Isomorphous substituted titanium silicalite molecular sieve as well as preparation method and application thereof
By using ammonium fluoride organic solution to expand pores and reacting with a titanium source, isomorphously substituted titanium-silicon molecular sieves were prepared, solving the problems of pore structure regulation and active center construction in traditional methods, and achieving highly efficient macromolecular catalytic performance.
Patent Information
- Application Number
- CN202610284673.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-10
- Publication Date
- 2026-05-15
AI Technical Summary
The microporous channel structure of traditional titanium-silicon molecular sieves restricts the diffusion of macromolecular reactants, and existing pore-expansion modification methods are difficult to simultaneously achieve pore structure regulation, active center construction, and catalytic performance improvement.
A pure silicon layered precursor was expanded by using an ammonium fluoride organic solution, then dispersed in ethanol, a titanium source was added for reaction and calcination, and isomorphously substituted titanium-silicon molecular sieves were prepared. This avoided the damage to the framework caused by strong acid and high temperature conditions and precisely constructed the framework titanium active centers.
The prepared titanium-silicon molecular sieve exhibits superior catalytic performance and lifespan, making it suitable for macromolecular catalytic reactions with significantly improved catalytic activity.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of molecular sieve preparation technology, and in particular to an isomorphously substituted titanium-silicon molecular sieve, its preparation method, and its application. Background Technology
[0002] Titanium silicate molecular sieves, as a class of porous materials with catalytic properties, have demonstrated excellent catalytic effects in selective oxidation reactions such as olefin epoxidation and ketone ammonium oximation, becoming a research and application hotspot in the field of catalytic materials. However, traditional titanium silicate molecular sieves are limited by their microporous channel structure, making it difficult for large molecular reactants to diffuse to the active sites, which severely restricts their application in macromolecular catalytic reactions. Therefore, the development of titanium silicate molecular sieves with large pore size and high activity has become an important development direction in this field.
[0003] To address the issue of limited pore size in titanium-silicon molecular sieves, researchers have developed various post-treatment methods for pore expansion and modification. They have also attempted to introduce titanium active centers during the pore expansion process, mainly categorized into two types: silanization pillar-supported pore expansion and one-step fluoride modification. However, existing methods are insufficient to simultaneously meet the needs of pore structure regulation, active center construction, and catalytic performance enhancement.
[0004] Silanization pillaring is a common method for pore-expanding modification of layered silicate materials. By modifying the interlayer of layered silicate precursors with silanizing agents, materials with expanded interlayer pores can be prepared, increasing the pore size to a certain extent. However, this method usually requires strong acid media and high temperature conditions. The harsh reaction conditions can easily damage the layered framework structure of the material, or even cause the framework to collapse. In addition, silanizing agents have problems such as cumbersome operation procedures and poor safety, making it difficult to achieve precise control of the pore structure.
[0005] The one-step preparation of titanium-silicon molecular sieves using fluorides is a recently developed method for post-processing layered silicates. It employs an aqueous solution of hexafluorotitanic acid (H₂TiF₆) to treat the layered precursor in a "one-step" manner, simultaneously achieving etching and pore-expansion of the molecular sieve and isomorphous substitution of titanium. However, the hydrolysis of hexafluorotitanic acid produces hydrofluoric acid (HF), which has a severe and uneven etching effect on the molecular sieve layers, easily forming irregular channels. Furthermore, the one-step preparation process easily leads to the formation of non-framework titanium, resulting in a relatively low proportion of framework titanium active centers and low catalytic activity of the catalyst.
[0006] Therefore, it is of great significance to develop a titanium-silicon molecular sieve with mild conditions, controllable steps, precise construction of active centers, and applicability to various layered precursors, as well as its preparation method. Summary of the Invention
[0007] The purpose of this invention is to provide a isomorphously substituted titanium-silicon molecular sieve, its preparation method, and its application, so as to solve the problem of low reactivity of titanium-silicon molecular sieves prepared by one-step method in the prior art.
[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing isomorphously substituted titanium-silicon molecular sieves, comprising the following steps: (1) A pore-expanding material is obtained by mixing a pure silicon layered precursor with an ammonium fluoride organic solution and reacting the mixture. (2) Disperse the pore-expanding material in ethanol, add a titanium source for reaction, drying and calcination to obtain isomorphous substituted titanium silicon molecular sieve.
[0009] Preferably, in step (1), the pure silicon layered precursor includes PLS-3, PLS-4, MCM-47 or RUB-39.
[0010] Preferably, in step (1), the concentration of ammonium fluoride in the ammonium fluoride organic solution is 10~20wt%, wherein the solvent in the ammonium fluoride organic solution includes one or more of methanol, ethanol, ethylene glycol and ethyl acetate; and the mass-volume ratio of the pure silicon layered precursor to the ammonium fluoride organic solution is 1g:40~60mL.
[0011] Preferably, in step (1), the reaction temperature is 30~60℃ and the time is 4~10h.
[0012] Preferably, in step (2), the molar ratio of silicon in the pore-expanding material to titanium in the titanium source is 30~100:1.
[0013] Preferably, in step (2), the roasting temperature is 500~600℃ and the time is 4~6h.
[0014] This invention provides a method for preparing isomorphously substituted titanium-silicon molecular sieves as described above, resulting in isomorphously substituted titanium-silicon molecular sieves.
[0015] This invention provides an application of the isomorphously substituted titanium-silicon molecular sieve described above as a catalyst in the epoxidation reaction of olefins.
[0016] Preferably, the process includes the following steps: mixing olefins, hydrogen peroxide, titanium silicate molecular sieves and solvents and then carrying out an epoxidation reaction.
[0017] Preferably, the molar mass ratio of the olefin and the titanium-silicon molecular sieve is 1 mmol: 2~3 mg.
[0018] The beneficial effects of this invention are: This invention uses an ammonium fluoride organic solution to expand the pores of a pure silicon layered precursor. Compared with the traditional ammonium fluoride aqueous solution, this avoids structural damage to the layered precursor and helps maintain the integrity of the molecular sieve framework.
[0019] This invention disperses the pore-expanding material in ethanol and then adds a titanium source to react, which inhibits the formation of non-framework titanium and is conducive to the formation of more framework titanium active centers.
[0020] Compared to the one-step method of preparing titanium-silicon molecular sieves using aqueous fluorotitanic acid, the preparation method provided by this invention is more controllable, and the prepared titanium-silicon molecular sieves have better catalytic performance and longer service life. Detailed Implementation
[0021] This invention provides a method for preparing isomorphously substituted titanium-silicon molecular sieves, comprising the following steps: (1) A pore-expanding material is obtained by mixing a pure silicon layered precursor with an ammonium fluoride organic solution and reacting the mixture. (2) Disperse the pore-expanding material in ethanol, add a titanium source for reaction, drying and calcination to obtain isomorphous substituted titanium silicon molecular sieve.
[0022] In this invention, in step (1), the pure silicon layered precursor includes PLS-3, PLS-4, MCM-47 or RUB-39.
[0023] In this embodiment of the invention, PLS-3 is used as a precursor to prepare isomorphously substituted titanium-silicon molecular sieves. The preparation method of PLS-3 is as follows: first, NaOH is dissolved in TEAOH aqueous solution, then silicon source H-kanemite is added, and the mixture is stirred at room temperature for 30 min. Then, the reactants are transferred to a polytetrafluoroethylene reactor with a stainless steel jacket for reaction. The molar ratio of reactants is 1.0 SiO2 : 0.2 TEAOH. + The crystallization conditions were: 0.04 NaOH : 6.5 H2O, temperature 170℃, static reaction for 1 day, the product was collected by centrifugation, washed with a large amount of deionized water, and finally dried to contain 20~30 mmol / g of water.
[0024] In this invention, in step (1), the concentration of ammonium fluoride in the ammonium fluoride organic solution is 10~20wt%, specifically 10wt%, 12wt%, 14wt%, 18wt%, or 20wt%; wherein the solvent in the ammonium fluoride organic solution includes one or more of methanol, ethanol, ethylene glycol, and ethyl acetate; the mass-volume ratio of the pure silicon layered precursor to the ammonium fluoride organic solution is 1g:40~60mL, specifically 1g:40mL, 1g:50mL, or 1g:60mL.
[0025] In this invention, in step (1), the reaction temperature is 30~60℃, specifically 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃; the time is 4~10h, specifically 4h, 5h, 6h, 7h, 8h, 9h, 10h.
[0026] In this invention, in step (2), the molar ratio of silicon in the pore-expanding material to titanium in the titanium source is 30~100:1, specifically 30:1, 40:1, 50:1, 60:1, 70:1, or 80:1.
[0027] In this invention, in step (2), the roasting temperature is 500~600℃, specifically 500℃, 520℃, 550℃, 580℃, 600℃; the time is 4~6h, specifically 4h, 4.5h, 5h, 5.5h, 6h.
[0028] This invention provides a method for preparing isomorphously substituted titanium-silicon molecular sieves as described above, resulting in isomorphously substituted titanium-silicon molecular sieves.
[0029] This invention provides an application of the isomorphously substituted titanium-silicon molecular sieve described above as a catalyst in the epoxidation reaction of olefins.
[0030] The present invention includes the following steps: mixing olefins, hydrogen peroxide, titanium silicon molecular sieves and solvents and then carrying out an epoxidation reaction.
[0031] In this invention, the molar mass ratio of the olefin and the titanium-silicon molecular sieve is 1 mmol: 2~3 mg, specifically 1 mmol: 2 mg or 1 mmol: 3 mg.
[0032] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0033] Example 1
[0034] Weigh 1.0 g of pure silicon layered precursor PLS-3 (water content 25 mmol / g) and add it to 50 mL of a 15 wt% ammonium fluoride / methanol solution. In a polytetrafluoroethylene beaker, stir and react at 50 °C for 6 h. After the reaction is complete, centrifuge to separate the solid, wash three times with methanol, then wash with water until neutral, and dry at 80 °C for 6 h to obtain the pore-expanding material, denoted as Pore-Expanding Material-1.
[0035] 0.5 g of the above-mentioned pore-expanding material-1 was dispersed in 25 mL of anhydrous ethanol and sonicated for 10 min to achieve uniform dispersion. Under nitrogen protection and vigorous stirring, tetraethyl titanate was slowly added dropwise using a microsyringe (controlling the Si / Ti ratio in the titanium-silicon molecular sieve to 35). After the addition was complete, the mixture was refluxed and stirred in an oil bath at 60 °C for 6 h. After the reaction was complete, the solid was collected by centrifugation, washed three times with ethanol, and dried overnight at 80 °C. Finally, the dried product was heated to 550 °C in a muffle furnace at a heating rate of 2 °C / min and calcined in air for 5 h to obtain isomorphously substituted titanium-silicon molecular sieve, denoted as titanium-silicon molecular sieve-1.
[0036] Example 2
[0037] Weigh 1.0 g of pure silicon layered precursor PLS-3 (water content 30 mmol / g) and add it to 60 mL of a 15 wt% ammonium fluoride / methanol solution. In a polytetrafluoroethylene beaker, stir and react at 60 °C for 10 h. After the reaction is complete, centrifuge to separate the solid, wash three times with methanol, then wash with water until neutral, and dry at 80 °C for 6 h to obtain the pore-expanding material, denoted as pore-expanding material-2.
[0038] 0.5 g of the above-mentioned pore-expanding material-2 was dispersed in 25 mL of anhydrous ethanol and sonicated for 15 min to achieve uniform dispersion, obtaining a dispersion. Under nitrogen protection and vigorous stirring, tetraethyl titanate was slowly added dropwise using a microsyringe (controlling the Si / Ti ratio in the titanium-silicon molecular sieve to 60). After the addition was complete, the mixture was refluxed and stirred in an oil bath at 50 °C for 6 h. After the reaction was complete, the solid was collected by centrifugation, washed three times with ethanol, and dried overnight at 80 °C. Finally, the dried product was heated to 500 °C in a muffle furnace at a heating rate of 2 °C / min and calcined in air for 6 h to obtain isomorphously substituted titanium-silicon molecular sieve, denoted as titanium-silicon molecular sieve-2.
[0039] Example 3
[0040] Weigh 1.0 g of pure silicon layered precursor PLS-3 (water content 20 mmol / g) and add it to 40 mL of a 15 wt% ammonium fluoride / methanol solution. In a polytetrafluoroethylene beaker, stir and react at 40 °C for 8 h. After the reaction is complete, centrifuge to separate the solid, wash three times with methanol, then wash with water until neutral, and dry at 80 °C for 6 h to obtain the pore-expanding material, denoted as pore-expanding material-3.
[0041] 0.5 g of the above-mentioned pore-expanding material-3 was dispersed in 25 mL of anhydrous ethanol and sonicated for 20 min to achieve uniform dispersion. Under nitrogen protection and vigorous stirring, tetraethyl titanate was slowly added dropwise using a microsyringe (controlling the Si / Ti ratio in the titanium-silicon molecular sieve to 50). After the addition was complete, the mixture was refluxed and stirred in an oil bath at 55 °C for 6 h. After the reaction was complete, the solid was collected by centrifugation, washed three times with ethanol, and dried overnight at 80 °C. Finally, the dried sample was heated to 600 °C in a muffle furnace at a heating rate of 2 °C / min and calcined in air for 5 h to obtain isomorphously substituted titanium-silicon molecular sieve, denoted as titanium-silicon molecular sieve-3.
[0042] Comparative Example 1
[0043] 1.2 g of PLS-3 was added to 0.95 g of H2TiF6 solution (concentration of 60 wt%) and 30 g of deionized water, and reacted in a polytetrafluoroethylene beaker at 35 °C for 5 h. The product after reaction was collected by vacuum filtration and washed with a large amount of deionized water to prepare titanium silicon molecular sieve-4.
[0044] The titanium-silicon molecular sieves of Examples 1-3 and Comparative Example 1 were used for the epoxidation reaction of 1-pentene / hydrogen peroxide and 1-hexene / hydrogen peroxide. The reaction conditions were: 10 mmol of olefin, 10 mmol of H2O2 (a 30 wt% aqueous solution), 20 mg of catalyst (50 mg when the titanium-silicon molecular sieve of Comparative Example 1 was used as a catalyst), 60 °C, and 2 h. The results are shown in Table 1.
[0045] Table 1. Results of Catalytic Performance Verification
[0046] As can be seen from Table 1, the conversion rates of 1-pentene and 1-hexene by the titanium-silicon molecular sieve prepared in this invention are higher than those of the titanium-silicon molecular sieve in Comparative Example 1. This indicates that the titanium-silicon molecular sieve prepared in this invention in two steps, first by expanding the pores with an ammonium fluoride organic solution and then by isomorphous substitution with a titanium source, can significantly improve the catalytic activity of the catalyst.
[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing isomorphously substituted titanium-silicon molecular sieves, characterized in that, Includes the following steps: (1) A pore-expanding material is obtained by mixing a pure silicon layered precursor with an ammonium fluoride organic solution and reacting the mixture. (2) Disperse the pore-expanding material in ethanol, add a titanium source for reaction, drying and calcination to obtain isomorphous substituted titanium silicon molecular sieve.
2. The method for preparing isomorphously substituted titanium-silicon molecular sieves according to claim 1, characterized in that, In step (1), the pure silicon layered precursor includes PLS-3, PLS-4, MCM-47 or RUB-39.
3. The method for preparing isomorphously substituted titanium-silicon molecular sieves according to claim 1 or 2, characterized in that, In step (1), the concentration of ammonium fluoride in the ammonium fluoride organic solution is 10~20wt%, and the solvent in the ammonium fluoride organic solution includes one or more of methanol, ethanol, ethylene glycol and ethyl acetate; the mass-volume ratio of the pure silicon layered precursor to the ammonium fluoride organic solution is 1g:40~60mL.
4. The method for preparing isomorphously substituted titanium-silicon molecular sieves according to claim 3, characterized in that, In step (1), the reaction temperature is 30~60℃ and the time is 4~10h.
5. The method for preparing isomorphously substituted titanium-silicon molecular sieves according to claim 1, 2, or 4, characterized in that, In step (2), the molar ratio of silicon in the pore-expanding material to titanium in the titanium source is 30~100:
1.
6. The method for preparing isomorphously substituted titanium-silicon molecular sieves according to claim 5, characterized in that, In step (2), the roasting temperature is 500~600℃ and the time is 4~6h.
7. The isomorphously substituted titanium-silicon molecular sieve prepared by the method of any one of claims 1 to 6.
8. The application of the isomorphously substituted titanium-silicon molecular sieve of claim 7 as a catalyst in the epoxidation reaction of olefins.
9. The application of the isomorphously substituted titanium-silicon molecular sieve according to claim 8 in the olefin epoxidation reaction, characterized in that, The process includes the following steps: mixing olefins, hydrogen peroxide, titanium silicate molecular sieves, and solvents, followed by an epoxidation reaction.
10. The application of the isomorphously substituted titanium-silicon molecular sieve according to claim 9 in the olefin epoxidation reaction, characterized in that, The molar mass ratio of the olefin and the titanium-silicon molecular sieve is 1 mmol: 2~3 mg.