A mww molecular sieve, its preparation method and application

Abstract

This invention discloses a MWW molecular sieve, its preparation method, and its applications. The molecular sieve of this invention has a schematic chemical composition as shown in the formula "mSiO2·nAl2O3·pSDA1·qSDA2", where 20≤m / n≤35, 51≤m / p≤1000, 0.05≤p / q≤0.60, SDA1 is N,N,N-trimethyladamantane ammonium, and SDA2 is cyclohexylamine. The content of non-framework aluminum in the molecular sieve is less than 5% of the total aluminum content, and the content of aluminum located at the T2 site of the framework semi-supercage is more than 15% of the total aluminum content.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve technology, specifically relating to an MWW molecular sieve, its preparation method, and its application. Background Technology

[0002] In industry, molecular sieve materials are widely used in catalysis, ion exchange, adsorption, and separation due to their open structure and large surface area. Subtle differences in these material structures indicate variations in the various observable properties used to characterize them, such as morphology, specific surface area, pore size, and the variability of these dimensions. This also implies significant differences in their catalytic and adsorption properties.

[0003] The basic framework structure of crystalline microporous molecular sieves is based on a rigid three-dimensional TO4 (SiO4, AlO4, etc.) unit structure; in this structure, TO4 shares oxygen atoms in a tetrahedral manner, and the charge balance of the framework tetrahedrons such as AlO4 is achieved through surface cations such as Na. + H + The presence of these pores is maintained. This demonstrates that the framework properties of zeolites can be altered through cation exchange. Furthermore, zeolites possess a rich system of channels with specific pore sizes, which interweave to form a three-dimensional network structure. Even after the removal of water or organic matter from these channels, the framework remains stable (US4439409). Based on this structure, molecular sieves not only exhibit excellent catalytic activity and shape selectivity for various organic reactions, but also achieve good selectivity through modification (US6162416, US4954325, US5362697).

[0004] The molecular sieve with the MWW structure has two independent and non-interconnected ten-membered ring channel systems: one set of two-dimensional sinusoidal channels with an approximately elliptical cross-section and a pore size of 0.41 nm × 0.51 nm, and the other set of ten-membered ring channels containing an approximately cylindrical twelve-membered ring supercage with a size of 0.71 nm × 0.71 nm × 1.82 nm. This supercage is connected to the outside through a slightly distorted ten-membered ring window (0.40 nm × 0.55 nm).

[0005] In the synthesis of MWW molecular sieves, expensive or highly toxic piperidine or hexamethyleneimine are typically required as organic structure directing agents, significantly increasing the synthesis cost. CN104511271B discloses a molecular sieve and its preparation method, which involves introducing specific nitrogen-containing monocyclic C... 5-15A combination of two organic structure-directing agents, cycloalkanes (such as N,N-diethylcyclohexylamine, dicyclohexylamine, N-methyldicyclohexylamine, etc.) and azo aromatics (such as quinoline, N-phenylquinoline, N-cyclohexylpyridine, 6-methylquinoline, etc.), was used to synthesize SCM-1 molecular sieves with MWW structures. CN112939019A discloses a method for synthesizing MCM-49 molecular sieves with MWW structures, which requires the use of relatively expensive hexamethyleneimine as an organic structure-directing agent. CN103848433B discloses the synthesis of MCM-49 molecular sieves with MWW structures using a dual organic structure-directing agent, hexamethyleneimine-cyclohexylamine. The introduction of a second organic structure-directing agent, cyclohexylamine, significantly reduces the use of hexamethyleneimine. Although this reduces the cost of organic structure-directing agents to some extent, the problem of using the high-cost organic structure-directing agent hexamethyleneimine still exists, and the amount of organic structure-directing agent used is relatively large.

[0006] US5173281 discloses a method for synthesizing molecular sieves using cyclohexylamine, which has a lower cost, as an organic structure directing agent. However, the synthesized product contains a significant amount of FER impurities. CN108675313A discloses a method for synthesizing MCM-49 molecular sieves using cyclohexylamine as an organic structure directing agent. However, this method is complex, requiring the pre-preparation of a seed solution before adding seed crystals at a mass ratio of less than 20% to the silicon source. CN107010637B discloses a method for synthesizing silicon-aluminum MCM-49 molecular sieves with an MWW structure, using cyclohexylamine as an organic structure directing agent. However, the molar ratio of cyclohexylamine to the silicon source is 0.3–0.6, requiring a large amount. Furthermore, seed crystals at a mass ratio of 1–10% to the silicon source are needed for crystallization. In addition, when synthesizing MWW molecular sieves using only the seed method, the product yield is extremely low and the amount of seed crystals used is extremely large, significantly reducing the synthesis efficiency of this molecular sieve. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the preparation process of MWW molecular sieves in the prior art requires the addition of seed crystals and the amount of organic structure directing agent is large, which leads to low molecular sieve synthesis efficiency and high cost. The present invention provides an MWW molecular sieve, its preparation method and application. The molecular sieve has a unique chemical composition and morphology and has good performance when used as a catalyst.

[0008] The first aspect of the present invention provides an MWW molecular sieve having an illustrative chemical composition as shown in the formula "mSiO2·nAl2O3·pSDA1·qSDA2", wherein 20≤m / n≤35, 51≤m / p≤1000, 0.05≤p / q≤0.60, SDA1 is N,N,N-trimethyladamantaneammonium, and SDA2 is cyclohexylamine.

[0009] Furthermore, the molecular sieve has an illustrative chemical composition as shown in the formula “mSiO2·nAl2O3·pSDA1·qSDA2”, wherein 21≤m / n≤34, 52≤m / p≤800, preferably 52≤m / p≤120, and 0.10≤p / q≤0.58.

[0010] Furthermore, the content of non-framework aluminum in the molecular sieve is less than 5% of the total aluminum content, and the content of aluminum located at the T2 site of the framework semi-supercage is more than 15% of the total aluminum content, preferably 16% to 25%.

[0011] Furthermore, the molecular sieve crystals have a nanosheet morphology, the thickness of the crystals is not higher than 20 nm, preferably 10-20 nm, and the size of the nanosheets is not higher than 800 nm, preferably 100-800 nm.

[0012] A second aspect of this invention provides a method for preparing MWW molecular sieves, comprising the following steps:

[0013] The MWW molecular sieve is prepared by mixing a silicon source, an aluminum source, sodium hydroxide, organic structure directing agent a, organic structure directing agent b, and water, followed by crystallization.

[0014] The silicon source (SiO2), aluminum source (Al2O3), sodium hydroxide, organic structure directing agent a (SDA1) (N,N,N-trimethyladamantane), organic structure directing agent b (SDA2) (cyclohexylamine), and water are added in a molar ratio of SiO2:Al2O3:NaOH:SDA1:SDA2:H2O = 1:0.028~0.050:0.07~0.22:0.001~0.03:0.051~0.10:12~50.

[0015] Furthermore, the added silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), sodium hydroxide, organic structure directing agent a (calculated as N,N,N-trimethyladamantane ammonium), organic structure directing agent b (calculated as cyclohexylamine), and water are in a molar ratio of SiO2:Al2O3:NaOH:SDA1:SDA2:H2O = 1:0.029~0.048:0.08~0.21:0.001~0.028:0.055~0.095:14~40.

[0016] Furthermore, the silicon source is silica sol; the aluminum source is sodium aluminate.

[0017] Furthermore, the sodium aluminate contains 38% to 43% Al2O3 by weight and 30% to 33% Na2O by weight.

[0018] Furthermore, the crystallization conditions are crystallization at 130–180°C for 0.5–2.0 days, preferably at 140–170°C for 0.75–2.00 days.

[0019] Furthermore, the crystallization process of the reaction mixture is a dynamic crystallization by rotation or stirring, with a rotation or stirring speed of 10 to 300 rpm, preferably 10 to 100 rpm.

[0020] Furthermore, no seed crystals need to be added during the crystallization process of the molecular sieve.

[0021] Furthermore, the yield of the molecular sieve product exceeds 80%.

[0022] Furthermore, the crystallization can be carried out in any manner conventionally known in the art, such as by mixing the silicon source, aluminum source, sodium hydroxide, organic structure directing agent a, organic structure directing agent b and water in a predetermined ratio, and then heating the resulting mixture under crystallization conditions.

[0023] Furthermore, after the crystallization step, the product can be obtained from the obtained mixture by any conventionally known separation method. Examples of such separation methods include filtering, washing, and drying the obtained mixture. Here, the filtration, washing, and drying can be performed in any manner conventionally known in the art. Specifically, for example, the filtration can be performed by simply vacuum filtering the obtained product mixture. For example, washing can be performed using deionized water and / or ethanol. For example, the drying temperature can be 40–250°C, preferably 60–150°C, and the drying time can be 8–30 h, preferably 10–20 h. This drying can be carried out under normal pressure or under reduced pressure.

[0024] Furthermore, the MWW molecular sieve obtained after the crystallization step can be further processed by calcination to obtain sodium-type MWW molecular sieve. The calcination can be carried out in any manner conventionally known in the art, for example, the calcination temperature is generally 300–800°C, preferably 400–650°C, and the calcination time is generally 1–10 hours, preferably 3–6 hours. In addition, the calcination is generally carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere.

[0025] Furthermore, the total specific surface area of ​​the sodium-type MWW molecular sieve is not less than 400 m². 2 / gram, preferably 400-550 meters 2 / gram; the specific surface area of ​​the sodium-type MWW molecular sieve is not less than 50 m² / g; 2 / gram, preferably 60-120 meters 2 / g; the total pore volume of the sodium-type MWW molecular sieve is not less than 0.60 cm³. 3 / gram, preferably 0.60 to 1.20 cm 3 / g; the micropore volume of the sodium-type MWW molecular sieve is not less than 0.15 cm³. 3 / gram, preferably 0.15 to 0.22 cm 3 / gram.

[0026] Furthermore, the ammonium ion exchange of the molecular sieve involves exchanging the alkali metal cations Na in the sodium-type MWW molecular sieve. + Exchange for NH4 + Sodium-type MWW molecular sieves and ammonium salts are exchanged at a solid-liquid mass ratio of 1:5 to 1:20 at 20 to 60°C for 0.5 to 4 hours. This exchange can be done once or multiple times. After the ammonium ion exchange, the mixture is dried at 60 to 120°C for 4 to 24 hours and then calcined at 400 to 650°C for 1 to 12 hours in an oxygen or air atmosphere to obtain hydrogen-type MWW molecular sieves.

[0027] Furthermore, the ammonium salt used in the exchange is selected from at least one of ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium sulfate; the concentration of ammonium ions in the ammonium salt solution is 0.1–1 mol / L.

[0028] Furthermore, the total acid content of the hydrogen-type MWW molecular sieve is not less than 800 μmol / g, preferably 800–1600 μmol / g; the strong acid content of the molecular sieve is not less than 300 μmol / g, preferably 300–600 μmol / g.

[0029] A third aspect of the present invention also provides an MWW molecular sieve composition comprising an MWW molecular sieve prepared according to any of the methods described in the first aspect or according to any of the methods described in the second aspect, and a binder.

[0030] The fourth aspect of the present invention also provides the use of MWW molecular sieves prepared according to any of the methods described in the first aspect above, or MWW molecular sieves prepared according to any of the methods described in the second aspect above, or MWW molecular sieve compositions described in the third aspect above, as adsorbents or catalysts for the conversion of organic compounds.

[0031] Furthermore, the MWW molecular sieve is used as a catalyst in the alkylation of benzene and cyclohexene to produce cyclohexylbenzene.

[0032] Furthermore, the reaction conditions are as follows: reaction temperature 140–240℃, reaction pressure 1.0–5.0 MPa, benzene-olefin molar ratio 1.0–20.0, and olefin mass hourly space velocity 1.0–10 h⁻¹. 1 .

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The MWW molecular sieve of this invention has a unique chemical composition, such as the formula "mSiO2·nAl2O3·pSDA1·qSDA2". The content of non-framework aluminum in the molecular sieve is less than 5% of the total aluminum content, and the content of aluminum located at the T2 site of the framework semi-supercage is more than 15% of the total aluminum content. The molecular sieve crystals have a nanosheet morphology, the thickness of the crystals is no more than 20 nm, and the size of the nanosheets is no more than 800 nm.

[0035] The MWW molecular sieve of this invention is prepared by adding a small amount of dual organic directing agents (N,N,N-trimethyladamantane ammonium and cyclohexylamine) to a hydrothermal synthesis system, without the need for seed crystals or temperature-dependent crystallization. This method can reduce costs and improve the synthesis efficiency of molecular sieves. Attached Figure Description

[0036] Figure 1 The X-ray diffraction pattern of the sample in Example 1;

[0037] Figure 2 This is a scanning electron microscope image of the sample in Example 1;

[0038] Figure 3 The sample in Example 1 13 C10 NMR spectrum;

[0039] Figure 4 For the samples in Example 1 and Example 2 27 Al NMR spectrum;

[0040] Figure 5 The X-ray diffraction pattern of the sample in Example 2;

[0041] Figure 6 This is a scanning electron microscope image of the sample in Example 2;

[0042] Figure 7 The X-ray diffraction pattern of the sample in Example 3;

[0043] Figure 8 This is a scanning electron microscope image of the sample in Example 3;

[0044] Figure 9 The X-ray diffraction pattern of the sample in Example 4;

[0045] Figure 10 This is a scanning electron microscope image of the sample in Example 4;

[0046] Figure 11 The X-ray diffraction pattern of the sample in Comparative Example 1 is shown.

[0047] Figure 12 The X-ray diffraction pattern of the sample in Comparative Example 2;

[0048] Figure 13 The X-ray diffraction pattern of the sample in Comparative Example 3 is shown.

[0049] Figure 14 The X-ray diffraction pattern of the sample in Comparative Example 4;

[0050] Figure 15 The X-ray diffraction pattern of the sample in Comparative Example 5;

[0051] Figure 16 For the samples in Comparative Example 5 27 Al NMR spectrum;

[0052] Figure 17 The X-ray diffraction pattern of the sample in Comparative Example 6 is shown. Detailed Implementation

[0053] In the context of this specification, the structure of the molecular sieve is determined by X-ray diffraction (XRD), which is measured using an X-ray powder diffractometer with a Cu-Kα ray source and a nickel filter. Before sample testing, the crystallinity of the molecular sieve sample is observed using a scanning electron microscope (SEM) to confirm that the sample contains only one type of crystal, i.e., the molecular sieve sample is a pure phase. XRD testing is then performed to ensure that there are no interfering peaks from other crystals in the diffraction pattern.

[0054] In the context of this specification, including in the following examples and comparative examples, the X-ray powder diffractometer used for the molecular sieves is a Panalytical X-PERPRO type X-ray powder diffractometer, used to analyze the phase composition of the samples, and a CuKα ray source. Nickel filter, 2θ scanning range 2~50°, operating voltage 40KV, current 40mA, scanning rate 10° / min.

[0055] In the context of this specification, including in the following examples and comparative examples, the scanning electron microscope (SEM) used for the molecular sieves is an S-4800II field emission scanning electron microscope. The molecular sieves were observed using this SEM at a magnification of 40,000x. A random field of view was selected, and the average sum of the crystal sizes in that field of view was calculated. This operation was repeated a total of 10 times, and the average sum of the 10 averages was taken as the crystal size.

[0056] In the context of this specification, including in the following examples and comparative examples, the method for measuring the crystal thickness of the molecular sieve is as follows: the molecular sieve is observed using a transmission electron microscope (FEI G2F30 transmission electron microscope, operating voltage 300kV) at a magnification of 100,000x, a field of view is randomly selected, and the thickness of all crystals in that field of view is measured. This operation is repeated 5 times, and the average value of the 5 measurements is taken as the average thickness of the crystal.

[0057] In the context of this specification, including in the following examples and comparative examples, the pore volume, specific surface area, and external specific surface area of ​​the molecular sieve were measured by the nitrogen physical adsorption-desorption method (BET method): the nitrogen physical adsorption-desorption isotherm of the molecular sieve was measured using a Micromeretic ASAP2020M physical adsorption instrument, and then calculated using the BET equation and t-plot equation. The experimental conditions for this molecular sieve were: measurement temperature -196°C; before measurement, the molecular sieve was heat-treated at 550°C in air for 6 hours, and then pretreated in vacuum at 350°C for 4 hours.

[0058] In the context of this specification, including in the following examples and comparative examples, the content of each element in the molecular sieve was determined by inductively coupled plasma atomic emission spectrometry (ICP) using a Varian 725-ES instrument. The analytical sample was dissolved in hydrofluoric acid before testing, and the content was expressed in moles.

[0059] In the context of this specification, including in the following examples and comparative examples, the acid content of the hydrogen-form molecular sieves was determined using NH3-TPD chemisorption-desorption curves (Altamira AMI-3300 instrument). Before testing, the samples were activated at 550°C for 1 hour, ammonia was adsorbed at 100°C for 20 minutes, and then desorbed and detected at 100–600°C. The acid content corresponding to desorption temperatures above 300°C, determined by Gaussian peak segmentation, can be considered as the acid content of strong acids.

[0060] In the context of this specification, including in the following examples and comparative examples, the content of framework aluminum and non-framework aluminum in the molecular sieve is determined by... 27 Al NMR spectroscopy was performed using a Bruker AvanceⅢ / WB-400 instrument. Peaks with chemical shifts around 0 ppm corresponded to non-framework aluminum, while peaks with chemical shifts in the range of 65–35 ppm corresponded to framework aluminum. The percentage of the non-framework aluminum peak area relative to the sum of the two peak areas (total peak area) represents the non-framework aluminum content. Simultaneously, Gaussian peak partitioning was used; the percentage of the area corresponding to the peak with a chemical shift around 60 ppm relative to the total peak area represents the aluminum content at the framework semi-supercage T2 site.

[0061] In the context of this specification, including in the following examples and comparative examples, the types of organic matter in the molecular sieves are determined by... 13 The chemical shifts of organic compounds in the molecular sieve were determined by comparing them with the standard chemical shifts and peak areas of N,N,N-trimethyladamantane ammonium and cyclohexylamine. The chemical shifts of standard cyclohexylamine were 50.4 ppm, 35.5 ppm, 25.8 ppm, and 24.6 ppm, and the chemical shifts of standard N,N,N-trimethyladamantane ammonium were 73.0 ppm, 48.0 ppm, 36.5 ppm, 32.5 ppm, and 29.8 ppm.

[0062] In the context of this specification, including in the following examples and comparative examples, the organic content in the molecular sieves was determined by thermogravimetric analysis (TGA) using an SDT Q600 V20.9 Build 20 instrument. The sample was heated from 50°C to 800°C at a rate of 10°C / min in air or oxygen atmosphere to detect weight loss. The percentage of weight loss of the sample within the range of 200–700°C was taken as the organic content of the sample.

[0063] In the context of this specification, including in the following examples and comparative examples, the yield of molecular sieves refers to the percentage of the mass of the calcined sample relative to the sum of the masses of SiO2 and Al2O3 contained in the raw material.

[0064] In the context of this specification, including in the following examples and comparative examples, the catalyst is used to carry out the alkylation reaction of benzene and cyclohexene:

[0065] Selectivity of cyclohexylbenzene % = (molar amount of target cyclohexylbenzene in the product) / (total molar amount of alkylbenzenes in the product) × 100%.

[0066] Selectivity % for cyclohexylbenzene and dicyclohexylbenzene = (molar amount of cyclohexylbenzene in the product + molar amount of dicyclohexylbenzene) / (total molar amount of alkylbenzenes in the product) × 100%.

[0067] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0068] Example 1

[0069] A mixture was prepared by stirring 22.98 g of deionized water, 0.846 g of sodium aluminate (containing 40.5 wt% Al2O3 and 30.6 wt% Na2O), 0.169 g of sodium hydroxide, 0.85 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.95 g of cyclohexylamine (organic structure directing agent b), and 15.15 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0070] SiO2 / Al2O3 = 30;

[0071] NaOH / SiO2 = 0.12;

[0072] N,N,N-trimethyladamantane ammonium / SiO2 = 0.010;

[0073] Cyclohexylamine / SiO2 = 0.095;

[0074] H2O / SiO2 = 18.

[0075] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C with a stirring speed of 20 rpm for 1.5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 1 The sample shown is an MWW molecular sieve with a yield of 91 wt%. The SEM image of the sample is shown below. Figure 2 As shown, the crystals are in the form of nanosheets, with a thickness of 18 nm and a size of 500 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 29.6 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 The C NMR spectrum is as follows Figure 3 As shown, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) is 1:4.8, and the chemical composition of the sample's molar ratio is "1SiO2·0.034Al2O3·0.009SDA1·0.043SDA2". The sample's... 27 Al NMR spectrum as shown Figure 4 As shown, the aluminum content in the non-skeletal structure is 0.9%, and the aluminum content at the T2 site of the skeletal semi-supercage is 17.6%.

[0076] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​526 m². 2 / gram, with an external specific surface area of ​​105 m² measured by the BET method. 2 / g; Total pore volume 0.86cm 3 / gram, micropore volume is 0.18 cm³3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 1077 μmol / g, and the strong acid content was 472 μmol / g.

[0077] Example 2

[0078] A mixture was prepared by stirring 26.59 g of deionized water, 0.866 g of sodium aluminate (containing 40.5 wt% Al2O3 and 30.6 wt% Na2O), 0.297 g of sodium hydroxide, 1.74 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.87 g of cyclohexylamine (organic structure directing agent b), and 15.51 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0079] SiO2 / Al2O3 = 30;

[0080] NaOH / SiO2 = 0.15;

[0081] N,N,N-Trimethyladamantaneammonium / SiO2 = 0.020;

[0082] Cyclohexylamine / SiO2 = 0.085;

[0083] H2O / SiO2 = 20.

[0084] The mixture was placed in a stainless steel reactor and heated to crystallize at 155°C with a stirring speed of 30 rpm for 2 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 5 The sample shown is an MWW molecular sieve with a yield of 90 wt%. The SEM image of the sample is shown below. Figure 6 As shown, the crystals are in the form of nanosheets, with a thickness of 18 nm and a size of 400 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 29.8 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similarly, the ratio of N,N,N-trimethyladamantane (SDA1) to cyclohexylamine (SDA2) was 1:2.2, and the chemical composition of the sample molar ratio was "1SiO2·0.034Al2O3·0.019SDA1·0.042SDA2". The sample's...27 Al NMR spectrum as shown Figure 4 As shown, the aluminum content in the non-skeletal structure is 0.8%, and the aluminum content at the T2 site of the skeletal semi-supercage is 16.9%.

[0085] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​511 m². 2 / gram, with an external specific surface area of ​​108 m² measured by the BET method. 2 / g; Total pore volume 0.81cm 3 / gram, micropore volume is 0.17 cm³ 3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 1035 μmol / g, and the strong acid content was 452 μmol / g.

[0086] Example 3

[0087] A mixture was prepared by stirring 18.92 g of deionized water, 0.833 g of sodium aluminate (containing 42.5 wt% Al2O3 and 30.6 wt% Na2O), 0.219 g of sodium hydroxide, 0.41 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.77 g of cyclohexylamine (organic structure directing agent b), and 14.58 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0088] SiO2 / Al2O3 = 28;

[0089] NaOH / SiO2 = 0.14;

[0090] N,N,N-Trimethyladamantaneammonium / SiO2 = 0.005;

[0091] Cyclohexylamine / SiO2 = 0.080;

[0092] H2O / SiO2 = 16.

[0093] The mixture was placed in a stainless steel reactor and heated to crystallize at 165°C with a stirring speed of 40 rpm for 1.5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 7 The sample shown is an MWW molecular sieve with a yield of 87 wt%. The SEM image of the sample is shown below. Figure 8As shown, the crystals are in the form of nanosheets, with a thickness of 16 nm and a size of 350 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 28.1 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similar to Example 1, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) was 1:6.1, and the chemical composition of the sample molar ratio was "1SiO2·0.036Al2O3·0.005SDA1·0.031SDA2". The sample's... 27 Al NMR spectrum and Figure 4 Similar to Example 1, the content of non-skeletal aluminum is 1.1%, and the content of aluminum at the T2 site of the skeletal semi-supercage is 18.8%.

[0094] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​478 m². 2 / gram, with an external specific surface area of ​​74 m² measured by the BET method. 2 / g; Total pore volume 0.78cm 3 / gram, micropore volume is 0.19 cm³ 3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 1241 μmol / g, and the strong acid content was 506 μmol / g.

[0095] Example 4

[0096] A mixture was prepared by stirring 33.78 g of deionized water, 0.780 g of sodium aluminate (containing 40.5 wt% Al2O3 and 33 wt% Na2O), 0.322 g of sodium hydroxide, 0.21 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.59 g of cyclohexylamine (organic structure directing agent b), and 14.89 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0097] SiO2 / Al2O3 = 32;

[0098] NaOH / SiO2 = 0.16;

[0099] N,N,N-trimethyladamantane ammonium / SiO2 = 0.0025;

[0100] Cyclohexylamine / SiO2 = 0.060;

[0101] H2O / SiO2 = 24.

[0102] The mixture was placed in a stainless steel reactor and heated to 170°C with a stirring speed of 10 rpm for one day for crystallization. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 9 The sample shown is an MWW molecular sieve with a yield of 89 wt%. The SEM image of the sample is shown below. Figure 10 As shown, the crystals are in the form of nanosheets, with a thickness of 16 nm and a size of 550 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 32.2 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similar to Example 1, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) was 1:7.9, and the chemical composition of the sample molar ratio was "1SiO2·0.031Al2O3·0.002SDA1·0.016SDA2". The sample's... 27 Al NMR spectrum and Figure 4 Similar to Example 1, the content of non-skeletal aluminum is 1.4%, and the content of aluminum at the T2 site of the skeletal semi-supercage is 19.2%.

[0103] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​496 m². 2 / gram, with an external specific surface area of ​​69 m² measured by the BET method. 2 / g; Total pore volume 0.88cm 3 / gram, micropore volume is 0.19 cm³ 3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 971 μmol / g, and the strong acid content was 434 μmol / g.

[0104] Example 5

[0105] A mixture was prepared by stirring 37.53 g of deionized water, 0.948 g of sodium aluminate (containing 40.5 wt% Al2O3 and 30.6 wt% Na2O), 0.401 g of sodium hydroxide, 1.98 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.65 g of cyclohexylamine (organic structure directing agent b), and 14.14 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0106] SiO2 / Al2O3 = 25;

[0107] NaOH / SiO2 = 0.20;

[0108] N,N,N-Trimethyladamantaneammonium / SiO2 = 0.025;

[0109] Cyclohexylamine / SiO2 = 0.070;

[0110] H2O / SiO2 = 28.

[0111] The mixture was placed in a stainless steel reactor and heated to crystallize at 155°C with a stirring speed of 60 rpm for 2 days. After crystallization, it was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product was compared with... Figure 1 Similarly, the sample was an MWW molecular sieve with a yield of 87 wt%. The SEM image of the sample is similar to... Figure 2 Similarly, the crystals are in the form of nanosheets, with a thickness of 14 nm and a size of 300 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 25.3 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similar to Example 1, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) was 1:1.8, and the chemical composition of the sample molar ratio was "1SiO2·0.040Al2O3·0.018SDA1·0.032SDA2". The sample's... 27 Al NMR spectrum and Figure 4 Similar to Example 1, the content of non-skeletal aluminum is 1.0%, and the content of aluminum at the T2 site of the skeletal semi-supercage is 16.5%.

[0112] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​467 m². 2 / gram, with an external specific surface area of ​​115 m² measured by the BET method. 2 / g; Total pore volume 0.95cm 3 / gram, micropore volume is 0.17 cm³3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 1344 μmol / g, and the strong acid content was 478 μmol / g.

[0113] Example 6

[0114] A mixture was prepared by stirring 44.35 g of deionized water, 1.009 g of sodium aluminate (containing 40.5 wt% Al2O3 and 30.6 wt% Na2O), 0.178 g of sodium hydroxide, 0.62 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.50 g of cyclohexylamine (organic structure directing agent b), and 13.84 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0115] SiO2 / Al2O3 = 23;

[0116] NaOH / SiO2 = 0.15;

[0117] N,N,N-Trimethyladamantaneammonium / SiO2 = 0.008;

[0118] Cyclohexylamine / SiO2 = 0.055;

[0119] H2O / SiO2 = 32.

[0120] The mixture was placed in a stainless steel reactor and heated to crystallize at 150°C with a stirring speed of 30 rpm for 2 days. After crystallization, it was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product was compared with... Figure 1 Similarly, the sample was an MWW molecular sieve with a yield of 88 wt%. The SEM image of the sample is similar to... Figure 2 Similarly, the crystals are in the form of nanosheets, with a thickness of 19 nm and a size of 420 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 23.3 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similar to Example 1, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) was 1:4.2, and the chemical composition of the sample molar ratio was "1SiO2·0.043Al2O3·0.007SDA1·0.029SDA2". The sample's...27 Al NMR spectrum and Figure 4 Similar to Example 1, the content of non-skeletal aluminum is 0.9%, and the content of aluminum at the T2 site of the skeletal semi-supercage is 18.1%.

[0121] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​508 m². 2 / gram, with an external specific surface area of ​​91 m² measured by the BET method. 2 / g; Total pore volume 1.03cm 3 / gram, micropore volume is 0.19 cm³ 3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 1396 μmol / g, and the strong acid content was 543 μmol / g.

[0122] Example 7

[0123] A mixture was prepared by stirring 49.52 g of deionized water, 1.078 g of sodium aluminate (containing 40.5 wt% Al2O3 and 30.6 wt% Na2O), 0.001 g of sodium hydroxide, 0.91 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.58 g of cyclohexylamine (organic structure directing agent b), and 13.50 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0124] SiO2 / Al2O3 = 21;

[0125] NaOH / SiO2 = 0.11;

[0126] N,N,N-trimethyladamantane ammonium / SiO2 = 0.012;

[0127] Cyclohexylamine / SiO2 = 0.065;

[0128] H2O / SiO2 = 36.

[0129] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C with a stirring speed of 10 rpm for 1.5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product was compared with... Figure 1 Similarly, the sample was an MWW molecular sieve with a yield of 89 wt%. The SEM image of the sample is similar to... Figure 2Similarly, the crystals are in the form of nanosheets, with a thickness of 16 nm and a size of 340 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 21.1 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similar to Example 1, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) was 1:3.3, and the chemical composition of the sample molar ratio was "1SiO2·0.047Al2O3·0.011SDA1·0.036SDA2". The sample's... 27 Al NMR spectrum and Figure 4 Similar to Example 1, the content of non-skeletal aluminum is 1.4%, and the content of aluminum at the T2 site of the skeletal semi-supercage is 17.7%.

[0130] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​462 m². 2 / gram, with an external specific surface area of ​​95 m² measured by the BET method. 2 / g; Total pore volume 0.75cm 3 / gram, micropore volume is 0.20 cm³ 3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 1478 μmol / g, and the strong acid content was 552 μmol / g.

[0131] Example 8

[0132] A mixture was prepared by stirring 12.30 g of deionized water, 0.536 g of sodium aluminate (containing 40.5 wt% Al2O3 and 30.6 wt% Na2O), 0.322 g of sodium hydroxide, 0.97 g of N,N,N-trimethyladamantane ammonium solution (containing 25.12 wt% N,N,N-trimethyladamantane ammonium) (organic structure directing agent a), 0.54 g of cyclohexylamine (organic structure directing agent b), and 10.87 g of silica sol (containing 40.0 wt% SiO2) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0133] SiO2 / Al2O3 = 34;

[0134] NaOH / SiO2 = 0.18;

[0135] N,N,N-trimethyladamantane ammonium / SiO2 = 0.016;

[0136] Cyclohexylamine / SiO2 = 0.075;

[0137] H2O / SiO2 = 15.

[0138] The mixture was placed in a stainless steel reactor and heated to crystallize at 165°C with a stirring speed of 20 rpm for one day. After crystallization, it was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product was compared with... Figure 1 Similarly, the sample was an MWW molecular sieve with a yield of 89 wt%. The SEM image of the sample is similar to... Figure 2 Similarly, the crystals are in the form of nanosheets, with a thickness of 15 nm and a size of 450 nm. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 33.8 using inductively coupled plasma atomic emission spectrometry (ICP). The sample... 13 C NMR spectrum and Figure 3 Similar to Example 1, the ratio of N,N,N-trimethyladamantane ammonium (SDA1) to cyclohexylamine (SDA2) was 1:2.7, and the chemical composition of the sample molar ratio was "1SiO2·0.030Al2O3·0.014SDA1·0.038SDA2". The sample's... 27 Al NMR spectrum and Figure 4 Similar to Example 1, the content of non-skeletal aluminum is 1.5%, and the content of aluminum at the T2 site of the skeletal semi-supercage is 17.2%.

[0139] The sodium-type molecular sieve obtained after calcining the sample in air at 550℃ for 6 hours had a specific surface area of ​​519 m². 2 / gram, with an external specific surface area of ​​106 m² measured by the BET method. 2 / g; Total pore volume 0.93cm 3 / gram, micropore volume is 0.18 cm³ 3 / g. Sodium-type molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 45℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 6 hours to obtain hydrogen-type MWW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 887 μmol / g, and the strong acid content was 388 μmol / g.

[0140] Comparative Example 1

[0141] The material ratio and crystallization temperature are the same as in Example 3, except that the synthesis time is extended to 5 days.

[0142] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C with a stirring speed of 20 rpm for 5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 11 As shown, the sample is a mixture of FER and MWW structures, and is not an MWW molecular sieve.

[0143] Comparative Example 2

[0144] The material ratio and crystallization temperature are the same as in Example 4, except that the synthesis time is extended to 4 days.

[0145] The mixture was placed in a stainless steel reactor and heated to crystallize at 170°C with a stirring speed of 10 rpm for 4 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 12 As shown, the sample is a mixture of FER and MWW structures, and is not an MWW molecular sieve.

[0146] Comparative Example 3

[0147] The material ratio is the same as in Example 1, except that N,N,N-trimethyladamantane ammonium (SDA1) is not added. The final material ratio (molar ratio) is:

[0148] SiO2 / Al2O3 = 30;

[0149] NaOH / SiO2 = 0.12;

[0150] Cyclohexylamine / SiO2 = 0.095;

[0151] H2O / SiO2 = 18.

[0152] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C with a stirring speed of 20 rpm for 1.5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 13 As shown, the sample has an FER structure and is not an MWW molecular sieve.

[0153] Comparative Example 4

[0154] The material ratio is the same as in Example 2, except that cyclohexylamine (SDA2) is not added. The final material ratio (molar ratio) is:

[0155] SiO2 / Al2O3 = 30;

[0156] NaOH / SiO2 = 0.15;

[0157] N,N,N-Trimethyladamantaneammonium / SiO2 = 0.020;

[0158] H2O / SiO2 = 20.

[0159] The mixture was placed in a stainless steel reactor and heated to crystallize at 155°C with a stirring speed of 30 rpm for 2 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 14 As shown, the sample is an amorphous material and is not an MWW molecular sieve.

[0160] Comparative Example 5

[0161] The material ratio is the same as in Example 1, except that a larger amount of N,N,N-trimethyladamantane ammonium is added. The final material ratio (molar ratio) is:

[0162] SiO2 / Al2O3 = 30;

[0163] NaOH / SiO2 = 0.12;

[0164] N,N,N-trimethyladamantane ammonium / SiO2 = 0.15;

[0165] Cyclohexylamine / SiO2 = 0.095;

[0166] H2O / SiO2 = 18.

[0167] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C with a stirring speed of 20 rpm for 1.5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 15 The image shown is of the MWW molecular sieve. However, the sample... 27 Al NMR spectrum as shown Figure 16 As shown, the aluminum content in the non-skeletal structure is 7.1%, and the aluminum content at the T2 site of the skeletal semi-supercage is 6.2%.

[0168] Comparative Example 6

[0169] The material ratio is the same as in Example 1, except that the added sodium aluminate contains different contents of Al2O3 and Na2O (containing 50.6% by weight of Al2O3 and 45.2% by weight of Na2O). The raw materials are prepared in the same amount of substances.

[0170] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C with a stirring speed of 20 rpm for 1.5 days. After crystallization, the mixture was filtered, washed, and dried overnight in an oven at 100°C. The XRD pattern of the obtained product is shown below. Figure 17 As shown, the raw material was only partially crystallized, and the sample was a mixture of amorphous material and MWW molecular sieve.

[0171] Examples 9-16

[0172] The hydrogen-form MWW molecular sieve powder samples synthesized in Examples 1-8 were crushed and sieved to obtain 0.35 g of the 20-40 mesh particle size fraction, which was then placed in a fixed-bed reactor for liquid-phase alkylation reaction of benzene and cyclohexene. The reaction conditions were: reaction temperature 150-220℃, reaction pressure 1.5-3.5 MPa, benzene-to-olefin molar ratio 2.0-10.0, and cyclohexene mass hourly space velocity 1.0-10 h⁻¹. 1 The specific reaction conditions for each embodiment are shown in Table 1. The products, catalyst activity, and product selectivity were analyzed using a Shimadzu GC-2014 gas chromatograph, as shown in Table 1.

[0173] Comparative Example 7

[0174] Similar to Examples 9-16, the catalyst obtained after treating the hydrogen-type MWW molecular sieve synthesized in Comparative Example 5 was reacted. The catalyst activity and product selectivity are shown in Table 1.

[0175] Table 1. Catalyst performance results for Examples 9-16 and Comparative Example 7.

[0176]

[0177] The specific 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 combining the 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 MWW molecular sieve, wherein the molecular sieve has a schematic chemical composition as shown in the formula "mSiO2•nAl2O3•pSDA1•qSDA2", wherein 20≤m / n≤35, 51≤m / p≤1000, 0.05≤p / q≤0.60, SDA1 is N,N,N-trimethyladamantaneammonium, and SDA2 is cyclohexylamine; the content of non-framework aluminum in the molecular sieve is less than 5% of the total aluminum content, and the content of aluminum located at the T2 site of the framework semi-supercage is more than 15% of the total aluminum content; the molecular sieve crystals are in the form of nanosheets, the thickness of the crystals is not higher than 20 nm, and the size of the nanosheets is not higher than 800 nm.

2. The MWW molecular sieve according to claim 1, characterized in that, 21≤m / n≤34, 52≤m / p≤800.

3. The MWW molecular sieve according to claim 2, characterized in that, 52≤m / p≤120, 0.10≤p / q≤0.

58.

4. The MWW molecular sieve according to claim 1, characterized in that, The aluminum content in the molecular sieve located at the T2 site of the semi-supercage in the framework is higher than 16% to 25% of the total aluminum content.

5. The MWW molecular sieve according to claim 1, characterized in that, The thickness of the molecular sieve crystal is 10~20nm, and the size of the nanosheet is 100~800nm.

6. A method for preparing the MWW molecular sieve according to any one of claims 1-5, comprising the following steps: The MWW molecular sieve is prepared by mixing a silicon source, an aluminum source, sodium hydroxide, organic structure directing agent a, organic structure directing agent b, and water, followed by crystallization. The silicon source is calculated as SiO2, the aluminum source as Al2O3, sodium hydroxide, organic structure directing agent a as N,N,N-trimethyladamantane ammonium, organic structure directing agent b as cyclohexylamine, and water, in a molar ratio of SiO2:Al2O3:NaOH:SDA1:SDA2:H2O=1:0.028~0.050:0.07~0.22:0.001~0.03:0.051~0.10:12~50; The aluminum source is sodium aluminate, wherein the content of Al2O3 in the sodium aluminate is 38%~43% by weight, and the content of Na2O is 30%~33% by weight. The reaction mixture was crystallized at 130-180°C for 0.5-2.0 days.

7. The preparation method according to claim 6, characterized in that, The added silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), sodium hydroxide, organic structure directing agent a (calculated as N,N,N-trimethyladamantane), organic structure directing agent b (calculated as cyclohexylamine), and water are in a molar ratio of SiO2:Al2O3:NaOH:SDA1:SDA2:H2O=1:0.029~0.048:0.08~0.21:0.001~0.028:0.055~0.095:14~40.

8. The preparation method according to claim 6, characterized in that, The silicon source is silica sol.

9. The preparation method according to claim 6, characterized in that, The reaction mixture was crystallized at 140-170°C for 0.75-2.00 days.

10. The preparation method according to claim 6, characterized in that, The crystallization process of the reaction mixture is a dynamic crystallization by rotation or stirring, with a rotation or stirring speed of 10~300 rpm.

11. The preparation method according to claim 10, characterized in that, The rotation or stirring speed is 10~100 rpm.

12. The preparation method according to claim 6, characterized in that, No seed crystals need to be added during the crystallization process of the molecular sieve.

13. An MWW molecular sieve composition comprising an MWW molecular sieve according to any one of claims 1 to 5 or an MWW molecular sieve prepared according to any one of claims 6 to 12, and a binder.

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