Preparation method of high-activity hierarchical porous titanium silicalite molecular sieve
The multi-stage pore TS-1 molecular sieve was prepared by spray thermal decoupling dry adhesive conversion method, which solved the problem of mismatch between the side reaction of traditional titanium silicon molecular sieve in oxidation reaction and the insertion rate of titanium silicon components, and achieved high activity and low cost The multi-stage pore structure and the formation of TiO6 species have improved catalytic performance.
Patent Information
- Application Number
- CN202411390588.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2025-01-07
AI Technical Summary
Traditional microporous titanium silicon molecular sieve can easily lead to side reactions in oxidation reactions, and the rate of insertion of titanium and silicon components into the framework does not match, making it easy to produce anatase that is harmful to catalytic activity. In addition, the preparation of existing multi-stage pore TS-1 molecular sieve Methods The use of mesoporous template agent is costly and has high environmental pressure.
The spray thermal decoupled dry adhesive conversion method is used to form porous titanium silicon oxide powder by ultrasonic spraying, and react with tetrapropyl ammonium hydroxide under infrared lamp to form the initial dry adhesive, and then convert and roast in the crystallization kettle. Avoid the use of mesoporous template agents to promote the formation of multi-stage pore structures and highly active TiO6 species.
The multi-stage pore TS-1 molecular sieve without anatase and rich in TiO6 was successfully prepared, which reduced the preparation cost, improved the catalytic activity, avoided the formation of anatase, and achieved efficient catalytic performance.
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Figure CN119263294A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of molecular sieve catalyst preparation, and in particular relates to a method for preparing a high-activity multi-level porous titanium silicon molecular sieve. Background Art
[0002] Titanium silicate molecular sieve (TS-1) with MFI topology has been widely used in catalytic reactions such as olefin epoxidation, phenol hydroxylation and oxidative desulfurization due to its good activity, selectivity and stability. However, with the continuous expansion of industrial applications, traditional microporous molecular sieves cannot pass macromolecular reactants in various oxidation reactions, which easily leads to side reactions, thus limiting the catalytic activity of the molecular sieve. Secondly, during the preparation of TS-1 molecular sieve, the rates of titanium and silicon components inserting into the framework are not matched, which easily produces anatase (TiO2) that is harmful to catalytic activity, especially at low silicon-titanium ratios. In addition, TiO6 has recently been considered to be a species with higher activity than TiO4. By constructing TiO6 species in TS-1 molecular sieve, its catalytic activity can be greatly improved. Therefore, the construction of a multi-level porous TS-1 molecular sieve without anatase and rich in TiO6 is of great significance for its industrial application.
[0003] Patent CN116495747A discloses a method for preparing an amide-assisted nano-multi-level pore TS-1 molecular sieve. The obtained TS-1 exhibits high catalytic activity in olefin epoxidation and oxidative desulfurization reactions due to its high TiO6 species concentration and nano-multi-level pore structure. Wang et al. assisted the synthesis of TS-1 molecular sieve with L-lysine, which greatly increased the TiO6 species content in the molecular sieve (Chin.J.Catal.2021,42,2189-2196). Yao et al. prepared a multi-level pore TS-1 molecular sieve rich in TiO6 species by amphiphilic organosilane-assisted dry gel conversion method (Chem.Eng.J.,2023,475,146053). All of these works introduce a bifunctional mesoporous template to stabilize the Ti component, thereby promoting the formation of multi-level pore structure and TiO6 species. However, the use of mesoporous templates greatly increases the preparation cost and environmental pressure of molecular sieves. Therefore, it is particularly necessary to develop a simple and inexpensive method to construct molecular sieves to solve the above problems. Summary of the invention
[0004] The purpose of the present invention is to provide a method for preparing a high-activity multi-level porous titanium silicalite molecular sieve, which prepares anatase-free, TiO6-rich multi-level porous TS-1 molecular sieve by simple spray pyrolysis coupled dry gel conversion without adding additional mesoporous template agents.
[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:
[0006] The present invention provides a method for preparing a high-activity multi-level porous titanium silicon molecular sieve, comprising the following steps:
[0007] Step (1): adding a silicon source to an ammonia solution, stirring evenly, then adding a mixed solution of a titanium source and anhydrous ethanol, stirring to form an initial sol;
[0008] Step (2): pouring the initial sol obtained in step (1) into an ultrasonic spray pyrolysis device for ultrasonic spray pyrolysis to obtain porous titanium silicon oxide powder;
[0009] Step (3): adding the porous titanium silicon oxide powder obtained in step (2) into a tetrapropylammonium hydroxide solution, stirring and evaporating to dryness under infrared light to obtain an initial dry gel;
[0010] Step (4): placing the initial dry glue obtained in step (3) into a crystallization kettle filled with water, and ensuring that the dry glue does not come into direct contact with the water, placing the crystallization kettle in an oven to convert the dry glue, and then calcining the obtained powder to obtain a multi-level porous titanium silicon molecular sieve catalyst.
[0011] Preferably, in step (1), the silicon source is one of ethyl orthosilicate, white carbon black and silica sol, and the titanium source is tetrabutyl titanate;
[0012] Preferably, the composition of the initial sol in step (1) is: the molar ratio of SiO2, H2O, TiO2, NH4OH and EtOH is 1:58:0.025:0.3:6.
[0013] Preferably, the stirring temperature in step (1) is room temperature and the stirring time is 5-10 h.
[0014] Preferably, the pyrolysis temperature in step (2) in step (3) is 350-600°C
[0015] Preferably, the concentration of tetrapropylammonium hydroxide in step (3) is 10 wt %, and the solid-liquid mass ratio of the porous titanium silicon oxide powder to the tetrapropylammonium hydroxide solution is 1:12.
[0016] Preferably, in step (4), the dry glue conversion temperature is 150-180° C., and the dry glue conversion time is 1-4 days.
[0017] Preferably, the calcination temperature in step (4) is 550° C. and the calcination time is 6 hours.
[0018] Beneficial effects of the present invention
[0019] The present invention provides a method for preparing a high-activity multi-level porous titanium silicon molecular sieve. Compared with the prior art, the present invention avoids the use of a mesoporous template agent by coupling a spray pyrolysis with a dry gel conversion strategy, and the molecular sieve preparation cost is low and the method is simple. During the spray pyrolysis process, a large number of pores are introduced into the solid microspheres due to the rapid evaporation of water, which promotes the formation of a mesoporous structure during the dry gel conversion process. At the same time, during the pyrolysis process, the silicon-titanium components are rapidly condensed to form a defective Si-O-Ti structure, which not only inhibits the formation of anatase during the dry gel conversion process, but also promotes the formation of highly active TiO6 species. Finally, through this simple synthesis method without a mesoporous template agent, a multi-level porous TS-1 molecular sieve without anatase and rich in TiO6 species is obtained. This method provides a broad prospect for the design and manufacture of efficient TS-1 molecular sieve catalysts. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 X-ray diffraction patterns of the TS-1 molecular sieve samples of Examples 1 and 2 of the present invention and Comparative Example 1;
[0021] Figure 2 The transmission electron microscope photos of the TS-1 molecular sieve sample of Example 1 of the present invention and Comparative Example 1;
[0022] Figure 3 The UV-Vis spectra of the TS-1 molecular sieve samples of Examples 1 and 2 of the present invention and Comparative Example 1;
[0023] Figure 4 It is a schematic structural diagram of the ultrasonic spray pyrolysis device of the present invention.
[0024] In the figure, 1. ultrasonic sprayer, 2. tubular pyrolysis furnace, 3. gas washing bottle. DETAILED DESCRIPTION
[0025] The present invention discloses a method for preparing a high-activity multi-level porous titanium silicon molecular sieve, comprising the following steps:
[0026] Step (1): Add a silicon source to an ammonia solution and stir evenly, then add a mixed solution of a titanium source and anhydrous ethanol, preferably stirring at room temperature for 5-10 hours to form an initial sol; the silicon source is one of ethyl orthosilicate, white carbon black, and silica sol, and the titanium source is preferably tetrabutyl titanate; the composition of the initial sol is preferably: the molar ratio of SiO2, H2O, TiO2, NH4OH and EtOH is 1:58:0.025:0.3:6.
[0027] Step (2): pouring the initial sol obtained in step (1) into an ultrasonic spray pyrolysis device for ultrasonic spray pyrolysis, wherein the pyrolysis temperature is preferably 350-600° C., the spray flow rate in the pyrolysis furnace is preferably 0.5 L / min, the spray device frequency is preferably 1.7 MHz, and the powder is recovered through a gas washing bottle to obtain porous titanium silicon oxide powder; the structure of the ultrasonic spray pyrolysis device is as follows: Figure 4 As shown, it is specifically composed of an ultrasonic sprayer 1, a tubular pyrolysis furnace 2 and a gas washing bottle 3. The initial sol is poured into the ultrasonic sprayer 1 at one end, forms aerosol through the ultrasonic sprayer 1, is pyrolyzed through the tubular pyrolysis furnace 2, and is recovered through the gas washing bottle 3 at the other end. The ultrasonic sprayer 1, tubular pyrolysis furnace 2 and gas washing bottle 3 are purchased from commercial sources;
[0028] Step (3): adding the porous titanium silicon oxide powder obtained in step (2) to a tetrapropylammonium hydroxide solution of a certain concentration, stirring and evaporating under infrared light to obtain an initial dry glue; the concentration of the tetrapropylammonium hydroxide is preferably 10wt%, and the solid-liquid mass ratio of the porous titanium silicon oxide powder to the tetrapropylammonium hydroxide solution is preferably 1:12;
[0029] Step (4): the initial dry glue obtained in step (3) is placed in a crystallization kettle containing a small amount of water, and it is ensured that the dry glue does not come into direct contact with the water. The crystallization kettle is placed in an oven to carry out dry glue conversion. The dry glue conversion temperature is preferably 150-180°C, and the dry glue conversion time is preferably 1-4 days. The obtained powder is then calcined at 550°C for 6 hours to obtain a multi-level porous titanium silicon molecular sieve.
[0030] The present invention is further described in detail below with reference to specific examples, and the raw materials involved in the examples are all commercially available.
[0031] Example 1
[0032] A method for preparing a high-activity multi-level porous titanium silicon molecular sieve comprises the following steps:
[0033] (1): Weigh 4.145 g of tetraethyl orthosilicate and slowly add it dropwise to 20.362 g of 1 wt% ammonia solution and stir at room temperature for 6 h; mix 0.164 g of tetrabutyl titanate and 5.329 g of anhydrous ethanol and stir at room temperature for 10 h; then mix and stir the two systems for 10 h to form an initial sol;
[0034] (2): The initial sol is poured into an ultrasonic spray pyrolysis device, and the temperature of the tubular pyrolysis furnace, the frequency of the spray device, and the spray purge air flow rate are set to 600°C, 1.7 MHz, and 0.5 L / min, respectively. The spray device is turned on, and the sol aerosol passes through the tubular pyrolysis furnace and is recovered through a washing bottle to obtain a porous titanium silicon oxide powder;
[0035] (3): 1 g of porous titanium silicon oxide powder was added to 12 g of 10 wt% tetrapropylammonium hydroxide solution, and the mixture was stirred and evaporated to dryness under infrared light to obtain an initial dry gel;
[0036] (4): Take 1g of the initial dry glue and put it into a 25mL crystallization kettle. The bottom of the crystallization kettle is filled with 2mL of water, and it is ensured that the dry glue does not come into direct contact with the water. The crystallization kettle is placed in a 175℃ oven for 2 days to convert the dry glue. Then the obtained powder is placed in a muffle furnace and calcined at 550℃ for 6 hours to obtain a molecular sieve catalyst.
[0037] Example 2
[0038] A method for preparing a high-activity multi-level porous titanium silicon molecular sieve comprises the following steps:
[0039] (1): Weigh 4.145 g of tetraethyl orthosilicate and slowly add it dropwise to 20.362 g of 1 wt% ammonia solution and stir at room temperature for 6 h; mix 0.164 g of tetrabutyl titanate and 5.329 g of anhydrous ethanol and stir at room temperature for 10 h; then mix and stir the two systems for 10 h to form an initial sol;
[0040] (2): Pour the initial sol into an ultrasonic spray pyrolysis device, set the temperature of the tubular pyrolysis furnace, the frequency of the spray device, and the spray purge air flow rate to 450°C, 1.7 MHz, and 0.5 L / min, respectively, turn on the spray device, and after the sol aerosol passes through the tubular pyrolysis furnace, it is recovered through a washing bottle to obtain a porous titanium silicon oxide powder;
[0041] (3): 1 g of porous titanium silicon oxide powder was added to 12 g of 10 wt% tetrapropylammonium hydroxide solution, and the mixture was stirred and evaporated to dryness under infrared light to obtain an initial dry gel;
[0042] (4): Take 1g of the initial dry glue and put it into a 25mL crystallization kettle. The bottom of the crystallization kettle is filled with 2mL of water, and it is ensured that the dry glue does not come into direct contact with the water. The crystallization kettle is placed in a 175℃ oven for 2 days to convert the dry glue. Then the obtained powder is placed in a muffle furnace and calcined at 550℃ for 6 hours to obtain a molecular sieve catalyst.
[0043] Comparative Example 1
[0044] A method for preparing a high-activity multi-level porous titanium silicon molecular sieve comprises the following steps:
[0045] (1): Weigh 4.145 g of tetraethyl orthosilicate and slowly add it dropwise to 20.362 g of 1 wt% ammonia solution and stir at room temperature for 6 h; mix 0.164 g of tetrabutyl titanate and 5.329 g of anhydrous ethanol and stir at room temperature for 10 h; then mix and stir the two systems for 10 h to form an initial sol;
[0046] (2): Pour the initial sol into an ultrasonic spray pyrolysis device, set the temperature of the tubular pyrolysis furnace, the frequency of the spray device, and the spray purge air flow rate to 150°C, 1.7 MHz, and 0.5 L / min, respectively, turn on the spray device, and after the sol aerosol passes through the pyrolysis furnace, it is recovered through a washing bottle to obtain a porous titanium silicon oxide powder;
[0047] (3): 1 g of porous titanium silicon oxide powder was added to 11.85 g of 10 wt% tetrapropylammonium hydroxide solution, and the mixture was stirred and evaporated to dryness under infrared light to obtain an initial dry gel;
[0048] (4): Take 1g of the initial dry glue and put it into a 25mL crystallization kettle. The bottom of the crystallization kettle is filled with 2mL of water, and it is ensured that the dry glue does not come into direct contact with the water. The crystallization kettle is placed in a 175℃ oven for 2 days to convert the dry glue. Then the obtained powder is placed in a muffle furnace and calcined at 550℃ for 6 hours to obtain a molecular sieve catalyst.
[0049] The obtained catalyst samples were characterized. Figure 1 X-ray diffraction patterns of the TS-1 molecular sieve samples of Examples 1 and 2 of the present invention and Comparative Example 1; Figure 2 The transmission electron microscope photos of the TS-1 molecular sieve sample of Example 1 of the present invention and Comparative Example 1 are shown in FIG. Figure 2 a represents the TS-1 molecular sieve sample of Example 1, Figure 2 b represents the catalyst sample of Comparative Example 1, Figure 3 The UV-Vis spectra of the TS-1 molecular sieve samples of Examples 1 and 2 of the present invention and Comparative Example 1 are shown.
[0050] The results show that all samples show MFI topological structure, indicating that TS-1 molecular sieve was successfully synthesized by spray pyrolysis coupled with dry gel conversion. Compared with the comparative samples, the example samples show a multi-level pore structure, no anatase, and a higher TiO6 species content. The catalytic 1-hexene epoxidation performance of the samples was investigated at 60°C (catalyst dosage 50 mg, 1-hexene dosage 10 mmol, hydrogen peroxide dosage 10 mmol, reaction time 2 h), as shown in Table 1. The results show that compared with the comparative examples, the example samples show a higher 1-hexene conversion rate.
[0051] Table 1
[0052]
[0053] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.
Claims
1. A method for preparing a high-activity multi-level porous titanium silicon molecular sieve, characterized in that: The following steps are involved: Step (1): adding a silicon source to an ammonia solution, stirring evenly, then adding a mixed solution of a titanium source and anhydrous ethanol, stirring to form an initial sol; Step (2): pouring the initial sol obtained in step (1) into an ultrasonic spray pyrolysis device for ultrasonic spray pyrolysis to obtain porous titanium silicon oxide powder; Step (3): adding the porous titanium silicon oxide powder obtained in step (2) into a tetrapropylammonium hydroxide solution, stirring and evaporating to dryness under infrared light to obtain an initial dry gel; Step (4): placing the initial dry glue obtained in step (3) into a crystallization kettle filled with water, and ensuring that the dry glue does not come into direct contact with the water, placing the crystallization kettle in an oven to convert the dry glue, and then calcining the obtained powder to obtain a multi-level porous titanium silicon molecular sieve catalyst.
2. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: In the step (1), the silicon source is one of ethyl orthosilicate, white carbon black and silica sol, and the titanium source is tetrabutyl titanate.
3. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: The composition of the initial sol in step (1) is: the molar ratio of SiO2, H2O, TiO2, NH4OH and EtOH is 1:58:0.025:0.3:
6.
4. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: The stirring temperature in step (1) is room temperature, and the stirring time is 5-10 hours.
5. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: The pyrolysis temperature in step (2) in step (3) is 350-600°C.
6. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: The concentration of tetrapropylammonium hydroxide in step (3) is 10 wt %, and the solid-liquid mass ratio of the porous titanium silicon oxide powder to the tetrapropylammonium hydroxide solution is 1:
12.
7. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: In the step (4), the dry glue conversion temperature is 150-180° C., and the dry glue conversion time is 1-4 days.
8. The method for preparing a high-activity multi-level porous titanium silicon molecular sieve according to claim 1, characterized in that: The temperature of the calcination treatment in step (4) is 550° C. and the time is 6 hours.