A multi-level pore all-silicon molecular sieve Silicalite-2 and its preparation method and application

Abstract

The present invention belongs to the field of molecular sieve synthesis technology, and in particular to a multi-level porous all-silicon molecular sieve Silicalite-2 and a preparation method thereof. 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 a straight channel connected by micropores-mesopores-micropores. 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.

Description

Technical Field

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

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

[0003] Methods for forming hierarchical pores in molecular sieves are primarily categorized into the following: soft template method, hard template method, and post-processing method. During the hard template synthesis process, phase separation is very likely to occur due to differences in physical and chemical properties between the hard template used and surface functional groups, resulting in low yields. Post-processing methods, on the other hand, employ acid / base treatment to create mesopores by desiliconization or dealumination, leading to a loss of framework. The resulting hierarchical pore molecular sieves are susceptible to structural collapse during the reaction. Therefore, developing a simple, low-cost soft template preparation method to synthesize more efficient Silicalite-2 porous molecular sieves is key to solving this problem.

[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, ZSM-5 seed crystals, and the above solution under closed conditions to obtain a gel. After hydrothermal crystallization, the gel is dried and calcined 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 reproducibility, making it unfavorable for industrial production. CN106276957A discloses an ordered macroporous-mesoporous multi-level opal structure. The synthesis method of multi-level pore pure silicon molecular sieve Silicalite-1, which uses styrene microspheres, silica and sucrose as raw materials to synthesize a multi-level porous carbon material as a hard template, and mixes a silicon source, an organic template, water, anhydrous ethanol and a carbon material to prepare a dry glue. After hydrothermal crystallization, the soft and hard templates are removed to obtain the target multi-level pore pure silicon molecular sieve. The carbon material template used in this method has poor affinity with the silicon oxide material and cannot effectively play a pore-forming effect. The connectivity of the pores is poor, and the improvement of the diffusion performance is limited; CN112479222A discloses a method for preparing a multi-level pore pure silicon zeolite molecular sieve. A saccharide is contacted with porous silica gel to obtain a silica gel containing a saccharide; after grinding and mixing the template with the above-mentioned silica gel, a multi-level pore pure silicon zeolite molecular sieve can be obtained by crystallization and calcination. The preparation method of the molecular sieve is simple, but the regular uniformity of the pores formed by the saccharide 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-forming effect, poor pore connectivity and regular uniformity, and low molecular sieve crystallinity, which limits the improvement of the diffusion performance of the molecular sieve. In addition, due to the lack of research on Silicalite-2 multi-level pore all-silicon molecular sieves in the prior art, a multi-level pore all-silicon molecular sieve Silicalite-2 and its preparation method and application are proposed. The present invention combines a specific microporous template agent with a mesoporous template agent to prepare a Silicalite-2 molecular sieve containing multi-level pores. The Silicalite-2 molecular sieve is free of 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] In a first aspect, the present invention provides a multi-level porous all-silicon molecular sieve Silicalite-2, which has micropores with a pore size of 0.4-0.5 nm and mesopores with a pore size of 2.0-5.0 nm, 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 of ​​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) crystallizing the mixed solution, 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 calculated based on the molar number of SiO2 contained therein.

[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 wt %.

[0015] Preferably, the silicon source is ethyl 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 include: 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 provides 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 porous all-silicon molecular sieve Silicalite-2 of the present invention adopts a template to direct the synthesis of regular microporous channels. The XRD spectrum shows that there is only a Silicalite-2 molecular sieve crystal phase without other impurities. Through measurement and calculation, it is known that the molecular sieve obtained by the optimal synthesis process has a high degree of crystallinity. At the same time, when preparing the multi-level porous all-silicon molecular sieve Silicalite-2, a double-template hydrothermal synthesis method is adopted in which a specific microporous template and a mesoporous template are added simultaneously. This 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 following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0027] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[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 of ​​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; the micro- and mesoporous templates induce the silicon source to undergo regular self-polymerization, hydrolysis, and produce organic silicon oligomers, and then the templates are removed by drying and calcining to obtain the target porous molecular sieve; 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 weight of the two is 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 amount 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 calculated based on the molar number of SiO2 it contains, and the molar number of the microporous template and the mesoporous template is calculated based on the molar number of the silicon source itself. In a preferred embodiment, in step (1), the molar ratio of the amount of the microporous template, the mesoporous template, 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), during the specific implementation, 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 0.5-10 hours. In a preferred embodiment, the mixing conditions include: temperature of 45-55°C, time of 3-5 hours.

[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 produce ethanol during the reaction, and the produced 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 autogenous 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 process, 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 for the crystallization treatment include: a temperature of 100-200° C. and a time of 12-90 hours. In a preferred embodiment, the conditions for 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 crystallized product 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 hours. Specifically, the calcination is carried out 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) crystallizing the mixed solution, 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) crystallizing the mixed solution, 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] Wherein, the microporous template is tetrabutylammonium hydroxide, and 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 calculated based on the molar number of SiO2 it contains.

[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) crystallizing the mixed solution, 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, and 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 calculated based on the molar number of SiO2 it contains; 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) crystallizing the mixed solution, 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, and 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 calculated based on the molar number of SiO2 it contains; the tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25 weight%; the silicon source is ethyl 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) crystallizing the mixed solution, 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] Wherein, 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 calculated based on the molar number of SiO2 it contains; the tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25 weight %; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the conditions for the crystallization treatment 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) crystallizing the mixed solution, 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] Wherein, 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 calculated based on the molar number of SiO2 it contains; the tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25 weight %; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the crystallization treatment conditions include: temperature of 100-200°C and time of 12-90h; in step (1), the mixing conditions include: temperature of 45-80°C and 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) crystallizing the mixed solution, 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] Wherein, 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 calculated based on the molar number of SiO2 it contains; the tetrabutylammonium hydroxide is used in the form of an aqueous solution, and the tetrabutylammonium hydroxide is used in the form of an aqueous solution. The concentration of the aqueous ammonium chloride solution is ≥25% by weight; the silicon source is tetraethyl orthosilicate and / or silica sol; in step (2), the conditions for the crystallization treatment include: a temperature of 100-200°C and a time of 12-90 hours; in step (1), the mixing conditions include: a temperature of 45-80°C and a time of 0.5-10 hours; the method further includes drying the separated solid phase product before calcination, and the drying conditions include: a temperature of 100-120°C and a time of 5-10 hours.

[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) crystallizing the mixed solution, 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] Wherein, 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 calculated based on the molar number of SiO2 it contains; the tetrabutylammonium hydroxide is used in the form of an aqueous solution, the concentration of the tetrabutylammonium hydroxide aqueous solution is ≥25% by weight; the silicon source is ethyl orthosilicate and / or silica sol; in step (2), the conditions for the crystallization treatment include: a temperature of 100-200°C and a time of 12-90h; in step (1), the conditions for the mixing include: a temperature of 45-80°C and a time of 0.5-10h; the method further includes drying the separated solid phase product before calcination, and the drying conditions include: a temperature of 100-120°C and a time of 5-10h; in step (2), the conditions for the calcination include: a temperature of 450-600°C and a time of 5-10h.

[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] A fourth aspect of the present invention proposes the use of the aforementioned hierarchically porous all-silicon molecular sieve, Silicalite-2, in the preparation of porous catalysts and in organic shape-selective or confined chemical reactions. In this context, "organic shape-selective reaction" refers to the molecular sieve's micropores screening the target product, improving its selectivity; "confined chemical reaction" refers to the ability of the molecular sieve's mesoporous channels to carry out chemical reactions, increasing the collision probability of reactant molecules and improving conversion.

[0081] The following examples further illustrate the multi-level porous all-silicon molecular sieve Silicalite-2 and its preparation method. The examples are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection 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] Cetyltrimethylammonium 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 (2SiO2.3H2O): Manufacturer: Rongzheng Chemical, industrial grade.

[0088] Test Case

[0089] Scanning Electron Microscope (SEM): Sample morphology was analyzed using a Hitachi S-4800 scanning electron microscope (SEM). The microscope uses scattered electron beam or secondary electron imaging principles, with sample magnification ranging from 100 to 800K and acceleration voltages ranging from 0.5 to 30kV. Sample preparation: A small amount of Silicalite-2, an all-silicon molecular sieve, was ultrasonically dispersed in an ethanol solution for 1 hour. The sample was then dripped onto a small copper sheet using a plastic dropper. The sheet was then sequentially attached to a conductive adhesive and gold-sprayed for 90 seconds before being loaded for testing.

[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 operating voltage and current were 40 kV and 200 mA, respectively. The all-silicon molecular sieve Silicalite-2 sample was ground into a fine powder before testing. The 2θ angle measurement range was 5-90°, with a test speed of 8° / min and a step size of 1 second. The test files were analyzed and processed using Jade 6.0.

[0091] Crystallinity: K = (I / S) / (2B*cosθ), where 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; and 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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0095] (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 to a pH value of 7, 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. 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 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. The mixture was 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) 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 to a pH value of 7, 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. 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 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 0.65 cm 3 / g, pore surface area of ​​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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of the tetraethyl orthosilicate) to obtain a mixed solution.

[0101] (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 to a pH value of 7, 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. 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 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 0.53 cm 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. The mixture was stirred at 60°C for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0104] (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 to a pH value of 7, 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. 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 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 0.33 cm 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 (2SiO2.3H2O) was added dropwise under magnetic stirring. The mixture was stirred at 60°C for 3 h to mix. 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 ethyl orthosilicate) to obtain a mixed solution;

[0107] (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 to a pH value of 7, 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. 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 connected by micropores-mesopores-micropores. The yield of the multi-level porous all-silicon molecular sieve Silicalite-2 is 88%, and the pore volume is 0.41 cm 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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0110] (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 100 ° C for 90 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 to a pH value of 7, 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. 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 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 0.25 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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0113] (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 200 ° C for 12 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 to a pH value of 7, 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. 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 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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) 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 to a pH value of 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. 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 connected by micropores-mesopores-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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0119] (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 to a pH value of 6.5, 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. 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 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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) 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 to a pH value of 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. 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 connected by micropores-mesopores-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] Example 11

[0124] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) 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 to a pH value of 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. 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 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 0.61 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 cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0128] (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 to a pH value of 7, and then dried at 110 ° C for 10 hours, and then calcined at 500 ° C for 7 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2. 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 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 0.44 cm 3 / g, pore surface area is 488m 2 / g, and the crystallinity is 83.7%.

[0129] Example 13

[0130] (1) 38.48 g of tetrabutylammonium hydroxide (TBAOH, 25 wt%), 13.52 g of cetyltrimethylammonium 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) to obtain a mixed solution.

[0131] (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 to a pH value of 7, and then dried at 110 ° C for 10 hours, and then calcined at 600 ° C for 5 hours to obtain a multi-level porous all-silicon molecular sieve Silicalite-2. 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 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 0.43 cm 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 cetyltrimethylammonium 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. The mixture was stirred at 60°C for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of TEOS) 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 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 to a pH value of 7, and then dried at 110°C for 10 hours, and then calcined at 550°C for 6 hours 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and maintained for 0.5 h (to remove ethanol generated during the hydrolysis of the 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 in an 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. The mixture was stirred at 60° C. for 3 h to mix. The stopper on one side of the three-necked flask was then opened and the mixture was maintained for 0.5 h (to remove ethanol generated during the hydrolysis of the tetraethyl orthosilicate) to obtain a mixed solution.

[0140] (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 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 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 high 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 have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection 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 connected by micropores, mesopores, and micropores. The pore volume of the multi-level porous all-silicon molecular sieve Silicalite-2 is 0.22-0.65 cm 3 / g, pore surface area of ​​330-570m 2 / g.

2. The multi-level porous all-silicon molecular sieve Silicalite-2 according to claim 1, 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.

3. A method for preparing the multi-level porous all-silicon molecular sieve Silicalite-2 according to claim 1 or 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) crystallizing the mixed solution, 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; 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; In step (1), the mixing conditions include: temperature of 45-80°C and time of 0.5-10h; In step (2), the crystallization treatment conditions include: temperature of 100-200°C and time of 12-90h; In step (2), the calcination conditions include: temperature of 450-600°C and time of 5-10 hours.

4. The method according to claim 3, 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.

5. The method according to claim 3 or 4, characterized in that The silicon source is ethyl orthosilicate and / or silica sol.

6. The method according to claim 3 or 4, characterized in that The method further comprises drying the separated solid phase product before calcination.

7. The method according to claim 6, characterized in that The drying conditions include: a temperature of 100-120° C. and a time of 5-10 hours.

8. The multi-level porous all-silicon molecular sieve Silicalite-2 prepared by the method according to any one of claims 3 to 7.

9. Use of the hierarchically porous all-silicon molecular sieve Silicalite-2 according to claim 1, 2 or 8 in the preparation of porous catalysts and organic shape-selective or confined chemical reactions.

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