Preparation method of beta molecular sieve, beta molecular sieve and application

Abstract

The application discloses a preparation method of a Beta molecular sieve, the Beta molecular sieve and application. The preparation method comprises the following steps: step A, preparing a pseudo-solid phase mixture containing a silicon source, an aluminum source, an inorganic alkali, a first template agent, water and a nonionic polymer; step B, performing a crystallization reaction on the pseudo-solid phase mixture and a second template agent; and step C, washing, centrifuging and calcining the product of the crystallization reaction, thereby obtaining the Beta molecular sieve. The preparation method of the Beta molecular sieve provided by the application adopts a mode of using quaternary ammonium alkali and an organic amine as a co-template agent, and is supplemented with a nonionic polymer, and the Beta molecular sieve is synthesized by using a pseudo-solid phase crystallization method, so that the discharge of a large amount of ammonia-nitrogen wastewater can be avoided, and the use amount of the template agent, especially the quaternary ammonium alkali template agent, is effectively reduced. The Beta molecular sieve prepared has high yield, good crystallinity and narrow particle size distribution range, and the particle size distribution range is between 20 nm and 80 nm.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molecular sieve preparation, and in particular to a preparation method of Beta molecular sieve, Beta molecular sieve and application. BACKGROUND

[0002] Beta molecular sieve is a kind of molecular sieve with three-dimensional twelve-membered ring channels, and the pore size is generally Beta molecular sieve has a unique structure and a high specific surface area. The hydrogen type Beta molecular sieve containing aluminum has better thermal stability, hydrothermal stability and acidity, and exhibits excellent catalytic performance in hydrogenation isomerization, hydrogenation cracking, transalkylation, preparation of isopropylbenzene from benzene and propylene, olefin hydration, aromatic alkylation and toluene disproportionation reactions. However, the traditional micron-sized Beta molecular sieve is not conducive to the diffusion and mass transfer process of macromolecular reactants and products in the catalytic reaction, and therefore, the nano-sized Beta molecular sieve emerges as the times require.

[0003] From 2000 to 2004, Van Grieken et al. reported a method for preparing nano-molecular sieve agglomerates by hydrothermal crystallization of a clear solution system, and then Pham-Huu et al. prepared nano-beta molecular sieve by using carbon nanotubes as inert templates.

[0004] However, the traditional hydrothermal synthesis of nano-Beta molecular sieve requires a large amount of quaternary ammonium base template agent, and the cost of the expensive template agent accounts for about 50% to 70% of the raw material cost in the synthesis process of the molecular sieve. Moreover, a part of the template agent is adsorbed by the molecular sieve and a small amount is decomposed, and the rest is still present in the mother liquor and is not efficiently utilized. In addition, a large amount of water is required as a solvent for preparing the clear solution, the reaction process generates high pressure, and a large amount of strong alkali waste liquid is generated, and finally the yield of the nano-molecular sieve is less than 60%. Therefore, the crystallization mother liquor after the synthesis of the molecular sieve contains a large amount of unreacted raw material components and molecular sieve crystals.

[0005] CN110668459A discloses a nano-Beta molecular sieve with a wide silicon-aluminum ratio range and a preparation method thereof, wherein the silicon-aluminum atomic ratio of the nano-Beta molecular sieve is 6 to 300, and the size of the nano-Beta molecular sieve is 5 to 100 nm. The nano-Beta molecular sieve has a nano size, a wide silicon-aluminum ratio range and a high crystallinity. A method for synthesizing the nano-Beta molecular sieve with a wide silicon-aluminum ratio range in a concentrated system by using amino acids and through two-step crystallization is proposed, and the method can obtain Beta molecular sieve nanocrystals with a high yield and good crystallinity. However, a high proportion of quaternary ammonium base tetraethylammonium hydroxide is still used in the method, the synthesis raw material cost is high, and the large amount of amino acids further increases the preparation cost.

[0006] CN112624147A discloses a method for green synthesis of nanocrystalline Beta molecular sieve. The method synthesizes nanometer Beta molecular sieve with a grain size of about 100 nm by selecting appropriate raw materials such as silicon source, aluminum source, alkali source and seed crystal, optimizing the formula and process, and synthesizing the nanometer Beta molecular sieve without using a template agent. The method reduces product cost and environmental pressure, and further improves product competitiveness. However, the yield of the nanometer Beta molecular sieve obtained by the method is not high, the crystallinity is poor, the strong acid property, thermal stability and hydrothermal stability are greatly affected, and the actual application is seriously limited.

[0007] CN112624142A discloses a preparation method of nanometer hierarchical pore Beta molecular sieve. The method first adopts ball milling to mix solid phase raw materials, and then prepares nanometer hierarchical pore Beta molecular sieve through vapor assisted dry gel transformation. Compared with the existing vapor assisted dry gel transformation method for preparing Beta molecular sieve, the method avoids the process of evaporating the synthesis gel to obtain a dry gel, and directly uses the solid phase reaction mixture obtained by ball milling of tetraethyl ammonium bromide and solid silica gel and the like in vapor assisted transformation, thereby simplifying the synthesis steps and reducing the synthesis cost. At the same time, the migration and dispersion of the solid phase raw materials are promoted due to the presence of steam, thereby preparing nanometer hierarchical pore Beta molecular sieve with small particle size, dispersion and rich intracrystalline mesopores. Moreover, the method reduces the amount of solvent water used, simplifies the synthesis steps and reduces the synthesis cost. However, the method is prone to problems such as insufficient depolymerization of raw materials and uneven mixing of template agent and silicon-aluminum source, which may affect the uniformity of molecular sieve crystallization and ultimately affect the quality of nanometer molecular sieve.

[0008] In summary, in view of the problems of Beta molecular sieve in the prior art, such as low yield, poor crystallinity, large amount of quaternary ammonium base template agent, high cost and large amount of ammonia-nitrogen waste liquid discharge, the present application aims to provide a preparation method of Beta molecular sieve to overcome the above problems in the prior art. SUMMARY

[0009] In view of the above problems in the prior art, the present application provides a preparation method of Beta molecular sieve, Beta molecular sieve and application. The preparation process of the Beta provided by the present application avoids the discharge of a large amount of ammonia-nitrogen wastewater, effectively reduces the amount of template agent, and the Beta prepared has high yield, good crystallinity and narrow particle size distribution range.

[0010] The first aspect of the present application provides a preparation method of Beta molecular sieve, comprising the following steps:

[0011] Step A, preparing a pseudo-solid phase mixture containing a silicon source, an aluminum source, an inorganic base, a first template agent, water and a non-ionic polymer;

[0012] Step B, the pseudo-solid phase mixture and the second template agent are subjected to a crystallization reaction;

[0013] Step C, the product of the crystallization reaction is washed, centrifuged and calcined to obtain the Beta zeolite.

[0014] The preparation method of the Beta zeolite provided by the application adopts a mode of using a first template agent and a second template agent as co-template agents and is assisted by a non-ionic polymer, and synthesis is performed by using a pseudo-solid phase crystallization method, so that the discharge of a large amount of ammonia-nitrogen wastewater can be avoided, and the use amount of the template agent is effectively reduced. The Beta zeolite prepared has a high yield, good crystallinity and a narrow particle size distribution range.

[0015] According to some embodiments of the preparation method, in step A, in the preparation of the pseudo-solid phase mixture, the molar ratio of each material is as follows:

[0016] SiO2:Al2O3:M2O:first template agent:H2O = 1:(0.0083-0.05):(0.1-0.3):(0.05-0.25):(1.5-4); wherein the number of moles of the silicon source is counted based on the number of moles of SiO2 contained therein; the number of moles of the aluminum source is counted based on the number of moles of Al2O3 contained therein; the number of moles of the inorganic base is counted based on the number of moles of the corresponding alkali metal oxide; the number of moles of the first template agent is counted based on the number of moles of itself; and the number of moles of water is counted based on the number of moles of itself.

[0017] For example, in different embodiments of the application, the molar proportion of Al2O3 in the raw materials for preparing the pseudo-solid phase mixture can be 0.0083, 0.01, 0.02, 0.03, 0.04, 0.05, and any value and any combination range between them. The molar proportion of M2O can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, and any value and any combination range between them. The molar proportion of the first template agent can be 0.05, 0.1, 0.15, 0.2, 0.25, and any value and any combination range between them. The molar proportion of H2O can be 1.5, 2, 2.5, 3, 3.5, 4, and any value and any combination range between them.

[0018] According to some embodiments of the preparation method, in step A, in the preparation of the pseudo-solid phase mixture, the molar ratio of each material is as follows:

[0019] SiO2:Al2O3:M2O:first template agent:H2O = 1:(0.0083-0.05):(0.1-0.3):(0.05-0.25):(1.5-4); wherein the number of moles of the silicon source is counted based on the number of moles of SiO2 contained therein; the number of moles of the aluminum source is counted based on the number of moles of Al2O3 contained therein; the number of moles of the inorganic base is counted based on the number of moles of the corresponding alkali metal oxide; the number of moles of the first template agent is counted based on the number of moles of itself; and the number of moles of water is counted based on the number of moles of itself.

[0020] 4); wherein the number of moles of the silicon source is counted by the number of moles of SiO2 contained therein; the number of moles of the aluminum source is counted by the number of moles of Al2O3 contained therein; the number of moles of the inorganic base is counted by the number of moles of the corresponding alkali metal oxide; the number of moles of the template agent is counted by the number of moles of the template agent itself; and the number of moles of water is counted by the number of moles of water itself.

[0021] According to some embodiments of the preparation method of the present application, the first template agent is selected from at least one of quaternary ammonium bases, preferably, the quaternary ammonium base is tetraethylammonium hydroxide.

[0022] According to some embodiments of the preparation method of the present application, the second template agent is selected from at least one of organic amines.

[0023] According to preferred embodiments of the preparation method of the present application, the organic amine is selected from at least one of triethylamine, n-butylamine and ethylenediamine.

[0024] According to some embodiments of the preparation method of the present application, the weight of the non-ionic polymer accounts for 1% to 6% of the weight of the pseudo-solid phase mixture. For example, the weight of the non-ionic polymer accounts for 1%, 2%, 3%, 4%, 5%, 6% of the weight of the pseudo-solid phase mixture, and any value and any combination range therebetween.

[0025] According to preferred embodiments of the preparation method of the present application, the weight of the non-ionic polymer accounts for 2% to 4% of the weight of the pseudo-solid phase mixture.

[0026] According to some embodiments of the preparation method of the present application, in step A, the conditions for preparing the pseudo-solid phase mixture include stirring and aging at 70°C to 90°C, and evaporating to remove water.

[0027] According to some embodiments of the preparation method of the present application, in step B, the conditions for the crystallization reaction include a temperature of 140°C to 160°C and a time of 1 day to 7 days.

[0028] In different embodiments of the present application, the pseudo-solid phase mixture and the organic amine are placed in the inner liner of the crystallization kettle separately to perform the crystallization reaction, wherein the organic amine is in the form of gas phase transmission to assist the pseudo-solid phase mixture raw material to crystallize.

[0029] According to some embodiments of the preparation method of the present application, in step C, the conditions for the calcination process include a temperature of 500°C to 600°C and calcination in air for 3h to 6h.

[0030] According to some embodiments of the preparation method of the present application, the process further comprises a drying process before the calcination, and the temperature of the drying process is 50°C to 80°C.

[0031] According to some embodiments of the preparation method, the silicon source is selected from at least one of silica sol, tetraethyl orthosilicate and white carbon black.

[0032] According to some embodiments of the preparation method, the aluminum source is selected from at least one of aluminum sulfate, aluminum nitrate and pseudoboehmite.

[0033] According to some embodiments of the preparation method, the inorganic base is selected from sodium hydroxide and / or potassium hydroxide.

[0034] According to some embodiments of the preparation method, the non-ionic polymer is selected from at least one of non-ionic water-soluble polymers with an average relative molecular mass ≤50000 (i.e. Average Mn ≤50000).

[0035] According to preferred embodiments of the preparation method, the non-ionic water-soluble polymer is selected from at least one of polyethylene glycol, polyvinyl alcohol, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) and poly(oxyethylene)-poly(oxypropylene) ether block copolymer (F127).

[0036] In the preparation method of the Beta provided by the present application, the quaternary ammonium base is used as the first template agent, the organic amine is used as the second template agent in the form of a co-template agent, and the synthesis is performed with the aid of a non-ionic polymer and a pseudo-solid phase crystallization method. The organic amine is used as the second template agent in the form of a gas phase transmission, which increases the contact area with the reaction raw materials, promotes uniform nucleation, and effectively reduces the amount of the quaternary ammonium base used. The pseudo-solid phase crystallization of the pseudo-solid phase mixture and the second template agent reduces the ammonia-nitrogen wastewater, and the poor flow characteristics thereof also inhibit the growth of the molecular sieve crystal grains, playing a physical "limitation" role. The non-ionic polymer can form a reticular structure in the dry gel, playing a chemical "limitation" role. The two kinds of "limitation" jointly act on the zeolite crystal nucleus to grow in the nanoscale space, forming nanocrystal grains, and the use of the double templates further strengthens the crystallinity of the product, so that a high-yield nanometer Beta molecular sieve is finally obtained.

[0037] The present application provides a Beta molecular sieve obtained by the above preparation method.

[0038] The Beta molecular sieve provided by the present application has high yield, good crystallinity, and a narrow particle size distribution range of 20nm-80nm.

[0039] The third aspect of the present application provides a preparation method of the above-mentioned Beta molecular sieve or application of the above-mentioned Beta molecular sieve in catalysts and adsorbents. Preferably, the application is in a hydrogen isomerization catalyst, a hydrocracking catalyst, a transalkylation catalyst, a catalyst for preparing cumene from benzene and propylene, an olefin hydration catalyst, an aromatic alkylation catalyst and a toluene disproportionation catalyst.

[0040] Advantages of the present application:

[0041] The preparation method of the Beta molecular sieve provided by the present application adopts the mode of using quaternary ammonium base and organic amine as co-template agents, and is supplemented with non-ionic polymer, and utilizes pseudo-solid phase crystallization method for synthesis, so that the discharge of a large amount of ammonia-nitrogen wastewater can be avoided, and the amount of template agents, especially quaternary ammonium base template agents, can be effectively reduced.

[0042] The Beta molecular sieve prepared by the present application has high yield, good crystallinity and narrow particle size distribution range, and the particle size distribution range is between 20nm and 80nm. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is an X-ray diffraction spectrum (XRD spectrum) of the Beta-1 sample in Example 1 of the present application.

[0044] Figure 2 It is a scanning electron microscope (SEM) photograph of the Beta-1 sample in Example 1 of the present application.

[0045] Figure 3 It is an XRD spectrum of the Beta-2 sample in Example 2 of the present application.

[0046] Figure 4 It is an SEM photograph of the Beta-2 sample in Example 2 of the present application.

[0047] Figure 5 It is an SEM photograph of the Beta-3 in Comparative Example 1 of the present application.

[0048] Figure 6 It is an SEM photograph of the Beta-4 in Comparative Example 2 of the present application.

[0049] Figure 7 It is an XRD spectrum of the Beta-6 in Comparative Example 4 of the present application.

[0050] Figure 8 It is an XRD spectrum of the Beta-7 in Comparative Example 5 of the present application. DETAILED DESCRIPTION

[0051] In order to make the present application easier to understand, the present application will be described in detail below in combination with embodiments and drawings, and these embodiments are only illustrative and do not limit the application range of the present application.

[0052] The test method of the present application and the equipment used in the test are as follows:

[0053] (1) X-ray diffraction spectrum: tested by Bruker D8 Advance SS, the scanning range of the test process is 5°-50°, the scanning speed is 6° / min, Cu target is used in the XRD spectrum test process, Cu Kα,

[0054] (2) Scanning electron microscope photo: grain size observation and morphology analysis are carried out by Tecnai F20 scanning electron microscope.

[0055] The various reagents used in the following examples and comparative examples are all commercially available.

[0056]

Example 1

[0057] Preparation of nano-Beta molecular sieve:

[0058] Dissolve aluminum nitrate and sodium hydroxide in water in a certain proportion, stir for 10 min, and obtain solution A.

[0059] Mix silica sol and tetraethylammonium hydroxide in a certain proportion, stir for 20 min, and obtain solution B.

[0060] Dissolve non-ionic polymer F127 in a certain amount of water to obtain solution C.

[0061] Slowly add solution A to solution B, stir until uniform, add solution C, stir and age at 90℃, and evaporate water to a water-silicon molar ratio of 3 (H2O / SiO2=3) at the same time to obtain a pseudo-solid phase mixture.

[0062] Separately place the pseudo-solid phase mixture and 10 mL of triethylamine in the inner liner of the crystallization kettle, and crystallize at 140℃ for 3 days. After the crystallization is completed, the product is washed with deionized water and centrifuged until the pH is neutral, and then dried at 80℃ in an air atmosphere to obtain Beta molecular sieve raw powder.

[0063] Finally, calcine at 550℃ in air for 4h to obtain the high-yield nano-Beta molecular sieve, which is denoted as sample Beta-1.

[0064] The molar ratio of each effective component in the pseudo-solid phase mixture is SiO2:Al2O3:Na2O: tetraethylammonium hydroxide:H2O = 1:0.025:0.18:0.15:3, and the weight of F127 is 3wt% of the weight of the pseudo-solid phase mixture.

[0065] As shown in Figure 1 , sample Beta-1 is a pure-phase, high-crystallinity Beta molecular sieve. As shown inFigure 2 As shown, the grain size of sample Beta-1 is between 20 nm and 80 nm.

[0066] In this embodiment, the weight ratio of sample Beta-1 to the SiO2 and Al2O3 contained in the feed is 86%. According to the formula shown in equation (1):

[0067]

[0068] As calculated by the above formula (1), the solid phase yield in this embodiment is as high as 86%.

[0069]

Example 2

[0070] Preparation of nano-Beta molecular sieves:

[0071] Aluminum sulfate and sodium hydroxide are dissolved in water in a certain proportion and stirred for 10 minutes to obtain solution A.

[0072] Tetraethyl orthosilicate and tetraethylammonium hydroxide were mixed in a certain proportion and stirred for 20 minutes to obtain solution B.

[0073] Polyethylene glycol (number average molecular weight Mn = 20000) was dissolved in a certain amount of water to obtain solution C.

[0074] Slowly add solution A to solution B and stir until homogeneous. Then add solution C and stir and age at 90°C while evaporating water until the water-to-silicon ratio is 1.5 (H2O / SiO2 = 1.5), thus obtaining a pseudo-solid phase mixture.

[0075] The pseudo-solid mixture and 10 mL of ethylenediamine were placed separately in the liner of a crystallization vessel and crystallized at 140 °C for 3 days. After crystallization, the product was washed with deionized water, centrifuged until pH neutral, and then dried at 80 °C in air to obtain Beta molecular sieve raw powder.

[0076] Then, the sample was calcined at 550℃ in air for 4 hours to obtain high-yield nano-Beta molecular sieves, denoted as sample Beta-2.

[0077] The molar ratio of each effective component in the pseudo-solid mixture is SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.02:0.1:0.25:1.5, and the weight of polyethylene glycol is 5 wt% of the weight of the pseudo-solid mixture.

[0078] like Figure 3 As shown, sample Beta-2 is a pure-phase, highly crystalline Beta molecular sieve. Figure 4 As shown, the grain size of sample Beta-2 is between 20 nm and 80 nm.

[0079] The solid phase yield of this example is up to 83% calculated from formula (1).

[0080]

Example 3

[0081] The process is the same as that of Example 1, except that the molar ratio of each effective component in the pseudo-solid phase mixture is SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.0083:0.1:0.1:2.

[0082] It is determined that the solid phase yield of this example is 85%, and the product particle size is between 20 nm and 80 nm.

[0083]

Example 4

[0084] The process is the same as that of Example 1, except that the molar ratio of each effective component in the pseudo-solid phase mixture is SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.05:0.3:0.05:4.

[0085] It is determined that the solid phase yield of this example is 82%, and the product particle size is between 20 nm and 80 nm.

[0086]

Example 5

[0087] The process is the same as that of Example 1, except that the weight of F127 in the pseudo-solid phase mixture is 1% of the weight of the pseudo-solid phase mixture.

[0088] It is determined that the solid phase yield of this example is 86%, and the product particle size is between 40 nm and 100 nm.

[0089]

Example 6

[0090] The process is the same as that of Example 1, except that the weight of F127 in the pseudo-solid phase mixture is 6% of the weight of the pseudo-solid phase mixture.

[0091] It is determined that the solid phase yield of this example is 85%, and the product particle size is between 20 nm and 80 nm.

[0092]

Comparative Example 1

[0093] The comparative example adopts a conventional hydrothermal crystallization process, and the process for preparing nano-Beta molecular sieve is as follows:

[0094] Dissolve aluminum nitrate and sodium hydroxide in water in a certain proportion, stir for 10 min, and obtain solution A.

[0095] Mix silica sol and tetraethylammonium hydroxide in a certain proportion, stir for 20 min, and obtain solution B.

[0096] Solution C was prepared by dissolving non-ionic polymer F127 in a certain amount of water.

[0097] Solution A was slowly added to solution B and stirred until uniform, and then solution C was added, and the mixture was stirred and aged at 90°C to obtain a mixture.

[0098] The obtained mixture and 10 mL of triethylamine were separately placed in the inner liner of a crystallization kettle, and crystallization was carried out at 140°C for 3 days. After crystallization, the product was washed with deionized water, centrifuged to neutral pH, and then dried at 80°C in an air atmosphere to obtain Beta molecular sieve crude powder.

[0099] Then, the Beta molecular sieve was obtained by calcination at 550°C in air for 4h, and was recorded as sample Beta-3.

[0100] In the mixture, the molar ratio of each effective component was SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.025:0.18:0.15:25, and the weight of F127 was 3wt% of the weight of the mixture.

[0101] The conventional hydrothermal synthesis method was used in the present comparative example, and the yield of the obtained product could reach 78%. However, as shown in Table 1, the particle size of sample Beta-3 reached 2 μm, and the distribution was uneven. The water content in the crystallization mixture was high, which seriously affected the particle size of the product. That is, the water content was increased, and the particle size of the product was obviously increased. Figure 5

[0102]

Comparative Example 2

[0103] Preparation of nano-Beta molecular sieve:

[0104] Aluminum nitrate and sodium hydroxide were dissolved in water in a certain proportion, and stirred for 10 min to obtain solution A.

[0105] Silica sol and tetraethylammonium hydroxide were mixed in a certain proportion, and stirred for 20 min to obtain solution B.

[0106] Solution A was slowly added to solution B and stirred until uniform, and then aged at 90°C while evaporating water until the water to silica ratio was 3 (H2O / SiO2 = 3) to obtain a pseudo-solid phase mixture.

[0107] The pseudo-solid phase mixture and 10 mL of triethylamine were separately placed in the inner liner of a crystallization kettle, and crystallization was carried out at 140°C for 3 days. After crystallization, the product was washed with deionized water, centrifuged to neutral pH, and then dried at 80°C in an air atmosphere to obtain Beta molecular sieve crude powder.

[0108] Then, the Beta molecular sieve was obtained by calcination at 550°C in air for 4h, and was recorded as sample Beta-4.​

[0109] The molar ratio of each effective component in the quasi-solid phase mixture is SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.025:0.18:0.15:3.

[0110] No nonionic polymer is added in the present comparative example. As shown in Table 1, the particle size of the sample Beta-4 prepared in the present comparative example is between 100 nm and 300 nm. Figure 6

[0111] It can be seen that the addition of the nonionic polymer in the crystallization mixture effectively reduces the particle size of the product.

[0112]

Comparative Example 3

[0113] Preparation of nano-Beta molecular sieve:

[0114] Aluminum nitrate and sodium hydroxide were dissolved in water in a certain proportion, and stirred for 10 min to obtain solution A.

[0115] Silica sol and tetraethylammonium hydroxide were mixed in a certain proportion, and stirred for 20 min to obtain solution B.

[0116] The nonionic polymer F127 was dissolved in a certain amount of water to obtain solution C.

[0117] Solution A was slowly added to solution B, and stirred until uniform. Solution C was added, and stirred and aged at 90°C while evaporating water until the water to silica ratio was 3 (H2O / SiO2 = 3) to obtain a quasi-solid phase mixture.

[0118] The quasi-solid phase mixture and 10 mL of distilled water were separately placed in the inner liner of the crystallization kettle, and crystallized at 140°C for 3 days. After the crystallization was completed, the product was washed with deionized water, centrifuged to neutral pH, and then dried at 80°C in an air atmosphere to obtain Beta molecular sieve raw powder.

[0119] Then, the Beta molecular sieve was obtained by calcining at 550°C in air for 4 h, and was denoted as sample Beta-5.

[0120] The molar ratio of each effective component in the quasi-solid phase mixture is SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.025:0.18:0.15:3, and the weight of F127 is 3 wt% of the weight of the quasi-solid phase mixture.

[0121] In the present comparative example, no organic amine was added as a template. The solid phase yield of the sample Beta-5 prepared in the present comparative example was only 68%.

[0122] ​Therefore, organic amines, as one of the co-templating agents, can effectively improve the yield of nano-Beta molecular sieves.

[0123] Comparative Example 4

[0124] Preparation of nano-Beta molecular sieves:

[0125] Aluminum nitrate and sodium hydroxide are dissolved in water in a certain proportion and stirred for 10 minutes to obtain solution A.

[0126] Silica sol, 10 mL of triethylamine, and tetraethylammonium hydroxide were mixed in a certain proportion and stirred for 20 min to obtain solution B.

[0127] Solution C was prepared by dissolving nonionic polymer F127 in a certain amount of water.

[0128] Slowly add solution A to solution B and stir until homogeneous. Then add solution C and stir and age at 90°C while evaporating water until the water-to-silicon ratio is 3 (H2O / SiO2 = 3) to obtain a mixture.

[0129] The resulting mixture was placed in the lining of a crystallization vessel and crystallized at 140°C for 3 days. After crystallization, the product was washed with deionized water, centrifuged until pH neutral, and then dried at 80°C in air to obtain Beta molecular sieve raw powder.

[0130] Then, it was calcined at 550℃ in air for 4 hours to obtain Beta molecular sieve, which was designated as sample Beta-6.

[0131] The molar ratio of each effective component in the mixture is SiO2:Al2O3:Na2O:tetraethylammonium hydroxide:H2O = 1:0.025:0.18:0.15:25, and the weight of F127 is 3wt% of the weight of the pseudo-solid mixture.

[0132] like Figure 7 As shown in the figure, the XRD pattern of sample Beta-6 prepared in this comparative example shows that sample Beta-6 contains not only Beta molecular sieves but also a large number of impurity crystals. In other words, the addition of organic amines and quaternary ammonium bases to the crystallization mixture leads to the formation of impurity phases, making it impossible to obtain pure phase Beta molecular sieves and affecting the purity of the product.

[0133] Comparative Example 5

[0134] Preparation of nano-Beta molecular sieves:

[0135] Aluminum nitrate and sodium hydroxide are dissolved in water in a certain proportion and stirred for 10 minutes to obtain solution A.

[0136] Mix silica sol and deionized water in a certain proportion and stir for 20 minutes to obtain solution B.

[0137] Dissolve non-ionic polymer F127 in a certain amount of water to obtain solution C.

[0138] Slowly add solution A into solution B, stir until uniform, add solution C, stir and age at 90℃, evaporate water until the water to silica ratio is 3 (H2O / SiO2=3) to obtain a pseudo-solid phase mixture.

[0139] Separately place the pseudo-solid phase mixture and 10 mL of triethylamine in the inner liner of a crystallization kettle, crystallize at 140℃ for 3 days, after crystallization, wash the product with deionized water, centrifuge until the pH is neutral, and then dry at 80℃ in an air atmosphere to obtain Beta molecular sieve crude powder.

[0140] Then calcine at 550℃ in air for 4h to obtain sample Beta-7.

[0141] The molar ratio of each effective component in the pseudo-solid phase mixture is SiO2:Al2O3:Na2O:H2O=1:0.025:0.18:3, and the weight of F127 is 3wt% of the weight of the pseudo-solid phase mixture.

[0142] In the present comparative example, no quaternary ammonium base tetraethylammonium hydroxide is added as one of the co-templates. As shown in Table 1, the sample Beta-7 prepared in the present comparative example is not crystallized, and is in an amorphous phase. Figure 8

[0143] It can be seen that the quaternary ammonium base can significantly affect the crystallinity of the product, and when no quaternary ammonium base is added, the uncrystallization phenomenon occurs.

[0144] The above only describes preferred examples of the present application. It should be noted that for those skilled in the art, under the technical inspiration provided by the present application, other equivalent variants and improvements as common knowledge in the art can also be made, and should also be considered as the protection scope of the present application.​

Claims

1. A method for preparing a Beta molecular sieve, comprising the following steps: Step A, preparing a pseudo-solid phase mixture containing a silicon source, an aluminum source, an inorganic base, a first template agent, water and a nonionic water-soluble polymer; Step B, performing a crystallization reaction on the pseudo-solid phase mixture and a second template agent; Step C, washing, centrifuging and calcining the product of the crystallization reaction to obtain the Beta molecular sieve; the first template agent is selected from at least one of quaternary ammonium bases; the second template agent is selected from at least one of organic amines; in Step A, the molar ratio of each material in the pseudo-solid phase mixture is as follows: SiO2:Al2O3:M2O:first template agent:H2O = 1:(0.0083-0.05):(0.1-0.3):(0.05-0.25):(1.5-4); wherein the molar number of the silicon source is calculated based on the molar number of SiO2 contained therein; the molar number of the aluminum source is calculated based on the molar number of Al2O3 contained therein; the molar number of the inorganic base is calculated based on the molar number of the corresponding alkali metal oxide M2O; the molar number of the first template agent is calculated based on its own molar number; and the molar number of water is calculated based on its own molar number.

2. The production method according to claim 1, characterized by, in Step A, the molar ratio of each material in the pseudo-solid phase mixture is as follows: SiO2:Al2O3:M2O:first template agent:H2O = 1:(0.0083-0.05):(0.1-0.3):(0.05-0.25):(1.5-4); wherein the molar number of the silicon source is calculated based on the molar number of SiO2 contained therein; the molar number of the aluminum source is calculated based on the molar number of Al2O3 contained therein; the molar number of the inorganic base is calculated based on the molar number of the corresponding alkali metal oxide M2O; the molar number of the first template agent is calculated based on its own molar number; and the molar number of water is calculated based on its own molar number.

3. The production method according to claim 1 or 2, characterized by, the quaternary ammonium base is tetraethylammonium hydroxide; and / or the organic amine is selected from at least one of triethylamine, n-butylamine and ethylenediamine.

4. The production method according to claim 1 or 2, characterized by, the nonionic water-soluble polymer accounts for 1%-6% of the weight of the pseudo-solid phase mixture.

5. The production method according to claim 4, characterized by, the nonionic water-soluble polymer accounts for 2%-4% of the weight of the pseudo-solid phase mixture.

6. The production method according to claim 1 or 2, characterized by, in Step A, the conditions for preparing the pseudo-solid phase mixture include stirring and aging at 70-90°C and evaporating water; and / or in Step B, the conditions for the crystallization reaction include a temperature of 140-160°C and a time of 1-7 days.

7. The production method according to claim 1 or 2, characterized by, in Step C, the conditions for the calcination process include a temperature of 500-600°C, calcination in air for 3-6 hours; and / or a drying process is further included before the calcination, and the temperature of the drying process is 50-80°C.

8. The production method according to claim 1 or 2, characterized by, the silicon source is selected from at least one of silica sol, tetraethyl orthosilicate and white carbon black; and / or the aluminum source is selected from at least one of aluminum sulfate, aluminum nitrate and pseudo-boehmite; and / or the inorganic base is selected from sodium hydroxide and / or potassium hydroxide; and / or the nonionic water-soluble polymer is selected from at least one of nonionic water-soluble polymers with an average relative molecular mass of ≤50000.

9. The production method according to claim 1 or 2, characterized by, The non-ionic water-soluble polymer is selected from at least one of polyethylene glycol, polyvinyl alcohol, polyethylene oxide-polypropylene oxide-polyethylene oxide tri-block copolymer, and polyoxyethylene polyoxypropylene ether block copolymer.

10. A Beta zeolite prepared by the method of any one of claims 1 to 9.

11. Use of the Beta zeolite of claim 10 in catalysts and adsorbents.

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