A mesoporous NaY molecular sieve and its preparation method

Abstract

The present invention relates to a kind of mesoporous NaY molecular sieve and preparation method thereof, the method comprising: S1, single-stranded nucleic acid mother liquor is subjected to nucleic acid annealing treatment to obtain single-stranded nucleic acid annealing mother liquor; wherein, the sequence length of the single-stranded DNA segment in the single-stranded nucleic acid mother liquor is 15 200bp; S2, a silicon source, the single-stranded nucleic acid annealing mother liquor, water, an alkali source, an aluminum source and a NaY directing agent are mixed to obtain a crystallization precursor solution; S3, the crystallization precursor solution is subjected to crystallization treatment, a solid product is taken out and roasted. The method of the present invention is simple in steps and low in cost, and a mesoporous NaY molecular sieve with high mesopore volume content and narrow mesopore size distribution can be prepared.

Description

Technical Field

[0001] The present application relates to a mesoporous NaY molecular sieve and a preparation method thereof. Background Art

[0002] As an important active component in industrial catalysts, Y-type molecular sieves are widely used in catalytic cracking and other equipment. Y-type molecular sieves have a FAU structure and a pore size of 0.74 nm, making them microporous materials. Against the backdrop of increasingly inferior raw materials in the refining and chemical industry, the limited structural openness of pure microporous materials makes it difficult for some macromolecular reactants, due to size constraints, to contact and react with the acidic centers within the zeolite's micropores. This reduces the efficiency of the catalytic active centers and exacerbates surface coking, impacting catalyst performance and lifespan. By introducing mesopores into microporous molecular sieve materials through specific methods, forming hierarchical molecular sieves can effectively optimize reactant / product diffusion, reduce adverse secondary reactions, and improve overall catalytic performance. Y-type molecular sieves can be directly prepared by hydrothermal synthesis using sol / gel feedstock containing silicon and aluminum sources. Research has shown that by introducing specific materials as mesoporous templates during the synthesis process, hierarchical molecular sieves containing mesopores can be obtained. However, the resulting molecular sieves often lack sufficient mesopore and micropore connectivity, thus failing to significantly improve adsorption or catalytic performance.

[0003] Patent CN100439246C discloses a method for synthesizing composite-pore zeolite molecular sieves using a hard template or composite template. The key to this technology is the use of a common silicon source and its metal atom-doped framework as raw materials, followed by hydrothermal treatment and calcination to produce a composite-pore zeolite molecular sieve with both micropores and mesopores, which serves as an adsorbent, catalyst, and catalyst support. However, this invention uses rice husks, alkaline styrene-based ion exchange resins, or inorganic carbon as hard template materials. The mesopores introduced by the hard template into the synthesized crystals are relatively independent, resulting in limited connectivity between the mesopores in the crystal product, and the active centers of the molecular sieve remain underutilized.

[0004] Patent CN103539151 discloses a method for preparing a high-silicon-to-aluminum Y-type zeolite with abundant secondary pores. The key to this technology is to first synthesize a high-crystallinity, high-silicon-to-aluminum Fe-NaY zeolite, then alternately use ammonium exchange and hydrothermal treatment to obtain a Y-type molecular sieve (USFeY zeolite) with a high silicon-to-aluminum ratio and abundant secondary pores. However, this method relies on a molecular sieve matrix containing heteroatoms, which limits its universality. It also requires multiple post-processing steps, which are complex, energy-intensive, and require a large volume of waste treatment.

[0005] Patent CN107555446 discloses a method for preparing a multi-level pore Y-type molecular sieve. The key to this technology is to use an anionic surfactant as a mesostructure directing agent, mix a sol containing a seed gel, a silicon source, an aluminum source, a co-structure directing agent, and a template, and obtain the multi-level pore Y molecular sieve through hydrothermal synthesis, filtration, washing, drying, and calcination. However, due to the weak interaction between the anionic surfactant as a template and the inorganic silicon species, it is difficult to form a stable mesophase structure. This method requires the use of organosilanes such as aminopropyltrimethoxysilane and p-aminophenyltrimethoxysilane as co-structure directing agents. At the same time, the content of mesopores formed in the crystallized product is limited (the mesopore volume accounts for approximately 20% of the total pore volume). Summary of the Invention

[0006] The purpose of the present invention is to provide a mesoporous NaY molecular sieve and a preparation method thereof. The method of the present invention has simple steps and low cost, and can prepare a mesoporous NaY molecular sieve with high mesopore content and narrow mesopore size distribution range.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a mesoporous NaY molecular sieve, the method comprising:

[0008] S1. performing nucleic acid annealing treatment on a single-stranded nucleic acid mother solution to obtain a single-stranded nucleic acid annealing mother solution; wherein the sequence length of the single-stranded DNA segment in the single-stranded nucleic acid mother solution is 15-200 bp;

[0009] S2, mixing a silicon source, the single-stranded nucleic acid annealing mother solution, water, an alkali source, an aluminum source, and a NaY directing agent to obtain a crystallization precursor solution;

[0010] S3, crystallizing the crystallization precursor solution, taking out the solid product and calcining it.

[0011] Optionally, the sequence length of the single-stranded DNA segment is 20-200 bp, preferably 30-180 bp, and the content of the single-stranded DNA segment in the single-stranded nucleic acid mother solution is 50-200 μmol / L.

[0012] Optionally, the content of the single-stranded DNA segment in the crystallization precursor solution is 5-50 nmol / g.

[0013] Optionally, in step S1, the conditions for the nucleic acid annealing treatment include: a temperature of 88-98° C. and a time of 2-6 min.

[0014] Optionally, step S2 includes:

[0015] SS1, mixing the silicon source, the single-stranded nucleic acid annealing mother solution and water to obtain a first mixed solution;

[0016] SS2, mixing the alkali source, the aluminum source and water to obtain a second mixed solution;

[0017] SS3. Mix the first mixed solution, the second mixed solution and the NaY directing agent to obtain the crystallization precursor solution.

[0018] Optionally, in step S2, the crystallization precursor solution has a schematic molar composition of (4-5)Na2O·Al2O3·(5-12)SiO2·(160-250)H2O;

[0019] The content of the NaY directing agent in the crystallization precursor solution is 8-20% by weight.

[0020] Optionally, the NaY directing agent has an illustrative molar composition of (15-20)Na2O·Al2O3·(10-18)SiO2·(250-380)H2O.

[0021] Optionally, in step S3, the crystallization treatment conditions include: a temperature of 88-110° C. and a time of 12-48 hours.

[0022] Optionally, step S3 further comprises: taking out the solid product, washing and drying it, and then performing the roasting;

[0023] The calcination conditions include: a temperature of 500-600° C. and a calcination time of 4-6 hours.

[0024] Optionally, the silicon source is selected from one or more of water glass, silica sol, ethyl orthosilicate and methyl orthosilicate; the alkali source is selected from sodium hydroxide and / or potassium hydroxide; and the aluminum source is selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate and aluminum sol.

[0025] The second aspect of the present invention provides a mesoporous NaY sieve prepared by the method provided in the first aspect of the present invention.

[0026] Optionally, the mesoporous NaY sieve has an average grain size of 400-600 nm, a mesopore volume of 30-35% of the total pore volume, a silicon-aluminum molar ratio of 1.5-3, and a relative crystallinity of 75-90%.

[0027] Through the above technical solution, the present invention has the following beneficial effects:

[0028] (1) The present invention uses single-stranded nucleic acid as a flexible template. This type of material has mature commercial solid-phase synthesis technology and is easy to obtain. At the same time, the nucleic acid sequence composition can be flexibly designed, and its chain segment length is nanometer-scale and rationally adjustable at the mesopore scale, which is conducive to regulating the connected pore system in the crystallized product. It is suitable for introducing connected mesopores into the molecular sieve material, so that the mesopore size distribution of the prepared molecular sieve is narrower.

[0029] (2) The single-stranded nucleic acid used in the method of the present invention has a flexible one-dimensional linear structure, a low nucleic acid charge density, and good compatibility with the inorganic components in the synthesis system; in addition, the synthesis process does not rely on other co-structure directing agents or mesoporous template agents, further reducing the synthesis cost.

[0030] (3) The mesoporous NaY molecular sieve prepared by the method of the present invention has a high mesopore volume content.

[0031] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 This is the XRD diffraction pattern of the mesoporous NaY molecular sieve prepared in Example 1 of the present invention.

[0034] Figure 2 This is a scanning electron microscope image of the mesoporous NaY molecular sieve prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] A first aspect of the present invention provides a method for preparing a mesoporous NaY molecular sieve, the method comprising: S1, subjecting a single-stranded nucleic acid mother liquid to a nucleic acid annealing treatment to obtain a single-stranded nucleic acid annealing mother liquid; wherein the sequence length of the single-stranded DNA segment in the single-stranded nucleic acid mother liquid is 15-200bp; S2, mixing a silicon source, the single-stranded nucleic acid annealing mother liquid, water, an alkali source, an aluminum source and a NaY directing agent to obtain a crystallization precursor solution; S3, subjecting the crystallization precursor solution to a crystallization treatment, taking out a solid product and calcining it.

[0037] The present invention adopts single-stranded nucleic acid as a flexible mesoporous template agent, takes advantage of the good compatibility of single-stranded nucleic acid with inorganic synthesis systems, does not rely on other co-structure directing agents and multi-step post-processing, and realizes the synthesis of mesoporous NaY molecular sieves through a one-step hydrothermal method. The preparation method is simple and low in cost, and can prepare mesoporous NaY molecular sieves with narrow mesopore size distribution and high mesopore content.

[0038] In one embodiment of the present invention, a single-stranded nucleic acid mother solution is subjected to nucleic acid annealing treatment and then cooled to 20-25° C. Annealing the single-stranded nucleic acid mother solution can convert the complex secondary structure in the nucleic acid mother solution into a linear structure. The nucleic acid has a low charge density and good compatibility with inorganic components in the synthesis system. The nucleic acid is nanometer-sized in length, making it suitable for introducing interconnected mesopores into the microporous molecular sieve material.

[0039] In a specific embodiment of the present invention, the sequence length of the single-stranded DNA segment is 20-200 bp, preferably 30-180 bp, and the content of the single-stranded DNA segment in the single-stranded nucleic acid mother solution is 50-200 μmol / L, preferably 80-180 μmol / L. The single-stranded nucleic acid in the method of the present invention can be commercially obtained, and the above method of the present invention can produce a mesoporous NaY molecular sieve with a narrower mesopore size distribution.

[0040] In a specific embodiment of the present invention, the content of the single-stranded DNA segment in the crystallization precursor solution is 5-50 nmol / g, preferably 10-45 nmol / g.

[0041] According to the present invention, nucleic acid annealing treatment refers to a process in which the complex secondary structure of nucleic acids is thermally dissociated into a linear structure under certain temperature conditions. The temperature of the nucleic acid annealing treatment can be specifically selected based on the melting temperatures of different nucleic acids, as long as the annealing temperature is higher than the melting temperature of the nucleic acid. In a specific embodiment of the present invention, in step S1, the conditions of the nucleic acid annealing treatment include: a temperature of 88-98°C and a time of 2-6 minutes; preferably, a temperature of 90-95°C and a time of 3-5 minutes.

[0042] According to the present invention, the present invention does not impose any specific restrictions on the mixing conditions in step S2. For example, the mixing can be carried out at 20-25°C. In a specific embodiment of the present invention, step S2 includes: SS1, mixing the silicon source, the single-stranded nucleic acid annealing mother solution and water to obtain a first mixed solution; SS2, mixing the alkali source, the aluminum source and water to obtain a second mixed solution; SS3, mixing the first mixed solution, the second mixed solution and the NaY directing agent to obtain the crystallization precursor solution. In this embodiment, by preparing different raw materials into different mixed solutions and then mixing them, it is beneficial to prepare a mesoporous NaY molecular sieve with a narrower mesopore size distribution and a higher mesopore volume content.

[0043] In a specific embodiment of the present invention, in step S2, the crystallization precursor solution has a schematic molar composition of (4-5)Na2O·Al2O3·(5-12)SiO2·(160-250)H2O.

[0044] According to the present invention, the content of the NaY directing agent in the crystallization precursor solution can be maintained in a wide range. In a specific embodiment, the content of the NaY directing agent in the crystallization precursor solution is 8-20 wt %, preferably 10-16 wt %.

[0045] According to the present invention, NaY directing agents are well known to those skilled in the art. In one embodiment of the present invention, the NaY directing agent has an illustrative molar composition of (15-20)Na2O·Al2O3·(10-18)SiO2·(250-380)H2O. Methods for preparing directing agents are also well known to those skilled in the art. Raw materials used to prepare the NaY directing agent can include, for example, deionized water, sodium metaaluminate, sodium hydroxide, sodium silicate, water glass, and the like. In one embodiment, the molar ratio of the raw materials used in preparing the directing agent is (15-20)Na2O:Al2O3:(10-18)SiO2:(250-380)H2O, where Na in the raw materials used to prepare the NaY directing agent is calculated as Na2O, Al as Al2O3, and Si as SiO2.

[0046] According to the present invention, the crystallization treatment is a static crystallization treatment, and the crystallization treatment can be carried out in a heat-resistant sealed container, for example, it can be carried out in a crystallization kettle. The conditions for the crystallization treatment may include: a temperature of 88-110°C and a time of 12-48 hours; preferably, a temperature of 95-105°C and a time of 16-36 hours. The crystallization pressure can be the pressure generated by the reaction itself or an external pressure, preferably the pressure generated by the reaction itself. The method of the present invention uses single-stranded nucleic acid as a flexible template, which is independent of other co-structure directing agents, avoids multi-step post-processing, and can achieve the synthesis of mesoporous NaY-type molecular sieves through a one-step hydrothermal method. The method is simple and easy.

[0047] According to the present invention, the method for removing the solid product is not particularly limited. For example, centrifugal separation, filtration, suction filtration, etc. can be used.

[0048] In a specific embodiment of the present invention, step S3 further includes: washing and drying the solid product after taking it out, and then performing the calcination to remove the single-stranded nucleic acid material. Calcination is well known to those skilled in the art, and can be performed in a muffle furnace or a tube furnace, for example. The conditions for the calcination include: a temperature of 500-600°C and a time of 4-6 hours. The present invention does not impose specific restrictions on the calcination atmosphere, for example, it can be an air atmosphere or an inert gas atmosphere. Washing can be performed with any liquid that does not react with the solid product. In one embodiment, the solid product is washed with ethanol and deionized water in sequence, and each solvent is washed 5-10 times. Drying can be performed in a constant temperature drying oven, and the drying conditions can include: a temperature of 100-150°C and a time of 2-4 hours.

[0049] According to the present invention, the silicon source can be selected from one or more of water glass, silica sol, ethyl orthosilicate and methyl orthosilicate; the alkali source is selected from sodium hydroxide and / or potassium hydroxide; and the aluminum source is selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate and aluminum sol.

[0050] The second aspect of the present invention provides a mesoporous NaY sieve prepared by the method provided in the first aspect of the present invention.

[0051] In a specific embodiment of the present invention, the average grain size of the mesoporous NaY sieve is 400-600nm, the mesopore volume accounts for 30-35% of the total pore volume, the silicon-aluminum molar ratio is 1.5-3, wherein the silicon-aluminum molar ratio refers to the molar ratio of Si element to Al element, and the relative crystallinity is 75-90%.

[0052] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0053] In the following examples, room temperature was 25°C. All raw materials used in the examples and comparative examples were commercially available unless otherwise specified. Water glass was provided by Sinopec Catalyst Qilu Branch, containing 77.6 g / L sodium oxide, 249.6 g / L silicon dioxide, and a modulus of 3.32.

[0054] The relative crystallinity, average grain size, silicon-aluminum molar ratio, micropore volume, and mesopore volume of the molecular sieves in this application are measured as follows:

[0055] The relative crystallinity of the molecular sieve is determined by reference to ASTM D3906-91 and SH / T0340-92 standard methods, with commercial Y molecular sieve as the standard (Tianjin Nanhua Catalyst Co., Ltd., Na-type Y molecular sieve), and the crystallinity of commercial Y molecular sieve is defined as 100%. The sum of the peak heights of the eight diffraction characteristic peaks with a 2θ angle between 14-35° in the XRD spectrum of the crystallized product is multiplied by the half-maximum width of the (533) diffraction peak with a 2θ angle of 23.5° as the diffraction intensity of the molecular sieve, and the crystallinity of the molecular sieve to be tested is calculated by the external standard method. Test instrument: D5005 X-ray diffractometer from Siemens, Germany. Test conditions: Cu target, Kα radiation, solid detector, tube voltage 40kV, tube current 40mA, step scan, step width 0.02°, prefabrication time 2s, scanning range 5°~70°.

[0056] The silicon-aluminum molar ratio of the molecular sieve was quantitatively characterized using X-ray fluorescence. The instrument used was a Rigaku Corporation 3271E X-ray fluorescence spectrometer. Test conditions included pelletizing the powder sample, using a rhodium target, an excitation voltage of 50 kV, and an excitation current of 50 mA. Spectral line intensities of each element were detected using a scintillation counter and a proportional counter, and quantitative and semi-quantitative analysis of elemental content was performed using an external standard method.

[0057] In the examples and comparative examples, the crystal size of the molecular sieve was measured by scanning electron microscopy (SEM), and the sizes of 20 crystals were randomly measured (taking the largest observable size) and the average value was taken to obtain the average crystal size of the molecular sieve sample.

[0058] The pore volume (total pore volume and mesopore volume) and pore size distribution of the molecular sieve were measured using the low-temperature nitrogen adsorption capacity method. The test instrument was a Micromeritics ASAP2400 static nitrogen adsorption instrument. Test conditions: The sample was vacuum degassed at 1.33 Pa and 300°C for 4 hours, then exposed to liquid nitrogen at 77 K for isothermal adsorption and desorption. The adsorption and desorption isotherms were measured, and the pore volume was calculated using the BET equation, and the pore size distribution was calculated using the BJH equation.

[0059] Example 1

[0060] (1) Preparation of NaY directing agent: 4 g of sodium hydroxide solid, 1 g of sodium aluminate solid and 10.0 g of deionized water were thoroughly mixed and stirred at room temperature for 15 minutes. 25 g of water glass was added thereto, and the resulting mixture was stirred at room temperature for 1 hour. The mixture was then placed in a 33°C water bath and allowed to stand for 26 hours to obtain a NaY directing agent having a molar composition of 17.8 Na2O:Al2O3:17.0SiO2:357.9H2O.

[0061] (2) Preparation of single-stranded nucleic acid stock solution: Heat the single-stranded nucleic acid stock solution (concentration 100 μmol / L) to 95°C and hold for 3 minutes, then cool to room temperature to complete the nucleic acid annealing process and obtain the single-stranded nucleic acid stock solution. The nucleic acid sequence in this example is (from 5' end to 3' end, length 40 bp): GACGG CTCAA ACTTT ACTCA TCTCA ACGCA AATTC AACTC (SEQ ID NO. 1).

[0062] (3) Prepare a crystallization precursor solution: fully dissolve water glass in ionized water, mix well to obtain a silicon source solution, add the single-stranded nucleic acid obtained in the previous step to the silicon source solution, mix well at room temperature to obtain a first mixed solution. Fully dissolve sodium hydroxide in deionized water, add aluminum sulfate, and stir at room temperature for 2 hours to obtain a second mixed solution. After mixing the first mixed solution and the second mixed solution, a crystallization mother solution is obtained. 1 g of the directing agent obtained in step (1) is added to 9 g of the crystallization mother solution, and stirred at room temperature for 1 hour to obtain 10 g of a crystallization precursor solution. The content of the single-stranded DNA segment in the crystallization precursor solution is 10 nmol / g, and the crystallization precursor solution has a schematic molar composition of 4.8Na2O·Al2O3·6.5SiO2·216H2O.

[0063] (4) Crystallization: The crystallization precursor solution was placed into a crystallization kettle and crystallized at 95°C for 24 hours using a static crystallization method.

[0064] (5) Post-treatment: After the crystallization is completed, the crystallized mixture is subjected to solid-liquid separation, and is filtered, washed, and dried in sequence. The dried crystallized product is calcined at 550°C for 4 hours to remove the residual single-stranded nucleic acid and obtain a mesoporous NaY molecular sieve, whose XRD diffraction pattern is shown below. Figure 1 As shown in the scanning electron microscope image Figure 2 shown.

[0065] Example 2

[0066] (1) Preparation of NaY directing agent: 4.2 g of sodium hydroxide solid, 1 g of sodium metaaluminate solid and 7.6 g of deionized water were thoroughly mixed and stirred at room temperature for 15 minutes. 20.5 g of water glass was added thereto, and the resulting mixture was stirred at room temperature for 1 hour. The mixture was then placed in a 35°C water bath and allowed to stand for 24 hours to obtain a NaY directing agent having a molar composition of 16.5 Na2O·Al2O3·13.9SiO2·287.7H2O.

[0067] (2) Preparation of single-stranded nucleic acid stock solution: Heat the single-stranded nucleic acid stock solution (concentration 100 μmol / L) to 95°C and hold for 3 minutes, then cool to room temperature to complete the nucleic acid annealing treatment and obtain the single-stranded nucleic acid stock solution. The nucleic acid sequence in this example is (from 5' end to 3' end, sequence length 80 bp): CTCTG TACCT ATCAT CCCAC TTACC GTTCA TCAGCACTAG CTCTG TACCT ATCAT CCCAC TTACC GTTCA TCAGC ACTAG (SEQ ID NO. 2).

[0068] (3) Prepare a crystallization precursor solution: fully dissolve water glass in deionized water, mix well to obtain a silicon source solution; add the single-stranded nucleic acid obtained in the previous step to the silicon source solution, mix well at room temperature to obtain a first mixed solution. Fully dissolve sodium hydroxide in deionized water, add aluminum sulfate, and stir at room temperature for 2 hours to obtain a second mixed solution. Mix the first mixed solution and the second mixed solution to obtain a crystallization mother solution. Add 0.8 g of the directing agent obtained in step (1) to 9.2 g of the crystallization mother solution, stir at room temperature for 2 hours to obtain 10 g of a crystallization precursor solution, the content of the single-stranded DNA segment in the crystallization precursor solution is 50 nmol / g, and the crystallization precursor solution has a schematic molar composition of 4.5Na2O:Al2O3:10SiO2:185H2O.

[0069] (4) Crystallization: The crystallization precursor solution was placed into a crystallization kettle and crystallized at 100°C for 20 h using a static crystallization method.

[0070] (5) Post-treatment: After crystallization, the crystallized mixture is subjected to solid-liquid separation, followed by filtration, washing, and drying. The dried crystallized product is calcined at 520°C for 5 h to remove the residual single-stranded nucleic acid and obtain a mesoporous NaY molecular sieve.

[0071] Example 3

[0072] (1) Preparation of NaY directing agent: 3.9 g of sodium hydroxide solid, 1.05 g of sodium aluminate solid and 11.5 g of deionized water were thoroughly mixed and stirred at room temperature for 15 minutes. 25.5 g of water glass was added thereto, and the resulting mixture was stirred at room temperature for 2 hours. The mixture was then placed in a 37°C water bath and allowed to stand for 20 hours to obtain a NaY directing agent having an illustrative molar composition of 16.9 Na2O·Al2O3·16.5SiO2·362.2H2O.

[0073] (2) Preparation of single-stranded nucleic acid stock solution: Heat the single-stranded nucleic acid stock solution (concentration 200 μmol / L) to 90°C and hold for 4 minutes, then cool to room temperature to complete the nucleic acid annealing treatment and obtain the single-stranded nucleic acid stock solution. The nucleic acid sequence in this embodiment is (from 5' end to 3' end, length is 160 bp): GTTAT CATCA CGTCT AATCC CTGGC AAATA CAATA CTATAGTTAT CATCA CGTCT AATCC CTGGC AAATA CAATA CTATA GTTAT CATCA CGTCT AATCC CTGGCAAATA CAATA CTATA GTTAT CATCA CGTCT AATCC CTGGC AAATA CAATA CTATA (SEQ ID NO. 3).

[0074] (3) Prepare a crystallization precursor solution: fully dissolve the silica sol in deionized water, mix well, and obtain a silicon source solution; add the single-stranded nucleic acid obtained in the previous step to the silicon source solution, mix well at room temperature, and obtain a first mixed solution. Fully dissolve sodium hydroxide in deionized water, add aluminum nitrate, and stir at room temperature for 2 hours to obtain a second mixed solution. Mix the first mixed solution and the second mixed solution to obtain a crystallization mother solution. Add 1.3 g of the directing agent obtained in step (1) to 8.7 g of the crystallization mother solution, stir at room temperature for 2 hours, and obtain 10 g of a crystallization precursor solution. The content of single-stranded DNA segments in the crystallization precursor solution is 20 nmol / g, and the crystallization precursor solution has a schematic molar composition of 4.3Na2O·Al2O3·9SiO2·200H2O.

[0075] (4) Crystallization: The crystallization precursor solution was placed into a crystallization kettle and crystallized at 90°C for 40 hours using a static crystallization method.

[0076] (5) Post-treatment: After crystallization, the crystallized mixture is subjected to solid-liquid separation, followed by filtration, washing, and drying. The dried crystallized product is calcined at 500°C for 6 h to remove the residual single-stranded nucleic acid and obtain a mesoporous NaY molecular sieve.

[0077] Example 4

[0078] The mesoporous NaY molecular sieve was prepared by the same method as in Example 1, except that in step (3), the content of the single-stranded DNA segment in the crystallization precursor solution was 1 nmol / g.

[0079] Example 5

[0080] The mesoporous NaY molecular sieve was prepared by the same method as in Example 1, except that in step (2), the nucleic acid sequence was (from 5' end to 3' end, length 15 bp): GACGG CTCAA ACTTT (SEQ ID NO. 4).

[0081] Example 6

[0082] The mesoporous NaY molecular sieve was prepared by the same method as in Example 1, except that in step (2), the temperature of the nucleic acid annealing treatment was 50° C. and the time was 1 min.

[0083] Example 7

[0084] The mesoporous NaY molecular sieve was prepared by the same method as in Example 1, except that in step (3), water glass, single-stranded nucleic acid mother liquor, deionized water, sodium hydroxide, aluminum sulfate and the NaY directing agent prepared in step (1) of Example 1 were mixed instead of mixing them in steps.

[0085] The content of the directing agent in the obtained crystallization precursor solution was 10 wt %, the content of the single-stranded DNA segment was 10 nmol / g, and the crystallization precursor solution had a schematic molar composition of 4.8Na2O·Al2O3·6.5SiO2·216H2O.

[0086] Comparative Example 1

[0087] The mesoporous NaY molecular sieve was prepared by the same method as in Example 1, except that step (2) was omitted and the single-stranded nucleic acid mother solution was not added when preparing the crystallization precursor solution.

[0088] Comparative Example 2

[0089] Mesoporous NaY molecular sieves were prepared using the same method as in Example 1, except that step (2) was omitted and the single-stranded nucleic acid mother solution was replaced by the chain oligomer polydiallyldimethylammonium chloride (PDDA, Mw 100,000-200,000, innochem, A71079) when preparing the crystallization precursor solution.

[0090] The test results of the relative crystallinity, average grain size and pore structure characteristics of the molecular sieves obtained in each embodiment and comparative example are shown in Table 1.

[0091] Table 1

[0092]

[0093] As can be seen from Table 1, the mesopore volume of the mesoporous NaY molecular sieve obtained by the method of the present invention accounts for more than 21% of the total pore volume, the mesopore volume content is high, the pore size distribution of the mesopores is narrower, and the grain size is small; while the mesopore volume of the comparative sample is less than 10% of the total pore volume, and the mesopore size distribution is wider. Sequence Listing <110> Sinopec Sinopec Petrochemical Research Institute <120> A mesoporous NaY molecular sieve and its preparation method <130> 24365RIPP <160> 4 <170> SIPOSequenceListing 1.0 <210> 1 <211> 40 <212> DNA <213> Artificial Sequence <400> 1 gacggctcaa actttactca tctcaacgca aattcaactc 40 <210> 2 <211> 80 <212> DNA <213> Artificial Sequence <400> 2 ctctgtacct atcatcccac ttaccgttca tcagcactag ctctgtacct atcatcccac 60 ttaccgttca tcagcactag 80 <210> 3 <211> 160 <212> DNA <213> Artificial Sequence <400> 3 gttatcatca cgtctaatcc ctggcaaata caatactata gttatcatca cgtctaatcc 60 ctggcaaata caatactata gttatcatca cgtctaatcc ctggcaaata caatactata 120 gttatcatca cgtctaatcc ctggcaaata caatactata 160 <210> 4 <211> 15 <212> DNA <213> Artificial Sequence <400> 4 gacggctcaa acttt 15

Claims

1. A method for preparing a mesoporous NaY molecular sieve, the method comprising: S1. performing nucleic acid annealing treatment on a single-stranded nucleic acid mother solution to obtain a single-stranded nucleic acid annealing mother solution; wherein the sequence length of the single-stranded DNA segment in the single-stranded nucleic acid mother solution is 15-200 bp; S2, mixing a silicon source, the single-stranded nucleic acid annealing mother solution, water, an alkali source, an aluminum source, and a NaY directing agent to obtain a crystallization precursor solution; S3, crystallizing the crystallization precursor solution, taking out the solid product and calcining it.

2. The method according to claim 1, wherein The sequence length of the single-stranded DNA segment is 20-200 bp, and the content of the single-stranded DNA segment in the single-stranded nucleic acid mother solution is 50-200 μmol / L.

3. The method according to claim 2, wherein: The sequence length of the single-stranded DNA segment is 30-180 bp.

4. The method according to claim 1, wherein The content of the single-stranded DNA segment in the crystallization precursor solution is 5-50 nmol / g.

5. The method according to claim 1, wherein In step S1, the conditions for the nucleic acid annealing treatment include: a temperature of 88-98° C. and a time of 2-6 min.

6. The method according to claim 1, wherein Step S2 includes: SS1, mixing the silicon source, the single-stranded nucleic acid annealing mother solution and water to obtain a first mixed solution; SS2, mixing the alkali source, the aluminum source and water to obtain a second mixed solution; SS3. Mix the first mixed solution, the second mixed solution and the NaY directing agent to obtain the crystallization precursor solution.

7. The method according to claim 1, wherein In step S2, the crystallization precursor solution has a schematic molar composition of (4-5)Na2O·Al2O3·(5-12)SiO2·(160-250)H2O; The content of the NaY directing agent in the crystallization precursor solution is 8-20 wt %.

8. The method according to claim 1, wherein The NaY directing agent has an illustrative molar composition of (15-20)Na2O·Al2O3·(10-18)SiO2·(250-380)H2O.

9. The method according to claim 1, wherein In step S3, the crystallization treatment conditions include: a temperature of 88-110 o C, time is 12-48 hours.

10. The method according to claim 1, wherein Step S3 further comprises: taking out the solid product, washing and drying it, and then performing the roasting; The calcination conditions include: a temperature of 500-600 o C, time is 4-6 hours.

11. The method according to claim 1, wherein The silicon source is selected from one or more of water glass, silica sol, ethyl orthosilicate and methyl orthosilicate; the alkali source is selected from sodium hydroxide and / or potassium hydroxide; and the aluminum source is selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate and aluminum sol.

12. The mesoporous NaY molecular sieve prepared by the method according to any one of claims 1 to 11.

13. The mesoporous NaY molecular sieve according to claim 12, wherein: The average grain size of the mesoporous NaY molecular sieve is 400-600 nm, the mesopore volume accounts for 30-35% of the total pore volume, the silicon-aluminum molar ratio is 1.5-3, and the relative crystallinity is 75-90%.

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