A method for synthesizing beta zeolite and beta zeolite

Abstract

The application provides a method for synthesizing Beta molecular sieve, which comprises the following steps: step one, sequentially adding an aluminum source, an alkali source and a template agent into a solvent, stirring to form a solution, continuing to age, and obtaining an intermediate product A; step two, adding a silicon source into another solvent, respectively adding crystal seeds and an additive, stirring until completely dissolved, then adding the intermediate product A in the step one, and then adding an aluminum source to obtain a basic gel B; and step three, performing segmentation and crystallization on the basic gel B in the step two to obtain the Beta molecular sieve. The method can improve the utilization rate of the silicon source and the aluminum source, reduce the amount of the template agent, and obtain a rod-shaped and small-grain Beta molecular sieve with high relative crystallinity and high BET specific surface area.

Description

Technical Field

[0001] This invention belongs to the field of crystalline aluminosilicate molecular sieve synthesis, specifically relating to Beta molecular sieves and their synthesis methods, and particularly to a rod-shaped, small-crystal Beta molecular sieve and its synthesis method, belonging to the field of molecular sieve materials and their synthesis technology. Background Technology

[0002] Molecular sieves are a class of inorganic materials with regular channel structures and uniform pore sizes. Due to their high specific surface area, excellent stability, and tunable acid properties, they are widely used in oil refining, petrochemicals, and fine chemicals. In 1967, Mobil Corporation in the United States first synthesized Beta molecular sieves using tetraethylammonium hydroxide as a template. Beta molecular sieves are the only high-silica molecular sieves with a 12-membered ring channel and an open framework structure, with a pore size of approximately 0.66 × 0.77 nm. They have wide applications in alkylation, catalytic cracking, and adsorption of volatile organic compounds, and are one of the most commonly used molecular sieves in catalysis and adsorption.

[0003] To date, the hydrothermal synthesis of Beta molecular sieves remains the most widely used and mature process. However, during the synthesis of Beta molecular sieves, the utilization rate of the aluminum source is generally high, reaching 85%-100%, while the utilization rate of the silicon source decreases from 90% to about 25% as the silicon-aluminum ratio increases. This results in the actual silicon-aluminum ratio of the Beta molecular sieve being lower than the silicon-aluminum ratio in the feed.

[0004] Under the same silicon-to-aluminum ratio, this application can improve the utilization rate of silicon and aluminum sources, accelerate the crystallization speed of Beta molecular sieves, stabilize the product, reduce the amount of template agent, and reduce the synthesis cost of Beta molecular sieves. This will greatly improve the performance of refining catalysts, drive the technological progress of refining catalysts, and bring huge social and economic benefits. Summary of the Invention

[0005] To address one of the aforementioned problems, this invention provides a molecular sieve and its synthesis method. This application has the beneficial effects of high utilization rate of silicon source and / or aluminum source, or high crystallinity, or reduced template agent dosage and cost reduction.

[0006] This invention includes the following:

[0007] Implementation Method 1: A method for synthesizing Beta molecular sieves, the method comprising the following steps:

[0008] Step 1: Add aluminum source, alkali source, and template agent to the solvent in sequence, stir to form a solution, and continue aging to obtain intermediate product A;

[0009] Step 2: Take another solvent, add silicon source, seed crystal and additive, stir until completely dissolved, add intermediate product A from step 1, and then add aluminum source to obtain alkaline gel B;

[0010] Step 3: Crystallize the alkaline gel B obtained in Step 2 to obtain Beta molecular sieve;

[0011] The amount of template agent used is 2% to 10% of the aluminum source in molar terms. The particle size of the Beta molecular sieve is 100-300 nanometers. The utilization rate of the aluminum source is greater than or equal to 90%, the utilization rate of the silicon source is greater than or equal to 83%, and the crystallinity of the Beta molecular sieve is 90%-160%. In some embodiments, the Beta molecular sieve is rod-shaped or has small crystals.

[0012] Implementation Method 2: According to the method described in Implementation Method 1, the crystallinity is 93%-160%, the solvent is deionized water, and the crystallization is dynamic crystallization or segmented crystallization;

[0013] In step one, the aluminum source, alkali source, template agent, and deionized water are mixed in a molar ratio of Al2O3:0.1-1.2Na2O:0.04-0.2template agent:40-100H2O to obtain the intermediate product A.

[0014] In the entire method, the silicon source, aluminum source, alkali source, template agent, additive, and deionized water are mixed in a molar ratio of 6-80 (SiO2:Al2O3:0.2-2.0, Na2O:0.02-0.1, template agent:0.01-0.06, additive:80-200) to obtain the alkaline gel B, wherein the content of seed crystals in the gel is 1 wt% to 18 wt%.

[0015] Implementation Method 3: According to the method described in Implementation Method 2, the silicon source is one or a mixture of several of water glass, sodium silicate, solid silica gel and fumed silica, and the aluminum source is one or a mixture of several of boehmite, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum oxide and aluminum chloride.

[0016] Implementation Method 4: According to the method described in Implementation Method 2, the alkali source is one or a mixture of two of sodium hydroxide and potassium hydroxide.

[0017] Implementation Method 5: According to the method described in Implementation Method 2, the template agent is one or a mixture of more than one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0018] Implementation Method 6: According to the method described in Implementation Method 2, the additive is an alcohol or a surfactant.

[0019] Implementation Method 7: According to the method described in Implementation Method 6, the alcohol additive is one or a combination of ethanol, ethylene glycol, propylene glycol, isopropanol, and polyvinyl alcohol; the surfactant additive is one or a combination of fatty alcohol polyoxyethylene ether ammonium sulfate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate; the seed crystal is a Beta molecular sieve seed crystal or a Y-type zeolite seed crystal, and the seed crystal mass accounts for 2%-15% of the gel mass.

[0020] Implementation Method 8: According to the method described in Implementation Method 2, the temperature at which the silicon source, aluminum source, alkali source and water are mixed is 25℃-80℃, the aging time is 2h-6h, the crystallization temperature is 110℃-180℃, and the crystallization time is 10h-96h.

[0021] Implementation Method 9: According to any one of Implementation Methods 1-8, the crystallization is segmented and / or dynamic crystallization, wherein the temperature of the first segment of the segmented crystallization is 115°C to 140°C and the crystallization time is 10h-24h, and the temperature of the second segment is greater than 140°C to 175°C and the crystallization time is 14h-72h.

[0022] Implementation Method 10: A Beta molecular sieve, prepared by the method described in any one of Implementation Methods 1-9.

[0023] This application has at least one of the following beneficial effects:

[0024] 1. This application optimizes the template agent dosage relationship through the aforementioned seed crystals, specifically in conjunction with the overall synthesis method of this application to synthesize rod-shaped, small-crystal Beta molecular sieves, thereby reducing the amount of template agent used and thus reducing the synthesis cost of Beta molecular sieves. In addition, approximately 50% to 60% of the cost of the method in this application is the price cost of the template agent. Therefore, in the prior art, the large-scale use of template agents would significantly increase the synthesis cost, as shown in Comparative Example 3. This application also has the beneficial effect of high utilization rate of silicon source and / or aluminum source, or the effect of high crystallinity. Furthermore, this application cannot achieve the cost reduction effect at least when there are no seed crystals or the seed crystals do not conform to the dosage relationship of this application.

[0025] 2. The dosage relationship also includes the control of additive dosage. If the dosage in the specification exceeds the range, it may affect any effect of this application, such as decreased crystallinity or lower silicon-aluminum utilization. Furthermore, increasing the amount of template agent will at least fail to achieve the effect of cost reduction, which reflects that the use of seed crystals reduces the amount of template agent. Seed crystals and template agents have a positive optimization relationship. Increasing the amount of template agent will lead to an increase in the amount of tetrapropylethyl ammonium hydroxide and ethanol. In this application, the amount of tetrapropylethyl ammonium hydroxide and ethanol exceeding the above-mentioned dosage will also affect the crystallinity of this application or lower silicon-aluminum utilization. The relationship between crystallinity, template agent and additive dosage indirectly affects the effect of the method of this application.

[0026] In addition, the technical solution of the present invention also brings many other advantages, which will be described in detail in the specific implementation mode.

[0027] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0029] Figure 1 XRD spectra of Beta zeolites synthesized in Example 1, Comparative Example 1, Example 2, and Comparative Example 2;

[0030] Figure 2 SEM photograph of the Beta zeolite synthesized in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Now, example embodiments will be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar parts, and thus their repetitive description will be omitted.

[0032] In addition, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present invention. However, those skilled in the art will realize that the technical solutions of the present invention can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. can be used. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the present invention.

[0033] It should be noted that the term "Beta" in the Beta zeolite involved in this application can be translated as the Greek letter "β" or the Chinese character "Beta".

[0034] One aspect of the present invention provides a Beta zeolite and a method for synthesizing the same, the method comprising the following steps:

[0035] Step 1: Add an aluminum source, an alkali source, and a template agent in sequence in a solvent, stir to form a solution, and then continue aging to obtain an intermediate product A;

[0036] Step 2: Take another solvent, add silicon source, seed crystal and additive, stir until completely dissolved, add intermediate product A from step 1, and then add aluminum source to obtain alkaline gel B;

[0037] Step 3: Crystallize the alkaline gel B obtained in Step 2 to obtain Beta molecular sieve;

[0038] The amount of template agent used is 2% to 10% of the aluminum source in molar terms. The particle size of the Beta molecular sieve is 100-300 nanometers. The utilization rate of the aluminum source is greater than or equal to 90%, the utilization rate of the silicon source is greater than or equal to 83%, and the crystallinity is 90%-160%. In some embodiments, the Beta molecular sieve is rod-shaped or has a small crystal shape.

[0039] This application optimizes the template agent dosage relationship through the aforementioned seed crystals, specifically in conjunction with the overall synthesis method of this application to synthesize rod-shaped, small-crystal Beta molecular sieves, thereby reducing the amount of template agent used and thus reducing the synthesis cost of Beta molecular sieves. In addition, about 50% to 60% of the cost of the method in this application is the price cost of the template agent. Therefore, the use of a large amount of template agent in the prior art or the increase of template agent as in Comparative Example 3 will significantly increase the synthesis cost. Alternatively, this application also has the beneficial effect of high utilization rate of silicon source and / or aluminum source, or the effect of high crystallinity. Furthermore, this application cannot achieve the cost reduction effect at least when the seed crystals are lacking or the seed crystals do not conform to the dosage relationship of this application. Other related effects of the Beta molecular sieves prepared by this application can be found in Table 1.

[0040] In some embodiments, the crystallinity is 93%-160% or 93%-102%, the solvent is deionized water, and the crystallization is dynamic crystallization or segmented crystallization;

[0041] In step one, the aluminum source, alkali source, template agent, and deionized water are mixed in a molar ratio of Al2O3:0.1-1.2Na2O:0.04-0.2template agent:40-100H2O to obtain the intermediate product A.

[0042] In the entire method, the silicon source, aluminum source, alkali source, template agent, additive, and deionized water are mixed in a molar ratio of 6–80 (SiO2:Al2O3:0.2–2.0, Na2O:0.02–0.1, template agent:0.01–0.06, additive:80–200) to obtain the alkaline gel B, wherein the seed crystal content in the gel is 1 wt% to 18 wt%. In this application, adding the aluminum source in two parts in the first and second steps can increase the utilization rate of the aluminum source. The dynamic crystallization described in this application has the meaning commonly understood by those skilled in the art, referring to the crystallization vessel being in a dynamic, such as rotating, state throughout the crystallization process. The segmented crystallization described in this application has the meaning commonly understood by those skilled in the art, referring to the temperature within the crystallization vessel changing in stages during the crystallization process.

[0043] The dosage relationship also includes the control of additive dosage. Exceeding the dosage range in the specification may affect any effect of this application, such as decreased crystallinity or lower silicon-aluminum utilization. Furthermore, increasing the amount of template agent will at least fail to achieve the effect of cost reduction, which reflects that the seed crystal reduces the amount of template agent. The seed crystal and template agent have a positive optimization relationship. Increasing the amount of template agent leads to an increase in the amount of tetrapropylethyl ammonium hydroxide and ethylene glycol. In this application, the amount of tetrapropylethyl ammonium hydroxide and ethylene glycol exceeding the above dosage also affects the crystallinity of this application or the lower silicon-aluminum utilization. The relationship between crystallinity, template agent and additive dosage indirectly affects the effect of the method of this application.

[0044] In some embodiments, the silicon source is one or a mixture of several of water glass, sodium silicate, solid silica gel, and fumed silica, and the aluminum source is one or a mixture of several of boehmite, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum oxide, and aluminum chloride.

[0045] In some embodiments, the alkali source is one or a mixture of two of sodium hydroxide and potassium hydroxide.

[0046] In some embodiments, the template agent is one or a mixture of more than one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0047] In some embodiments, the additive is an alcohol or a surfactant.

[0048] In some embodiments, the alcohol additive is one or a combination of ethanol, ethylene glycol, propylene glycol, isopropanol, and polyvinyl alcohol; the surfactant additive is one or a combination of fatty alcohol polyoxyethylene ether ammonium sulfate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate; and the seed crystal is a Beta molecular sieve seed crystal or a Y-type zeolite seed crystal, with the seed crystal mass accounting for 2%-15% of the gel mass.

[0049] In some embodiments, the temperature at which the silicon source, aluminum source, alkali source and water are mixed is 25°C-80°C, the aging time is 2h-6h, the crystallization temperature is 110°C-180°C, and the crystallization time is 10h-96h.

[0050] In some embodiments, the crystallization is segmented dynamic crystallization, which is segmented and / or dynamic crystallization. The first segment of the segmented crystallization has a temperature of 115°C to 140°C and a crystallization time of 10h to 24h, and the second segment has a temperature of greater than 140°C to 175°C and a crystallization time of 14h to 72h.

[0051] In some embodiments, this application also provides a Beta molecular sieve, prepared by the synthesis method described in any one of embodiments 1-9, wherein the Beta molecular sieve is rod-shaped and has small crystals. Other related effects of the Beta molecular sieve prepared in this application can be found in Table 1.

[0052] This application will be further illustrated by the following embodiments.

[0053] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0054] In the following embodiments, phase analysis was performed on the synthesized Beta molecular sieves using X-ray powder diffraction, and the relative crystallinity of the products was calculated. The instrument used was a Dutch PANalytial X'Pert Powder X-ray diffractometer. Cu-Kα radiation (wavelength...) was employed. The tube current was 40 mA, the tube voltage was 40 kV, and the step size was 0.013° / s. The scanning angle range for phase analysis was 5°-35°. Crystallinity was calculated using two characteristic diffraction peaks located between 21° and 23°. The ratio of the sum of the areas of these two peaks in the sample to the sum of the areas of these two peaks in the Beta molecular sieve standard was the relative crystallinity of the sample. The Beta molecular sieve used as the crystallinity standard in the examples and comparative examples was a 100% crystallinity standard provided by the Petrochemical Research Institute of China National Petroleum Corporation. All raw materials used in this application are available for purchase. The Beta seed crystals used were prepared by the method disclosed in this application.

[0055] Example

[0056] Example 1

[0057] This embodiment provides a Beta molecular sieve and its synthesis method, which includes the following steps:

[0058] At 45℃, 6g of sodium aluminate was added to 35g of deionized water and stirred until the solution was clear. 20g of sodium hydroxide was added and stirred until the solution was clear. 3.2g of tetraethylammonium hydroxide was added, and the mixture was stirred for 30 minutes, then aged for another 4 hours. The aluminum source, alkali source, template agent, and deionized water were added in a molar ratio of Al₂O₃:0.8Na₂O:0.12 tetraethylammonium hydroxide:60H₂O to obtain intermediate product A1. 125g of water glass and 160g of H₂O were weighed and placed in a beaker. Under stirring in a 50℃ water bath, 12g of… Beta seed crystals (3.00%) and 6.0g ethanol were stirred until completely dissolved. Then, intermediate product A1 was added, followed by the slow addition of 32.8g of 30% sodium aluminate solution. The mixture was stirred for 30min to obtain alkaline gel B1. The molar ratio of the components in the gel reaction mixture was 0.5Na2O:Al2O3:35SiO2:120H2O:0.05tetraethylammonium hydroxide:0.04ethanol. The mixture was then placed in a reactor for dynamic crystallization at 120℃ for 10h and 160℃ for 18h. After washing and filtration, the mixture was dried at 120℃ for 12h to obtain Beta molecular sieve 1.

[0059] like Figure 1-2 As shown, the Beta molecular sieve synthesized using Example 1 has an aluminum source utilization rate of 90%, a silicon source utilization rate of 76%, a relative crystallinity of 102%, and a particle size of 100 nm; Figure 2 As shown in the SEM image of the Beta molecular sieve synthesized in Example 1, it can be clearly seen that the synthesized molecular sieve has a particle size of 100 nm and a rod shape. In addition, the Beta molecular sieves synthesized in Examples 2 and 3 also have at least the rod-shaped and small-crystal effect shown in the SEM image of Example 1, which will not be described again here.

[0060] Comparative Example 1

[0061] The synthesis method was followed as described in Example 1, but without the addition of ethanol.

[0062] At 45℃, 6g of sodium aluminate was added to 35g of deionized water and stirred until the solution became clear. Then, 20g of sodium hydroxide was added and stirred until the solution became clear again. Next, 3.2g of tetraethylammonium hydroxide was added and stirred for 30 minutes, followed by aging for another 4 hours. The aluminum source, alkali source, template agent, and deionized water were added in a molar ratio of Al₂O₃:0.8Na₂O:0.12 tetraethylammonium hydroxide:60H₂O to obtain intermediate product A1. 125g of water glass and 160g of H₂O were weighed and placed in a beaker. 12g of Beta seed crystals (3.04%) were added under stirring in a 50℃ water bath. After complete dissolution, intermediate product A1 was added, followed by the slow addition of 32.8g of... A 30% sodium aluminate solution was stirred for 30 min to obtain an alkaline gel B2. The molar ratio of the components in the gel reaction mixture was 0.5Na2O:Al2O3:35SiO2:120H2O:0.05tetraethylammonium hydroxide. The gel was then placed in a reaction vessel for dynamic crystallization at 120℃ for 10 h and 160℃ for 18 h. After washing and filtration, the gel was dried at 120℃ for 12 h to obtain Beta molecular sieve 2.

[0063] The aluminum source utilization rate of the Beta molecular sieve synthesized using Comparative Example 1 was 85%, the silicon source utilization rate was 70%, the relative crystallinity of the Beta molecular sieve was 90%, and the particle size was 330 nm. In this example, no ethanol additive was used, as shown in Table 1, which resulted in the synthesized Beta molecular sieve having poor crystallinity or reduced silicon and aluminum utilization.

[0064] Example 2

[0065] This embodiment provides a Beta molecular sieve and its synthesis method, which includes the following steps:

[0066] At 40℃, 5g of sodium aluminate was added to 30g of deionized water and stirred until the solution became clear. Then, 12g of sodium hydroxide was added and stirred until the solution became clear again. Next, 2.4g of tetraethylammonium hydroxide was added and stirred for 30 minutes, followed by aging for another 4 hours. The aluminum source, alkali source, template agent, and deionized water were added in a molar ratio of Al₂O₃:1Na₂O:0.09 tetraethylammonium hydroxide:44H₂O to obtain intermediate product A2. 80g of water glass and 120g of H₂O were weighed and placed in a beaker. Under stirring in a 45℃ water bath, 14g of Beta seed crystals (5.00%) and 3.0g of fatty alcohol polyoxyethylene ether ammonium sulfate were added sequentially. After stirring until completely dissolved, intermediate product A2 was added, followed by the slow addition of 13.6g of... A 30% sodium aluminate solution was stirred for 30 min to obtain an alkaline gel B3. The molar ratio of the components in the gel reaction mixture was 0.45 Na2O:Al2O3:30 SiO2:90 H2O:0.04 tetraethylammonium hydroxide:0.02 fatty alcohol polyoxyethylene ether ammonium sulfate. The gel was then placed in a reactor for dynamic crystallization at 120℃ for 12 h and 140℃ for 24 h. After washing and filtration, the gel was dried at 120℃ for 12 h to obtain Beta molecular sieve 3.

[0067] The Beta molecular sieve synthesized using Example 2 had an aluminum source utilization rate of 91%, a silicon source utilization rate of 88%, a relative crystallinity of 93%, and a particle size of 180 nm.

[0068] Comparative Example 2

[0069] The synthesis method is followed as described in Example 2, but without the addition of fatty alcohol polyoxyethylene ether ammonium sulfate.

[0070] At 40℃, 5g of sodium aluminate was added to 30g of deionized water and stirred until the solution became clear. Then, 12g of sodium hydroxide was added and stirred until the solution became clear again. Next, 2.4g of tetraethylammonium hydroxide was added and stirred for 30 minutes, followed by aging for another 4 hours. The aluminum source, alkali source, template agent, and deionized water were added in a molar ratio of Al₂O₃:1Na₂O:0.09 tetraethylammonium hydroxide:44H₂O to obtain intermediate product A2. 80g of water glass and 120g of H₂O were weighed and placed in a beaker. Under stirring in a 45℃ water bath, 14g of Beta seed crystals (5.05% percentage) were added sequentially and stirred until completely dissolved. Then, intermediate product A2 was added, followed by the slow addition of 13.6g of [unspecified substance]. A 30% sodium aluminate solution was stirred for 30 min to obtain an alkaline gel B4. The molar ratio of the components in the gel reaction mixture was 0.45 Na2O:Al2O3:30 SiO2:90 H2O:0.04 tetraethylammonium hydroxide. The gel was then placed in a reaction vessel for dynamic crystallization at 120℃ for 12 h and 140℃ for 24 h. After washing and filtration, the gel was dried at 120℃ for 12 h to obtain Beta molecular sieve 4.

[0071] The Beta molecular sieve synthesized using Example 2 has an aluminum source utilization rate of 85%, a silicon source utilization rate of 76%, a relative crystallinity of 87%, and a particle size of 470 nm.

[0072] As shown in Table 1, this embodiment did not use the additive fatty alcohol polyoxyethylene ether ammonium sulfate, which resulted in poor crystallinity of the synthesized Beta molecular sieve or low silicon-aluminum utilization rate and poor crystallinity.

[0073] Example 3

[0074] This embodiment provides a Beta molecular sieve and its synthesis method, which includes the following steps:

[0075] At 40℃, 4.5g of sodium aluminate was added to 10g of deionized water and stirred until the solution became clear. Then, 10g of sodium hydroxide was added and stirred until the solution became clear. 2.0g of tetrapropylammonium hydroxide was added and stirred for 30min, followed by aging for 4h. The aluminum source, alkali source, template agent, and deionized water were added in a molar ratio of Al2O3:0.6Na2O:0.05tetraethylammonium hydroxide:30H2O to obtain intermediate product A3. 74.5g of water glass and 74g of H2O were weighed and placed in a beaker. Under stirring in a 45℃ water bath, 12g of Beta seed crystals (6.00%) and 5.0g of ethylene glycol were added sequentially. After stirring until completely dissolved, intermediate product A3 was added, followed by the slow addition of 8g of... A 30% sodium aluminate solution was stirred for 30 min to obtain an alkaline gel B5. The molar ratio of the components in the gel reaction mixture was 0.25 Na2O:Al2O3:26 SiO2:72 H2O:0.02 tetrapropylethyl ammonium hydroxide:0.01 ethylene glycol. The gel was then placed in a reaction vessel for dynamic crystallization at 120℃ for 14 h and 160℃ for 20 h. After washing and filtration, the gel was dried at 120℃ for 12 h to obtain Beta molecular sieve 5.

[0076] The Beta molecular sieve synthesized using Example 3 had an aluminum source utilization rate of 88%, a silicon source utilization rate of 83%, a relative crystallinity of 95%, and a particle size of 150 nm.

[0077] Comparative Example 3

[0078] The synthesis method described in Example 3 was followed, but without the addition of seed crystals.

[0079] At 40℃, 4.5g of sodium aluminate was added to 10g of deionized water and stirred until the solution became clear. Then, 10g of sodium hydroxide was added and stirred until the solution became clear again. Next, 2.0g of tetrapropylammonium hydroxide was added and stirred for 30 minutes, followed by aging for 4 hours. The aluminum source, alkali source, template agent, and deionized water were added in a molar ratio of Al₂O₃:0.6Na₂O:0.05 tetraethylammonium hydroxide:30H₂O to obtain intermediate product A3. 74.5g of water glass and 74g of H₂O were weighed and placed in a beaker. Under stirring in a 45℃ water bath, 12g of tetrapropylammonium hydroxide and... 5.0 g of ethylene glycol was stirred until completely dissolved, and then intermediate product A3 was added. Next, 8 g of 30% sodium aluminate solution was slowly added, and the mixture was stirred for 30 min to obtain alkaline gel B6. The molar ratio of the components in the gel reaction mixture was 0.25 Na2O:Al2O3:26 SiO2:72 H2O:0.25 tetrapropylethyl ammonium hydroxide. The gel was then placed in a reaction vessel for dynamic crystallization at 120℃ for 14 h and 160℃ for 20 h. After washing and filtration, the gel was dried at 120℃ for 12 h to obtain Beta molecular sieve 6.

[0080] The Beta molecular sieve synthesized using Example 3 had an aluminum source utilization rate of 82% and a silicon source utilization rate of 76%. The relative crystallinity of the Beta molecular sieve was 88%, and the amount of template agent used was significantly increased. The particle size was 420 nm. The above examples show that the lack of seed crystals or the seed crystals not conforming to the dosage relationship of this application is evident. In this example, the increased amount of template agent did not achieve the effect of cost reduction, which reflects that the amount of template agent used was reduced by the amount of seed crystals. Seed crystals and template agents have a positive optimization relationship. As shown in Table 1, the increase in the amount of template agent leads to an increase in the amount of tetrapropylethylammonium hydroxide and ethanol. In this application, the amount of tetrapropylethylammonium hydroxide and ethanol exceeding the above-mentioned amounts also affects the crystallinity of this application, resulting in a lower silicon and aluminum utilization rate. The relationship between crystallinity, template agent, and additive dosage indirectly affects the effect of the method of this application. Table 1 below is a comparative analysis of the methods and effects of the examples listed in this application.

[0081] Table 1: Comparative Analysis of the Embodiments and Effects Listed in this Application

[0082]

[0083]

[0084] As can be seen from the comparative data in Table 1, this application has at least one of the following beneficial effects: the amount of the template agent is 2% to 10% of the aluminum source in molar terms; the Beta molecular sieve is rod-shaped or has small crystals; the particle size of the Beta molecular sieve is 100-300 nanometers; the utilization rate of the aluminum source is greater than or equal to 90%; the utilization rate of the silicon source is greater than or equal to 83%; and the crystallinity is greater than or equal to 93%.

[0085] In addition, about 50% to 60% of the cost of the method in this application is the cost of the template agent. By increasing the number of seed crystals, the amount of template agent used can be significantly reduced, which can significantly reduce the synthesis cost compared to the large amount of template agent used in the prior art.

[0086] In summary, the Beta molecular sieve synthesized using the synthesis method of the present invention has the characteristics of high utilization rate of silicon and aluminum sources, reduces the amount of template agent used, and reduces the synthesis cost of Beta molecular sieve.

[0087] Exemplary embodiments of this disclosure have been specifically shown and described above. It should be understood that this disclosure is not limited to the detailed structures, arrangements, or implementations described herein; rather, this disclosure is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A method for synthesizing Beta molecular sieves, the method comprising the following steps: Step 1: Add aluminum source, alkali source, and template agent to the solvent in sequence, stir to form a solution, and continue aging to obtain intermediate product A; Step 2: Take another solvent and add silicon source, seed crystal and additive, stir until completely dissolved, add intermediate product A from step 1, and then add aluminum source to obtain alkaline gel B, wherein the additive is a surfactant. Step 3: Crystallize the alkaline gel B from Step 2 to obtain the Beta molecular sieve. The Beta molecular sieve is rod-shaped, and the crystallization is either dynamic crystallization or segmented crystallization. The amount of template agent used is 2% to 10% of the aluminum source in molar terms. The particle size of the Beta molecular sieve is 100-300 nanometers. The utilization rate of the aluminum source is greater than or equal to 90%. The utilization rate of the silicon source is greater than or equal to 83%. The crystallinity of the Beta molecular sieve is 90%-160%.

2. The method according to claim 1, characterized in that, The crystallinity is 93%-160%, and the solvent is deionized water; In step one, the aluminum source, alkali source, template agent, and deionized water are mixed in a molar ratio of Al2O3 : 0.1~1.2 Na2O : 0.04~0.2 template agent : 40~100 H2O to obtain the intermediate product A. In the entire method, the silicon source, aluminum source, alkali source, template agent, additive, and deionized water are mixed in a molar ratio of 6~80 (SiO2: Al2O3: 0.2~2.0 Na2O: 0.02~0.1, template agent: 0.01~0.06, additive: 80~200 H2O) to obtain the alkaline gel B, wherein the content of seed crystals in the gel is 1wt% to 18wt%.

3. The method according to claim 2, characterized in that, The silicon source is one or a mixture of several of water glass, sodium silicate, solid silica gel and precipitated silica, and the aluminum source is one or a mixture of several of boehmite, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum oxide and aluminum chloride.

4. The method according to claim 2, characterized in that, The alkali source is one or a mixture of two of sodium hydroxide and potassium hydroxide.

5. The method according to claim 2, characterized in that, The template agent is one or a mixture of more than one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

6. The method according to claim 1, characterized in that, The surfactant additive is one or more of fatty alcohol polyoxyethylene ether ammonium sulfate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate, and the seed crystal is a Beta molecular sieve seed crystal, a Y-type zeolite seed crystal, or a combination thereof, and the mass of the seed crystal accounts for 2 wt%-15 wt% of the gel mass.

7. The method according to claim 2, wherein the temperature at which the silicon source, aluminum source, alkali source and water are mixed is 25℃-80℃, the aging time is 2 h-6 h, the crystallization temperature is 110℃-180℃, and the crystallization time is 10 h-96 h.

8. The method according to any one of claims 1-7, characterized in that, The first stage of the segmented crystallization process involves a temperature of 115°C to 140°C and a crystallization time of 10 h to 24 h. The second stage involves a temperature greater than 140°C to 175°C and a crystallization time of 14 h to 72 h.

9. A Beta molecular sieve, characterized in that, Prepared by the method of any one of claims 1-8.

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