Method for preparing high-crystallinity nanometer S-1 molecular sieve through low template agent system and application of high-crystallinity nanometer S-1 molecular sieve
Through the addition of low-template agent system and fluoride and S-1 seeds, the S-1 molecular sieve synthesis process is optimized, and the environmental pollution and crystal size problems caused by high-template agent are solved, and the efficient adsorption effect of volatile organic matter is achieved.
Patent Information
- Application Number
- CN202510409721.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-07-08
AI Technical Summary
In the traditional S-1 molecular sieve synthesis process, high template agent usage leads to high production costs, serious environmental pollution, and poor crystallinity and nanometer size, which affects its efficiency as VOCs adsorption material.
High crystallinity nano S-1 molecular sieve was synthesized using a low-template agent system. By adding fluoride and S-1 seeds of different sizes, the synthesis conditions were optimized to improve adsorption performance.
The S-1 molecular sieve synthesized under low template agent conditions showed significantly improved volatile organic adsorption ability under humidity conditions, even surpassing the S-1 molecular sieve synthesized by traditional high template agents, showing excellent toluene adsorption properties.
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Figure CN120271007A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of molecular sieve preparation, and particularly relates to a method for preparing high-crystallinity nano S-1 molecular sieve with a low template agent system and its application. Background Art
[0002] Volatile Organic Compounds (VOCs), such as toluene, pose a significant threat to human health and the ecological environment due to their strong toxicity and volatility. Given the serious hazards of VOCs, their treatment technologies have become a research hotspot in the current environmental protection field. Among many treatment technologies, the adsorption method has been widely used in the field of VOCs treatment due to its advantages such as simple operation, good selectivity, and recyclability of the adsorbent. The performance of the adsorbent plays a crucial role in the removal efficiency of VOCs. Therefore, developing efficient and economical adsorbent materials is the key to improving the treatment effect of VOCs.
[0003] Silicalite-1 (S-1) molecular sieve, with its regular pore structure, high specific surface area, and excellent hydrothermal stability, shows great potential as an efficient adsorbent material for VOCs such as toluene. However, the traditional S-1 molecular sieve synthesis process requires a large amount of tetrapropylammonium hydroxide (TPAOH) as a template agent, which not only significantly increases the production cost but also causes non-negligible pollution to the environment. Synthesizing S-1 molecular sieve with a low TPAOH template agent dosage is likely to result in problems such as reduced crystallinity of the product, low yield, incomplete crystallization, and increased crystal size. Due to the increase in crystal size, the mass transfer efficiency of these S-1 molecular sieves during the adsorption process will also be affected, further limiting their application potential as VOCs adsorbent materials.
[0004] Therefore, in the synthesis process of S-1 molecular sieve, how to effectively reduce the dosage of TPAOH template agent while ensuring high crystallinity and nano size has become a technical problem to be solved urgently. Summary of the Invention
[0005] To solve the above technical problems, the present invention provides a method for preparing high-crystallinity nano S-1 molecular sieve with a low template agent system and its application, which synthesizes high-crystallinity S-1 molecular sieve under the condition of using a low dosage of TPAOH and / or tetrapropylammonium salt template agent, and further prepares regular nano-sized S-1 molecular sieve with high crystallinity by adding S-1 seeds of different sizes. The prepared nano S-1 molecular sieve has excellent volatile organic compound adsorption ability.
[0006] The present invention is achieved through the following technical solutions:
[0007] In the first aspect of the present invention, a method for preparing highly crystalline nano S-1 zeolite with a low template agent system is provided, comprising the following steps:
[0008] Dissolve a silicon source and a template agent in water, carry out a crystallization reaction at 80 - 200 °C, and calcine the solid product after crystallization to obtain S-1 zeolite;
[0009] The template agent is selected from one or more of tetrapropylammonium hydroxide (TPAOH) and tetrapropylammonium salts; the molar ratio of the silicon source to the template agent is 1:(0.01 - 0.05).
[0010] Furthermore, the silicon source is selected from one or more of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate, fumed silica, silica sol, and sodium silicate.
[0011] Furthermore, the molar ratio of the silicon source to water is 1:(5 - 50), preferably 1:(5 - 15).
[0012] Furthermore, the tetrapropylammonium salts include tetrapropylammonium bromide (TPABr) and tetrapropylammonium chloride (TPACl).
[0013] Furthermore, the crystallization reaction time is 12 - 96 h, and the crystallization reaction can be carried out in a distributed crystallization or direct crystallization manner.
[0014] Furthermore, the conditions for the calcination treatment are: heating to 500 - 600 °C at a heating rate of 1 - 10 °C / min, and calcining at 500 - 600 °C for 5 - 7 h.
[0015] Furthermore, it also includes the step of adding a fluoride to water.
[0016] Furthermore, the molar ratio of the silicon source to the fluoride is 1:(0.01 - 0.5).
[0017] Furthermore, the fluoride is selected from one or more of ammonium fluoride (NH4F), hydrofluoric acid (HF), potassium fluoride, sodium fluoride, magnesium fluoride, and aluminum fluoride, preferably NH4F.
[0018] Adding a fluoride to the template agent system can increase the surface hydrophobicity of the synthesized S-1 zeolite, making it show a significantly improved volatile organic compound adsorption capacity compared with the S-1 zeolite prepared under the condition of using a high template agent under humidity conditions (RH = 60% - 100%).
[0019] Furthermore, when the template agent contains tetrapropylammonium salt, it further includes the step of adding alkali metal hydroxide to water.
[0020] Furthermore, the alkali metal hydroxide is selected from one or more of hydroxides of lithium, sodium, potassium and cesium.
[0021] Furthermore, the molar ratio of the tetrapropylammonium salt to the alkali metal hydroxide is 1:(0.5 - 1.5).
[0022] Furthermore, it further includes the step of adding S-1 seed crystals to water.
[0023] In the synthesis of a low-template agent system, adding S-1 seed crystals can further synthesize high-crystallinity S-1 zeolite with significantly reduced size; and the smaller the size of the added S-1 seed crystals, the smaller the crystal size of the synthesized S-1 zeolite, and ultimately high-crystallinity nano-sized S-1 zeolite can be synthesized.
[0024] Furthermore, the size of the S-1 seed crystals is 40 - 30000 nm.
[0025] Furthermore, the mass ratio of the S-1 seed crystals to the silicon source is (0.01 - 0.5):1.
[0026] Furthermore, the preparation method of the S-1 seed crystals includes the following steps: dissolving the silicon source and the template agent in water, carrying out a crystallization reaction at 80 - 200 °C, and calcining the solid product after crystallization to obtain S-1 seed crystals.
[0027] Furthermore, in the preparation method of the S-1 seed crystals, the molar ratio of the silicon source to the template agent is 1:(0.01 - 0.5).
[0028] Furthermore, in the preparation method of the S-1 seed crystals, the silicon source is selected from one or more of tetraethyl orthosilicate, tetramethyl orthosilicate, fumed silica, silica sol and sodium silicate.
[0029] Furthermore, in the preparation method of the S-1 seed crystals, the molar ratio of the silicon source to water is 1:(5 - 50), preferably 1:(5 - 15).
[0030] Furthermore, in the preparation method of the S-1 seed crystals, the template agent is selected from one or more of TPAOH and tetrapropylammonium salts; the tetrapropylammonium salts include TPABr and TPACl; when the template agent contains tetrapropylammonium salt, it further includes the step of adding alkali metal hydroxide to water.
[0031] Furthermore, in the preparation method of the S-1 seed crystals, it further includes the step of adding a mineralizing agent to water.
[0032] Further, the mineralizer is selected from one or more of L-lysine, glycine, L-glutamic acid, DL-methionine, and L-alanine.
[0033] Further, in the preparation method of the S-1 seed, the crystallization reaction time is 12 - 96 h, and the crystallization reaction can be carried out in a distributed crystallization or direct crystallization manner.
[0034] Further, in the preparation method of the S-1 seed, the conditions of the calcination treatment are as follows: heating to 500 - 600 °C at a heating rate of 1 - 10 °C / min, and calcining at 500 - 600 °C for 5 - 7 h.
[0035] The second aspect of the present invention provides the S-1 molecular sieve prepared by the method described in the first aspect.
[0036] The third aspect of the present invention provides the application of the S-1 molecular sieve described in the second aspect in adsorbing volatile organic compounds.
[0037] The S-1 molecular sieve provided by the present invention exhibits excellent adsorption performance in the adsorption of VOCs represented by toluene.
[0038] The beneficial effects of the present invention are as follows:
[0039] 1. The present invention synthesizes a highly crystalline S-1 molecular sieve under the condition of using a low amount of TPAOH and / or tetrapropylammonium salt template agent, and adding fluoride in the low template agent system can increase the surface hydrophobicity of the synthesized S-1 molecular sieve, so that it shows a significantly improved volatile organic compound adsorption capacity under humidity conditions (RH = 60% - 100%) compared with the S-1 molecular sieve prepared under the condition of using a high template agent conventionally.
[0040] 2. The present invention further prepares a highly crystalline regular nano-sized S-1 molecular sieve with a significantly reduced size by adding S-1 seeds of different sizes. The prepared nano S-1 molecular sieve has excellent volatile organic compound adsorption capacity, even exceeding the adsorption capacity of the S-1 molecular sieve synthesized using a high TPAOH template agent conventionally, showing great application potential. Description of the Drawings
[0041] Figure 1 It is the PXRD pattern of the highly crystalline S-1 molecular sieve prepared in Examples 1 - 3.
[0042] Figure 2 It is the SEM image of the highly crystalline S-1 molecular sieve (S-1-0.05T) prepared in Example 1; among them, a is the SEM image with a scale of 100 μm, and b is the SEM image with a scale of 50 μm.
[0043] Figure 3PXRD pattern (left) and SEM image (right) of the highly crystalline hydrophobic S-1 zeolite prepared in Example 4.
[0044] Figure 4 PXRD patterns of the highly crystalline S-1 zeolites prepared in Examples 5 - 8.
[0045] Figure 5 PXRD patterns of the highly crystalline nano S-1 zeolites prepared in Examples 9 - 11.
[0046] Figure 6 SEM images of the highly crystalline nano S-1 zeolites prepared in Examples 9 - 11; where a is 40 nm S-1 seed, b is S-1-0.05T-40 nm S, c is 200 nm S-1 seed, d is S-1-0.05T-200 nm S, e is 15 μm S-1 seed, and f is S-1-0.05T-15 μm S.
[0047] Figure 7 Graph showing the toluene adsorption performance test results of the highly crystalline S-1 zeolites prepared in Examples 1 - 3 and Comparative Example 1 and the highly crystalline nano S-1 zeolite prepared in Example 11 under dry conditions.
[0048] Figure 8 Graph showing the toluene adsorption performance test results of the highly crystalline S-1 zeolite prepared in Example 1 and the highly crystalline hydrophobic S-1 zeolite prepared in Example 4 under dry conditions and humid conditions (RH = 60%). Detailed Embodiments
[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs. The terms used in the description of this invention herein are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.
[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments given are not intended to limit the present invention.
[0051] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial sources.
[0052] Example 1
[0053] A method for preparing highly crystalline S-1 zeolite (S-1-0.05T) with a low template agent system, comprising the following steps:
[0054] First, add 0.813 g of TPAOH and 2.990 g of H2O into a 25 mL beaker, stir for 30 min, then add 1.2 g of silica white, and continue to stir for 6 h until completely dissolved (the molar ratio of SiO2:TPAOH:H2O is 1:0.05:10). Subsequently, transfer the above mixed solution into a 25 mL stainless steel hydrothermal reaction kettle, and carry out static crystallization at 170 °C for 3 d. Put the solid product obtained after crystallization into a muffle furnace, heat it from room temperature to 550 °C at a rate of 1.5 °C / min, and calcine it at 550 °C for 6 h to remove the molecular sieve template agent. Name the obtained S-1 zeolite as S-1-0.05T, where T represents the TPAOH template agent, and 0.05 represents the molar ratio of TPAOH to SiO2.
[0055] Example 2
[0056] A method for preparing highly crystalline S-1 zeolite (S-1-0.03T) with a low template agent system, comprising the following steps:
[0057] First, add 0.488 g of TPAOH and 3.230 g of H2O into a 25 mL beaker, stir for 30 min, then add 1.2 g of silica white, and continue to stir for 6 h until completely dissolved (the molar ratio of SiO2:TPAOH:H2O is 1:0.03:10). Subsequently, transfer the above mixed solution into a 25 mL stainless steel hydrothermal reaction kettle, and carry out static crystallization at 170 °C for 3 d. Put the solid product obtained after crystallization into a muffle furnace, heat it from room temperature to 550 °C at a rate of 1.5 °C / min, and calcine it at 550 °C for 6 h to remove the molecular sieve template agent. Name the obtained S-1 zeolite as S-1-0.03T, where T represents the TPAOH template agent, and 0.03 represents the molar ratio of TPAOH to SiO2.
[0058] Example 3
[0059] A method for preparing highly crystalline S-1 zeolite (S-1-0.01T) with a low template agent system, comprising the following steps:
[0060] First, 0.163 g of TPAOH and 3.480 g of H2O were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of silica was added, and stirring was continued for 6 h to completely dissolve it (the molar ratio of SiO2:TPAOH:H2O was 1:0.01:10). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained S-1 molecular sieve was named S-1-0.01T. Here, T represents the TPAOH template agent, and 0.01 represents the molar ratio of TPAOH to SiO2.
[0061] Figure 1 Powder X-ray diffraction (PXRD) patterns of the highly crystalline S-1 molecular sieves prepared in Examples 1-3 are shown. It can be seen from Figure 1 that under the condition of low TPAOH template agent dosage (the molar ratio of TPAOH to SiO2 is 0.01 - 0.05), highly crystalline S-1 molecular sieves can be synthesized.
[0062] Figure 2 Scanning electron microscope (SEM) image of the highly crystalline S-1 molecular sieve (S-1-0.05T) prepared in Example 1 is shown. It can be seen from Figure 2 that the S-1 molecular sieve synthesized under the 0.05T template agent dosage system has relatively large crystal sizes, with an average size reaching 15 μm.
[0063] Example 4
[0064] A method for preparing a highly crystalline hydrophobic S-1 molecular sieve (S-1-0.05T-0.05NH4F) with a low template agent system, comprising the following steps:
[0065] First, 0.813 g of TPAOH, 1.2 g of silica, and 2.990 g of H2O were added to a 25 mL beaker. After stirring for 30 min, 0.037 g of NH4F was added, and stirring was continued for 6 h to completely dissolve it (the molar ratio of SiO2:TPAOH:NH4F:H2O was 1:0.05:0.05:10). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained S-1 molecular sieve was named S-1-0.05T-0.05NH4F, where T represents the TPAOH template agent.
[0066] Figure 3 PXRD pattern (left figure) and SEM image (right figure) of the highly crystalline hydrophobic S-1 molecular sieve prepared in Example 4. It can be seen from Figure 3 that adding NH4F to the 0.05T template agent system can synthesize highly crystalline S-1 molecular sieve, and NH4F can regulate the morphology of S-1 molecular sieve, reducing the thickness in the b-axis direction and increasing its surface hydrophobicity at the same time.
[0067] Example 5
[0068] A method for preparing highly crystalline S-1 molecular sieve (S-1-0.05TPABr-Na) with a low template agent system, comprising the following steps:
[0069] First, add 0.266 g of TPABr, 3.60 g of H2O, and 0.0421 g of NaOH into a 25 mL beaker. After stirring for 30 min, add 1.2 g of silica white and continue to stir for 6 h until it is completely dissolved (the molar ratio of SiO2:TPABr:NaOH:H2O is 1:0.05:0.05:10). Subsequently, transfer the above mixed solution to a 25 mL stainless steel hydrothermal reaction kettle and carry out static crystallization at 170 °C for 3 d. Put the solid product obtained after crystallization into a muffle furnace, heat it from room temperature to 550 °C at a rate of 1.5 °C / min, and calcine it at 550 °C for 6 h to remove the molecular sieve template agent. Name the obtained S-1 molecular sieve as S-1-0.05TPABr-Na, where 0.05 represents the molar ratio of TPABr to SiO2 being 0.05, and Na represents the alkali metal hydroxide NaOH.
[0070] Example 6
[0071] A method for preparing highly crystalline S-1 molecular sieve (S-1-0.05TPABr-Li) with a low template agent system, comprising the following steps:
[0072] First, 0.266 g of TPABr, 3.60 g of H2O, and 0.0428 g of LiOH were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of fumed silica was added, and stirring was continued for 6 h until it was completely dissolved (the molar ratio of SiO2:TPABr:LiOH:H2O was 1:0.05:0.05:10). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reaction kettle and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained S-1 molecular sieve was named S-1-0.05TPABr-Li, where 0.05 represents the molar ratio of TPABr to SiO2 being 0.05, and Li represents the alkali metal hydroxide LiOH.
[0073] Example 7
[0074] A method for preparing a high-crystallinity S-1 molecular sieve (S-1-0.05TPABr-K) with a low template agent system, comprising the following steps:
[0075] First, 0.266 g of TPABr, 3.60 g of H2O, and 0.0561 g of KOH were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of fumed silica was added, and stirring was continued for 6 h until it was completely dissolved (the molar ratio of SiO2:TPABr:KOH:H2O was 1:0.05:0.05:10). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reaction kettle and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained S-1 molecular sieve was named S-1-0.05TPABr-K, where 0.05 represents the molar ratio of TPABr to SiO2 being 0.05, and K represents the alkali metal hydroxide KOH.
[0076] Example 8
[0077] A method for preparing a high-crystallinity S-1 molecular sieve (S-1-0.05TPABr-Cs) with a low template agent system, comprising the following steps:
[0078] First, 0.266 g of TPABr, 3.60 g of H2O, and 0.150 g of CsOH were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of fumed silica was added, and stirring was continued for 6 h to completely dissolve it (the molar ratio of SiO2:TPABr:CsOH:H2O was 1:0.05:0.05:10). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, and the temperature was raised from room temperature to 550 °C at a rate of 1.5 °C / min and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained S-1 molecular sieve was named S-1-0.05TPABr-Cs, where 0.05 represents the molar ratio of TPABr to SiO2 being 0.05, and Cs represents the alkali metal hydroxide CsOH.
[0079] Compared with the TPAOH template agent, the TPABr or TPACl template agent has greater application prospects because its solid form is easier to store and transport. Figure 4 PXRD patterns of the highly crystalline S-1 molecular sieves prepared in Examples 5-8, from Figure 4 which it can be seen that highly crystalline S-1 molecular sieves can be synthesized under the condition of low TPABr template agent dosage (the molar ratio of TPABr to SiO2 is 0.01 - 0.05).
[0080] Example 9
[0081] A method for preparing highly crystalline nano S-1 molecular sieve (S-1-0.05T-15μm S) assisted by 15μm S-1 seeds in a low template agent system, comprising the following steps:
[0082] (1) First, 0.813 g of TPAOH and 2.990 g of H2O were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of fumed silica was added, and stirring was continued for 6 h to completely dissolve it (the molar ratio of SiO2:TPAOH:H2O was 1:0.05:10). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, and the temperature was raised from room temperature to 550 °C at a rate of 1.5 °C / min and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained sample was named 15μm S-1 seeds.
[0083] (2) Synthesis of highly crystalline nano S-1 zeolite with reduced size by 15-μm S-1 seed-assisted low-template agent system. First, 0.813 g of TPAOH and 2.990 g of H2O were added to a 25-mL beaker. After stirring for 30 min, 1.2 g of silica white and 0.060 g of 15-μm S-1 seeds (molar ratio of SiO2:TPAOH:15-μm S-1 seeds:H2O = 1:0.05:0.05:10) were added. After continuing to stir for 6 h, the above mixed solution was transferred to a 25-mL stainless-steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace and heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained nano S-1 zeolite was named S-1-0.05T-15-μm S, where T represents the TPAOH template agent, 0.05 represents the molar ratio of TPAOH to SiO2 of 0.05, and 15-μm S represents the addition of 15-μm S-1 seeds.
[0084] Example 10
[0085] A method for preparing highly crystalline nano S-1 zeolite (S-1-0.05T-200-nm S) by 200-nm S-1 seed-assisted low-template agent system, comprising the following steps:
[0086] (1) First, 13.0 g of TPAOH and 15.0 g of H2O were added to a 50-mL beaker. After stirring for 10 min, 8.32 g of TEOS was added, and stirring was continued for 6 h to completely dissolve it (molar ratio of SiO2:TPAOH:H2O = 1:0.4:35). Subsequently, the above mixed solution was transferred to a 100-mL stainless-steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace and heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained sample was named 200-nm S-1 seeds.
[0087] (2) Synthesis of highly crystalline nano S-1 zeolite with reduced size by 200 nm S-1 seed-assisted low-template agent system. First, 0.813 g of TPAOH and 2.990 g of H2O were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of silica white and 0.060 g of 200 nm S-1 seeds (molar ratio of SiO2:TPAOH:200 nm S-1 seeds:H2O = 1:0.05:0.05:10) were added. After continuing to stir for 6 h, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reactor and crystallized statically at 170 °C for 3 days. The solid product obtained after crystallization was placed in a muffle furnace and heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the zeolite template agent. The obtained nano S-1 zeolite was named S-1-0.05T-200 nm S, where T represents the TPAOH template agent, 0.05 represents the molar ratio of TPAOH to SiO2 of 0.05, and 200 nm S represents the addition of S-1 seeds with a size of 200 nm.
[0088] Example 11
[0089] A method for preparing highly crystalline nano S-1 zeolite (S-1-0.05T-40 nm S) by 40 nm S-1 seed-assisted low-template agent system, comprising the following steps:
[0090] (1) First, 7.32 g of TPAOH and 4.16 g of TEOS were added to a 25 mL beaker. After stirring for 6 h, 0.146 g of L-lysine was added; after continuing to stir for 20 min, 2.25 g of H2O was evaporated by heating (molar ratio of SiO2:TPAOH:H2O:L-lysine = 1:0.45:9:0.05). Subsequently, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reactor and crystallized stepwise at 70 °C for 2 days and then at 170 °C for 1 day. The solid product obtained after crystallization was placed in a muffle furnace and heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the zeolite template agent. The obtained sample was named 40 nm S-1 seeds.
[0091] (2) Synthesis of highly crystalline nano S-1 zeolite using 40 nm S-1 seed-assisted low-template agent system. First, 0.813 g of TPAOH and 2.990 g of H2O were added to a 25 mL beaker. After stirring for 30 min, 1.2 g of silica white and 0.060 g of 40 nm S-1 seeds (molar ratio of SiO2:TPAOH:40 nm S-1 seeds:H2O = 1:0.05:0.05:10) were added. After continuous stirring for 6 h, the above mixed solution was transferred to a 25 mL stainless steel hydrothermal reaction kettle and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace and heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained nano S-1 zeolite was named S-1-0.05T-40 nm S, where T represents the TPAOH template agent, 0.05 represents the molar ratio of TPAOH to SiO2 of 0.05, and 40 nm S represents the addition of S-1 seeds with a size of 40 nm.
[0092] Figure 5 PXRD patterns of the highly crystalline nano S-1 zeolites prepared in Examples 9-11. It can be seen from Figure 5 that the use of S-1 seeds with different sizes to assist the low-template agent system can synthesize highly crystalline nano S-1 zeolites.
[0093] Figure 6 SEM images of the highly crystalline nano S-1 zeolites prepared in Examples 9-11; where a is 40 nm S-1 seeds, b is S-1-0.05T-40 nm S, c is 200 nm S-1 seeds, d is S-1-0.05T-200 nm S, e is 15 μm S-1 seeds, and f is S-1-0.05T-15 μm S. It can be seen from Figure 6 that the introduction of seeds can effectively reduce the crystal size of the synthesized S-1 zeolite, and the smaller the initial seed size added, the more obvious the effect of reducing the S-1 crystal size. Finally, when adding 40 nm S-1 seeds, highly crystalline regular nano-sized S-1 zeolites can be synthesized. Among them, the average crystal sizes of the synthesized S-1-0.05T-40 nm S, S-1-0.05T-200 nm S, and S-1-0.05T-15 μm S zeolites are 200 nm, 400 nm, and 5000 nm, respectively.
[0094] Comparative Example 1
[0095] A method for preparing S-1 zeolite (S-1-0.35T) includes the following steps:
[0096] First, 11.37 g of TPAOH and 8.32 g of TEOS were added to a 50 mL beaker. After stirring for 30 min, 1.34 g of H2O was evaporated by heating, and stirring was continued for 6 h to completely dissolve it (the molar ratio of SiO2:TPAOH:H2O was 1:0.35:10). Subsequently, the above mixed solution was transferred to a 100 mL stainless steel hydrothermal reactor and crystallized statically at 170 °C for 3 d. The solid product obtained after crystallization was placed in a muffle furnace, heated from room temperature to 550 °C at a rate of 1.5 °C / min, and calcined at 550 °C for 6 h to remove the molecular sieve template agent. The obtained S-1 molecular sieve was named S-1-0.35T.
[0097] Test Example
[0098] The toluene adsorption performance of the highly crystalline S-1 molecular sieves prepared in Examples 1-3 and Comparative Example 1 and the highly crystalline nano-S-1 molecular sieve prepared in Example 11 was tested. The test method was as follows:
[0099] First, 0.2 g of a 40-60 mesh S-1 molecular sieve sample was loaded into a quartz tube and activated in an air atmosphere at 200 °C (30 mL / min) for 30 min and then cooled to 30 °C. Subsequently, the toluene breakthrough curve was tested under atmospheric pressure conditions, and toluene vapor (1000 ppm) was introduced into the reaction tube by bubbling; the tail gas was analyzed on an on-line gas chromatograph equipped with a hydrogen flame ionization detector. The test under humid conditions was carried out by introducing water vapor with an injection pump, and the inlet relative humidity (RH) was controlled to be constant at 60% using a thermo-hygrometer.
[0100] The test results are as Figure 7 and Figure 8 shown. Figure 7 is the toluene adsorption performance test result diagram of the highly crystalline S-1 molecular sieves prepared in Examples 1-3 and Comparative Example 1 and the highly crystalline nano-S-1 molecular sieve prepared in Example 11 under dry conditions. It can be seen from Figure 7 that since the S-1 molecular sieve synthesized in Example 11 has a nano-size, it shows excellent adsorption performance in the adsorption of VOCs represented by toluene, and even can reach or exceed the toluene adsorption performance of the S-1 molecular sieve synthesized by the traditional high-template agent in Comparative Example 1; Figure 8 is the toluene adsorption performance test result diagram of the highly crystalline S-1 molecular sieve prepared in Example 1 and the highly crystalline hydrophobic S-1 molecular sieve prepared in Example 4 under dry conditions and humid conditions (RH = 60%). It can be seen from Figure 8 that adding NH4F can increase the surface hydrophobicity of the S-1 molecular sieve, and its toluene adsorption performance under humid conditions is significantly improved compared with that without adding NH4F.
[0101] In summary, the present invention provides a method for preparing highly crystalline S-1 zeolite with a low template agent system. Under the condition of using a low amount of TPAOH and / or tetrapropylammonium salt template agent, highly crystalline S-1 zeolite is synthesized. Moreover, adding fluoride in the low template agent system can increase the surface hydrophobicity of the synthesized S-1 zeolite, enabling it to exhibit significantly improved volatile organic compound adsorption capacity compared to the S-1 zeolite prepared under the condition of using a high template agent under humidity conditions (RH = 60% - 100%).
[0102] On this basis, the present invention further provides a method for preparing highly crystalline nano S-1 zeolite with a low template agent system. By further adding S-1 seeds of different sizes, highly crystalline regular nano-sized S-1 zeolite with significantly reduced size is prepared. The prepared nano S-1 zeolite has excellent volatile organic compound adsorption capacity, even exceeding the adsorption capacity of the S-1 zeolite synthesized using a high amount of TPAOH template agent conventionally, showing great application potential.
[0103] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.
Claims
1. A method for preparing highly crystalline nano S-1 zeolite with a low template agent system, characterized in that, It includes the following steps: Dissolve a silicon source and a template agent in water, conduct a crystallization reaction at 80 - 200 °C, and calcine the crystallized solid product to obtain S-1 molecular sieve; The template agent is selected from one or more of tetrapropylammonium hydroxide and tetrapropylammonium salts; the molar ratio of the silicon source to the template agent is 1:(0.01 - 0.05).
2. The method according to claim 1, wherein The silicon source is selected from one or more of tetraethyl orthosilicate, tetramethyl orthosilicate, precipitated silica, silica sol, and sodium silicate; the tetrapropylammonium salts include tetrapropylammonium bromide and tetrapropylammonium chloride.
3. The method according to claim 1, characterized in that, It also includes the step of adding a fluoride to water.
4. The method according to claim 3, characterized in that, The molar ratio of the silicon source to the fluoride is 1:(0.01 - 0.5).
5. The method according to claim 1, characterized in that When the template agent contains tetrapropylammonium salts, it also includes the step of adding an alkali metal hydroxide to water; the molar ratio of the tetrapropylammonium salt to the alkali metal hydroxide is 1:(0.5 - 1.5).
6. The method according to any one of claims 1-5, characterized in that, It also includes the step of adding S-1 seeds to water.
7. The method according to claim 6, wherein The size of the S-1 seeds is 40 - 30000 nm.
8. The method according to claim 6, characterized in that The mass ratio of the S-1 seeds to the silicon source is (0.01 - 0.5):
1.
9. An S-1 molecular sieve prepared by the method according to any one of claims 1 - 8.
10. Use of the S-1 molecular sieve according to claim 9 in adsorbing volatile organic compounds.