EMT molecular sieve, preparation method and application thereof
Patent Information
- Application Number
- CN202510266720.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-07
- Publication Date
- 2026-09-08
AI Technical Summary
[0006]综上所述，虽然现有技术中公开了多种EMT分子筛的制备方法，但是鲜有公开通过导向剂法合成EMT分子筛
（1）本发明方法在EMT分子筛合成过程中，首先制备出适宜组成的导向剂，然后通过向分子筛母液中引入导向剂，利用导向剂中高活性的EMT晶核的诱导作用促进EMT分子筛的成核过程，在避免价格昂贵18-冠醚-6模板剂的使用，同时有效提高EMT分子筛的结晶度；
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Figure CN122704933A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of molecular sieve synthesis and relates to an EMT molecular sieve and its preparation method. Background Technology
[0002] EMT molecular sieves are hexagonal octahedral molecular sieves with two sets of intersecting cavities connected by two-dimensional intersecting channels. This makes their acidic sites highly accessible. Compared to Y molecular sieves, EMT molecular sieves have a slightly higher silica-to-alumina ratio, but they have more acidic sites and higher acid strength, making them promising for applications in isomerization and alkylation processes. Furthermore, the abundant pore structure of EMT molecular sieves gives them great potential for adsorption applications. For example, in the preparation of polyolefins, EMT molecular sieves show better performance than traditional NaX molecular sieves in removing trace amounts of methanol and propionaldehyde polar oxides from olefins. EMT molecular sieves also show certain advantages in replacing activated alumina as a regenerator for hydrogen peroxide working fluids. However, the synthesis of pure-phase, highly crystallinity, and highly hydrothermal stable EMT molecular sieves is difficult. It requires the large-scale use of the highly toxic and expensive (market price around 400,000 RMB / ton) directional template agent 18-crown ether-6, and the narrow range of synthetic formulations leads to the easy formation of impurities, severely limiting the industrial application of EMT molecular sieves. Over the years, a great deal of research has been conducted on the efficient synthesis of EMT molecular sieves.
[0003] CN115959679 discloses an EMT molecular sieve and its preparation method, wherein the EMT molecular sieve is a carbon-containing EMT molecular sieve with a carbon content of 0.02-0.5 wt% and a Na2O content of less than 2.5 wt%. The preparation method of the EMT molecular sieve includes: (1) mixing an aluminum source, sodium hydroxide, a silicon source, an organic amine, and a solvent to obtain a mixture; (2) crystallizing the mixture, removing the solvent, washing with water, and dispersing it in acid after crystallization to obtain a dispersion; (3) crystallizing the dispersion, removing the solvent and washing with water after crystallization; and (4) drying and calcining to obtain the EMT molecular sieve.
[0004] CN115838179 discloses a method for preparing graded porous EMT molecular sieves with ultra-large pore volume. The specific steps involve mixing a silicon source, such as sodium silicate, silica sol, orthosilicic acid, or fumed silica, with an aluminum source, such as aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropoxide, or tert-butylaluminum, to form a gel in a specific ratio. Additional silicon and aluminum sources are then added to adjust the ratio, and the mixture is crystallized at a certain temperature for a period of time. The mixture is then separated by filtration, washed with water, and the resulting solid is dried to obtain the graded porous molecular sieve material.
[0005] CN110893337 discloses a method for preparing EMT molecular sieves. The specific steps are as follows: First, polyethylene glycol is completely dissolved in deionized water. After complete dissolution with sodium hydroxide, an aluminum source is added and stirred thoroughly to form solution A. Solution B is prepared by completely dissolving a silicon source in another portion of sodium hydroxide solution, and stirring thoroughly until a clear solution is obtained. Solutions A and B are placed in an ice-water mixture. Then, solution B is added dropwise to solution A, and stirring is continued until a homogeneous gel mixture is formed. The resulting homogeneous gel mixture is transferred to a high-pressure reactor and crystallized at a certain temperature for a period of time. After crystallization, the mixture is cooled to room temperature. The solid product is washed with deionized water, dried, and calcined to obtain the EMT molecular sieve.
[0006] In summary, although various methods for preparing EMT molecular sieves have been disclosed in the prior art, few methods for synthesizing EMT molecular sieves using directing agents have been disclosed. Summary of the Invention
[0007] To address the shortcomings of existing technologies, this invention provides an EMT molecular sieve, its preparation method, and its applications. This invention is the first to synthesize an EMT molecular sieve using a directing agent method.
[0008] The first aspect of this invention provides a method for preparing EMT molecular sieves, the method comprising the following steps: (1) Directing agent preparation: The molar ratio of each component in the directing agent is Na2O:Al2O3:SiO2:H2O = (16-19):1:(4-6):(200-400), preferably Na2O:Al2O3:SiO2:H2O = 17-18:1:4-6:250-350; (2) Molecular sieve synthesis: After uniformly mixing silicon source, aluminum source, alkali source, water and the directing agent obtained in step (1), EMT molecular sieve is obtained by crystallization, filtration, washing, drying and calcination.
[0009] In the method of the present invention, the silicon source mentioned in step (1) is at least one of sodium silicate, silica sol, water glass, tetraethyl orthosilicate and silica, with sodium silicate being more preferred.
[0010] In the method of the present invention, the alkali source in step (1) is sodium hydroxide; the aluminum source is at least one of sodium aluminate, aluminum isopropoxide, and aluminum nitrate, preferably sodium aluminate.
[0011] In the method of the present invention, the mixing temperature in step (1) can be room temperature, the mixing time is generally 12h-36h, the mixing can be carried out under stirring conditions, and the stirring speed is generally 100r / min-1000r / min.
[0012] In the method of the present invention, in step (2), the alkali source and water are first mixed evenly, then the silicon source is added, and finally the guiding agent obtained in step (1) is added to form a molecular sieve mother liquor. After being mixed evenly, the mixture is loaded into a reactor for crystallization.
[0013] In the method of the present invention, the silicon source mentioned in step (2) is at least one of silica sol, water glass, tetraethyl orthosilicate and silica, with silica sol being more preferred.
[0014] In the method of the present invention, the alkali source in step (2) is sodium hydroxide; the aluminum source is at least one of sodium aluminate, aluminum isopropoxide and aluminum nitrate, preferably sodium aluminate.
[0015] In the method of the present invention, in step (2), the components in the molecular sieve mother liquor are in the molar ratio of Na2O:Al2O3:SiO2:H2O = (1.8-2.5):1:(8-12):(100-200), preferably Na2O:Al2O3:SiO2:H2O = 2-2.4:1:9-10:140-160; the amount of the directing agent added is 2%-10% of the mass of silicon source (based on the mass of SiO2) in the directing agent, preferably 4%-5%.
[0016] In the method of the present invention, the liquid crystallization temperature of the molecular sieve mother liquid crystal in step (2) is generally 100℃-115℃, preferably 105℃-110℃, and the crystallization time is generally 5 days-10 days, preferably 7 days-8 days.
[0017] In the method of the present invention, the molecular sieve product in step (2) is subjected to solid-liquid separation by filtration and washed with water until neutral. The drying temperature is 80℃-120℃ and the drying time is 12h-24h. The calcination temperature is 500℃-600℃ and the calcination time is 3h-6h.
[0018] Furthermore, in the method of the present invention, sodium carboxymethyl cellulose (molecular weight 300-1200), preferably sodium carboxymethyl cellulose (molecular weight 300-800), can be added in step (2). The amount added is 5%-15% of the mass of the silicon source (based on SiO2) in the molecular sieve mother liquor, preferably 8%-10%. The addition of sodium carboxymethyl cellulose can significantly improve the performance of EMT molecular sieves, especially the silicon-to-aluminum ratio.
[0019] An EMT molecular sieve prepared by the above method, wherein the molecular sieve product has a typical EMT topology.
[0020] In the EMT molecular sieve of the present invention, the relative crystallinity of the EMT molecular sieve is 85%-105%, preferably 90%-100%.
[0021] In the EMT molecular sieve of the present invention, the EMT molecular sieve product exhibits a typical regular hexagonal morphology with an average particle size of 1.5μm-3.0μm, preferably 2.0μm-2.5μm.
[0022] In the EMT molecular sieve of this invention, the specific surface area of the EMT molecular sieve product is 750 m². 2 / g-900m 2 / g, preferably 830m 2 / g-870m 2 / g, total pore volume is 0.35cm³ 3 / g-0.45cm 3 / g, preferably 0.38cm 3 / g-0.42cm 3 / g.
[0023] In the EMT molecular sieve of the present invention, the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 4.5-7.5, preferably 6.0-7.0.
[0024] In the EMT molecular sieve of the present invention, based on the weight of the EMT molecular sieve product, the mass content of Na2O in the EMT molecular sieve product is 8%-13%, preferably 9%-11%.
[0025] The aforementioned EMT molecular sieves can be used in hydrocracking, isomerization, and alkylation reactions.
[0026] Compared with existing technologies, the EMT molecular sieve, its preparation method, and its applications of the present invention have the following beneficial effects: (1) In the process of EMT molecular sieve synthesis, the present invention first prepares a directing agent with a suitable composition, and then introduces the directing agent into the molecular sieve mother liquor. The induction effect of the highly active EMT crystal nuclei in the directing agent is used to promote the nucleation process of EMT molecular sieve. This avoids the use of expensive 18-crown ether-6 template agent and effectively improves the crystallinity of EMT molecular sieve. (2) By adding inexpensive and readily available carboxymethyl cellulose to the molecular sieve mother liquor, the negatively charged anions around the monomeric silicate ions are increased, the bonding rate of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra is slowed down, the bonding probability between silicon-oxygen tetrahedra, the basic structural unit of molecular sieve, is increased during the molecular sieve crystallization process, the silicon-aluminum ratio of EMT molecular sieve products is greatly improved, and its hydrothermal stability is enhanced. Attached Figure Description
[0027] Figure 1 The XRD pattern of the EMT molecular sieve synthesized in Example 1. Figure 2 SEM images of the EMT molecular sieve synthesized in Example 1. Figure 3 The XRD pattern of the EMT molecular sieve synthesized in Comparative Example 1. Figure 4 SEM images of the EMT molecular sieve synthesized in Comparative Example 1. Figure 5 The XRD pattern of the EMT molecular sieve synthesized in Comparative Example 2. Figure 6 SEM images of the EMT molecular sieve synthesized in Comparative Example 2. Figure 7 The XRD pattern of the EMT molecular sieve synthesized in Comparative Example 3. Figure 8 SEM images of the EMT molecular sieve synthesized in Comparative Example 3. Detailed Implementation
[0028] The present invention will be further described in detail below with reference to specific embodiments. The embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. In the context of the present invention, unless otherwise specified, % refers to mass percentage content.
[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.
[0030] In this invention, the morphology of the synthesized molecular sieve was determined by SEM; the crystal structure and relative crystallinity of the molecular sieve were determined by XRD characterization, and the standard sample was the molecular sieve product synthesized in Comparative Example 1 of this invention using 18-crown ether-6 as a template agent; the average particle size of the molecular sieve was determined by laser particle size analyzer; the elemental composition of the molecular sieve was determined by XRF characterization; and the pore information was obtained by nitrogen adsorption-desorption testing of the EMT molecular sieve using an ASAP 2420 automatic physical adsorption instrument at 77 K. Example 1
[0031] (1) Sodium silicate, sodium hydroxide and sodium aluminate were added to water according to the molar ratio of Na2O:Al2O3:SiO2:H2O of each component being 17:1:5:300. The mixture was stirred at 500r / min for 24h at room temperature to obtain the directing agent.
[0032] (2) According to the molecular sieve mother liquor composition, the molar ratio of Na2O:Al2O3:SiO2:H2O is 2.2:1:10:150. First, sodium hydroxide, sodium aluminate and sodium carboxymethyl cellulose (molecular weight 300-800) are added to a certain amount of water. The amount of sodium carboxymethyl cellulose added accounts for 10% of the mass of silicon source (based on SiO2 mass ratio) in the molecular sieve mother liquor. Then, 30% concentration of silica sol is added to the above solution. Finally, the directing agent obtained in step (1) is added. The amount of directing agent added is 5% of the mass of silicon source (based on SiO2 mass) in the directing agent, which accounts for 5% of the mass of silicon source (based on SiO2 mass) in the molecular sieve mother liquor. After stirring evenly, it is transferred to a polytetrafluoroethylene stainless steel reactor and statically crystallized at 110℃ for 7 days. The molecular sieve product is filtered and separated, washed with deionized water until the washing water is neutral, dried at 100℃ for 24 hours, and calcined at 550℃ for 3 hours to obtain the EMT molecular sieve product.
[0033] The molecular sieve product obtained in this embodiment exhibits typical EMT topological diffraction characteristic peaks, such as... Figure 1 As shown, the relative crystallinity is 98%. Furthermore, SEM results of the molecular sieve product show that the EMT molecular sieve exhibits a typical hexagonal morphology. The average particle size of the EMT molecular sieve product is 2.4 μm, and the specific surface area is 855 m². 2 / g, total pore volume is 0.39cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 6.3; the Na2O mass content in the EMT molecular sieve product is 10.6%. Example 2
[0034] (1) Sodium silicate, sodium hydroxide and sodium aluminate were added to water according to the molar ratio of Na2O:Al2O3:SiO2:H2O of each component being 16:1:4:200. The mixture was stirred at 800r / min for 12h at room temperature to obtain the directing agent.
[0035] (2) According to the molecular sieve mother liquor composition, the molar ratio of Na2O:Al2O3:SiO2:H2O is 1.8:1:8:100. First, sodium hydroxide, sodium aluminate and sodium carboxymethyl cellulose (molecular weight 300-800) are added to a certain amount of water. The amount of sodium carboxymethyl cellulose added accounts for 5% of the mass of silicon source (based on SiO2 mass ratio) in the molecular sieve mother liquor. Then, 30% concentration of silica sol is added to the above solution. Finally, the directing agent obtained in step (1) is added. The amount of directing agent added is 2% of the mass of silicon source (based on SiO2 mass) in the directing agent, which accounts for 2% of the mass of silicon source (based on SiO2 mass) in the molecular sieve mother liquor. After stirring evenly, it is transferred to a polytetrafluoroethylene stainless steel reactor and statically crystallized at 100℃ for 5 days. The molecular sieve product is filtered and separated, washed with deionized water until the washing water is neutral, dried at 100℃ for 24 hours, and calcined at 500℃ for 3 hours to obtain the EMT molecular sieve product.
[0036] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 89%; the product also presents a typical EMT molecular sieve hexagonal morphology; the average particle size of the EMT molecular sieve product is 1.8 μm; and the specific surface area of the EMT molecular sieve product is 820 m². 2 / g, total pore volume is 0.37cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 5.8; the Na2O mass content in the EMT molecular sieve product is 11.4%. Example 3
[0037] (1) Sodium silicate, sodium hydroxide and sodium aluminate were added to water according to the molar ratio of Na2O:Al2O3:SiO2:H2O of each component being 19:1:6:400. The mixture was stirred at 500r / min for 36h at room temperature to obtain the directing agent.
[0038] (2) According to the molecular sieve mother liquor composition, the molar ratio of Na2O:Al2O3:SiO2:H2O is 2.5:1:12:200. First, sodium hydroxide, sodium aluminate and sodium carboxymethyl cellulose (molecular weight 300-800) are added to a certain amount of water. The amount of sodium carboxymethyl cellulose added accounts for 15% of the mass of silicon source (based on SiO2 mass ratio) in the molecular sieve mother liquor. Then, 30% concentration of silica sol is added to the above solution. Finally, the directing agent obtained in step (1) is added. The amount of directing agent added is 10% of the mass of silicon source (based on SiO2 mass) in the directing agent. After stirring evenly, it is transferred to a polytetrafluoroethylene stainless steel reactor and statically crystallized at 115℃ for 10 days. The molecular sieve product is filtered and separated, washed with deionized water until the washing water is neutral, dried at 100℃ for 24h, and calcined at 600℃ for 3h to obtain EMT molecular sieve product.
[0039] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 103%; the product also presents a typical EMT molecular sieve hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.7 μm; and the specific surface area of the EMT molecular sieve product is 873 m². 2 / g, total pore volume is 0.41cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 7.1; the Na2O mass content in the EMT molecular sieve product is 9.0%. Example 4
[0040] The molecular sieve synthesis steps are the same as in Example 1, except that in step (1), the silicon source is replaced by silica sol instead of sodium silicate, and the aluminum source is replaced by aluminum isopropoxide instead of sodium aluminate, while other conditions remain unchanged.
[0041] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 87%; the product also presents a typical EMT molecular sieve regular hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.2 μm; and the specific surface area of the EMT molecular sieve product is 781 m². 2 / g, total pore volume is 0.35cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 6.2; the Na2O mass content in the EMT molecular sieve product is 10.4%. Example 5
[0042] The molecular sieve synthesis steps are the same as in Example 1, except that in step (2), tetraethyl orthosilicate is used instead of silica sol as the silicon source, and aluminum nitrate is used instead of sodium aluminate as the aluminum source, while other conditions remain unchanged.
[0043] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 96%; the product also presents a typical EMT molecular sieve regular hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.5 μm; and the specific surface area of the EMT molecular sieve product is 840 m². 2 / g, total pore volume is 0.38cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 6.4; the Na2O mass content in the EMT molecular sieve product is 9.8%. Example 6
[0044] The molecular sieve synthesis steps are the same as in Example 1, except that in step (2), sodium carboxymethyl cellulose (molecular weight 800-1200) is used instead of sodium carboxymethyl cellulose (300-800) as the template agent.
[0045] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 94%; the product also presents a typical EMT molecular sieve hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.2 μm; and the specific surface area of the EMT molecular sieve product is 838 m². 2 / g, total pore volume is 0.40cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 6.8; the Na2O mass content in the EMT molecular sieve product is 10.1%. Example 7
[0046] The molecular sieve synthesis steps are the same as in Example 1, except that sodium carboxymethyl cellulose (300-800) is not added in step (2), and other conditions remain unchanged.
[0047] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 102%; the molecular sieve product also presents a typical EMT molecular sieve regular hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.6 μm; and the specific surface area of the EMT molecular sieve product is 860 m². 2 / g, total pore volume is 0.38cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 4.9; the Na2O mass content in the EMT molecular sieve product is 12.1%. Example 8
[0048] The molecular sieve synthesis steps are the same as in Example 2, except that sodium carboxymethyl cellulose (300-800) is not added in step (2), and other conditions remain unchanged.
[0049] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 95%; the molecular sieve product also presents a typical EMT molecular sieve regular hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.0 μm; and the specific surface area of the EMT molecular sieve product is 824 m². 2 / g, total pore volume is 0.35cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 4.5; the Na2O mass content in the EMT molecular sieve product is 12.8%. Example 9
[0050] The molecular sieve synthesis steps are the same as in Example 3, except that sodium carboxymethyl cellulose (300-800) is not added in step (2), and other conditions remain unchanged.
[0051] The molecular sieve product obtained in this embodiment also exhibits typical EMT topological diffraction characteristic peaks, with a relative crystallinity of 105%; the molecular sieve product also presents a typical EMT molecular sieve regular hexagonal morphology; the average particle size of the EMT molecular sieve product is 2.8 μm; and the specific surface area of the EMT molecular sieve product is 835 m². 2 / g, total pore volume is 0.37cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 5.3; the Na2O mass content in the EMT molecular sieve product is 11.8%.
[0052] Comparative Example 1 The molecular sieve synthesis steps are the same as in Example 1, except that step (1) is omitted, and in step (2), 18-crown ether-6 is used instead of sodium carboxymethyl cellulose (300-800) as the template agent.
[0053] The molecular sieve product obtained in this comparative example also showed typical EMT topological diffraction characteristic peaks. Figure 3 The relative crystallinity is 100%; the product also exhibits a typical hexagonal morphology of EMT molecular sieves. Figure 4 Furthermore, the edges and corners are more regular and distinct; the average particle size of EMT molecular sieve products is 3.2 μm; the specific surface area of EMT molecular sieve products is 860 m². 2 / g, total pore volume is 0.38cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 6.4; the Na2O mass content in the EMT molecular sieve product is 10.3%.
[0054] Comparative Example 2 The molecular sieve synthesis steps are the same as in Example 1, except that step (1) is omitted, that is, no directing agent is introduced into the system.
[0055] Due to the lack of induction from highly active EMT nuclei in the directing agent, the product prepared in Comparative Example 2 exhibits diffraction peaks characteristic of non-EMT topological structures. Figure 5 Furthermore, the morphology of the product particles also exhibits an irregular particle cluster morphology, which is not the typical hexagonal morphology of EMT molecular sieves. Figure 6 The average particle size of the product is 1.2 μm; the specific surface area of the product is 126 m². 2 / g, total pore volume is 0.11cm 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the product is 8.9; the Na2O mass content of the product is 2.1%.
[0056] Comparative Example 3 (1) Sodium silicate, sodium hydroxide and sodium aluminate were added to water according to the molar ratio of Na2O:Al2O3:SiO2:H2O of each component being 12:1:5:300. The mixture was stirred at 500r / min for 24h at room temperature to obtain the directing agent.
[0057] (2) The experimental steps are the same as steps (2) in Example 1.
[0058] The molecular sieve product obtained in this comparative example exhibits typical FAU-type topological diffraction peaks; furthermore, the morphology of the molecular sieve product is also a typical FAU molecular sieve octahedral morphology; the average particle size of the molecular sieve product is 1.8 μm; and the specific surface area of the molecular sieve product is 829 m². 2 / g, total pore volume is 0.35cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the molecular sieve product is 5.0; the Na2O mass content in the molecular sieve product is 12.5%.
[0059] Comparative Example 4 (3) Sodium silicate, sodium hydroxide and sodium aluminate were added to water according to the molar ratio of Na2O:Al2O3:SiO2:H2O of each component being 18:1:8:300. The mixture was stirred at 500r / min for 24h at room temperature to obtain the directing agent.
[0060] (4) The experimental steps are the same as steps (2) in Example 1.
[0061] The molecular sieve product obtained in this comparative example exhibits typical FAU-type topological diffraction peaks; furthermore, the morphology of the molecular sieve product is also a typical FAU molecular sieve octahedral morphology; the average particle size of the molecular sieve product is 1.5 μm; and the specific surface area of the molecular sieve product is 841 m². 2 / g, total pore volume is 0.37cm³ 3 / g; the silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the molecular sieve product is 5.2; the Na2O mass content in the molecular sieve product is 12.2%.
Claims
1. A method for preparing EMT molecular sieves, characterized in that: The method includes the following: (1) Directing agent preparation: The molar ratio of each component in the directing agent is Na2O:Al2O3:SiO2:H2O = (16-19):1:(4-6):(200-400), preferably Na2O:Al2O3:SiO2:H2O = 17-18:1:4-6:250-350; (2) Molecular sieve synthesis: After uniformly mixing silicon source, aluminum source, alkali source, water and the directing agent obtained in step (1), EMT molecular sieve is obtained by crystallization, filtration, washing, drying and calcination.
2. The preparation method according to claim 1, characterized in that: The silicon source mentioned in step (1) is at least one of sodium silicate, silica sol, water glass, tetraethyl orthosilicate and silica, with sodium silicate being more preferred.
3. The preparation method according to claim 1, characterized in that: The alkali source mentioned in step (1) is sodium hydroxide; the aluminum source is at least one of sodium aluminate, aluminum isopropoxide, and aluminum nitrate, preferably sodium aluminate.
4. The preparation method according to claim 1, characterized in that: The mixing temperature mentioned in step (1) is room temperature, and the mixing time is 12h-36h.
5. The preparation method according to claim 1, characterized in that: In step (2), the alkali source is first mixed with water evenly, then the silicon source is added, and finally the guiding agent obtained in step (1) is added to form a molecular sieve mother liquor. After mixing evenly, the mixture is crystallized.
6. The preparation method according to claim 1, characterized in that: The silicon source mentioned in step (2) is at least one of silica sol, water glass, tetraethyl orthosilicate and silica, with silica sol being more preferred.
7. The preparation method according to claim 1, characterized in that: The alkali source mentioned in step (2) is sodium hydroxide; the aluminum source is at least one of sodium aluminate, aluminum isopropoxide and aluminum nitrate, preferably sodium aluminate.
8. The preparation method according to claim 1, characterized in that: Step (2) The components in the molecular sieve mother liquor are in the following molar ratio: Na2O:Al2O3:SiO2:H2O = (1.8-2.5):1:(8-12):(100-200), preferably Na2O:Al2O3:SiO2:H2O = 2-2.4:1:9-10:140-160; the amount of the directing agent added is 2%-10% of the mass of silicon source in the molecular sieve mother liquor based on the mass of SiO2, preferably 4%-5%.
9. The preparation method according to claim 1, characterized in that: The molecular sieve mother liquid crystallization temperature in step (2) is 100℃-115℃, preferably 105℃-110℃, and the crystallization time is 5 days-10 days, preferably 7 days-8 days.
10. The preparation method according to claim 1, characterized in that: The molecular sieve product described in step (2) is subjected to solid-liquid separation by filtration, washed with water until neutral, and the drying temperature is 80℃-120℃, the drying time is 12h-24h; the calcination temperature is 500℃-600℃, the calcination time is 3h-6h.
11. The preparation method according to claim 1, characterized in that: In step (2), sodium carboxymethyl cellulose is added, preferably sodium carboxymethyl cellulose, and the amount added is 5%-15% of the mass of the molecular sieve mother liquor silicon source based on SiO2, preferably 8%-10%.
12. The EMT molecular sieve prepared by any one of claims 1-11, characterized in that: The molecular sieve product described above has a typical EMT topology.
13. The molecular sieve according to claim 12, characterized in that: The relative crystallinity of the EMT molecular sieve is 85%-105%, preferably 90%-100%.
14. The molecular sieve according to claim 12, characterized in that: The EMT molecular sieve product exhibits a typical regular hexagonal morphology with an average particle size of 1.5μm-3.0μm, preferably 2.0μm-2.5μm.
15. The molecular sieve according to claim 12, characterized in that: The specific surface area of the EMT molecular sieve product is 750 m². 2 / g-900m 2 / g, preferably 830m 2 / g-870m 2 / g, total pore volume is 0.35cm³ 3 / g-0.45cm 3 / g, preferably 0.38cm 3 / g-0.42cm 3 / g.
16. The molecular sieve according to claim 12, characterized in that: The silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of the EMT molecular sieve product is 4.5-7.5, preferably 6.0-7.
0.
17. The EMT molecular sieve prepared by any of the methods of claims 1-11 or the EMT molecular sieve described in any of claims 12-16 is used for isomerization reactions and alkylation reactions.