A method for template-free synthesis of fau and emt molecular sieves with superlarge pore volume

Abstract

The present application relates to the technical field of hierarchical pore molecular sieve materials, and discloses a preparation method of hierarchical pore FAU type and EMT molecular sieve with super-large pore volume. A silicon source such as sodium silicate, silica sol, orthosilicic acid, fumed silica and the like is mixed with an aluminum source such as aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropylate, tertiary butyl aluminum and the like to configure a gel with a certain proportion, and then additional silicon source and aluminum source are added to adjust the proportion, and crystallization is carried out at a certain temperature for a period of time. The mixture is separated by filtration, and then washed by water filtration. The obtained solid is dried to obtain the hierarchical pore molecular sieve material. The method provided by the present application has a simple synthesis process, does not need to use an organic template agent, has wide raw material selection, and has low production cost. The molecular sieve obtained by the present application has high total specific surface area and large external specific surface area (FAU type 834 m 2 / g and 138 m 2 / g, EMT type 591 m 2 / g and 199 m 2 / g), and super-large pore volume (FAU type 1.40 cm 3 / g, EMT type 0.92 cm 3 / g).

Description

Technical Field

[0001] This invention relates to a method for producing FAU-type and EMT-type molecular sieves with ultra-large pore volumes. Sodium silicate, silica sol, orthosilicic acid, and fumed silica are used as silicon sources, and aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropoxide, and tert-butylaluminum are used as aluminum sources. A hydrothermal crystallization method is employed, and the size and aggregation of the molecular sieves are controlled by regulating the nucleation, growth, and composition of the mother liquor, thereby obtaining FAU-type and EMT-type molecular sieves with ultra-large pore volumes. Background Technology

[0002] Molecular sieves have wide applications in petrochemicals, adsorption, and other fields due to their high specific surface area, good acidity, tunable pore size, and good hydrothermal stability. When used as catalysts, the diffusion rate of feed / product molecules within the molecular sieve is a crucial factor determining its performance.

[0003] Due to the increasing weight and quality of crude oil, the size of crude oil molecules increases. Molecular sieves with only microporous structures lack sufficient diffusion capacity, easily leading to catalyst coking and carbon buildup, resulting in rapid catalyst deactivation. Introducing mesopores into molecular sieves can increase the external specific surface area, shorten the diffusion path, and allow reactant molecules to diffuse more quickly, thus delaying catalyst deactivation caused by coking and carbon buildup. Industrially, hydrothermal steam treatment of molecular sieves, such as USY, is commonly used to generate mesopores; however, its external specific surface area and pore volume ratio are relatively low (the external specific surface area is generally below 100 μm). 2 / g, mesoporous pore volume less than 0.5cm³ 3 / g). Therefore, under the general trend of heavy oil refining, developing a method for synthesizing molecular sieves with high specific surface area and large pore volume is of great significance. In recent years, researchers have made many efforts in synthesizing molecular sieve materials with mesoporous structures, mainly using template methods and post-treatment methods. Templates used include hard templates and organic templates. However, the hard template method requires precise molecular sieve mother liquor impregnation, while the organic template method faces problems such as high cost, toxicity, and environmental unfriendliness. Furthermore, the template method ultimately requires high-temperature calcination to remove the template agent, easily generating pollution emissions. These problems severely limit the industrial application of the template method. The post-treatment method generally uses acid and alkali reagents to treat the molecular sieve material, generating mesopores by removing silica and alumina. However, this method damages the molecular sieve framework structure, and the treatment of wastewater generated after treatment is also a difficult problem to solve. Thus, the main problems currently facing the synthesis of graded porous molecular sieves are low external specific surface area, low pore volume, complex synthesis methods, expensive raw materials, and environmental unfriendliness, making industrial production difficult. How to synthesize graded porous molecular sieves in a green and environmentally friendly one-step process in an inorganic system has become an urgent problem for researchers to solve. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for obtaining ultra-large pore volume FAU-type molecular sieves and EMT-type molecular sieves by controlling the nucleation and growth process of molecular sieves without adding organic template agents, using sodium silicate, silica sol, or orthosilicic acid as silicon sources and aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropoxide, or tert-butylaluminum as aluminum sources. The graded pore molecular sieves prepared by this invention have high specific surface area, large pore volume, low raw material cost, and a simple preparation method that does not require organic template agents, making it environmentally friendly and suitable for industrial production.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] (1) Mix silicon source, aluminum source and deionized water evenly and age to obtain a clear and transparent gel.

[0007] (2) Add additional silicon and aluminum sources to the gel synthesized in step (1), stir evenly, and obtain molecular sieve synthesis mother liquor.

[0008] (3) The molecular sieve mother liquor obtained in step (2) is transferred into a crystallization kettle for crystallization, and then FAU type molecular sieve or EMT type molecular sieve with ultra-large pore volume is obtained by filtration, washing and drying.

[0009] The silicon source is one or more of sodium silicate, silica sol, orthosilicic acid, and fumed silica. The aluminum source is one or more of aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropoxide, and tert-butylaluminum.

[0010] Preferably, (1) the molar ratio of sodium oxide to aluminum oxide in the gel is 8-20, the molar ratio of silicon oxide to aluminum oxide is 10-30, and the molar ratio of water to aluminum oxide is 120-500.

[0011] Preferably, (1) the gel aging temperature is 10-70℃ and the aging time is 1-72 hours.

[0012] Preferably, (2) the molecular sieve precursors sodium oxide to alumina have a molar ratio of 3-8, silicon oxide to alumina have a molar ratio of 5-20, and water to alumina have a molar ratio of 90-400.

[0013] Preferably, in the crystallization process described in (3), the crystallization temperature is 30-120℃ and the crystallization time is 2-120 hours.

[0014] This invention uses sodium silicate, silica sol, orthosilicic acid, and fumed silica as silicon sources, and aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropoxide, and tert-butylaluminum as aluminum sources. A hydrothermal crystallization method is employed to regulate the nucleation and growth of molecular sieves, resulting in FAU-type and EMT-type molecular sieves with ultra-large pore volumes. This method uses inexpensive raw materials, eliminates the need for organic template agents, and reduces costs. The crystallized mixture does not require centrifugation; simple filtration suffices, making the operation simple and suitable for industrial production. Attached Figure Description

[0015] Figure 1 The XRD patterns of the FAU-type molecular sieves obtained in Example 1 and Example 1-1 are shown below.

[0016] Figure 2 The N2 adsorption-desorption isotherms of the FAU-type molecular sieves obtained in Example 1 and Example 1-1 are shown below.

[0017] Figure 3 The image shows a scanning electron microscope (SEM) image of the FAU-type molecular sieve obtained in Example 1.

[0018] Figure 4 The image shows a scanning electron microscope (SEM) image of the FAU-type molecular sieve obtained in Example 1-1.

[0019] Figure 5 The XRD pattern of the FAU-type molecular sieve obtained in Example 2;

[0020] Figure 6 The N2 adsorption-desorption isotherm and pore size distribution diagram of the FAU-type molecular sieve obtained in Example 2 are shown below.

[0021] Figure 7 This is a scanning electron microscope image of the FAU-type molecular sieve obtained in Example 2;

[0022] Figure 8 This is a transmission electron microscope image of the FAU-type molecular sieve obtained in Example 2;

[0023] Figure 9 The FAU-type molecular sieve obtained in Example 2 27 Al NMR image

[0024] Figure 10 The XRD pattern of the FAU-type molecular sieve obtained in Example 3;

[0025] Figure 11 The N2 adsorption-desorption isotherm diagram and pore size distribution diagram of the FAU type molecular sieve obtained in Example 3 are shown below.

[0026] Figure 12 The XRD pattern of the FAU-type molecular sieve obtained in Example 4;

[0027] Figure 13The N2 adsorption-desorption isotherm of the FAU-type molecular sieve obtained in Example 4 is shown below.

[0028] Figure 14 The XRD pattern of the EMT-type molecular sieve obtained in Example 5;

[0029] Figure 15 The N2 adsorption-desorption isotherm and pore size distribution diagram of the EMT molecular sieve obtained in Example 5 are shown below.

[0030] Figure 16 This is a scanning electron microscope image of the EMT-type molecular sieve obtained in Example 5. Detailed Implementation

[0031] This invention provides a method for synthesizing FAU-type molecular sieves with ultra-large pore volume without a mold, comprising the following steps:

[0032] (1) Mix silicon source, aluminum source and deionized water evenly and age to obtain a clear and transparent gel.

[0033] (2) Add additional silicon and aluminum sources to the gel synthesized in step (1), stir evenly, and obtain molecular sieve synthesis mother liquor.

[0034] (3) The molecular sieve mother liquor obtained in step (2) is transferred into a crystallization kettle for crystallization. Then, the FAU type molecular sieve or EMT type molecular sieve with ultra-large pore volume is obtained by filtration, washing and drying.

[0035] In this invention, the silicon source is one or more of sodium silicate, silica sol, orthosilicic acid, and fumed silica. The aluminum source is one or more of aluminum powder, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum isopropoxide, and tert-butylaluminum.

[0036] In this invention, the preferred molar ratio of sodium oxide to aluminum oxide in the gel of step (1) is 8-20, the preferred molar ratio of silicon oxide to aluminum oxide is 10-30, and the preferred molar ratio of water to aluminum oxide is 120-500. The preferred aging temperature of the gel is 10-70℃, and the preferred aging time is 1-72 hours.

[0037] In this invention, the preferred molar ratio of sodium oxide to alumina in the molecular sieve mother liquor in step (2) is 3-8, the preferred molar ratio of silicon oxide to alumina is 5-20, and the preferred molar ratio of water to alumina is 90-400. During the crystallization process, the preferred crystallization temperature is 30-120℃, and the preferred crystallization time is 2-120 hours.

[0038] This invention controls the size and aggregation of molecular sieves by regulating their nucleation, growth, and mother liquor composition, thereby obtaining FAU-type and EMT-type molecular sieves with ultra-large pore volumes. This invention has no special requirements for silicon and aluminum sources or water; industrial silicon, aluminum, and industrial water are sufficient. Furthermore, the use of industrial sodium silicate, industrial sodium aluminate, and industrial water as raw materials further reduces costs.

[0039] The FAU-type molecular sieve with ultra-large pore volume prepared by the above-described method provided by this invention can achieve a specific surface area of ​​up to 834 m². 2 / g, pore volume 1.40cm 3 / g. The specific gravity of EMT type molecular sieves can reach up to 591m. 2 / g, pore volume 0.92cm 3 / g.

[0040] The technical solution of the present invention will be further described below with reference to some specific implementation examples, but the scope of protection of the present invention is not limited thereto.

[0041] Example 1

[0042] A 45g solution of 26wt% sodium silicate was prepared using silica sol and NaOH and placed in a 100℃ oven until clear. Aluminum powder was then added at a silica to alumina molar ratio of 1:9, stirred thoroughly, and aged at 25℃ for 24 hours. The resulting solution was labeled as mother liquor (1). Afterward, aluminum powder was added again to adjust the silica to alumina ratio to 8, stirred thoroughly, and transferred to a crystallization vessel. Crystallization was carried out at 60℃ for 24 hours. The crystallized solid was filtered, washed, and dried at 100℃ for 24 hours to obtain a large-pore-volume FAU-type molecular sieve. This FAU-type molecular sieve was designated FAU-1, and the specific surface area of ​​FAU-1 was 741 m². 2 / g, with a microporous specific surface area of ​​573m² 2 / g, with an external specific surface area of ​​167m² 2 / g, total pore volume is 1.27cm³ 3 / g, micropore volume is 0.23cm³ 3 / g, mesoporous pore volume is 1.04cm³ 3 / g.

[0043] Example 1-1

[0044] The mother liquor (1) obtained in Example 1 was added to an equal amount of aluminum powder as in Example 1, stirred evenly, and transferred to a crystallization kettle for crystallization at 60°C for 48 hours. The crystallized solid was filtered, washed, and dried at 100°C for 24 hours to obtain an ultra-large pore volume FAU-type molecular sieve, denoted as FAU-1-1. The specific surface area of ​​the obtained FAU-1-1 was 789 m². 2 / g, with a microporous specific surface area of ​​647m² 2 / g, with an external specific surface area of ​​141m² 2 / g, total pore volume is 1.50cm³ 3 / g, micropore volume is 0.26cm³ 3 / g, mesoporous pore volume is 1.24cm³ 3 / g.

[0045] Example 2

[0046] A 70g solution of 26wt% sodium silicate was prepared using fumed silica and NaOH solution. Aluminum isopropoxide was then added at a silica to alumina molar ratio of 2:3, and the mixture was stirred until homogeneous. The solution was aged at 20°C for 24 hours. Next, silica sol and sodium aluminate were added to adjust the silica to alumina molar ratio to 9, and the mixture was stirred until homogeneous. The solution was then transferred to a crystallization vessel and crystallized at 60°C for 72 hours. The resulting solid was filtered, washed, and dried at 100°C for 24 hours to obtain a large-pore-volume FAU-type molecular sieve, denoted as FAU-2. The specific surface area of ​​the obtained FAU-2 was 704 m². 2 / g, with a microporous specific surface area of ​​544m³ 2 / g, with an external specific surface area of ​​160m² 2 / g, total pore volume is 1.33cm³ 3 / g, micropore volume is 0.22cm³ 3 / g, mesoporous pore volume is 1.11cm³ 3 / g.

[0047] Example 3

[0048] 60 kg of industrial sodium silicate and 33 kg of industrial high-aluminate were mixed and aged at room temperature for 12 h. Then, 2.3 kg of solid industrial sodium aluminate was added and stirred until homogeneous. The mixture was then hydrothermally crystallized at 100 °C for 24 h. The resulting solid sample was filtered, washed, and dried at 100 °C for 24 h. The obtained FAU-type molecular sieve was named FAU-3. The specific surface area of ​​FAU-3 was 834 m². 2 / g, with a microporous specific surface area of ​​696m² 2 / g, with an external specific surface area of ​​138m² 2 / g, total pore volume is 1.40cm³ 3 / g, micropore volume is 0.28cm³ 3 / g, mesoporous pore volume is 1.12cm³ 3 / g.

[0049] Example 4

[0050] 90 kg of industrial sodium silicate and 49.5 kg of industrial sodium aluminate were mixed and aged at room temperature for 24 h. Then, 4.5 kg of solid industrial sodium aluminate was added and stirred until homogeneous. The mixture was then hydrothermally crystallized at 100 °C for 48 h. The resulting solid sample was filtered, washed, and dried at 100 °C for 24 h. The obtained FAU-type molecular sieve was named FAU-3. The specific surface area of ​​FAU-3 was 506 m². 2 / g, with a microporous specific surface area of ​​438m² 2 / g, with an external specific surface area of ​​68m² 2 / g, total pore volume is 0.86cm³ 3 / g, micropore volume is 0.17cm³ 3 / g, mesoporous pore volume is 0.69cm³ 3 / g.

[0051] Example 5

[0052] A 45g solution of 26wt% sodium silicate was prepared using orthosilicic acid and NaOH solution and dried in an 80℃ oven until clear. Sodium aluminate was then added at a silica to a silica molar ratio of 20. The solution was aged at 30℃ for 48 hours. Sodium aluminate was then added to adjust the silica to alumina molar ratio to 6.5, and the solution was transferred to a crystallization vessel and crystallized at 60℃ for 50 hours. The resulting solid sample was filtered, washed, and dried at 100℃ for 24 hours. The obtained EMT-type molecular sieve was named EMT-1, with a specific surface area of ​​591 m². 2 / g, with a microporous specific surface area of ​​393m² 2 / g, with an external specific surface area of ​​199m² 2 / g, total pore volume is 0.92cm³ 3 / g, micropore volume is 0.16cm³ 3 / g, mesoporous pore volume is 0.76cm³ 3 / g.

[0053] Characterization:

[0054] (1) Characterization of FAU-type molecular sieves

[0055] Figure 1 The XRD patterns of the FAU-type molecular sieves obtained in Example 1 and Example 1-1 are shown below.

[0056] Figure 2 The N2 adsorption-desorption isotherms of the FAU-type molecular sieves obtained in Example 1 and Example 1-1 are shown below.

[0057] Figure 3 The image shows a scanning electron microscope (SEM) image of the FAU-type molecular sieve obtained in Example 1.

[0058] Figure 4 The image shows a scanning electron microscope (SEM) image of the FAU-type molecular sieve obtained in Example 1-1.

[0059] Figure 5 The XRD pattern of the FAU-type molecular sieve obtained in Example 2;

[0060] Figure 6 The N2 adsorption-desorption isotherm and pore size distribution diagram of the FAU-type molecular sieve obtained in Example 2 are shown below.

[0061] Figure 7 This is a scanning electron microscope image of the FAU-type molecular sieve obtained in Example 2;

[0062] Figure 8 This is a transmission electron microscope image of the FAU-type molecular sieve obtained in Example 2;

[0063] Figure 9 The FAU-type molecular sieve obtained in Example 2 27 Al NMR image

[0064] Figure 10 The XRD pattern of the FAU-type molecular sieve obtained in Example 3;

[0065] Figure 11 The N2 adsorption-desorption isotherm diagram and pore size distribution diagram of the FAU type molecular sieve obtained in Example 3 are shown below.

[0066] Figure 12 The XRD pattern of the FAU-type molecular sieve obtained in Example 4;

[0067] Figure 13 The N2 adsorption-desorption isotherm of the FAU-type molecular sieve obtained in Example 4;

[0068] from Figure 1 , Figure 5 , Figure 10 and Figure 12 It can be seen that the sample has the characteristic diffraction peaks of FAU type molecular sieve, indicating that it is an FAU type molecular sieve material. Furthermore, the broadening of the diffraction peaks indicates that the sample has a small grain size. Figure 9 It can be seen from 27 The Al NMR peak is mainly at 60 ppm, indicating that all Al is in a four-coordinated state, representing framework aluminum, and the absence of non-framework aluminum indicates complete crystallization of the molecular sieve. Figure 3 , Figure 4 and Figure 7 Abundant intergranular mesopores can be observed between the particles. Figure 8 As can be seen, the mesopores are well interconnected, and the molecular sieve possesses a good crystal structure. From... Figure 2 , Figure 6 , Figure 11 and Figure 13It can be seen that the adsorption capacity of all samples increases sharply in the low-pressure region, which is due to the microporous structure of the molecular sieve. When P / P0>0.9, the adsorption capacity of the sample increases sharply, which indicates that the sample has a rich intercrystalline mesoporous structure.

[0069] (2) Characterization of EMT-type molecular sieves

[0070] Figure 14 The XRD pattern of the EMT-type molecular sieve obtained in Example 5;

[0071] Figure 15 The N2 adsorption-desorption isotherm and pore size distribution diagram of the EMT molecular sieve obtained in Example 5 are shown below.

[0072] Figure 16 This is a scanning electron microscope image of the EMT-type molecular sieve obtained in Example 5.

[0073] from Figure 14 It can be seen that the molecular sieve has the characteristic diffraction peaks of EMT-type molecular sieves, and the diffraction peaks show broadening, indicating that the sample grain size is small. Figure 15 It can be seen that the sample adsorption capacity increases sharply in the low-pressure region, which is due to the inherent microporous structure of the molecular sieve. At P / P0 = 0.9, the sample adsorption capacity increases dramatically, indicating that the sample possesses abundant intercrystalline mesoporous structures. Furthermore, the pore size distribution diagram shows that the mesopore size of the sample is mainly concentrated around 25 nm. Figure 16 It can be seen that there are abundant intercrystalline mesopores between the molecular sieve particles.

[0074] As can be seen from the above embodiments, the preparation method provided by the present invention uses various raw materials, including industrial sodium silicate, as silicon sources and various aluminum sources, including industrial sodium aluminate, as aluminum sources. By controlling the nucleation and growth process of the molecular sieve, hydrothermal crystallization is used to obtain FAU-type and EMT-type molecular sieves with ultra-large pore volumes. The preparation steps are simple, and no organic template agent is required, making it energy-saving and environmentally friendly.

[0075] 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 template-free synthesis of FAU-type molecular sieves with ultra-large pore volume, characterized in that, The synthesis steps are as follows: Prepare a 45g solution of 26wt% sodium silicate using silica sol and NaOH, and place it in a 100℃ oven until clear. Then, add aluminum powder at a silica to alumina molar ratio of 1:9, stir well, and age at 25℃ for 24 hours. After that, add more aluminum powder to adjust the silica to alumina molar ratio to 8, stir well, transfer to a crystallization kettle, and crystallize at 60℃ for 24 hours. Filter the crystallized solid, wash it, and dry it at 100℃ for 24 hours to obtain the ultra-large pore volume FAU type molecular sieve.

2. A method for template-free synthesis of FAU-type molecular sieves with ultra-large pore volume, characterized in that, The synthesis steps are as follows: Prepare a 70g 26wt% sodium silicate solution using fumed silica and NaOH solution. Then, add aluminum isopropoxide at a silica to alumina molar ratio of 2:3, stir well, and age at 20℃ for 24h. Next, add silica sol and sodium aluminate to adjust the silica to alumina molar ratio to 9, stir well, transfer to a crystallization kettle, and crystallize at 60℃ for 72h. Filter and wash the obtained solid, and dry it at 100℃ for 24h to obtain the ultra-large pore volume FAU type molecular sieve.

3. A method for template-free synthesis of EMT-type molecular sieves with ultra-large pore volume, characterized in that, The synthesis steps are as follows: Prepare a 45g solution of 26wt% sodium silicate using orthosilicic acid and NaOH solution. Place the solution in an 80℃ oven until clear. Then add sodium aluminate at a silicon dioxide to alumina molar ratio of 20. Aging at 30℃ for 48h. Add sodium aluminate to adjust the silicon dioxide to alumina molar ratio to 6.

5. Transfer the solution to a crystallization vessel and crystallize at 60℃ for 50h. Filter the obtained solid sample, wash it, and dry it at 100℃ for 24h to obtain an ultra-large pore volume EMT molecular sieve.

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