Hierarchical pore TS-1 molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the field of molecular sieve preparation, in particular to a hierarchical pore TS-1 molecular sieve as well as a preparation method and application thereof. According to the preparation method provided by the invention, in the TS-1 molecular sieve synthesis process, a certain amount of silanization reagent is added into a gel system, in the crystallization process, the silanization reagent, a titanium source and a silicon source participate in condensation polymerization together, and a hydrophobic chain segment can form a dynamic micelle structure in the synthesis system; and directionally regulating and controlling pore formation on the outer surface and the peripheral area of the crystal. After post-treatment roasting, organic components in the silanization reagent are removed, so that a hierarchical pore structure is formed in a molecular sieve framework, and the specific surface area of the catalyst and the reactant diffusion efficiency are effectively improved. The catalyst is used for catalyzing olefin epoxidation, the conversion rate of substrate olefin reaches 36.5%, and the selectivity of diol reaches 98%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molecular sieve preparation, and particularly to a hierarchical pore TS-1 molecular sieve, a preparation method and application thereof. BACKGROUND

[0002] Titanium silicalite TS-1 is a kind of microporous material with MFI topological structure, which exhibits excellent activity and selectivity in catalytic oxidation reactions (such as olefin epoxidation, phenol hydroxylation, cyclohexanone ammoximation, etc.). The microporous structure (pore size about 0.55 nm) of TS-1 endows it with high specific surface area and shape-selective catalytic properties, but also leads to serious mass transfer limitations. For large molecule reactants (such as cyclohexanone, phenol derivatives) or bulky intermediates, the microporous channels are difficult to achieve efficient diffusion, resulting in low active site utilization, decreased reaction rate and rapid catalyst deactivation (such as carbon deposition blocking the pores).

[0003] To break through the micropore mass transfer bottleneck, hierarchical pore TS-1 can be constructed by hard template method, post-treatment pore expansion method, seed-directed method, soft template method, etc. Among the above methods, the soft template method is concerned due to its mild pore-forming mechanism and structural adjustability. The soft template dynamically guides the formation of pores during the synthesis process through hydrophobic / hydrophilic interaction, avoiding the harsh post-treatment steps of the hard template method. Among the reagents that can be used as soft templates, silanization reagents (such as long-chain alkyltrimethoxysilane) have both hydrophobic segments and hydrolysable siloxane groups, which can form stable micelles through self-assembly in the hydrothermal system, while directly participating in the polycondensation reaction of the molecular sieve framework. The hydrophobic segment of the silanization reagent guides the formation of mesopores, while the siloxane group co-condenses with the silicon source, ensuring the chemical bonding of the template and the framework and enhancing the structural stability; by adjusting the feeding sequence of the silanization reagent and the titanium source, the aggregation of titanium species is inhibited and the embedding of isolated four-coordinated titanium is promoted; the flexible segment of the silanization reagent forms a three-dimensional interconnected mesoporous network during the crystallization process, significantly improving the mass transfer efficiency.

[0004] However, there are many factors affecting the modification effect of silanization reagents on molecular sieves. Different silanization reagents have different abilities to construct hierarchical pore molecular sieves, and different addition times of silanization reagents will also lead to different mesopore states, and different crystal phases of molecular sieves will also affect the modification effect of silanization reagents. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide a hierarchical pore TS-1 molecular sieve, a preparation method and application thereof. The preparation method provided by the present application can obtain a hierarchical pore TS-1 molecular sieve with high specific surface area, which has high catalytic performance in olefin epoxidation.

[0006] The present application provides a preparation method of a hierarchical pore TS-1 molecular sieve, comprising the following steps:

[0007] S1) The first hydrolysate and the second hydrolysate are mixed to obtain a mixture;

[0008] The first hydrolysate is obtained by first hydrolysis of a silicon source and a template agent;

[0009] The second hydrolysate is obtained by a second hydrolysis of an alcohol, a titanium source, and a template agent;

[0010] S2) Remove alcohol from the mixture obtained in step S1) and add water, then crystallize it with triisopropyloxysilane to obtain a crystallized product;

[0011] S3) The crystallized material obtained in step S2) is calcined to obtain hierarchical porous TS-1 molecular sieve.

[0012] This invention first mixes a first hydrolysate and a second hydrolysate to obtain a mixture; wherein the volume ratio of the first hydrolysate to the second hydrolysate is (2.8~4):1. The first hydrolysate of this invention is obtained by first hydrolysis of a silicon source and a template agent. Specifically, the silicon source and the template agent are mixed, heated, and stirred to perform the first hydrolysis, obtaining the first hydrolysate. The silicon source is tetraethyl orthosilicate; the template agent is one of tetrapropylammonium hydroxide or tetrabutylammonium hydroxide. Using tetrapropylammonium hydroxide and tetrabutylammonium hydroxide as template agents is beneficial for the formation of the MFI topology of titanium-silicon molecular sieves; the volume ratio of the silicon source to the template agent is 1:(1.1~1.2). The temperature of the first hydrolysis in this invention is 35℃~55℃, and the time of the first hydrolysis is 3 h~5 h.

[0013] The second hydrolysate of this invention is obtained by a second hydrolysis of an alcohol, a titanium source, and a template agent. Specifically, the alcohol, titanium source, and template agent are mixed, heated, and stirred to carry out a second hydrolysis, yielding the second hydrolysate. The silicon and titanium sources described in this invention are both hydrophobic and insoluble in water; while the alcohol is a moderately polar molecule that is both hydrophilic and lipophilic. In the alcohol-added system, the solution is a quasi-single-phase sol, where Si and Ti are mixed at the molecular level. The hydrolysis rate of the titanium source is greater than that of the silicon source. The presence of the alcohol significantly reduces water activity, inhibiting the hydrolysis rate of the titanium source. Simultaneously, the alcohol can undergo alcoholysis (Ti–OR exchange) with the Ti centers, forming stable complexes. The hydrolysis-condensation rates of Ti and Si are matched, promoting the formation of Ti–O–Si bonds. The system has a high Ti content and a regular structure.

[0014] The alcohol mentioned in this invention is one of ethanol, isopropanol, and butanol; the titanium source is one of tetraethyl titanate and tetrabutyl titanate; the template agent is the same as described above and will not be repeated; the volume ratio of the titanium source, alcohol, and template agent is 1:(2~4):(8~10). The second hydrolysis temperature in this invention is room temperature, specifically 20℃~30℃, and the second hydrolysis time is 0.5 h~1.5 h.

[0015] After obtaining the mixture, the present invention removes the alcohol and adds water. Specifically, the mixture is heated to 80℃~95℃ to remove the alcohol, followed by the addition of water. In the alcohol-added system, under low water activity, titanium-silicon condensation is slow, the colloidal particle size is small and dispersed, and the system is homogeneous. After "alcohol removal and water addition", hydrolysis and condensation are activated, forming a dense and uniform gel. The crystallization process is effectively guided by the template agent, resulting in small and regular crystals, yielding a perfect MFI framework.

[0016] This invention involves removing alcohol and adding water to the obtained mixture, followed by crystallization with triisopropyloxysilane to obtain a crystallized product. Specifically, after removing alcohol and adding water to the obtained mixture, triisopropyloxysilane is added to the resulting solution for crystallization. The crystallized material is then centrifuged and dried to obtain the crystallized product. The molar ratio of triisopropyloxysilane to the silicon source in step S1) is (0.05~0.3):1. The crystallization temperature is 180℃~210℃, and the crystallization time is 48 h~72 h; the centrifugation time is 40 min~90 min; the drying temperature is 80℃~100℃, and the drying time is 6 h~10 h.

[0017] The triisopropyloxysilane described in this invention is a silanizing agent with a slow-release hydrolysis rate, significant steric hindrance, and framework compatibility. It can synergistically polymerize with the Si-O-Ti network in the sol-gel stage of molecular sieves, possessing a triple function of framework densification, terminal hydroxyl passivation, and mesoporous induction, thereby constructing intercrystalline or interconnected hierarchical porous structures and stabilizing the Ti framework. In constructing TS-1 molecular sieves with high crystallinity, high Ti framework ratio, and controllable hierarchical porous structures, triisopropyloxysilane is the only optimal silanizing agent that can simultaneously achieve framework regulation, surface passivation, and pore structure induction.

[0018] The solution obtained after alcohol removal and water replenishment in this invention is a uniformly dispersed silicon-titanium oxide sol system containing Si-O-Ti network atomic clusters and active precursors with hydroxyl end groups, in the "initial formation of gel network" stage. At this stage, the numerous hydroxyl end groups in the silicon-titanium network have two characteristics: ① the network is not yet dense and has high spatial openness; ② it has strong chemical activity and easily undergoes condensation reactions with other alkoxysilanes. At this time, the slow-release hydrolysis process of the silanizing agent occurs simultaneously with the condensation reaction of the titanium and silicon source residues, allowing newly generated Si-OH to continue participating in network growth. Some of the silicon source in the silanizing agent enters the framework, while the rest participates in condensation on the surface or outer layer of the framework, "passivating" the surface hydroxyl groups of the framework and preventing Ti-OH from polymerizing to form TiO2. This forms a denser, more regular, and hydrophobic Si-O-Ti network while reducing the formation of non-framework Ti. After crystallization is heated to 180℃~210℃, triisopropyloxysilane continues to undergo thermal decomposition and hydrolysis, releasing new Si-OH. At this point, crystal nuclei already exist in the system. Newly added Si sources will preferentially continue to grow on the surface of the crystal nuclei (not re-nucleate), making the grains more regular and slowing down the migration and aggregation of Ti species. This makes the crystallization process more gentle, and finally obtains TS-1 with high crystallinity and a high proportion of Ti in the framework, which is composed of nanocrystals. The micropores are well maintained, and the mesopores are mostly intercrystalline pores and defect-induced mesopores.

[0019] After obtaining the crystallized material, the present invention calcines the crystallized material to obtain a hierarchical porous TS-1 molecular sieve. Specifically, the calcination temperature of the present invention is 450℃~550℃, and the calcination time is 4 h~6 h. More specifically, the calcination atmosphere of the present invention is air; the heating rate of the calcination is 2℃ / min~5℃ / min.

[0020] The preparation method provided by this invention utilizes a hydrothermal method to prepare a hierarchical TS-1 molecular sieve. During the crystallization process, a silanizing agent self-assembles to form micelles or ordered aggregates, which are then embedded into the molecular sieve framework. After calcination to remove the organic portion of the silanizing agent, a hierarchical pore structure with high specific surface area (mesoporous / macroporous / microporous) is formed, which is beneficial for improving mass transfer and catalytic activity, and significantly enhancing catalytic performance.

[0021] This invention also provides a hierarchical porous TS-1 molecular sieve obtained by any of the preparation methods described above. The hierarchical porous TS-1 molecular sieve obtained by this invention is a hierarchical porous TS-1 molecular sieve with a high specific surface area. The hierarchical porous TS-1 molecular sieve obtained by this invention comprises silicon, titanium, and oxygen.

[0022] The present invention also provides a method for olefin epoxidation, comprising the following steps:

[0023] The olefin, hydrogen peroxide, catalyst and solvent are reacted at a temperature of 40℃~100℃ for 1 h~5 h;

[0024] The catalyst is a hierarchical porous TS-1 molecular sieve obtained by any of the preparation methods described above.

[0025] Specifically, hydrogen peroxide, solvent, olefin, and the catalyst are added sequentially to a reaction vessel. The mixture is heated and stirred at 40°C to 100°C for 1 to 5 hours. After the reaction, the catalyst is separated to obtain the olefin epoxidation product. Preferably, the reaction is carried out at 50°C to 70°C for 2 to 4 hours. The stirring rate is 100 rpm to 800 rpm, preferably 300 rpm to 600 rpm. The stirring primarily increases the mixing of the catalyst and reactants, ensuring sufficient contact and promoting the reaction.

[0026] The olefin described in this invention is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and cyclopentene; the solvent is selected from one or more of methanol, acetonitrile, and acetone. The main purpose of the solvent is to mix the organic matter and hydrogen peroxide into one phase to improve mass transfer. The mass ratio of the olefin to the solvent in this invention is 1:(3~9), preferably 1:(5~8); the amount of catalyst added is 0.5%~8% of the mass of the olefin, preferably 2%~6%; the molar ratio of hydrogen peroxide to the olefin is 1:(2~3.5), preferably 1:(2.5~3.5).

[0027] This invention provides a hierarchical porous TS-1 molecular sieve, its preparation method, and its applications. The preparation method involves adding a certain amount of silanizing agent to the gel system during the synthesis of the TS-1 molecular sieve. During crystallization, the silanizing agent, along with titanium and silicon sources, participates in the polycondensation reaction. Its hydrophobic segments can form a dynamic micelle structure in the synthesis system, directionally regulating the formation of pores on the outer surface of the crystal and its surrounding areas. After post-treatment calcination, the organic components in the silanizing agent are removed, thereby forming a hierarchical porous structure in the molecular sieve framework, effectively improving the specific surface area of ​​the catalyst and the diffusion efficiency of reactants. The catalyst is used to catalyze the epoxidation of olefins, achieving a substrate olefin conversion rate of 36.5% and a diol selectivity of 98%. Attached Figure Description

[0028] Figure 1 This is a pore size distribution diagram of TS-1 molecular sieve;

[0029] Figure 2 This is a pore size distribution diagram of TS-1-4 molecular sieve. Detailed Implementation

[0030] This invention discloses a hierarchical porous TS-1 molecular sieve, its preparation method, and its applications. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0031] The present invention will be further described below with reference to the embodiments:

[0032] Example 1

[0033] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 22.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 35 °C for 3 h to form solution ①. 1.0 mL of tetrabutyl titanate, 2 mL of ethanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 0.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing the alcohol at 90 °C and adding water, solution ④ was formed. Solution ④ was transferred to a crystallization vessel and crystallized at 180 °C for 48 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 80 °C for 6 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 450 °C for 4 h to obtain TS-1 molecular sieve, denoted as TS-1.

[0034] Example 2

[0035] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 22.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 35 °C for 3 h to form solution ①. 1.0 mL of tetrabutyl titanate, 2 mL of ethanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 0.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 0.71 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 180 °C for 48 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 80 °C for 6 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 450 °C for 4 h to obtain TS-1 molecular sieve, denoted as TS-1-1.

[0036] Example 3

[0037] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 24.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 55 °C for 5 h to form solution ①. 1.0 mL of tetrabutyl titanate, 4 mL of isopropanol, and 10.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 1.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 1.41 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 210 °C for 72 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 5 °C / min to 550 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-2.

[0038] Example 4

[0039] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 22.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 55 °C for 3 h to form solution ①. 1.0 mL of tetrabutyl titanate, 4 mL of isopropanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 1.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 2.83 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 180 °C for 72 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 2 °C / min to 550 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-3.

[0040] Example 5

[0041] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 22.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 50 °C for 4 h to form solution ①. 1.0 mL of tetrabutyl titanate, 4 mL of butanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 0.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 3.54 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 180 °C for 48 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 5 °C / min to 550 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-4.

[0042] Example 6

[0043] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 24.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 45 °C for 4 h to form solution ①. 1.0 mL of tetrabutyl titanate, 3 mL of isopropanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 0.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 4.24 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 210 °C for 48 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 5 °C / min to 500 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-5.

[0044] Example 7

[0045] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 24.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 50 °C for 3 h to form solution ①. 1.0 mL of tetrabutyl titanate, 4 mL of butanol solution, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 1.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 3.54 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 180 °C for 72 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 5 °C / min to 550 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-6.

[0046] Example 8

[0047] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 24.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 50 °C for 5 h to form solution ①. 1.0 mL of tetrabutyl titanate, 2 mL of isopropanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 0.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 2.83 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 180 °C for 48 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 4 °C / min to 550 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-7.

[0048] Example 9

[0049] Preparation of titanium-silicon molecular sieves: 20.0 mL of tetraethyl orthosilicate and 24.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at 50 °C for 5 h to form solution ①. 1.0 mL of tetrabutyl titanate, 2 mL of isopropanol, and 8.0 mL of tetrapropylammonium hydroxide were mixed evenly and stirred at room temperature for 0.5 h to form solution ②. Solution ① was mixed with solution ② to form solution ③. After removing alcohol and adding water at 90 °C, solution ④ was formed. 2.83 g of triisopropyloxysilane was added to solution ④ and stirred evenly to form solution ⑤. Solution ⑤ was transferred to a crystallization vessel and crystallized at 180 °C for 72 h. After crystallization, the molecular sieve was separated by centrifugation, dried at 100 °C for 10 h, and then calcined in a muffle furnace at a heating rate of 1 °C / min to 550 °C for 6 h to obtain TS-1 molecular sieve, denoted as TS-1-8.

[0050] Application Example 1

[0051] 6.4 g butene, 16.8 g methanol, 15.2 g acetonitrile, and 5.65 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor. 0.128 g of TS-1-1 catalyst was added, and the mixture was stirred at 300 rpm at 60 °C for 2 h. Quantitative analysis after centrifugation showed an olefin conversion of 30.6% and a target product selectivity of 95%.

[0052] Application Example 2

[0053] 6.4 g pentene, 16.8 g methanol, 15.2 g acetonitrile, and 4.52 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor. 0.128 g TS-1-2 catalyst was added, and the mixture was stirred at 300 rpm at 50 °C for 2 h. After centrifugation, quantitative analysis showed an olefin conversion of 26.5% and a target product selectivity of 97%.

[0054] Application Example 3

[0055] 6.4 g of pentene, 32 g of methanol, and 3.23 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor, along with 0.384 g of TS-1-3 catalyst. The mixture was stirred at 600 rpm and reacted at 50 °C for 2 h. After centrifugation, quantitative analysis showed that the olefin conversion rate was 24.7% and the selectivity for the target product was 98%.

[0056] Application Example 4

[0057] 6.4 g pentene, 16.8 g methanol, 15.2 g acetonitrile, and 4.52 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor. 0.128 g TS-1-4 catalyst was added, and the mixture was stirred at 300 rpm and reacted at 60 °C for 2 h. Quantitative analysis after centrifugation showed an olefin conversion of 36.5% and a target product selectivity of 98%.

[0058] Application Example 5

[0059] 6.4 g hexene, 32 g acetone, and 3.76 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor, along with 0.32 g TS-1-5 catalyst. The mixture was stirred at 500 rpm and reacted at 70 °C for 2 h. After centrifugation, quantitative analysis showed that the olefin conversion rate was 27.5% and the selectivity for the target product was 99%.

[0060] Application Example 6

[0061] 6.4 g heptaene, 32 g acetone, and 3.23 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor, along with 0.32 g of TS-1-6 catalyst. The mixture was stirred at 300 rpm and reacted at 70 °C for 4 h. After centrifugation, quantitative analysis showed that the olefin conversion rate was 24.3% and the selectivity for the target product was 99%.

[0062] Application Example 7

[0063] 6.4 g heptaene, 32 g methanol, and 3.23 g of 27.5% hydrogen peroxide aqueous solution were added to a 100 mL reactor, along with 0.32 g of TS-1-7 catalyst. The mixture was stirred at 300 rpm and reacted at 60 °C for 2 h. After centrifugation, quantitative analysis showed that the olefin conversion rate was 28.1% and the selectivity for the target product was 96%.

[0064] Application Example 8

[0065] 6.4 g octene, 32 g acetone, and 2.82 g of 27.5% hydrogen peroxide aqueous solution were added to a 100 mL reactor, along with 0.32 g TS-1-8 catalyst. The mixture was stirred at 300 rpm and reacted at 70 °C for 2 h. After centrifugation, quantitative analysis showed that the olefin conversion rate was 18.7%, and the diol selectivity of the final product was 99%.

[0066] Application Comparative Example 1

[0067] 6.4 g butene, 16.8 g methanol, 15.2 g acetonitrile, and 5.65 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor. 0.128 g of TS-1 molecular sieve catalyst was then added. The mixture was stirred at 300 rpm and reacted at 60 °C for 2 h. Quantitative analysis after centrifugation showed an olefin conversion rate of 26.5% and a target product selectivity of 94%.

[0068] Application Comparative Example 2

[0069] 6.4 g pentene, 16.8 g methanol, 15.2 g acetonitrile, and 4.52 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor. 0.128 g TS-1 molecular sieve catalyst was then added. The mixture was stirred at 300 rpm and reacted at 60 °C for 2 h. Quantitative analysis after centrifugation showed an olefin conversion of 30.4% and a target product selectivity of 97%.

[0070] Application Comparative Example 3

[0071] 6.4 g of hexene, 32 g of acetone, and 3.76 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor. 0.32 g of TS-1 molecular sieve catalyst was then added. The mixture was stirred at 500 rpm and reacted at 70 °C for 2 h. Quantitative analysis was performed after centrifugation, revealing an olefin conversion rate of 20.5% and a target product selectivity of 99%.

[0072] Application Comparative Example 4

[0073] 6.4 g heptaene, 32 g acetone, and 3.23 g of 27.5% hydrogen peroxide aqueous solution were added to a 250 mL reactor, along with 0.32 g of TS-1 molecular sieve catalyst. The mixture was stirred at 300 rpm and reacted at 70 °C for 4 h. After centrifugation, quantitative analysis was performed, revealing an olefin conversion rate of 21.6% and a target product selectivity of 99%.

[0074] Application Comparative Example 5

[0075] 6.4 g heptaene, 32 g methanol, and 3.23 g of 27.5% hydrogen peroxide aqueous solution were added to a 100 mL reactor, along with 0.32 g of hierarchical porous TS-1 molecular sieve catalyst. The mixture was stirred at 300 rpm and reacted at 60 °C for 2 h. After centrifugation, quantitative analysis showed that the olefin conversion rate was 23.4% and the selectivity for the target product was 92%.

[0076] The parameters and results of Application Examples 1-8 and Comparative Example 5 are summarized in Table 1:

[0077] Table 1

[0078]

[0079] The above performance data show that, under the same or similar conditions, the TS-1 molecular sieve synthesized with the addition of a silanizing agent has a much better catalytic performance in olefin epoxidation than the TS-1 synthesized without the addition of a silanizing agent.

[0080] Comparative Example 1

[0081] To compare the effect of using ethanol as a solvent in the preparation of solution ②, the method of Example 4 was followed, except that ethanol was replaced with water, while everything else remained the same, to obtain a molecular sieve, denoted as TS-1-BC-1.

[0082] Comparative Example 2

[0083] To compare the effect of the silanizing reagent addition steps, the order of addition of the silanizing reagent was adjusted. Following the method of Example 4, the only difference was that triisopropyloxysilane was added to solution ③ instead of solution ④; all other steps remained the same. The resulting molecular sieve was named TS-1-BC-2.

[0084] Comparative Example 3

[0085] To further compare the effects of the silanizing reagent addition steps, the order of addition of the silanizing reagent was adjusted again. Following the method of Example 4, the only difference was that triisopropyloxysilane was added to the crystallized solution instead of solution ④; all other steps remained the same, resulting in a molecular sieve named TS-1-BC-3.

[0086] Application Comparison 6~8

[0087] The molecular sieves obtained in Comparative Examples 1-3 were evaluated as catalysts under the reaction conditions of Application Example 4, and were designated as Comparative Examples 6-8. The parameters and results of Comparative Examples 6-8 are summarized in Table 2, and the parameters and results of Application Example 4 are also summarized in Table 2 for comparison.

[0088] Table 2

[0089]

[0090] Supplementary experiments revealed that the role of ethanol added during solution preparation ② is irreplaceable. This is because both silicon and titanium sources are hydrophobic and insoluble in water, while alcohols are moderately polar molecules that are both hydrophilic and lipophilic. In the alcohol-added system, the solution is a quasi-single-phase sol, with Si and Ti mixed at the molecular level. Furthermore, by adjusting the timing of silanizing agent addition, it was found that adding the silanizing agent to solution ④ after alcohol removal resulted in a better catalytic effect than adding it to solution ③ or the crystallized solution. This is because the solution after alcohol removal has already formed a certain structure, and adding the silanizing agent at this point avoids excessive or side reactions caused by premature addition, thus helping to improve the structural stability and uniformity of the catalyst.

[0091] The BET specific surface area and pore size distribution of TS-1 and TS-1-4 molecular sieves under nitrogen adsorption-desorption were tested. The BET specific surface area results are shown in Table 3, and the pore size distribution results are shown in Table 4. Figure 1 and Figure 2 As shown, Figure 1 This is a pore size distribution diagram of TS-1 molecular sieve. Figure 2 This is a pore size distribution diagram of TS-1-4 molecular sieve.

[0092] Table 3

[0093]

[0094] Table 3 shows that the BET specific surface area of ​​TS-1-4 is much higher than that of TS-1. Figure 1 and Figure 2 The results show that TS-1-4 contains a hierarchical pore structure of micropores, mesopores, and macropores, while TS-1 mainly has small mesopores. This indicates that the silanizing agent induces the formation of a hierarchical pore structure, which is beneficial to the mass transfer process during the reaction and thus enhances the catalytic performance of the molecular sieve.

[0095] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a hierarchical-pore TS-1 molecular sieve, characterized in that, The method comprises the following steps: S1) mixing a first hydrolysate and a second hydrolysate to obtain a mixed solution; The first hydrolysate is obtained by first hydrolysis of a silicon source and a template agent; The second hydrolysate is obtained by second hydrolysis of an alcohol, a titanium source and a template agent; S2) removing alcohol from the mixed solution obtained in step S1) and supplementing water, and then crystallizing with triisopropylsilyl to obtain a crystalline product; S3) calcining the crystalline product obtained in step S2) to obtain a hierarchical TS-1 molecular sieve.

2. The production method according to claim 1, characterized by, In step S2), the molar ratio of triisopropylsilyl to the silicon source in step S1) is (0.05-0.3):

1.

3. The preparation method according to claim 1, characterized in that, In step S1), the alcohol is one of ethanol, isopropanol and butanol; The silicon source is tetraethyl orthosilicate; The template agent is one of tetrapropylammonium hydroxide or tetrabutylammonium hydroxide; The titanium source is one of tetraethyl titanate and tetrabutyl titanate.

4. The method of claim 1, wherein, In step S1), the volume ratio of the silicon source to the template agent is 1:(1.1-1.2); The volume ratio of the titanium source, the alcohol and the template agent is 1:(2-4):(8-10); The volume ratio of the first hydrolysate to the second hydrolysate is (2.8-4):

1.

5. The preparation method according to claim 1, characterized in that, In step S1), the temperature of the first hydrolysis is 35-55°C, and the time of the first hydrolysis is 3-5 h; The temperature of the second hydrolysis is room temperature, and the time of the second hydrolysis is 0.5-1.5 h.

6. The method of claim 1, wherein, In step S2), the temperature of the crystallization is 180-210°C, and the time of the crystallization is 48-72 h; The temperature of the calcination is 450-550°C, and the time of the calcination is 4-6 h.

7. The hierarchical TS-1 molecular sieve obtained by the preparation method in any one of claims 1-6.

8. A process for the epoxidation of an olefin, characterized in that, The method comprises the following steps: The olefin, hydrogen peroxide, catalyst and solvent are reacted at a temperature of 40-100°C for 1-5 h; The catalyst is the hierarchical TS-1 molecular sieve obtained by the preparation method in any one of claims 1-6.

9. The process for the epoxidation of an olefin according to claim 8, characterized in that, The olefin is selected from one or more of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and cyclopentene; The solvent is selected from one or more of methanol, acetonitrile and acetone.

10. The process for the epoxidation of an olefin according to claim 8, characterized in that, The mass ratio of the olefin to the solvent is 1:(3-9); The amount of the catalyst added is 0.5%-8% of the mass of the olefin; The molar ratio of the hydrogen peroxide to the olefin is 1:(2-3.5).

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