Preparation method of hierarchical pore zeolite

Abstract

The invention belongs to the technical field of zeolite catalysts, and particularly relates to a preparation method of hierarchical pore zeolite. Through a high-silicon / pure-silicon seed crystal-selective etching synergistic strategy, in a synthesis stage, more than 30% of high-silicon (silica-alumina ratio (SAR) is greater than or equal to 500) or pure-silicon (SAR-infinity) seed crystals are introduced into a gel system, and most of the seed crystals are ensured to be embedded into a product skeleton in a complete form; in the post-treatment stage, the high-silicon seed crystal area is etched preferentially through an alkaline solution, mesopores are directionally generated, meanwhile, a matrix micropore structure is reserved, and precise customization of the hierarchical pore structure is achieved. The mesopore volume of the prepared hierarchical pore zeolite reaches 0.35 cm < 3 > / g or above, the external specific surface area is increased (180-220 m < 2 > / g vs traditionally smaller than 120 m < 2 > / g), pollution of toxic template agents is avoided, and the method is suitable for large-scale production of multiple types of zeolite such as ZSM-5 and Beta.

Description

Technical Field

[0001] The present invention belongs to the technical field of zeolite catalysts, and more particularly relates to a method for preparing hierarchical pore zeolite. Background Art

[0002] Hierarchical pore molecular sieves (with both micropores and mesopores) have shown significant advantages in catalysis, adsorption, and separation due to their unique pore structure. For example, in petroleum catalytic cracking, micropores (0.3-1nm) provide shape-selective catalytic active sites, while mesopores (2-50nm) can accelerate the mass transfer of macromolecular reactants and reduce carbon deposition and deactivation. However, traditional molecular sieves (such as ZSM-5) only have a microporous structure, and a single microporous structure is difficult to meet the needs of macromolecular catalytic reactions. Therefore, the controllable synthesis of hierarchical pore structures has become a research hotspot in the field of zeolite catalysts.

[0003] Currently, the preparation methods for hierarchical zeolites mainly include hard templates, soft templates, and post-treatment methods, but all have limitations. The hard template method introduces hard templates such as carbon nanospheres and polymer microspheres to occupy the space. After the molecular sieve crystallizes, the templates are removed to form mesopores. However, hard templates generally require high-temperature calcination (>500°C) to remove, which is expensive and difficult to scale up industrially. The soft template method uses surfactants (such as CTAB, P123, or organosilane coupling agents) as mesoporous templates to form a mesoporous structure through self-assembly. However, soft templates are expensive, and the resulting mesopores are often worm-like, with poor connectivity, low mass transfer efficiency, and toxicity. The post-treatment method involves treating the molecular sieve with alkali or acid to remove silicon and aluminum to form mesopores. However, due to the random distribution of silicon and aluminum in the zeolite synthesis product, this method can lead to uneven mesopore distribution, with some areas over-dissolving to form large pores (>50 nm), destroying the microporous structure. Therefore, there is an urgent need to develop a green and low-cost method for synthesizing hierarchical zeolites. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing hierarchical pore zeolite. The present invention adopts a "high silicon / pure silicon seed-selective etching" synergistic strategy. In the synthesis stage, >30% high silicon (silicon-aluminum ratio (SAR) ≥500) or pure silicon (SAR→∞) seeds are introduced into the gel system to ensure that the seeds are embedded in the product skeleton in a complete form; in the post-processing stage, since the removal rate of silicon atoms in the molecular sieve skeleton is much greater than that of aluminum atoms, the high silicon seed area is preferentially etched by an alkaline solution to directionally generate mesopores while retaining the matrix microporous structure, so as to solve the problems existing in the above-mentioned prior art and realize the precise customization of the multi-level pore structure.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is to provide a method for preparing a hierarchical pore zeolite, comprising the following steps:

[0007] Mixing silicon source, aluminum source, template, alkali source and water uniformly to obtain zeolite initial gel;

[0008] adding a seed solution to the initial zeolite gel, subjecting it to aging treatment and hydrothermal crystallization treatment to obtain a hierarchical pore zeolite precursor;

[0009] The hierarchical pore zeolite precursor is calcined and etched with alkaline solution to obtain the hierarchical pore zeolite;

[0010] The seed crystal solution is a seed crystal solution with a silicon-to-aluminum ratio of ≥500 or a pure silicon seed crystal solution.

[0011] Furthermore, the molar ratio of the silicon source, aluminum source, template, alkali source and water is 1:(0.01-0.02):(0.05-0.3):(0.1-0.3):(20-100).

[0012] Furthermore, the amount of the seed solution added is 10-50% of the mass of the initial zeolite gel.

[0013] Optionally, the amount of the seed solution added to the initial zeolite gel is 30-50% of the mass of the initial zeolite gel.

[0014] Furthermore, the aging treatment time is 2 hours.

[0015] Furthermore, the temperature of the hydrothermal crystallization treatment is 140-200° C., and the time is 12-72 hours.

[0016] Optionally, the temperature of the hydrothermal crystallization treatment is 140-170°C.

[0017] Furthermore, the calcination temperature is 550° C. and the calcination time is 4-10 hours.

[0018] The purpose of calcination in the present invention is to remove the template.

[0019] Furthermore, the temperature of the alkaline solution etching is 80-100° C., and the time is 1-5 hours.

[0020] Optionally, the alkali solution etching time is 1-3 hours.

[0021] Furthermore, the silicon source is at least one of silica sol, white carbon black, silica gel and water glass.

[0022] Furthermore, the aluminum source is at least one of sodium metaaluminate, pseudo-boehmite, aluminum isopropoxide and aluminum sulfate.

[0023] Furthermore, the alkali source is at least one of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide and ammonia water.

[0024] Furthermore, the template agent includes n-butylamine, tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

[0025] Optionally, the template includes tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

[0026] Furthermore, the pure silicon seed solution is a ZSM-5 zeolite seed solution.

[0027] Furthermore, the seed solution with a silicon-aluminum ratio of ≥500 is a Beta zeolite solution.

[0028] When the seed crystal solution is a ZSM-5 zeolite seed crystal solution, the template agent is n-butylamine, tetraethylammonium hydroxide or tetrapropylammonium hydroxide, preferably tetrapropylammonium hydroxide.

[0029] When the seed crystal solution is a Beta zeolite seed crystal solution, the template is tetraethylammonium hydroxide.

[0030] Optionally, the step of preparing the ZSM-5 zeolite seed solution includes: mixing tetraethyl orthosilicate (TEOS) and tetrapropylammonium hydroxide (TPAOH), and crystallizing at 50-170° C. for 24 hours to obtain the ZSM-5 zeolite seed solution.

[0031] Preferably, the molar ratio of ethyl orthosilicate to tetrapropylammonium hydroxide is 1:(0.2-0.3).

[0032] Preferably, the crystallization temperature is 70-100°C.

[0033] Optionally, the preparation step of the Beta zeolite seed solution includes: heat treating the Beta zeolite seeds in a 1-4 mol / L acid solution at a temperature of 50-150° C. for 6-12 h, drying and then dissolving in a 0.1-0.3 mol / L sodium hydroxide solution to obtain the Beta zeolite seed solution.

[0034] Preferably, the acid solution is a sulfuric acid solution or a hydrochloric acid solution.

[0035] Preferably, the drying temperature is 120°C.

[0036] Preferably, the liquid-to-solid ratio of the Beta zeolite seed crystals to the sodium hydroxide solution is 10-30.

[0037] Furthermore, the alkali solution used for the alkali etching is one of sodium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium hydroxide, and the concentration is 1-5 mol / L.

[0038] Optionally, the alkali solution used for the alkali etching is sodium hydroxide with a concentration of 1-2 mol / L.

[0039] This invention synthesizes hierarchically porous zeolites through seed-induced synthesis. The seeds engage in two competing behaviors within the zeolite synthesis system: "structure-directed" (dissolution and recombination) and complete preservation. When the seed addition exceeds 30%, the system's supersaturation decreases significantly, resulting in the seeds being dominant as dopants. This results in the final product essentially becoming a "seed-new phase complex." Furthermore, during alkali treatment, the desiliconization rate of the zeolite framework is exponentially positively correlated with the silicon-to-aluminum ratio (SAR), with higher SARs resulting in faster desiliconization rates.

[0040] The second technical solution of the present invention is to provide a hierarchical pore zeolite, which is prepared by the above-mentioned preparation method.

[0041] The third technical solution of the present invention is to provide an application of the above-mentioned hierarchical pore zeolite as a catalyst in the field of catalytic diesel hydrocracking to prepare monocyclic aromatic hydrocarbons and xylene isomerization.

[0042] The present invention discloses the following technical effects:

[0043] The multi-level pore zeolite prepared by the present invention breaks through the inherent bottleneck of mesopore size and external specific surface area. Through the "high silicon / pure silicon seed-selective etching" synergistic strategy, mesopores (10-30nm) are generated in the zeolite skeleton, the mesopore volume is increased to 0.25-0.35cm3 / g, and the external specific surface area reaches 180-220m 2 / g, which is 100%-150% higher than the traditional seed method (mesopore volume <0.15cm3 / g, external specific surface area <120m2 / g), significantly enhancing the mass transfer efficiency of the reactants.

[0044] The hierarchical pore zeolite prepared by the present invention accurately retains the microporous structure and acid center, and the high-silicon seed crystals (SAR≥500) are preferentially dissolved in the alkali treatment, thereby extending the catalytic life by 2-3 times.

[0045] The method for preparing hierarchical pore zeolite of the present invention gets rid of the dependence on high-cost hard templates and toxic soft templates, is a green and low-cost process, and provides a universal solution for the industrial application of hierarchical pore zeolite. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0047] Figure 1 This is the XRD pattern of the product in Example 1.

[0048] Figure 2 This is the TEM image of the product in Example 1.

[0049] Figure 3 This is the adsorption-desorption isotherm of the product of Example 1.

[0050] Figure 4 This is the XRD pattern of the product in Example 2.

[0051] Figure 5 The XRD patterns of the products of Comparative Examples 1-3 are shown. DETAILED DESCRIPTION

[0052] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0053] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0054] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0055] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0056] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0057] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0058] Unless otherwise specified, the raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0059] Among them, the commercially available Beta zeolite seeds were provided by Shandong Qilu Huaxin High-Tech Co., Ltd.

[0060] Unless otherwise specified, the normal temperature and room temperature involved in the specific embodiments of the present invention refer to 20-30°C.

[0061] Example 1

[0062] The preparation steps of hierarchical ZSM-5 zeolite include:

[0063] S1, tetraethyl orthosilicate (TEOS) and tetrapropylammonium hydroxide (TPAOH) were mixed in a molar ratio of 1:0.2, and reacted at 80° C. for 24 hours to obtain a ZSM-5 seed solution (SAR was ∞, pure silicon seed);

[0064] S2, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 60):0.2:0.3:50 to obtain a zeolite initial gel;

[0065] S3, adding a ZSM-5 seed solution of 40% of the mass of the initial zeolite gel to the initial zeolite gel, aging at room temperature for 2 hours, transferring to 170°C for hydrothermal crystallization for 18 hours, and centrifuging, washing, and drying (100°C, 12 hours) the product to obtain a seeded ZSM-5 zeolite;

[0066] S4. The seeded ZSM-5 zeolite was calcined at 550° C. for 6 h, immersed in a 2 mol / L NaOH solution, treated at 80° C. for 2 h, washed and dried to obtain a hierarchical ZSM-5 zeolite.

[0067] Example 2

[0068] The preparation steps of hierarchical pore Beta zeolite include:

[0069] S1. Commercially available Beta zeolite seed crystals were immersed in 3 mol / L hydrochloric acid, treated at 120°C for 6 hours, dried, and calcined at 600°C for 3 hours. The calcined product was dissolved in 0.2 mol / L NaOH solution to prepare a Beta seed crystal suspension (SAR = 600, high silicon seed crystals);

[0070] Among them, the liquid-to-solid ratio of commercially available Beta zeolite and NaOH solution is 20;

[0071] S2, mixing silica sol, sodium metaaluminate, tetraethylammonium hydroxide (TEAOH), NaOH and H2O in a molar ratio of 1:(1 / 60):0.15:0.25:40 to obtain a zeolite initial gel;

[0072] S3, adding a Beta seed suspension of 50% of the mass of the initial zeolite gel to the initial zeolite gel, aging at 40°C for 2 hours, transferring to 140°C for hydrothermal crystallization for 24 hours, and centrifuging, washing, and drying (100°C, 12 hours) the product to obtain a Beta precursor containing seed crystals;

[0073] S4. The seed-containing Beta precursor was calcined at 550° C. for 6 h, immersed in a 1.5 mol / L NaOH solution, treated at 60° C. for 3 h, washed and dried to obtain a hierarchical pore Beta zeolite.

[0074] Example 3

[0075] The preparation steps of hierarchical ZSM-5 zeolite include:

[0076] S1. Tetraethyl orthosilicate (TEOS) and tetrapropylammonium hydroxide (TPAOH) were mixed in a molar ratio of 1:0.3 and reacted at 80° C. for 24 hours to obtain a ZSM-5 seed solution (SAR=∞, pure silicon seed);

[0077] S2, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 100):0.2:0.3:50 to obtain a zeolite initial gel;

[0078] S3, adding a ZSM-5 seed solution of 50% of the mass of the initial zeolite gel to the initial zeolite gel, aging at room temperature for 2 hours, transferring to 170°C for hydrothermal crystallization for 18 hours, and centrifuging, washing, and drying (100°C, 12 hours) the product to obtain a seeded ZSM-5 zeolite;

[0079] S4. The seeded ZSM-5 zeolite was calcined at 550° C. for 6 h, immersed in a 2 mol / L NaOH solution, treated at 80° C. for 2 h, washed and dried to obtain a hierarchical ZSM-5 zeolite.

[0080] Example 4

[0081] The preparation steps of hierarchical ZSM-5 zeolite include:

[0082] S1, tetraethyl orthosilicate (TEOS) and tetrapropylammonium hydroxide (TPAOH) were mixed in a molar ratio of 1:0.2, and reacted at 80° C. for 24 hours to obtain a ZSM-5 seed solution (SAR=∞, pure silicon seed);

[0083] S2, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 80):0.2:0.3:50 to obtain a zeolite initial gel;

[0084] S3, adding a ZSM-5 seed solution of 30% of the mass of the initial zeolite gel to the initial zeolite gel, aging at room temperature for 2 hours, transferring to 170°C for hydrothermal crystallization for 18 hours, and centrifuging, washing, and drying (100°C, 12 hours) the product to obtain a seeded ZSM-5 zeolite;

[0085] S4. The seeded ZSM-5 zeolite was calcined at 550° C. for 6 h, immersed in a 2 mol / L NaOH solution, treated at 80° C. for 2 h, washed and dried to obtain a hierarchical ZSM-5 zeolite.

[0086] Example 5

[0087] The preparation steps of hierarchical ZSM-5 zeolite include:

[0088] S1, tetraethyl orthosilicate (TEOS) and tetrapropylammonium hydroxide (TPAOH) were mixed in a molar ratio of 1:0.3, and reacted at 80° C. for 24 hours to obtain a ZSM-5 seed solution (SAR was ∞, pure silicon seed);

[0089] S2, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 70):0.2:0.3:50 to obtain a zeolite initial gel;

[0090] S3, adding a ZSM-5 seed solution of 40% of the mass of the initial zeolite gel to the initial zeolite gel, aging at room temperature for 2 hours, transferring to 170°C for hydrothermal crystallization for 18 hours, and centrifuging, washing, and drying (100°C, 12 hours) the product to obtain a seeded ZSM-5 zeolite;

[0091] S4. The seeded ZSM-5 zeolite was calcined at 550° C. for 6 h, immersed in a 2 mol / L NaOH solution, treated at 80° C. for 2 h, washed and dried to obtain a hierarchical ZSM-5 zeolite.

[0092] Comparative Example 1

[0093] The steps for preparing ZSM-5 zeolite by the traditional seed method (low silicon seed) include:

[0094] S1, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 60):0.2:0.3:50 to obtain a zeolite initial gel;

[0095] S2. Adding 5% of the mass of the initial zeolite gel to the ZSM-5 seed crystals with a silicon-aluminum ratio (SAR) of 50, the ZSM-5 seed crystals were aged at room temperature for 2 hours, and then transferred to 170° C. for hydrothermal crystallization for 18 hours. The product was centrifuged, washed, and dried (100° C. for 12 hours) to obtain the seeded ZSM-5 zeolite.

[0096] S3. calcining the ZSM-5 zeolite containing the seed crystals at 550° C. for 4 h to obtain ZSM-5 zeolite.

[0097] Comparative Example 2

[0098] The steps of preparing ZSM-5 zeolite by hard template method include:

[0099] S1, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 60):0.2:0.3:50 to obtain a zeolite initial gel;

[0100] S2, adding 20% ​​of the mass of the initial zeolite gel to the nanocarbon sphere template into the initial zeolite gel, aging at room temperature for 2 hours, transferring to 170 ° C for hydrothermal crystallization for 18 hours, and centrifuging, washing, and drying (100 ° C, 12 hours) to obtain a precursor product;

[0101] S3. The precursor product was calcined at 600° C. for 6 h, immersed in a 2 mol / L NaOH solution, treated at 80° C. for 2 h, washed and dried to obtain ZSM-5 zeolite.

[0102] Comparative Example 3

[0103] The steps of preparing ZSM-5 zeolite by post-treatment method include:

[0104] S1, mixing silica sol, sodium metaaluminate, tetrapropylammonium hydroxide (TPAOH), NaOH and H2O in a molar ratio of 1:(1 / 60):0.2:0.3:50 to obtain a zeolite initial gel;

[0105] S3, after aging the initial zeolite gel at room temperature for 2 hours, transferring it to 170°C for hydrothermal crystallization for 18 hours, and the product was centrifuged, washed, and dried (100°C, 12 hours) to obtain ZSM-5 zeolite;

[0106] S4. Immerse the ZSM-5 zeolite in a 2 mol / L NaOH solution, treat at 80° C. for 2 hours, wash and dry to obtain the ZSM-5 zeolite.

[0107] Test example

[0108] Figure 1This is the XRD pattern of the product of Example 1. As can be seen from the figure, the crystal form of the hierarchical pore ZSM-5 zeolite prepared by the present invention does not change, and the crystallinity is good.

[0109] Figure 2 This is a TEM image of the product of Example 1. As can be seen from the image, there are a large number of cavities between the secondary particles of the hierarchical porous ZSM-5 zeolite prepared by the present invention, which provide channels for the diffusion of reactants and products.

[0110] Figure 3 This is the adsorption-desorption isotherm for the product of Example 1. As can be seen from the figure, the hierarchical ZSM-5 zeolite prepared using the present invention quickly reaches equilibrium at low relative pressures, demonstrating a typical microporous structure. As the relative pressure rises above 0.4, the adsorption capacity increases rapidly, indicating the presence of a large number of mesopores, which is consistent with the results of the TEM image.

[0111] Figure 4 This is the XRD pattern of the product of Example 2. As can be seen from the figure, the crystal form of the hierarchical pore Beta zeolite prepared by the present invention does not change, and the crystallinity is good.

[0112] Figure 5 The XRD patterns of the products of Comparative Examples 1 to 3 are shown in Table 1. As can be seen from the diagram, the products of Comparative Examples 1 to 3 are all pure ZSM-5 zeolites.

[0113] The specific surface area and pore volume data of the products obtained in Examples 1-2 and Comparative Examples 1-3 were tested, and the results are shown in Table 1. The method is as follows:

[0114] A 0.2 g zeolite sample was pretreated at 350°C for 2 h under vacuum pressure and then adsorbed with N2 at -196°C. The specific surface area was calculated using the BET equation, and the micropore specific surface area and micropore volume were calculated using the t-Plot method.

[0115] Table 1 Specific surface area and pore volume data of hierarchical pore zeolite

[0116]

[0117]

[0118] It can be seen from the data in Table 1 that the external specific surface area and mesopore volume of the hierarchical pore zeolite sample prepared by the present invention are significantly improved. This result fully demonstrates that the present method can effectively prepare a hierarchical pore zeolite with both microporous and mesoporous structures and the coexistence of the two.

[0119] Catalyst performance test example 1

[0120] Catalytic performance testing of xylene isomerization catalysts prepared from hierarchically porous ZSM-5 zeolite. To verify the catalytic performance of xylene isomerization prepared from the samples of Example 1 and Comparative Examples 1-3 (catalyst evaluation methods were based on XFLi et al. Chinese Journal of Chemical Engineering 24 (2016) 1577-1583), the performance of the samples was tested using 15.0% by mass ethylbenzene and 85.0% by mass m-xylene as the reaction feedstocks. The results are shown in Table 2.

[0121] Catalytic performance test conditions: reaction temperature 360 ​​° C; reaction pressure 0.5 MPa; space velocity = 4.5 h -1 The hydrogen-to-hydrocarbon molar ratio was 2.0. After 3 hours of reaction, the liquid reaction product was analyzed by gas chromatography. The catalytic performance parameter includes isomerization activity. SPX = wPX / wΣX × 100%, where wPX and wΣX represent the mass fractions of paraxylene and total xylene in the liquid product, respectively.

[0122] Table 2 Activity of xylene isomerization catalysts prepared from Example 1 and Comparative Example samples

[0123] sample Isomerization activity (%) C8 aromatics loss (%) Example 1 23.8 1.3 Comparative Example 1 22.1 2.6 Comparative Example 2 21.3 3.1 Comparative Example 3 22.4 2.9

[0124] Catalyst performance test example 2

[0125] The catalytic performance of the catalyst prepared from hierarchical ZSM-5 zeolite for the hydrocracking of tetralin (a model compound for catalytic diesel). In order to verify the catalytic performance of the samples prepared in Example 1 and Comparative Examples 1-3 (the evaluation method of the catalyst refers to the Journal of Inorganic Chemistry, 2022, 38(07):1350-1360), tetralin was used as the reaction raw material and the catalytic performance of the samples was tested. The results are shown in Table 3. The conditions for the catalytic performance test of the catalyst are as follows: reaction temperature 480°C, pressure 6MPa, and volume ratio of H2 to tetralin of 1300:1.

[0126] Table 3 Preparation of tetralin hydrocracking catalysts from Example 1 and Comparative Example samples

[0127] sample Conversion rate (%) Lifespan (h) Example 1 80.6 60.4 Comparative Example 1 61.4 22.1 Comparative Example 2 50.3 17.3 Comparative Example 3 49.7 15.9

[0128] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0129] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing hierarchical pore zeolite, characterized in that the steps include: Mixing silicon source, aluminum source, template, alkali source and water uniformly to obtain zeolite initial gel; adding a seed solution to the initial zeolite gel, subjecting it to aging treatment and hydrothermal crystallization treatment to obtain a hierarchical pore zeolite precursor; The hierarchical pore zeolite precursor is calcined and etched with alkaline solution to obtain the hierarchical pore zeolite; The seed crystal solution is a seed crystal solution with a silicon-to-aluminum ratio of ≥500 or a pure silicon seed crystal solution.

2. The preparation method according to claim 1, wherein The molar ratio of the silicon source, aluminum source, template, alkali source and water is 1:(0.01-0.02):(0.05-0.3):(0.1-0.3):(20-100); And / or, the amount of the seed solution added is 10-50% of the mass of the initial zeolite gel.

3. The preparation method according to claim 1, wherein The aging time is 2h; And / or, the temperature of the hydrothermal crystallization treatment is 140-200° C. and the time is 12-72 hours; And / or, the calcination temperature is 550° C. and the calcination time is 4-10 h; And / or, the temperature of the alkaline solution etching is 80-100° C., and the time is 1-5 hours.

4. The preparation method according to claim 1, wherein The silicon source is at least one of silica sol, white carbon black, silica gel and water glass; And / or, the aluminum source is at least one of sodium metaaluminate, pseudo-boehmite, aluminum isopropoxide and aluminum sulfate; And / or, the alkaline source is at least one of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide and ammonia water; And / or, the template includes n-butylamine, tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

5. The preparation method according to claim 1, wherein The seed crystal solution with a silicon-to-aluminum ratio of ≥500 is a Beta zeolite seed crystal solution; and / or the pure silicon seed crystal solution is a ZSM-5 zeolite seed crystal solution.

6. The preparation method according to claim 5, wherein The preparation steps of the ZSM-5 zeolite seed solution include: mixing ethyl orthosilicate and tetrapropylammonium hydroxide, and crystallizing at 50-170° C. for 24 hours to obtain the ZSM-5 zeolite seed solution.

7. The preparation method according to claim 6, wherein The molar ratio of the ethyl orthosilicate to tetrapropylammonium hydroxide is 1:(0.2-0.3).

8. The preparation method according to claim 5, wherein The preparation step of the Beta zeolite seed solution comprises: heat-treating Beta zeolite seeds in a 1-4 mol / L acid solution at a temperature of 50-150° C. for 6-12 hours, drying, and then dissolving in a 0.1-0.3 mol / L sodium hydroxide solution to obtain the Beta zeolite seed solution; Wherein, the acid solution is a sulfuric acid solution or a hydrochloric acid solution; and / or the drying temperature is 120° C.; and / or the liquid-to-solid ratio of the Beta zeolite seed crystals to the sodium hydroxide solution is 10-30.

9. A hierarchical pore zeolite, characterized in that: The hierarchical pore zeolite is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the hierarchically porous zeolite according to claim 9 as a catalyst in the field of catalytic diesel hydrocracking to produce monocyclic aromatic hydrocarbons and xylene isomerization.

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