the static aging is 25-80°C, preferably 25-60°C, and the static aging time is 12-36h, preferably 12-20h.

[0019] Preferably, in step (1), the molar ratio of the components in the Y-type molecular sieve structure directing agent is (5-20) Na2O:Al2O3:(5-20)SiO2:(200-400)H2O.

[0020] Preferably, in step (2), the molar ratio of the components in the gel is (2-30) Na2O:Al2O3:(2-20)SiO2:(50-400)H2O.

[0021] Preferably, in step (2), the stirring temperature is 25-50°C, and the time is 1-5h; the crystallization temperature is 90-150°C, preferably 95-120°C, and the time is 12-24h, preferably 12-20h; the calcination temperature is 400-600°C, and the time is 6-10h.

[0022] Beneficial effects of the present invention:

[0023] Beneficial effect 1: The present invention uses carbonate to achieve the preparation of multi-level pore Y-type molecular sieves, and the use of hydroxyl radicals in the formation process of the molecular sieve framework is more conducive to the introduction of carbonates.

[0024] Beneficial Effect 2: The association between carbonate and the silica-alumina species of the skeleton is used to remove silica and aluminum, thereby achieving in-situ formation of mesopores. This overcomes the pollution problem caused by organic templates and greatly reduces costs.

[0025] Beneficial effect 3: From the characterization results in Table 1, it can be seen that the high-silicon multi-level pore Y-type molecular sieve synthesized with the assistance of hydroxyl radicals / carbonate has a higher specific surface area and larger pore volume than the Y molecular sieve synthesized with a template agent, which is beneficial to the mass transfer and heat transfer of reactants and products. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the X-ray diffraction spectrum of the multi-level pore Y-type molecular sieve obtained in Example 1 of the present invention.

[0027] Figure 2 This is a graph showing the N2 adsorption and desorption curves of the multi-level pore Y-type molecular sieve obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The following examples of the present invention are described in detail. These examples are based on the technical solutions of the present invention and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following examples. Experimental methods in the following examples where specific conditions are not specified are generally based on conventional conditions. The experimental methods described in the following examples are all conventional methods unless otherwise specified. The reagents and compounds described are all commercially available unless otherwise specified.

[0029] Source of raw materials: Aluminum sulfate and other raw materials are from China Petroleum Lanzhou Petrochemical Company, all of which are industrial products; template agent is purchased from Anhui Jinao Chemical Co., Ltd., which is an industrial product; sodium carbonate, sodium persulfate, etc. are all commercially available reagents, industrial grade.

[0030] 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. Sample testing conditions: scanning angle 5-40°, scanning speed 6° / min.

[0031] The adsorption-desorption isotherms of the samples were measured at liquid nitrogen temperature using an 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.

[0032] Synthesis of structure-directing agent 1:

[0033] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water, and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 5Na2O:Al2O3:5SiO2:200H2O, and then aged at 60°C for 16 hours to obtain a structure directing agent 1.

[0034] Synthesis of structure-directing agent 2:

[0035] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 16Na2O:Al2O3:15SiO2:320H2O, and then aged at 35°C for 16 hours to obtain structure directing agent 2.

[0036] Synthesis of structure-directing agent 3:

[0037] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 16Na2O:Al2O3:15SiO2:320H2O, and then aged at 25°C for 20 hours to obtain structure directing agent 3.

[0038] Synthesis of structure-directing agent 4:

[0039] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 20Na2O:Al2O3:20SiO2:400H2O, and then aged at 45°C for 12 hours to obtain structure directing agent 4.

[0040] Synthesis of structure-directing agent 5:

[0041] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 5Na2O:Al2O3:5SiO2:200H2O, and then aged at 50°C for 20 hours to obtain structure directing agent 5.

[0042] Synthesis of structure-directing agent 6:

[0043] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 30Na2O:Al2O3:40SiO2:800H2O, and then aged at 60°C for 24 hours to obtain structure directing agent 6.

[0044] Synthesis of structure-directing agent 7:

[0045] Calculated on the basis of oxides, water glass, aluminum oxide, deionized water and sodium hydroxide were mixed and stirred uniformly in a molar ratio of 20Na2O:Al2O3:20SiO2:200H2O, and then aged at 25°C for 12 hours to obtain structure directing agent 7.

[0046] Preparation of sodium lye 1:

[0047] Sodium hydroxide, sodium metaaluminate and water are mixed and stirred until completely dissolved to obtain a sodium-containing alkali solution 1 with a molar ratio of 10Na2O:1Al2O3:150H2O.

[0048] Preparation of sodium lye 2:

[0049] Sodium hydroxide, sodium metaaluminate and water are mixed and stirred until completely dissolved to obtain a sodium-containing alkali solution 2 with a molar ratio of 15 Na2O:Al2O3:200 H2O.

[0050] Preparation of sodium lye 3:

[0051] Sodium hydroxide, sodium metaaluminate and water are mixed and stirred until completely dissolved to obtain a sodium-containing alkali solution 3 with a molar ratio of 10Na2O:Al2O3:100H2O.

[0052] Example 1

[0053] 20.83g of ethyl orthosilicate and 1.15g of ammonium carbonate were mixed and stirred uniformly at a molar ratio of 30Na2O:Al2O3:20SiO2:400H2O. Then, 1.33g of aluminum chloride, 36g of water, and 12g of sodium hydroxide were added and stirred uniformly to form a gel. 0.238g of sodium persulfate was then added, and finally, 3.5g of structure-directing agent 1 was added and stirred at 50°C for 1 hour to obtain a mixed component. The amount of ammonium carbonate added was 12% of the molar amount of SiO2 in the gel. The amount of sodium persulfate added was 1% of the molar amount of SiO2 in the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 120°C for 24 hours. The mixture was then filtered, washed, dried, and calcined at 600°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0054] Example 2

[0055] 46.75g of water glass and 4g of sodium carbonate were mixed and stirred uniformly at a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O. Then, 10.5g of aluminum sulfate 18hydrate, 23.75g of water, and 10.64g of sodium-containing alkali solution 1 were added and stirred uniformly to form a gel. 0.98g of sodium persulfate was then added, and finally 7.4g of structure-directing agent 2 was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of sodium carbonate added was 13% of the molar amount of SiO2 in the gel. The amount of sodium persulfate added was 3% of the molar amount of SiO2 in the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 12 hours. The mixture was then filtered, washed, dried, and calcined at 550°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0056] Example 3

[0057] 4.16g of ethyl orthosilicate, 1.02g of aluminum oxide, 9g of water, and 1.6g of sodium hydroxide were mixed and stirred uniformly in a molar ratio of 2Na2O:Al2O3:2SiO2:50H2O to form a gel. 0.03g of potassium carbonate was then added and stirred uniformly. 0.24g of sodium persulfate was then added, and finally 0.79g of structure-directing agent 2 was stirred at 25°C for 3 hours to obtain a mixed component. The amount of potassium carbonate added was 1% of the molar amount of SiO2 in the gel. The amount of sodium persulfate added was 5% of the molar amount of SiO2 in the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 95°C for 15 hours. The mixture was then filtered, washed, dried, and calcined at 400°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0058] Example 4

[0059] 5.04g of silicon powder and 1.21g of ammonium carbonate were mixed and stirred uniformly at a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O. Then, 2.67g of aluminum chloride, 36g of water, and 2.28g of sodium hydroxide were added and stirred uniformly to form a gel. 0.98g of sodium persulfate was then added, and finally 2.30g of structure-directing agent 3 was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of ammonium carbonate added was 15% of the molar amount of SiO2 in the gel. The amount of sodium persulfate added was 5% of the molar amount of SiO2 in the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 24 hours. The mixture was then filtered, washed, dried, and calcined at 600°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0060] Example 5

[0061] 5.04g of silicon powder, 4.08g of aluminum isopropoxide, 36g of water, and 1.6g of sodium hydroxide were mixed and stirred uniformly at a molar ratio of 2Na2O:Al2O3:8.4SiO2:200H2O to form a gel. 1.34g of sodium carbonate was then added and stirred uniformly. 0.4g of sodium persulfate was then added, and finally 2.34g of structure-directing agent 4 was stirred at 35°C for 3 hours to obtain a mixed component. The amount of sodium carbonate added was 15% of the molar amount of SiO2 in the gel. The amount of sodium persulfate added was 2% of the molar amount of SiO2 in the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 150°C for 20 hours. The mixture was then filtered, washed, dried, and calcined at 500°C for 8 hours to obtain a hierarchical pore Y-type molecular sieve.

[0062] Example 6

[0063] 25.65g of water glass, 4.08g of aluminum isopropoxide, 17g of water, and 2.28g of sodium hydroxide were mixed and stirred uniformly at a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O to form a gel. 1.74g of potassium carbonate was then added and stirred uniformly. Then, 1.6g of sodium persulfate was added, and finally, 2.34g of structure-directing agent 5 was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of potassium carbonate added was 15% of the molar amount of SiO2 added to the gel. The amount of sodium persulfate added was 4% of the molar amount of SiO2 added to the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 100°C for 15 hours. The mixture was then filtered, washed, dried, and calcined at 500°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0064] Example 7

[0065] 3g of silicon powder was mixed with 6.7g of aluminum sulfate 18-hydrate, 1.6g of sodium hydroxide, and 1.8g of water in a molar ratio of 2Na2O:Al2O3:5SiO2:10H2O, stirring uniformly to form a gel. 0.048g of ammonium carbonate was then added and stirred uniformly. Then, 0.6g of sodium persulfate was added, and finally, 0.66g of structure-directing agent 6 was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of ammonium carbonate added was 1% of the molar amount of SiO2 added to the gel. The amount of sodium persulfate added was 5% of the molar amount of SiO2 added to the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 120°C for 12 hours. The mixture was then filtered, washed, dried, and calcined at 600°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0066] Example 8

[0067] 46.75g of water glass, 10.5g of aluminum sulfate 18-hydrate, and 23.75g of water were mixed and stirred uniformly in a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O. 10.64g of sodium-containing alkali solution 2 was then added and stirred uniformly to form a gel. 4g of sodium carbonate and 0.98g of sodium persulfate were then added. Finally, 7.4g of structure-directing agent 1 was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of sodium carbonate added was 13% of the molar amount of SiO2 in the gel. The amount of sodium persulfate added was 3% of the molar amount of SiO2 in the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 150°C for 24 hours. The mixture was then filtered, washed, dried, and calcined at 550°C for 7 hours to obtain a conventional Y-type molecular sieve.

[0068] Example 9

[0069] 12g of silicon powder and 0.27g of potassium carbonate were mixed and stirred uniformly at a molar ratio of 80Na2O:Al2O3:200SiO2:800H2O. 0.67g of aluminum sulfate 18hydrate, 6.4g of sodium hydroxide, and 14.4g of water were then added sequentially and stirred to form a gel. 2.38g of sodium persulfate was then added, and finally 1.67g of structure-directing agent 7 was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of potassium carbonate added was 1% of the molar amount of SiO2 added to the gel. The amount of sodium persulfate added was 5% of the molar amount of SiO2 added to the gel. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 120°C for 12 hours. The mixture was then filtered, washed, dried, and calcined at 550°C for 6 hours to obtain a hierarchical pore Y-type molecular sieve.

[0070] Example 10

[0071] 46.75g of water glass, 10.5g of aluminum sulfate 18-hydrate, and 23.75g of water were mixed and stirred uniformly at a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O. 10.64g of sodium-containing alkali solution 3 was then added and stirred uniformly to form a gel. 3.26g of ammonium carbonate was then added and stirred uniformly. 7.4g of structure-directing agent 6 was then added. Finally, 1.6g of sodium persulfate was added and stirred at 35°C for 3 hours to obtain a mixed component. The amount of ammonium carbonate added was 13% of the molar amount of SiO2 added to the gel. The amount of sodium persulfate added was 5% of the molar amount of SiO2 added to the gel. The mixed component was transferred to a polytetrafluoroethylene liner and crystallized at 120°C for 15 hours. The mixture was then filtered, washed, dried, and calcined at 400°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0072] Comparative Example 1

[0073] 46.75g of water glass, 10.5g of aluminum sulfate 18-hydrate, and 23.75g of water were mixed and stirred uniformly at a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O. 10.64g of sodium-containing alkali solution 1 was added and stirred uniformly to form a gel. Finally, 7.4g of structure-directing agent 2 was added and stirred at 35°C for 3 hours to obtain a mixed component. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 12 hours. The mixture was then filtered, washed, dried, and calcined at 550°C for 10 hours to obtain a conventional Y-type molecular sieve.

[0074] Comparative Example 2

[0075] 46.75g of water glass, 10.5g of aluminum sulfate 18-hydrate, and 23.75g of water were mixed and stirred uniformly at a molar ratio of 2.85Na2O:Al2O3:8.4SiO2:200H2O. 10.64g of sodium-containing alkali solution 1 was then added and stirred uniformly to form a gel. 3.4g of mesoporous template TPHAC was then added, and finally 7.4g of structure-directing agent 2 was added and stirred at 35°C for 3 hours to obtain a mixed component. The mixed component was transferred to a polytetrafluoroethylene-lined container and crystallized at 96°C for 12 hours. The mixture was then filtered, washed, dried, and calcined at 550°C for 10 hours to obtain a hierarchical pore Y-type molecular sieve.

[0076] The multi-level pore molecular sieve prepared in the example was compared with the sample obtained in the comparative example, and the pore structure parameters thereof are listed in Table 1.

[0077] Table 1 Comparison of pore structure parameters of examples and comparative examples

[0078] sample <![CDATA[S total / m 2 ·g -1 ]]> <![CDATA[S mic / m 2 ·g -1 ]]> <![CDATA[S ext / m 2 ·g -1 ]]> <![CDATA[V meso / cm 3 ·g -1 ]]> Example 1 756 667 89 0.42 Example 2 800 673 127 0.46 Example 3 759 656 103 0.43 Example 4 773 685 88 0.42 Example 5 785 685 100 0.43 Example 6 737 628 109 0.40 Example 7 762 668 94 0.45 Example 8 774 674 100 0.45 Example 9 728 636 92 0.40 Implementation 10 750 654 96 0.41 Comparative Example 1 674 630 44 0.16 Comparative Example 2 680 576 104 0.15

[0079] As can be seen from Table 1, the multi-level pore Y-type molecular sieves synthesized in the examples all contain abundant mesoporous specific surface area. Figure 1 It can be seen that the sample exhibits characteristic diffraction peaks of Y-type molecular sieves and has good crystallinity. Figure 2 The nitrogen adsorption and desorption diagram of the sample shows that the sample has a distinct mesoporous structure. In summary, the multi-level pore Y-type molecular sieve synthesized by the method of the present invention has abundant mesopores and good crystallinity.

[0080] In summary, the present invention provides a method for preparing a high-silicon multi-level pore Y-type molecular sieve. When forming the initial framework, hydroxyl radicals accelerate the breaking and formation of Si-O-Si bonds, which is conducive to the introduction of carbonates into the molecular sieve framework. After calcination, the product is used to remove silicon and aluminum by the association of carbonate ions with the framework silicon and aluminum species, thereby achieving in-situ generation of mesopores. At the same time, the amount of aluminum species removed is much greater than the amount of silicon species removed, thereby achieving in-situ preparation of a high-silicon mesoporous Y-type molecular sieve. This largely solves the pollution problem caused by using organic matter as a mesoporous template.

[0081] 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 present invention.

Claims

1. A method for preparing a high-silicon multi-level pore Y-type molecular sieve, characterized in that: The following steps are involved: (1) Preparation of a structure directing agent: Sodium hydroxide, a first silicon source, a first aluminum source, and deionized water are mixed and stirred uniformly, and then aged to obtain a Y-type molecular sieve structure directing agent; wherein sodium hydroxide is calculated as Na2O, the first silicon source is calculated as SiO2, and the first aluminum source is calculated as Al2O3, and the molar ratio of each component in the Y-type molecular sieve structure directing agent is (5-30)Na2O: Al2O3: (5-40)SiO2: (200-800)H2O; (2) Preparation of molecular sieve: The second silicon source, the second aluminum source, the sodium-containing alkali solution and water are mixed and stirred to form a gel, and then the oxidant, carbonate and Y-type molecular sieve structure directing agent are strengthened and stirred to form a mixed component; the mixed component is transferred to a polytetrafluoroethylene liner, crystallized, filtered, washed, dried and calcined to obtain a high-silicon multi-level pore Y-type molecular sieve; wherein the second silicon source is calculated as SiO2, the second aluminum source is calculated as Al2O3, and the sodium-containing alkali solution is calculated as Na2O, and the molar ratio of each component in the gel is (2-80)Na2O: Al2O3: (2-200)SiO2: (10-800)H2O; Wherein, in step (2), the carbonate is selected from at least one of sodium carbonate, potassium carbonate, and ammonium carbonate, and the strong oxidant is sodium persulfate.

2. The preparation method according to claim 1, characterized in that In step (2), the sodium-containing alkali solution is sodium hydroxide or a high-alkali solution; the high-alkali solution is prepared by mixing sodium hydroxide, sodium aluminate and water and stirring until dissolved; wherein sodium hydroxide is calculated as Na2O and sodium aluminate is calculated as Al2O3, and in the high-alkali solution, the molar ratio of sodium hydroxide, sodium aluminate and water is (10-15)Na2O: Al2O3: (100-200)H2O.

3. The preparation method according to claim 2, characterized in that In the high alkaline solution, the molar ratio of sodium hydroxide, sodium aluminate and water is (10-13)Na2O: Al2O3: (100-160)H2O.

4. The preparation method according to claim 1, characterized in that The first aluminum source or the second aluminum source is selected from at least one of aluminum sulfate 18hydrate, aluminum oxide, aluminum chloride, and aluminum isopropoxide; the first silicon source or the second silicon source is selected from at least one of water glass, ethyl orthosilicate, and silicon powder.

5. The preparation method according to claim 1, characterized in that In step (2), the carbonate is selected from sodium carbonate; The amount of carbonate added is 1-15% of the molar amount of SiO2 added in the gel; The carbonate is added after the gel is formed or during the gel formation process.

6. The preparation method according to claim 5, characterized in that The amount of carbonate added is 1-10% of the molar amount of SiO2 added in the gel.

7. The preparation method according to claim 1, characterized in that In step (2), the amount of the strong oxidant added is 1-5% of the molar amount of SiO2 added in the gel.

8. The preparation method according to claim 7, characterized in that In step (2), the amount of the strong oxidant added is 2-5% of the molar amount of SiO2 added in the gel.

9. The preparation method according to claim 1, characterized in that In step (1), the static aging temperature is 25-80° C., and the static aging time is 12-36 h.

10. The preparation method according to claim 9, characterized in that In step (1), the static aging temperature is 25-60° C., and the static aging time is 12-20 h.

11. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of each component in the Y-type molecular sieve structure directing agent is (5-20)Na2O: Al2O3: (5-20)SiO2: (200-400)H2O.

12. The preparation method according to claim 1, characterized in that In step (2), the molar ratio of the components in the gel is (2-30)Na2O: Al2O3: (2-20)SiO2: (50-400)H2O.

13. The preparation method according to claim 1, characterized in that In step (2), the stirring temperature is 25-50°C and the time is 1-5 hours; the crystallization temperature is 90-150°C and the time is 12-24 hours; the calcination temperature is 400-600°C and the time is 6-10 hours.

14. The preparation method according to claim 13, characterized in that In step (2), the crystallization temperature is 95-120°C and the crystallization time is 12-20 h.

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