PHMB-assisted synthesis of high external surface area ts-1 molecular sieve and preparation method and application thereof

Abstract

The application belongs to the technical field of catalysts, and discloses a PHMB-assisted-synthesized high-external-surface-area TS-1 molecular sieve and a preparation method and application thereof. The preparation method comprises the following steps: mixing a silicon source, a template agent and water to perform hydrolysis, adding polyhexamethylene biguanide hydrochloride after cooling to obtain a uniform silicon precursor solution; dissolving a titanium source in isopropyl alcohol and adding the solution into the silicon precursor solution to obtain a mixed sol after alcohol removal treatment; then, adding crystal seeds into the mixed sol to perform hydrothermal reaction, and washing, drying and calcining the obtained product to obtain the TS-1 molecular sieve. The application introduces PHMB to assist in hydrothermal crystallization, controls the crystal nucleation and growth process of the molecular sieve, and obtains the TS-1 molecular sieve with large mesopore volume and high external surface area. The obtained molecular sieve as a catalyst exhibits excellent catalytic performance in the cyclohexanone ammoximation reaction, and the conversion rate of cyclohexanone reaches 99.6% and the cyclohexanone oxime yield reaches 93.3%.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a high external surface area TS-1 molecular sieve synthesized with PHMB assistance, its preparation method and application. Background Technology

[0002] TS-1 molecular sieve is a typical MFI-type titanium-silicon molecular sieve, composed of a framework of titanium atoms isomorphously replacing some silicon atoms, exhibiting a regular microporous structure and excellent shape-selective catalytic performance. As an environmentally friendly oxidation catalyst, TS-1 molecular sieve demonstrates good catalytic activity for reactions such as olefin epoxidation, aromatic hydroxylation, and cyclohexanone ammonium oximeation under mild reaction conditions with hydrogen peroxide as the oxidant, and has important application value in the fields of fine chemicals and petrochemicals.

[0003] However, TS-1 molecular sieves prepared by the traditional hydrothermal method are typical MFI-type microporous molecules with a small external surface area. Their specific microporous channel structure and small external surface area make it difficult for reactant molecules to diffuse rapidly to the active sites, and also limit the full exposure of the framework titanium active centers, thus restricting the improvement of the catalytic performance of TS-1 molecular sieves. Therefore, increasing the external surface area and mesopore volume of TS-1 molecular sieves by controlling the synthesis conditions has become an important research direction for improving their mass transfer performance and catalytic efficiency.

[0004] In the hydrothermal synthesis of molecular sieves, surfactants, acting as structure-directing agents or grain growth regulators, significantly influence crystal nucleation, growth, and final morphology. Different types of surfactants, such as polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), and Triton X-100, exhibit different mechanisms of action in regulating the crystal size, intergranular porosity, and external specific surface area of ​​molecular sieves due to their unique molecular structures and interfacial properties. PVP, as a surfactant, can increase the content of framework titanium in the synthesis of TS-1 molecular sieves and reduce the average particle size of TS-1 molecular sieves to 180 nm. However, its effect on increasing the mesopore volume and external specific surface area of ​​TS-1 molecular sieves is limited, and the particle size distribution is relatively wide with poor uniformity. The surfactant Triton X-100 can act as a mesopore template agent to regulate the mesopore structure of TS-1 molecular sieves, but it can only produce small mesopores of 2-3 nm, resulting in insufficient increase in mesopore volume and failing to significantly improve the external specific surface area of ​​TS-1 molecular sieves. While CTAB, as a cationic surfactant, can act as a template agent to induce the formation of specific pore structures in TS-1 molecular sieves and influence the crystal growth rate of TS-1 molecular sieves through electrostatic interactions, thereby controlling the crystal morphology of TS-1 molecular sieves, its effect on grain refinement is not significant, making it difficult to effectively control the grain size of TS-1 molecular sieves at the submicron level. Furthermore, at higher addition levels, the aforementioned surfactants can easily interfere with the orderly assembly of the MFI framework in TS-1 molecular sieves, leading to a decrease in the crystallinity of TS-1 molecular sieves, making it difficult to simultaneously achieve grain refinement and framework integrity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a PHMB-assisted synthesis of a high external surface area TS-1 molecular sieve, its preparation method, and its applications. This invention uses tetraethyl orthosilicate as the silicon source, n-butyl titanate as the titanium source, and tetrapropylammonium hydroxide as the template agent. By introducing polyhexamethylene biguanide hydrochloride (PHMB) to assist hydrothermal crystallization, the nucleation and growth process of the molecular sieve is controlled, resulting in nano-TS-1 molecular sieves with large mesopore volume and high external specific surface area, significantly improving their catalytic performance in the cyclohexanone ammoniation reaction.

[0006] One objective of this invention is to provide a method for preparing high external surface area TS-1 molecules using PHMB-assisted synthesis, comprising the following steps: The silicon source, template agent and water were mixed and hydrolyzed. After cooling, polyhexamethylene biguanide hydrochloride (PHMB) was added and stirred to dissolve, resulting in a homogeneous silicon precursor solution. The titanium source was dissolved in isopropanol and then added to the silicon precursor solution. After alcohol removal treatment, a mixed sol was obtained. Seed crystals were added to the mixed sol to carry out a hydrothermal crystallization reaction. The hydrothermal crystallization reaction product was washed, dried and calcined to obtain TS-1 molecular sieve. The molar ratio of the repeating structural unit of the polyhexamethylene biguanide hydrochloride to the silicon source is 0.0005~0.01.

[0007] When the molar ratio of repeating structural units of polyhexamethylene biguanide hydrochloride to silicon source is less than 0.0005, the number of PHMB molecules is insufficient to form a complete physical barrier covering the crystal nucleus surface, and crystal plane diffusion cannot be effectively limited, resulting in weak or even ineffective crystal refinement and pore-forming effects. When the molar ratio of repeating structural units of polyhexamethylene biguanide hydrochloride to silicon source is greater than 0.01, excessive PHMB molecules will over-coat the crystal nucleus surface, which may not only lead to excessive passivation of the crystal plane and inhibit normal crystal nucleation and growth, but also interfere with TP due to excessive steric hindrance. The orderly assembly of the MFI framework by the AOH structure-directing agent actually leads to a significant decrease in crystallinity. Only when the molar ratio of the repeating structural units of polyhexamethylene biguanide hydrochloride to the silicon source is in the range of 0.0005 to 0.01 can PHMB play its "selective surface regulation" function—forming a sufficiently dense dynamic barrier on the surface of the crystal nucleus to achieve grain refinement and intergranular mesopore creation, while not interfering with the core role of TPAOH in guiding the orderly crystallization of the microporous framework in the bulk phase, thus achieving the optimal balance between grain refinement and framework integrity.

[0008] Furthermore, the temperature for hydrolyzing the silicon source, template agent, and water is 60~80℃, and the hydrolysis time is 3h; wherein, the silicon source is tetraethyl orthosilicate.

[0009] Furthermore, the template agent is tetrapropylammonium hydroxide (TPAOH), and the molar ratio of the template agent to the silicon source is 0.1~0.25.

[0010] Furthermore, the titanium source is tetrabutyl titanate or titanium trichloride, and the molar ratio of the titanium source to the silicon source is 0.01~0.035.

[0011] Further, the seed crystal is a TS-1 molecular sieve obtained by hydrothermal crystallization for 12-48 hours using the above preparation method without adding polyhexamethylene biguanide hydrochloride and titanium source, or a TS-1 molecular sieve obtained by hydrothermal crystallization for 12-48 hours using the above preparation method without adding polyhexamethylene biguanide hydrochloride; the amount of seed crystal added is 0.01-0.5g.

[0012] Furthermore, the hydrothermal reaction temperature is 120~190℃, and the hydrothermal reaction time is 24~96h; when microwave-assisted heating is used for the hydrothermal reaction, the hydrothermal reaction temperature is 120~190℃, and the hydrothermal reaction time is 0.5~4h.

[0013] The second objective of this invention is to provide a high external surface area TS-1 molecular sieve prepared by the above-mentioned preparation method using PHMB-assisted synthesis.

[0014] Furthermore, the external surface area of ​​the TS-1 molecular sieve is 150~250m². 2 / g, mesopore volume is 0.3~0.5cm³ 3 / g.

[0015] The third objective of this invention is to provide an application of the high external surface area TS-1 molecular sieve synthesized with the above-mentioned PHMB-assisted synthesis in the cyclohexanone ammoniation reaction.

[0016] Furthermore, the reaction conditions for the cyclohexanone amination reaction are as follows: tert-butanol as solvent, hydrogen peroxide as oxidant, ammonia water as ammonia source, reaction temperature 70~90℃, and reaction time 1.5~3h.

[0017] Compared with the prior art, the positive and beneficial effects of this invention are as follows: 1. In the initial stage of hydrothermal synthesis, the positive charge carried by polyhexamethylene biguanide hydrochloride (PHMB) interacts with the negatively charged SiO4 through electrostatic interaction. 4- and TiO4 4-The precursor undergoes a condensation reaction, forming amorphous aggregates or primary clusters. Simultaneously, PHMB, as a one-dimensional linear macromolecule, tightly wraps around the crystal nucleus surface via electrostatic attraction, forming a dynamic physical barrier. This barrier effectively limits the diffusion and deposition rate of Si / Ti species onto the crystal face, inhibiting excessive crystal growth and resulting in submicron-sized grains with significantly better uniformity than PVP. Furthermore, after PHMB molecules wrap around the crystal nucleus surface, they occupy interstitial positions between adjacent nanocrystals during crystallization. As grain growth is suppressed, the accumulation of these nanocrystals naturally forms numerous interconnected intercrystalline mesopores, rather than Triton pores. The isolated mesopores of X-100 with a pore size of only 2-3 nm are completely preserved after calcination to remove PHMB. This constructs a hierarchical porous zeolite system composed of intrinsic micropores formed by the TPAOH template and intergranular mesopores induced by PHMB grain size regulation, achieving a significant increase in mesopore volume and external specific surface area. In this process, the molar ratio of repeating structural units of PHMB to silicon source is strictly limited to 0.0005-0.01. Within this molar ratio range, PHMB can precisely exert its "selective surface regulation" effect. Functionally, it forms a sufficiently dense dynamic barrier on the surface of the crystal nucleus to achieve grain refinement and mesopore creation between crystals, while not interfering with the core role of TPAOH in guiding the orderly crystallization of the microporous framework in the bulk phase, thus achieving an optimal balance between grain refinement and framework integrity. In addition, compared with high-cost cationic surfactants such as CTAB, PHMB is a widely used low-cost industrial bactericide with abundant sources, good water solubility, no need for additional compounding of other additives, and no problems such as phase separation or foam interference will occur at the low addition amount of this invention. It is simple to operate and easy to scale up for production. Therefore, by precisely controlling the PHMB / silicon source molar ratio between 0.0005 and 0.01, this invention utilizes the multiple synergistic mechanisms of PHMB electrostatic condensation, crystal nucleus surface confinement, and intergranular pore formation to simultaneously solve the four major technical challenges in the background technology: wide particle size distribution, insufficient mesopore increment, limited external surface area improvement, and crystallinity damage under high addition amounts. Ultimately, a high-performance TS-1 molecular sieve with uniform and fine (submicron) grains, narrow particle size distribution, large mesopore volume, high external specific surface area, and intact MFI framework crystallinity is obtained, achieving a high degree of unity between grain refinement, pore channel optimization, and framework stability.

[0018] 2. The TS-1 molecular sieve prepared by this invention has a significantly reduced crystal size and a significantly increased mesopore volume and external specific surface area, which fully exposes more framework titanium active sites and provides a large number of accessible active centers for the cyclohexanone ammonium oximation reaction. The TS-1 molecular sieve exhibits excellent catalytic performance as a catalyst in the cyclohexanone ammonium oximation reaction, which helps to reduce the amount of catalyst used and energy consumption costs in industrial production. Attached Figure Description

[0019] Figure 1 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the TS-1 molecular sieves obtained in Example 1 and Comparative Example 1 of this invention; wherein, (a) and (c) are the SEM and TEM images of the TS-1 molecular sieve obtained in Comparative Example 1, respectively; and (b) and (d) are the SEM and TEM images of the TS-1 molecular sieve obtained in Example 1, respectively.

[0020] Figure 2 The infrared spectra of the TS-1 molecular sieves obtained in Examples 1-5 and Comparative Example 1 of this invention are shown.

[0021] Figure 3 The N2 adsorption-desorption isotherms and pore size distribution curves of the TS-1 molecular sieves obtained in Examples 1-4 and Comparative Example 1 of this invention are shown; wherein, (a) is the N2 adsorption-desorption isotherm and (b) is the pore size distribution curve. Detailed Implementation

[0022] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0023] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0024] Example 1 A method for preparing high external surface area TS-1 molecular sieves with PHMB-assisted synthesis includes the following steps: (1) Mix tetrapropylammonium hydroxide (TPAOH) solution (25% TPAOH aqueous solution) with deionized water at a molar ratio of 1:133, then slowly add 24g of tetraethyl orthosilicate (TEOS) to ensure that the molar ratio of TPAOH to TEOS is 0.15:1, stir and hydrolyze in a constant temperature water bath at 70℃ for 3h, cool to room temperature, then add 0.058g of polyhexamethylene biguanide hydrochloride to ensure that the molar ratio of the repeating structural unit of polyhexamethylene biguanide hydrochloride to TEOS is 0.0025:1, stir to dissolve, and obtain a uniform silicon precursor solution; (2) Dissolve tetrabutyl titanate (the molar ratio of tetrabutyl titanate to TEOS is 0.03:1) in isopropanol and add it dropwise to the silicon precursor solution obtained in step (1). Remove the alcohol at 80°C for 2 hours to obtain a mixed sol. (3) After the mixed sol cools to room temperature, add 100 mg of seed crystals (the seed crystals are TS-1 molecular sieves obtained by hydrothermal crystallization for 12 h using the preparation method of Comparative Example 1 without PHMB) to obtain a mixed gel. Transfer the mixed gel to a stainless steel reactor with a polytetrafluoroethylene liner and hydrothermally crystallize at 170 °C for 48 h. After hydrothermal crystallization, centrifuge, wash, dry, and calcine at 550 °C for 6 h to obtain TS-1 molecular sieves with high external surface area synthesized with PHMB assistance.

[0025] The TS-1 molecular sieve prepared in this embodiment was used for the ammoniation reaction of cyclohexanone. The reaction apparatus was a 100mL three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirring system. The reaction system used the TS-1 molecular sieve prepared in this embodiment as a catalyst, an 8wt% hydrogen peroxide aqueous solution as an oxidant, 85wt% tert-butanol as a reaction medium, and 25wt% ammonia water as an ammonia source.

[0026] The specific procedure for the cyclohexanone amination reaction is as follows: 3.8 g of cyclohexanone, 11.2 mL of tert-butanol and 25 mg of TS-1 molecular sieve catalyst are added to a round-bottom flask, the temperature is raised to 80 °C, and 17.2 mL of hydrogen peroxide and 8.8 mL of ammonia are added at a constant rate (completed within 75 min). The reaction is then continued at 80 °C with stirring for 105 min.

[0027] The products were analyzed using gas chromatography with internal standard method. Chromatographic conditions: An Agilent 7890B gas chromatograph equipped with an HP-5 capillary column (30m × 0.32mm × 0.25μm) and an FID detector were used; the initial temperature was 60℃ and held for 2 min, then increased to 250℃ at a rate of 10℃ / min. Toluene was used as the internal standard, and the content of each component was quantitatively calculated using the internal standard method.

[0028] The formula for calculating catalytic performance indicators is as follows: Cyclohexanone conversion rate = (mass of cyclohexanone consumed / initial mass of cyclohexanone) × 100% Cyclohexanone oxime yield = (Actual mass of cyclohexanone oxime produced / Theoretical mass of cyclohexanone oxime produced) × 100% The TS-1 molecular sieve prepared in Example 1 was used for the amination of cyclohexanone, with a cyclohexanone conversion rate of 99.6% and a cyclohexanone oxime yield of 93.3%.

[0029] Example 2 The only difference between the preparation method of PHMB-assisted synthesis of high external surface area TS-1 molecular sieve and Example 1 is that the repeating structural unit of polyhexamethylene biguanide hydrochloride in step (1) is added in a molar ratio of 0.001:1 with TEOS.

[0030] The high external surface area TS-1 molecular sieve synthesized with PHMB in this embodiment is used in the same operation method as in Example 1 for the cyclohexanone ammoniation reaction.

[0031] The TS-1 molecular sieve prepared in this embodiment was used for the amination reaction of cyclohexanone, with a cyclohexanone conversion rate of 99.9% and a cyclohexanone oxime yield of 90.0%.

[0032] Example 3 The only difference between the preparation method of PHMB-assisted synthesis of high external surface area TS-1 molecular sieve and Example 1 is that the repeating structural unit of polyhexamethylene biguanide hydrochloride in step (1) is added in a molar ratio of 0.0005:1 with TEOS.

[0033] The high external surface area TS-1 molecular sieve synthesized with PHMB in this embodiment is used in the same operation method as in Example 1 for the cyclohexanone ammoniation reaction.

[0034] The TS-1 molecular sieve prepared in this embodiment was used for the cyclohexanone amination reaction, with a cyclohexanone conversion rate of 97.8% and a cyclohexanone oxime yield of 82.0%.

[0035] Example 4 The only difference between the preparation method of PHMB-assisted synthesis of high external surface area TS-1 molecular sieve and Example 1 is that the repeating structural unit of polyhexamethylene biguanide hydrochloride in step (1) is added in a molar ratio of 0.005:1 with TEOS.

[0036] The high external surface area TS-1 molecular sieve synthesized with PHMB in this embodiment is used in the same operation method as in Example 1 for the cyclohexanone ammoniation reaction.

[0037] The TS-1 molecular sieve prepared in this embodiment was used for the amination of cyclohexanone, with a cyclohexanone conversion rate of 95.6% and a cyclohexanone oxime yield of 89.5%.

[0038] Example 5 The only difference between the preparation method of PHMB-assisted synthesis of high external surface area TS-1 molecular sieve and Example 1 is that the seed crystal in step (3) is the TS-1 molecular sieve obtained by hydrothermal crystallization for 48 hours using the preparation method in Comparative Example 1.

[0039] The high external surface area TS-1 molecular sieve synthesized with PHMB in this embodiment is used in the same operation method as in Example 1 for the cyclohexanone ammoniation reaction.

[0040] The TS-1 molecular sieve prepared in this embodiment was used for the amination of cyclohexanone, with a cyclohexanone conversion rate of 99.1% and a cyclohexanone oxime yield of 92.6%.

[0041] Example 6 The only difference between the PHMB-assisted synthesis method for high external surface area TS-1 molecular sieve and Example 1 is that microwave-assisted heating is used during hydrothermal crystallization, and the hydrothermal crystallization time is 2 hours.

[0042] The high external surface area TS-1 molecular sieve synthesized with PHMB in this embodiment is used in the same operation method as in Example 1 for the cyclohexanone ammoniation reaction.

[0043] The TS-1 molecular sieve prepared in this embodiment was used for the cyclohexanone amination reaction, with a cyclohexanone conversion rate of 93.3% and a cyclohexanone oxime recovery rate of 83.7%.

[0044] Comparative Example 1 The only difference between this comparative example and Example 1 is that polyhexamethylene biguanide hydrochloride is not added in step (1).

[0045] The operation method for the TS-1 molecular sieve prepared in this comparative example to perform the cyclohexanone ammoniation reaction is the same as that in Example 1.

[0046] The TS-1 molecular sieve prepared in this comparative example was used for the amination of cyclohexanone, with a cyclohexanone conversion rate of 69.4% and a cyclohexanone oxime yield of 49.0%.

[0047] The N2 adsorption-desorption performance of the TS-1 molecular sieves prepared in Examples 1-4 and Comparative Example 1 was tested. The specific test results are shown in Table 1. S BET The total specific surface area. S ext Specific surface area S micro The specific surface area of ​​the micropores. V meso For mesoporous pore volume, V micro It refers to the pore volume of micropores.

[0048] Table 1. Test results of N2 adsorption-desorption performance of TS-1 molecular sieves prepared in Examples 1-4 and comparative examples. As can be seen from the data in Table 1, the specific surface area, external specific surface area, and mesopore volume of the TS-1 molecular sieve prepared in Comparative Example 1 without the addition of PHMB are all much smaller than those of the TS-1 molecular sieves prepared in Examples 1-4 with the addition of PHMB. This indicates that the addition of PHMB to the TS-1 precursor solution can regulate the specific surface area, external specific surface area, and mesopore volume. Synthesis of TS-1 molecular sieve mesopores: PHMB-regulated synthesis of TS-1 molecular sieves produced more mesopores, resulting in a larger external specific surface area and mesopore volume.

[0049] The morphology of the TS-1 molecular sieve samples prepared in Example 1 and Comparative Example 1 was tested using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are as follows: Figure 1 As shown. By Figure 1 The results show that the TS-1 molecular sieve synthesized with PHMB assistance in Example 1 has a similar spherical morphology to the TS-1 molecular sieve synthesized without PHMB in Comparative Example 1. However, the former has a more uniform size distribution, with an average particle size of approximately 155 nm. In contrast, the TS-1 molecular sieve synthesized without PHMB in Comparative Example 1 exhibits non-uniform size distribution, with small crystallites measuring approximately 150 nm and large crystallites measuring approximately 480 nm. This demonstrates that the addition of PHMB does not alter the morphology of the TS-1 molecular sieve crystals, but it can regulate the crystal size, resulting in a more uniform TS-1 molecular sieve crystal size.

[0050] The structure of the TS-1 molecular sieve samples prepared in Comparative Example 1 and Examples 1-5 was analyzed using Fourier transform infrared spectroscopy (FT-IR), and the results are as follows: Figure 2 As shown. By Figure 2 As can be seen, compared with Comparative Example 1, the TS-1 molecular sieve synthesized with PHMB in Examples 1-5 still has a typical MFI structure, which can further promote Ti implantation into the molecular sieve framework.

[0051] The pore structure of the TS-1 molecular sieves obtained in Comparative Example 1 and Examples 1-4 was characterized. The pore structure properties of the TS-1 molecular sieve samples prepared in Comparative Example 1 and Examples 1-4 were analyzed using the N2 physical adsorption method, and the results are as follows: Figure 3 As shown. By Figure 3 As can be seen from (a) in the figure, the adsorption-desorption isotherms of the TS-1 molecular sieve samples prepared in Comparative Example 1 and Examples 1-4 are all Type I isotherms, but the relative pressure of the isotherms varies. P / P When 0 > 0.8, the adsorption and desorption lines do not coincide, indicating that micropores and secondary mesopores exist in all TS-1 molecular sieve crystals. Figure 3 As can be seen from (b) in Examples 1-4, the TS-1 molecular sieve synthesized with PHMB assistance has a wider mesopore distribution, with the most probable pore size distributed in the range of 20-70 nm, while the TS-1 molecular sieve synthesized without PHMB assistance in Comparative Example 1 has a significantly smaller most probable pore size.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high external surface area TS-1 molecular sieves using PHMB-assisted synthesis, characterized in that, Includes the following steps: The silicon source, template agent and water are mixed and hydrolyzed. After cooling, polyhexamethylene biguanide hydrochloride is added and dissolved to obtain a homogeneous silicon precursor solution. The titanium source was dissolved in isopropanol and then added to the silicon precursor solution. After alcohol removal, a mixed sol was obtained. Seed crystals were added to the mixed sol to carry out a hydrothermal crystallization reaction. The hydrothermal crystallization reaction product was dried and calcined to obtain TS-1 molecular sieve. The molar ratio of the repeating structural unit of the polyhexamethylene biguanide hydrochloride to the silicon source is 0.0005~0.

01.

2. The method for preparing high external surface area TS-1 molecular sieves with PHMB-assisted synthesis according to claim 1, characterized in that, The silicon source, template agent, and water are hydrolyzed at a temperature of 60-80°C for 3 hours.

3. The method for preparing high external surface area TS-1 molecular sieves with PHMB-assisted synthesis according to claim 1, characterized in that, The template agent is tetrapropylammonium hydroxide, and the molar ratio of the template agent to the silicon source is 0.10~0.

25.

4. The method for preparing high external surface area TS-1 molecular sieves with PHMB-assisted synthesis according to claim 1, characterized in that, The titanium source is tetrabutyl titanate or titanium trichloride, and the molar ratio of the titanium source to the silicon source is 0.010~0.

035.

5. The method for preparing high external surface area TS-1 molecular sieves with PHMB-assisted synthesis according to claim 1, characterized in that, The seed crystal is a TS-1 molecular sieve obtained by hydrothermal crystallization for 12-48 hours using the preparation method described in claim 1 without adding polyhexamethylene biguanide hydrochloride and a titanium source, or a TS-1 molecular sieve obtained by hydrothermal crystallization for 12-48 hours using the preparation method described in claim 1 without adding polyhexamethylene biguanide hydrochloride; the amount of seed crystal added is 0.01-0.5g.

6. The method for preparing high external surface area TS-1 molecular sieves with PHMB-assisted synthesis according to claim 1, characterized in that, The hydrothermal crystallization reaction temperature is 120~190℃, and the hydrothermal crystallization reaction time is 24~96h; when microwave-assisted heating is used for the hydrothermal reaction, the hydrothermal crystallization reaction temperature is 120~190℃, and the hydrothermal crystallization reaction time is 0.5~4h.

7. A TS-1 molecular sieve with high external surface area prepared by the preparation method according to any one of claims 1 to 6 using PHMB-assisted synthesis.

8. The high external surface area TS-1 molecular sieve synthesized with PHMB assistance according to claim 7, characterized in that, The TS-1 molecular sieve has an external surface area of ​​150~250m². 2 / g, mesopore volume is 0.3~0.5cm³ 3 / g.

9. The application of a high external surface area TS-1 molecular sieve synthesized with PHMB assistance as described in claim 8 in the cyclohexanone amination reaction.

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