Ti-Sn-beta molecular sieve as well as preparation method and application thereof
The preparation of Ti-Sn-Beta molecular sieve through transcrystal synthesis and hydrothermal method solves the problems of expensive raw materials and complex synthesis of existing titanium tin molecular sieve materials, and achieves efficient and simple preparation process and excellent catalytic performance.
Patent Information
- Application Number
- CN202510282101.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-11
- Publication Date
- 2025-06-10
AI Technical Summary
The titanium and tin sources of existing titanium tin molecular sieve are expensive, and the synthesis process needs to be carried out under vacuum conditions, which is cumbersome to operate, which is not conducive to industrial application.
Through the transcrystal synthesis method, the MWW type molecular sieve is converted into Beta type molecular sieve, and Ti and Sn are introduced at the same time to prepare Ti-Sn-Beta molecular sieve. The hydrothermal method is used to simplify the synthesis process and reduce the cost of raw materials.
It realizes efficient preparation of Ti-Sn-Beta molecular sieve, which is simple to operate, inexpensive raw materials, and has good catalytic activity. It is suitable for olefins to produce 1,2-diol reaction, and has high conversion and selectivity.
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Figure CN120117622A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of molecular sieve catalysts, and more particularly to a Ti-Sn-beta molecular sieve, a preparation method thereof, and an application thereof. Background Art
[0002] Due to its unique pore structure, special acidic active sites, large specific surface area, high hydrothermal stability, and good hydrophobicity, molecular sieves are currently commonly used heterogeneous catalysts. With the development of synthesis technology, the types of molecular sieves have gradually expanded from traditional pure silicon-type and silicon-aluminum molecular sieves to heteroatom molecular sieves containing various transition metals (such as Ti, Sn, Zr, V, etc.). The introduction of heteroatoms can effectively change the types, strengths, and distributions of the acid centers of molecular sieves, endowing molecular sieves with the ability to catalyze various different chemical reactions. Among them, titanium-silicon molecular sieves represented by TS-1 and Ti-MWW molecular sieves doped with tetracoordinate framework Ti are the most successful industrial heteroatom molecular sieve catalysts today. The reaction system composed of it and hydrogen peroxide (H 2 O 2 ) can highly selectively catalyze important oxidation reactions such as olefin epoxidation, aromatic hydroxylation, and ketone-amine oximation reactions, and the by-product is only water, which conforms to the current advocated concept of green chemistry. Recently, tetracoordinate framework Sn-doped molecular sieves (such as Sn-MFI, Sn-Beta, Sn-MWW, etc.) have been reported to be synthesized and have shown excellent catalytic activity in important reactions such as the hydration of epoxides to 1,2-diols, Bayer-Villiger oxidation, and biomass conversion, attracting extensive attention from researchers.
[0003] 1,2-Diol is widely used in multiple fields, such as cosmetics and personal care, food production, textiles and plastics, pharmaceutical manufacturing, industrial coolants, etc., and has great value in daily life and industrial production. It is an important fine chemical. At present, most of the methods for producing 1,2-diol are multi-step reactions. First, it is necessary to oxidize olefins to generate epoxides, and then generate 1,2-diol by hydration. Based on the respective catalytic abilities of titanium-silicon and tin-silicon molecular sieves, simultaneously incorporating Ti and Sn into the molecular sieve framework can obtain a catalyst that cascades the olefin epoxidation reaction and the hydration of epoxides to 1,2-diol reaction.
[0004] Beta zeolite has a relatively large pore structure. After metal heteroatoms with relatively large atomic radii such as Ti and Sn are incorporated by isomorphous substitution, the influence on its unit cell is relatively small, making it an ideal heteroatom carrier. Currently, Ti- or Sn-containing Beta has been successfully synthesized by various methods. However, the means of simultaneously introducing Ti and Sn into Beta zeolite are still lacking. From the only reported case (Chinese Journal of Catalysis, 2021, 42, 1176–1184), the synthesis process needs to be carried out under vacuum conditions, and the titanium source and tin source used are relatively expensive organometallic raw materials. The overall operation is cumbersome and not conducive to industrial application. Summary of the Invention
[0005] One of the objectives of the present invention is to provide a Ti-Sn-beta zeolite and its preparation method to solve the problems that the raw materials such as titanium source and tin source used in existing titanium-tin zeolites are expensive, the synthesis process needs to be carried out under vacuum conditions, the overall operation is cumbersome, and it is not conducive to industrial application.
[0006] Another objective of the present invention is to provide the application of the above-mentioned Ti-Sn-beta zeolite in directly catalyzing olefins to prepare 1,2-diols in one step.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A Ti-Sn-beta zeolite, and its preparation method includes the following steps: Mix a silicon source, a titanium source, a tin source, seeds, an alkali source, a mineralizer and water to form a synthesis gel; wherein, the molar ratio of the silicon source, the titanium source, the tin source, the alkali source, the mineralizer, and water is 1.0 SiO 2 :0.01-0.04 TiO 2 :0.005-0.02 SnO 2 :0.1-1.0 OH - :0.1-1.0 mineralizer:12.5 H 2 O, and the dosage of the seeds is 5% of the mass of the silicon source calculated as SiO 2 ; Remove water from the obtained synthesis gel until the H 2 O / SiO 2 molar ratio ≤ 1 to form a paste; then hydrothermally crystallize the obtained paste at 140-190 °C. After the crystallization product is filtered, washed, dried, and then calcined, the Ti-Sn-Beta zeolite is obtained.
[0008] Preferably, the molar ratio of the silicon source, the titanium source, the tin source, the alkali source, the mineralizer, and water is 1.0 SiO 2 :0.02-0.04 TiO 2 :0.01 SnO 2: 0.5 - 1.0 OH - : 0.5 - 1.0 Mineralizer: 12.5 H 2 O.
[0009] The silicon source is one or more of deboronated MWW zeolite, deboronated Ti-MWW zeolite, or deboronated Sn-MWW zeolite, and the seed crystal is dealuminated Beta zeolite.
[0010] The silicon source is prepared as follows: Mix the boron-containing MWW or Ti-MWW or Sn-MWW zeolite powder with 2 - 6 mol / L nitric acid, reflux at 60 - 120 °C for 6 - 24 hours for deboronation, then filter, wash, and dry to obtain deboronated MWW zeolite (deB-MWW), deboronated Ti-MWW zeolite (deB-Ti-MWW), and deboronated Sn-MWW zeolite (deB-Sn-MWW) with Si-OH defect sites.
[0011] The seed crystal is prepared as follows: Mix the silica-alumina type H-Beta zeolite powder with concentrated nitric acid, reflux at 60 - 120 °C for 6 - 24 hours for dealumination, then filter, wash, and dry to obtain dealuminated Beta zeolite powder (deAl-Beta); the silica / alumina ratio of the silica-alumina type H-Beta zeolite powder is 10 - 40.
[0012] The titanium source is one or more of titanium tetrachloride, tetrabutyl titanate, tetraethyl titanate, hexafluorotitanic acid, and ammonium hexafluorotitanate.
[0013] The tin source is one or more of tin(IV) chloride pentahydrate, ammonium hexachlorostannate, and dibutyltin diacetate.
[0014] The base source is one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride, and tetraethylammonium fluoride.
[0015] The mineralizer is one or more of hydrogen fluoride, ammonium fluoride, and sodium fluoride.
[0016] The hydrothermal crystallization time is 12 - 96 hours. The crystallization product is filtered and washed until the pH ≈ 7, then placed in an oven at 80 °C for drying, and then calcined at 550 °C for 6 hours after drying.
[0017] The present invention also provides the application of the TiSn-beta molecular sieve in directly and catalytically preparing 1,2-diols from olefins in one step, which includes the following steps: In a batch reactor, 0.1 g of the Ti-Sn-Beta molecular sieve catalyst is mixed with 5 mmol of olefin, 5 mL of acetone, and 5 mmol of hydrogen peroxide with a mass concentration of 30%. The mixture is magnetically stirred at 500 rpm at a temperature of 60 °C for 6 h. The olefin is cyclohexene, 1-hexene, 1-octene, or styrene.
[0018] The present invention uses the conversion crystallization synthesis method to convert the MWW-type molecular sieve into the Beta-type molecular sieve, and at the same time implants Ti and Sn into the Beta molecular sieve framework to obtain the Ti-Sn-Beta molecular sieve. This preparation method is simple to operate, the raw materials used are cheap and easily available, and it has good prospects for industrial promotion and application. The obtained Ti-Sn-Beta molecular sieve catalyst is applied to the reaction of directly hydrating olefins to prepare 1,2-diols, and has excellent catalytic activity. In the reaction of catalyzing the hydration of cyclohexene to prepare 1,2-cyclohexanediol, the conversion rate is as high as over 80%, and the selectivity is as high as over 90%. In the reaction of catalyzing the hydration of 1-octene to prepare 1,2-octanediol, the conversion rate is as high as over 96%, and the selectivity is as high as over 99%. Description of the Drawings
[0019] Figure 1 is the X-ray diffraction pattern of the deB-MWW molecular sieve prepared in Example 1.
[0020] Figure 2 is the X-ray diffraction pattern of the Ti-Sn-Beta molecular sieve prepared in Example 1.
[0021] Figure 3 is the X-ray diffraction pattern of the Ti-Sn-Beta molecular sieve prepared in Example 2.
[0022] Figure 4 is the X-ray diffraction pattern of the Ti-Sn-Beta molecular sieve prepared in Example 3.
[0023] Figure 5 is the transmission electron microscope photograph (a) of the Ti-Sn-Beta molecular sieve prepared in Example 1 and the X-ray energy spectrum analysis surface scan photograph of each element. (b) is the comprehensive diagram of various element surface scans, and (c), (d), (e), and (f) are the surface scan photographs of O, Si, Ti, and Sn respectively.
[0024] Figure 6 is the Sn 3 d X-ray photoelectron spectrum of the Ti-Sn-Beta molecular sieve prepared in Example 1.
[0025] Figure 7is the Ti 2 of the Ti-Sn-Beta molecular sieve prepared in Example 1 p X-ray photoelectron spectroscopy.
[0026] Figure 8 is the X-ray diffraction pattern of the Ti-Sn-Beta molecular sieve prepared in Comparative Example 1
[0027] Figure 9 is the transmission electron microscope photograph of the Ti-Sn-Beta molecular sieve prepared in Comparative Example 1
[0028] Figure 10 is the Sn 3 of the Ti-Sn-Beta molecular sieve prepared in Comparative Example 1 d X-ray photoelectron spectroscopy.
[0029] Figure 11 is the Ti 2 of the Ti-Sn-Beta molecular sieve prepared in Comparative Example 1 p X-ray photoelectron spectroscopy.
[0030] Figure 12 is the X-ray diffraction pattern of the Ti-Sn-Beta molecular sieve prepared in Comparative Example 2
[0031] Figure 13 is the X-ray diffraction pattern of the Ti-Sn-Beta molecular sieve prepared in Comparative Example 3 Detailed implementation mode
[0032] In the following examples, various processes and methods not described in detail are conventional methods well known in the art, and reagents whose sources and specifications are not indicated are commercially available analytical pure or chromatographically pure.
[0033] Synthesis of Ti-MWW molecular sieve: At room temperature, piperidine (calculated as PI), water (calculated as H 2 O), boric acid (calculated as B 2 O 3 ), tetrabutyl titanate (calculated as TiO 2 ), and fumed silica (calculated as SiO 2 ) were mixed evenly to obtain a synthesis gel, and its molar ratio composition was 1.0 SiO 2 : 1.4 PI: 0.67 B 2 O 3 : 0.033 TiO 2 : 25 H 2 O. The synthesis gel was placed in a sealed reaction kettle and aged at 130 °C for 1 day at a rotation rate of 40 revolutions per minute. Then, it was crystallized at 170 °C for 6 days, filtered, washed, and dried to obtain the Ti-MWW molecular sieve raw powder.
[0034] If tetrabutyl titanate is not added in the above synthesis process, the as-synthesized B-MWW zeolite powder can be obtained.
[0035] Example 1: Preparation of Ti-Sn-beta zeolite (1) The as-synthesized B-MWW zeolite powder was refluxed in 2 mol / L nitric acid at 90 °C for 12 h to remove boron, filtered and washed with ultrapure water until pH≈7, and then dried in an oven at 80 °C to obtain deB-MWW zeolite with Si-OH defect sites, which was used as the silicon source.
[0036] (2) The commercially available aluminosilicate H-Beta zeolite powder was refluxed in concentrated nitric acid (mass fraction 65-67%) at 90 °C for 12 h to remove aluminum, filtered and washed with ultrapure water until pH≈7, and then dried in an oven at 80 °C to obtain deAl-Beta zeolite powder, which was used as the seed crystal.
[0037] (3) Using deB-MWW as the silicon source, tetrabutyl titanate as the titanium source, stannic chloride pentahydrate as the tin source, tetraethylammonium hydroxide as the template agent, NH 4 F as the mineralizer, and deAl-Beta as the seed crystal, the silicon source was calculated as SiO 2 the titanium source was calculated as TiO 2 the tin source was calculated as SnO 2 the base, mineralizer, water, and seed crystal were fully mixed to form a synthesis gel. The added deAl-Beta zeolite seed crystal was 5% of the mass of SiO 2 in the silicon source, and the molar ratio of the remaining components was 1.0 SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 1.0 TEAOH: 1.0 NH 4 F: 12.5 H 2 O.
[0038] The obtained synthesis gel was placed in an oven at 80 °C to remove water until H 2 O / SiO 2 ≤1 to form a paste. Finally, the obtained paste was hydrothermally crystallized in an oven at 190 °C for 72 h, filtered and washed with ultrapure water until pH≈7, and then dried in an oven at 80 °C to obtain the as-synthesized TiSn-Beta zeolite powder; the obtained as-synthesized TiSn-Beta zeolite powder was placed in a muffle furnace and calcined at 550 °C for 6 h to obtain Ti-Sn-Beta zeolite.
[0039] The X-ray diffraction pattern of the prepared deB-MWW zeolite is as Figure 1 shown, having a good MWW topological structure. The X-ray diffraction patterns of the Ti-Sn-Beta zeolite were characterized respectively as Figure 2As shown, it has good BEA topology. The transmission electron microscope photograph and the X-ray energy spectrum analysis surface scan of the Ti-Sn-Beta molecular sieve are as Figure 5 shown. Ti and Sn are highly dispersed in the synthesized Beta molecular sieve without obvious aggregation, which conforms to the characteristics of framework Ti and Sn in the molecular sieve. The X-ray photoelectron spectrum of the Ti-Sn-Beta molecular sieve is as Figure 6 the Sn element and Figure 7 the Ti element shown. In this product, Ti and Sn are framework Ti and framework Sn.
[0040] Example 2: Preparation of Ti-Sn-beta molecular sieve In step (3), the molar ratio of each component is 1.0 SiO 2 : 0.04 TiO 2 : 0.01 SnO 2 : 1.0 TEAOH: 0.5NH 4 F: 12.5 H 2 O.
[0041] In step (3), the obtained paste is hydrothermally crystallized in an oven at 190 °C for 96 hours, and the rest are the same as in Example 1. The X-ray diffraction pattern of the prepared Ti-Sn-Beta molecular sieve is as Figure 3 shown, and it has good BEA topology.
[0042] Example 3: Preparation of Ti-Sn-beta molecular sieve In step (3), the molar ratio of each component is 1.0 SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 0.5 TEAOH: 1.0NH 4 F: 12.5 H 2 O.
[0043] In step (3), the deAl-Beta molecular sieve seeds are not added, and the paste is hydrothermally crystallized for 168 hours, and the rest are the same as in Example 1. The X-ray diffraction pattern of the prepared Ti-Sn-Beta molecular sieve is as Figure 4 shown.
[0044] Example 4: Preparation of Ti-Sn-beta molecular sieve The boron-containing Ti-MWW molecular sieve powder was subjected to boron removal by refluxing with 2 mol / L nitric acid at 90 °C for 12 hours, filtered and washed with ultrapure water until the pH was approximately 7, and then dried in an oven at 80 °C to obtain the deB-Ti-MWW molecular sieve with Si-OH defect sites, which was used as the silicon source. The rest was the same as in Example 1.
[0045] Example 5: Preparation of Ti-Sn-beta molecular sieve In step (3), the titanium source was ammonium hexafluorotitanate, the tin source was ammonium hexachlorostannate, the base source was tetraethylammonium fluoride and tetraethylammonium hydroxide, and the mineralizer was sodium fluoride. The molar ratio of each component was 1.0 SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 0.5 TEAF: 0.5 TEAOH: 0.5 NaF: 12.5 H 2 O. The rest was the same as in Example 1.
[0046] Example 6: Preparation of Ti-Sn-beta molecular sieve In step (3), the titanium source was tetraethyl titanate, the tin source was dibutyltin diacetate, the base source was tetraethylammonium bromide and tetraethylammonium hydroxide, and the mineralizer was ammonium fluoride. The molar ratio of each component was 1.0 SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 0.5 TEABr: 0.5 TEAOH: 1.0 NH 4 F: 12.5 H 2 O. The rest was the same as in Example 1.
[0047] Comparative Example 1 The commercially available aluminosilicate H-Beta molecular sieve powder was subjected to dealumination by refluxing with concentrated nitric acid at 90 °C for 12 hours, filtered and washed with ultrapure water until the pH was approximately 7, and then dried in an oven at 80 °C to obtain the deAl-Beta molecular sieve powder with Si-OH defect sites, which was used as the silicon source; Using deAl-Beta as the silicon source, tetrabutyl titanate as the titanium source, tin (IV) chloride pentahydrate as the tin source, and tetraethylammonium hydroxide as the template agent, with the silicon source calculated as SiO 2 calculated as TiO 2 calculated as SnO 2 calculated as, the base, and water were fully mixed to form a synthesis gel. The molar ratio of each component was 1.0 SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 1.0 TEAOH: 1.0 NH 4 F: 12.5H2 O。
[0048] The obtained synthetic gel was placed in an oven at 190 °C for hydrothermal crystallization for 168 hours, filtered and washed with ultrapure water until the pH was approximately 7, and then dried in an oven at 80 °C to obtain the as-synthesized TiSn-Beta zeolite powder; the obtained as-synthesized TiSn-Beta zeolite powder was placed in a muffle furnace and calcined at 550 °C for 6 hours to obtain the Ti-Sn-Beta zeolite.
[0049] The prepared Ti-Sn-Beta zeolite was characterized, and its X-ray diffraction pattern is as Figure 8 shown. The product has a good BEA topological structure; its transmission electron microscope photograph Figure 9 shows that there are a large number of TiO 2 and SnO 2 particles on the surface of the Beta zeolite, which belong to non-framework metal species; its X-ray photoelectron spectrum is as Figure 10 Sn element and Figure 11 Ti element shown. In this product, Ti and Sn are non-framework TiO 2 and SnO 2 .
[0050] Comparative Example 2 The commercially available aluminosilicate H-Beta zeolite powder was refluxed with concentrated nitric acid at 100 °C for 12 hours for dealumination, filtered and washed with ultrapure water until the pH was approximately 7, and then dried in an oven at 80 °C to obtain the deAl-Beta zeolite powder, which was used as the seed for later use; Using the boron-containing MWW zeolite as the silicon source, tetrabutyl titanate as the titanium source, tetraethylammonium hydroxide as the template agent, and NH 4 F as the mineralizing agent, the silicon source was calculated as SiO 2 , the titanium source was calculated as TiO 2 , the base, the mineralizing agent, the seed, and water were fully mixed to form a synthetic gel. The added deAl-Beta zeolite seed was 10% of the mass of SiO 2 , and the molar ratio of the remaining components was 1.0SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 1.0 TEAOH: 1.0 NH 4 F: 12.5 H 2 O.
[0051] The obtained synthetic gel was placed in an oven at 80 °C for water removal until the molar ratio of H 2 O / SiO 2≤ 1 to form a paste. Finally, the obtained paste was hydrothermally crystallized in an oven at 190 °C for 24 hours, filtered and washed with ultrapure water until the pH ≈ 7, and then dried in an oven at 80 °C to obtain the Ti-Sn-Beta molecular sieve precursor powder; the obtained Ti-Sn-Beta molecular sieve precursor powder was placed in a muffle furnace and calcined at 550 °C for 6 hours to obtain the Ti-Sn-Beta molecular sieve.
[0052] The X-ray diffraction pattern of the prepared Ti-Sn-Beta molecular sieve is as Figure 12 shown, and the crystallinity of the obtained product is low.
[0053] Comparative Example 3 Using commercially available aluminosilicate H-Beta as the silicon source, tetrabutyl titanate as the titanium source, and tetraethylammonium hydroxide as the template agent, with the silicon source calculated as SiO 2 and the titanium source calculated as TiO 2 and the base and water were fully mixed to form a synthesis gel. The molar ratio of each component was 1.0 SiO 2 : 0.02 TiO 2 : 0.01 SnO 2 : 1.0 TEAOH: 1.0 NH 4 F: 12.5 H 2 O.
[0054] The obtained synthesis gel was placed in an oven at 190 °C and hydrothermally crystallized for 72 hours, filtered and washed with ultrapure water until the pH ≈ 7, and then dried in an oven at 80 °C to obtain the Ti-Sn-Beta molecular sieve precursor powder; the obtained Ti-Sn-Beta molecular sieve precursor powder was placed in a muffle furnace and calcined at 550 °C for 6 hours to obtain the Ti-Sn-Beta molecular sieve.
[0055] The X-ray diffraction pattern of the prepared Ti-Sn-Beta molecular sieve is as Figure 13 shown, and the product exhibits a symbiotic state of MWW and BEA topological structures.
[0056] The Ti-Sn-Beta molecular sieve catalysts prepared in Examples 1-4 and Comparative Examples 1-3 were used in the catalytic hydration of cyclohexene to 1,2-cyclohexanediol. The steps were as follows: In a batch reactor, 0.1 g of the Ti-Sn-Beta molecular sieve catalyst was mixed with 5 mmol of cyclohexene, 5 mL of acetone, and 5 mmol of 30% mass concentration hydrogen peroxide, and magnetically stirred at 500 rpm at 60 °C for 6 h. Analysis was carried out using gas chromatography (Fuli F80, FID), and the raw material conversion rate and product selectivity data were calculated, as shown in Table 1.
[0057] Table 1 The Ti-Sn-Beta molecular sieve catalysts prepared in Examples 1-4 and Comparative Examples 1-3 were used in the reaction of 1-octene hydration to 1,2-octanediol. The steps were as follows: In a batch reactor, 0.1 g of the Ti-Sn-Beta molecular sieve catalyst was mixed with 5 mmol of 1-octene, 5 mL of acetone, and 5 mmol of 30% hydrogen peroxide by mass concentration, and reacted at 60 °C with magnetic stirring at 500 rpm for 6 h. Analysis was carried out using gas chromatography (Fuli F80, FID), and the raw material conversion rate and product selectivity data were calculated, as shown in Table 2.
[0058] Table 2 The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention, and is not intended to limit the present invention. Any partial changes to the formula and process based on this should be within the protection scope of the present invention.
Claims
1. A Ti-Sn-beta molecular sieve, characterized in that: The preparation method thereof comprises the following steps: The silicon source, titanium source, tin source, seed crystal, alkali source, mineralizer and water are mixed to form a synthetic gel; wherein the molar ratio of the silicon source, titanium source, tin source, alkali source, mineralizer and water is 1.0 SiO2: 0.01-0.04 TiO2: 0.005-0.02 SnO2: 0.1-1.0OH - :0.1-1.0 mineralizer: 12.5 H2O, the amount of seed crystals is 5% of the mass of the silicon source in terms of SiO2; the obtained synthetic gel is dehydrated until the molar ratio of H2O / SiO2 is ≤1 to form a paste; the obtained paste is hydrothermally crystallized at 140-190°C, the crystallized product is filtered, washed, dried, and then roasted to obtain a Ti-Sn-Beta molecular sieve; The silicon source is one or more of deboronized MWW molecular sieve, deboronized Ti-MWW molecular sieve or deboronized Sn-MWW molecular sieve, and the seed crystal is a dealuminated Beta molecular sieve.
2. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The silicon source is prepared according to the following steps: mixing boron-containing MWW or Ti-MWW or Sn-MWW molecular sieve powder with 2-6 mol / L nitric acid, reflux treatment at 60-120° C. for 6-24 hours to remove the boron, and then filtering, washing and drying to obtain a deboronated MWW molecular sieve containing Si-OH defect sites, a deboronated Ti-MWW molecular sieve or a deboronated Sn-MWW molecular sieve.
3. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The seed crystal is prepared according to the following steps: mixing silicon-aluminum type H-Beta molecular sieve powder with concentrated nitric acid, reflux treatment at 60-120° C. for 6-24 hours to dealuminate, and then filtering, washing and drying to obtain dealuminated Beta molecular sieve powder; the silicon-aluminum type H-Beta molecular sieve powder has a silicon / aluminum molar ratio of 10-40.
4. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The titanium source is one or more of titanium tetrachloride, tetrabutyl titanate, tetraethyl titanate, hexafluorotitanic acid, and ammonium hexafluorotitanate.
5. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The tin source is one or more of tin tetrachloride pentahydrate, ammonium hexachlorostannate, and dibutyltin diacetate.
6. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The alkali source is one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride and tetraethylammonium fluoride.
7. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The mineralizer is one or more of hydrogen fluoride, ammonium fluoride and sodium fluoride.
8. The Ti-Sn-beta molecular sieve according to claim 1, characterized in that: The hydrothermal crystallization time is 12-96 hours. The hydrothermal crystallization product is filtered and washed to pH≈7, then placed in an oven at 80°C for drying, and then calcined at 550°C for 6 hours.
9. Use of the Ti-Sn-beta molecular sieve according to any one of claims 1 to 8 to catalyze the preparation of 1,2-diols from olefins.
10. The use according to claim 9, characterized in that: The olefin is cyclohexene, 1-hexene, 1-octene or styrene.