A multi-level pore sba-15 molecular sieve and a preparation method thereof

Abstract

The application provides a kind of hierarchical pore SBA-15 molecular sieve and its preparation method, the preparation method includes the following steps: P123, pore expander and inorganic acid are dissolved in water to obtain a mixed solution, silicon source is added and hydrolyzed in the mixed solution to obtain a hydrolysate and mother liquor;Repeat the following operation: the mother liquor obtained in the last step is subjected to ethanol removal treatment, then P123, pore expander and inorganic acid are added and dissolved, silicon source is added and hydrolyzed again, and the solid and mother liquor are obtained again;S3: the hydrolysate obtained in S1 and S2 is combined, and the combined solid product is subjected to hydrothermal crystallization by adding the mother liquor, the crystallization product is dried and calcined to obtain the hierarchical pore SBA-15 molecular sieve.The preparation method of the application has high synthesis efficiency, low cost and less pollution, and the synthesized molecular sieve contains hierarchical pore structure and can realize cross-scale penetration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve materials, in particular to a hierarchical pore SBA-15 molecular sieve and a preparation method thereof. BACKGROUND

[0002] Molecular sieves are widely used in adsorption, separation, catalysis and other fields due to their unique pore structure, especially in petroleum and chemical industry. With the continuous development of molecular sieve catalytic applications, single-pore molecular sieves cannot meet the diverse needs of catalyst preparation.

[0003] Microporous molecular sieves (diameter less than 2nm) have small pore size and long and narrow pore channels, so it is difficult for large molecules in heavy oil to diffuse into the pore channels, which reduces the reaction in the narrow pore channels of the microporous molecular sieves. The large molecule reactants cannot enter the pore channels, and the narrow and long pore channels have large diffusion resistance, which affects the rapid diffusion of the reaction product molecules, easily leading to deep cracking and coking, and even further leading to rapid deactivation of the molecular sieve. Compared with microporous molecular sieve materials, mesoporous molecular sieves (diameter of 2-50nm) can make up for the limitations of microporous molecular sieves in reactant and reaction product internal diffusion, but due to the amorphous structure of ordered mesoporous molecular sieves, their structural stability is often poor, which limits their application in the catalytic field. The internal structure of mesoporous molecular sieves is long-range ordered and short-range disordered. Macroporous molecular sieves (diameter greater than 50nm) have a more loose structure, usually have a larger specific surface area and pore volume, and have lost the ability to separate molecules due to their large pore size.

[0004] Therefore, an ideal porous material catalyst should have excellent activity, shape selectivity and hydrothermal stability on the one hand, and good diffusion performance on the other hand. Obviously, molecular sieve materials with single micropore, mesopore or macropore structure cannot meet the above performance. Therefore, it is necessary to make up for the structural defects of various single-pore porous materials and to design and prepare hierarchical pore molecular sieve materials containing hierarchical pore structures and realizing cross-scale penetration.

[0005] The existing method for producing molecular sieves has problems of low efficiency, high cost and serious pollution, and the prepared molecular sieves have single pore structure and cannot meet the application requirements. SUMMARY

[0006] To solve the above technical problems, the present application provides a hierarchical pore SBA-15 molecular sieve and a preparation method thereof. The preparation method has high synthesis efficiency, low cost and less pollution, and the synthesized molecular sieve contains hierarchical pore structure and realizes cross-scale penetration.

[0007] To achieve the above objectives, the present invention provides a method for preparing a hierarchical porous SBA-15 molecular sieve, comprising the following steps:

[0008] S1: Dissolve the nonionic surfactant P123 (templating agent), pore expander and inorganic acid in water to obtain a mixture. Add a silicon source and hydrolyze it in the mixture. After hydrolysis, separate the solid and liquid to obtain the hydrolysis product (solid) and mother liquor.

[0009] S2: Repeat the following steps: Add polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander and inorganic acid to the mother liquor obtained in the previous step and dissolve them. Add silicon source and hydrolyze again. After hydrolysis, separate solid and liquid to obtain hydrolysis product (solid) and mother liquor again.

[0010] S3: Combine the hydrolysis products obtained from S1 and S2, add the final mother liquor to perform hydrothermal crystallization on the combined hydrolysis products, dry and calcine the crystallized products to obtain the multi-level porous SBA-15 molecular sieve.

[0011] The pore-expanding agent includes at least two of the following: hydroxypropyl methylcellulose, PEG800, PEG1000, PEG1500, PEG2000, and AES surfactant.

[0012] This invention prepares multi-level porous molecular sieves by adding pore-expanding agents of different proportions and molecular weights, solving the technical problem that existing molecular sieve materials with single microporous, mesoporous, or macroporous structures cannot simultaneously meet the requirements of excellent activity, shape selectivity, hydrothermal stability, and good diffusion performance. It also solves the problems of low synthesis efficiency, high cost, and serious pollution in molecular sieve synthesis by recycling the mother liquor and using multiple hydrolysis and single crystallization.

[0013] Regarding production efficiency, conventional methods require at least 3 days to produce a batch of hierarchical SBA-15 molecular sieves in a single reactor, with 1 day dedicated to dissolving P123, the pore-expanding agent, and hydrolyzing the silicon source, and 2 days for hydrothermal crystallization. If 8 batches are produced in the same reactor, at least 24 days are needed. The preparation method of this invention combines 8 batches of hydrolysis products and produces the same amount of hierarchical SBA-15 molecular sieves in the same reactor through a single crystallization process without increasing equipment investment, requiring only 10 days (8 days for dissolving P123 and the pore-expanding agent, and hydrolyzing the silicon source in 8 batches, respectively, and 2 days for hydrothermal crystallization). Furthermore, the efficiency increases with the number of batches synthesized.

[0014] This invention adopts mother liquor recycling, which makes full use of the inorganic acid, nonionic surfactant P123 and pore expander in the mother liquor. This not only greatly reduces environmental pollution, but also further reduces the raw material cost of multi-stage porous SBA-15 molecular sieve.

[0015] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the pore-expanding agent includes at least two of hydroxypropyl methylcellulose, PEG1500, PEG2000, and AES surfactant.

[0016] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the pore-expanding agent comprises PEG1500:PEG2000:hydroxypropyl methylcellulose:AES surfactant in a mass ratio of 1:1-4:0-4:0-4.

[0017] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the pore-expanding agent is a combination of PEG1500 and PEG2000, and the preferred pore-expanding agent mass ratio is PEG1500:PEG2000 = 1:1:-2.

[0018] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the molar ratio of the nonionic surfactant P123 of the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer in S1 to the silicon source is 0.01-0.02:1.

[0019] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the molar ratio of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander, and inorganic acid in S1 is 1:3-8:300-1500, more preferably 1:4-6:600-1200.

[0020] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the amounts of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander and inorganic acid added in S2 are 30%-80%, 30%-100% and 10%-60% of the initial amounts, respectively, and more preferably, the amounts added are 40%-60%, 50%-80% and 30%-50% of the initial amounts, respectively.

[0021] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the operation in S2 is repeated 1-80 times, more preferably 5-60 times.

[0022] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the hydrolysis reaction temperature of the silicon source in S1 and S2 is 30-60℃, and the hydrolysis time is 4-20h.

[0023] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the hydrolysis reaction temperature of the silicon source in S1 and S2 is 40-60℃, and the hydrolysis time is 8-16h.

[0024] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the hydrothermal crystallization reaction temperature in S3 is 100-120℃, and the reaction time is 20-60h, preferably 30-50h.

[0025] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, in the hydrothermal crystallization described in S3, the mass ratio of mother liquor to total solids is 1-50:1, more preferably 1-40:1.

[0026] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the calcination conditions in S3 include: calcination at 500-600℃ in an air atmosphere for 4-8 hours.

[0027] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the drying conditions in S3 include: drying at a temperature of 100-120℃ for 4-10 hours.

[0028] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the silicon source includes at least one of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, silica sol, and water glass, and more preferably at least one of ethyl orthosilicate, silica sol, and water glass.

[0029] In the above-mentioned method for preparing multi-level porous SBA-15 molecular sieve, preferably, the inorganic acid includes at least one of hydrochloric acid, phosphoric acid, and nitric acid.

[0030] The present invention also provides a multi-level porous SBA-15 molecular sieve obtained by the above-described method for preparing multi-level porous SBA-15 molecular sieve.

[0031] Preferably, in the above-mentioned hierarchical porous SBA-15 molecular sieve, the specific surface area of ​​the hierarchical porous SBA-15 molecular sieve is >817 m². 2 / g, pore volume >1.12ml / g, average pore size >16.3nm.

[0032] The technical solution provided by this invention has the following beneficial effects:

[0033] The preparation method of the present invention has high synthesis efficiency, low waste emission, and low pollution. The multi-level porous SBA-15 molecular sieve synthesized by the present invention contains a multi-level pore structure and can achieve cross-scale interconnection, and has excellent activity, shape selectivity, hydrothermal stability and diffusion performance. Attached Figure Description

[0034] Figure 1The XRD patterns of the SBA-15 hierarchical porous molecular sieves in Examples 1-4 are shown below.

[0035] Figure 2 The low-temperature N2 adsorption-desorption isotherms of the SBA-15 hierarchical porous molecular sieve in Examples 1-4 are shown.

[0036] Figure 3A These are the pore distribution curves of the SBA-15 multi-level porous molecular sieves from Examples 1-2;

[0037] Figure 3B These are the pore distribution curves of the SBA-15 multi-level porous molecular sieves from Examples 3-4;

[0038] Figure 4A TEM image of the SBA-15 hierarchical porous molecular sieve from Example 1;

[0039] Figure 4B This is a TEM image of the SBA-15 hierarchical porous molecular sieve from Example 2.

[0040] Figure 4C TEM image of the SBA-15 hierarchical porous molecular sieve in Example 3;

[0041] Figure 4D This is a TEM image of the SBA-15 hierarchical porous molecular sieve from Example 4. Detailed Implementation

[0042] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0043] The sources of raw materials or equipment in embodiments of the present invention include:

[0044]

[0045]

[0046] The analysis used in the embodiments of the present invention includes:

[0047] X-ray diffraction (XRD): The XRD test of the sample was performed on a Rigaku D / max-2500pc X-ray diffractometer in Japan, using Cu Kα rays (λ=0.1541841nm) as the light source, with a voltage of 40KV and a current of 200mA.

[0048] Pore ​​structure analysis (BET): The specific surface area and pore structure of the samples were determined using an ASAP2405M specific surface area and porosity analyzer from Micron Instruments, Inc. The measurement conditions were as follows: samples were purified under a vacuum of <10⁴ mtorr. The adsorption volume of N₂ on the sample surface was measured at different pressures under liquid nitrogen temperature, and the specific surface area of ​​the samples was calculated using the BET formula; pore distribution was determined using the BJH method.

[0049] Temperature-programmed desorption (NH3-TPD): Acidity was characterized using the NH3-TPD method. 0.2 g of sample was weighed and purified at 600 °C with a He gas flow for 1 h. After cooling to room temperature, NH3 was adsorbed for 10 min, followed by purging with a He gas flow for 30 min. The temperature was then increased from room temperature to 100 °C at a rate of 10 °C / min, and purging continued until the baseline stabilized. Finally, the temperature was increased to 600 °C at a rate of 10 °C / min and held for 30 min.

[0050] Transmission electron microscopy (TEM): Transmission electron microscopy (TEM) characterization was performed on a Philips Tecnai G2F20 field emission transmission electron microscope from the Netherlands.

[0051] Example 1

[0052] This embodiment provides a hierarchical porous SBA-15 molecular sieve, the preparation method of which is as follows:

[0053] Take 2278g of nonionic surfactant P123 (hereinafter referred to as P123) of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer and add it to 100L of 1.8M nitric acid solution. After heating to 35℃, stir at a constant temperature for 6h. After the template agent P123 is completely dissolved, add 1023g of PEG1500 (pore expander) and 1354g of PEG2000 (pore expander). After stirring at a constant temperature of 45℃ for 4h, after the pore expander is completely dissolved, add 4800g of tetraethyl orthosilicate. Hydrolyze at a constant temperature of 45℃ for 12h. Filter to separate the hydrolysis product (solid) and mother liquor.

[0054] Add 40 L of 1.8 M nitric acid solution and 1822 g of nonionic surfactant P123 to the mother liquor. Stir at 35 °C for 6 h. Add 614 g of PEG1500 and 812 g of PEG2000. Stir at 45 °C for 4 h. After the pore-expanding agent is completely dissolved, add 3360 g of tetraethyl orthosilicate. Hydrolyze at 45 °C for 12 h. Filter and separate the solid. Repeat the above process 3 times.

[0055] After the final hydrolysis, the hydrolysis products separated from the previous five hydrolysis cycles were added to the final mother liquor, and the mixture was heated to 100℃ for hydrothermal crystallization for 36 hours. The crystallized products were filtered, washed, dried at 120℃ for 12 hours, and calcined at 550℃ for 4 hours to obtain 8168g of SBA-15 hierarchical porous molecular sieve I, with a yield of 93.1%.

[0056] Example 2

[0057] This embodiment provides a hierarchical porous SBA-15 molecular sieve, the preparation method of which is as follows:

[0058] 2530g of P123 was added to 100L of 2.1M nitric acid solution. The temperature was raised to 35℃ and stirred at a constant temperature for 6 hours. After the template agent P123 was completely dissolved, 1056g of PEG1500 and 1382g of PEG2000 were added. The mixture was stirred at a constant temperature of 45℃ for 4 hours. Then, 4498g of tetraethyl orthosilicate was added. The mixture was hydrolyzed at a constant temperature of 45℃ for 10 hours. The mixture was filtered to separate the hydrolysis product (solid) and the mother liquor.

[0059] Add 50 L of 2.1 M nitric acid solution and 1771 g of nonionic surfactant P123 to the mother liquor. Stir at 35 °C for 6 h. Add 634 g of PEG1500 and 829 g of PEG2000. Stir at 45 °C for 4 h. After the pore-expanding agent is completely dissolved, add 3148 g of tetraethyl orthosilicate. Hydrolyze at 45 °C for 12 h. Filter and separate the solid. Repeat the above process 6 times.

[0060] After the final hydrolysis, the hydrolysis products separated from the previous 8 hydrolysis cycles were added to the final mother liquor, and the mixture was heated to 100℃ for hydrothermal crystallization for 36 hours. The crystallized products were filtered, washed, dried at 120℃ for 16 hours, and calcined at 550℃ for 4 hours to obtain 12368g of SBA-15 hierarchical porous molecular sieve II, with a yield of 92.8%.

[0061] Example 3

[0062] This embodiment provides a hierarchical porous SBA-15 molecular sieve, the preparation method of which is as follows:

[0063] 2350g of P123 was added to 100L of 1.6M hydrochloric acid solution. The temperature was raised to 35℃ and stirred at a constant temperature for 6 hours. After the template agent P123 was completely dissolved, 1041g of PEG1500 and 1362g of PEG2000 were added. The mixture was stirred at a constant temperature of 35℃ for 4 hours. Then, 4436g of silica sol was added and the hydrolysis reaction was carried out at a constant temperature for 10 hours. The mixture was filtered to separate the hydrolysis product (solid) and the mother liquor.

[0064] Add 60 L of 1.6 M nitric acid solution and 1645 g of nonionic surfactant P123 to the mother liquor. Stir at 35 °C for 6 h. Add 572 g of PEG1500 and 750 g of PEG2000. Stir at 45 °C for 4 h. After the pore-expanding agent is completely dissolved, add 3105 g of tetraethyl orthosilicate. Hydrolyze at 45 °C for 12 h. Filter and separate the solid. Repeat the above process 3 times.

[0065] After the final hydrolysis, the hydrolysis products separated from the previous five hydrolysis cycles were added to the final mother liquor, and the mixture was heated to 100℃ for hydrothermal crystallization for 48 hours. The crystallized products were filtered, washed, dried at 120℃ for 24 hours, and calcined at 550℃ for 4 hours to obtain 8392g of SBA-15 hierarchical porous molecular sieve III, with a yield of 93.3%.

[0066] Example 4

[0067] This embodiment provides a hierarchical porous SBA-15 molecular sieve, the preparation method of which is as follows:

[0068] Add 2346g of P123 to 100L of 2.0M hydrochloric acid solution, heat to 35℃ and stir at a constant temperature for 6h. After the template agent P123 is completely dissolved, add 1035g of PEG1500 and 1486g of PEG2000, stir at a constant temperature of 45℃ for 4h, add 5436g of propyl orthosilicate, and hydrolyze at a constant temperature of 45℃ for 10h. Filter to separate the hydrolysis product (solid) and mother liquor.

[0069] Add 50 L of 1.8 M nitric acid solution and 1408 g of nonionic surfactant P123 to the mother liquor. Stir at 35 °C for 6 h. Add 621 g of PEG1500 and 743 g of PEG2000. Stir at 45 °C for 4 h. After the pore-expanding agent is completely dissolved, add 3262 g of tetraethyl orthosilicate. Hydrolyze at 45 °C for 12 h. Filter and separate the solid. Repeat the above process 6 times.

[0070] After the final hydrolysis, the hydrolysis products separated from the previous 8 hydrolysis cycles were added to the final mother liquor, and the mixture was heated to 100℃ for hydrothermal crystallization for 48 hours. The crystallized products were filtered, washed, dried at 120℃ for 24 hours, and calcined at 550℃ for 4 hours to obtain 13258g of SBA-15 hierarchical porous molecular sieve IV, with a yield of 93.7%.

[0071] Example 5

[0072] This embodiment provides a hierarchical porous SBA-15 molecular sieve, the preparation method of which is as follows:

[0073] 2418g of nonionic surfactant P123 (hereinafter referred to as P123) of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer was added to 100L of 1.8M nitric acid solution. The solution was heated to 35℃ and stirred at a constant temperature for 6h. After the template agent P123 was completely dissolved, 1064g of PEG1500 (pore expander) and 1286g of PEG2000 (pore expander) were added. The solution was stirred at a constant temperature of 45℃ for 4h. After the pore expander was completely dissolved, 4800g of tetraethyl orthosilicate was added. The solution was hydrolyzed at a constant temperature of 45℃ for 12h. The solution was filtered to separate the hydrolysis product (solid) and mother liquor.

[0074] Add 40 L of 1.8 M nitric acid solution and 968 g of nonionic surfactant P123 to the mother liquor. Stir at 35 °C for 6 h. Add 426 g of PEG1500 and 514 g of PEG2000. Stir at 45 °C for 4 h. After the pore-expanding agent is completely dissolved, add 2880 g of tetraethyl orthosilicate. Hydrolyze at 45 °C for 12 h. Filter and separate the solid. Repeat the above process 6 times.

[0075] After the final hydrolysis, the hydrolysis products separated from the previous 8 hydrolysis cycles were added to the final mother liquor, and the mixture was heated to 100℃ for hydrothermal crystallization for 36 hours. The crystallized products were filtered, washed, dried at 120℃ for 12 hours, and calcined at 550℃ for 4 hours to obtain SBA-15 hierarchical porous molecular sieve V7268g, with a yield of 91.4%.

[0076] Example 6

[0077] This embodiment provides a hierarchical porous SBA-15 molecular sieve, the preparation method of which is as follows:

[0078] Add 226g of P123 to 10L of 1.8M hydrochloric acid solution, heat to 35℃ and stir at a constant temperature for 6h. After the template agent P123 is completely dissolved, add 164g of PEG1500 and 106g of PEG2000, stir at a constant temperature of 45℃ for 4h, add 546g of propyl orthosilicate, and hydrolyze at a constant temperature of 45℃ for 10h. Filter to separate the hydrolysis product (solid) and mother liquor.

[0079] Add 6 L of 1.8 M nitric acid solution and 176 g of nonionic surfactant P123 to the mother liquor. Stir at 35 °C for 6 h. Add 158 g of PEG1500 and 600 g of PEG2000. Stir at 45 °C for 4 h. After the pore-expanding agent is completely dissolved, add 63 g of tetraethyl orthosilicate. Hydrolyze at 45 °C for 12 h. Filter and separate the solid. Repeat the above process 30 times.

[0080] After the final hydrolysis, the 52 hydrolysis products separated earlier were added to the final mother liquor, and the mixture was heated to 100℃ for hydrothermal crystallization for 48 hours. The crystallized product was filtered, washed, dried at 120℃ for 24 hours, and calcined at 550℃ for 4 hours to obtain 28,800 g of SBA-15 hierarchical porous molecular sieve VI, with a yield of 91.8%.

[0081] The structural parameters of the hierarchical porous SBA-15 molecular sieves in Examples 1-6 above are shown in Table 1.

[0082] Table 1. Structural parameters of the hierarchical porous SBA-15 molecular sieves synthesized in Examples 1-6

[0083] Sample Specific surface area, m 2 / g]] Pore volume, ml / g Average pore diameter, nm Molecular sieve I 862 1.14 17.4 Molecular sieve II 824 1.13 17.5 Molecular sieve III 834 1.15 17.8 Molecular sieve IV 817 1.12 16.3 Molecular sieve V 833 1.13 16.8 Molecular sieve VI 819 1.16 17.1

[0084] The hierarchical porous SBA-15 molecular sieves of Examples 1-4 above were characterized by XRD, N2 adsorption-desorption isotherms and pore size distribution, SEM and TEM. Figure 1 The XRD patterns of the SBA-15 hierarchical porous molecular sieves in Examples 1-4 are shown below. Figure 2 The low-temperature N2 adsorption-desorption isotherms of the SBA-15 hierarchical porous molecular sieve in Examples 1-4 are shown below. Figure 3A and Figure 3B These are the pore distribution curves of the SBA-15 hierarchical porous molecular sieves from Examples 1-4. Figure 4A - Figure 4D TEM images of the SBA-15 hierarchical porous molecular sieves from Examples 1-4.

[0085] The nitrogen adsorption-desorption isotherms, pore distribution curves, and pore structure data obtained above indicate that, compared with mesoporous molecular sieves, the hierarchical SBA-15 molecular sieve prepared in this invention has a larger pore volume, pore size, and specific surface area. This is more conducive to the entry of macromolecular compounds in heavy distillate oils into the pores to participate in chemical reactions, and also facilitates the rapid diffusion and overflow of reaction product molecules, avoiding side reactions such as secondary cracking. As can be seen from the transmission electron microscopy images above, the SBA-15 molecular sieve products of Examples 1-4 all possess a well-defined two-dimensional hexagonal ordered structure, and the morphology and pores of the samples are relatively complete, strongly demonstrating the excellent reproducibility of the preparation and production process of this invention.

Claims

1. A method for preparing a hierarchical porous SBA-15 molecular sieve, comprising the following steps: S1: Dissolve the nonionic surfactant P123, pore expander and inorganic acid in water to obtain a mixture. Add a silicon source and hydrolyze it in the mixture. After hydrolysis, separate the solid and liquid to obtain the hydrolysis product and mother liquor. S2: Repeat the following operations: Add polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander and inorganic acid to the mother liquor obtained in the previous step and dissolve them. Add silicon source and hydrolyze again. After hydrolysis, separate solid and liquid to obtain hydrolysis product and mother liquor again. S3: Combine the hydrolysis products obtained from S1 and S2, add the final mother liquor to perform hydrothermal crystallization on the combined hydrolysis products, dry and calcine the crystallized products to obtain the multi-level porous SBA-15 molecular sieve. in, The pore-expanding agent is a combination of PEG1500 and PEG2000, with a mass ratio of PEG1500:PEG200 = 1:1-4.

2. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The molar ratio of the nonionic surfactant P123 of the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer in S1 to the silicon source is 0.01-0.02:

1.

3. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The molar ratio of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander, and inorganic acid in S1 is 1:3-8:300-1500.

4. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 3, wherein, The molar ratio of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander, and inorganic acid in S1 is 1:4-6:600-1200.

5. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The amounts of the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander, and inorganic acid added to S2 are 30%-80%, 30%-100%, and 10%-60% of the initial amounts, respectively.

6. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 5, wherein, The amounts of the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer nonionic surfactant P123, pore expander, and inorganic acid added to S2 are 40%-60%, 50%-80%, and 30%-50% of the initial amounts, respectively.

7. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The operation described in S2 is repeated 1-80 times.

8. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 7, wherein, The operation described in S2 is repeated 5-60 times.

9. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The hydrolysis reaction temperature of the silicon source described in S1 and S2 is 30-60℃, and the hydrolysis time is 4-20h.

10. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 9, wherein, The hydrolysis reaction temperature of the silicon source is 40-60℃, and the hydrolysis time is 8-16h.

11. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The silicon source includes at least one of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, silica sol, and water glass.

12. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 10, wherein, The silicon source includes at least one of tetraethyl orthosilicate, silica sol, and water glass.

13. The method for preparing the hierarchical porous SBA-15 molecular sieve according to claim 1, wherein, The inorganic acid includes at least one of hydrochloric acid, phosphoric acid, and nitric acid.

14. A multi-level porous SBA-15 molecular sieve obtained by the preparation method of the multi-level porous SBA-15 molecular sieve according to any one of claims 1-13.

15. The hierarchical porous SBA-15 molecular sieve according to claim 14, wherein, The specific surface area of ​​the hierarchical porous SBA-15 molecular sieve is >817 m². 2 / g, pore volume >1.12mL / g, average pore size >16.3nm.

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