Hierarchical pore all-silicon molecular sieve Silicalite-2 as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of molecular sieve synthesis, and particularly relates to a hierarchical pore all-silicon molecular sieve Silicalite-2 and a preparation method thereof. The hierarchical pore all-silicon molecular sieve Silicalite-2 is provided with micropores with the pore diameter of 0.4-0.5 nm and mesopores with the pore diameter of 2.0-5.0 nm, and is also provided with straight channels which are connected with one another by micropores, mesopores and micropores. The Silicalite-2 molecular sieve is free of mixed crystals and has high crystallinity, and the preparation method is simple, easy to operate, short in period, suitable for industrial production and high in yield.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve synthesis, and in particular to a multi-level pore all-silicon molecular sieve Silicalite-2 and a preparation method and application thereof. Background Art

[0002] Silicalite-2 zeolite is a molecular sieve with a MEL-type framework structure and is an all-silicon form of ZSM-11. It has relatively high thermal and chemical stability. Its special ten-membered ring straight-through pore structure and strong hydrophobic and lipophilic properties make it an inert carrier for shape-selective catalysts and is widely used in isomerization separation, permeation and organic matter removal systems. However, its micropore size limits the transport of reactant and product macromolecules in the molecular sieve, thereby limiting its application in catalysis. Therefore, constructing multi-level pores in the molecular sieve to improve the flow and diffusion of the molecular sieve has become an urgent requirement for the application of this molecular sieve. Moreover, there is no literature report on the preparation of Silicalite-2 multi-level pore all-silicon molecular sieve.

[0003] The methods for forming multi-level pores of molecular sieves are mainly divided into the following categories: soft template method, hard template method, post-processing method, etc. In the synthesis process of the hard template method, due to the differences in physical and chemical properties such as the hard template used and the surface functional groups, phase separation is very likely to occur, resulting in low yields. The post-processing method uses acid / base treatment to produce mesopores by causing skeleton loss through desiliconization or dealumination. The resulting multi-level porous molecular sieve is prone to structural collapse during the reaction. Therefore, the key to solving the problem is to develop a simple and low-cost soft template preparation method to synthesize more efficient Silicalite-2 porous molecular sieves.

[0004] CN105645429A discloses a method for synthesizing Silicalite-2 all-silicon molecular sieve, which comprises mixing a template with an alkali source, adjusting the pH value of the solution, and then stirring a silicon source, a ZSM-5 seed crystal and the above solution under closed conditions to obtain a gel, and after hydrothermal crystallization, drying and roasting to obtain the Silicalite-2 all-silicon molecular sieve. This method uses a seed crystal induction method to synthesize the target molecular sieve, which has high requirements for the pre-preparation seed crystals and poor repeatability, and is not conducive to industrial production; CN106276957A discloses an ordered macroporous-mesoporous multi-level opal structure The method for synthesizing multi-level porous pure silicon molecular sieve Silicalite-1 is a method for synthesizing a multi-level porous carbon material synthesized by using styrene microspheres, silicon dioxide and sucrose as raw materials as a hard template agent, and a silicon source, an organic template agent, water, anhydrous ethanol and a carbon material are mixed and stirred to obtain a dry glue, and the soft and hard template agents are removed after hydrothermal crystallization to obtain the target multi-level porous pure silicon molecular sieve. The carbon material template agent used in this method has poor affinity with the silicon oxide material and cannot effectively play a pore-forming effect, and the connectivity of the pores is poor, and the improvement of diffusion performance is limited; CN112479222A discloses a method for preparing a multi-level porous pure silicon zeolite molecular sieve. The carbohydrate substance is contacted with porous silica gel to obtain silica gel containing the carbohydrate substance; after the template agent is ground and mixed with the above-mentioned silica gel, a multi-level porous pure silicon zeolite molecular sieve can be obtained by crystallization and roasting. The preparation method of the molecular sieve is simple, but the regular uniformity of the pores formed by the carbohydrate substance is poor, and the crystallinity of the molecular sieve is often low, which has limited improvement on the molecular diffusivity. Summary of the invention

[0005] The purpose of the present invention is to address the shortcomings of the prior art in preparing multi-porous all-silicon molecular sieves, such as poor pore-making effect, poor pore connectivity and regular uniformity, and low molecular sieve crystallinity, which limits the improvement of the diffusion performance of the molecular sieve, and the lack of research on Silicalite-2 multi-level pore all-silicon molecular sieves in the prior art, thereby proposing a multi-level pore all-silicon molecular sieve Silicalite-2 and its preparation method and application. The present invention combines a specific microporous template with a mesoporous template to prepare a Silicalite-2 molecular sieve containing multi-level pores. The Silicalite-2 molecular sieve has no impurities and has a high degree of crystallinity. At the same time, the preparation method is simple and easy to operate, has a short cycle, is suitable for industrial production, and has a high yield.

[0006] The first aspect of the present invention provides a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5nm and mesopores with a pore size of 2.0-5.0nm, and has straight channels connecting micropores, mesopores and micropores.

[0007] Preferably, the pore volume of the multi-level pore all-silicon molecular sieve Silicalite-2 is 0.22-0.65 cm 3 / g, pore surface area is 330-570m 2 / g.

[0008] Preferably, the multi-level porous all-silicon molecular sieve Silicalite-2 is prepared by crystallizing raw materials containing a microporous template, a mesoporous template and a silicon source, wherein the microporous template is tetrabutylammonium hydroxide, and the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

[0009] The second aspect of the present invention provides a method for preparing a multi-level porous all-silicon molecular sieve Silicalite-2, the method comprising the following steps:

[0010] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0011] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0012] Wherein, the microporous template agent is tetrabutylammonium hydroxide, and the mesoporous template agent is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

[0013] Preferably, the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO 2 The number of moles.

[0014] Preferably, the tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight.

[0015] Preferably, the silicon source is tetraethyl orthosilicate and / or silica sol.

[0016] Preferably, in step (2), the conditions of the crystallization treatment include: temperature of 100-200° C. and time of 12-90 h.

[0017] Preferably, in step (1), the mixing conditions include: temperature of 45-80° C. and time of 0.5-10 h.

[0018] Preferably, the method further comprises drying the separated solid phase product before calcination; more preferably, the drying conditions comprise: a temperature of 100-120° C. and a drying time of 5-10 h.

[0019] Preferably, in step (2), the calcination conditions include: temperature of 450-600° C. and time of 5-10 h.

[0020] The third aspect of the present invention provides a multi-level porous all-silicon molecular sieve Silicalite-2 prepared by the above-mentioned method.

[0021] The fourth aspect of the present invention proposes an application of the multi-level porous all-silicon molecular sieve Silicalite-2 described above in the preparation of porous catalysts and organic shape-selective or confined chemical reactions.

[0022] The multi-level pore all-silicon molecular sieve Silicalite-2 of the present invention adopts a template agent to directional synthesize regular microporous channels, and an XRD spectrum shows that there is only a Silicalite-2 molecular sieve crystal phase without other impurities, and through measurement and calculation, it can be known that the molecular sieve obtained by the optimal synthesis process has a higher degree of crystallinity. At the same time, when preparing the multi-level pore all-silicon molecular sieve Silicalite-2, a double template agent is added simultaneously to perform a hydrothermal synthesis method for preparation, and the method is simple to operate, has a short cycle, and has a high yield, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image of the multi-level porous all-silicon molecular sieve Silicalite-2 prepared in Example 1 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the multi-level porous all-silicon molecular sieve Silicalite-2 prepared in Comparative Example 1 of the present invention;

[0025] Figure 3 This is the XRD diffraction pattern of the multi-level porous all-silicon molecular sieve Silicalite-2 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] The first aspect of the present invention proposes a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5nm and mesopores with a pore size of 2.0-5.0nm, and has straight channels connecting micropores, mesopores and micropores, which is conducive to the diffusion and transfer of molecules.

[0029] In the multi-level pore all-silicon molecular sieve Silicalite-2 of the present invention, in a specific embodiment, the pore volume of the multi-level pore all-silicon molecular sieve Silicalite-2 is 0.22-0.65cm 3 / g, pore surface area is 330-570m 2 / g.

[0030] In the multi-level porous all-silicon molecular sieve Silicalite-2 of the present invention, in a specific embodiment, the multi-level porous all-silicon molecular sieve Silicalite-2 is prepared by crystallizing a raw material containing a microporous template, a mesoporous template and a silicon source, wherein the microporous template is tetrabutylammonium hydroxide, and the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

[0031] The second aspect of the present invention provides a method for preparing a multi-level porous all-silicon molecular sieve Silicalite-2, the method comprising the following steps:

[0032] (1) mixing and stirring a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0033] (2) The mixed solution is crystallized, and the treated product is centrifuged, washed, dried, and calcined to obtain a multi-level porous all-silicon molecular sieve Silicalite-2 single crystal; micro- and mesoporous templates induce the silicon source to undergo regular self-polymerization and hydrolysis to produce organic silicon oligomers, and then the template is removed by drying and calcining to obtain the target porous molecular sieve; wherein tetrabutylammonium hydroxide is selected as the microporous template to form a cross straight channel with a pore size of ~0.45nm, and hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride are used as the mesoporous template. Since the molecular weights of the two are moderate, a pore size structure of 2-5nm can be obtained after calcination. If the pore size is too small, it is not conducive to molecular diffusion. If the pore size is too large, the porous molecular sieve structure is unstable and easy to collapse.

[0034] In the method of the present invention, in a specific embodiment, the tetrabutylammonium hydroxide is used in the form of an aqueous solution. In a preferred embodiment, the microporous template agent is a tetrabutylammonium hydroxide aqueous solution with a concentration of ≥25% by weight.

[0035] In the method of the present invention, in a specific embodiment, the silicon source is tetraethyl orthosilicate and / or silica sol.

[0036] In the method of the present invention, in a specific embodiment, in step (1), the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, for example, it can be 0.05:0.05:10:1, 0.1:0.1:64:1, 0.27:0.27:32:1 or 0.5:0.5:100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The molar number of the microporous template agent and the mesoporous template agent is calculated by their own molar number. In a preferred embodiment, in step (1), the molar ratio of the microporous template agent, the mesoporous template agent, water and the silicon source is 0.2-0.3:0.2-0.3:25-50:1.

[0037] In the method of the present invention, in step (1), in the specific implementation process, the microporous template agent and the mesoporous template agent are mixed with deionized water, and then the silicon source is added dropwise under magnetic stirring to mix and stir.

[0038] In the method of the present invention, in step (1), in a specific embodiment, the mixing conditions include: temperature of 45-80°C, time of 0.5-10h. In a preferred embodiment, the mixing conditions include: temperature of 45-55°C, time of 3-5h.

[0039] In the method of the present invention, in step (1), during the specific operation, when the silicon source used is tetraethyl orthosilicate, tetraethyl orthosilicate will be hydrolyzed to generate ethanol during the reaction, and the generated ethanol needs to be removed from the mixed solution. Specifically, the ethanol removal method can be a conventional choice in the art.

[0040] In the method of the present invention, in order to ensure that the total volume of the solution does not change much before and after the hydrolysis of the silicon source, sufficient self-generated pressure can be provided for the sealed crystallization process. In the specific operation process, before the crystallization treatment, it is necessary to add water to the mixed solution obtained in step (1) to reach 4 / 5 of the volume of the crystallization kettle.

[0041] In the method of the present invention, in step (2), during the specific operation, the mixed solution obtained in step (1) is placed in a crystallization kettle with a polytetrafluoroethylene lining for crystallization treatment.

[0042] In the method of the present invention, in step (2), in a specific embodiment, the conditions of the crystallization treatment include: a temperature of 100-200° C. and a time of 12-90 hours. In a preferred embodiment, the conditions of the crystallization treatment include: a temperature of 160-180° C. and a time of 60-80 hours.

[0043] In the method of the present invention, in step (2), during the specific operation, before centrifugation, the product after the crystallization treatment is quenched to room temperature using an ice water bath.

[0044] In the method of the present invention, in step (2), in a specific embodiment, the pH value of the product after washing is 6.5-7.5, for example, it can be 6.5, 7 or 7.5.

[0045] In the method of the present invention, in step (2), in a specific embodiment, the drying conditions include: a temperature of 100-120° C. and a time of 5-10 h.

[0046] In the method of the present invention, in step (2), in a specific embodiment, the calcination conditions include: a temperature of 450-600° C. and a time of 5-10 h. Specifically, the calcination is performed in an air atmosphere.

[0047] According to a first embodiment of the method of the present invention, the method comprises the following steps:

[0048] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0049] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0050] Wherein, the microporous template agent is tetrabutylammonium hydroxide, and the mesoporous template agent is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

[0051] According to a second embodiment of the method of the present invention, the method comprises the following steps:

[0052] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0053] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0054] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The number of moles.

[0055] According to a third embodiment of the method of the present invention, the method comprises the following steps:

[0056] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0057] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0058] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight.

[0059] According to a fourth embodiment of the method of the present invention, the method comprises the following steps:

[0060] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0061] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0062] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight; the silicon source is tetraethyl orthosilicate and / or silica sol.

[0063] According to a fifth embodiment of the method of the present invention, the method comprises the following steps:

[0064] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0065] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0066] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the crystallization treatment conditions include: a temperature of 100-200°C and a time of 12-90h.

[0067] According to a sixth embodiment of the method of the present invention, the method comprises the following steps:

[0068] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0069] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0070] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the crystallization treatment conditions include: a temperature of 100-200°C and a time of 12-90h; in step (1), the mixing conditions include: a temperature of 45-80°C and a time of 0.5-10h.

[0071] According to a seventh embodiment of the method of the present invention, the method comprises the following steps:

[0072] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0073] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0074] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2The method comprises the following steps: wherein the tetrabutylammonium hydroxide is used in the form of an aqueous solution, the concentration of the tetrabutylammonium hydroxide aqueous solution being ≥25 wt %; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the crystallization treatment conditions include: a temperature of 100-200° C. and a time of 12-90 h; in step (1), the mixing conditions include: a temperature of 45-80° C. and a time of 0.5-10 h; the method further comprises drying the separated solid phase product before calcination, the drying conditions including: a temperature of 100-120° C. and a time of 5-10 h.

[0075] According to an eighth embodiment of the method of the present invention, the method comprises the following steps:

[0076] (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution;

[0077] (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2;

[0078] The microporous template is tetrabutylammonium hydroxide, the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride; the molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is the SiO contained in it. 2 The method comprises the following steps: wherein the tetrabutylammonium hydroxide is used in the form of an aqueous solution, the concentration of the tetrabutylammonium hydroxide aqueous solution being ≥25 wt %; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the crystallization treatment conditions include: a temperature of 100-200° C. and a time of 12-90 h; in step (1), the mixing conditions include: a temperature of 45-80° C. and a time of 0.5-10 h; the method further comprises drying the separated solid phase product before calcination, the drying conditions include: a temperature of 100-120° C. and a time of 5-10 h; in step (2), the calcination conditions include: a temperature of 450-600° C. and a time of 5-10 h.

[0079] The third aspect of the present invention provides a multi-level porous all-silicon molecular sieve Silicalite-2 prepared by the above-mentioned method.

[0080] The fourth aspect of the present invention proposes an application of the multi-level porous all-silicon molecular sieve Silicalite-2 described above in the preparation of porous catalysts and organic shape-selective or confined chemical reactions. In this article, "organic shape-selective reaction" refers to the molecular screening of target products by the micropores of the molecular sieve to improve the selectivity of the target products; "confined chemical reaction" refers to the chemical reaction that can be carried out in the suitable mesoporous channels of the molecular sieve, which increases the collision probability of the reactant molecules and improves the conversion rate.

[0081] The following examples further illustrate the multi-level porous all-silicon molecular sieve Silicalite-2 and its preparation method of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0082] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0083] Tetrabutylammonium hydroxide (TBAOH): Manufacturer: Wokai Reagent, Brand: XW20524951;

[0084] Hexadecyltrimethylammonium bromide (CTAB): Manufacturer: Shanghai Test Reagent, Brand: 30037416;

[0085] Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC): Manufacturer: Wokai Reagent, Brand: XW276685263;

[0086] Tetraethyl orthosilicate (TEOS): Manufacturer: Shanghai Test Reagent, Brand: 80124118;

[0087] Silica sol (2SiO 2 .3H 2 O): Manufacturer: Rongzheng Chemical, industrial grade.

[0088] Test Case

[0089] Scanning electron microscope (SEM): The morphology of the sample was analyzed by the S-4800 scanning electron microscope produced by Hitachi, Japan. The principle is the scattered electron beam or secondary electron imaging principle. The magnification of the sample is 100-800K, and the acceleration voltage is from 0.5 to 30KV. Sample preparation process: Take a very small amount of all-silicon molecular sieve Silicalite-2 and ultrasonically disperse it in ethanol solution for 1h, drop it on the surface of a small copper sheet with a plastic dropper, stick it to the conductive glue in order, spray gold for 90S, and carry out sample loading test.

[0090] XRD diffraction pattern: The phase of the molecular sieve was determined by Rigaku D / max-2500 X-ray diffractometer produced by Japan Rigaku Corporation. CuKα was used as the radiation source. The working voltage and current are 40KV and 200mA respectively. The all-silicon molecular sieve Silicalite-2 sample should be ground into fine powder before testing. The 2θ angle test range is 5-90°, the test speed is 8° / min, and the step length is 1s. The test file is analyzed and processed by Jade 6.0.

[0091] Crystallinity: K = (I / S) / (2B*cosθ), K is the crystallinity, I is the peak area of ​​the XRD diffraction peak; S is the sample weight; B is the diffraction peak width; θ is the diffraction peak wavelength.

[0092] Yield: Y = (S 实际重量 / S 理论重量 )*100%.

[0093] Example 1

[0094] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0095] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 92%, and the pore volume is 0.60 cm 3 / g, pore surface area is 558m 2 / g, and the crystallinity is 86.6%.

[0096] Example 2

[0097] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 28.34 g of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC, 65 wt%) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0098] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 94%, and the pore volume is 0.65cm 3 / g, pore surface area is 570m 2 / g, and the crystallinity is 86.2%.

[0099] Example 3

[0100] (1) 35.81 g of tetrabutylammonium hydroxide (TBAOH, 50 wt%), 25.15 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0101] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 90%, and the pore volume is 0.53cm 3 / g, pore surface area is 551m 2 / g, and the crystallinity is 85.2%.

[0102] Example 4

[0103] (1) 2.39 g of tetrabutylammonium hydroxide (TBAOH, 75 wt%), 2.51 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0104] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 95%, and the pore volume is 0.33cm 3 / g, pore surface area is 347m 2 / g, and the crystallinity is 77.5%.

[0105] Example 5

[0106] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of silica sol (2SiO 2 .3H 2 O), stirring at 60° C. for 3 h to mix, then opening the stopper on one side of the three-necked flask and maintaining for 0.5 h (to remove ethanol generated during the hydrolysis of ethyl orthosilicate), to obtain a mixed solution;

[0107] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 88%, and the pore volume is 0.41cm 3 / g, pore surface area is 416m 2 / g, and the crystallinity is 84.7%.

[0108] Example 6

[0109] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0110] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 100° C. for 90 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110° C. for 10 hours, and then calcine it at 550° C. for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 92%, and the pore volume is 0.25 cm 3 / g, pore surface area is 385m 2 / g, and the crystallinity is 78.1%.

[0111] Example 7

[0112] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0113] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 200°C for 12 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 90%, and the pore volume is 0.58 cm 3 / g, pore surface area is 536m 2 / g, and the crystallinity is 87.3%.

[0114] Example 8

[0115] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0116] (2) Deionized water was added to the mixed solution of step (1) to make up to 80 mL, and then placed in a 100 mL crystallization kettle and treated at 170°C for 72 hours. After the treatment, the treated product was quenched to room temperature in an ice water bath, and then centrifuged. The separated solid phase product was washed with deionized water until the pH value was 7.5, and then dried at 110°C for 10 hours, and then calcined at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 93%, and the pore volume is 0.62 cm 3 / g, pore surface area is 566m 2 / g, and the crystallinity is 86.3%.

[0117] Example 9

[0118] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0119] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 6.5, then dry it at 110°C for 10 hours, and then calcine it at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 90%, and the pore volume is 0.58 cm 3 / g, pore surface area is 522m 2 / g, and the crystallinity is 86.1%.

[0120] Example 10

[0121] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0122] (2) Deionized water was added to the mixed solution of step (1) to make up to 80 mL, and then placed in a 100 mL crystallization kettle and treated at 170°C for 72 hours. After the treatment, the treated product was quenched to room temperature in an ice water bath, and then centrifuged. The separated solid phase product was washed with deionized water until the pH value was 7, and then dried at 100°C for 6 hours, and then calcined at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 93%, and the pore volume is 0.55 cm 3 / g, pore surface area is 539m 2 / g, and the crystallinity is 85.8%.

[0123] Embodiment 11

[0124] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0125] (2) Deionized water was added to the mixed solution of step (1) to make up to 80 mL, and then placed in a 100 mL crystallization kettle and treated at 170°C for 72 hours. After the treatment, the treated product was quenched to room temperature in an ice water bath, and then centrifuged. The separated solid phase product was washed with deionized water until the pH value was 7, and then dried at 120°C for 5 hours, and then calcined at 550°C for 6 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 92%, and the pore volume is 0.61 cm 3 / g, pore surface area is 556m 2 / g, and the crystallinity is 85.9%.

[0126] Example 12

[0127] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0128] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 500°C for 7 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 94%, and the pore volume is 0.44cm 3 / g, pore surface area is 488m 2 / g, and the crystallinity is 83.7%.

[0129] Embodiment 13

[0130] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0131] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170°C for 72 hours. After the treatment, use an ice water bath to quench the treated product to room temperature, then centrifuge it, wash the separated solid phase product with deionized water until the pH value is 7, then dry it at 110°C for 10 hours, and then calcine it at 600°C for 5 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connected by micropores, mesopores and micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 94%, and the pore volume is 0.43cm 3 / g, pore surface area is 461m 2 / g, and the crystallinity is 82.1%.

[0132] Comparative Example 1

[0133] (1) 4.79 g of n-octylamine, 13.52 g of hexadecyltrimethylammonium bromide (CTAB) and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0134] (2) Deionized water was added to the mixed solution of step (1) to make up to 80 mL, and then placed in a 100 mL crystallization kettle and treated at 170° C. for 72 h. After the treatment, the treated product was quenched to room temperature in an ice water bath, and then centrifuged. The separated solid phase product was washed with deionized water until the pH value was 7, and then dried at 110° C. for 10 h, and then calcined at 550° C. for 6 h to obtain a multi-level pore all-silicon molecular sieve Silicalite-2. The pore volume of the multi-level pore all-silicon molecular sieve Silicalite-2 is 0.11 cm 3 / g, pore surface area is 279m 2 / g.

[0135] Comparative Example 2

[0136] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of polystyrene and 40 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0137] (2) Deionized water was added to the mixed solution of step (1) to make up to 80 mL, and then placed in a 100 mL crystallization kettle and treated at 170° C. for 72 h. After the treatment, the treated product was quenched to room temperature by ice water bath, and then centrifuged. The separated solid phase product was washed with deionized water to a pH value of 7, and then dried at 110° C. for 24 h, and then calcined at 550° C. for 6 h to obtain a molecular sieve with a mesoporous pore size of 10 nm-20 nm and an easily collapsed structure, and a pore volume of 0.15 cm 3 / g, pore surface area is 223m 2 / g.

[0138] Comparative Example 3

[0139] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%) and 53.52 g of water were placed in a three-necked flask, and then 14.32 g of tetraethyl orthosilicate (TEOS) was added dropwise under magnetic stirring, and stirred at 60° C. for 3 h to mix, and then the stopper on one side of the three-necked flask was opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of tetraethyl orthosilicate) to obtain a mixed solution;

[0140] (2) Add deionized water to the mixed solution of step (1) to make up to 80 mL, then place it in a 100 mL crystallization kettle and treat it at 170° C. for 72 h. After the treatment, quench the treated product to room temperature in an ice water bath and then centrifuge it. Wash the separated solid phase product with deionized water to a pH of 7, then dry it at 110° C. for 24 h, and then calcine it at 550° C. for 6 h to obtain a fully microporous Silicalite-2 molecular sieve.

[0141] From the experimental results of Examples 1-13 and Figure 1-3 It can be seen that the multi-level porous all-silicon molecular sieve Silicalite-2 prepared by the present invention has no impurity crystals and has a high degree of crystallinity. At the same time, the preparation method is simple and easy to operate, has a short cycle, is suitable for industrial production, and has a high yield.

[0142] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A multi-level pore all-silicon molecular sieve Silicalite-2, characterized in that: The multi-level porous all-silicon molecular sieve Silicalite-2 has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, and has straight channels connecting micropores, mesopores and micropores.

2. The molecular sieve Silicalite-2 according to claim 1, characterized in that The pore volume of the multi-level pore all-silicon molecular sieve Silicalite-2 is 0.22-0.65cm 3 / g, pore surface area is 330-570m 2 / g.

3. The multi-level porous all-silicon molecular sieve Silicalite-2 according to claim 1 or 2, characterized in that: The multi-level porous all-silicon molecular sieve Silicalite-2 is prepared by crystallizing raw materials containing a microporous template, a mesoporous template and a silicon source, wherein the microporous template is tetrabutylammonium hydroxide, and the mesoporous template is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

4. A method for preparing a multi-level porous all-silicon molecular sieve Silicalite-2, characterized in that: The method comprises the following steps: (1) mixing a microporous template, a mesoporous template, a silicon source and water to obtain a mixed solution; (2) subjecting the mixed solution to crystallization treatment, then separating the treated product into solid and liquid, and calcining the separated solid phase product to obtain a multi-level porous all-silicon molecular sieve Silicalite-2; Wherein, the microporous template agent is tetrabutylammonium hydroxide, and the mesoporous template agent is hexadecyltrimethylammonium bromide and / or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

5. The method according to claim 4, characterized in that The molar ratio of the microporous template, the mesoporous template, water and the silicon source is 0.05-0.5:0.05-0.5:10-100:1, wherein the molar number of the silicon source is calculated based on the molar number of SiO2 contained therein.

6. The method according to claim 4 or 5, characterized in that: The tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight.

7. The method according to any one of claims 4 to 6, characterized in that: The silicon source is tetraethyl orthosilicate and / or silica sol.

8. The method according to any one of claims 4 to 7, characterized in that: In step (2), the conditions of the crystallization treatment include: temperature of 100-200° C. and time of 12-90 h.

9. The method according to any one of claims 4 to 8, characterized in that: In step (1), the mixing conditions include: temperature of 45-80°C and time of 0.5-10h.

10. The method according to any one of claims 4 to 9, characterized in that: The method also includes drying the separated solid phase product before calcination; Preferably, the drying conditions include: a temperature of 100-120° C. and a time of 5-10 h.

11. The method according to any one of claims 4 to 10, characterized in that: In step (2), the calcination conditions include: temperature of 450-600° C. and time of 5-10 h.

12. The multi-level porous all-silicon molecular sieve Silicalite-2 prepared by the method of any one of claims 4 to 11.

13. Use of the multi-level porous all-silicon molecular sieve Silicalite-2 as claimed in any one of claims 1 to 3 and 12 in the preparation of porous catalysts and organic shape-selective or confined chemical reactions.

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