Mesoporous NaY molecular sieve and preparation method thereof

Abstract

The invention provides a mesoporous NaY molecular sieve and a preparation method thereof. The preparation method comprises the following steps: mixing a first silicon source, a first aluminum source, a structure-directing agent and an alkaline earth metal compound, and performing primary crystallization to obtain a precursor solution; adding a second aluminum source into the precursor solution, stirring and mixing to obtain metal aluminosilicate gel, and performing secondary crystallization on the metal aluminosilicate gel to obtain the mesoporous NaY molecular sieve. According to the preparation method of the mesoporous NaY molecular sieve, provided by the invention, an organic template agent and a post-treatment step are not needed, and the introduction time sequence and removal of alkaline earth metal ions are controlled through step-by-step crystallization, so that in-situ generation of mesopores in a molecular sieve framework is realized. The NaY molecular sieve can maintain high crystallinity, and has large mesoporous specific surface area and mesoporous introduction amount.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of molecular sieve synthesis, and particularly relates to a mesoporous NaY molecular sieve and a preparation method thereof. BACKGROUND

[0002] The single microporous structure of NaY molecular sieve limits catalytic conversion reactions involving macromolecules, hinders the diffusion of heavy oil macromolecules in the pores, and leads to poor accessibility of the acid active centers. In order to improve the cracking ability of NaY molecular sieve for heavy oil and other macromolecules, mesoporous structures need to be introduced into NaY molecular sieve to improve the diffusion rate of heavy oil macromolecules in the pores and improve the accessibility of the acid active centers. Therefore, the synthesis of NaY molecular sieve with intracrystalline mesopores has attracted more and more attention.

[0003] Hydrothermal treatment (for example, CN1078819C, CN114604876A, etc.) is the earliest technology to obtain NaY molecular sieve with mesoporous structure. The original powder of NaY molecular sieve is used as raw material, and the mesoporous ultra-stable (USY) molecular sieve with gradient pores is obtained through multiple ammonium ion exchange and hydrothermal treatment, which effectively improves the silicon-aluminum ratio of the framework. However, this method needs to go through multiple ammonium exchange and hydrothermal treatment, the process is complex, high-temperature hydrothermal treatment will cause lattice collapse, and the treatment cost of wastewater containing nitrogen is too high.

[0004] The template method refers to a method of constructing mesopores by introducing various mesoporous templates, including hard templates such as active carbon materials (for example, CN106809857B) or soft templates such as surfactants (for example, CN107555446B, CN112723373B, CN109692656B, CN103214003B, etc.). The mesoporous NaY molecular sieve synthesized by this method has high relative crystallinity, uniform mesopore size, and ordered pore channel penetration. However, this method also has many problems, for example, the yield of the hard template method is low and has no industrial production value; the cost of the soft template method is high, and high-temperature calcination is needed to remove the template agent, which will cause the release of a large amount of ammonia-containing waste gas. Therefore, the synthesis of mesoporous inorganic system has always been the research goal of researchers.

[0005] Transition metal elements replace Si or Al in the framework of molecular sieve to form heteroatomic molecular sieve. The bond length and bond angle of M-O bond in the heteroatomic molecular sieve are different from those of Al-O bond. These sites are extremely unstable and are preferentially removed in subsequent steam treatment, thereby obtaining mesoporous structures in the framework. Guo et al (Guo et al, Microporous and Mesoporous Materials, 2015, 211:192-199) introduced Fe 3+The framework introduced into the NaY molecular sieve is hydrothermally calcined after treatment to prepare a uniformly distributed mesoporous structure; Mi et al (Mi et al, Journal of Catalysis, 2017, 347: 116-126) introduce B 3+ The framework introduced into the NaY molecular sieve is hydrothermally calcined after treatment to prepare a uniformly distributed mesoporous structure; Mi et al (Mi et al, Journal of Catalysis, 2017, 347: 116-126) introduce B 3+ The synthesis system of the NaY molecular sieve is introduced into the synthesis system, and the synthesized molecular sieve is subjected to water vapor calcination treatment at a lower temperature, so that the framework silicon aluminum ratio and the mesoporous volume of the NaY molecular sieve subjected to the conventional high-temperature hydrothermal calcination treatment can be obtained. However, these methods for preparing the NaY molecular sieve all need subsequent ammonium ion exchange and hydrothermal treatment processes, and the problem of treating ammonia-containing wastewater has not been fundamentally solved.

[0006] Therefore, although the above work has great significance for synthesizing mesoporous NaY molecular sieves, for the NaY molecular sieve, how to avoid the subsequent complicated ammonium exchange and high-energy consumption hydrothermal treatment process while introducing a large number of intracrystalline mesopores is still a great challenge. SUMMARY

[0007] To solve the above technical problems, the purpose of the present application is to provide a mesoporous NaY molecular sieve and a preparation method thereof. By controlling the timing of adding the alkaline earth metal compound in steps, a NaY molecular sieve with intracrystalline mesoporous structure is prepared.

[0008] To achieve the above purpose, the present application provides a preparation method of a mesoporous NaY molecular sieve, wherein the preparation method comprises the following steps:

[0009] (1) mixing a first silicon source, a first aluminum source, a structure directing agent and an alkaline earth metal compound, and obtaining a precursor solution after one-step crystallization;

[0010] (2) adding a second aluminum source to the precursor solution, stirring and mixing to obtain a metal aluminosilicate gel, and performing two-step crystallization on the metal aluminosilicate gel to obtain a mesoporous NaY molecular sieve. The compound of the alkaline earth metal has a defect structure promoting effect.

[0011] According to a specific embodiment of the present application, preferably, the molar ratio of silicon, aluminum, sodium and water in the metal aluminosilicate gel is (5-20):1:(2-20):(150-300) in terms of SiO2, Al2O3, Na2O and H2O.

[0012] According to a specific embodiment of the present application, preferably, the content of the compound of alkaline earth metal is in a molar ratio of 0.01-0.2 of the alkaline earth metal to the silicon element in the metallosilicate gel, wherein M represents the oxide of the alkaline earth metal.

[0013] According to a specific embodiment of the present application, preferably, the mass of Al in the structure-directing agent accounts for 3%-12% of the mass of Al in the metallosilicate gel, calculated based on Al2O3.

[0014] According to a specific embodiment of the present application, preferably, the compound of alkaline earth metal comprises one or more than two combinations of metal salts and metal hydroxides containing Be, Mg, Ca, Sr, Ba, such as beryllium sulfate tetrahydrate, strontium chloride hexahydrate, calcium chloride, strontium nitrate, calcium citrate, magnesium hydroxide, barium chloride dihydrate, strontium acetate, calcium sulfate, strontium hydroxide, magnesium citrate, strontium sulfate, barium nitrate, calcium acetate, etc.

[0015] According to a specific embodiment of the present application, preferably, the temperature of the first crystallization is 60-80℃, and the time of the first crystallization is 1-28h.

[0016] According to a specific embodiment of the present application, preferably, the temperature of the second crystallization is 90-180℃, and the time of the second crystallization is 16-72h. More preferably, the temperature of the second crystallization is 90-100℃.

[0017] The inventor of the present application found that the step-by-step crystallization can realize the sequential growth and shedding of alkaline earth metal in the framework of molecular sieve, thereby realizing the in-situ introduction of intracrystalline mesoporous structure. The mechanism of the process is as follows: in the first crystallization process, the lower temperature is not conducive to the entry of Al ions into the framework of molecular sieve, and the introduction of the single aluminum source reduces the alkalinity of the system, and the superimposed effect of the two helps the entry of alkaline earth metal ions into the framework of molecular sieve. In the second crystallization process, the high temperature is conducive to the entry of Al ions into the framework of molecular sieve, and the subsequent addition of strong alkaline aluminum source increases the alkalinity of the system, which makes the M-O bond of the framework of molecular sieve unstable, causing the shedding of alkaline earth metal ions from the framework of molecular sieve, thereby causing structural defects of the crystal and promoting the generation of a large amount of mesopores. Therefore, in the step-by-step crystallization process of NaY molecular sieve, the present application utilizes the in-situ introduction of alkaline earth metal ions at a lower crystallization temperature and the generation of mesopores by shedding from the framework at a higher crystallization temperature.

[0018] According to a specific embodiment of the present application, preferably, the raw material of the structure-directing agent comprises a second silicon source, a third aluminum source, an alkali source and water, and the molar ratio of the second silicon source, the third aluminum source, the alkali source and water is (10-30):1:(10-30):(260-480), calculated based on SiO2, Al2O3, Na2O and H2O.

[0019] In some specific embodiments, preferably, the structure-directing agent is obtained by aging a mixture of a second silicon source, a third aluminum source, an alkali source, and water. More preferably, the aging temperature is 30-50°C, and the aging time is 1-28 hours.

[0020] In some specific implementations, preferably, the mixing temperature in step (1) is 25-60°C; and the mixing temperature in step (2) is 25-80°C.

[0021] In some specific implementations, preferably, the secondary crystallization process further includes steps of cooling, washing, filtration, and drying; the drying temperature is 60-180℃, preferably 60-120℃.

[0022] According to a specific embodiment of the present invention, preferably, the first silicon source includes one or more of the following: tetraethyl orthosilicate, silica sol, silica powder, silicic acid, fumed silica, and water glass; the second silicon source includes one or more of the following: tetraethyl orthosilicate, silica sol, silica powder, silicic acid, fumed silica, and water glass. The terms "first silicon source" and "second silicon source" are used only for name differentiation and may represent the same or different substances.

[0023] According to a specific embodiment of the present invention, preferably, the first aluminum source includes one or more combinations of high-alkali sodium aluminate, low-alkali sodium aluminate, sodium aluminate, alumina, aluminum sulfate, aluminum isopropoxide, boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide, and aluminum nitrate; the second aluminum source includes one or more combinations of high-alkali sodium aluminate, low-alkali sodium aluminate, sodium aluminate, alumina, aluminum sulfate, aluminum isopropoxide, boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide, and aluminum nitrate; and the third aluminum source includes one or more combinations of high-alkali sodium aluminate, low-alkali sodium aluminate, sodium aluminate, alumina, aluminum sulfate, aluminum isopropoxide, boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide, and aluminum nitrate. The terms "first aluminum source," "second aluminum source," and "third aluminum source" are used only for name differentiation and may represent the same or different substances.

[0024] According to a specific embodiment of the present invention, preferably, the alkali source includes Na₂O and / or NaOH. For the aforementioned silicon source, aluminum source, alkali source, etc., the same substance can be selected under certain circumstances, as long as a predetermined molar ratio is met.

[0025] The present invention also provides a mesoporous NaY molecular sieve, which is obtained by the above preparation method.

[0026] According to a specific embodiment of the present invention, preferably, the mesoporous NaY molecular sieve has a mesoporous specific surface area of ​​60-130 m². 2·g -1 (preferably 81-125m) 2 ·g -1 The mesopore volume is 0.05-0.20 cm³. 3 ·g -1 (Preferred size: 0.07-0.15cm) 3 ·g -1 ).

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

[0028] (1) The method for preparing NaY molecular sieve with intracrystalline mesoporous structure provided by the present invention does not require any organic template agent or hydrothermal post-treatment step. By controlling the timing and sequence of introduction and removal of alkaline earth metal ions through stepwise crystallization, intracrystalline mesoporous structure is generated in situ in the molecular sieve framework.

[0029] (2) The method for preparing NaY molecular sieve with intracrystalline mesopores provided by the present invention can control the mesopore content by controlling the amount of alkaline earth metal salt or alkaline earth metal hydroxide introduced. The higher the amount of alkaline earth metal introduced, the higher the mesopore content.

[0030] (3) The mesoporous NaY molecular sieve provided by the present invention can maintain a high degree of crystallinity and has a large mesoporous specific surface area and mesoporous introduction amount. Attached Figure Description

[0031] Figure 1 The XRD patterns of NaY molecular sieves prepared in Comparative Example 1 and Examples 6, 9, 10, 12, and 14 are shown.

[0032] Figure 2 Nitrogen adsorption-desorption isotherms of mesoporous NaY molecular sieves prepared in Examples 6, 9, 10, 12, and 14.

[0033] Figure 3 The pore size distribution diagrams are for the mesoporous NaY molecular sieves prepared in Examples 6, 9, 10, 12, and 14.

[0034] Figure 4 This is a high-resolution transmission electron microscope image of the mesoporous NaY molecular sieve prepared in Example 6. Detailed Implementation

[0035] 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.

[0036] The water glass, high-alkali sodium aluminate, low-alkali sodium aluminate, and aluminum sulfate used in the examples and comparative examples were from Lanzhou Petrochemical Company of China National Petroleum Corporation and were industrial products; the remaining raw materials were commercially available and were of analytical grade.

[0037] The molecular sieves provided in the examples and comparative examples were tested using the following analytical instruments:

[0038] 1. Phase analysis and confirmation were performed using a Shimadzu XRD-7000 X-ray crystal powder diffractometer. Instrument parameters: Cu-Ka rays, wavelength 0.1543 nm, tube voltage 40 kV, tube current 30 mA. Sample testing conditions: scanning angle 5°-40°, scanning speed 8° / min.

[0039] 2. The adsorption-desorption isotherms of the samples were determined at liquid nitrogen temperature using an ASAP2020M fully automated adsorption instrument manufactured by Micromeritics, USA. Nitrogen gas was used as the adsorbate. The T-plot model was used to distinguish the internal and external surface areas of the samples. The pore volume and pore size distribution were determined by the static volumetric method, thereby calculating the pore structure parameters.

[0040] 3. To observe the mesopores directly, a transmission electron microscope (TEM) was used. The instrument model was JEM-2100LaB6 high-resolution transmission electron microscope with an accelerating voltage of 200kV and a magnification of 50-1500K times.

[0041] The preparation process of the NaY molecular sieve structure directing agent used in the examples and comparative examples is as follows:

[0042] The silicon source used in preparing the following structure-directing agent is water glass (with technical specifications of 6.89 wt% Na2O, 19.81 wt% SiO2, and 73.30 wt% H2O); the aluminum source and alkali source are high-alkali sodium aluminate (with technical specifications of 21.13 wt% Na2O, 3.10 wt% Al2O3, and 75.77 wt% H2O); the alkali source can also be NaOH.

[0043] The silicon sources used in preparing the molecular sieves in the examples and comparative examples were water glass (with technical specifications of 6.89 wt% Na2O, 19.81 wt% SiO2, and 73.30 wt% H2O), silica sol (with technical specifications of 40 wt% SiO2 and 60 wt% H2O), and silicic acid (with technical specifications of 99 wt% H2SiO3). The aluminum and alkali sources were high-alkali sodium aluminate (with technical specifications of 21.13 wt% Na2O, 3.10 wt% Al2O3, and 75.77 wt% H2O), low-alkali sodium aluminate (with technical specifications of 11.98 wt% Na2O, 8.07 wt% Al2O3, and 79.95 wt% H2O), and aluminum sulfate octadechydrate (with a purity of 99 wt%).

[0044] 1. Prepare NaY molecular sieve structure directing agent according to the molar ratio of Na2O:Al2O3:SiO2:H2O=12:1:10:260. Stir 126.20g of water glass and 137.31g of high-alkali sodium aluminate at room temperature until uniform, and age at 35℃ for 8h to obtain white gel-like NaY molecular sieve structure directing agent (1).

[0045] 2. Prepare NaY molecular sieve structure directing agent according to the molar ratio of Na2O:Al2O3:SiO2:H2O=30:1:28:480. Stir 227.15g of water glass and 88.27g of high-alkali sodium aluminate at room temperature, and age at 30℃ for 10h to obtain white gel-like NaY molecular sieve structure directing agent (2).

[0046] 3. Prepare NaY molecular sieve structure directing agent according to the molar ratio of Na2O:Al2O3:SiO2:H2O=16:1:15:320. Stir 151.44g of water glass and 109.85g of high-alkali sodium aluminate at room temperature, and age at 50℃ for 12h to obtain white gel-like NaY molecular sieve structure directing agent (3).

[0047] 4. Prepare NaY molecular sieve structure directing agent according to the molar ratio of Na2O:Al2O3:SiO2:H2O=20:1:18:360. Stir 201.91g of water glass and 122.05g of high-alkali sodium aluminate at room temperature, and age at 45℃ for 16h to obtain white gel-like NaY molecular sieve structure directing agent (4).

[0048] 5. Prepare NaY molecular sieve structure directing agent according to the molar ratio of Na2O:Al2O3:SiO2:H2O=24:1:22:410. Stir 252.39g of water glass and 125.83g of high-alkali sodium aluminate at room temperature, and age at 35℃ for 20h to obtain white gel-like NaY molecular sieve structure directing agent (5).

[0049] 6. Prepare NaY molecular sieve structure directing agent according to the molar ratio of Na2O:Al2O3:SiO2:H2O=28:1:26:460. Stir 181.72g of water glass and 76.05g of high-alkali sodium aluminate at room temperature until uniform, and age at 40℃ for 24h to obtain white gel-like NaY molecular sieve structure directing agent (6).

[0050] Example 1

[0051] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0052] (1) Dissolve 9.46g of aluminum sulfate octadechydrate in 11.91g of deionized water to obtain an aluminum sulfate solution. Add 3.13g of beryllium sulfate tetrahydrate, the above aluminum sulfate solution, and 5.27g of directing agent (1) to 47.95g of water glass. After stirring evenly at 25°C, crystallize at 60°C for 20h to obtain a precursor solution.

[0053] (2) 5.89 g of high-alkali sodium aluminate was added to the above precursor solution and stirred at 25 °C until the system was homogeneous to obtain metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.6:1:10:200. The gel was crystallized at 90 °C for 24 h. The product was washed, filtered and dried to obtain mesoporous Be-NaY molecular sieve.

[0054] Example 2

[0055] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0056] (1) Add 26.65g of aluminum sulfate octadeca to 108.79g of deionized water to prepare a solution. Add the above aluminum sulfate solution and 4.01g of strontium chloride hexahydrate to 70.31g of silica sol and stir evenly. Add 16.33g of directing agent. (3) Mix at 60°C and crystallize at 80°C for 18h to obtain the precursor solution.

[0057] (2) 14.03g of solid sodium aluminate was added to the above precursor solution and stirred at 80°C until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.6:1:10:200. The gel was crystallized at 90°C for 24h. The obtained product was washed, filtered and dried to obtain mesoporous Sr-NaY molecular sieve.

[0058] Example 3

[0059] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0060] (1) Dissolve 9.53g of aluminum nitrate in 23.58g of deionized water to obtain an aluminum nitrate solution. Mix 33.56g of silicic acid and 11.38g of sodium hydroxide solution to obtain an alkaline sodium silicate solution. Add 1.26g of calcium chloride, 6.88g of directing agent (5) and the above aluminum nitrate solution to the alkaline sodium silicate solution. Mix at 45°C. After dissolution, crystallize at 80°C for 18h to obtain a precursor solution.

[0061] (2) 11.38 g of low-alkali sodium aluminate was added to the above precursor solution and stirred at 55 °C until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.3:1:8.5:210. The gel was crystallized at 180 °C for 48 h. The product was washed, filtered and dried to obtain mesoporous Ca-NaY molecular sieve.

[0062] Example 4

[0063] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0064] (1) Dissolve 6.93g of strontium nitrate and 15.43g of aluminum sulfate octahydrate in 63.27g of deionized water to obtain a mixed solution of aluminum sulfate and strontium nitrate. Add the solution to 126.49g of water glass and add 34.63g of directing agent (2). Stir evenly at 50°C and crystallize at 80°C for 8h to obtain a precursor solution.

[0065] (2) 41.66g of low-alkali sodium aluminate was added to the above precursor solution and stirred at 70℃ until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.3:1:8.5:210. The gel was crystallized at 110℃ for 48h. The obtained product was washed, filtered and dried to obtain mesoporous Sr-NaY molecular sieve.

[0066] Example 5

[0067] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0068] (1) Add 4.14g of calcium citrate, 102.39g of aluminum sulfate solution and 22.02g of directing agent (4) to 138.82g of water glass. After stirring evenly at 60℃, crystallize at 70℃ for 12h to obtain the precursor solution.

[0069] (2) Add 15.08g of high-alkali sodium aluminate to the above precursor solution, stir at 75℃ until the system is homogeneous, and obtain metal aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O=2.5:1:10:240. Crystallize at 120℃ for 24h. The obtained product is washed, filtered and dried to obtain mesoporous Ca-NaY molecular sieve.

[0070] Example 6

[0071] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0072] (1) Add 132g aluminum sulfate solution, 2.02g magnesium hydroxide and 27.51g directing agent (3) to 185.97g water glass, stir evenly at 45℃, and crystallize at 70℃ for 12h to obtain precursor solution.

[0073] (2) 29.28g of high-alkali sodium aluminate was added to the above precursor solution and stirred at 65℃ until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.7:1:9.5:230. The gel was crystallized at 140℃ for 24h. The obtained product was washed, filtered and dried to obtain mesoporous Mg-NaY molecular sieve.

[0074] Example 7

[0075] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0076] (1) Mix 23.03g of silica sol and 8g of sodium hydroxide solution, add 2.95g of aluminum chloride and 2.45g of barium chloride dihydrate and stir evenly, and add 6.88g of directing agent (6). Mix at 55°C and crystallize at 70°C for 12h to obtain the precursor solution.

[0077] (2) 7.55g of high-alkali sodium aluminate was added to the above precursor solution and stirred at 75℃ until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.7:1:9.5:230. The gel was crystallized at 110℃ for 72h. The obtained product was washed, filtered and dried to obtain mesoporous Ba-NaY molecular sieve.

[0078] Example 8

[0079] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0080] (1) Dissolve 5.81g of strontium acetate and 24.14g of aluminum sulfate octadeca in 53.12g of deionized water to obtain a mixed solution of aluminum sulfate and strontium acetate. Then add 178.53g of water glass and 34.94g of directing agent. (5) Stir evenly at 55°C and crystallize at 80°C for 16h to obtain a precursor solution.

[0081] (2) Add 38.93g of low-alkali sodium aluminate to the above precursor solution, stir at 75°C until the system is homogeneous, and obtain metal aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O=3.3:1:9.5:200. Crystallize at 120°C for 24h. The obtained product is washed, filtered, and dried at 120°C to obtain mesoporous NaY molecular sieve.

[0082] Example 9

[0083] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0084] (1) Dissolve 11.71g of aluminum sulfate octadecylhydrate in 28.18g of deionized water to obtain an aluminum sulfate solution. Add the aluminum sulfate solution and 3.57g of calcium sulfate to 69.74g of water glass and add 6.32g of directing agent. After stirring evenly at 60℃, crystallize at 70℃ for 16h to obtain a precursor solution.

[0085] (2) 5.29 g of high-alkali sodium aluminate was added to the above precursor solution and stirred at 80 °C until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.9:1:12:260. The gel was crystallized at 95 °C for 48 h. The product was washed, filtered and dried to obtain mesoporous Ca-NaY molecular sieve.

[0086] Example 10

[0087] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0088] (1) Add 83.34g of aluminum sulfate solution to 182.98g of water glass, and then add 3.98g of strontium hydroxide and 25.47g of directing agent. (3) Stir evenly at 55℃, and then crystallize at 70℃ for 16h to obtain the precursor solution.

[0089] (2) Add 22.97g of high-alkali sodium aluminate to the above precursor solution and stir at 80℃ until the system is homogeneous to obtain metal aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O=2.6:1:10:200. Crystallize at 100℃ for 24h. The obtained product is washed, filtered and dried to obtain mesoporous Sr-NaY molecular sieve.

[0090] Example 11

[0091] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0092] (1) Dissolve 5.81g magnesium citrate in 83.52g aluminum sulfate solution to obtain a mixed solution of aluminum sulfate and magnesium citrate. Then add 188.03g water glass and 27.51g directing agent. (5) Stir evenly at 50℃ and crystallize at 70℃ for 16h to obtain precursor solution.

[0093] (2) Add 2.04 g of low-alkali sodium aluminate to the above precursor solution, stir at 80 °C until the system is homogeneous, and obtain metal aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O=3.3:1:16:300. Crystallize at 110 °C for 24 h. The obtained product is washed, filtered and dried to obtain mesoporous Mg-NaY molecular sieve.

[0094] Example 12

[0095] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0096] (1) Add 3.14g of strontium sulfate and 61.71g of aluminum sulfate solution to 140.08g of water glass and stir evenly. Add 13.41g of directing agent. (4) Stir evenly at 55℃ and crystallize at 70℃ for 18h to obtain the precursor solution.

[0097] (2) Add 49.09 g of high-alkali sodium aluminate to the above precursor solution and stir at 55 °C until the system is homogeneous to obtain metal aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O=3.3:1:16:300. Crystallize at 100 °C for 48 h. The obtained product is washed, filtered and dried to obtain mesoporous Sr-NaY molecular sieve.

[0098] Example 13

[0099] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0100] (1) Mix 34.69g silica sol, 5.09g aluminum nitrate, 3.76g barium nitrate, 9.11g directing agent (4) and 42.53g deionized water at 55°C and crystallize at 80°C for 24h to obtain a precursor solution.

[0101] (2) 26.26g of high-alkali sodium aluminate was added to the above-mentioned solution and stirred at 75°C until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=3.0:1:12:240. The gel was crystallized at 110°C for 72h. The obtained product was washed, filtered and dried to obtain mesoporous Ba-NaY molecular sieve.

[0102] Example 14

[0103] This embodiment provides a method for preparing mesoporous NaY molecular sieves, the specific steps of which are as follows:

[0104] (1) Dissolve 21.22g of aluminum sulfate octadecylhydrate in 60.89g of deionized water to obtain an aluminum sulfate solution. Add 4.86g of calcium acetate, 67.61g of water glass and 21.87g of directing agent (6) to the solution. Mix evenly at 50°C and crystallize at 80°C for 24h to obtain a precursor solution.

[0105] (2) 18.77g of high-alkali sodium aluminate was added to the above-mentioned solution and stirred at 65°C until the system was homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.1:1:7:270. The gel was crystallized at 100°C for 48h. The product was washed, filtered and dried to obtain mesoporous Ca-NaY molecular sieve.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing conventional NaY molecular sieves, including the following steps:

[0108] 61.95g of aluminum sulfate solution was slowly added dropwise to 139.07g of water glass while stirring vigorously. After stirring evenly, 17.07g of high-alkali sodium aluminate and 15.28g of directing agent (1) were added to obtain aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.6:1:10:200. After stirring until the system was uniform, it was crystallized at 100℃ for 24h. The obtained product was washed, filtered and dried to obtain conventional NaY molecular sieve.

[0109] Comparative Example 2

[0110] This comparative example uses the exact same material ratio as Example 1, the difference being that it only uses one-step crystallization instead of step-by-step crystallization. The specific steps are as follows:

[0111] (1) Dissolve 9.46g of aluminum sulfate octadechydrate in 11.91g of deionized water to obtain an aluminum sulfate solution. Add 3.13g of beryllium sulfate tetrahydrate, the above aluminum sulfate solution, 5.89g of high-alkali sodium aluminate and 5.27g of directing agent (1) to 47.95g of water glass and stir evenly to obtain aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O=2.6:1:10:200. Crystallize at 90℃ for 24h. The obtained product is washed, filtered and dried to obtain mesoporous Be-NaY molecular sieve.

[0112] The pore structure parameters of the mesoporous molecular sieves prepared in Examples 1-14 and Comparative Examples 1-2 are compared with those of conventional molecular sieves. The results are shown in Table 1. Among them, S... total S represents the total specific surface area. ext V represents the specific surface area of ​​mesopores. total V represents the total pore volume. meso Represents the volume of mesopores.

[0113] Table 1. Pore structure parameters of samples from Examples 1-14 and Comparative Examples 1-2

[0114]

[0115]

[0116] According to the data in Table 1, the mesoporous NaY molecular sieve provided in Example 6 has a mesoporous specific surface area of ​​115.8 m². 2 ·g -1 The mesopore volume is 0.15 cm³. 3 ·g -1 The mesopore volume of conventional NaY molecular sieves (Comparative Example 1) is 0.04 cm³. 3 Therefore, the mesoporous NaY molecular sieve provided in Example 6 has a mesopore volume approximately four times that of conventional NaY molecular sieves. Furthermore, compared to Comparative Example 1, Comparative Example 2 did not show a significant increase in either the specific surface area or the pore volume of the mesopores, indicating that introducing Be species into the NaY molecular sieve synthesis system without stepwise crystallization does not effectively increase the mesopore specific surface area and pore volume of the product molecular sieve. This result demonstrates that the stepwise crystallization operation in this invention is crucial for the introduction of mesopores.

[0117] Figure 1 XRD patterns of NaY molecular sieves prepared in Comparative Example 1 and Examples 6, 9, 10, 12, and 14. From...Figure 1 It can be seen that, compared with Comparative Example 1, the mesoporous NaY molecular sieves provided in Examples 6, 9, 10, 12, and 14 are typical Y-type molecular sieves. Furthermore, as shown in Table 1, although the relative crystallinity of the molecular sieves in Examples 6, 9, 10, 12, and 14 decreased slightly, it remained at a relatively high level overall, indicating that the introduction of alkaline earth metals did not significantly affect the crystallization process of the NaY molecular sieves.

[0118] Figure 2 This is the N2 adsorption-desorption isotherm of the mesoporous NaY molecular sieves prepared in Examples 6, 9, 10, 12, and 14 of this invention. (The remaining text appears to be a fragment and requires further context for accurate translation.) Figure 2 As can be seen from the N2 adsorption-desorption isotherms, the adsorption-desorption isotherms of the mesoporous NaY molecular sieves provided in Examples 6, 9, 10, 12, and 14 are type IV curves with H3-type hysteresis loops, exhibiting obvious characteristics of mesoporous materials. This verifies that the present invention has successfully prepared a mesoporous NaY molecular sieve material.

[0119] Figure 3 This is a pore size distribution diagram for Embodiments 6, 9, 10, 12, and 14 of this invention. Figure 3 As can be seen from the pore size distribution curves, the mesoporous NaY molecular sieves provided in Examples 6, 9, 10, 12, and 14 have obvious mesoporous distribution in the range of 2-10 nm.

[0120] Figure 4 The image shows a high-resolution transmission electron microscope (TEM) image of the sample from Example 6 of this invention. A clear mesoporous distribution can be observed in the image, indicating that this invention successfully introduced a clear mesoporous structure into the NaY molecular sieve framework.

Claims

1. A process for the preparation of a mesoporous NaY molecular sieve, wherein, The preparation method comprises the following steps: (1) mixing a first silicon source, a first aluminum source, a structure directing agent and a compound of an alkaline earth metal, and after one-time crystallization, a precursor solution is obtained; (2) adding a second aluminum source to the precursor solution, and after stirring and mixing, a metal silicoaluminate gel is obtained, and the metal silicoaluminate gel is subjected to two-time crystallization to obtain a mesoporous NaY molecular sieve; In terms of SiO2, Al2O3, Na2O and H2O, the molar ratio of silicon element, aluminum element, sodium element and water in the metal silicoaluminate gel is (5-20):1:(2-20):(150-300); The content of the compound of the alkaline earth metal and the molar ratio of silicon element in the metal silicoaluminate gel are M / SiO2=0.01-0.2, wherein M represents the oxide of the alkaline earth metal; In terms of Al2O3, the mass of Al in the structure directing agent accounts for 3%-12% of the mass of Al in the metal silicoaluminate gel.

2. The production method according to claim 1, wherein, The compound of the alkaline earth metal comprises one or a combination of more than two of metal salts and metal hydroxides containing Be, Mg, Ca, Sr and Ba.

3. The production method according to claim 1, wherein The temperature of the one-time crystallization is 60-80°C, and the time of the one-time crystallization is 1-28h.

4. The production method according to claim 1, wherein The temperature of the two-time crystallization is 90-180°C, and the time of the two-time crystallization is 16-72h.

5. The production method according to claim 1, wherein The raw material of the structure directing agent comprises a second silicon source, a third aluminum source, an alkali source and water, and in terms of SiO2, Al2O3, Na2O and H2O, the molar ratio of the second silicon source, the third aluminum source, the alkali source and water is (10-30):1:(10-30):(260-480).

6. The production method according to claim 1 or 5, wherein The first silicon source comprises one or a combination of more than two of tetraethyl orthosilicate, silica sol, silicon powder, silicic acid, white carbon black and water glass; The second silicon source comprises one or a combination of more than two of tetraethyl orthosilicate, silica sol, silicon powder, silicic acid, white carbon black and water glass.

7. The production method according to claim 1 or 5, wherein The first aluminum source comprises one or a combination of more than two of high-alkali sodium aluminate, low-alkali sodium aluminate, sodium aluminate, aluminum oxide, aluminum sulfate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide and aluminum nitrate; The second aluminum source comprises one or a combination of more than two of high-alkali sodium aluminate, low-alkali sodium aluminate, sodium aluminate, aluminum oxide, aluminum sulfate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide and aluminum nitrate; The third aluminum source comprises one or a combination of more than two of high-alkali sodium aluminate, low-alkali sodium aluminate, sodium aluminate, aluminum oxide, aluminum sulfate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide and aluminum nitrate.

8. The production method according to claim 5, wherein The alkali source comprises Na2O and / or NaOH.

9. A mesoporous NaY molecular sieve, which is obtained by the preparation method in any one of claims 1-8.

10. The mesoporous NaY molecular sieve of claim 9, wherein, The mesoporous NaY molecular sieve has a mesopore specific surface area of 60-130 m 2 ·g -1 The mesoporous NaY molecular sieve has a mesopore specific surface area of 60-130 m 3 ·g -1 .

Images