Preparation of thin-layered titanium silicalite molecular sieve Ti-MWW and application thereof in epoxidation reaction

Abstract

The application discloses a kind of preparation of thin-layer Ti-MWW titanium silicalite and its application in epoxidation reaction, belong to inorganic chemical synthesis technical field.The application adds polycyclic aliphatic amine in the synthesis process of Ti-MWW molecular sieve, and reduces the crystallization temperature in the early stage of molecular sieve crystallization to delay the growth rate of molecular sieve C axis, obtain shorter C axis thin-layer Ti-MWW, greatly improve the diffusion performance of Ti-MWW molecular sieve by this method, increase the diffusion rate of reactant molecules in channel, so that the catalytic performance of molecular sieve is greatly improved, suitable for catalyzing propylene, butylene, hexene, cyclohexene, octene liquid phase epoxidation and the like.

Description

Technical Field

[0001] This invention belongs to the field of inorganic chemical synthesis technology, specifically relating to the preparation of a thin-layered Ti-MWW titanium-silicon molecular sieve and its application in epoxidation reactions. Background Technology

[0002] In 1983, Taramasso successfully incorporated the transition metal element Ti into an all-silica zeolite framework, developing the titanium-silica molecular sieve TS-1 (GB2071071A, USP4410501, 1983), expanding the catalytic applications of molecular sieves from acid-base catalysis to selective oxidation catalysis. However, due to the diffusion limitations of the micropores, TS-1 molecular sieves exhibited relatively low activity in the catalytic oxidation of macromolecular olefins. To address this issue, developing titanium-silica molecular sieves with larger pore structures has been a top research priority.

[0003] Ti-MWW molecular sieves possess two independent pore systems: one consisting of elliptical 10-membered ring sinusoidal channels, and the other consisting of 10-membered ring straight channels connected to 12-membered ring supercages with a diameter of approximately 0.7 nm, with 12-membered ring cups distributed on their crystal surface. This unique pore system enables Ti-MWW molecular sieves to exhibit superior catalytic performance compared to titanium-silicon molecular sieve TS-1 in a series of catalytic oxidation reactions, such as olefin epoxidation, aldehyde and ketone ammoxidation, and the oxidation of pyridine and sulfides. Notably, the Ti-MWW / H₂O₂ catalytic system was used for the first time to achieve the industrial application of ammoxidation of butanone to butanone oxime.

[0004] Currently, the main synthesis method for Ti-MWW molecular sieves utilizes a single-template agent, cycloheximine or piperidine, as an organic directing agent, fumed silica or alkaline silica sol as the silicon source, tetrabutyl titanate as the titanium source, and boric acid as a crystallization aid, undergoing hydrothermal crystallization at a specific temperature. However, this method results in a significant waste of boric acid resources. Subsequent researchers developed a method using a dual-template agent, adamantane ammonium hydroxide, and cycloheximine as organic directing agents, with potassium carbonate as a crystallization aid, to prepare Ti-MWW molecular sieves. Regardless of the synthesis method used, although the prepared Ti-MWW exhibits certain advantages in pore structure compared to TS-1 molecular sieves, it still cannot achieve ideal oxidation reactivity in some macromolecular olefin epoxidation reactions.

[0005] Furthermore, selectively controlling the length of specific axes of molecular sieves can effectively optimize their catalytic performance. Due to diffusion limitations, catalytic reactions involving some macromolecules are more likely to occur at the pore openings of molecular sieves. Crystals with shorter lengths along specific axes are more conducive to exposing more pore structures for reaction participation compared to bulk crystals, and also facilitate molecule diffusion. Therefore, designing and synthesizing molecular sieve crystals with specific preferred orientations has become a research focus. From an industrial application perspective, developing thin-layered Ti-MWW molecular sieves with shorter C-axis is of great significance. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a method for preparing thin-layered Ti-MWW titanium-silicon molecular sieves and their application in epoxidation reactions. This invention innovatively incorporates polycyclic aliphatic amines during the synthesis of Ti-MWW molecular sieves and lowers the crystallization temperature in the early stages of molecular sieve crystallization to slow down the growth rate of the C-axis, resulting in thin-layered Ti-MWW with a shorter C-axis. This method significantly improves the diffusion performance of Ti-MWW molecular sieves, increases the diffusion rate of reactant molecules within the pores, and thus greatly enhances the catalytic performance of the molecular sieve. It is suitable for catalyzing reactions such as the liquid-phase epoxidation of propylene, butene, hexene, cyclohexene, and octene.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a thin-layered Ti-MWW titanium-silicon molecular sieve, comprising the following steps:

[0009] (1) Mix the template agent and water evenly, add the titanium source drop by drop, stir evenly, and obtain gel A;

[0010] (2) Mix the polycyclic fatty amine and water evenly, add the silicon source, stir evenly, and obtain gel B;

[0011] (3) Slowly add gel A to gel B, stir evenly, then add boric acid additive and stir evenly;

[0012] (4) The reaction solution obtained in step (3) is stirred and crystallized at 100-150℃ for 5-36 hours, then stirred at 150-210℃ for 4-8 days, cooled down, and the resulting mother liquor is filtered, washed, and dried to obtain thin-layer Ti-MWW molecular sieve raw powder.

[0013] (5) Disperse the Ti-MWW molecular sieve raw powder in a nitric acid solution with a concentration of 1-5 mol / L and treat it at 60-110℃ for 0.5-2 days. Centrifuge, wash, dry, and calcine in air at 400-650℃ for 5-24 hours to obtain Ti-MWW titanium-silicon molecular sieve catalyst.

[0014] Based on the above technical solution, further, the template agent mentioned in step (1) is one or a combination of two or more of piperidine, cycloheximine, and piperazine.

[0015] Based on the above technical solution, further, the titanium source mentioned in step (1) is one or a combination of two or more of tetrabutyl titanate, tetraisopropyl titanate, titanium tetrachloride, titanium sulfate, hexafluorotitanic acid or ammonium hexafluorotitanic acid.

[0016] Based on the above technical solution, further, the mass ratio of titanium source, template agent and water in step (1) is 1:5 to 10:10 to 20.

[0017] Based on the above technical solution, further, the silicon source mentioned in step (2) is one or a combination of two or more of fumed silica, silica sol, tetraethyl orthosilicate and silicon powder.

[0018] Based on the above technical solution, further, the polycyclic aliphatic amines mentioned in step (2) are one or more of the following: dicyclohexylamine, N,N'-dimethylpiperazine, bicyclo[2.2.1]heptane-2-amine, bicyclo[2.2.2]octane-1-amine, adamantaneamine, and triethylenediamine.

[0019] Based on the above technical solution, further, the mass ratio of the polycyclic aliphatic amine, silicon source and water in step (2) is 1:1 to 5:3 to 15.

[0020] Based on the above technical solution, further, the mass ratio of gel A and gel B in step (3) is 1:2 to 2:1, and the mass percentage of boric acid added is 0.05 to 0.5%.

[0021] Based on the above technical solution, further, the specific process of step (4) is to add the reaction solution obtained in step (3) into the synthesis vessel, stir and crystallize at 120-140℃ for 10-14h, then stir at 150-190℃ for 5-7 days, cool down, filter the obtained mother liquor, wash, and dry to obtain thin-layer Ti-MWW molecular sieve raw powder.

[0022] Based on the above technical solution, further, in step (5), the mass ratio of Ti-MWW molecular sieve raw powder to nitric acid solution is 1:(20-100), the concentration of nitric acid solution is 1-3 mol / L, the calcination temperature is 500-600℃, and the calcination time is 5-12h.

[0023] Secondly, the present invention provides a thin-layered Ti-MWW titanium-silicon molecular sieve prepared by the above-described preparation method.

[0024] Thirdly, the present invention provides the application of the above-mentioned thin-layered Ti-MWW titanium-silicon molecular sieve in epoxidation reactions.

[0025] Based on the above technical solution, the epoxidation reaction is a liquid-phase epoxidation reaction, the substrate of the epoxidation reaction is olefin and hydrogen peroxide, and the solvent includes methanol, ethanol, acetonitrile and dimethylformamide.

[0026] Based on the above technical solution, the olefins further include propylene, butene, pentene, hexene, cyclohexene, and octene.

[0027] Based on the above technical solution, the molar ratio of olefin, hydrogen peroxide and solvent is 1:1 to 2:10 to 50, the reaction temperature is 30 to 100°C, the reaction pressure is 0.1 to 3 MPa, and the reaction time is 0.5 to 5 h.

[0028] The advantages of this invention over the prior art are as follows:

[0029] This invention incorporates polycyclic aliphatic amines into the preparation of Ti-MWW molecular sieves. These amines can inhibit the growth of the C-axis of the molecular sieve during crystallization, resulting in thin-layered Ti-MWW molecular sieves. The synthesized Ti-MWW molecular sieves are particularly suitable for catalyzing the liquid-phase epoxidation of propylene, butene, hexene, cyclohexene, and octene, as well as the oximeation of cyclohexanone. In particular, they exhibit good reactivity in the epoxidation reaction of 1-hexene with hydrogen peroxide, showing very broad application prospects. Attached Figure Description

[0030] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0031] Figure 1 This is a scanning electron microscope image of the conventional Ti-MWW molecular sieve in Comparative Example 1;

[0032] Figure 2 This is a scanning electron microscope image of Ti-MWW molecular sieve catalyst-1 in Example 1. Detailed Implementation

[0033] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0034] The 1-hexene conversion (x(1-Hexene), %) and the 1,2-epoxidehexane selectivity (s(1,2-Epoxidehexane), %) were calculated using Equations (1) and (2).

[0035]

[0036] In the formula: n(1,2-Epoxide hexane) is the amount of 1,2-epoxide hexane, mol; n(Pentanal) is the amount of pentanal, mol; n(1,2-Hexanediol) is the amount of 1,2-hexanediol, mol; n0(1-Hexene) is the initial amount of 1-hexene, mol.

[0037] Comparative Example 1: Traditional Ti-MWW Molecular Sieves

[0038] Synthesis of traditional Ti-MWW molecular sieves: Fumed silica was used as the silicon source, tetrabutyl titanate was used as the titanium source, piperidine was used as the template agent, and boric acid was used as the crystallization aid. The specific feeding and synthesis steps are as follows: First, 11.9 g of piperidine was mixed with 34.2 g of deionized water and stirred until homogeneous. Then, 1.2 g of tetrabutyl titanate solution was slowly added dropwise to the mixture. Finally, 8.2 g of boric acid and 6 g of fumed silica were added and mixed thoroughly to obtain a titanium-silicon gel. The titanium-silicon gel was transferred to a stainless steel static reactor and heated to 170 °C for crystallization for 168 h. After crystallization, the mixture was cooled to room temperature, filtered, dried at 110 °C, and calcined at 540 °C for 6 h to obtain Ti-MWW molecular sieve raw powder. The Ti-MWW molecular sieve raw powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50, treated at 80℃ for 1 day, centrifuged, washed, dried at 80℃ for 12 hours, and calcined in air at 550℃ for 10 hours to finally obtain the Ti-MWW molecular sieve catalyst.

[0039] Figure 1 The image shows a scanning electron microscope (SEM) image of the conventional Ti-MWW molecular sieve in Comparative Example 1.

[0040] Example 1: Ti-MWW molecular sieve catalyst-1

[0041] First, 11.9g piperidine and 17.1g water were mixed and stirred for 30 minutes. Then, 1.2g tetrabutyl titanate was added dropwise and stirred for 2 hours to obtain gel A. Then, 3.64g dicyclohexylamine and 17.1g water were mixed evenly and 6g fumed silica was added. After stirring for 2 hours, gel B was obtained. Then, gel A was slowly added to gel B, and after mixing and stirring for 1 hour, 8.2 g of boric acid was added, and stirring was continued until homogeneous. The stirred solution was then added to a synthesis vessel, and crystallized at 130°C for 12 hours at a speed of 20–100 rpm. The temperature was then raised to 170°C and stirred for 6 days. After cooling, the pressure was released, and the mother liquor was extracted. After filtration, washing, and drying, a thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50, treated at 80°C for 1 day, centrifuged, washed, dried at 80°C for 12 hours, and calcined in air at 550°C for 10 hours to finally obtain Ti-MWW molecular sieve catalyst-1. The molar ratio of SiO2:TiO2:piperidine:B2O3:dicyclohexylamine:H2O was 1.0:0.038:1.2:0.67. : 0.2:19.

[0042] Figure 2 The image shown is a scanning electron microscope (SEM) image of the Ti-MWW molecular sieve catalyst prepared in Example 1, and... Figure 1 Compared with traditional molecular sieve catalysts, the molecular sieve prepared in Example 1 has the advantage that, in electron microscopy images, the molecular sieve can be clearly observed to have a thinner layered structure. The edges of the thinned layered structure are flat and smooth, without obvious uneven thickness or agglomeration.

[0043] Example 2: Ti-MWW molecular sieve catalyst-2

[0044] First, 11.9g piperidine and 17.1g water were mixed and stirred for 30 minutes. Then, 1.2g tetrabutyl titanate was added dropwise and stirred for 2 hours to obtain gel A. Then, 2.3g N,N'-dimethylpiperazine and 17.1g water were mixed evenly and 6g fumed silica was added. After stirring for 2 hours, gel B was obtained. Then, gel A was slowly added to gel B, and after mixing and stirring for 1 hour, 8.2 g of boric acid was added and stirring continued until homogeneous. The stirred liquid was then added to a synthesis vessel and crystallized at 130 °C for 12 hours at a speed of 20–100 rpm. The temperature was then raised to 170 °C and stirred for 6 days. After cooling, the pressure was released and the mother liquor was extracted. After filtration, washing, and drying, a thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50 and treated at 80 °C for 1 day. After centrifugation, washing, drying at 80 °C for 12 hours, and calcination in air at 550 °C for 10 hours, Ti-MWW molecular sieve catalyst-2 was finally obtained.

[0045] Example 3: Ti-MWW molecular sieve catalyst-3

[0046] First, 11.9g piperidine and 17.1g water were mixed and stirred for 30min. Then, 1.2g tetrabutyl titanate was added dropwise and stirred for 2h to obtain gel A. Then, 2.22g bicyclo[2.2.1]heptane-2-amine and 17.1g water were mixed evenly and 6g silicon source was added. After stirring for 2h, gel B was obtained. Then, gel A was slowly added to gel B, and after mixing and stirring for 1 hour, 8.2 g of boric acid was added and stirring was continued until homogeneous. The stirred liquid was then added to a synthesis vessel and stirred and crystallized at 130°C for 12 hours at a speed of 20–100 rpm. The temperature was then raised to 170°C and stirred for 6 days. After cooling, the pressure was released and the mother liquor was extracted. After filtration, washing, and drying, a thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50 and treated at 80°C for 1 day. After centrifugation, washing, drying at 80°C for 12 hours, and calcination in air at 550°C for 10 hours, Ti-MWW molecular sieve catalyst-3 was finally obtained.

[0047] Example 4: Ti-MWW molecular sieve catalyst-4

[0048] First, 11.9 g piperidine and 17.1 g water were mixed and stirred for 30 min. Then, 1.2 g tetrabutyl titanate was added dropwise and stirred for 2 h to obtain gel A. 2.50 g bicyclo[2.2.2]octane-1-amine and 17.1 g water were mixed evenly and then 6 g fumed silica was added and stirred for 2 h to obtain gel B. Then, gel A was slowly added to gel B and stirred for 1 h. Then, 8.2 g boric acid was added and stirred evenly. The stirred solution was added to a synthesis vessel and stirred at 130 °C for 12 h at a speed of 20-100 rpm. Then, the temperature was raised to 170 °C and stirred for 6 days. After cooling, the pressure was released and the mother liquor was extracted. After filtration, washing, and drying, thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve raw powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50 and treated at 80℃ for 1 day. After centrifugation, washing, drying at 80℃ for 12 hours, and calcination in air at 550℃ for 10 hours, the Ti-MWW molecular sieve catalyst-4 was finally obtained.

[0049] Example 5: Ti-MWW molecular sieve catalyst-5

[0050] First, 11.9 g piperidine and 17.1 g water were mixed and stirred for 30 min. Then, 1.2 g tetrabutyl titanate was added dropwise and stirred for 2 h to obtain gel A. 3.02 g adamantane and 17.1 g water were mixed evenly and then 6 g fumed silica was added and stirred for 2 h to obtain gel B. Gel A was then slowly added to gel B and stirred for 1 h. 8.2 g boric acid was then added and stirred evenly. The stirred solution was added to a synthesis vessel and stirred at 130 °C for 12 h at a speed of 20–100 rpm. Then, the temperature was raised to 170 °C and stirred for 6 days. After cooling, the pressure was released and the mother liquor was extracted. After filtration, washing, and drying, thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve raw powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50 and treated at 80℃ for 1 day. After centrifugation, washing, drying at 80℃ for 12 hours, and calcination in air at 550℃ for 10 hours, the Ti-MWW molecular sieve catalyst-5 was finally obtained.

[0051] Example 6: Ti-MWW molecular sieve catalyst-6

[0052] First, 11.9 g piperidine and 17.1 g water were mixed and stirred for 30 min. Then, 1.2 g tetrabutyl titanate was added dropwise and stirred for 2 hours to obtain gel A. 1.82 g dicyclohexylamine and 17.1 g water were mixed evenly and 6 g fumed silica was added. After stirring for 2 hours, gel B was obtained. Then, gel A was slowly added to gel B and stirred for 1 hour. Then, 8.2 g boric acid was added and stirred evenly. The stirred solution was added to a synthesis vessel and stirred at 130 °C for 12 hours at a speed of 20-100 rpm. Then, the temperature was raised to 170 °C and stirred for 6 days. After cooling, the pressure was released and the mother liquor was extracted. After filtration, washing, and drying, thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve raw powder was then mixed with a 2 mol / L nitric acid solution at a mass ratio of 1:50 and treated at 80°C for 1 day. After centrifugation, washing, drying at 80°C for 12 hours, and calcination in air at 550°C for 10 hours, Ti-MWW molecular sieve catalyst-6 was finally obtained.

[0053] Example 7: Ti-MWW molecular sieve catalyst-7

[0054] First, 11.9 g piperidine and 17.1 g water were mixed and stirred for 30 min. Then, 1.2 g tetrabutyl titanate was added dropwise and stirred for 2 h to obtain gel A. 5.47 g dicyclohexylamine and 17.1 g water were mixed evenly and then 6 g fumed silica was added and stirred for 2 h to obtain gel B. Gel A was then slowly added to gel B and stirred for 1 h. 8.2 g boric acid was then added and stirred evenly. The stirred solution was added to a synthesis vessel and stirred at 130 °C for 12 h at a speed of 20–100 rpm. Then, the temperature was raised to 170 °C and stirred for 6 days. After cooling, the pressure was released and the mother liquor was extracted. After filtration, washing, and drying, thin-layer Ti-MWW molecular sieve powder was obtained. The Ti-MWW molecular sieve raw powder was then mixed with 2 mol / L nitric acid solution at a mass ratio of 1:50 and treated at 80℃ for 1 day. After centrifugation, washing, drying at 80℃ for 12 hours, and calcination in air at 550℃ for 15 hours, the Ti-MWW molecular sieve catalyst was finally obtained.

[0055] Example 8:

[0056] The weighed catalyst was placed in a batch reactor with an effective volume of 160 ml, and then acetonitrile, 1-hexene, and hydrogen peroxide were added sequentially. The molar ratio of the materials was n(1-hexene):n(H2O2):n(acetonitrile) = 1:1.05:20, and the amount of catalyst was 10% of the mass fraction of 1-hexene. The reaction was carried out at 500 r / min and 40℃ under normal pressure for 4 h, followed by cooling and centrifugation, and then sampling for analysis. The samples were analyzed using an Agilent 7890A gas chromatograph with an Innowax column, and the product was quantitatively analyzed using the area normalization method.

[0057] Table 1. Results of the liquid-phase epoxidation reaction of 1-hexene with hydrogen peroxide using catalysts from Examples 1-7 and Comparative Example 1.

[0058]

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a thin-layered Ti-MWW titanium-silicon molecular sieve, characterized in that, Includes the following steps: (1) Mix the template agent and water evenly, add the titanium source drop by drop, stir evenly, and obtain gel A; (2) Mix the polycyclic fatty amine and water evenly, add the silicon source, stir evenly, and obtain gel B; (3) Slowly add gel A to gel B, stir evenly, then add boric acid additive and stir evenly; (4) The reaction solution obtained in step (3) is stirred and crystallized at 100-150°C for 5-36 hours, then stirred at 150-210°C for 4-8 days, cooled down, and the resulting mother liquor is filtered, washed, and dried to obtain thin-layer Ti-MWW molecular sieve raw powder. (5) Disperse the Ti-MWW molecular sieve raw powder in a nitric acid solution with a concentration of 1-5 mol / L and treat it at 60-110℃ for 0.5-2 days. Centrifuge, wash, dry, and calcine in air at 400-650℃ for 5-24 hours to obtain Ti-MWW titanium-silicon molecular sieve catalyst.

2. The preparation method according to claim 1, characterized in that, The template agent mentioned in step (1) is one or a combination of two or more of piperidine, cycloheximine, and piperazine; the titanium source is one or a combination of two or more of tetrabutyl titanate, tetraisopropyl titanate, titanium tetrachloride, titanium sulfate, hexafluorotitanic acid, or ammonium hexafluorotitanic acid; the mass ratio of the titanium source, template agent, and water is 1:5 to 10:10 to 20.

3. The preparation method according to claim 1, characterized in that, The silicon source mentioned in step (2) is one or more of the following: fumed silica, silica sol, tetraethyl orthosilicate, and silicon powder; the polycyclic aliphatic amine is one or more of the following: dicyclohexylamine, N,N'-dimethylpiperazine, bicyclo[2.2.1]heptane-2-amine, bicyclo[2.2.2]octane-1-amine, adamantaneamine, and triethylenediamine; the mass ratio of the polycyclic aliphatic amine, silicon source, and water is 1:1 to 5:3 to 15.

4. The preparation method according to claim 1, characterized in that, The mass ratio of gel A and gel B in step (3) is 1:2 to 2:1, and the mass percentage of boric acid added is 0.05 to 0.5%.

5. The preparation method according to claim 1, characterized in that, The specific process of step (4) is to add the reaction solution obtained in step (3) into the synthesis vessel, stir and crystallize at 120-140℃ for 10-14h, then stir at 150-190℃ for 5-7 days, cool down, filter the obtained mother liquor, wash, dry and obtain thin-layer Ti-MWW molecular sieve raw powder.

6. The preparation method according to claim 1, characterized in that, The mass ratio of Ti-MWW molecular sieve raw powder to nitric acid solution in step (5) is 1:(20-100), the concentration of nitric acid solution is 1-3 mol / L, the calcination temperature is 500-600℃, and the calcination time is 5-12h.

7. The thin-layered Ti-MWW titanium-silicon molecular sieve prepared by the preparation method according to any one of claims 1-6.

8. The application of the thin-layered Ti-MWW titanium-silicon molecular sieve according to claim 7 in the epoxidation reaction.

9. The application according to claim 8, characterized in that, The epoxidation reaction is a liquid-phase epoxidation reaction, and the substrates of the epoxidation reaction are olefins and hydrogen peroxide; the solvents include methanol, ethanol, acetonitrile and dimethylformamide; the olefins include propylene, butene, pentene, hexene, cyclohexene and octene.

10. The application according to claim 9, characterized in that, The molar ratio of olefin, hydrogen peroxide and solvent is 1:1 to 2:10 to 50, the reaction temperature is 30 to 100℃, the reaction pressure is 0.1 to 3 MPa, and the reaction time is 0.5 to 5 h.

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