A method for preparing hydrogen-type sheet-like ZSM-5 molecular sieve

Abstract

The application provides a method for preparing hydrogen-type sheet ZSM-5 molecular sieve, and relates to the technical field of molecular sieve.The silicon source, the aluminum source, the structure directing agent (trimethylpentylammonium hydroxide and / or N-ethyl-N,N-dimethylbut-1-aminium hydroxide) and water are mixed, the obtained mixed solution is subjected to hydrothermal crystallization to obtain a crystallization product; the crystallization product is calcined to obtain the hydrogen-type sheet ZSM-5 molecular sieve.The trimethylpentylammonium hydroxide and / or N-ethyl-N,N-dimethylbut-1-aminium hydroxide are used as the structure directing agent, and the hydrogen-type sheet ZSM-5 molecular sieve is directly obtained after hydrothermal crystallization and calcination.The structure directing agent used in the application is cheap and easy to obtain, and the sodium-free synthesis of the hydrogen-type sheet ZSM-5 molecular sieve is realized, ion exchange and secondary calcination are not needed, so that the generation of a large amount of ion exchange waste liquid is avoided, and the energy consumption of secondary calcination is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a method for preparing hydrogen-type flaky ZSM-5 molecular sieves. Background Art

[0002] ZSM-5 molecular sieve is a typical three-dimensional pore 10-membered ring molecular sieve. a The axial direction has a 10-membered ring-shaped channel (5.5×5.1Å), along b ZSM-5 has a 10-membered ring straight pore with an axial diameter of (5.3 × 5.6 Å), exhibiting unique shape-selective catalytic properties and anisotropic mass transfer. Due to its high acid strength, adjustable acid site density, a wide Si / Al ratio window (10 to ∞), and excellent hydrothermal stability, it is widely used in chemical production. ZSM-5 is commonly used in catalytic processes such as alkane aromatization, aromatics alkylation, toluene disproportionation, isomerization reactions, naphtha / olefin catalytic cracking (FCC), methanol to gasoline (MTG), methanol to olefins (MTO), and biomass conversion.

[0003] Common hydrothermal synthesis of ZSM-5 molecular sieves mainly uses propylamine, hexamethylenediamine, diethylamine or tetrapropylammonium hydroxide as structure directing agents, or uses inorganic Rb under pure inorganic conditions. + When synthesized as a cation, the product molecular sieve size is in the micron range. During the catalytic reaction, the product often resides in the micropores for too long, leading to side reactions and carbon deposition and deactivation. The preparation of multi-level pore ZSM-5 molecular sieves containing both mesopores and micropores or the preparation of flaky ZSM-5 molecular sieves is an effective way to improve the catalytic activity, selectivity and catalyst life of ZSM-5 molecular sieves. Compared with multi-level pore molecular sieves, flaky molecular sieves often have a higher ordered structure and crystallinity, and have both hydrothermal stability and mechanical strength. Therefore, the preparation of flaky molecular sieves is more meaningful.

[0004] Currently, along a -axis growth of sheet-like ZSM-5 molecular sieves is mainly achieved by using surfactant-type structure-directing agents (such as C6H3([C6H4–OC n H 2n –N + (CH3)2–C6H 12 –N + (CH3)2C6H 13 ][Br – ]2)3) Gemini structure directing agent (such as C 18 H 37 -N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 (abbreviated as C 18-6-6), C 22 H 45 -N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 (abbreviation C 22-6-6 ), quaternary ammonium salt structure directing agent (such as C6H5-C6H4-O-C 10 H 20 N + (CH3)2-C6H 13 (Br - (abbreviation C Ph-Ph-10-6 ), quaternary phosphonium salt structure directing agent (such as 1,6-hexylene bis (trioctyl phosphonium bromide), 1,6-dodecylene bis (trioctyl phosphonium bromide)) or polycationic structure directing agent (such as polydipropylhexamethylene ammonium hydroxide, polydipropylpentamethylene dipropylheptamethylene ammonium hydroxide) are synthesized, and the above method is often difficult to realize large-scale industrial application due to long preparation period of structure directing agent and expensive raw materials. Moreover, the current method for synthesizing the flaky ZSM-5 molecular sieve generally needs to introduce sodium ions, which usually act as an alkali source and provide charge compensation. After hydrothermal crystallization and calcination to remove the structure directing agent, ion exchange and secondary calcination processes are required to obtain the hydrogen type ZSM-5 molecular sieve, which is complicated and produces a large amount of ion exchange waste liquid and increases the energy consumption of the calcination process. SUMMARY

[0005] Therefore, the present application aims to provide a method for preparing hydrogen type flaky ZSM-5 molecular sieve. The method provided by the present application uses inexpensive and readily available structure directing agent, and realizes the preparation of hydrogen type flaky ZSM-5 molecular sieve in a sodium-free system, which is simple and easy to industrialize.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] The present application provides a method for preparing hydrogen type flaky ZSM-5 molecular sieve, comprising the following steps:

[0008] (1) mixing a silicon source, an aluminum source, a structure directing agent and water, hydrothermally crystallizing the obtained mixed solution, and sequentially cooling, solid-liquid separating, solid phase washing and drying the obtained crystallization reaction liquid to obtain a crystallization product; the structure directing agent is trimethylpentylammonium hydroxide and / or N-ethyl-N,N-dimethylbutan-1-aminium hydroxide; the silicon source is calculated as SiO2, and the aluminum source is calculated as Al2O3, and the molar ratio of the silicon source, the aluminum source, the structure directing agent and water is 1:0.01:0.36:(29-58); the mixed solution does not contain sodium element; the temperature of the hydrothermal crystallization is 150-200℃, and the time is 1-5 days;

[0009] (2) calcining the crystallized product to obtain the hydrogen-type flaky ZSM-5 molecular sieve; the calcination temperature is 300-800° C., and the calcination time is 1-10 h.

[0010] Preferably, the silicon source includes tetraethyl orthosilicate and / or silica sol.

[0011] Preferably, the aluminum source comprises aluminum nitrate.

[0012] Preferably, the preparation method of trimethylpentylammonium hydroxide comprises the following steps:

[0013] (1) 1-bromopentane, trimethylamine and an organic solvent are mixed to undergo a nucleophilic substitution reaction to obtain trimethylpentyl ammonium bromide;

[0014] (2) The trimethylpentylammonium bromide is subjected to ion exchange through a strong alkaline anion exchange resin to obtain the trimethylpentylammonium hydroxide.

[0015] Preferably, the preparation method of N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide comprises the following steps:

[0016] (a) mixing N,N-dimethylethylamine, 1-bromobutane and an organic solvent to conduct a nucleophilic substitution reaction to obtain N-ethyl-N,N-dimethylbutyl-1-ammonium bromide;

[0017] (b) performing ion exchange on the N-ethyl-N,N-dimethylbutane-1-ammonium bromide through a strongly basic anion exchange resin to obtain the N-ethyl-N,N-dimethylbutane-1-ammonium hydroxide.

[0018] Preferably, the mixing method is:

[0019] performing a first mixing of the structure directing agent and water to obtain a first mixed solution;

[0020] performing a second mixing of the first mixed solution and an aluminum source to obtain a second mixed solution;

[0021] The second mixed liquid is mixed with a silicon source for a third time.

[0022] Preferably, the hydrothermal crystallization is carried out under dynamic conditions, and the dynamic conditions are rotating the mixed liquid at a rotation speed of 10-100 rpm.

[0023] The present invention provides a method for preparing hydrogenated flaky ZSM-5 molecular sieves. Compared with the prior art, the method has the following advantages: trimethylpentyl ammonium hydroxide and / or N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide are used as structure-directing agents. The structure-directing agents are removed by hydrothermal crystallization and calcination to directly obtain hydrogenated flaky ZSM-5 molecular sieves. The structure-directing agents used in the present invention are inexpensive and readily available. The method also enables sodium-free synthesis of hydrogenated flaky ZSM-5 molecular sieves, eliminating the need for ion exchange and secondary calcination, and directly obtaining hydrogenated flaky ZSM-5 molecular sieves. This avoids the generation of large amounts of ion exchange wastewater and reduces the energy consumption of secondary calcination. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the process for preparing hydrogen-type flaky ZSM-5 molecular sieve according to an embodiment of the present invention;

[0025] Figure 2 TMPA in Example 1 + of 13 C NMR spectrum;

[0026] Figure 3 TMPA in Example 1 + of 1 H NMR spectrum;

[0027] Figure 4 For EDMBA in Example 2 + of 13 C NMR spectrum;

[0028] Figure 5 For EDMBA in Example 2 + of 1 H NMR spectrum;

[0029] Figure 6 This is the XRD pattern of the hydrogen-type flaky ZSM-5 molecular sieve prepared in Example 3;

[0030] Figure 7 This is a scanning electron microscope image of the hydrogen-type flaky ZSM-5 molecular sieve prepared in Example 3. Figure 7 (a) and (b) are scanning electron microscope images at different scales;

[0031] Figure 8 This is the XRD pattern of the hydrogen-type flaky ZSM-5 molecular sieve prepared in Example 4;

[0032] Figure 9 This is a scanning electron microscope image of the hydrogen-type flaky ZSM-5 molecular sieve prepared in Example 4. Figure 9 (a) and (b) are scanning electron microscope images at different scales;

[0033] Figure 10 This is the XRD pattern of the ZSM-5 molecular sieve prepared in Comparative Example 1;

[0034] Figure 11 This is a scanning electron microscope image of the ZSM-5 molecular sieve prepared in Comparative Example 1. Figure 11 (a) and (b) are scanning electron microscope images at different scales;

[0035] Figure 12 This is the XRD pattern of the ZSM-5 molecular sieve prepared in Comparative Example 2;

[0036] Figure 13 This is a scanning electron microscope image of the ZSM-5 molecular sieve prepared in Comparative Example 2. Figure 13 (a) and (b) are scanning electron microscope images at different scales;

[0037] Figure 14 This is the XRD pattern of the ZSM-5 molecular sieve prepared in Comparative Example 3;

[0038] Figure 15 This is a scanning electron microscope image of the ZSM-5 molecular sieve prepared in Comparative Example 3. Figure 15 (a) and (b) are scanning electron microscope images at different scales. DETAILED DESCRIPTION

[0039] The present invention provides a method for preparing hydrogen-type flaky ZSM-5 molecular sieve, comprising the following steps:

[0040] (1) A silicon source, an aluminum source, a structure-directing agent and water are mixed, the obtained mixture is subjected to hydrothermal crystallization, and the obtained crystallization reaction liquid is sequentially cooled, solid-liquid separated, solid-phase washed and dried to obtain a crystallized product; the structure-directing agent is trimethylpentyl ammonium hydroxide and / or N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide; the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of the silicon source, the aluminum source, the structure-directing agent and water is 1:0.01:0.36:(29-58); the mixed solution does not contain sodium element; the temperature of the hydrothermal crystallization is 150-200°C, and the time is 1-5 days;

[0041] (2) calcining the crystallized product to obtain the hydrogen-type flaky ZSM-5 molecular sieve; the calcination temperature is 300-800° C., and the calcination time is 1-10 h.

[0042] Figure 1 The schematic diagram of the process for preparing hydrogen-type flaky ZSM-5 molecular sieve according to the embodiment of the present invention is shown below. Figure 1 Provide detailed explanation.

[0043] In the present invention, unless otherwise specified, all raw materials involved are commercially available products well known in the art.

[0044] The present invention mixes a silicon source, an aluminum source, a structure directing agent and water, performs hydrothermal crystallization on the obtained mixed solution, and sequentially cools, solid-liquid separates, solid-phase washes and dries the obtained crystallization reaction solution to obtain a crystallized product; the mixed solution does not contain sodium element.

[0045] In the present invention, the silicon source preferably includes ethyl orthosilicate and / or silica sol, and the silica sol is preferably neutral silica sol; the aluminum source preferably includes aluminum nitrate; and the water is preferably deionized water.

[0046] In the present invention, the structure-directing agent is trimethylpentyl ammonium hydroxide and / or N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide, and the structure-directing agent is a quaternary ammonium cationic compound with a chain length of 7 (including carbon and nitrogen elements). In the present invention, the structural formula of the trimethylpentyl ammonium hydroxide is shown in Formula I, where X1 - OH - The structural formula of the N-ethyl-N, N-dimethylbutyl-1-ammonium hydroxide is shown in Formula II, where X2 - OH - .

[0047] Formula I, Formula II.

[0048] The present invention has no particular requirements for the source of the structure-directing agent, and it can be prepared using commercially available products or methods well known to those skilled in the art; the structure-directing agent is inexpensive and readily available. In an embodiment of the present invention, the preparation method of trimethylpentyl ammonium hydroxide comprises the following steps:

[0049] (1) 1-bromopentane, trimethylamine and an organic solvent are mixed to undergo a nucleophilic substitution reaction to obtain trimethylpentyl ammonium bromide;

[0050] (2) The trimethylpentylammonium bromide is subjected to ion exchange through a strong alkaline anion exchange resin to obtain the trimethylpentylammonium hydroxide.

[0051] In the present application, in the step (1), the molar ratio of 1-bromopentane to trimethylamine is preferably 1:3; the organic solvent can be acetonitrile, and the present application does not have a particular requirement for the amount of the organic solvent, which can only ensure that the raw materials are dissolved and the reaction is smoothly carried out. In the present application, the method for mixing 1-bromopentane, trimethylamine and the organic solvent is preferably as follows: 1-bromopentane is added to the organic solvent, stirred at room temperature for 10 min, and then a trimethylamine solution is added dropwise; the trimethylamine solution is a solution of trimethylamine and the organic solvent. In the present application, the temperature of the nucleophilic substitution reaction is preferably 90℃, and the time is preferably 12 h, and the nucleophilic substitution reaction is preferably carried out under stirring. After the nucleophilic substitution reaction is completed, the obtained reaction liquid is preferably sequentially subjected to rotary evaporation, filtration, solid washing, filtration and drying to obtain trimethylpentylammonium bromide; the washing reagent used in the washing is preferably diethyl ether, which simultaneously plays a recrystallization role in the process of washing.

[0052] In the present application, in the step (2), the strong basic anion exchange resin can be 717 anion exchange resin. In the present application, the specific operation of the ion exchange is preferably as follows: the trimethylpentylammonium bromide, the 717 anion exchange resin and water are mixed for ion exchange. In the present application, the ion exchange is preferably repeated, and the number of times of the ion exchange is preferably 3 times; in each ion exchange, the mass ratio of trimethylpentylammonium bromide, 717 anion exchange resin and water is preferably 1:3:5, and the time of each ion exchange is preferably 24 h; after each ion exchange is completed, the 717 anion exchange resin is filtered out and an equal mass of 717 anion exchange resin is added. In the present application, after the ion exchange is completed, the trimethylpentylammonium hydroxide is obtained by sequentially performing filtration and rotary evaporation.

[0053] In the present application, the preparation method of the N-ethyl-N,N-dimethylbutan-1- ammonium hydroxide comprises the following steps:

[0054] (a) mixing N,N-dimethylethylamine, 1-bromobutane and an organic solvent to carry out a nucleophilic substitution reaction, to obtain N-ethyl-N,N-dimethylbutan-1- ammonium bromide;

[0055] (b) ion exchanging the N-ethyl-N,N-dimethylbutan-1-ammonium bromide through a strong basic anion exchange resin to obtain the N-ethyl-N,N-dimethylbutan-1-ammonium hydroxide.

[0056] In step (a) of the present invention, the molar ratio of N,N-dimethylethylamine to 1-bromobutane is preferably 1:3. The organic solvent can be acetonitrile. The amount of the organic solvent used is not particularly required, as long as the raw materials are dissolved and the reaction proceeds smoothly. In the present invention, the method for mixing N,N-dimethylethylamine, 1-bromobutane, and the organic solvent is preferably as follows: N,N-dimethylethylamine is added to the organic solvent, stirred at room temperature for 10 minutes, and then 1-bromobutane is added. In the present invention, the temperature for the nucleophilic substitution reaction is preferably 30°C, and the reaction time is preferably 48 hours. The nucleophilic substitution reaction is preferably carried out under stirring. After the nucleophilic substitution reaction is completed, the resulting reaction solution is preferably subjected to rotary evaporation, filtration, solid washing, filtration, and drying to obtain N-ethyl-N,N-dimethylbutyl-1-ammonium bromide. The washing agent used for washing the solid is preferably diethyl ether, which also serves as a recrystallization agent during the washing process.

[0057] In the present invention, the conditions and operation of the ion exchange in step (b) are the same as those in the above step (2), except that the trimethylpentyl ammonium bromide in step (2) is replaced by N-ethyl-N,N-dimethylbutyl-1-ammonium bromide, which will not be repeated here.

[0058] In the present invention, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of the silicon source, aluminum source, structure-directing agent, and water is 1:0.01:0.36:(29-58). The present invention adopts a sodium-free formulation system. In the present invention, the method of mixing the silicon source, aluminum source, structure-directing agent, and water is preferably:

[0059] performing a first mixing of the structure directing agent and water to obtain a first mixed solution;

[0060] performing a second mixing of the first mixed solution and an aluminum source to obtain a second mixed solution;

[0061] The second mixed liquid is mixed with a silicon source for a third time to obtain the mixed liquid (gel).

[0062] In the present invention, the first mixing, the second mixing and the third mixing are preferably stirred mixing, and the stirring mixing is based on uniform mixing of the raw materials; when the silicon source is a liquid, it can be added to the second mixed liquid in a dropwise manner; the first mixing, the second mixing and the third mixing can be carried out at room temperature, that is, no additional heating or cooling is required.

[0063] In the present application, the temperature of the hydrothermal crystallization is 150-200℃, which can be 150, 160, 170, 180, 190 or 200℃, and the time is 1-5 days, which can be 1, 2, 3, 4 or 5 days. In the present application, the mixture of the silicon source, the aluminum source, the structure-directing agent and water is transferred into a hydrothermal kettle, and then is placed in an oven for the hydrothermal crystallization. In the present application, the hydrothermal crystallization is preferably carried out under dynamic conditions, which are preferably that the mixture is rotated, specifically, the oven is selected as a dynamic oven, and the dynamic oven is kept rotating during the hydrothermal crystallization, and the rotation speed is preferably 10-100 rpm, which can be 50-80 rpm. The hydrothermal crystallization under dynamic conditions in the present application has the following advantages: (1) the reactants (the silicon source, the aluminum source and the structure-directing agent) can be mixed sufficiently, the uniformity is improved, the local concentration unevenness is avoided, the gel phase separation or component segregation is reduced, the product composition is ensured to be consistent, and the generation of impurities (such as amorphous silicon dioxide or non-target molecular sieve) is also reduced; (2) the mass transfer process is accelerated, and the crystallization time is shortened (compared with static conditions); (3) the crystal overgrowth or agglomeration is inhibited, and therefore smaller and more uniform crystal particles are obtained.

[0064] After the hydrothermal crystallization is completed, the crystallization reaction liquid obtained in the present application is sequentially subjected to cooling, solid-liquid separation, solid-phase washing and drying to obtain the crystallization product. The method of the solid-liquid separation in the present application is not particularly required, and the method well known to those skilled in the art can be used, such as filtration or suction filtration. In the present application, the washing reagent used in the washing is preferably deionized water and / or ethanol; the temperature of the drying is preferably 40-250℃, more preferably 60-150℃, and further preferably 100℃, and the time is preferably 8-30 h, more preferably 10-20 h, and the drying can be carried out under normal pressure or under reduced pressure.

[0065] In the synthesis of flaky ZSM-5 zeolites, the properties of the selected structure-directing agent, such as molecular size, shape, rigidity, hydrophilicity / hydrophobicity, and geometric compatibility with the zeolite framework, significantly influence their morphology and growth orientation. In sodium-free synthesis, quaternary ammonium cations, as the sole cations balancing the negative charge of the zeolite framework, also influence Al placement and acidity. By selecting suitable quaternary ammonium salts as structure-directing agents, developing green methods for the synthesis of sodium-free flaky ZSM-5 zeolites with low-cost raw materials, simple processes, and easy industrial conversion has great potential for application. The present invention adopts a quaternary ammonium cationic compound with a chain length of 7, namely trimethylpentyl ammonium hydroxide and / or N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide as a structure directing agent, and adopts a sodium-free synthesis formula to directly synthesize a sheet-like hydrogen-type ZSM-5 molecular sieve; the structure directing agent used in the present invention has the following functions: (1) charge balance and alkalinity regulation: in general molecular sieve synthesis, sodium ions usually have the function of serving as an alkali source and providing charge compensation. The structure directing agent used in the present invention itself has alkalinity or can release protons, and can adjust the pH value of the gel under sodium-free conditions. At the same time, it can directly balance the negative charge of the molecular sieve framework (such as AlO4) by releasing cations. - charge), replacing the role of sodium ions; (2) Geometric matching and template effect: The formation of sheet molecular sieves is usually related to the generation of layered intermediates. The molecular size and shape of the structure directing agent used in the present invention can highly match the layered structure of the molecular sieve, promote the anisotropic growth of the molecular sieve, and finally form a sheet morphology; (3) Reduce the interference of competing ions: Without the competition of sodium ions, the structure directing agent used in the present invention has a more prominent effect on charge balance or adsorption sites. For example, under sodium-free conditions, the cations of the structure directing agent can monopolize the negative charge sites of the molecular sieve framework, thereby enhancing its ability to direct specific structures.

[0066] After obtaining the crystallized product, the present invention calcines the crystallized product to obtain the hydrogen-type flaky ZSM-5 molecular sieve.

[0067] In the present invention, the calcination temperature is 300-800°C, preferably 400-650°C, more preferably 500-550°C, and can be 500, 510, 520, 530, 540, or 550°C, and the calcination time is 1-10 hours, preferably 5-8 hours, and can be 5, 6, 7, or 8 hours; the calcination is preferably carried out in an oxygen-containing atmosphere, preferably air or oxygen. The present invention removes the structure-directing agent through the calcination to obtain a hydrogen-type ZSM-5 molecular sieve.

[0068] The present invention adopts quaternary ammonium salt ions (trimethylpentyl ammonium hydroxide and / or N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide) as a structure-directing agent, adopts a sodium-free formula, and directly obtains hydrogen-type flaky ZSM-5 molecular sieves through hydrothermal crystallization and calcination. The operation is simple and convenient. After the template agent is removed by calcination, ion exchange and secondary calcination are unnecessary, which saves operating procedures, avoids the generation of a large amount of ion exchange waste liquid, and saves energy consumption in the calcination process.

[0069] To further illustrate the present invention, the method for preparing hydrogen-type flaky ZSM-5 molecular sieve provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0070] In the embodiment, the structure of the ZSM-5 molecular sieve is determined by an X-ray diffraction pattern (XRD), and the X-ray diffraction pattern (XRD) is measured by an X-ray powder diffractometer (model Panalytical X PERPRO, Cu Kα ray source (λ = 1.5418Å), nickel filter, 2θ scanning range 3 ~ 50 °, operating voltage 40kV, current 40mA, scanning rate 5 ° / min). Before the sample test, a scanning electron microscope (SEM, model S-4800II field emission scanning electron microscope) was used to observe the crystallization of the molecular sieve sample to confirm that the sample contained only one crystal, that is, the molecular sieve sample was pure phase. On this basis, the XRD test was performed to ensure that there was no interference peak of other crystals in the diffraction peak in the XRD spectrum.

[0071] Example 1

[0072] Preparation of structure-directing agent (trimethylpentyl ammonium hydroxide, TMPA-OH):

[0073] The raw material 1-bromopentane (0.1 mol) was added to 150 mL of acetonitrile and stirred at room temperature for 10 minutes to obtain a 1-bromopentane solution. Then, a 13 wt% trimethylamine solution in acetonitrile (0.3 mol of trimethylamine) was slowly added dropwise to the above 1-bromopentane solution and stirred at 90°C for 12 hours. The resulting reaction solution was then rotary evaporated and filtered. The filtered solid was washed with ether, filtered, and vacuum dried for 12 hours to obtain a white solid product - trimethylpentyl ammonium bromide (TMPA-Br).

[0074] At room temperature, TMPA-Br was mixed with 717 anion exchange resin and water for ion exchange three times (the mass ratio of TMPA-Br, 717 anion exchange resin and water for each ion exchange was 1:3:5, and the ion exchange time was 24 hours; after each exchange, the 717 anion exchange resin was filtered out and an equal mass of 717 anion exchange resin was added). The mixture was then filtered and rotary evaporated to obtain a hydroxide-type quaternary ammonium salt structure-directing agent, namely trimethylpentyl ammonium hydroxide, denoted as TMPA-OH. TMPA-OH was then added to deionized water to prepare a 50% solution.

[0075] TMPA + Separately 13 C. 1 H. Nuclear magnetic resonance detection, the results are as follows Figures 2-3 As shown, Figure 2 TMPA in Example 1 + of 13 C NMR spectrum, Figure 3 TMPA in Example 1 + of 1 H NMR spectrum.

[0076] Example 2

[0077] Preparation of structure-directing agent (N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide, EDMBA-OH):

[0078] The raw material N,N-dimethylethylamine (0.1 mol) was added to 150 mL of acetonitrile and stirred at room temperature for 10 minutes to obtain an N,N-dimethylethylamine solution. Then, 1-bromobutane (0.3 mol) was slowly added dropwise to the above N,N-dimethylethylamine solution and stirred at 30°C for 48 hours. The resulting reaction solution was then rotary evaporated and filtered. The filtered solid was washed with ether, filtered, and vacuum dried for 12 hours to obtain a white solid product - N-ethyl-N,N-dimethylbutyl-1-ammonium bromide (EDMBA-Br).

[0079] EDMBA-Br was mixed with 717 anion exchange resin and water at room temperature for ion exchange three times (the mass ratio of EDMBA-Br, 717 anion exchange resin and water was 1:3:5 for each ion exchange, and the time for each ion exchange was 24 hours; after each exchange, the 717 anion exchange resin was filtered out and an equal mass of 717 anion exchange resin was added). The mixture was then filtered and rotary evaporated to obtain a quaternary ammonium salt structure-directing agent in the hydroxide form, namely N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide, denoted as EDMBA-OH. EDMBA-OH was then added to deionized water to prepare a solution with a mass fraction of 50%.

[0080] About EDMBA+ Separately 13 C. 1 H NMR test results are as follows Figures 4-5 As shown, Figure 4 For EDMBA in Example 2 + of 13 C NMR spectrum, Figure 5 For EDMBA in Example 2 + of 1 H NMR spectrum.

[0081] Example 3

[0082] Preparation of hydrogen-type flaky ZSM-5 molecular sieve (process as follows Figure 1 shown):

[0083] 0.82 g of a 50 wt% solution of the structure-directing agent TMPA-OH (prepared in Example 1) and 7.62 g of deionized water were weighed and stirred at room temperature. Subsequently, 0.06 g of aluminum nitrate nonahydrate was added. After stirring for 2 h, 1.60 g of ethyl orthosilicate was slowly added dropwise as a silicon source and stirred to form a uniform gel. The molar ratio of the gel at this time was: SiO2:Al2O3:OSDA:H2O = 1:0.01:0.36:58, where OSDA represents the structure-directing agent.

[0084] The resulting gel was transferred to a 25 mL hydrothermal reactor and hydrothermally crystallized in a dynamic oven at 180°C (80 rpm) for 72 hours (3 days). The product was then cooled, filtered, washed with deionized water, dried (at atmospheric pressure, 100°C, 10 hours), and calcined in a muffle furnace (at air atmosphere, 550°C, 6 hours) to obtain hydrogen-type flaky ZSM-5 molecular sieve.

[0085] The XRD analysis of hydrogen-type flake ZSM-5 molecular sieve is as follows: Figure 6 As shown, it is a pure phase ZSM-5 molecular sieve.

[0086] Figure 7 This is an SEM image of the hydrogen-type flaky ZSM-5 molecular sieve prepared in Example 3. The molecular sieve exhibits a flat, polygonal, flaky structure with clear geometric outlines, straight edges, and a uniform thickness of 120-180 nm. This creates a unique two-dimensional morphology of "micrometer-level lateral dimensions and submicrometer-level thickness," combining large surface area with ultrathin properties. The particles are well dispersed, predominantly consisting of a single layer or a few loosely stacked layers with wide interlayer spacing.

[0087] Example 4

[0088] Preparation of hydrogen-type flaky ZSM-5 molecular sieve (process as follows Figure 1 shown):

[0089] 1.66 g of a 50 wt% solution of the structure-directing agent EDMBA-OH (prepared in Example 2) and 5.14 g of deionized water were weighed and stirred at room temperature. Subsequently, 0.12 g of aluminum nitrate nonahydrate was added. After stirring for 2 h, 3.13 g of neutral silica sol (SiO2 content 30 wt%) was slowly added dropwise as a silicon source and stirred to form a uniform gel. The molar ratio of the gel at this time was: SiO2:Al2O3:OSDA:H2O = 1:0.01:0.36:29, where OSDA represents the structure-directing agent.

[0090] The resulting gel was transferred to a 25 mL hydrothermal reactor and hydrothermally crystallized in a dynamic oven at 180°C (80 rpm) for 72 hours (3 days). The product was then cooled, filtered, washed with deionized water, dried (at atmospheric pressure, 100°C, 10 hours), and calcined in a muffle furnace (at air atmosphere, 550°C, 6 hours) to obtain hydrogen-type flaky ZSM-5 molecular sieve.

[0091] The XRD analysis of hydrogen-type flake ZSM-5 molecular sieve is as follows: Figure 8 As shown, it is a pure phase ZSM-5 molecular sieve.

[0092] Figure 9 This is an SEM image of the hydrogen-type flaky ZSM-5 molecular sieve prepared in Example 4. The resulting molecular sieve exhibits a highly regular polygonal flaky structure with remarkable geometric symmetry, with some particles exhibiting slightly curved edges. The flakes are uniformly thick, ranging from 90 to 190 nm, forming an ultrathin two-dimensional structure with lateral dimensions reaching several microns, creating a unique "large size with nanometer-scale thickness" morphology. The flakes are primarily loosely stacked, with parallel arrangement or slight misalignment between layers.

[0093] Comparative Example 1

[0094] 0.64 g of a 50 wt% solution of the structure-directing agent EDMBA-OH (prepared in Example 2) and 8.10 g of deionized water were weighed and stirred at room temperature. 0.05 g of aluminum nitrate nonahydrate was then added. After stirring for 2 h, 1.21 g of neutral silica sol (SiO2 content 30 wt%) was slowly added dropwise as a silicon source and stirred to form a uniform gel. The molar ratio of the gel at this time was: SiO2:Al2O3:OSDA:H2O = 1:0.01:0.36:85, where OSDA represents the structure-directing agent.

[0095] The resulting gel was transferred to a 25 mL hydrothermal reactor and hydrothermally crystallized in a dynamic oven at 180°C (80 rpm) for 72 hours (3 days). The product was then cooled, filtered, washed with deionized water, dried (at atmospheric pressure, 100°C, 10 hours), and calcined in a muffle furnace (air atmosphere, 550°C, 6 hours) to obtain ZSM-5 molecular sieve.

[0096] The ZSM-5 molecular sieve obtained in Comparative Example 1 was subjected to XRD analysis, and the results were as follows: Figure 10 As shown, it is a pure phase ZSM-5 molecular sieve.

[0097] Figure 11 This is an SEM image of the ZSM-5 molecular sieve prepared in Comparative Example 1. At the 10μm scale, a large number of small particles are visible, with uneven size and irregular shape, indicating poor control of the crystallization process and low crystallinity. Observation at the 2μm scale reveals chaotic crystal growth orientation, lack of a distinct regular morphology, a rough surface, and numerous defects. Overall, the sample contains a small amount of incompletely developed short columnar crystals, as well as a large number of amorphous or microcrystalline particles.

[0098] Comparative Example 2

[0099] 1.38 g of a 40 wt% aqueous solution of the structure-directing agent tetrapropylammonium hydroxide (TPAOH) and 7.02 g of deionized water were weighed and stirred at room temperature. Subsequently, 0.06 g of aluminum nitrate nonahydrate was added. After stirring for 2 h, 1.57 g of ethyl orthosilicate was slowly added dropwise as a silicon source and stirred to form a uniform gel. The molar ratio of the gel at this time was: SiO2:Al2O3:OSDA:H2O=1:0.01:0.36:58, where OSDA represents the structure-directing agent;

[0100] The resulting gel was transferred to a 25 mL hydrothermal reactor and hydrothermally crystallized in a dynamic oven at 180°C (80 rpm) for 72 hours (3 days). The product was then cooled, filtered, washed with deionized water, dried (normal pressure, 100°C, 10 hours), and calcined in a muffle furnace (air atmosphere, 550°C, 6 hours) to obtain ZSM-5 molecular sieve.

[0101] The ZSM-5 molecular sieve obtained in Comparative Example 2 was subjected to XRD analysis, and the results were as follows: Figure 12 As shown, it is a pure phase ZSM-5 molecular sieve.

[0102] Figure 13SEM image of ZSM-5 molecular sieve prepared for Comparative Example 2. The molecular sieve presents regular crystal morphology, mainly short columnar or hexagonal structure, uniform size distribution, lateral size of 1.6-2.2 μm, uniform thickness, smooth particle surface, clear edges and corners, and no obvious agglomeration phenomenon.

[0103] Comparative Example 3

[0104] 0.82 g of a 50 wt% solution of structure-directing agent TMPA-OH (prepared in Example 1), 7.62 g of deionized water and 0.03 g of NaOH solid were weighed and stirred at room temperature, followed by addition of 0.06 g of aluminum nitrate nonahydrate, and 1.60 g of tetraethyl orthosilicate as a silicon source was slowly added dropwise after stirring for 2 h to form a uniform gel, the molar ratio of the gel at this time was SiO2:Al2O3:OSDA:H2O:NaOH = 1:0.01:0.36:58:0.1, wherein OSDA represents a structure-directing agent;

[0105] The obtained gel was transferred to a hydrothermal kettle with a volume of 25 mL and hydrothermally crystallized in a dynamic oven (dynamic oven rotation speed of 80 rpm) at 180°C for 72 h (3 days). After cooling, filtration, deionized water washing, drying (normal pressure, 100°C, 10 h), and calcination in a muffle furnace (air atmosphere, calcination temperature of 550°C, time of 6 h), ZSM-5 molecular sieve was obtained.

[0106] The ZSM-5 molecular sieve obtained in Comparative Example 3 was subjected to XRD analysis, and the results are shown in Figure 14 , which is a pure-phase ZSM-5 molecular sieve.

[0107] Figure 15 SEM image of ZSM-5 molecular sieve prepared for Comparative Example 3. The molecular sieve presents regular rectangular prismatic or polygonal shape, clear geometric contour, lateral size of most particles distributed in the range of 4-8 μm, uniform longitudinal thickness, and part of the crystals arranged in parallel or staggered manner to form an ordered laminated structure.

[0108] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing hydrogen-type flaky ZSM-5 molecular sieve, characterized in that: The following steps are involved: (1) A silicon source, an aluminum source, a structure-directing agent and water are mixed, the obtained mixture is subjected to hydrothermal crystallization, and the obtained crystallization reaction liquid is sequentially cooled, solid-liquid separated, solid-phase washed and dried to obtain a crystallized product; the structure-directing agent is trimethylpentyl ammonium hydroxide and / or N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide; the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of the silicon source, the aluminum source, the structure-directing agent and water is 1:0.01:0.36:(29-58); the mixed solution does not contain sodium element; the temperature of the hydrothermal crystallization is 150-200°C, and the time is 1-5 days; (2) calcining the crystallized product to obtain the hydrogen-type flaky ZSM-5 molecular sieve; the calcination temperature is 300-800° C., and the calcination time is 1-10 h.

2. The method according to claim 1, characterized in that The silicon source includes tetraethyl orthosilicate and / or silica sol.

3. The method according to claim 1, characterized in that The aluminum source includes aluminum nitrate.

4. The method according to claim 1, wherein The preparation method of the trimethylpentylammonium hydroxide comprises the following steps: (1) 1-bromopentane, trimethylamine and an organic solvent are mixed to undergo a nucleophilic substitution reaction to obtain trimethylpentyl ammonium bromide; (2) The trimethylpentylammonium bromide is subjected to ion exchange through a strong alkaline anion exchange resin to obtain the trimethylpentylammonium hydroxide.

5. The method according to claim 1, wherein The preparation method of the N-ethyl-N,N-dimethylbutyl-1-ammonium hydroxide comprises the following steps: (a) mixing N,N-dimethylethylamine, 1-bromobutane and an organic solvent to conduct a nucleophilic substitution reaction to obtain N-ethyl-N,N-dimethylbutyl-1-ammonium bromide; (b) performing ion exchange on the N-ethyl-N,N-dimethylbutane-1-ammonium bromide through a strongly basic anion exchange resin to obtain the N-ethyl-N,N-dimethylbutane-1-ammonium hydroxide.

6. The method according to any one of claims 1 to 5, characterized in that The mixing method is: performing a first mixing of the structure directing agent and water to obtain a first mixed solution; performing a second mixing of the first mixed solution and an aluminum source to obtain a second mixed solution; The second mixed liquid is mixed with a silicon source for a third time.

7. The method according to claim 1, characterized in that The hydrothermal crystallization is carried out under dynamic conditions, wherein the dynamic conditions are to rotate the mixed solution at a rotation speed of 10 to 100 rpm.

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