Preparation method and application of a multi-level pore zsm-5 nanosheet zeolite

Abstract

The application discloses a preparation method of nano-flower-like ZSM-5 nanosheet zeolite. The preparation method comprises the following steps: mixing an aluminum source solution and a silicon source to obtain a gel, and adjusting the pH of the gel to be 7-10; after aging of the obtained gel, the gel is mixed with a long carbon chain surfactant and a non-ionic surfactant, and then hydrothermal reaction is carried out after the mixing, so that crystals are precipitated; and the obtained crystals are dried and calcined to obtain the ZSM-5 nanosheet zeolite. The method is simple and low in cost. The synthesized product has a widely adjustable silicon-aluminum ratio, an ordered adjustable mesoporous structure, a mesopore size adjustable between 5-20 nm, and a nanosheet thickness reducible to about 10 nm, and meanwhile, the nanosheets are column-supported, and have excellent stability, so that the product has a better application prospect in the field of catalysis.

Description

Technical Field

[0001] This application belongs to the field of catalysts, specifically relating to a method for preparing hierarchical porous ZSM-5 nanosheet zeolite. Background Technology

[0002] Hierarchical porous ZSM-5 zeolite molecular sieves retain the advantages of microporous molecular sieves, such as tunable acidity and good hydrothermal stability. Simultaneously, by introducing mesopores, they overcome limitations in mass transfer and diffusion. Therefore, hierarchical porous ZSM-5 zeolite exhibits stronger macromolecular diffusion performance while ensuring high conversion rates, guaranteeing catalyst stability and high catalytic reaction performance, thus demonstrating excellent application prospects and economic benefits. Among them, ZSM-5 nanosheet zeolite, due to its larger specific surface area, more exposed active sites, and shorter diffusion paths, shows extremely high application potential in catalytic reactions, especially catalytic cracking reactions.

[0003] The main methods for preparing nanosheet molecular sieves include: the additive method, the ammonium fluoride-assisted method, and the template method. The additive method typically involves adding organic additives such as urea or glucose to the system to regulate crystal growth and obtain nanosheet molecular sieves. The ammonium fluoride-assisted method uses fluoride ions instead of hydroxide ions as mineralizing agents to synthesize nanosheet molecular sieves. However, the thickness of nanosheets prepared by these two methods is usually in the range of 100-450 nm, making it difficult to reduce the nanosheet thickness to the unit cell level. The template method can prepare nanosheet molecular sieves with unit cell-level thickness. The most representative work in this area is that Ryoo et al. prepared hierarchical porous ZSM-5 nanosheet zeolite by designing a dual-headed quaternary ammonium salt surfactant (C22) as a mesoporous template agent, achieving a nanosheet thickness as low as 2 nm. Che et al. also synthesized MFI nanosheets with a nanosheet thickness of approximately 3 nm by designing a single quaternary ammonium-headed surfactant as a template agent, where the aromatic groups of the surfactant formed layered micelles through π-π interactions. The special template agent method can achieve the synthesis of cell-level nanosheet molecular sieves by designing template agents with special structures. The main problems at present are that special template agents need to be directionally designed and synthesized, the synthesis steps are complicated and the synthesis cost is high. At the same time, the synthesized nanosheets are prone to collapse, which greatly limits the industrial application of this method.

[0004] Therefore, finding an economical, simple, and efficient method for preparing ZSM-5 nanosheet zeolite is of great application value. Summary of the Invention

[0005] One objective of this application is to improve the preparation method of ZSM-5 nanolayered zeolite and reduce the preparation cost of ZSM-5.

[0006] Another objective of this application is to improve the morphology of ZSM-5 nanosheet zeolite and enhance its stability.

[0007] Another objective of this application is to use the ZSM-5 nanosheet zeolite prepared in this application in the olefin catalytic cracking reaction system, thereby improving the selectivity and stability of ethylene and propylene.

[0008] A method for preparing ZSM-5 nanolayered zeolite, comprising:

[0009] (1) The aluminum source solution and the silicon source were mixed to obtain a gel.

[0010] (2) Adjust the pH of the gel to 7-10;

[0011] (3) After aging, the gel obtained in step (2) is mixed with long-chain surfactant and non-ionic surfactant. After mixing, a hydrothermal reaction is carried out to precipitate crystals. The crystals are dried and calcined to obtain ZSM-5 nanosheet zeolite.

[0012] The long-chain surfactant includes one or a mixture of two or more of tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

[0013] In the preparation of ZSM-5 nanolayered zeolite, a one-step method can be used to synthesize ZSM-5 zeolite with a nanoflower morphology, effective pillars between the nanosheets, and good stability by using long-chain trimethyl quaternary ammonium salt and nonionic surfactant.

[0014] The ZSM-5 nanolayered zeolite prepared by the above method is used in the reaction system of olefin catalytic cracking. This ZSM-5 nanolayered zeolite exhibits excellent stability and, due to its specific morphology and structural characteristics, can significantly improve the selectivity for ethylene and propylene. Attached Figure Description

[0015] Figure 1 These are the small-angle and wide-angle XRD patterns of the catalysts prepared in Examples 1 to 3 of this invention.

[0016] Figure 2 The image shows the mesopore distribution of the catalysts prepared in Examples 1-3 of this invention.

[0017] Figure 3 This is a scanning electron microscope image of the nanosheet molecular sieve prepared in Example 1 of the present invention.

[0018] Figure 4 This is a scanning electron microscope image of the molecular sieve sample prepared in Comparative Example 1 of the present invention.

[0019] Figure 5 This is a scanning electron microscope image of the molecular sieve sample prepared in Comparative Example 2 of the present invention.

[0020] Figure 6 This is a scanning electron microscope image of the molecular sieve sample prepared in Comparative Example 3 of the present invention.

[0021] Figure 7 This is a scanning electron microscope image of the nanosheet molecular sieve prepared in Example 2 of the present invention.

[0022] Figure 8 This is a scanning electron microscope image of the nanosheet molecular sieve prepared in Example 3 of the present invention.

[0023] Figure 9 Transmission electron microscopy of the nanosheet molecular sieve prepared in Example 1 of this invention. Detailed Implementation

[0024] The preparation method of the ZSM-5 nanolayered zeolite of the present invention and its application are described in further detail below. This does not limit the scope of protection of this application, which is defined by the claims. Certain specific details disclosed provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented using other materials, etc., without employing one or more of these specific details.

[0025] Unless the context otherwise requires, the terms “comprising” and “including” in the specification and claims shall be understood as open-ended and inclusive, meaning “including, but not limited to”.

[0026] The terms "implementation," "an implementation," "another implementation," or "certain implementations" used in this specification refer to specific features, structures, or characteristics described in relation to the implementation, which are included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0028] The units in the weight-volume percentages of this invention are well known to those skilled in the art, for example, referring to the weight of the solute in 100 ml of solution.

[0029] In this invention, the concentration unit "M" of the solution represents mol / L.

[0030] The term "roasting" refers to the process of treating a substance at high temperatures in an air atmosphere.

[0031] The term "aging" refers to leaving something to stand at a certain temperature for a period of time.

[0032] In this application, the amount of silicon source used is calculated as SiO2.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0034] Long-chain alkyl trimethyl quaternary ammonium salts or bases are commonly used template agents in the synthesis of mesoporous molecular sieves (MCM series). As mesoporous template agents and small-molecule organic template agents, they work synergistically with seed crystals in the synthesis of hierarchical porous molecular sieves, yielding nanoparticle aggregate structures. The addition of long-chain trimethyl quaternary ammonium salts inhibits grain growth, ultimately resulting in nanoparticle aggregate morphology and structures that are not ultrathin nanosheet structures.

[0035] The inventors unexpectedly discovered that adding long-chain alkyl trimethyl quaternary ammonium salts and nonionic surfactants (such as X-100) to a hydrothermal synthesis system alters the morphology of the resulting MFI molecular sieve, leading to the formation of ultrathin nanoflower-shaped hierarchical porous MFI topological molecular sieves.

[0036] A method for preparing ZSM-5 nanolayered zeolite, comprising:

[0037] (1) Mix the aluminum source solution with the silicon source to form a gel;

[0038] (2) Adjust the pH of the gel from step (1) to 7-10;

[0039] (3) After the gel aging in step (2), it is mixed with long-chain surfactant and non-ionic surfactant. After mixing, a hydrothermal reaction is carried out to precipitate crystals. The crystals are dried and calcined to obtain ZSM-5 nanosheet zeolite.

[0040] The long-chain surfactant includes one or a mixture of two or more of tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

[0041] The nonionic surfactant is one or a mixture of two or more of Triton X-100 (i.e., TX-100), alkylphenol polyoxyethylene ether (i.e., TX-10), nonylphenol polyoxyethylene ether (10) (i.e., NP-10) or octylphenol ether-10 (i.e., OP-10).

[0042] In some embodiments, the molar ratio of silicon source to long-chain surfactant is 100:(3-10).

[0043] The molar ratio of silicon source to nonionic surfactant is 100:(1-3).

[0044] The ZSM-5 molecular sieve prepared by the synergistic effect of long-chain surfactants and nonionic surfactants exhibits a nanoflower-like morphology and excellent stability. Especially within the aforementioned dosage range, the resulting ZSM-5 nanosheet molecular sieve shows an ordered mesopore distribution with a pore size that can be controllably adjusted within the range of 5-20 nm, demonstrating excellent catalytic performance in olefin catalytic cracking reaction systems.

[0045] In some implementations, the molar ratio of silicon source to aluminum source is 100:(0.3-2). That is, the molar ratio of Si element to Al element is 100:(0.3-2).

[0046] Preferably, the molar ratio of Si to Al is approximately 90.

[0047] In the hot water reaction, the molar ratio of silicon source to water is 100:(1800-4000).

[0048] The silicon source includes: water glass, silica sol, methyl silicate, and / or ethyl silicate, etc.

[0049] The aluminum source includes soluble aluminum salts such as aluminum sulfate and aluminum chloride.

[0050] In some embodiments, in step (2), the pH can be adjusted to 7-10 by adding an alkaline or / and acidic solution.

[0051] In some embodiments, the temperature of the hydrothermal reaction in step (3) is controlled at 120-180°C.

[0052] The crystallization time is 12h-72h.

[0053] The roasting temperature is 550-650℃. The roasting time is 2-8 hours.

[0054] Typically, the crystals precipitated after the hydrothermal reaction are washed, dried, and then calcined. The drying temperature is controlled between 80-120℃. It is only necessary to control the water content of the solid within a certain range.

[0055] In some embodiments, the aging process in step (3) is carried out at a temperature of 40-80°C.

[0056] ZSM-5 nanosheet zeolite, obtained after subsequent drying and calcination at temperatures of 40-80℃, exhibits better catalytic performance and a longer service life when applied in olefin catalytic cracking reaction systems.

[0057] Aging time: 8-12 hours.

[0058] The ZSM-5 molecular sieve prepared by the above method possesses a nanoflower structure with nanosheet thicknesses ranging from 4 to 10 nm. This molecular sieve exhibits good stability, maintaining its nanoflower structure even under prolonged high-temperature use without collapse. Its internal structure and properties, in particular, demonstrate excellent performance in olefin catalytic cracking reaction systems, exhibiting high selectivity for small molecule olefins and a long service life.

[0059] On the other hand, the ZSM-5 nanosheet zeolite prepared in this application is used in the olefin catalytic cracking reaction system.

[0060] Under the action of the ZSM-5 nanosheet zeolite obtained by the above preparation method, olefins undergo a cracking reaction at a reaction temperature of 500-550℃.

[0061] Preferably, the reaction pressure is approximately 1 atm (one standard atmosphere);

[0062] More preferably, the mass hourly space velocity is about 6-10 h. -1 .

[0063] The olefins include monoolefins, preferably C4-C8 monoolefins, such as pentene, hexene, heptene, and octene. C4-C8 olefins are often byproducts of many processes, making their use as raw materials for catalytic cracking more practically significant.

[0064] The ZSM-5 nanosheet zeolite prepared in this application can significantly improve the combined selectivity of ethylene and propylene in the catalytic cracking of olefins, and has a long service life.

[0065] The ZSM-5 nanolayered zeolite of the present invention and its catalytic effect are further illustrated below with specific embodiments. All substances used in the following embodiments are chemically pure standards.

[0066] The nonionic surfactant TX-100 in the examples is composed of polyethylene glycol octylphenyl ether and has a viscosity of 24 × 10⁻⁶. - 3 Pa·s.

[0067] Example 1

[0068] Weigh 1.2g of aluminum sulfate octadechydrate, 1.8g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 30. After aging the gel at 60℃ for 12h, add 2.5g of octadecyltrimethylammonium bromide and 3.5g of TX-100 to the aged gel, stir for 1h, and then transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product, and then calcine the dried solid product in a muffle furnace at 550℃ for 6h to obtain ZSM-5 nanosheet zeolite.

[0069] Example 2

[0070] Weigh 1.2g of aluminum sulfate octadechydrate, 1.8g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 30. After aging the gel at 60℃ for 12h, add 2.5g of octadecyltrimethylammonium bromide and 1.8g of TX-100 to the aged gel and stir for 1h. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6h to obtain hierarchical porous ZSM-5 nanosheet zeolite.

[0071] Example 3

[0072] Weigh 1.2g of aluminum sulfate octahydrate, 1.8g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 30. After aging the gel at 60℃ for 12h, add 2.5g of hexadecyltrimethylammonium bromide and 0.9TX-100 to the aged gel and stir for 1h. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6h to obtain hierarchical porous ZSM-5 nanosheet zeolite.

[0073] Example 4

[0074] Weigh out 0.6g of aluminum sulfate octahydrate, 2.1g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 60. After aging the gel at 60℃ for 12h, add 2.5g of hexadecyltrimethylammonium bromide and 3.5g of TX-100 to the aged gel and stir for 1h. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6h to obtain hierarchical porous ZSM-5 nanosheet zeolite.

[0075] Example 5

[0076] Weigh 0.39g of aluminum sulfate octahydrate, 2.5g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 90. After aging the gel at 60℃ for 12h, add 2.5g of hexadecyltrimethylammonium bromide and 3.5g of TX-100 to the aged gel and stir for 1h. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6h to obtain hierarchical porous ZSM-5 nanosheet zeolite.

[0077] Example 6

[0078] Weigh 0.85g sodium aluminate, 2.0g nitric acid, and 15g deionized water, mix and stir until completely dissolved. Dissolve 2.4g sodium hydroxide in 10g water, stirring until completely dissolved to form a clear liquid. Add the sodium hydroxide solution dropwise to the aluminum solution, stir, and then add 30g silica sol (40%) to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 20. After aging the gel at 60℃ for 12h, add 2.5g hexadecyltrimethylammonium bromide and 3.5g TX-100 to the aged gel, stir for 1h, and then transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product, and then calcine the dried solid product in a muffle furnace at 550℃ for 6h to obtain hierarchical porous ZSM-5 nanosheet zeolite.

[0079] Comparative Example 1

[0080] The ingredient ratio and crystallization process are the same as in Example 1, except that only long-chain alkyltrimethylammonium bromide is added.

[0081] Weigh 1.2g of aluminum sulfate octahydrate, 1.8g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 60. After aging the gel at 60℃ for 12 hours, add 2.5g of hexadecyltrimethylammonium bromide to the aged gel and stir for 1 hour. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6 hours to remove the template agent, obtaining molecular sieve powder.

[0082] Comparative Example 2

[0083] The ingredient ratio and crystallization process are the same as in Example 1, except that only the nonionic surfactant TX-100 is added.

[0084] Weigh 1.2g of aluminum sulfate octadechydrate, 1.8g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 60. After aging the gel at 60℃ for 12 hours, add 3.5g of TX-100 to the aged gel and stir for 1 hour. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6 hours to obtain molecular sieve powder.

[0085] Comparative Example 3

[0086] Weigh out 0.39g of aluminum sulfate octahydrate, 2.5g of sulfuric acid, and 18g of deionized water, mix and stir until completely dissolved. Add 25g of water glass (containing 30% SiO2 and 9% Na2O) and 10g of deionized water, and stir until homogeneous to form a gel. The pH of the gel is approximately 7, and the Si / Al ratio is 90. After aging the gel at 90℃ for 12h, add 2.5g of hexadecyltrimethylammonium bromide and 3.5g of TX-100 to the aged gel and stir for 1h. Transfer the stirred gel to a polytetrafluoroethylene-lined reactor for crystallization treatment at 140℃ for 3 days. After crystallization, wash and dry the resulting solid product. Place the dried solid product in a muffle furnace and calcine at 550℃ for 6h to obtain ZSM-5 molecular sieve raw powder.

[0087] Experimental Example 1

[0088] This experimental example analyzes the small-angle and wide-angle XRD spectra of the ZSM-5 nanolayered zeolite prepared in Examples 1-3, such as... Figure 1 As shown in the right-hand wide-angle XRD pattern, all samples exhibit MFI-type structural characteristic peaks, indicating good crystallinity. The left-hand small-angle XRD results show a diffraction peak between peaks 2 and 3 in all three synthesized samples, suggesting pillar-like support between the nanosheets and better sample stability. Similarly, XRD analysis of the products from Examples 4-5 revealed similar characteristic peaks.

[0089] Experimental Example 2

[0090] In this experiment, the specific surface area, pore volume and pore size distribution of the samples in Examples 1-5 and Comparative Examples 1-3 were analyzed using a Mack Physical Adsorption Analyzer 2460, as shown in Table 1. The examples all have larger specific surface area and pore volume.

[0091] The results are as follows Figure 2 As shown, the mesopore distribution of ZSM-5 nanolayered zeolite is tunable from 5 to 20 nm. Table 1 shows the pore properties of the catalysts prepared in Examples 1-5.

[0092]

[0093] Experimental Example 3

[0094] This experimental example demonstrates scanning electron microscopy analysis of the ZSM-5 nanolayered zeolites prepared in Examples 1-3, as shown in the attached figure. Figure 3 , Figure 7 and Figure 8 As shown in the figure, the morphology of the samples is petal-shaped ultrathin nanosheets. The thickness of the nanosheets can be adjusted by changing the ratio of long-chain alkyl trimethyl quaternary ammonium salt and TX-100.

[0095] Figure 9 This is a transmission electron microscope image of the nanosheet molecular sieve prepared in Example 1.

[0096] Scanning electron microscopy analysis was performed on the ZSM-5 zeolites prepared in Comparative Examples 1-3, as shown in the attached figures. Figure 4 , 5 And 6. The ZSM-5 zeolite samples of Comparative Examples 1, 2, and 3 have significantly different grain morphologies from the ultrathin nanofloral flakes of Example 1. Comparative Example 1 consists of spherical nanoparticle aggregates with an average size of approximately 600 nm. SEM characterization results are shown in Figure 6. Figure 4 .

[0097] The ZSM-5 zeolite sample of Comparative Example 2 has a significantly different grain morphology from the ultrathin nanofloral flakes of Example 1. It consists of large hexagonal grains with an average size of approximately 1 μm. The SEM characterization results are shown in [Figure / Image]. Figure 5 .

[0098] The ZSM-5 zeolite sample in Comparative Example 3 exhibits a significantly different grain morphology from the ultrathin nanoflakes in Example 1. It consists of elliptical spherical particles with an average size of approximately 600 nm. SEM characterization results are shown below. Figure 6 .

[0099] Experiment Example 4

[0100] This experiment tested the catalytic performance of ZSM-5 nanolayered zeolites prepared in Examples 1-5 and Comparative Examples 1-3.

[0101] The obtained zeolite tablets were ground to a fineness of 40–80 mesh. 1.0 g of sample was weighed and loaded into a fixed-bed reactor for catalytic cracking reaction evaluation, using 1-hexene as the raw material, at a reaction temperature of 550 °C and a space velocity of 6 h⁻¹. -1 The evaluation results are shown in Table 2.

[0102] Table 2 shows the distribution of major products in the examples and comparative examples.

[0103]

[0104] The conversion rates of Examples 1-5 and Comparative Examples 1-3 of this application are above 95%. The catalyst lifetime in Table 2 refers to the time during which the 1-hexene conversion is maintained above 95%.

Claims

1. An application of ZSM-5 nanolayered zeolite in an olefin catalytic cracking reaction system, comprising: Under the action of ZSM-5 nanosheet zeolite, C4-C8 monoolefins undergo cracking reaction at a reaction temperature of 500-550℃. The preparation method of the ZSM-5 nanolayered zeolite includes: (1) The aluminum source solution and the silicon source are mixed to obtain a gel. (2) Adjust the pH of the gel to 7-10; (3) After aging the gel obtained in step (2) at 40-80℃ for 8-12 hours, it is mixed with long-chain surfactant and non-ionic surfactant. After mixing, a hydrothermal reaction is carried out to precipitate crystals. The crystals are dried and calcined to obtain ZSM-5 nanosheet zeolite. The long-chain surfactant includes one or a mixture of two or more of tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide; The nonionic surfactant is one or a mixture of two or more of Triton X-100, alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether-10 and octylphenol ether-10. The molar ratio of silicon source to long-chain surfactant is 100:(3-10), and the molar ratio of silicon source to nonionic surfactant is 100:(1-3).

2. The application according to claim 1, characterized in that, The long-chain surfactant is hexadecyltrimethylammonium bromide or octadecyltrimethylammonium bromide.

3. The application according to claim 1, characterized in that, The molar ratio of Si to Al is 100:(0.3-2).

4. The application according to claim 1, characterized in that, The molar ratio of Si to Al is 90.

5. The application according to any one of claims 1-4, characterized in that, The temperature of the hydrothermal reaction in step (3) is controlled at 120-180℃.

6. The application according to any one of claims 1-4, characterized in that, The roasting temperature is 550-650℃.

7. The application of claim 4 according to any one of claims 1-4, characterized in that, The olefins are pentene, hexene, hepten, or octene.

8. The application according to claim 1, characterized in that, The reaction pressure is 1 atm.

9. The application according to claim 1 or 8, characterized in that, Mass hourly space velocity is 6-10 h -1 .

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