Beta zeolite agglomerates, methods of making and using the same

Abstract

The present application relates to the field of molecular sieve, and particularly provides a Beta molecular sieve aggregate, a preparation method and application thereof. The preparation method of the Beta molecular sieve aggregate comprises the following steps: preparing an initial Beta molecular sieve; adding a first acid aqueous solution and an organic template into an initial aluminum solution, adjusting pH, and sequentially performing a first pre-crystallization treatment and a crystallization treatment to obtain the initial Beta molecular sieve; performing a recrystallization treatment on the initial Beta molecular sieve; mixing the initial Beta molecular sieve with polyvinyl alcohol, stirring the mixture in a second acid aqueous solution at 20-150 DEG C for 0-2 hours (0 hours is not included), aging for 2-48 hours, performing a second pre-crystallization for 1-48 hours, and then performing a crystallization treatment again to obtain the Beta molecular sieve aggregate. The Beta molecular sieve aggregate obtained by the method has a high specific surface area and mesopore area, and the mesopore diameter is concentrated in 4.5-7.5 nm.

Description

Technical Field

[0001] This invention relates to the field of molecular sieves, and more specifically, to a Beta molecular sieve aggregate, its preparation method, and its application. Background Technology

[0002] Over the past few decades, molecular sieves, as porous materials, have been widely used in catalysis, adsorption, and ion exchange. In chemical catalysis and materials science, Beta molecular sieves have become a research and application hotspot due to their unique three-dimensional pore structure, excellent thermal stability, and acidity. These molecular sieves are widely used in petrochemicals, environmental protection, and the synthesis of fine chemicals. However, the small pore size of traditional Beta molecular sieves limits their efficiency in processing large molecular reactants. To address this issue, scientists have begun exploring the preparation of Beta molecular sieves with high mesoporosity to improve their catalytic efficiency and expand their application range.

[0003] In the preparation of high-mesoporous Beta zeolites, early methods mainly relied on traditional techniques such as the use of organic templates. However, these methods often sacrificed the structural stability and activity of the material while increasing the pore size. To overcome these challenges, recent research has focused on selecting more suitable materials and improving synthesis conditions. For example, by introducing specific silicon sources or using a dual-template method, the pore size of Beta zeolites can be increased while maintaining structural stability. However, a method for preparing zeolites that can simultaneously increase specific surface area, mesopore area, and mesopore size is currently lacking.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing Beta molecular sieve aggregates, which can effectively improve the specific surface area, mesopore area, and mesopore diameter of Beta molecular sieves.

[0006] A second objective of this invention is to provide a Beta molecular sieve aggregate prepared by the above-described preparation method.

[0007] A third objective of this invention is to provide an application of the above-mentioned Beta molecular sieve aggregates in catalysis or automotive exhaust treatment.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] In a first aspect, the present invention provides a method for preparing Beta molecular sieve aggregates, comprising:

[0010] S1. Preparation of initial Beta molecular sieve: The first acid aqueous solution and organic template agent are added to the initial aluminum solution, the pH is adjusted to 11-13.5, and after a pre-crystallization treatment, the original solution is obtained; the silicon source is mixed with the original solution, and after crystallization treatment, the initial Beta molecular sieve is obtained; the initial aluminum solution includes alkali, aluminum source and water;

[0011] S2. Initial Beta molecular sieve recrystallization treatment: The initial Beta molecular sieve and polyvinyl alcohol are mixed and stirred in a second acid aqueous solution at 20-150°C for 0-2 hours (excluding 0 hours), aged for 2-48 hours, and then pre-crystallized at 50-220°C for 1-48 hours before being crystallized again to obtain Beta molecular sieve aggregates.

[0012] As a further preferred technical solution, the concentration of the first acid aqueous solution is 0.1-5 mol / L, the concentration of the organic template agent is 0.1-0.5 mol / L, and the concentration of the initial aluminum solution is 0.1-5 mol / L;

[0013] Preferably, the first pre-crystallization treatment is performed at a temperature of 100–180°C for 12–24 hours.

[0014] As a further preferred technical solution, the organic template agent includes at least one of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride, tetraethylammonium fluoride, tetrapropylammonium hydroxide, tetramethylammonium hydroxide, tetramethylammonium bromide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide;

[0015] Preferably, the reaction system for the crystallization treatment has the following molar ratio composition: SiO2 / Al2O3 = 20-600, Na2O / SiO2 = 0.01-0.1, TEAOH / SiO2 = 0.01-0.05, H2O / SiO2 = 2-5.

[0016] As a further preferred technical solution, the crystallization treatment is performed at a temperature of 120–180°C for 24–48 hours.

[0017] As a further preferred technical solution, the silicon source includes at least one of silica sol, fumed silica, silica gel particles, white carbon black, and tetraethyl orthosilicate, preferably silica gel particles with a particle size of 20 to 500 mesh.

[0018] Preferably, the alkali comprises an inorganic alkali, and the inorganic alkali is preferably sodium hydroxide and / or potassium hydroxide;

[0019] Preferably, the aluminum source includes at least one of aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum isopropoxide, or aluminum sec-butoxide.

[0020] As a further preferred technical solution, the first acid and the second acid are each independently selected from at least one of fluorosilicic acid, sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, phosphoric acid, formic acid, acetic acid, or acetic acid;

[0021] Preferably, the first acid is fluorosilicic acid, and the second acid is acetic acid or oxalic acid;

[0022] Preferably, the concentration of the second acid aqueous solution is 0.1 mol / L to 5.0 mol / L.

[0023] As a further preferred technical solution, the mass ratio of the initial Beta molecular sieve, the second acid, and the polyvinyl alcohol is 1:5-20:0.1-1.

[0024] As a further preferred technical solution, the recrystallization treatment is performed at a temperature of 120–220°C for 1–72 hours.

[0025] Secondly, the present invention provides a Beta molecular sieve aggregate prepared by the above-described preparation method, wherein the Beta molecular sieve aggregate has a specific surface area of ​​650–1000 m². 2 / g, mesopore area is 400-800m² 2 / g, with mesopore diameters of 4.5–7.5 nm.

[0026] Thirdly, the present invention provides an application of the above-mentioned Beta molecular sieve aggregates in catalysis or automotive exhaust treatment.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The method for preparing Beta molecular sieve aggregates provided by this invention involves treating the initial Beta molecular sieve with an aqueous solution of fluorosilicic acid, and simultaneously subjecting the initial Beta molecular sieve to stirring, secondary pre-crystallization, and re-crystallization. The resulting Beta molecular sieve aggregates exhibit a high specific surface area (650–1000 m²). 2 / g) and mesopore area (400~800m) 2 The high mesoporous Beta molecular sieve exhibits superior performance in applications such as catalyst supports and adsorbents (e.g., automotive exhaust gas adsorption). Attached Figure Description

[0029] Figure 1 The image shows the XRD pattern of the Beta molecular sieve aggregates obtained in Example 1.

[0030] Figure 2 The image shows the pore size distribution curve of the Beta molecular sieve aggregates obtained in Example 1.

[0031] Figure 3 This is a SEM image of the Beta molecular sieve aggregates obtained in Example 1. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply.

[0033] On one hand, the present invention provides a method for preparing Beta molecular sieve aggregates, comprising:

[0034] S1. Preparation of initial Beta molecular sieve: The first acid aqueous solution and organic template agent are added to the initial aluminum solution, the pH is adjusted to 11-13.5, and after a pre-crystallization treatment, the original solution is obtained; the silicon source is mixed with the original solution, and after crystallization treatment, the initial Beta molecular sieve is obtained; the initial aluminum solution includes alkali, aluminum source and water;

[0035] S2. Initial Beta molecular sieve recrystallization treatment: The initial Beta molecular sieve and polyvinyl alcohol are mixed and stirred in a second acid aqueous solution at 20-150°C for 0-2 hours (excluding 0 hours), aged for 2-48 hours, and then pre-crystallized at 50-220°C for 1-48 hours before being crystallized again to obtain Beta molecular sieve aggregates.

[0036] This preparation method involves treating the initial Beta molecular sieve with an aqueous solution of fluorosilicic acid, followed by stirring, secondary pre-crystallization, and re-crystallization. The resulting Beta molecular sieve aggregates exhibit a high specific surface area (650–1000 m²). 2 / g) and mesopore area (400~800m) 2 The high mesoporous Beta molecular sieve exhibits superior performance in applications such as catalyst supports and adsorbents (e.g., automotive exhaust gas adsorption).

[0037] Further, the concentration of the first acid aqueous solution is 0.1–5 mol / L, the concentration of the organic template agent is 0.1–0.5 mol / L, and the concentration of the initial aluminum solution is 0.1–5 mol / L. The concentration of the first acid aqueous solution includes, but is not limited to, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 mol / L. The concentration of the organic template agent includes, but is not limited to, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5 mol / L. The concentration of the initial aluminum solution includes, but is not limited to, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 mol / L.

[0038] Furthermore, the pH in S1 includes, but is not limited to, 11, 11.5, 12, 12.5, 13, or 13.5.

[0039] Further, the first pre-crystallization treatment is performed at a temperature of 100–180°C for 12–24 hours. The above treatment temperatures include, but are not limited to, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180°C. The above treatment times include, but are not limited to, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 hours.

[0040] Furthermore, the reaction system for the crystallization treatment has the following molar ratio composition: SiO2 / Al2O3 = 20-600, Na2O / SiO2 = 0.01-0.1, TEAOH / SiO2 = 0.01-0.05, H2O / SiO2 = 2-5. The molar ratio of SiO2 to Al2O3 includes, but is not limited to, 20, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, or 600; the molar ratio of Na2O to SiO2 includes, but is not limited to, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1; the molar ratio of TEAOH / SiO2 includes, but is not limited to, 0.01, 0.02, 0.03, 0.04, or 0.05; and the molar ratio of H2O to SiO2 includes, but is not limited to, 2, 2.5, 3, 3.5, 4, 4.5, or 5.

[0041] Further, the crystallization treatment is performed at a temperature of 120–180°C for 24–48 hours. The aforementioned temperatures include, but are not limited to, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180°C, and the aforementioned times include, but are not limited to, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, or 48 hours.

[0042] Further, the silicon source includes at least one of silica sol, fumed silica, silica gel particles, silica fume, and tetraethyl orthosilicate, preferably silica gel particles with a particle size of 20-500 mesh. The silica sol includes an alkaline silica sol with a silica content of 30 wt.% and an alkaline silica sol with a silica content of 40 wt.%. The aforementioned alkaline silica sol with a silica content of 30 wt.% includes Ludox AS-30 and / or Ludox HS-30, with Ludox AS-30 having a pH of 9.4 and Ludox HS-30 having a pH of 9.8. The aforementioned alkaline silica sol with a silica content of 40 wt.% includes Ludox AS-40 and / or Ludox HS-40, with Ludox AS-40 having a pH of 9.4 and Ludox HS-40 having a pH of 9.5.

[0043] Preferably, the alkali comprises an inorganic alkali, which is preferably sodium hydroxide and / or potassium hydroxide, and more preferably sodium hydroxide.

[0044] Preferably, the aluminum source includes at least one of aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum isopropoxide, or aluminum sec-butoxide.

[0045] Furthermore, the first acid and the second acid are each independently selected from at least one of fluorosilicic acid, sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, phosphoric acid, formic acid, acetic acid, or acetic acid.

[0046] Preferably, the first acid is fluorosilicic acid, and the second acid is acetic acid or oxalic acid.

[0047] Preferably, the concentration of the second acid aqueous solution is 0.1 mol / L to 5.0 mol / L. The concentration of the second acid includes, but is not limited to, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 mol / L.

[0048] Further, the mass fraction of acetic acid in the mixed aqueous solution is 1% to 20%, preferably 2% to 15%, and more preferably 2% to 10%. The mass fraction of acetic acid in the above-mentioned mixed aqueous solution includes, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0049] Further, the mass ratio of the initial Beta molecular sieve, the second acid, and the polyvinyl alcohol is 1:5 to 20:0.1 to 1. The above mass ratios include, but are not limited to, 1:5:0.1, 1:6:0.5, 1:7:1, 1:8:0.2, 1:9:0.7, 1:10:1, 1:11:0.3, 1:12:0.5, 1:13:0.8, 1:14:0.9, 1:15:1, 1:16:0.1, 1:17:0.4, 1:18:0.5, 1:19:0.2, or 1:20:1.

[0050] Further, the recrystallization treatment is performed at a temperature of 120–220°C for 1–72 hours. The aforementioned temperatures include, but are not limited to, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, or 220°C, and the aforementioned times include, but are not limited to, 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, or 72 hours.

[0051] Further, the organic template agent includes at least one selected from tetraethylammonium hydroxide (TEAOH), tetraethylammonium bromide, tetraethylammonium chloride, tetraethylammonium fluoride, tetrapropylammonium hydroxide, tetramethylammonium hydroxide, tetramethylammonium bromide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide. Preferably, the organic template agent is tetraethylammonium hydroxide (TEAOH), tetraethylammonium bromide, tetraethylammonium chloride, or tetraethylammonium fluoride.

[0052] On the other hand, the present invention provides a Beta molecular sieve aggregate prepared by the above preparation method, wherein the Beta molecular sieve aggregate has a specific surface area of ​​650-1000 m². 2 / g, mesopore area is 400-800m² 2 / g, with mesopore diameters of 4.5–7.5 nm. The specific surface areas mentioned above include, but are not limited to, 650, 660, 680, 700, 720, 740, 760, 780, 800, 820, 840, 860, 880, 900, 920, 940, 960, 980, or 1000 m².2 / g. The mesopore area mentioned above includes, but is not limited to, 400, 450, 500, 550, 600, 650, 700, 750 or 800 μm. 2 / g. The mesopore diameters mentioned above include, but are not limited to, 4.5, 4.6, 4.8, 5, 5.2, 5.4, 5.5, 5.6, 5.8, 6, 6.2, 6.4, 6.5, 6.6, 6.8, 7, 7.2, 7.4 or 7.5 nm.

[0053] Furthermore, this invention provides an application of the aforementioned Beta molecular sieve aggregates in catalysis or automotive exhaust treatment. It should be understood that the focus of this invention is on applying these Beta molecular sieve aggregates to catalysis or automotive exhaust treatment; however, the specific application method is not limited to any particular method, and any method commonly used in the art can be employed.

[0054] The present invention will be further described in detail below with reference to embodiments and comparative examples.

[0055] It should be noted that in the following embodiments and comparative examples, the crystal structure of the product was determined by X-ray diffraction (XRD), and spectra with 2θ angles ranging from 5 to 35 degrees were recorded. The specific surface area and pore structure parameters of the product were obtained by low-temperature nitrogen adsorption-desorption measurements.

[0056] Example 1

[0057] A method for preparing Beta molecular sieve aggregates includes the following steps:

[0058] Step 1: An initial aluminum solution (concentration 1.5 mol / L) was prepared using sodium hydroxide and aluminum nitrate. Then, 0.15 mol / L of fluorosilicic acid aqueous solution and 0.3 mol / L of tetraethylammonium hydroxide (TEAOH) solution were added to adjust the pH to 12.5. The solution was pre-crystallized at 160℃ for 18 h, then mixed with Ludox AS-40 and crystallized at 150℃ for 24 h to obtain the initial Beta molecular sieve. The reaction system for the crystallization treatment had the following molar ratios: SiO2 / Al2O3 = 20, Na2O / SiO2 = 0.1, TEAOH / SiO2 = 0.01, H2O / SiO2 = 2.

[0059] Step 2: After mixing the initial Beta molecular sieve and polyvinyl alcohol, stir in an aqueous acetic acid solution at 90°C for 1 hour. The concentration of the aqueous acetic acid solution is 5%, and the mass ratio of the initial Beta molecular sieve, acetic acid and polyvinyl alcohol is 1:5:0.1. Aging is carried out for 24 hours, followed by a second pre-crystallization at 120°C for 12 hours. The pre-crystallized product is taken out at room temperature and pressure, washed and filtered, and then crystallized again at 120°C for 36 hours to obtain Beta molecular sieve aggregates.

[0060] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 670 m². 2 / g, mesopore area is 420m² 2 / g, with a mesopore size of 5.5nm.

[0061] from Figure 1 As can be seen, this embodiment successfully synthesized Beta molecular sieve aggregates, with obvious characteristic peaks and no impurity peaks, exhibiting a significant crystal structure. From Figure 2 It can be seen that the mesopore size of the Beta molecular sieve aggregates obtained in this embodiment is mostly distributed at 5.5 nm. From Figure 3 It can be seen that the Beta molecular sieve aggregates obtained in this embodiment have an aggregate size in the range of 200-300 nm.

[0062] Example 2

[0063] A method for preparing Beta molecular sieve aggregates differs from Example 1 in that, in Example S1, the aluminum source is aluminum sulfate, the concentration of the fluorosilicic acid aqueous solution is 0.2 mol / L, the pH is adjusted to 13, the first pre-crystallization is carried out at 150°C for 24 hours, the silicon source is fumed silica, and the crystallization time is 48 hours. The reaction system for the crystallization treatment has the following molar ratio: SiO2 / Al2O3 = 400, Na2O / SiO2 = 0.05, TEAOH / SiO2 = 0.02, H2O / SiO2 = 4. In S2, stirring is carried out for 2 hours, the initial mass ratio of Beta molecular sieve, acetic acid, and polyvinyl alcohol is 1:10:0.5, aging is carried out for 48 hours, and a second pre-crystallization is carried out for 24 hours.

[0064] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 690 m². 2 / g, mesopore area is 450m² 2 / g, with a mesopore size of 6.5nm.

[0065] Example 3

[0066] A method for preparing Beta molecular sieve aggregates differs from Example 1 in that, in Example S1, the alkali is potassium hydroxide, the aluminum source is sodium aluminate, the concentration of the fluorosilicic acid aqueous solution is 0.1 mol / L, the pH is 11, the first pre-crystallization temperature is 100℃, the time is 12 h, the silicon source is Ludox HS-30, and the crystallization time is 24 h. The reaction system for the crystallization treatment has the following molar ratio: SiO2 / Al2O3 = 600, Na2O / SiO2 = 0.1, TEAOH / SiO2 = 0.05, H2O / SiO2 = 5. In Example S2, the stirring time is 0.1 h, the aging time is 2 h, and the second pre-crystallization time is 1 h.

[0067] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 655 m². 2 / g, mesopore area is 405m² 2 / g, with a mesopore size of 4.8nm.

[0068] Example 4

[0069] A method for preparing Beta molecular sieve aggregates differs from Example 1 in that, in Example S1, the aluminum source is aluminum isopropoxide, the concentration of the fluorosilicic acid aqueous solution is 0.4 mol / L, the concentration of TEAOH is 0.5 mol / L, the pH is 13.5, the primary pre-crystallization temperature is 180℃, and the time is 24 h; the silicon source is tetraethyl orthosilicate, and the crystallization time is 48 h. In Example S2, the stirring time is 1.5 h, the aging time is 36 h, and the secondary pre-crystallization time is 18 h.

[0070] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 680 m². 2 / g, mesopore area is 430m² 2 / g, with a mesopore size of 6.8nm.

[0071] Example 5

[0072] A method for preparing Beta molecular sieve aggregates differs from Example 1 in that, in Example S1, the concentration of the fluorosilicic acid aqueous solution is 0.2 mol / L, the pH is 12, the silicon source is 50-100 mesh silica gel particles, the crystallization treatment temperature is 150℃, the time is 36 h, and the molar ratio of the crystallization reaction system is SiO2 / Al2O3 = 300, Na2O / SiO2 = 0.05, TEAOH / SiO2 = 0.03, and H2O / SiO2 = 3. In Example S2, the initial mass ratio of Beta molecular sieve, acetic acid, and polyvinyl alcohol is 1:20:1.

[0073] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 720 m². 2 / g, mesopore area is 480m² 2 / g, with a mesopore size of 7.1nm.

[0074] Example 6

[0075] A method for preparing Beta molecular sieve aggregates, differing from Example 1, in this Example S1, the aluminum source is sodium aluminate, the TEAOH solution concentration is 0.4 mol / L, the pH is 13, the primary pre-crystallization temperature is 180℃, and the time is 24 h. The silicon source is 200-500 mesh silica gel, the crystallization treatment temperature is 120℃, and the time is 48 h. The molar ratio of the crystallization reaction system is SiO2 / Al2O3 = 400, Na2O / SiO2 = 0.08, TEAOH / SiO2 = 0.04, and H2O / SiO2 = 4. In Example S2, the stirring time is 1.5 h, the aging time is 36 h, and the secondary pre-crystallization time is 18 h.

[0076] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 750 m². 2 / g, mesopore area is 520m² 2 / g, with a mesopore size of 7.2nm.

[0077] Example 7

[0078] A method for preparing Beta molecular sieve aggregates, which differs from Example 6 in that the concentration of the fluorosilicic acid aqueous solution in Example S1 is 0.3 mol / L and the concentration of TEAOH is 1 mol / L.

[0079] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 710 m². 2 / g, mesopore area is 470m² 2 / g, with a mesopore size of 6.1nm.

[0080] Example 8

[0081] A method for preparing Beta molecular sieve aggregates, which differs from Example 6 in that the reaction system for crystallization treatment in Example S1 has the following molar ratio composition: SiO2 / Al2O3 = 300, Na2O / SiO2 = 0.1, TEAOH / SiO2 = 1, H2O / SiO2 = 6.

[0082] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 705 m². 2 / g, mesopore area is 485m² 2 / g, with a mesopore size of 6.9nm.

[0083] Example 9

[0084] A method for preparing Beta molecular sieve aggregates, which differs from Example 6 in that the first pre-crystallization treatment in Example S1 is: treatment at 190°C for 10 hours.

[0085] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 690 m². 2 / g, mesopore area is 460m² 2 / g, with a mesopore size of 7.3nm.

[0086] Example 10

[0087] A method for preparing Beta molecular sieve aggregates, which differs from Example 6 in that the concentration of the acetic acid aqueous solution in the mixed aqueous solution in Example S2 is 6 mol / L.

[0088] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 675 m². 2 / g, mesopore area is 440m² 2 / g, with a mesopore size of 7.6nm.

[0089] Example 11

[0090] A method for preparing Beta molecular sieve aggregates, which differs from Example 6 in that the initial mass ratio of Beta molecular sieve, acetic acid and polyvinyl alcohol in Example S2 is 1:3:1.

[0091] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 665 m². 2 / g, mesopore area is 410m² 2 / g, with a mesopore size of 7.3nm.

[0092] Example 12

[0093] A method for preparing Beta molecular sieve aggregates, which differs from Example 6 in that the recrystallization temperature in Example S2 is 230°C and the time is 5 hours.

[0094] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this embodiment was tested to be 685 m². 2 / g, mesopore area is 450m² 2 / g, with a mesopore size of 6.9nm.

[0095] Comparative Example 1

[0096] A method for preparing Beta molecular sieve aggregates, which differs from Example 1 in that fluorosilicic acid was not used to treat the initial aluminum solution in Comparative Example S1.

[0097] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this comparative example was tested to be 490 m². 2 / g, mesopore area is 74m² 2 / g, with a mesopore size of 4.1nm.

[0098] Comparative Example 2

[0099] A method for preparing Beta molecular sieve aggregates differs from Example 1 in that, in Comparative Example S2, an aqueous solution of acetic acid and polyvinyl alcohol was not used for stirring and aging.

[0100] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this comparative example was tested to be 540 m². 2 / g, mesopore area is 82m² 2 / g, with a mesopore size of 3.8nm.

[0101] Comparative Example 3

[0102] A method for preparing Beta molecular sieve aggregates differs from Example 1 in that the stirring temperature in Comparative Example S2 is 180°C and the stirring time is 2.5 h.

[0103] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this comparative example was tested to be 450 m². 2 / g, mesopore area is 65m² 2 / g, with a mesopore size of 4.3nm.

[0104] Comparative Example 4

[0105] A method for preparing Beta molecular sieve aggregates, which differs from Example 1 in that no secondary recrystallization treatment was performed in Comparative Example S2.

[0106] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this comparative example was tested to be 430 m². 2 / g, mesopore area is 60m² 2 / g, with a mesopore size of 4.0nm.

[0107] Comparative Example 5

[0108] A method for preparing Beta molecular sieve aggregates, which differs from Example 1 in that recrystallization treatment was not performed in Comparative Example S2.

[0109] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this comparative example was tested to be 530 m². 2 / g, mesopore area is 80m² 2 / g, with a mesopore size of 3.3nm.

[0110] Comparative Example 6

[0111] A method for preparing Beta molecular sieve aggregates, which differs from Example 1 in that the pH in Comparative Example S1 is 10.

[0112] The specific surface area of ​​the Beta molecular sieve aggregates obtained in this comparative example was tested to be 510 m². 2 / g, mesopore area is 100m² 2 / g, with a mesopore size of 3.1nm.

[0113] Although the invention has been illustrated and described with reference to specific embodiments, it should be understood that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be included in the appended claims.

Claims

1. A method for preparing Beta molecular sieve aggregates, characterized in that, include: S1. Preparation of initial Beta molecular sieve: Add the first acid aqueous solution and organic template agent to the initial aluminum solution, adjust the pH to 11~13.5, and after a pre-crystallization treatment, obtain the original solution; mix the silicon source with the original solution, and after crystallization treatment, obtain the initial Beta molecular sieve; the initial aluminum solution includes alkali, aluminum source and water; S2. Initial Beta molecular sieve recrystallization treatment: The initial Beta molecular sieve and polyvinyl alcohol are mixed and stirred in a second acid aqueous solution at 20~150℃ for 0~2 h (excluding 0 h), aged for 2~48 h, pre-crystallized at 50~220℃ for 1~48 h, and then crystallized again to obtain Beta molecular sieve aggregates. The first acid is fluorosilicic acid; the recrystallization treatment is performed at a temperature of 120~220℃ for 1~72 hours.

2. The method for preparing Beta molecular sieve aggregates according to claim 1, characterized in that, The concentration of the first acid aqueous solution is 0.1~5 mol / L, the concentration of the organic template agent is 0.1~0.5 mol / L, and the concentration of the initial aluminum solution is 0.1~5 mol / L; The first pre-crystallization treatment is performed at a temperature of 100~180℃ for 12~24 h.

3. The method for preparing Beta molecular sieve aggregates according to claim 1, characterized in that, The organic template agent includes at least one of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride, tetraethylammonium fluoride, tetrapropylammonium hydroxide, tetramethylammonium hydroxide, tetramethylammonium bromide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide.

4. The method for preparing Beta molecular sieve aggregates according to claim 1, characterized in that, The crystallization process is performed at a temperature of 120~180℃ for 24~48 hours.

5. The method for preparing Beta molecular sieve aggregates according to claim 1, characterized in that, The silicon source includes at least one of silica sol, silica gel particles, fumed silica, and tetraethyl orthosilicate, wherein the silica gel particles have a particle size of 20-500 mesh. The alkali includes an inorganic alkali, which is sodium hydroxide and / or potassium hydroxide; the reaction system of the crystallization treatment has the following molar ratio composition: SiO2 / Al2O3=20~600, Na2O / SiO2=0.01~0.1, TEAOH / SiO2=0.01~0.05, H2O / SiO2=2~5; The aluminum source includes at least one of aluminum sulfate, aluminum nitrate, sodium aluminate, aluminum isopropoxide, or aluminum sec-butoxide.

6. The method for preparing Beta molecular sieve aggregates according to claim 1, characterized in that, The second acid is selected from at least one of fluorosilicic acid, sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, phosphoric acid, formic acid, or acetic acid; The concentration of the second acid aqueous solution is 0.1 mol / L-5.0 mol / L.

7. The method for preparing Beta molecular sieve aggregates according to claim 1, characterized in that, The mass ratio of the initial Beta molecular sieve, the second acid, and the polyvinyl alcohol is 1:5~20:0.1~1.

8. A Beta molecular sieve aggregate prepared by the preparation method according to any one of claims 1 to 7, wherein the Beta molecular sieve aggregate has a specific surface area of ​​650 to 1000 m². 2 / g, mesopore area of ​​400~800 m 2 / g, with mesopore diameters of 4.5~7.5nm.

9. The application of the Beta molecular sieve aggregates according to claim 8 in catalysis.

10. The application according to claim 9, characterized in that, Application of the Beta molecular sieve aggregates in automobile exhaust treatment.

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