Preparation method of zeolite molecular sieve with precisely adjusted particle size
By precisely controlling the particle size of zeolite molecular sieves through a two-stage synthesis method, the problem of uneven particle size in existing technologies has been solved, thereby improving yield and catalytic performance, especially in the selectivity and lifespan of methanol-to-olefins reactions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUN YAT SEN UNIV
- Filing Date
- 2024-01-25
- Publication Date
- 2026-06-02
AI Technical Summary
Existing methods for synthesizing zeolite molecular sieves result in inconsistent particle sizes that cannot be precisely controlled, and the preparation process is complex, costly, and causes significant pollution.
A two-stage synthesis method was adopted. First, the temperature was maintained at 0-150℃ for 1-200 hours, and then the temperature was raised to 160-230℃ for 6-96 hours to crystallize, thus synthesizing zeolite molecular sieves with uniform particle size.
Precise control of zeolite molecular sieve particle size has been achieved, improving yield and catalytic performance, especially in selectivity and catalytic lifetime in methanol-to-olefins reaction.
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Figure CN118047395B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fine chemical technology, and more specifically, to a zeolite molecular sieve preparation technology. Background Technology
[0002] Zeolite molecular sieves play a vital role in the chemical industry, particularly in the production of essential chemical raw materials such as ethylene and propylene. Ethylene and propylene are key raw materials for synthesizing various polymer materials, chemical intermediates, and final chemical products, and are widely used in all sectors of national economy and people's livelihood.
[0003] Currently, the synthesis of zeolite molecular sieves often employs auxiliary methods to improve sample performance by adjusting the sample particle size, including sol-gel method, microwave-assisted synthesis method, ultrasonic-assisted method, and seed crystal method.
[0004] In China, Wu Qinming et al. (CN111252781) provided a method for synthesizing high-silicon KFI zeolite molecular sieves using a seed crystal method without organic template agents. An aluminum source is dissolved in deionized water and stirred until clear. Then, a sodium-containing alkali source, a potassium source, and a silicon source are added, stirred, and mixed. The mixture is then transferred to a reaction vessel, and KFI zeolite molecular sieve seeds are added for crystallization, which takes 4-15 days. The solid product is washed and dried to obtain the zeolite molecular sieve product. However, this synthesis method requires the addition of sodium and potassium sources, resulting in a complex raw material composition; the crystallization time is long, the crystallinity of the KFI zeolite molecular sieve is low, and the particle size of the zeolite molecular sieve cannot be precisely adjusted.
[0005] Tian Shuxun et al. (CN101555020) dissolved a template agent, silicon source, aluminum source, and phosphorus source in water and stirred to form a solution. The solution was then maintained at 100°C-150°C for 5-72 hours to obtain a seed crystal gel, which was set aside. The aluminum source, phosphorus source, and silicon source were dissolved in water to form a solution, which was then added to the prepared seed crystal gel and mixed thoroughly. A crystallization reaction was then carried out under the conditions of maintaining the temperature at 150-250°C for 10-72 hours; or the temperature was first maintained at 100-150°C for 5-72 hours, and then increased to 150-250°C for another 5-72 hours. The solid product was then washed and dried to obtain the zeolite molecular sieve product. This method significantly reduces the amount of organic template agent used in the preparation of SAPO zeolite molecular sieves, thereby reducing costs and pollution. However, this method has a complex preparation procedure and is cumbersome to operate. It requires the additional preparation of the seed crystal gel, and the particle size of the product cannot be precisely controlled. The particle size uniformity of the synthesized zeolite molecular sieves also needs improvement.
[0006] Shen Baojian et al. (CN100389067) used natural minerals such as perlite and montmorillonite as raw materials to provide all or part of the aluminum source, and added seed crystals to carry out a crystallization reaction under hydrothermal conditions to obtain ZSM-5 zeolite molecular sieves. This method expands the range of raw materials for synthesizing zeolite molecular sieves, finds new applications for more natural minerals, and further reduces the synthesis cost of zeolite molecular sieves. However, the synthesized zeolite molecular sieves have problems such as low crystallinity and uneven particle size, and their quality needs to be further improved.
[0007] Fan et al. (CN112744827) mixed an alkali source, an aluminum source, and some water, stirred until clear, and then added seed crystals and some silicon source to prepare a high-alkalinity precursor sol mixture. After aging and cooling, the remaining silicon source and water were added, and crystallization was carried out. The product was then separated into solid and liquid phases and dried to obtain magnesium-alkali zeolite molecular sieves. This method proposes aging under high alkalinity conditions followed by hydrothermal crystallization under low alkalinity conditions. The resulting product has high stability and crystallinity, low synthesis cost, and no template agent is added, resulting in less environmental pollution. However, the product synthesized by this method has low crystallinity, obvious impurities, and its uniformity needs improvement. Furthermore, it cannot precisely control the particle size of the zeolite molecular sieve. Summary of the Invention
[0008] To overcome the problems of uneven particle size and inability to precisely control the particle size of zeolite molecular sieves in the existing preparation methods, the purpose of this invention is to provide a simple preparation method for zeolite molecular sieves with good particle size uniformity and precise control over the particle size, while increasing the yield of zeolite molecular sieves.
[0009] To achieve the above objectives, the present invention adopts the following technical solution:
[0010] A method for preparing zeolite molecular sieves includes the following steps:
[0011] (1) Add the aluminum source and other raw materials to deionized water and stir evenly at room temperature;
[0012] (2) Add silicon source, stir at room temperature, add template agent to obtain precursor slurry;
[0013] (3) Add zeolite molecular sieve. The amount of zeolite molecular sieve is 1-15 mg / g of precursor slurry. Transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene, fix it on a homogeneous reactor, raise the temperature to 0-150℃, maintain it for 1-200h, and then raise the temperature to 160-230℃ for 3 hours to crystallize for 6-96h.
[0014] (4) After the reaction is completed, the zeolite molecular sieve is obtained by centrifugation, washing, drying and calcination.
[0015] Preferably, in the above preparation method, the aluminum source is boehmite, aluminum hydroxide, aluminum oxide, aluminum sulfate, or aluminum isopropoxide; the optimal aluminum source is boehmite.
[0016] Preferably, in the above preparation method, the silicon source is tetraethyl silicate, water glass, silica sol, silica gel, or silica dioxide. The optimal silicon source is tetraethyl silicate or silica sol.
[0017] Preferably, in the above preparation method, the template agent is triethylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, diethylamine, n-butylamine, morpholine, aniline, isopropylamine, or any combination thereof. The optimal template agent is tetrapropylammonium hydroxide, triethylamine, morpholine, or any combination thereof.
[0018] Preferably, in the above preparation method, the other raw material is phosphoric acid or sodium hydroxide.
[0019] Preferably, in the above preparation method, the aluminum source is alumina, the silicon source is silicon dioxide, and the other raw materials are phosphoric acid; the molar ratio of alumina, silicon dioxide, phosphoric acid, template agent and deionized water is 1 : (1-0.10): (3-1): (8-1): (50-200), and the zeolite molecular sieve prepared in this way is SAPO-34.
[0020] Preferably, in the above preparation method, the aluminum source is alumina, the silicon source is silicon dioxide, and the other raw materials are sodium hydroxide; the molar ratio of alumina, silicon dioxide, sodium oxide, template agent and deionized water is 1 : (200-10) : (20-1) : (25-5) : (500-10000), and the zeolite molecular sieve prepared in this way is ZSM-5.
[0021] Preferably, in the above preparation method, the zeolite molecular sieve in step (3) is a CHA zeolite molecular sieve or an MFI zeolite molecular sieve.
[0022] Compared with the prior art, the beneficial effects of the present invention are:
[0023] The innovation of this invention lies in its first-ever two-stage synthesis method. The core of this method is that the first stage involves heating to 0-150℃ and maintaining this temperature for 1-200 hours before proceeding to the second stage, which involves heating to 160-230℃ for 3 hours and then crystallizing for 6-96 hours. This results in highly uniform zeolite molecular sieves with controllable particle size. Through this two-stage synthesis method, the yield of zeolite molecular sieves can be increased while gradually reducing the particle size of the product. SAPO-34 zeolite molecular sieves with particle sizes of 9.9-10.3, 7.5-7.9, and 2.8-3.2 μm were successfully synthesized, with particle size deviations of less than 0.4 μm within the same batch. After reducing the particle size of the SAPO-34 zeolite molecular sieve, the catalytic performance of methanol-to-olefins (MTO) is significantly improved, with ethylene-propylene selectivity increasing by more than 5% and catalytic lifetime increasing by more than 60 minutes. ZSM-5 zeolite molecular sieves with particle sizes of 10.5-10.7, 3.9-4.1, and 2.5-2.7 μm were successfully synthesized, with particle size deviations of less than 0.2 μm for zeolite molecular sieves synthesized in the same batch. Attached Figure Description
[0024] Figure 1 This is a SEM image of the morphology of the SAPO-34 zeolite molecular sieve obtained in Example 3 of the present invention.
[0025] Figure 2 This is a SEM image of the morphology of the ZSM-5 zeolite molecular sieve obtained in Example 5 of the present invention.
[0026] Figure 3 The XRD patterns of SAPO-34 zeolite molecular sieves obtained in Examples 1-3 of this invention are shown below.
[0027] Figure 4 The XRD patterns of ZSM-5 zeolite molecular sieves obtained in Examples 4-6 of this invention are shown. Detailed Implementation
[0028] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.
[0029] The instruments used for characterization and the basic operating parameters for characterization in this embodiment are as follows:
[0030] Scanning electron microscopes: JEOL IT200, Thermofisher Apreo 2S
[0031] X-ray powder diffraction analysis: Ultima IV
[0032] Fixed-bed reaction evaluation device: VDRT-200SMT
[0033] Gas chromatography: GC-2014CAFC Example 1
[0034] (1): Add alumina and phosphoric acid to deionized water and stir evenly at room temperature. (2): Add tetraethyl silicate and continue stirring at room temperature for a period of time. Then add triethylamine to obtain SAPO-34 precursor slurry. The initial gel mixture contains Al2O3:P2O5:SiO2:TEA:H2O = 1:1:0.35:3.5:50. (4): Add 0.20g of CHA zeolite molecular sieve and transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene. Fix it on a homogeneous reactor, heat it to 120℃, maintain it at 20rpm for 80h, then heat it to 200℃ after 3h and react it at 200℃ for 48h. (5): After the reaction is completed, centrifuge, wash, dry and calcine to obtain SAPO-34 zeolite molecular sieve. Example 2
[0035] (1): Add aluminum sulfate and phosphoric acid to deionized water and stir evenly at room temperature. (2): Add water glass and continue stirring at room temperature for a period of time. Then add tetraethylammonium hydroxide to obtain SAPO-34 precursor slurry. The initial gel mixture contains Al2O3:P2O5:SiO2:TEAOH:H2O = 1:1:0.4:3.5:100. (4): Add 0.40g of CHA zeolite molecular sieve and transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene. Fix it on a homogeneous reactor, heat it to 110℃, maintain it at 20rpm for 100h, then heat it to 190℃ after 3 hours and react at 190℃ for 48 hours. (5): After the reaction is completed, centrifuge, wash, dry and calcine to obtain SAPO-34 zeolite molecular sieve. Example 3
[0036] (1): Add aluminum isopropoxide and phosphoric acid to deionized water and stir evenly at room temperature. (2): Add alkaline silica sol, continue stirring at room temperature for a period of time, and then add n-butylamine to obtain SAPO-34 precursor slurry. The initial gel mixture contains Al2O3:P2O5:SiO2:BTA:H2O = 1:1:0.5:3.5:150. (4): Add 0.60g of CHA zeolite molecular sieve, transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene, fix it on a homogeneous reactor, raise the temperature to 100℃, maintain it at 20rpm for 120h, raise the temperature to 180℃ after 3h, and react at 180℃ for 48h. (5): After the reaction is completed, centrifuge, wash, dry and calcine to obtain SAPO-34 zeolite molecular sieve. See electron micrograph for details. Figure 1 .
[0037] Comparative Example 1:
[0038] (1): Add aluminum isopropoxide and phosphoric acid to deionized water and stir evenly at room temperature. (2): Add alkaline silica sol, continue stirring at room temperature for a period of time, and then add n-butylamine to obtain SAPO-34 precursor slurry. The initial gel mixture contains Al2O3:P2O5:SiO2:BTA:H2O = 1:1:0.5:3.5:150. (4): Transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene, fix it on a homogeneous reactor, and react at 180℃ for 48 hours. (5): After the reaction is completed, centrifuge, wash, dry, and calcine to obtain SAPO-34 zeolite molecular sieve.
[0039]
[0040] MTO reaction conditions: reaction temperature 450℃, WHSV = 2h -1 Catalyst mass: 0.5g
[0041] Note: The relative crystallinity of SAPO-34 molecular sieve mentioned refers to the ratio of the sum of the peak areas at 2θ = 9.3°, 20.4°, and 30.3° in its XRD pattern, expressed as a percentage.
[0042] As can be seen from Table 1, Examples 1-3 of the present invention have significantly improved particle size uniformity compared with Comparative Document 1, and also have significantly improved yield and MTO selectivity.
[0043] Example 4:
[0044] (1): Add boehmite and sodium hydroxide to deionized water and stir evenly at room temperature. (2): Add alkaline silica sol and continue stirring at room temperature for a period of time. Then add tetrapropylammonium hydroxide to obtain ZSM-5 precursor slurry. The initial gel mixture contains Al2O3: Na2O SiO2: TPAOH: H2O = 1: 13: 75: 18: 4000. (3): Add 0.20g of MFI zeolite molecular sieve, transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene, fix it on a homogeneous reactor, raise the temperature to 120℃, maintain it at 20rpm for 160h, then raise the temperature to 200℃ after 3 hours, and react at 200℃ for 48 hours. After the reaction is completed, centrifuge, wash, dry and calcine to obtain ZSM-5 zeolite molecular sieve.
[0045] Example 5:
[0046] (1): Add aluminum hydroxide and sodium hydroxide to deionized water and stir evenly at room temperature. (2): Add alkaline silica sol and continue stirring at room temperature for a period of time. Then add triethylamine to obtain ZSM-5 precursor slurry. The initial gel mixture contains Al2O3: Na2O: SiO2: TEA: H2O = 1: 13: 90: 18: 6000. (3): Add 0.40g of MFI zeolite molecular sieve and transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene. Fix it on a homogeneous reactor, heat it to 110℃, maintain it at 20rpm for 180h, then heat it to 190℃ after 3 hours and react at 190℃ for 48 hours. After the reaction is completed, centrifuge, wash, dry and calcine to obtain ZSM-5 zeolite molecular sieve. See electron micrograph for details. Figure 2 .
[0047] Example 6:
[0048] (1): Boehmite and sodium hydroxide were added to deionized water and stirred evenly at room temperature. (2): Alkaline silica sol was added, and after stirring for a period of time at room temperature, tetrapropylammonium hydroxide was added to obtain ZSM-5 precursor slurry. The initial gel mixture contained Al2O3: Na2O: SiO2: TPAOH: H2O = 1: 13: 105: 18: 8000. (3): 0.60 g of MFI zeolite molecular sieve was added, and the precursor slurry was transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was fixed on a homogeneous reactor, heated to 100℃, and maintained at 20 rpm for 200 h. After 3 hours, the temperature was raised to 180℃, and the reaction was carried out at 180℃ for 48 hours. After the reaction was completed, the mixture was centrifuged, washed, dried, and calcined to obtain ZSM-5 zeolite molecular sieve.
[0049] Comparative Example 2:
[0050] (1): Boehmite and sodium hydroxide were added to deionized water and stirred evenly at room temperature. (2): Alkaline silica sol was added, and after stirring for a period of time at room temperature, tetrapropylammonium hydroxide was added to obtain ZSM-5 precursor slurry. The initial gel mixture contained Al2O3: Na2O: SiO2: TPAOH: H2O = 1:13:105:18:8000. (3): The precursor slurry was transferred to a high-pressure reactor lined with polytetrafluoroethylene and fixed on a homogeneous reactor. The reaction was carried out at 180℃ for 48 hours. After the reaction was completed, the mixture was centrifuged, washed, dried, and calcined to obtain ZSM-5 zeolite molecular sieve.
[0051]
[0052] Note: The relative crystallinity of ZSM-5 molecular sieve mentioned refers to the ratio of the sum of the peak areas at 2θ = 7.9°, 8.9°, and 23.3° in its XRD pattern, expressed as a percentage.
[0053] As can be seen from Table 2, Examples 4-6 of the present invention have significantly improved particle size uniformity compared with Comparative Document 2, and the yield is also significantly increased.
Claims
1. A method for preparing zeolite molecular sieves, characterized in that... It consists of the following steps: (1) Add the aluminum source and other raw materials to deionized water and stir evenly at room temperature; (2) Add silicon source, stir at room temperature, add template agent to obtain precursor slurry; (3) Add CHA zeolite molecular sieve or MFI zeolite molecular sieve. The amount of zeolite molecular sieve is 1-15 mg / g of precursor slurry. Transfer the precursor slurry to a high-pressure reactor lined with polytetrafluoroethylene, fix it on a homogeneous reactor, raise the temperature to 100-120℃, maintain it for 80-200h, and then raise the temperature to 160-230℃ for 3 hours to crystallize for 6-96h. (4) After the reaction is completed, the zeolite molecular sieve is obtained by centrifugation, washing, drying and calcination. When CHA zeolite molecular sieve is added in step (3), the zeolite molecular sieve prepared is SAPO-34. When MFI zeolite molecular sieve is added in step (3), the zeolite molecular sieve prepared is ZSM-5. The other raw materials are phosphoric acid or sodium hydroxide.
2. The preparation method according to claim 1, characterized in that, The aluminum source is boehmite, aluminum hydroxide, aluminum oxide, aluminum sulfate, or aluminum isopropoxide.
3. The preparation method according to claim 2, characterized in that, The aluminum source is boehmite.
4. The preparation method according to claim 1, characterized in that, The silicon source is tetraethyl silicate, water glass, silica sol, silica gel, or silicon dioxide.
5. The preparation method according to claim 4, characterized in that, The silicon source is tetraethyl silicate or silica sol.
6. The preparation method according to claim 1, characterized in that, The template agent is triethylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, diethylamine, n-butylamine, morpholine, aniline, isopropylamine, or any combination thereof.
7. The preparation method according to claim 6, characterized in that, The template agent is tetrapropylammonium hydroxide, triethylamine, morpholine, or any combination thereof.
8. The preparation method according to claim 1, characterized in that, The aluminum source is alumina, the silicon source is silicon dioxide, and the other raw material is phosphoric acid; the molar ratio of alumina, silicon dioxide, phosphoric acid, template agent and deionized water is 1 : (1-0.10) : (3-1) : (8-1) : (50-200), and the zeolite molecular sieve prepared at this time is SAPO-34.
9. The preparation method according to claim 1, characterized in that, The aluminum source is alumina, the silicon source is silicon dioxide, and the other raw materials are sodium hydroxide; the molar ratio of alumina, silicon dioxide, sodium hydroxide, template agent and deionized water is 1 : (200-10) : (20-1) : (25-5) : (500-10000), and the zeolite molecular sieve prepared under these conditions is ZSM-5.