A nanocluster silicoaluminophosphate molecular sieve and a method for preparing the same

Abstract

The application discloses a kind of nanocluster phosphosilicate aluminum molecular sieves and preparation method thereof, nanocluster phosphosilicate aluminum molecular sieve crystal structure belongs to aluminophosphate-A;With micropore-mesoporous two-stage composite pore structure, and in micropore and mesopore range all present concentrated distribution characteristics.Nanocluster phosphosilicate aluminum molecular sieve preparation method steps as follows: under the condition of sufficient mixing, silicon precursor, aluminum precursor, phosphoric acid, adjuvant, structure directing agent and water are mixed uniformly, to obtain stream A;Further under hydrothermal crystallization condition is handled, then after separation, product is obtained after heat treatment.The application provides a kind of new nanocluster phosphosilicate aluminum molecular sieve and preparation method thereof, especially in preparation, by the use of adjuvant, can simplify separation process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic material synthesis, and particularly relates to a molecular sieve material and a synthesis method thereof. BACKGROUND

[0002] Catalysts and adsorbents used in chemical industry mostly belong to porous materials, which have high specific surface area and other specific properties. Commonly used porous materials mainly include zeolite, alumina, silica, silica-alumina, activated carbon, etc. These porous materials have been widely applied to different technical fields, and have achieved great social and economic benefits. However, with the increase of demand, these traditional materials have been unable to meet the requirements in some fields, and new porous materials need to be developed to meet the actual needs of industrial production.

[0003] CN101884936A discloses a method for preparing a SAPO-34 molecular sieve shaped catalyst, a product obtained by the method and application thereof. The invention is activated by using an alkali solution to treat montmorillonite; after activation, the montmorillonite is mixed with an aluminum source, a phosphorus source, a template agent and deionized water, and then a high-temperature hydrothermal crystallization reaction is carried out; the crystallization slurry containing the montmorillonite matrix material, the silicoaluminophosphate molecular sieve and a binder are mixed and then shaped to obtain the SAPO-34 molecular sieve shaped catalyst.

[0004] CN101432072A discloses a method for synthesizing aluminophosphate and silicoaluminophosphate molecular sieves. In the method for synthesizing aluminophosphate or silicoaluminophosphate molecular sieves, a synthesis mixture is prepared by mixing a plurality of starting materials, which at least include a water source, a phosphorus source, an aluminum source, optionally a silicon source, and at least one organic directing agent for directing the formation of the molecular sieve. The starting materials are maintained at a temperature of 25-50°C, preferably 30-45°C during the mixing, and until the preparation of the starting mixture is completed, after which the synthesis mixture is heated to a crystallization temperature of about 100-350°C until the crystals of the molecular sieve are prepared. When the crystallization is completed, the molecular sieve is recovered.

[0005] “P2O5-Al2O3-triethanolamine system hydrothermal crystallization of multi-directional” (Petroleum Science and Technology (Petroleum Chemical Industry), September 1989, Vol. 5, No. 3) discloses the synthesis of phosphorus aluminum molecular sieve, by changing the preparation conditions of P2O5-Al2O3-triethanolamine (TEA) system, 10 different structure types of crystalline products are obtained. Phosphoric acid, pseudo-boehmite and triethanolamine are used as raw materials, and the synthesis is carried out at a crystallization temperature of 150°C. The crystal framework of the material is composed of aluminum, phosphorus and oxygen, and the crystal structure is aluminophosphate-A. SUMMARY

[0006] The present application provides a nano-cluster silicoaluminophosphate molecular sieve and a preparation method thereof.

[0007] The technical scheme of the present application is as follows: first, a nano-cluster aluminophosphate-silica molecular sieve is provided, which has a crystal structure belonging to aluminophosphate-A; has a two-stage composite pore structure of micropore-mesopore, and shows a concentrated distribution in the micropore and mesopore ranges, wherein the micropore distribution range is 0.5-0.6 nm, and the mesopore distribution range is 3.5-10 nm; the total specific surface area is 300-900 m 2 / g, wherein the mesopore surface area is 100-210 m 2 / g; the individual crystal morphology is approximately spherical, with a size of about 20-100 nm, and a plurality of nano-crystals form a cluster-shaped large crystal, and the large crystal morphology is an irregular block, and the large crystal size range is 1-10 microns.

[0008] The present application also provides a preparation method of the nano-cluster aluminophosphate-silica molecular sieve, and the steps are as follows:

[0009] Step 1: under the condition of sufficient mixing, the silicon precursor, the aluminum precursor, the phosphoric acid, the additive, the structure directing agent and water are mixed uniformly to obtain a stream A;

[0010] Step 2: the stream A obtained in step 1 is treated under the condition of hydrothermal crystallization, and then separated to obtain the product after heat treatment.

[0011] The present application also provides a nano-cluster aluminophosphate-silica molecular sieve obtained by the above preparation method.

[0012] The nano-cluster aluminophosphate-silica molecular sieve material provided by the present application has a two-stage composite pore structure of micropore-mesopore, is mainly composed of micropores, has good molecular transmission capacity, belongs to a high specific surface area solid porous material, can provide sufficient reaction sites for catalytic reactions, or provide sufficient adsorption sites for gaseous or liquid substances, and can be used as an adsorption separation agent for gases or liquids, or as a catalyst carrier.

[0013] The main skeleton structure of the nano-cluster aluminophosphate-silica molecular sieve material provided by the present application includes four elements of silicon, phosphorus, aluminum and oxygen, specifically, is composed of a silicon-oxygen structure, an aluminum-oxygen structure and a phosphorus-oxygen structure to form a basic structural unit, and finally forms a network structure porous structure. Since the silicon, phosphorus and aluminum exposed on the outer surface of the material have unsaturation on the valence bond, the material can form an action force with hydrocarbon molecules and has a certain catalytic performance; and can form a strong interaction with metal elements, adsorb metal elements, and be used as a carrier of metal catalysts.

[0014] The nanocluster aluminosilicate phosphate molecular sieve material provided by this invention has a relatively regular crystal morphology. Individual crystals are approximately spherical with a size of about 20–100 nm, and several nanocrystals form clusters of large crystals. These large crystals are irregularly shaped blocks with a size ranging from 1 to 10 micrometers. The crystal size, especially the size of the large crystals, can be adjusted by changing reaction parameters such as raw material ratios and preparation conditions, and the adsorption properties will change accordingly.

[0015] The method for preparing nanocluster aluminosilicate phosphate molecular sieve material provided by the present invention obtains nanocluster aluminosilicate phosphate molecular sieve material with micropore-mesopore dual-level channels through the dual action of composite structure directing agent and auxiliary agent. Moreover, the use of auxiliary agent can simplify the separation operation. Conventional filtration separation method can ensure that nanocluster aluminosilicate phosphate molecular sieve is obtained, and centrifugation separation operation can be omitted. Attached Figure Description

[0016] Figure 1 The XRD pattern of the material obtained in Example 1 is shown.

[0017] Figure 2 A scanning electron microscope image (2 μm) of the material obtained in Example 1.

[0018] Figure 3 The image is a scanning electron microscope image (100 nm) of the material obtained in Example 1.

[0019] Figure 4 The pore size distribution diagram of the material obtained in Example 1 is shown. Detailed Implementation

[0020] The technical solutions and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments.

[0021] Furthermore, the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] Furthermore, in this document, unless otherwise expressly stated, percentages and percent contents are all expressed by mass.

[0023] Further, in the present text, the phase structure of the silicoaluminophosphate molecular sieve is characterized by X-ray diffraction, which is tested by a D / max2500 X-ray diffractometer of Japan Rigaku, a Cu target, a Kα radiation source, a graphite monochromator, a tube voltage of 40 kV, a tube current of 80 mA, a scanning range of 5°-40°, a step of 0.1°, and a scanning speed of 1° / min.

[0024] Further, in the present text, the pore structure of the silicoaluminophosphate molecular sieve is measured by N2 adsorption-desorption, which is tested by an ASAP2420 physical adsorption instrument of Micromeritics Corporation of America. Before measurement, the sample is treated in vacuum at 300°C for more than 4 hours. The specific surface area and other parameters are calculated by the BET and t-plot methods, and the pore size distribution is measured by the DFT method.

[0025] Further, in the present text, the microcrystal morphology structure of the silicoaluminophosphate molecular sieve material is characterized by a scanning electron microscope, which is tested by a JSM-6301F scanning electron microscope (equipped with Oxford EDS) of Japan Electronics Corporation, a working voltage of 20 kV, a working distance of 15 mm, and a resolution of 1.5 nm.

[0026] The microcrystal morphology structure of the material of the present application is characterized by a scanning electron microscope, which is tested by a JSM-6301F scanning electron microscope (equipped with Oxford EDS) of Japan Electronics Corporation, a working voltage of 20 kV, a working distance of 15 mm, and a resolution of 1.5 nm.

[0027] The technical solutions and effects of the present application are further illustrated by the following examples, but are not limited to the following examples.

[0028] The first aspect of the present application provides a nanocluster silicoaluminophosphate molecular sieve, which has a crystal structure belonging to aluminophosphate-A, a two-level composite pore channel structure of micropore-mesopore, and a concentrated distribution in the micropore and mesopore ranges, wherein the micropore distribution range is 0.5-0.6 nm, and the mesopore distribution range is 3.5-10 nm.

[0029] Further, the crystal morphology of the above-mentioned nanocluster silicoaluminophosphate molecular sieve is approximately spherical, with a size of about 20-100 nm, and a cluster of nanocrystals forms a large crystal, and the morphology of the large crystal is an irregular block, and the size range of the large crystal is 1-10 microns.

[0030] Further, the total specific surface area of the above-mentioned nanocluster silicoaluminophosphate molecular sieve is 300-900 m 2 / g, wherein the mesopore specific surface area is 100-210 m 2 / g.

[0031] Further, the nanocluster silicoaluminophosphate molecular sieve has a main framework structure including four elements of silicon, phosphorus, aluminum and oxygen, and is a netted porous structure formed by basic structural units including silicon-oxygen structure, aluminum-oxygen structure and phosphorus-oxygen structure.

[0032] Further, the nanocluster silicoaluminophosphate molecular sieve belongs to solid inorganic crystal material, and its crystal structure belongs to aluminophosphate-A type, and specific diffraction data are as follows.

[0033]

[0034] The application also provides a preparation method of the nanocluster silicoaluminophosphate molecular sieve, and the steps are as follows.

[0035] Step 1: under the condition of sufficient mixing, mixing silicon precursor, aluminum precursor, phosphoric acid, additive, structure directing agent and water to obtain a stream A;

[0036] Step 2: treating the stream A obtained in step 1 under the condition of hydrothermal crystallization, and then separating and heat treating to obtain a product.

[0037] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the phosphoric acid added generates the phosphorus-oxygen structure as the framework of the silicoaluminophosphate molecular sieve in the subsequent hydrothermal crystallization reaction.

[0038] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the silicon precursor added generates the silicon-oxygen structure as the framework of the silicoaluminophosphate molecular sieve in the subsequent hydrothermal crystallization reaction. The silicon precursor can be at least one of methyl orthosilicate, ethyl orthosilicate, white carbon black, silica gel, silica sol and water glass, and preferably methyl orthosilicate and / or ethyl orthosilicate.

[0039] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the aluminum precursor added generates the aluminum-oxygen structure as the framework of the silicoaluminophosphate molecular sieve in the subsequent hydrothermal crystallization reaction. The aluminum precursor can be at least one of aluminum isopropoxide, aluminum butoxide and aluminum sec-butoxide.

[0040] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the structure directing agent includes triethylamine and glycine, and belongs to a composite structure directing agent. In the hydrothermal synthesis process, the triethylamine and glycine jointly act with the silicon precursor, the aluminum precursor and the phosphoric acid to form the framework of the silicoaluminophosphate molecular sieve.

[0041] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the additive is polyquaternary ammonium salt-6 (the monomer is C8H 16 N), polyquaternary ammonium salt-7 (the monomer is C 11 H 21at least one of Cl, F, Br, I, and CN2O.

[0042] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the ratio of the various raw materials used in step 1 is as follows: the molar ratio of phosphoric acid, silicon precursor, aluminum precursor, water, triethylamine, and glycine is 1.5-6P: 0.5-2.5SiO2: Al2O3: 150-700H2O: 5-12.5triethylamine: 2-8glycine, preferably 2-5P: 1-2SiO2: Al2O3: 200-600H2O: 6-12triethylamine: 3-7glycine; the mass ratio of the auxiliary agent to water is 1-6: 100, preferably 2-5: 100.

[0043] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the hydrothermal crystallization conditions in step 2 are as follows: the temperature is 140-200°C, preferably 150-190°C; the time is 60-220h, preferably 70-200h.

[0044] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the separation in step 2 can be performed by filtration, which generally includes multiple filtrations until the filtrate is neutral.

[0045] Further, in the preparation method of the nanocluster silicoaluminophosphate molecular sieve, the heat treatment in step 2 includes low-temperature drying heat treatment and high-temperature calcination heat treatment, wherein the drying heat treatment temperature is 100-150°C, and the time is 1-10h; the calcination heat treatment temperature is 400-600°C, and the calcination treatment time is 1-10h; the calcination needs to be performed in an oxygen atmosphere, which can generally be performed in an air or oxygen atmosphere.

[0046] Example 1

[0047] 7.5g of phosphoric acid, 15.8g of triethylamine, 8g of glycine, 3g of polyquaternary ammonium salt-6, and 8.5g of aluminum isopropoxide were dissolved in 150g of distilled water, 5g of tetraethyl orthosilicate was then added, and the mixture was uniformly mixed, followed by treatment at 155°C for 160h; the obtained sample was then filtered multiple times, and then placed in an oven for drying at 110°C for 12h, and finally calcined in air at 550°C for 5h, to obtain a sample numbered A1.

[0048] Example 2

[0049] 4.1g of phosphoric acid, 12.8g of triethylamine, 4.8g of glycine, 1.5g of polyquaternary ammonium salt-6, and 8.5g of aluminum isopropoxide were dissolved in 75g of distilled water, 4.5g of tetraethyl orthosilicate was then added, and the mixture was uniformly mixed, followed by treatment at 150°C for 70h; the obtained sample was then filtered multiple times, and then placed in an oven for drying at 110°C for 12h, and finally calcined in air at 550°C for 5h, to obtain a sample numbered A2.

[0050] Example 3.

[0051] Dissolve 10.0 g of phosphoric acid, 25 g of triethylamine, 10 g of glycine, 11 g of polyquaternary salt-6, 8.5 g of aluminum isopropoxide in 220 g of distilled water, then add 8.5 g of tetraethyl orthosilicate, mix well, then treat at 190°C for 200 h; then filter the obtained sample multiple times, then place in an oven at 110°C for drying for 12 h, and finally calcine at 550°C in air for 5 h, and the obtained sample is numbered as A 3.

[0052] Example 4

[0053] Dissolve 8.5 g of phosphoric acid, 17 g of triethylamine, 9.6 g of glycine, 4 g of polyquaternary salt-6, 7.5 g of aluminum isopropoxide in 200 g of distilled water, then add 6.7 g of tetraethyl orthosilicate, mix well, then treat at 180°C for 170 h; then filter the obtained sample multiple times, then place in an oven at 110°C for drying for 12 h, and finally calcine at 550°C in air for 5 h, and the obtained sample is numbered as A 4.

[0054] Example 5

[0055] Dissolve 9.5 g of phosphoric acid, 13.5 g of triethylamine, 8 g of glycine, 3.5 g of polyquaternary salt-7, 8.9 g of aluminum isopropoxide in 165 g of distilled water, then add 6.9 g of tetraethyl orthosilicate, mix well, then treat at 185°C for 190 h; then filter the obtained sample multiple times, then place in an oven at 110°C for drying for 12 h, and finally calcine at 550°C in air for 5 h, and the obtained sample is numbered as A 5.

[0056] Comparative Example 1

[0057] Dissolve 7.5 g of phosphoric acid, 8 g of glycine, 3 g of polyquaternary salt-6, 8.5 g of aluminum isopropoxide in 150 g of distilled water, then add 5 g of tetraethyl orthosilicate, mix well, then treat at 155°C for 160 h; then filter the obtained sample multiple times, then place in an oven at 110°C for drying for 12 h, and finally calcine at 550°C in air for 5 h, and the obtained sample is numbered as A 6, and the obtained product is amorphous, and no phosphosilicate-alumina molecular sieve is synthesized.

[0058] Comparative Example 2

[0059] Dissolve 7.5 g of phosphoric acid, 15.8 g of triethylamine, 3 g of polyquaternary salt-6, 8.5 g of aluminum isopropoxide in 150 g of distilled water, then add 5 g of tetraethyl orthosilicate, mix well, then treat at 155°C for 160 h; then filter the obtained sample multiple times, then place in an oven at 110°C for drying for 12 h, and finally calcine at 550°C in air for 5 h, and the obtained sample is numbered as A 7, and the obtained product is amorphous, and no phosphosilicate-alumina molecular sieve is synthesized.

[0060] Comparative Example 3

[0061] Dissolve 7.5 g of phosphoric acid, 1 g of triethylamine, 1 g of glycine, 3 g of polyquaternary salt-6, 8.5 g of aluminum isopropoxide in 150 g of distilled water, then add 5 g of tetraethyl orthosilicate, mix well, and then treat at 155°C for 160 h; then filter the obtained sample several times, then place it in an oven at 110°C for 12 h, and finally calcine it at 550°C in air for 5 h. The obtained sample is numbered A 8, and the obtained product is amorphous, and no silicoaluminophosphate molecular sieve is synthesized.

[0062] Comparative Example 4

[0063] Dissolve 7.5 g of phosphoric acid, 35 g of triethylamine, 18 g of glycine, 3 g of polyquaternary salt-6, 8.5 g of aluminum isopropoxide in 150 g of distilled water, then add 5 g of tetraethyl orthosilicate, mix well, and then treat at 155°C for 160 h; then filter the obtained sample several times, then place it in an oven at 110°C for 12 h, and finally calcine it at 550°C in air for 5 h. The obtained sample is numbered A 9, and the obtained product is amorphous, and no silicoaluminophosphate molecular sieve is synthesized.

[0064] Comparative Example 5

[0065] Dissolve 7.5 g of phosphoric acid, 15.8 g of triethylamine, 8 g of glycine, 3 g of cetyltrimethylammonium bromide, 8.5 g of aluminum isopropoxide in 150 g of distilled water, then add 5 g of tetraethyl orthosilicate, mix well, and then treat at 155°C for 160 h; then filter the obtained sample several times, then place it in an oven at 110°C for 12 h, and finally calcine it at 550°C in air for 5 h. The obtained sample is numbered A 10, and the obtained product is amorphous, and no silicoaluminophosphate molecular sieve is synthesized. It is indicated that cetyltrimethylammonium bromide can affect the synthesis of silicoaluminophosphate molecular sieve.

[0066] Comparative Example 6

[0067] Dissolve 7.5 g of phosphoric acid, 15.8 g of triethylamine, 8 g of glycine, 8.5 g of aluminum isopropoxide in 150 g of distilled water, then add 5 g of tetraethyl orthosilicate, mix well, and then treat at 155°C for 160 h; then filter the obtained sample several times, then place it in an oven at 110°C for 12 h, and finally calcine it at 550°C in air for 5 h. The obtained sample is numbered A 11. The obtained product is a silicoaluminophosphate molecular sieve, but the mesopore content is extremely low, and it can be considered that there is almost no mesopore structure.

[0068] Table 1. Physicochemical properties of samples of examples and comparative examples

[0069]

[0070] Note: In the present application, the crystallinity of the sample in Example 1 is defined as 100%, specifically, the height of the peak with the strongest diffraction intensity in the XRD spectrum of the sample in Example 1 is defined as 100%. The crystallinity of all other samples is obtained by comparing the height of the peak with the strongest diffraction intensity in the XRD spectrum of the sample to be compared with the sample in Example 1, i.e. the reference sample.

Claims

1. A nanocluster of aluminosilicate molecular sieve, the crystal structure of which belongs to aluminophosphate-A; it has a two-level composite pore structure of micropores and mesopores, and exhibits a concentrated distribution in both the micropore and mesopore ranges, wherein the micropore distribution range is 0.5-0.6 nm and the mesopore distribution range is 3.5-10 nm.

2. The nanocluster silica-alumina molecular sieve according to claim 1, characterized in that: Individual crystals of silica-alumina phosphate molecular sieves are approximately spherical in shape, with a size of 20–100 nm. Several nanocrystals form clusters of large crystals, which are irregular blocks with a size range of 1–10 micrometers.

3. The nanocluster silica-alumina molecular sieve according to claim 1, characterized in that: The total specific surface area of ​​nanocluster silica-alumina molecular sieves is 300–900 m². 2 / g, mesoporous specific surface area is 100~210m² 2 / g.

4. The nanocluster silica-alumina molecular sieve according to claim 1, characterized in that: The main framework structure of the nanocluster phosphate aluminosilicate molecular sieve includes four elements: silicon, phosphorus, aluminum, and oxygen. It is a network porous structure formed by basic structural units including silicon-oxygen, aluminum-oxygen, and phosphorus-oxygen structures.

5. The nanocluster silica-alumina molecular sieve according to claim 1, characterized in that: Nanocluster aluminum silicate phosphate molecular sieves belong to solid inorganic crystal materials, and their crystal structure belongs to the aluminophosphate-A type.

6. A method for preparing nanocluster silica-alumina molecular sieves, comprising the following steps: Step 1: Under thorough mixing conditions, the silicon precursor, aluminum precursor, phosphoric acid, additives, structure directing agent, and water are mixed to obtain material flow A; the structure directing agent includes triethylamine and glycine, and the additives are at least one of polyquaternium-6 and polyquaternium-7; the proportions of the various raw materials used are as follows: the molar ratio of phosphoric acid, silicon precursor, aluminum precursor, water, triethylamine, and glycine is 1.5-6P:0.5-2.5SiO2:Al2O3:150-700H2O:5-12.5Triethylamine:2-8glycine, and the mass ratio of additives to water is 1-6:100; Step 2: The material flow A obtained in Step 1 is processed under hydrothermal crystallization conditions, and then separated and heat-treated to obtain the product.

7. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: The silicon precursor is derived from at least one of methyl orthosilicate, ethyl orthosilicate, silica, silica sol, and water glass.

8. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: The silicon precursors are methyl orthosilicate and / or ethyl orthosilicate.

9. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: The aluminum precursor is derived from at least one of aluminum isopropoxide, aluminum butoxide, and aluminum sec-butoxide.

10. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: The proportions of the various raw materials used in step 1 are as follows: the molar ratio of phosphoric acid, silicon precursor, aluminum precursor, water, triethylamine, and glycine is 2-5P:1-2SiO2:Al2O3:200-600H2O:6-12triethylamine:3-7glycine; the mass ratio of the auxiliaries to water is 2-5:

100.

11. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: The hydrothermal crystallization conditions in step 2 are: temperature 140–200℃ and time 60–220h.

12. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: The hydrothermal crystallization conditions in step 2 are: temperature 150–190℃ and time 70–200h.

13. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: In step 2, separation is performed using a filtration method.

14. The method for preparing nanocluster silica-alumina molecular sieves according to claim 6, characterized in that: Step 2 includes low-temperature drying heat treatment and high-temperature calcination heat treatment. The drying heat treatment temperature is 100-150℃ and the time is 1-10h. The calcination heat treatment temperature is 400-600℃ and the calcination heat treatment time is 1-10h. Calcination must be carried out under an oxygen atmosphere.

15. A nanocluster of silica-alumina molecular sieve, characterized in that: The nanocluster silica-alumina molecular sieve is prepared using the method described in any one of claims 6-14.

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