(NH4) 2SiF6 dealumination and silicon supplement modification method of mesoporous NaY molecular sieve and hydrocracking catalyst

Abstract

The invention discloses a (NH4) 2SiF6 dealumination and silicon supplement modification method of a mesoporous NaY molecular sieve and a hydrocracking catalyst.The modification method comprises the steps that a first silicon source, a first aluminum source, an alkali source and water are mixed and then aged, and a NaY molecular sieve structure directing agent is obtained; mixing a second silicon source, a second aluminum source, a NaY molecular sieve structure directing agent and a precursor of metal M with a defect structure promoting effect to obtain a precursor solution, and performing primary crystallization on the precursor solution; adding a third aluminum source into the precursor solution after the first crystallization, and carrying out second crystallization to obtain a mesoporous NaY molecular sieve; carrying out ammonium exchange on the mesoporous NaY molecular sieve to obtain an NH4Y molecular sieve; the method comprises the following steps: mixing an NH4Y molecular sieve, an H4Ac buffer solution and a (NH4) 2SiF6 solution, heating and refluxing, and then carrying out suction filtration and washing to obtain the SY molecular sieve. The molecular sieve obtained by the method has a large number of mesopores and a relatively high silica-alumina ratio.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrocracking catalysts, and particularly relates to a (NH4)2SiF6 dealumination and silicon supplementation modification method of mesoporous NaY molecular sieves and a hydrocracking catalyst. BACKGROUND

[0002] The heavy and poor quality of hydrocracking raw materials such as vacuum residue and the like put forward more stringent requirements on the pore structure and acid properties of molecular sieves. Although the conventional Y molecular sieves have more acid sites, the structure mainly composed of micropores limits the diffusion of large molecules, which is not conducive to the contact between reactant molecules and active sites. It is necessary to introduce mesoporous structure into NaY molecular sieves to improve the diffusion rate of heavy oil macromolecules in the pores and improve the accessibility of the acid active centers. In addition, the acid is mainly weak acid, and the distribution of medium-strong acid suitable for hydrocracking reaction is less. In order to solve the above problems, ammonium ion exchange and steam treatment or complexing agent dealumination are generally used in industry to improve the silicon-aluminum ratio of NaY molecular sieves. However, the NaY molecular sieves obtained by these methods contain a large amount of non-framework aluminum and hydroxyl cavities, which affects the performance of the molecular sieves.

[0003] Dealumination and silicon supplementation treatment of molecular sieves with (NH4)2SiF6 under suitable conditions can prepare high-silicon Y-type molecular sieves. This is because (NH4)2SiF6 will gradually hydrolyze in aqueous solution to generate hydronium ions, free fluorides and monomeric silicon species. The monomeric silicon can react with the vacancies after the dealumination of the framework in the aqueous solution to realize the isomorphous substitution of the molecular sieves. The application of (NH4)2SiF6 for dealumination and silicon supplementation modification of molecular sieves obtains high-silicon Y molecular sieves with high crystallinity and few non-framework aluminum and hydroxyl cavities. In addition, because of the good dealumination and silicon supplementation effect, the number of medium-strong acid of the modified Y molecular sieves is greatly improved, which has important industrial application value.

[0004] Patent CN109665539A proposes a method for preparing modified Y molecular sieves. A directing agent is prepared by a special treatment method, and then a mixture composed of the directing agent, water, a silicon source and an aluminum source is subjected to hydrothermal crystallization to obtain a crystallization product containing small-grained NaY. Finally, the small-grained NaY is assembled through the action of a silane coupling agent and a surfactant to obtain NaY molecular sieves with regular mesoporous-microporous structure. The modified Y molecular sieves are obtained through post-treatment modification of sodium reduction by ammonium exchange, hydrothermal treatment and dealumination and silicon supplementation. The preparation process of this method is simple and easy to operate, and the connectivity of the mesopores and micropores can be easily optimized, which is conducive to the diffusion of macromolecules and maintains the characteristics of Y molecular sieves micropores and improves the crystallinity retention. The defect of this technology is that the obtained gas phase ultrastable molecular sieves have few mesopores in the framework.

[0005] Patent CN105084386A adopts hydrothermal treatment and de-aluminum and silicon supplementing combined process, so that the silicon content on the surface of Y molecular sieve is obviously increased, the lattice vacancy generated by removing silicon and aluminum during hydrothermal aging is filled, and the overall skeleton silicon aluminum ratio is only slightly increased. Finally, the Y molecular sieve cell only has a slight contraction, the relative crystallinity is 100%-130%, the cell parameter is 2.460-2.468nm, and the sodium oxide content is ≤0.1wt%. SUMMARY

[0006] The purpose of the present application is to provide a (NH4)2SiF6 de-aluminum and silicon supplementing modification method of mesoporous NaY molecular sieve, and the molecular sieve obtained by the method has a large amount of mesopores and a high silicon aluminum ratio.

[0007] The purpose of the present application is also to provide a catalytic cracking catalyst.

[0008] To achieve the above purpose, the present application provides a (NH4)2SiF6 de-aluminum and silicon supplementing modification method of mesoporous NaY molecular sieve, comprising the following steps:

[0009] S1, mixing a first silicon source, a first aluminum source, an alkali source and water to obtain a NaY molecular sieve structure directing agent after aging;

[0010] S2, mixing a second silicon source, a second aluminum source, the NaY molecular sieve structure directing agent and a precursor of a metal M having a defect structure promoting effect to obtain a precursor solution, and performing first crystallization on the precursor solution at 50-80℃ for 16-30h;

[0011] S3, adding a third aluminum source to the precursor solution after the first crystallization to obtain a metal silicon aluminate gel, and performing second crystallization on the obtained metal silicon aluminate gel at 90-110℃ for 16-84h to obtain a mesoporous NaY molecular sieve, wherein the metal M in the metal silicon aluminate gel is calculated as an oxide, the silicon element is calculated as SiO2, and the molar ratio of the oxide of the metal M to SiO2 is 0.01-0.06;

[0012] S4, mixing a soluble ammonium salt, the mesoporous NaY molecular sieve and deionized water to perform ammonium exchange, and then performing suction filtration, washing and drying to obtain an NH4Y molecular sieve;

[0013] S5, mixing the NH4Y molecular sieve, an H4Ac buffer solution and a (NH4)2SiF6 solution, heating and refluxing, and then performing suction filtration, washing and drying to obtain an SY molecular sieve.

[0014] The method for removing aluminum and adding silicon to mesoporous NaY molecular sieve (NH4)2SiF6 in this invention, in step S1, the first silicon source, the first aluminum source, the alkali source and water are calculated as SiO2, Al2O3, Na2O and H2O respectively, and the molar ratio is (12-30):1:(15-35):(250-480).

[0015] The method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieve (NH4)2SiF6 according to the present invention, wherein the molar ratio of SiO2, Al2O3, Na2O and H2O in the metal aluminosilicate gel is (10-20):1:(2-15):(150-300).

[0016] The method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieve (NH4)2SiF6 according to the present invention includes a first silicon source and a second silicon source that may be the same or different, and respectively include one or more of tetraethyl orthosilicate, silica sol, silica powder, silicic acid, silica, and water glass.

[0017] The method for dealumination and silicon replenishment modification of (NH4)2SiF6 in mesoporous NaY molecular sieves described in this invention includes a first aluminum source, a second aluminum source, and a third aluminum source that may be the same or different, and each of them includes one or more of the following: high-alkali sodium aluminate solution (high-alkali), low-alkali sodium aluminate solution (low-alkali), sodium aluminate, alumina, aluminum sulfate, aluminum isopropoxide, boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide, and aluminum nitrate.

[0018] The method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieve (NH4)2SiF6 according to the present invention, wherein the metal M is an alkaline earth metal, and the alkaline earth metal is one or more of Ca, Mg, Be, Ba and Sr.

[0019] The method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieves (NH4)2SiF6 according to the present invention includes the following steps: aging temperature in step S1 is 25-50℃, aging time is 1-32h; the precursor solution in step S2 is obtained by mixing at 25-60℃; metal aluminosilicate gel in step S3 is obtained by mixing at 25-80℃; the product obtained after secondary crystallization in step S3 is cooled, washed, filtered, and dried at 60-120℃ to obtain mesoporous NaY molecular sieves.

[0020] In the method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieve (NH4)2SiF6 described in this invention, the mass of Al2O3 in the NaY molecular sieve structure directing agent in step S3 accounts for 3-10% of the mass of Al2O3 in the metal aluminosilicate gel.

[0021] The method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieve (NH4)2SiF6 according to the present invention includes, in step S4, at least one of ammonium chloride, ammonium sulfate, and ammonium nitrate as the soluble ammonium salt.

[0022] The method for dealumination and silicon replenishment modification of (NH4)2SiF6 by mesoporous NaY molecular sieves according to the present invention, in step S4, the mass ratio of soluble ammonium salt, the mesoporous NaY molecular sieve, and deionized water is 0.6-1:1:5-15, and the ammonium exchange conditions are 30-90 min at a temperature of 75-95℃. Preferably, the ammonium exchange process is performed three or more times to ensure complete exchange.

[0023] The method for dealumination and silicon replenishment modification of mesoporous NaY molecular sieve (NH4)2SiF6 according to the present invention includes a stirring temperature of 25-90℃ in step S5 and a stirring time of 1-20h.

[0024] The method for dealumination and silicon replenishment modification of (NH4)2SiF6 by mesoporous NaY molecular sieves according to the present invention, wherein in step S5, SiF6 in the (NH4)2SiF6 solution... 2- The molar ratio of NH4Y molecular sieve to Al2O3 in mesoporous NaY molecular sieve is 0.1-1.0; the pH of H4Ac buffer solution is 5.8-6.5. Preferably, the NH4Y molecular sieve and H4Ac buffer solution are first mixed evenly, and then (NH4)2SiF6 solution is added, and the mixture is stirred at 25-90℃ for 1-20 hours.

[0025] To achieve the above objectives, the present invention also provides a hydrocracking catalyst, wherein the SY molecular sieve is obtained by a (NH4)2SiF6 dealumination and silicon replenishment modification method comprising the mesoporous NaY molecular sieve described above.

[0026] Beneficial effects of this invention:

[0027] The method described in this invention achieves the sequential growth and detachment of alkaline earth metals within the molecular sieve framework through stepwise crystallization, thereby realizing the in-situ introduction of mesoporous structures within the crystals. In the first crystallization step, the relatively low temperature is unfavorable for Al ions to enter the molecular sieve framework, and the introduction of a separate aluminum source reduces the basicity of the system. The combined effect of these two factors facilitates the entry of alkaline earth metal ions into the molecular sieve framework. In the second crystallization step, the high temperature favors the entry of aluminum ions into the molecular sieve framework, and the subsequent addition of a strongly alkaline aluminum source increases the basicity of the system. This destabilizes the MO bonds in the molecular sieve framework, causing alkaline earth metal ions to detach from the framework, resulting in structural defects in the crystals and promoting the formation of numerous mesopores. Attached Figure Description

[0028] Figure 1 The XRD patterns of the SY molecular sieves provided in Comparative Example 1 and Examples 1-5 are shown.

[0029] Figure 2ANitrogen adsorption-desorption of the SY molecular sieve provided in Comparative Example 1 and Example 1.

[0030] Figure 2B Pore ​​size distribution diagrams of the SY molecular sieves provided for Comparative Example 1 and Example 1. Detailed Implementation

[0031] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0032] In the examples, water glass, high-alkali, low-alkali, and aluminum sulfate were sourced 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.

[0033] The mesoporous NaY molecular sieves provided in the examples were tested using the following analytical instruments:

[0034] 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.

[0035] 2. Adsorption-desorption isotherms of the samples were determined at liquid nitrogen temperature using an ASAP2020M fully automated adsorption analyzer manufactured by Micromeritics, USA. Nitrogen gas was used as the adsorbate. The T-plot model was used to distinguish between the internal and external surface areas of the samples. The pore volume and pore size distribution were determined using the static volumetric method, thereby calculating the pore structure parameters. The specific implementation method is as follows.

[0036] The preparation process of the NaY molecular sieve structure directing agent used in the examples and comparative examples is as follows:

[0037] The silicon sources used in preparing the molecular sieves of the following structure-directing agents and examples and comparative examples are 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 are high-alkali sodium aluminate (with technical specifications of 21.13 wt% Na2O, 3.10 wt% Al2O3, and 75.77 wt% H2O) and low-alkali sodium aluminate (with technical specifications of 11.98 wt% Na2O, 8.07 wt% Al2O3, and 79.95 wt% H2O), and the purity of aluminum sulfate octadechydrate is 99 wt%. NaOH can also be used as the alkali source.

[0038] (1) 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 14h to obtain white gel-like NaY molecular sieve structure directing agent.

[0039] (2) 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 18h to obtain white gel-like NaY molecular sieve structure directing agent.

[0040] (3) 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, and age at 40℃ for 20h to obtain white gel-like NaY molecular sieve structure directing agent.

[0041] (4) 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 24h to obtain white gel-like NaY molecular sieve structure directing agent.

[0042] The following examples provide a method for preparing high-silica mesoporous SY molecular sieves:

[0043] Example 1

[0044] (1) Step 1: Dissolve 9.14g of aluminum sulfate octadecylhydrate in 16.87g of deionized water to obtain an aluminum sulfate solution. Place 46.68g of water glass in a water bath at 30℃. Add 1.12g of calcium chloride to the water glass. After mixing evenly, slowly add the above aluminum sulfate solution and stir vigorously. Then add 6.54g of directing agent (1). After stirring evenly, crystallize at 60℃ for 20h to obtain a precursor solution.

[0045] Step 2: Add 7.45g of high-alkali sodium aluminate to the above precursor solution to obtain a silicate gel with a molar ratio of Na2O:Al2O3:SiO2:H2O = 3:1:10:220, a molar ratio of calcium chloride to silicon dioxide of 0.06, and Al2O3 in the directing agent accounting for 5% of the total Al2O3 mass in the gel. After stirring until the system is homogeneous, crystallize at 100℃ for 24h. The obtained product is washed, filtered, and dried to obtain mesoporous Ca-NaY molecular sieve.

[0046] (2) Mix the above conventional NaY molecular sieve, ammonium chloride and deionized water in a mass ratio of 1:1:10, exchange the mixed solution at 90℃ for 60 min, then filter, wash and dry, repeat the operation more than three times to obtain NH4Y molecular sieve.

[0047] (3) Add the exchanged NH4Y molecular sieve to 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 60 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. 2- The molar ratio of (solution) / Al2O3 (molecular sieve) is 0.5. After the addition is complete, stirring and reflux are continued for 16 hours, followed by filtration and washing (until no NH4 is present in the solution). + (Ionization), drying, to obtain high-silica mesoporous SY molecular sieve.

[0048] Example 2

[0049] (1) Step 1: Dissolve 17.37g of aluminum sulfate octadecahydrate in 72.7g of deionized water to obtain an aluminum sulfate solution. Add 4.47g of beryllium sulfate tetrahydrate and the above aluminum sulfate solution to 142.70g of water glass and stir vigorously. After dissolving, add 15.07g of directing agent (4), stir evenly, and crystallize at 70℃ for 24h to obtain a precursor solution.

[0050] Step 2: Add 13.52g of low-alkali sodium aluminate to the above precursor solution to obtain a silicate gel with a molar ratio of Na2O:Al2O3:SiO2:H2O = 2.9:1:13:300, a molar ratio of beryllium sulfate tetrahydrate to silicon dioxide of 0.05, and Al2O3 in the directing agent accounting for 5% of the total Al2O3 mass in the gel. After stirring until the system is homogeneous, crystallize at 110℃ for 56h. The obtained product is washed, filtered, and dried to obtain mesoporous Be-NaY molecular sieve.

[0051] (2) The above mesoporous Be-NaY molecular sieve, ammonium sulfate and deionized water are mixed in a mass ratio of 1:0.6:9. The mixed solution is exchanged at 90℃ for 30 min, and then filtered, washed and dried to obtain mesoporous NH4Y molecular sieve.

[0052] (3) Add the exchanged NH4Y molecular sieve to 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 50 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. 2- The molar ratio of (solution) / Al2O3 (molecular sieve) is 0.4. After the addition is complete, stirring and reflux are continued for 14 hours, followed by filtration and washing (until no NH4 is present in the solution). + (Ionization), drying, to obtain high-silica mesoporous SY molecular sieve.

[0053] Example 3

[0054] (1) Step 1: Dissolve 21.32g of aluminum sulfate octadecylhydrate in 34.23g of deionized water to obtain an aluminum sulfate solution. Place 68.5g of silica sol in a 35℃ water bath, add 3.24g of basic magnesium carbonate and the above aluminum sulfate solution and stir vigorously. After dissolving, add 18.62g of directing agent (3), stir evenly, and crystallize at 50℃ for 16h to obtain a precursor solution.

[0055] Step 2: Add 44.81g of low-alkali sodium aluminate solution to the above precursor solution to obtain a silicate gel with a molar ratio of Na2O:Al2O3:SiO2:H2O = 2.7:1:15:200, a molar ratio of basic magnesium carbonate to silicon dioxide of 0.04, and Al2O3 in the directing agent accounting for 8% of the total Al2O3 mass in the gel. After stirring until the system is homogeneous, crystallize at 90℃ for 24h. The obtained product is washed, filtered, and dried to obtain mesoporous Mg-NaY molecular sieve.

[0056] (2) Mix the above mesoporous Mg-NaY molecular sieve, ammonium sulfate and deionized water in a mass ratio of 1:1:12, exchange the mixed solution at 90℃ for 60 min, and then filter, wash and dry to obtain mesoporous NH4Y molecular sieve.

[0057] (3) Add the exchanged NH4Y zeolite molecular sieve into 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 60 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. The molar ratio of SiF6 2- (solution) / Al2O3 (zeolite molecular sieve) is 0.7. After the addition, continue stirring and refluxing for 18 h, then filter by suction, wash (until there is no NH4 + ion in the solution), and dry to obtain high-silica mesoporous SY zeolite molecular sieve.

[0058] Example 4

[0059] (1) Step 1: Dissolve 19.55 g of aluminum nitrate in 136.33 g of deionized water to obtain an aluminum nitrate solution. Slowly add the aluminum nitrate solution and 2.67 g of strontium chloride hexahydrate to 142.8 g of water glass and stir vigorously, then add 14.67 g of the guiding agent (2). After stirring evenly, crystallize at 80 °C for 30 h to obtain a precursor solution;

[0060] Step 2: Add 18.46 g of high-alkali sodium aluminate to the above precursor solution to obtain a silicate gel. Its component molar ratio is Na2O:Al2O3:SiO2:H2O = 2.2:1:9.5:280. The molar ratio of strontium chloride hexahydrate to silicon dioxide is 0.02. The mass of Al2O3 in the guiding agent accounts for 3% of the total mass of Al2O3 in the gel. After stirring until the system is uniform, crystallize at 110 °C for 84 h. The obtained product is washed, filtered by suction, and dried to obtain mesoporous Sr-NaY zeolite molecular sieve;

[0061] (2) Mix the above mesoporous Sr-NaY zeolite molecular sieve, ammonium chloride, and deionized water in a mass ratio of 1:1:8. Exchange the mixed solution at 90 °C for 60 min, then filter, wash, and dry to obtain mesoporous NH4Y zeolite molecular sieve;

[0062] (3) Add the exchanged NH4Y zeolite molecular sieve into 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 90 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. The molar ratio of SiF6 2- (solution) / Al2O3 (zeolite molecular sieve) is 0.8. After the addition, continue stirring and refluxing for 18 h, then filter by suction, wash (until there is no NH4 + ion in the solution), and dry to obtain high-silica mesoporous SY zeolite molecular sieve.

[0063] Example 5

[0064] (1) Step 1: Mix 34.69g silica sol, 5.09g aluminum nitrate, 0.66g barium nitrate, 15.48g directing agent (2) and 42.53g deionized water at 55°C and crystallize at 80°C for 28h to obtain a precursor solution.

[0065] Step 2: Add 26.26g of high-alkali sodium aluminate to the above-mentioned solution and stir at 75℃ until the system is homogeneous to obtain a metal aluminosilicate gel. The molar ratio of each component in the gel is Na2O:Al2O3:SiO2:H2O = 3.0:1:12:240, the molar ratio of barium nitrate to silicon dioxide is 0.01, and the mass of Al2O3 in the directing agent accounts for 8% of the total Al2O3 mass in the gel. Crystallize at 110℃ for 54h, and the obtained product is washed, filtered, and dried at 100℃ to obtain mesoporous Ba-NaY molecular sieve.

[0066] (2) Mix the above mesoporous Ba-NaY molecular sieve, ammonium chloride and deionized water in a mass ratio of 1:1:10, exchange the mixed solution at 85℃ for 60 min, and then filter, wash and dry to obtain mesoporous NH4Y molecular sieve.

[0067] (3) Add the exchanged NH4Y molecular sieve to 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 90 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. 2- The molar ratio of (solution) / Al2O3 (molecular sieve) is 0.9. After the addition is complete, stirring and reflux are continued for 18 hours, followed by filtration and washing (until no NH4 is present in the solution). + (Ionization), drying, to obtain high-silica mesoporous SY molecular sieve.

[0068] Comparative Example 1

[0069] The material ratio and stepwise crystallization process of Comparative Example 1 are exactly the same as those of Example 1, except that no alkaline earth metals are added. The preparation steps are as follows:

[0070] (1) Step 1: Dissolve 9.14g of aluminum sulfate octadecylhydrate in 16.87g of deionized water to obtain an aluminum sulfate solution. Place 46.68g of water glass in a water bath at 30°C, mix evenly, slowly add the above aluminum sulfate solution and stir vigorously, then add 6.54g of directing agent (1), stir evenly, and crystallize at 60°C for 20h to obtain a precursor solution.

[0071] Step 2: Add 7.45g of high-alkali sodium aluminate to the above precursor solution to obtain a silicate gel with a molar ratio of Na2O:Al2O3:SiO2:H2O = 3:1:10:220. After stirring until the system is homogeneous, crystallize at 100℃ for 24h. The obtained product is washed, filtered, and dried to obtain NaY molecular sieve.

[0072] (2) Mix the above conventional NaY molecular sieve, ammonium chloride and deionized water in a mass ratio of 1:1:10, exchange the mixed solution at 90℃ for 60 min, then filter, wash and dry, repeat the operation more than three times to obtain NH4Y molecular sieve.

[0073] (3) Add the exchanged NH4Y molecular sieve to 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 60 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. 2- The molar ratio of (solution) / Al2O3 (molecular sieve) is 0.5. After the addition is complete, stirring and reflux are continued for 16 hours, followed by filtration and washing (until no NH4 is present in the solution). + (Ionization), drying, to obtain high-silica mesoporous SY molecular sieve.

[0074] Comparative Example 2

[0075] The final material ratio of Comparative Example 2 is exactly the same as that of Example 1, and alkaline earth metals are added during the process. The difference is that Comparative Example 2 uses one-step crystallization, and its preparation steps are as follows:

[0076] 9.14g of aluminum sulfate octadecylhydrate was dissolved in 16.87g of deionized water to obtain an aluminum sulfate solution. 46.68g of water glass was placed in a water bath at 30℃. 1.12g of calcium chloride was added to the water glass. After mixing evenly, the above aluminum sulfate solution was slowly added dropwise while stirring vigorously. 7.45g of high-alkali sodium aluminate was added to the above precursor solution. Then, 6.54g of directing agent (1) was added to obtain a silicate gel with a molar ratio of Na2O:Al2O3:SiO2:H2O = 3:1:10:220. The molar ratio of calcium chloride to silicon dioxide was 0.06. The mass of Al2O3 in the directing agent accounted for 5% of the total mass of Al2O3 in the gel. After stirring until the system was uniform, it was crystallized at 100℃ for 24h. The obtained product was washed, filtered, and dried to obtain a mesoporous Ca-NaY molecular sieve.

[0077] (2) Mix the above conventional NaY molecular sieve, ammonium chloride and deionized water in a mass ratio of 1:1:10, exchange the mixed solution at 90℃ for 60 min, then filter, wash and dry, repeat the operation more than three times to obtain NH4Y molecular sieve.

[0078] (3) Add the exchanged NH4Y molecular sieve to 100 mL of NH4Ac buffer solution with pH = 6, stir vigorously at 60 °C, and then slowly add 0.2 M (NH4)2SiF6 solution. 2- The molar ratio of (solution) / Al2O3 (molecular sieve) is 0.5. After the addition is complete, stirring and reflux are continued for 16 hours, followed by filtration and washing (until no NH4 is present in the solution). + (Ionization), drying, to obtain high-silica mesoporous SY molecular sieve.

[0079] The high-silica mesoporous SY molecular sieve prepared in the examples was compared with the conventional SY molecular sieve obtained in the comparative example, and their structural parameters are listed in Table 1.

[0080] Figure 1 The XRD patterns are those of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, Example 4, and Example 5; from Figure 1 As can be seen, similar to Comparative Example 1, the high-silica mesoporous SY molecular sieves provided in Examples 1, 2, and 3 are typical Y-type molecular sieves.

[0081] Further comparison revealed that Comparative Example 1 used the exact same material ratio and stepwise crystallization process as Example 1, the only difference being the absence of alkaline earth metals. Conversely, Comparative Example 2 had the same final material ratio as Example 1, but incorporated alkaline earth metals during the process; the difference was that Comparative Example 2 employed a one-step crystallization method. The BET characterization results for each sample are shown in Table 1. The modified molecular sieves obtained in Examples 1, 2, and 3 exhibited higher specific surface area and pore volume of mesopores than those in Comparative Examples 1 and 2. This indicates that introducing alkaline earth metals and stepwise crystallization during the synthesis of molecular sieves can induce mesopores and result in modified molecular sieves with a higher mesopore content.

[0082] Figure 2A These are the N2 adsorption-desorption isotherms for Comparative Example 1 and Example 1. Figure 2B The diagram shows the pore size distribution of Comparative Example 1 and Example 1; where, for example... Figure 2A The N2 adsorption-desorption isotherms show that the adsorption-desorption isotherms of the SY molecular sieves provided in Comparative Example 1 and Example 1 are Type IV curves with an H3-type hysteresis loop. Example 1 exhibits a more pronounced hysteresis loop than Comparative Example 1, indicating that Example 1 has a richer mesoporous structure. Figure 2B As shown in the pore size distribution curve, the SY molecular sieve provided in Example 1 exhibits a more concentrated mesopore distribution in the 2-10 nm range. Combined with the data in Table 1, the mesopore specific surface area of ​​the SY molecular sieve provided in Example 1 is 230.5 m². 2 ·g -1 The mesopore volume is 0.26 cm³. 3 ·g-1 In contrast, the mesopore volume of the conventional SY molecular sieve in Comparative Example 1 was 0.16 cm³. 3 / g, with a mesoporous specific surface area of ​​126.3m². 2 ·g -1 The mesopore volume of the high-silica mesoporous SY molecular sieve provided in Example 1 is approximately 1.6 times that of the conventional SY molecular sieve.

[0083] Table 1 Comparison of structural parameters of the examples and comparative samples.

[0084]

[0085] Experimental Example

[0086] Using Comparative Example 1, Comparative Example 2, USY molecular sieve (purchased from Lanzhou Petrochemical Catalyst Plant of China National Petroleum Corporation), and the high-silica mesoporous SY molecular sieve prepared in Examples 1, 2, 3, 4, and 5 as active components, catalysts were prepared to obtain catalyst D1, catalyst D2, catalyst 0, catalyst 1, catalyst 2, catalyst 3, catalyst 4, and catalyst 5, respectively. The hydrocracking performance of the six catalysts was evaluated and compared, and the results are listed in Table 2.

[0087] (1) Catalyst preparation process: 20wt% of SB powder from Sasol (Germany), 40wt% of pseudoboehmite powder, 30wt% of molecular sieve and 5wt% of guar gum powder were mixed evenly, and then the powdered solid mixture was mixed with 5wt% of a mixed solution of citric acid and nitric acid (each acid accounted for half), and extruded into strips by an extruder. The strips were dried in an oven at 120℃ for 4h, and then calcined in a muffle furnace at 550℃ for 4h to obtain a cylindrical catalyst support. A hydrocracking catalyst with an active component NiO-WO3 content of 25wt% (where the molar ratio of NiO to WO3 is 0.25) was prepared by saturated impregnation method. (2) Catalyst evaluation test was carried out on a 100ml fixed bed test device. The feed oil used was a mixture of wax oil and diesel oil (saturated hydrocarbon content 58.1%, aromatic hydrocarbon content 37.2%, gum content 4.7%). After pre-sulfurization treatment, the hydrocracking catalyst was evaluated for performance under the following process conditions: reaction temperature 380℃, hydrogen partial pressure 10.0 MPa, and volume hourly space velocity 1.5 h⁻¹. -1 The hydrogen-to-oil ratio is 800:1.

[0088] Compared to catalyst D1 obtained from the modified molecular sieve in Comparative Example 1, catalyst 1 prepared from the modified molecular sieve of Example 1 achieved a gasoline yield of 28.8% and a light oil yield of 68.4%, representing increases of 8.7 and 6.41 percentage points, respectively, compared to catalyst D1. Compared to the industrially available USY molecular sieve, the gasoline and light oil yields increased by 9.9 and 9.29 percentage points, respectively. This is attributed to two factors: firstly, the increased number of mesopores and enhanced pore connectivity facilitate the participation of more reactant molecules in the reaction; secondly, the increased content of moderately strong acids in the modified molecular sieve promotes the cracking of macromolecules in the feedstock. These excellent physicochemical properties are highly beneficial for the catalytic conversion of macromolecules such as heavy oil.

[0089] Table 2 Evaluation results of hydrocracking performance of each catalyst

[0090]

[0091]

[0092] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for modifying mesoporous NaY molecular sieve by (NH4)2SiF6 dealumination and silicon supplementation, characterized in that, The method comprises the following steps: S1, mixing a first silicon source, a first aluminum source, an alkali source and water, and then aging to obtain a NaY molecular sieve structure directing agent; S2, mixing a second silicon source, a second aluminum source, the NaY molecular sieve structure directing agent and a precursor of a metal M having a defect structure promoting effect to obtain a precursor solution, and then performing first crystallization on the precursor solution at 50-80 DEG C for 16-30 h; S3, adding a third aluminum source to the precursor solution after the first crystallization to obtain a metal silico-aluminate gel, and then performing second crystallization on the metal silico-aluminate gel at 90-110 DEG C for 16-84 h to obtain a mesoporous NaY molecular sieve, wherein the metal M in the metal silico-aluminate gel is in the form of an oxide, the silicon element is in the form of SiO2, and the molar ratio of the oxide of the metal M to SiO2 is 0.01-0.06; S4, mixing a soluble ammonium salt, the mesoporous NaY molecular sieve and deionized water to perform ammonium exchange, and then performing suction filtration, washing and drying to obtain an NH4Y molecular sieve; S5, mixing the NH4Y molecular sieve, an H4Ac buffer solution and an (NH4)2SiF6 solution, heating and refluxing, and then performing suction filtration and washing to obtain a SY molecular sieve.

2. The method for (NH4)2SiF6 dealumination and silication modification of the mesoporous NaY molecular sieve according to claim 1, characterized in that, In step S1, the first silicon source, the first aluminum source, the alkali source and water are in the form of SiO2, Al2O3, Na2O and H2O respectively, and the molar ratio is (12-30):1:(15-35):(250-480).

3. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieve according to claim 1, characterized in that, The molar ratio of SiO2, Al2O3, Na2O and H2O in the metal silico-aluminate gel is (10-20):1:(2-15):(150-300).

4. The method for (NH4)2SiF6 dealumination and silication modification of the mesoporous NaY molecular sieve according to claim 1, characterized in that, The first silicon source and the second silicon source are the same or different, and each comprises one or more of tetraethyl orthosilicate, silica sol, silicon powder, silicic acid, white carbon black and water glass.

5. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieve according to claim 1, characterized in that, The first aluminum source, the second aluminum source and the third aluminum source are the same or different, and each comprises one or more of high-alkali sodium metaborate solution, low-alkali sodium metaborate solution, sodium metaborate, aluminum oxide, aluminum sulfate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide and aluminum nitrate.

6. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieve according to claim 1, characterized in that, The metal M is an alkaline earth metal, and the alkaline earth metal is one or more of Ca, Mg, Be, Ba and Sr.

7. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieves according to claim 1, characterized in that, In step S1, the aging temperature is 25-50 DEG C, and the aging time is 1-32 h; in step S2, the precursor solution is mixed at 25-60 DEG C; in step S3, the metal silico-aluminate gel is mixed at 25-80 DEG C; and after the second crystallization in step S3, the product is cooled, washed, suction-filtered and dried at 60-120 DEG C to obtain the mesoporous NaY molecular sieve.

8. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieves according to claim 1, characterized in that, In step S3, the mass of Al2O3 in the NaY molecular sieve structure directing agent accounts for 3-10% of the mass of Al2O3 in the metal silico-aluminate gel.

9. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieve according to claim 1, characterized in that, In step S4, the soluble ammonium salt comprises at least one of ammonium chloride, ammonium sulfate and ammonium nitrate.

10. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieves according to claim 1, characterized in that, In step S4, the mass ratio of the soluble ammonium salt, the mesoporous NaY molecular sieve and deionized water is 0.6-1:1:5-15, and the ammonium exchange condition is that the exchange is performed at a temperature of 75-95 DEG C for 30-90 min.

11. The method for (NH4)2SiF6 dealumination and silication modification of mesoporous NaY molecular sieves according to claim 1, characterized in that, Step S5 SiF6 in (NH4)2SiF6 solution 2- The molar ratio of Al2O3 to mesoporous NaY molecular sieve is 0.1-1.0; the pH of H4Ac buffer solution is 5.8-6.

5.

12. A hydrocracking catalyst characterized in that, A (NH4)2SiF6 dealumination and silication modification method comprising the mesoporous NaY molecular sieve according to any one of claims 1-11 to obtain a SY molecular sieve.

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