Core-shell molecular sieves, methods of making and using the same, and processes for the co-production of ethylbenzene and para-diethylbenzene

Abstract

The application provides a kind of MFI structure molecular sieve MCM-41 core-shell molecular sieve and its preparation method and application and ZSM-5@MCM-41 core-shell molecular sieve and its preparation method and application, the core-shell coverage of the molecular sieve is 95-100%, XRD has characteristic peak at 1°-3°, the ratio of outer surface B acid amount and total B acid amount is 0.01~0.2.The application provides a kind of method for synthesizing ethylbenzene and p-diethylbenzene by ethylene and benzene alkylation, which comprises: contacting ethylene and benzene in the presence of ZSM-5@MCM-41 core-shell molecular sieve described in the application.The core-shell molecular sieve of the application has excellent para-selective ability and abundant mesoporous structure, and has strong anti-carbon deposition capacity, and can be used as active component and carrier of catalyst in various fields.

Description

Technical Field

[0001] This invention relates to the core-shell molecular sieve of MFI structured molecular sieve @MCM-41, its preparation method and application, as well as the preparation method and application of ZSM-5@MCM-41 core-shell molecular sieve, and a method for synthesizing ethylbenzene and co-producing p-diethylbenzene by alkylation of ethylene and benzene. Background Technology

[0002] p-Diethylbenzene is a high-value-added organic chemical raw material. It is used as a desorbent in the production of p-xylene and is widely used in the production of ion exchange resins, coatings, and crosslinking agents. Mobil's ZSM-5 molecular sieve, with its unique ten-membered ring channel structure, is considered one of the best catalysts for the production of p-diethylbenzene.

[0003] ZSM-5 molecular sieves have a unique pore structure, with pore sizes similar to the kinetic diameter of p-diethylbenzene. However, when using ZSM-5 molecular sieves for catalytic reactions, the para-selectivity of diethylbenzene is only about 30%, approaching thermodynamic equilibrium. The main reason is that p-diethylbenzene undergoes secondary isomerization at the non-shape-selective acidic sites on the outer surface of the ZSM-5 molecular sieve, resulting in two impurity byproducts: ortho-diethylbenzene and meta-diethylbenzene, ultimately leading to a decrease in para-selectivity. Therefore, removing the acidic sites on the outer surface is an essential modification method for obtaining ZSM-5 molecular sieve catalysts with high para-shape selectivity.

[0004] The unique core-shell structure combines the advantages of both the molecular sieve core and shell, greatly optimizing its performance and enabling the catalyst to achieve multifunctional catalytic effects that cannot be achieved by a single material, thus meeting more application requirements. The M41S series is a novel all-silica mesoporous material with ordered mesoporous walls, first discovered and successfully synthesized by Mobil in 1992, with MCM-41 being one of its most representative materials. It exhibits a one-dimensional ordered hexagonal mesoporous channel structure, good thermal and hydrothermal stability, a large specific surface area, and adjustable pore size (1.6–10 nm), and its synthesis process is simple. However, all-silica MCM-41 lacks acidity and ion exchange capacity, making it difficult to apply in many acid-catalyzed reactions. Therefore, combining MCM-41 mesoporous material with ZSM-5 molecular sieves imparts catalytic activity.

[0005] CN201410131825.7 discloses a method for synthesizing a ZSM-5@MCM-41 core-shell composite molecular sieve. ZSM-5 is first treated with an alkali to enrich its hydroxyl groups, and then the target catalyst is obtained through hydrothermal crystallization. This method provides a pre-reaction zone for the processing of heavy oil macromolecules and slows down the deactivation rate of the microporous active zone. However, the MCM-41 shell does not completely cover the acidic sites on the outer surface of ZSM-5, resulting in poor orthotropic shape selectivity.

[0006] Jindan Na et al. (Advanced Materials Research, 2012, 528: 267-271) synthesized ZSM-5 / MCM-41 molecular sieves via a hydrothermal method using hexadecyltrimethylammonium bromide as a template agent and ZSM-5 molecular sieve as a silicon source. They found that the concentration of sodium hydroxide and the crystallization time significantly affected the thickness of the MCM-41 shell and the crystallinity of the composite molecular sieve. This method significantly increased the reactivity of the catalytic cracking of n-dodecane, but it lacked para-selectivity. When applied to the alkylation of ethylene and benzene to synthesize ethylbenzene and co-produce p-diethylbenzene, it exhibited low para-selectivity and a short lifespan.

[0007] Chinese patent application 200410019886.0 discloses a mesoporous MCM-41 molecular sieve with ZSM-5 zeolite primary structural units. The method uses a direct method to prepare colloidal ZSM-5, then pre-treats it, and finally self-assembles it with hexadecyltrimethylammonium bromide to obtain the target catalyst. It has high hydrothermal stability and good etherification performance, but when used in alkylation reactions, its reactivity is low and its para-position shape selectivity is poor.

[0008] In the method of co-producing ethylbenzene and p-diethylbenzene by alkylation of benzene and ethylene, the p-diethylbenzene product will come into contact with a large number of acidic active sites on the outer surface of the molecular sieve. Due to the loss of the pore channel constraint, an isomerization reaction will occur, generating three isomers, ortho, meta, and para, which are close to thermodynamic equilibrium, thus affecting the para-selectivity of the reaction. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a method for preparing and applying a core-shell molecular sieve, @MCM-41, with novel structural features.

[0010] This invention proposes a novel method for preparing core-shell molecular sieves. The method involves hydrothermally treating the molecular sieve matrix. In the presence of high-temperature steam, some of the framework aluminum detaches, reducing overall acidity and creating defect sites. These defect sites facilitate the coating of mesoporous materials onto the outer surface of the MFI-structured molecular sieve, reducing acidic sites on the outer surface. More importantly, the hydrothermally treated molecular sieve is functionalized using two surfactants: polydiallyldimethylammonium chloride (PDDA) and dodecyl polyoxyethylene methyl ammonium chloride. This gives the outer surface of the molecular sieve a positive charge, which strongly interacts with the negatively charged mesoporous silica material in the alkaline solution. The two charges attract each other, preventing the silica from assembling into a core independently, resulting in a more uniform and orderly coating on the outer surface of the molecular sieve. Finally, calcination is performed to coat the outer surface of the molecular sieve with MCM-41 shell layers, allowing it to grow more densely on the outer surface, resulting in a core-shell molecular sieve with excellent dispersibility and other superior properties.

[0011] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides a core-shell molecular sieve of MFI structure molecular sieve @MCM-41, wherein the core-shell coverage of the molecular sieve is 95-100%, the XRD shows a characteristic peak at 1°-3°, and the ratio of the amount of Brønsted acid on the outer surface to the total amount of Brønsted acid is 0.01-0.2.

[0012] According to a second aspect of the present invention, the present invention provides a method for preparing the core-shell molecular sieve of the present invention, the method comprising:

[0013] a) The ammonium-type MFI structured molecular sieve was subjected to hydrothermal treatment to obtain the first solid;

[0014] b) The first solid is contacted with a mixed solution containing polydiallyl dimethyl ammonium chloride (PDDA) and dodecyl polyoxyethylene methyl ammonium chloride, separated, and dried to obtain the second solid;

[0015] c) Mix the second solid with a mixed solution of the raw materials for synthesizing the MCM-41, including water, organic solvent, template agent and alkali source, until homogeneous;

[0016] d) The raw materials from step III) are mixed evenly with a silicon source and hydrolyzed, then separated, washed, dried and calcined to obtain a solid; optionally, steps a)-d) are repeated multiple times, preferably 1-4 times.

[0017] According to a third aspect of the present invention, a method for preparing ZSM-5@MCM-41 core-shell molecular sieves using the preparation method described herein is provided, the method comprising:

[0018] I) The ZSM-5 parent material is ammonium exchanged and dried to obtain NH4-ZSM-5 ammonium molecular sieve. The ammonium exchange process includes: mixing the ZSM-5 parent material with an ammonium salt solution for ammonium ion exchange, slurrying according to the mass ratio of ZSM-5 parent material: ammonium salt: water = 1:(0.5-2):(5-20), stirring and exchanging at 25-95℃ for 0.5-3h, and repeating the ammonium exchange process 1-4 times.

[0019] II) The above ammonium-exchanged sample is subjected to hydrothermal treatment, the hydrothermal treatment process includes: placing the sample in a hydrothermal furnace at 400-850℃ and calcining it in a 20-100% volume water vapor atmosphere for 1-20 hours.

[0020] III) The hydrothermally treated sample was added to a mixed solution containing polydiallyldimethylammonium chloride and dodecyl polyoxyethylene methylammonium chloride, stirred at room temperature for 30-120 min, centrifuged, washed, and dried. The mass ratio of ZSM-5, polydiallyldimethylammonium chloride, dodecyl polyoxyethylene methylammonium chloride and water was 1:(0.4-3):(0.05-1):(50-500) on a dry basis.

[0021] IV) Add the solid from step III) to a mixed solution of ammonia, hexadecyltrimethylammonium bromide, ethanol and water, and ultrasonically disperse for 30-120 min; wherein, the mass ratio of ZSM-5, ammonia, hexadecyltrimethylammonium bromide, ethanol and water on a dry basis is 1:(2-5):(0.5-2):(50-150):(100-500);

[0022] V) Under stirring conditions, add tetraethyl orthosilicate to the mixed solution in step IV), then stir at room temperature for 4-8 hours, centrifuge, wash, dry, and calcine. The mass ratio of ZSM-5 to tetraethyl orthosilicate on a dry basis is 1:(0.1-2).

[0023] According to a fourth aspect of the present invention, the present invention provides the application of the core-shell molecular sieve described herein as a catalyst support and / or active component.

[0024] According to a fifth aspect of the present invention, the present invention provides the application of the ZSM-5@MCM-41 core-shell molecular sieve of the present invention in alkylation.

[0025] According to a sixth aspect of the present invention, the present invention provides a method for synthesizing ethylbenzene and co-producing p-diethylbenzene by alkylation of ethylene and benzene, the method comprising: contacting ethylene and benzene in the presence of the ZSM-5@MCM-41 core-shell molecular sieve described in the present invention.

[0026] The core-shell molecular sieve of the present invention has excellent para-shape selectivity and rich mesoporous structure, and strong resistance to carbon deposition. It can be used as an active component and support for catalysts in various fields.

[0027] The ZSM-5@MCM-41 core-shell molecular sieve of the present invention is used in alkylation reactions, such as the synthesis of ethylbenzene from ethylene and benzene, and the co-production of p-diethylbenzene, at a reaction temperature of 340–440 °C, a reaction pressure of 0.5–2 MPa, a benzene to ethylene molar ratio of 1–18, and a mass hourly space velocity (MHV) of 0.2–4 h⁻¹ based on ethylene. -1Under these conditions, the single-pass conversion rate of ethylene can reach 70-100%, and the para-selectivity of diethylbenzene can reach 70-99%. However, the ZSM-5@MCM-41 composite molecular sieve mentioned above and reported in the literature does not have an orderly and dense coating of the acidic sites on the outer surface of ZSM-5 by the shell MCM-41, leaving some acidic sites exposed. This causes the diethylbenzene product to undergo secondary isomerization at the acidic sites on the outer surface of the ZSM-5 molecular sieve, resulting in poor para-selectivity of the reaction. Attached Figure Description

[0028] Figure 1 This is the XRD pattern of catalyst sample Cata-1 from Example 1;

[0029] Figure 2 This is a transmission electron microscope (TEM) image of catalyst sample Cata-1 from Example 1;

[0030] Figure 3 This is a scanning electron microscope image of catalyst sample Cata-1 from Example 1. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] In this invention, the core-shell molecular sieve of MFI structured molecular sieve @MCM-41 refers to a core-shell type composite molecular sieve with MFI structured molecular sieve as the core and MCM-41 as the shell.

[0033] This invention provides a core-shell molecular sieve of MFI structure @MCM-41, which has a core-shell coverage of 95-100%, a characteristic peak in XRD at 1°-3°, and a ratio of Brønsted acid content on the outer surface to total Brønsted acid content of 0.01-0.2.

[0034] In this invention, the core-shell coverage ratio is obtained by scanning electron microscopy.

[0035] The ratio of the amount of Brønsted acid on the outer surface to the total amount of Brønsted acid was obtained by using 2,6-di-tert-butylpyridine infrared spectroscopy and pyridine infrared spectroscopy.

[0036] According to a preferred embodiment of the present invention, the ratio of the amount of Brønsted acid on the outer surface to the total amount of Brønsted acid is 0.01 to 0.09.

[0037] According to a preferred embodiment of the present invention, the content of MFI structured molecular sieve is 20-95% by weight and the content of MCM-41 is 5-80% based on the total weight of the core-shell molecular sieve. In the present invention, the weight content is preferably based on the amount of feed.

[0038] According to a preferred embodiment of the present invention, the shell thickness of the core-shell molecular sieve is 10 nm-150 nm, preferably 50-140 nm. The shell thickness is obtained by transmission electron microscopy (TEM) images.

[0039] According to a preferred embodiment of the present invention, the MFI structured molecular sieve is one or more of ZSM-5, TSZ, SEB-08, NU-4, NU-5 and TZ-1.

[0040] According to a preferred embodiment of the present invention, the silicon-aluminum molar ratio (SiO2 / Al2O3) of the MFI structure molecular sieve is 100–300.

[0041] According to a preferred embodiment of the present invention, the grain diameter of the MFI structured molecular sieve is 100–400 nm. The grain diameter is obtained by scanning electron microscopy (SEM) images.

[0042] According to a preferred embodiment of the present invention, the core-shell molecular sieve is ZSM-5@MCM-41.

[0043] This invention does not impose special requirements on the preparation method of core-shell molecular sieves. Products possessing the aforementioned characteristics of this invention can achieve the objectives of this invention. Specifically, this invention provides a method for preparing the core-shell molecular sieve described herein, comprising:

[0044] a) The ammonium-type MFI structured molecular sieve was subjected to hydrothermal treatment to obtain the first solid;

[0045] b) The first solid is contacted with a mixed solution containing polydiallyl dimethyl ammonium chloride (PDDA) and dodecyl polyoxyethylene methyl ammonium chloride, separated, and dried to obtain the second solid;

[0046] c) Mix the second solid with a mixed solution of the raw materials for synthesizing the MCM-41, including water, organic solvent, template agent and alkali source, until homogeneous;

[0047] d) The raw materials from step III) are mixed evenly with a silicon source and hydrolyzed, then separated, washed, dried and calcined to obtain a solid; optionally, steps a)-d) are repeated multiple times, preferably 1-4 times. This invention proposes a novel method for preparing core-shell molecular sieves. The method involves hydrothermally treating the molecular sieve matrix. In the presence of high-temperature steam, some of the framework aluminum detaches, reducing overall acidity and creating defect sites. These defect sites facilitate the coating of mesoporous materials onto the outer surface of the MFI-structured molecular sieve, reducing acidic sites on the outer surface. More importantly, the hydrothermally treated molecular sieve is functionalized using two surfactants: polydiallyldimethylammonium chloride (PDDA) and dodecyl polyoxyethylene methyl ammonium chloride. This gives the outer surface of the molecular sieve a positive charge, which strongly interacts with the negatively charged mesoporous silica material in the alkaline solution. The two charges attract each other, preventing the silica from assembling into a core independently, resulting in a more uniform and orderly coating on the outer surface of the molecular sieve. Finally, calcination is performed to coat the mesoporous silica shell layer by layer, allowing it to grow more densely on the outer surface of the molecular sieve, resulting in a core-shell molecular sieve with excellent properties, including high dispersibility.

[0048] In this invention, the range of selectable amounts of each substance is relatively wide. According to a preferred embodiment of this invention, in step b), the mass ratio of MFI structure molecular sieve, polydiallyl dimethyl ammonium chloride, dodecyl polyoxyethylene methyl ammonium chloride and water is 1:(0.4-3):(0.05-1):(50-500), preferably 1:(0.5-2):(0.1-0.5):(80-200).

[0049] In this invention, the ratio of the molecular sieve (dry basis), alkali source, template agent, organic solvent and water can be selected from a wide range. According to a preferred embodiment of the present invention, in step c), the mass ratio of molecular sieve (dry basis), alkali source, template agent, organic solvent and water is 1:(2~5):(0.5~2):(50~150):(100~500), preferably 1:(2~5):(0.5~2):(80~150):(100~300).

[0050] According to a preferred embodiment of the present invention, preferably, in step c), the alkali source is one or more of ammonia water, an alkaline solution with alkali metal and / or alkaline earth metal as cations.

[0051] In this invention, the type of template agent can be selected according to the mesoporous material to be synthesized. According to a preferred embodiment of this invention, the template agent is selected from one or more of hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethyl-p-toluenesulfonium (CTATos), hexadecyltrimethylammonium chloride, and hexadecyltrimethylammonium hydroxide.

[0052] In this invention, the range of types of organic solvents that can be selected is relatively wide. Any organic solvent that is soluble in water can be used in this invention. According to a preferred embodiment of this invention, preferably, the organic solvent is selected from one or more of ethanol, isopropanol and methanol.

[0053] In this invention, the ratio of MFI structure molecular sieve to silicon source can be selected within a wide range. According to a preferred embodiment of this invention, preferably, in step d), the mass ratio of MFI structure molecular sieve to silicon source on a dry basis is 1:(0.1-2), more preferably 1:(0.1-1).

[0054] In this invention, the silicon source can be selected from a wide range of types, such as inorganic silicon oxide and organosilicone grease. According to a preferred embodiment of this invention, preferably, preferably, in step d), the silicon source is silicone grease, and more preferably, the silicone grease is tetraethyl orthosilicate.

[0055] In this invention, the range of selectable conditions for the hydrothermal treatment is relatively wide. According to a preferred embodiment of the invention, preferably, in step a), the hydrothermal treatment conditions include a temperature of 400-850℃, more preferably 500-700℃. Using the aforementioned preferred treatment conditions can reduce the overall acidity of the catalyst and simultaneously form defect sites. These defect sites make it easier for mesoporous materials to coat the outer surface of the MFI structured molecular sieve, reducing the acidic sites on the outer surface.

[0056] According to a preferred embodiment of the present invention, preferably, the water vapor concentration is 20-100% by volume, and the remaining gas is air.

[0057] In this invention, the hydrothermal treatment time can be selected within a wide range. According to a preferred embodiment of this invention, preferably, in step a), the hydrothermal treatment conditions include: a time of 1-20 hours, preferably 3-10 hours.

[0058] In this invention, ammonium-type MFI structured molecular sieves can all be used. According to a preferred embodiment of this invention, preferably, the silicon-aluminum molar ratio (SiO2 / Al2O3) of the ammonium-type MFI structured molecular sieve is 100-300.

[0059] According to a preferred embodiment of the present invention, preferably, the crystal diameter of the ammonium-type MFI structure molecular sieve is 100-400 nm.

[0060] According to a preferred embodiment of the present invention, the preparation method of MFI-structured ammonium-type molecular sieve includes:

[0061] The MFI structure molecular sieve parent material is ammonium exchanged and dried to obtain an ammonium-type molecular sieve. The ammonium exchange process includes: mixing the MFI structure molecular sieve parent material with an ammonium salt solution to perform ammonium ion exchange, preferably by slurrying at a mass ratio of catalyst:ammonium salt:water = 1:(0.5-2):(5-20), stirring and exchanging at 25-95℃ for 0.5-3 hours, preferably repeating the ammonium exchange process 1-4 times, followed by drying.

[0062] According to a preferred embodiment of the present invention, the ammonium salt is preferably one or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium oxalate and ammonium phosphate, and is preferably ammonium chloride.

[0063] According to a preferred embodiment of the present invention, the present invention provides a method for preparing ZSM-5@MCM-41 core-shell molecular sieves using the preparation method of the present invention, the method comprising:

[0064] I) The ZSM-5 parent material is ammonium exchanged and dried to obtain NH4-ZSM-5 ammonium molecular sieve. The ammonium exchange process includes: mixing the ZSM-5 parent material with an ammonium salt solution for ammonium ion exchange, slurrying according to the mass ratio of ZSM-5 parent material: ammonium salt: water = 1:(0.5-2):(5-20), stirring and exchanging at 25-95℃ for 0.5-3h, and repeating the ammonium exchange process 1-4 times.

[0065] II) The above ammonium-exchanged sample is subjected to hydrothermal treatment, the hydrothermal treatment process includes: placing the sample in a hydrothermal furnace at 400-850℃ and calcining it in a 20-100% volume water vapor atmosphere for 1-20 hours.

[0066] III) The hydrothermally treated sample was added to a mixed solution containing polydiallyldimethylammonium chloride and dodecyl polyoxyethylene methylammonium chloride, stirred at room temperature for 30-120 min, centrifuged, washed, and dried. The mass ratio of ZSM-5, polydiallyldimethylammonium chloride, dodecyl polyoxyethylene methylammonium chloride and water was 1:(0.4-3):(0.05-1):(50-500) on a dry basis.

[0067] IV) Add the solid from step III) to a mixed solution of ammonia, hexadecyltrimethylammonium bromide, ethanol and water, and ultrasonically disperse for 30-120 min; wherein, the mass ratio of ZSM-5, ammonia, hexadecyltrimethylammonium bromide, ethanol and water on a dry basis is 1:(2-5):(0.5-2):(50-150):(100-500);

[0068] V) Under stirring conditions, add tetraethyl orthosilicate to the mixed solution in step IV), then stir at room temperature for 4-8 hours, centrifuge, wash, dry, and calcine. The mass ratio of ZSM-5 to tetraethyl orthosilicate on a dry basis is 1:(0.1-2). This invention first uses hydrothermal treatment of the ZSM-5 molecular sieve matrix. In the presence of high-temperature steam, some of the aluminum skeleton of ZSM-5 detaches, reducing the overall acidity and forming defect sites. These defect sites make it easier for MCM-41 to coat the outer surface of ZSM-5, reducing the acidic sites on the outer surface. More importantly, two surfactants, polydiallyldimethylammonium chloride (PDDA) and dodecyl polyoxyethylenemethylammonium chloride, are used to functionalize the hydrothermally treated ZSM-5 molecular sieve, giving the outer surface of the molecular sieve a positive charge. This positive charge interacts strongly with the negatively charged MCM-41 in the alkaline solution. The two charges attract each other, preventing MCM-41 from assembling into a core on its own, and allowing it to coat the outer surface of the molecular sieve more uniformly and orderly. Finally, multiple calcinations are performed to coat the MCM-41 shell layer by layer, making it grow more densely on the outer surface of the ZSM-5 molecular sieve, resulting in a ZSM-5@MCM-41 core-shell molecular sieve with high dispersibility and excellent alignment and shape selectivity.

[0069] According to a preferred embodiment of the present invention, the present invention provides a method for preparing a ZSM-5@MCM-41 core-shell molecular sieve with high para-selectivity, the technical solution of which is as follows:

[0070] Step 1: The ZSM-5 parent material is exchanged with ammonium and dried to obtain NH4-ZSM-5 ammonium molecular sieve. The ammonium exchange process is as follows: the catalyst obtained above is mixed with an ammonium salt solution for ammonium ion exchange. The mixture is slurried at a mass ratio of catalyst:ammonium salt:water = 1:(0.5-2):(5-20) and stirred at 25-95℃ for 0.5-3 hours. This ammonium exchange process can be repeated 1-4 times. After centrifugation and washing with water, the mixture is dried at 80-150℃ for 3-9 hours.

[0071] Step 2: The ammonium-exchange sample is subjected to hydrothermal treatment to obtain a silanol-rich ZSM-5 molecular sieve; the hydrothermal treatment process includes placing the ammonium-exchange treated molecular sieve in a hydrothermal furnace at 400-850℃, calcining it in a 20-100% (volume) water vapor atmosphere for 1-20 hours, and drying it at 90-180℃ for 8-15 hours;

[0072] Step 3: Functional modification of the hydrothermally treated product. The modification process involves adding the hydrothermally treated product to a mixed solution of polydiallyldimethylammonium chloride (PDDA) and dodecyl polyoxyethylene methyl ammonium chloride, stirring at room temperature for 30-120 minutes, centrifuging, washing, and drying. The mass ratio of molecular sieve (dry basis) to PDDA, dodecyl polyoxyethylene methyl ammonium chloride, and water is 1:(0.4-3):(0.05-1):(50-500).

[0073] Step 4: Add the modified molecular sieve to a mixed solution of 28% ammonia, cetyltrimethylammonium bromide (CTAB), ethanol, and water, and ultrasonically disperse for 30–120 min to achieve a high degree of mixing. The mass ratio of the molecular sieve (dry basis) to 28% ammonia, CTAB, ethanol, and water is 1:(2–5):(0.5–2):(50–150):(100–500).

[0074] Step 5: Under stirring conditions, slowly add tetraethyl orthosilicate (TEOS) to the above mixed solution, then stir at room temperature for 4–8 hours, centrifuge, wash, dry, and calcinate. The mass ratio of molecular sieve (dry basis) to TEOS is 1:(0.1–2).

[0075] Step 6: Repeat steps 3 to 5 one to four times to obtain the final product ZSM-5@MCM-41 core-shell molecular sieve.

[0076] In the preparation of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, preferably, the silicon-aluminum molar ratio of the molecular sieve, SiO2 / Al2O3, is 100 to 300.

[0077] In the preparation of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, preferably, the crystal diameter of the molecular sieve is 100-400 nm.

[0078] In the preparation of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, when ammonium exchange is used to obtain an ammonium-type molecular sieve, the ammonium salt is one or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium oxalate and ammonium phosphate, preferably ammonium chloride.

[0079] In the preparation of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, preferably, the hydrothermal treatment process is carried out at a temperature of 500-700℃ and calcined in a 20-100% (volume) water vapor atmosphere for 3-10 hours.

[0080] In the preparation of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, preferably, the mass ratio of molecular sieve (dry basis) to PDDA, dodecyl polyoxyethylene methyl ammonium chloride and water is 1:(0.5-2):(0.1-0.5):(80-200).

[0081] In the preparation and application of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, preferably, the mass ratio of the molecular sieve (dry basis) to 28% ammonia, CTAB, ethanol and water is 1:(2-5):(0.5-2):(80-150):(100-300).

[0082] In the preparation and application of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by the present invention, preferably, the mass ratio of molecular sieve (dry basis) to TEOS is 1:(0.1~1).

[0083] In the preparation of a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve provided by this invention, the ZSM-5 molecular sieve matrix is ​​first hydrothermally treated. In the presence of high-temperature water vapor, some of the aluminum skeleton of ZSM-5 detaches, reducing the overall acidity and simultaneously forming defect sites. These defect sites make it easier for MCM-41 to coat the outer surface of ZSM-5, reducing the acidic sites on the outer surface. More importantly, two surface treatments are used: polydiallyldimethylammonium chloride (PDDA) and dodecyl polyoxyethylenemethylammonium chloride. The activator functionalizes the hydrothermally treated ZSM-5 molecular sieve, giving it a positive charge on the outer surface. This positive charge interacts strongly with the negatively charged MCM-41 in the alkaline solution. The two charges attract each other, preventing the MCM-41 from assembling into a core on its own and allowing it to be more uniformly and orderly coated on the outer surface of the molecular sieve. Finally, multiple calcinations are performed to coat the MCM-41 shell layer by layer, making it grow more densely on the outer surface of the ZSM-5 molecular sieve. This results in a ZSM-5@MCM-41 core-shell molecular sieve with high dispersibility and excellent alignment and shape selectivity.

[0084] The ZSM-5@MCM-41 core-shell molecular sieve of this invention is used in the reaction of ethylene and benzene alkylation to synthesize ethylbenzene and co-produce p-diethylbenzene, at a reaction temperature of 340–440 °C, a reaction pressure of 0.5–2 MPa, a benzene to ethylene molar ratio of 1–18, and a mass hourly space velocity (MHV) of 0.2–4 h⁻¹ based on ethylene. -1 Under these conditions, the single-pass conversion rate of ethylene can reach 70-100%, and the para-selectivity of diethylbenzene can reach 70-99%.

[0085] This invention provides the application of the core-shell molecular sieve described herein as a catalyst support and / or active component.

[0086] This invention provides the application of the ZSM-5@MCM-41 core-shell molecular sieve described herein in alkylation.

[0087] This invention provides a method for synthesizing ethylbenzene and co-producing p-diethylbenzene by alkylation of ethylene and benzene, the method comprising: contacting ethylene and benzene in the presence of the ZSM-5@MCM-41 core-shell molecular sieve described in this invention.

[0088] According to a preferred embodiment of the present invention, the contact conditions preferably include: a temperature of 340–440°C, a pressure of 0.5–2 MPa, a benzene to ethylene molar ratio of 1–18, and an ethylene mass hourly space velocity of 0.2–4 h⁻¹. -1 .

[0089] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents or instruments used in the following examples are commercially available conventional reagent products.

[0090] Probe reaction experiments of the samples were conducted in a fixed-bed microreactor. The catalyst loading was 50 mg, the feed rate of liquid 1,3,5-triisopropylbenzene was 1 μL, the pressure was normal, the vaporization temperature was 150 °C, and the reaction temperature was 350 °C. The products were analyzed by gas chromatography (Agilent GC 7890) equipped with a flame ionization detector (FID), using an HP-FFAP column, argon as the carrier gas, and a flow rate of 20 mL / min. -1 And calculate according to the following formula:

[0091] Triisopropylbenzene conversion rate = (Total product - Triisopropylbenzene) / Total amount of all product components × 100%

[0092] The conversion rate of triisopropylbenzene represents the acidity of the catalyst's outer surface; the higher the conversion rate, the higher the acidity of the outer surface.

[0093] In this invention, XRD testing was performed using a Bruker D8 Advanced X-ray diffractometer. The testing conditions included: an X-ray source of 0.15418 nm Cu Kα, a tube current of 40 mA, a tube voltage of 40 kV, a scanning range of 1–45°, a step size of 0.05°, and a scanning speed of 4° / min. -1 .

[0094] In this invention, the transmission electron microscope is a JEOL-2010F electron microscope manufactured by Nippon Electron Ltd.

[0095] In this invention, the scanning electron microscope is a Nova NanoSEM 450 field emission scanning electron microscope from FEI Corporation, USA.

[0096]

Example 1

[0097] Weigh 100g of ZSM-5 molecular sieve (laboratory synthesis, SiO2 / Al2O3 molar ratio of 200, crystal diameter of 250nm), and stir the molecular sieve (dry basis) with the ammonium chloride aqueous solution in a 90℃ water bath for 1h according to the mass ratio of molecular sieve (dry basis): ammonium chloride: water = 1:1:10. Centrifuge; repeat the exchange twice, centrifuge, wash with water, and dry at 120℃ for 5h.

[0098] Take a portion of the catalyst (e.g., 20g), place it in a hydrothermal furnace, heat it to 600℃, calcine it with 100% volume water steam for 5 hours, and dry it at 120℃ for 12 hours.

[0099] The hydrothermally treated catalyst was mixed with molecular sieve (dry basis) in a mass ratio of 1:1.5:0.2:100 to PDDA, dodecyl polyoxyethylene methyl ammonium chloride and water, and stirred for 60 min. The mixture was then centrifuged, washed, and dried.

[0100] The modified molecular sieve was added to the mixed solution in a mass ratio of molecular sieve (dry basis) to 28% ammonia, CTAB, ethanol and water of 1:3:1:100:200, and ultrasonically dispersed for 60 minutes to achieve a high degree of mixing.

[0101] Under vigorous stirring, tetraethyl orthosilicate (TEOS) was slowly added to the above mixed solution at a mass ratio of molecular sieve (dry basis) to TEOS of 1:0.4. The mixture was then stirred at room temperature for 8 hours, centrifuged, washed, dried, and calcined. The molecular sieve modification and shell coating steps were repeated three times to obtain a highly para-selective ZSM-5@MCM-41 core-shell molecular sieve, denoted as Cata-1.

[0102] In Cata-1, the content of ZSM-5 is 65% by weight and the content of MCM-41 is 35%. A transmission electron microscope (TEM) image of catalyst sample Cata-1 is shown below. Figure 2 The scanning electron microscope images are as described above. Figure 3 As described, the XRD spectrum is as follows Figure 1 The XRD pattern has a characteristic peak at 1°-3°.

[0103] Probe reaction experiments were conducted on catalyst sample Cata-1, and the data are shown in Table 1.

[0104] Catalyst sample Cata-1 was loaded into a fixed-bed reactor at a loading rate of 2 g. Benzene and ethylene were used as feedstocks for the reaction, with a benzene flow rate of 66 ml / h, an ethylene flow rate of 2400 ml / h, a benzene to ethylene molar ratio of 7, and an ethylene mass hourly space velocity (WHSV) of 1.5 h⁻¹. -1 The reaction temperature was 380℃ and the reaction pressure was 1.2 MPa. Conversion and selectivity data are shown in Table 2.

[0105]

Example 2

[0106] Weigh 100g of SEB-08 molecular sieve (Sinopec Shanghai Petrochemical Research Institute, SiO2 / Al2O3 molar ratio of 100, crystal diameter of 100nm), and stir the molecular sieve (dry basis): ammonium acetate: water in a mass ratio of 1:1:15 in an 80℃ water bath for 1 hour. Centrifuge. Repeat the exchange twice, centrifuge, wash with water, and dry at 120℃ for 5 hours.

[0107] Take a portion of the catalyst (e.g., 20g), place it in a hydrothermal furnace, heat it to 500℃, calcine it with 80% (v / v) steam for 6 hours, and dry it at 120℃ for 12 hours.

[0108] The hydrothermally treated catalyst was mixed with molecular sieve (dry basis) in a mass ratio of PDDA, dodecyl polyoxyethylene methyl ammonium chloride and water of 1:2:0.1:80, stirred for 60 min, centrifuged, washed and dried.

[0109] The modified molecular sieve was added to the mixed solution in a mass ratio of molecular sieve (dry basis) to sodium hydroxide aqueous solution (5%), CTAOH, ethanol and water of 1:2.5:1:80:150, and ultrasonically dispersed for 30 min to achieve a high degree of mixing.

[0110] Under vigorous stirring, tetraethyl orthosilicate (TEOS) was slowly added to the above mixed solution at a mass ratio of molecular sieve (dry basis) to TEOS of 1:0.2. The mixture was then stirred at room temperature for 5 hours, centrifuged, washed, dried, and calcined. The molecular sieve modification and shell coating steps were repeated three times to obtain a highly para-selective SEB-08@MCM-41 core-shell molecular sieve, denoted as Cata-2.

[0111] In Cata-2, the content of SEB-08 is 74% by weight, the content of MCM-41 is 26%, and the XRD shows characteristic peaks at 1°-3°.

[0112] Probe reaction experiments were conducted on catalyst sample Cata-2, and the data are shown in Table 1.

[0113] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0114]

Example 3

[0115] Weigh 100g of TZ-1 molecular sieve (laboratory synthesis, SiO2 / Al2O3 molar ratio of 200, crystal diameter of 400nm), and stir and exchange the molecular sieve with an aqueous solution of ammonium chloride in a 50℃ water bath for 2h according to the mass ratio of molecular sieve (dry basis): ammonium nitrate: water = 1:1:10. Centrifuge; repeat the exchange twice, centrifuge, wash with water, and dry at 120℃ for 5h.

[0116] Take a portion of the catalyst (e.g., 20g), place it in a hydrothermal furnace, heat it to 650℃, calcine it with 100% volume water vapor for 5 hours, and dry it at 120℃ for 12 hours.

[0117] The hydrothermally treated catalyst was mixed with molecular sieve (dry basis) in a mass ratio of PDDA, dodecyl polyoxyethylene methyl ammonium chloride and water of 1:0.5:0.5:200, stirred for 60 min, centrifuged, washed and dried.

[0118] The modified molecular sieve was added to the mixed solution in a mass ratio of molecular sieve (dry basis) to 28% ammonia, CTAB, methanol and water of 1:3:1:50:200, and ultrasonically dispersed for 30 minutes to achieve a high degree of mixing.

[0119] Under vigorous stirring, tetraethyl orthosilicate (TEOS) was slowly added to the above mixed solution at a mass ratio of molecular sieve (dry basis) to TEOS of 1:1. The mixture was then stirred at room temperature for 8 hours, centrifuged, washed, dried, and calcined. The molecular sieve modification and shell coating steps were repeated three times to obtain a highly para-selective TZ-1@MCM-41 core-shell molecular sieve, denoted as Cata-3.

[0120] In Cata-3, the content of TZ-1 is 48% by weight, the content of MCM-41 is 52%, and the XRD shows characteristic peaks at 1°-3°.

[0121] Probe reaction experiments were conducted on catalyst sample Cata-3, and the data are shown in Table 1.

[0122] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0123]

Example 4

[0124] Similar to Example 1, except that the hydrothermal treatment conditions included: heating to 400°C, calcining with 100% (v / v) water vapor for 2 hours, and obtaining the molecular sieve catalyst, denoted as Cata-4.

[0125] In Cata-4, XRD shows a characteristic peak at 1°–3°.

[0126] Probe reaction experiments were conducted on catalyst sample Cata-4, and the data are shown in Table 1.

[0127] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0128]

Example 5

[0129] Similar to Example 1, except that the hydrothermally treated catalyst was mixed with molecular sieve (dry basis) in a mass ratio of 1:0.5:0.7:150 to PDDA, dodecyl polyoxyethylene methyl ammonium chloride and water to obtain the molecular sieve catalyst, which is denoted as Cata-5.

[0130] In Cata-5, XRD shows a characteristic peak at 1°–3°.

[0131] Probe reaction experiments were conducted on catalyst sample Cata-4, and the data are shown in Table 1.

[0132] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0133] Comparative Example 1

[0134] The comparative molecular sieve was prepared according to the method provided in Example 1, except that the two surfactants, polydiallyl dimethyl ammonium chloride (PDDA) and dodecyl polyoxyethylene methyl ammonium chloride, were not introduced to functionalize the hydrothermally treated ZSM-5 molecular sieve. The other steps were the same, and Cata-1b was obtained.

[0135] In Cata-1b, XRD shows characteristic peaks at 1°–3°.

[0136] Probe reaction experiments were conducted on catalyst sample Cata-1b, and the data are shown in Table 1.

[0137] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0138] Comparative Example 2

[0139] ZSM-5@MCM-41 core-shell molecular sieve Cata-2b was prepared according to the method reported in CN201410131825.7.

[0140] 5g of ZSM-5 molecular sieve (SiO2 / Al2O3 = 38) was mixed with 150mL of 0.6mol / L NaOH solution and treated with alkali in an 80℃ water bath for 30min. The resulting product was filtered and washed to obtain hydroxyl-rich ZSM-5 molecular sieve. 1.65g of the alkali-treated hydroxyl-rich ZSM-5 molecular sieve was added to 30mL of deionized water, stirred for 15min, and then ultrasonically dispersed for 15min. Then, 60mL of 7.5% CTAB solution was added, and finally, 105mL of an aqueous solution containing 23.4g of Na2SiO3·9H2O and 0.45g of NaAlO2 was added. The final mixed solution had a molar ratio of SiO2:Al2O3:CTAB:H2O = 1:0.033:0.15:140, and the mass ratio of ZSM-5 to SiO2 was 0.33. After thorough stirring, the pH was adjusted to 10.5 with 1 mol / L H2SO4 solution, and then transferred to a crystallization reactor for crystallization at 110℃ for 36 h. After filtration, drying, and calcination, the ZSM-5@MCM-41 core-shell composite molecular sieve Cata-2b was obtained.

[0141] Probe reaction experiments were conducted on the catalyst sample Cata-2b, and the data are shown in Table 1.

[0142] In Cata-2b, XRD shows no characteristic peaks in the 1°–3° range.

[0143] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0144] Comparative Example 3

[0145] Similar to Example 1, except that hydrothermal treatment was not used to modify the MFI structure molecular sieve, the remaining steps were the same, and Cata-3b was obtained.

[0146] In Cata-3b, XRD shows characteristic peaks at 1°–3°.

[0147] Probe reaction experiments were conducted on catalyst sample Cata-3b, and the data are shown in Table 1.

[0148] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0149] Comparative Example 4

[0150] Similar to Example 1, except that polydiallyldimethylammonium chloride (PDDA) was replaced with tetrapropylammonium hydroxide (TPAOH), while the other steps were the same, to obtain Cata-4b.

[0151] In Cata-4b, XRD shows a characteristic peak at 1°–3°.

[0152] Probe reaction experiments were conducted on the catalyst sample Cata-4b, and the data are shown in Table 1.

[0153] The reaction was carried out using benzene and ethylene as raw materials according to the method of Example 1, under the same conditions as in Example 1, and the results are shown in Table 2.

[0154] Table 1

[0155]

[0156] The conversion rate of triisopropylbenzene represents the acidity of the catalyst's outer surface; the higher the conversion rate, the higher the acidity of the outer surface.

[0157] Table 2

[0158]

[0159] Table 1 shows that the core-shell molecular sieve of the present invention has high overall acidity and low acidity on the outer surface; Table 2 shows that the core-shell molecular sieve of the present invention has excellent para-shaped selectivity, with the para-diethylbenzene selectivity of Example 1 reaching 91.6%.

[0160] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a core-shell molecular sieve of MFI structure @MCM-41, characterized in that, The method includes: a) The ammonium-type MFI structured molecular sieve was subjected to hydrothermal treatment to obtain the first solid; b) The first solid is contacted with a mixed solution containing polydiallyldimethylammonium chloride and dodecyl polyoxyethylenemethylammonium chloride, separated, and dried to obtain the second solid; c) Mix the second solid with a mixed solution of the raw materials for synthesizing the MCM-41, including water, organic solvent, template agent and alkali source, until homogeneous; d) The raw materials from step III) are mixed evenly with a silicon source and hydrolyzed, then separated, washed, dried and calcined to obtain a solid; The core-shell molecular sieve has a core-shell coverage of 95-100%, and its XRD shows a characteristic peak at 1°-3°. The ratio of the amount of Brønsted acid on the outer surface to the total amount of Brønsted acid is 0.01-0.

2. Based on the total weight of core-shell molecular sieves, the content of MFI structured molecular sieves is 20-95% by weight, and the content of MCM-41 is 5-80%. The MFI structured molecular sieve is one or more of ZSM-5, TSZ, SEB-08, NU-4, NU-5 and TZ-1.

2. The preparation method according to claim 1, wherein, The ratio of the amount of Brønsted acid on the outer surface to the total amount of Brønsted acid is 0.01 to 0.09; and / or The shell thickness of the core-shell molecular sieve is 10 nm-150 nm; and / or The silicon-to-aluminum molar ratio (SiO2 / Al2O3) of the MFI-structured molecular sieve is 100-300; and / or The MFI structured molecular sieve has a crystal diameter of 100~400nm; and / or The core-shell molecular sieve is ZSM-5@MCM-41.

3. The preparation method according to claim 2, wherein, The shell thickness of the core-shell molecular sieve is 50-140 nm.

4. The preparation method according to claim 1, wherein, Repeat steps a)-d) multiple times with the solid.

5. The preparation method according to claim 4, wherein, Repeat steps a)-d) 1-4 times with the solid.

6. The preparation method according to claim 5, wherein, In step b), the mass ratio of MFI structured molecular sieve, polydiallyldimethylammonium chloride, dodecyl polyoxyethylenemethylammonium chloride, and water, on a dry basis, is 1:(0.4~3):(0.05~1):(50~500); and / or In step c), the mass ratio of the MFI structured molecular sieve, alkali source, template agent, organic solvent, and water, on a dry basis, is 1:(2~5):(0.5~2):(50~150):(100~500); and / or In step c), The alkali source is one or more of ammonia water, alkali metal and / or alkaline earth metal cations; and / or The template agent is selected from one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethyl-p-toluenesulfonium, hexadecyltrimethylammonium chloride, and hexadecyltrimethylammonium hydroxide; and / or The organic solvent is selected from one or more of ethanol, isopropanol, and methanol; and / or In step d), the mass ratio of the MFI-structured molecular sieve to the silicon source, on a dry basis, is 1:(0.1~2); and / or In step d), the silicon source is silicone grease.

7. The preparation method according to claim 6, wherein, In step b), the mass ratio of MFI structured molecular sieve, polydiallyl dimethyl ammonium chloride, dodecyl polyoxyethylene methyl ammonium chloride, and water, on a dry basis, is 1:(0.5~2):(0.1~0.5):(80~200); and / or In step c), the mass ratio of the MFI structured molecular sieve, alkali source, template agent, organic solvent, and water, on a dry basis, is 1:(2~5):(0.5~2):(80~150):(100~300); and / or In step d), the mass ratio of the MFI-structured molecular sieve to the silicon source, on a dry basis, is 1:(0.1~1); and / or In step d), the silicon source is tetraethyl orthosilicate.

8. The preparation method according to claim 1, wherein, In step a), the hydrothermal treatment conditions include: a temperature of 400-850℃; and / or Water vapor concentration of 20-100% by volume, and / or The time is 1-20 hours.

9. The preparation method according to claim 8, wherein, In step a), the hydrothermal treatment conditions include: a temperature of 500~700℃; and / or The time is 3 to 10 hours.

10. The preparation method according to claim 1, wherein, The preparation methods of MFI structured ammonium molecular sieves include: The MFI structure molecular sieve parent material is ammonium exchanged and dried to obtain an ammonium-type molecular sieve. The ammonium exchange process includes: mixing the MFI structure molecular sieve parent material with an ammonium salt solution to perform ammonium ion exchange, followed by drying.

11. The preparation method according to claim 10, wherein, During the ammonium ion exchange, the mixture is slurried according to a mass ratio of catalyst:ammonium salt:water = 1:(0.5-2):(5-20), and stirred for 0.5-3 hours at 25-95°C; and / or The ammonium exchange process is repeated 1-4 times; and / or The ammonium salt is one or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium oxalate, and ammonium phosphate.

12. The preparation method according to claim 11, wherein, The ammonium salt is ammonium chloride.

13. A method for preparing ZSM-5@MCM-41 core-shell molecular sieves using the preparation method described in claim 1, characterized in that, The method includes: I) The ZSM-5 parent material is ammonium exchanged and dried to obtain NH4-ZSM-5 ammonium molecular sieve. The ammonium exchange process includes: mixing the ZSM-5 parent material with an ammonium salt solution to perform ammonium ion exchange, slurrying according to the mass ratio of ZSM-5 parent material: ammonium salt: water = 1: (0.5-2): (5-20), stirring and exchanging at 25-95℃ for 0.5-3h, and repeating the ammonium exchange process 1-4 times. II) The above ammonium-exchanged sample is subjected to hydrothermal treatment, the hydrothermal treatment process includes: placing the sample in a hydrothermal furnace at 400-850℃ and calcining it in a 20-100% volume water vapor atmosphere for 1-20 hours. III) The hydrothermally treated sample was added to a mixed solution containing polydiallyldimethylammonium chloride and dodecyl polyoxyethylene methylammonium chloride, stirred at room temperature for 30-120 min, centrifuged, washed, and dried. The mass ratio of ZSM-5, polydiallyldimethylammonium chloride, dodecyl polyoxyethylene methylammonium chloride, and water was 1:(0.4~3):(0.05~1):(50~500) on a dry basis. IV) Add the solid from step III) to a mixed solution of ammonia, hexadecyltrimethylammonium bromide, ethanol and water, and ultrasonically disperse for 30-120 min; wherein, the mass ratio of ZSM-5, ammonia, hexadecyltrimethylammonium bromide, ethanol and water on a dry basis is 1:(2-5):(0.5-2):(50-150):(100-500); V) Under stirring conditions, add tetraethyl orthosilicate to the mixed solution in step IV), then stir at room temperature for 4-8 hours, centrifuge, wash, dry, and calcine. The mass ratio of ZSM-5 to tetraethyl orthosilicate on a dry basis is 1:(0.1-2).

14. The use of the core-shell molecular sieve obtained by any one of the preparation methods of claims 1-13 as a catalyst support and / or active component.

15. The use of the core-shell molecular sieve obtained by the preparation method according to any one of claims 1-13 in alkylation.

16. A method for synthesizing ethylbenzene and co-producing p-diethylbenzene by alkylation of ethylene and benzene, characterized in that, The method comprises contacting ethylene with benzene in the presence of a core-shell molecular sieve obtained by any one of the preparation methods of claims 1-13.

17. The method according to claim 16, wherein, The conditions for contact include: The temperature is 340~440℃, the pressure is 0.5~2MPa, the molar ratio of benzene to ethylene is 1~18, and the mass hourly space velocity of ethylene is 0.2~4h. -1 .

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