Ultra-stable mesoporous USY molecular sieve, preparation method thereof and catalytic cracking catalyst

Abstract

The invention provides an ultra-stable mesoporous USY molecular sieve, a preparation method thereof and a catalytic cracking catalyst. 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 a mesoporous NaY molecular sieve; soluble ammonium salt, the mesoporous NaY molecular sieve and deionized water are mixed to obtain a mixed solution, and the mixed solution is subjected to ammonium ion exchange; carrying out hydrothermal ultra-stabilization on the mesoporous NaY molecular sieve subjected to primary exchange; and repeating the ammonium ion exchange and hydrothermal ultra-stable process to obtain the ultra-stable mesoporous USY molecular sieve. The self-made mesoporous NaY molecular sieve is subjected to hydrothermal ultra-stable modification, so that the mesoporous content of the self-made mesoporous NaY molecular sieve can be further improved, and the ultra-stable mesoporous USY molecular sieve is obtained and is used for a catalytic cracking catalyst.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve synthesis technology, specifically relating to an ultrastable mesoporous USY molecular sieve, its preparation method, and a catalytic cracking catalyst. Background Technology

[0002] The single microporous structure of NaY molecular sieves restricts catalytic conversion reactions involving macromolecules, hinders the diffusion of heavy oil macromolecules within the pores, and results in poor accessibility of its acidic active centers. To improve the cracking ability of NaY molecular sieves for heavy oil and other macromolecules, it is necessary to introduce mesoporous structures into NaY molecular sieves to increase the diffusion rate of heavy oil macromolecules within the pores and improve the accessibility of its acidic active centers. Furthermore, currently, ammonium ion exchange and hydrothermal ultrastable methods are commonly used in industry to prepare ultrastable (USY) molecular sieves. However, the pore volume and surface area of ​​these mesopores remain relatively low; therefore, increasing the mesopore content of USY molecular sieves has significant application value.

[0003] CN110627089A introduces Zr into the NaY molecular sieve framework. 4+ This method can directly generate intracrystalline mesoporous structures without the use of organic templates. It is the first method to introduce mesopores into the NaY molecular sieve framework using inorganic salts. However, the amount of mesopores introduced is low, and further hydrothermal aging treatment is required to prepare USY to increase the mesopore content. Secondly, Zr salts are expensive and not suitable for practical industrial applications.

[0004] CN108238613B synthesizes conventional NaY molecular sieves by introducing heteroatoms, and then prepares USY molecular sieves with small mesopores by removing unstable sites through hydrothermal ultrastability. However, the USY molecular sieves prepared by this method still have a low mesopore content.

[0005] Therefore, although the above work is of great significance for the synthesis of mesoporous NaY molecular sieves and USY molecular sieves, how to further improve the mesoporous content of USY molecular sieves is still an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide an ultrastable mesoporous USY molecular sieve, its preparation method, and a catalytic cracking catalyst. By controlling the timing of the addition of alkaline earth metal compounds through stepwise crystallization, a NaY molecular sieve with an intracrystalline mesoporous structure is prepared. Further hydrothermal ultrastable modification yields a USY molecular sieve with an even higher mesoporous content, which is then applied to a catalytic cracking catalyst.

[0007] To achieve the above objectives, the present invention provides a method for preparing an ultrastable mesoporous USY molecular sieve, wherein the preparation method includes the following steps:

[0008] (1) A first silicon source, a first aluminum source, a structure directing agent and an alkaline earth metal compound are mixed and crystallized once to obtain a precursor solution;

[0009] (2) Add a second aluminum source to the precursor solution, stir and mix to obtain a metal aluminosilicate gel, and then perform secondary crystallization on the metal aluminosilicate gel to obtain a mesoporous NaY molecular sieve.

[0010] (3) Mix soluble ammonium salt, mesoporous NaY molecular sieve, and deionized water in a mass ratio of (0.4-1):1:(6-12) to obtain a mixed solution; perform ammonium ion exchange on the mixed solution and adjust the pH to 3.0-4.5; then perform vacuum filtration, washing, and drying to complete one exchange (this process is called "one exchange").

[0011] (4) The mesoporous NaY molecular sieve that has undergone one exchange is subjected to hydrothermal ultrastabilization to complete one ultrastabilization (this process is called "one ultrastabilization").

[0012] (5) Repeat the above ammonium ion exchange and hydrothermal ultrastability process to complete the secondary exchange and secondary ultrastability (i.e., two-stage exchange and two-stage ultrastability) to obtain ultrastable mesoporous USY molecular sieve. The alkaline earth metal compound has a defect structure promoting effect.

[0013] According to a specific embodiment of the present invention, preferably, the molar ratio of silicon, aluminum, sodium and water in the metal aluminosilicate gel, based on SiO2, Al2O3, Na2O and H2O, is (5-20):1:(2-20):(150-300).

[0014] According to a specific embodiment of the present invention, preferably, the molar ratio of the content of the alkaline earth metal compound to the silicon element in the metal aluminosilicate gel, M / SiO2, is 0.105-0.2, where M represents the oxide corresponding to the alkaline earth metal.

[0015] According to a specific embodiment of the present invention, preferably, the mass of Al in the structure directing agent, calculated as Al2O3, accounts for 3%-12% of the mass of Al in the metal aluminosilicate gel.

[0016] According to a specific embodiment of the present invention, preferably, the alkaline earth metal compound includes one or more combinations of metal salts and metal hydroxides containing Be, Mg, Ca, Sr, and 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.

[0017] According to a specific embodiment of the present invention, preferably, the temperature of the first crystallization is 60-80°C and the time of the first crystallization is 1-28h.

[0018] According to a specific embodiment of the present invention, preferably, the secondary crystallization temperature is 90-180℃, and the secondary crystallization time is 16-72 hours. More preferably, the secondary crystallization temperature is 90-100℃.

[0019] The inventors of this invention have discovered that stepwise crystallization enables the sequential growth and detachment of alkaline earth metals within the molecular sieve framework, thereby achieving in-situ introduction of mesoporous structures within the crystal. The mechanism of this process is as follows: In the first crystallization step, the lower temperature is unfavorable for Al ions to enter the molecular sieve framework, and the introduction of a separate aluminum source reduces the alkalinity 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 higher temperature favors the entry of aluminum ions into the molecular sieve framework, and the subsequent addition of a strongly alkaline aluminum source increases the alkalinity of the system, making the MO bonds in the molecular sieve framework unstable and causing alkaline earth metal ions to detach from the framework. This results in structural defects in the crystal, promoting the formation of numerous mesopores. Therefore, this invention utilizes the in-situ introduction of alkaline earth metal ions at a lower crystallization temperature and their detachment from the framework at a higher crystallization temperature during the stepwise crystallization process of NaY molecular sieves to generate mesopores.

[0020] According to a specific embodiment of the present invention, preferably, the raw materials of the structure-directing agent include 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):(260-410) based on SiO2, Al2O3, Na2O and H2O.

[0021] 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.

[0022] 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.

[0023] 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℃.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] In some specific embodiments, preferably, the temperature of the ammonium ion exchange is 80-95°C and the time of the ammonium ion exchange is 30-90 min.

[0028] In some specific implementations, preferably, the hydrothermal ultrastability process is carried out in steam at 500-680°C for 1-6 hours.

[0029] In some specific embodiments, preferably, the soluble ammonium salt includes one or more combinations of ammonium chloride, ammonium sulfate, ammonium nitrate, etc.

[0030] In some specific embodiments, preferably, the acid used to adjust the pH is one or a combination of two or more of hydrochloric acid, nitric acid, sulfuric acid, etc.; the concentration of the acid can be controlled to be 0.5-2 mol / L.

[0031] In some specific implementations, preferably, during the hydrothermal ultrastability process, the heating rate of the hydrothermal device is 10-15℃ / min, and the water flux is 8-12 rpm.

[0032] The present invention also provides a mesoporous USY molecular sieve, which is prepared by the above-described method for preparing ultrastable mesoporous USY molecular sieve.

[0033] According to a specific embodiment of the present invention, preferably, the mesoporous USY molecular sieve has a mesoporous specific surface area of ​​90-150 m². 2 ·g -1 (Preferred 114-127m) 2 ·g -1 The mesopore volume is 0.05-0.30 cm³. 3 ·g -1 (Preferred size: 0.16-0.18cm) 3 ·g -1 ).

[0034] The present invention also provides a catalytic cracking catalyst, which is prepared using the above-mentioned ultrastable mesoporous USY molecular sieve as the active component; the amount of ultrastable mesoporous USY molecular sieve added is 10%-60%.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The method for preparing NaY molecular sieve with intracrystalline mesopores provided by the present invention does not require any organic template agent or post-processing steps. By controlling the timing of sequential introduction and removal of alkaline earth metal ions through stepwise crystallization, mesopores are generated in situ in the molecular sieve framework.

[0037] (2) The mesoporous NaY molecular sieve provided by the present invention can be hydrothermally stabilized to obtain an ultra-stable mesoporous USY molecular sieve, which has a higher mesopore content than conventional USY molecular sieve.

[0038] (3) The acid content of the ultra-stable mesoporous USY molecular sieve provided by the present invention is higher than that of conventional USY molecular sieve. Attached Figure Description

[0039] Figure 1 The XRD patterns of the USY molecular sieves prepared in Comparative Example 1, Example 1, Example 2, and Example 3 are shown.

[0040] Figure 2 Nitrogen adsorption-desorption isotherms for USY molecular sieves prepared in Comparative Example 1 and Example 4.

[0041] Figure 3 The pore size distribution of the USY molecular sieves prepared in Comparative Example 1 and Example 4 is shown.

[0042] Figure 4 The NH3-TPD diagrams are for the USY molecular sieves prepared in Comparative Example 1 and Example 4. Detailed Implementation

[0043] 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.

[0044] 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.

[0045] The molecular sieves provided in the examples and comparative examples were tested using the following analytical instruments:

[0046] 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.

[0047] 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.

[0048] 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.

[0049] The preparation process of the NaY molecular sieve structure directing agent used in the examples and comparative examples is as follows:

[0050] 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.

[0051] 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%).

[0052] 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).

[0053] 2. 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 until uniform, and age at 50℃ for 12h to obtain white gel-like NaY molecular sieve structure directing agent (2).

[0054] 3. 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 until uniform, and age at 35℃ for 20h to obtain white gel-like NaY molecular sieve structure directing agent (3).

[0055] Example 1

[0056] This embodiment provides a method for preparing ultrastable mesoporous USY molecular sieves, the specific steps of which are as follows:

[0057] (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 molar ratio of beryllium sulfate tetrahydrate to silicon dioxide is 0.105), the above aluminum sulfate solution, and 15.27g of directing agent (1) to water glass. After stirring evenly at 25°C, crystallize at 60°C for 20h to obtain a precursor solution.

[0058] (2) 5.89 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 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.

[0059] (3) Mix the above mesoporous Be-NaY molecular sieve, ammonium sulfate and deionized water in a mass ratio of 1:1:12. Exchange the mixed solution at 90℃ for 40 min. Adjust the pH to 3.5-4.0 with 1 mol / L H2SO4 solution. Then filter, wash and dry to obtain mesoporous NH4Y molecular sieve.

[0060] (4) The above mesoporous NH4Y molecular sieve was hydrothermally calcined in steam at 650°C for 2 hours.

[0061] (5) Repeat the above ammonium ion exchange and hydrothermal calcination processes once each to obtain ultra-stable mesoporous USY molecular sieve.

[0062] Example 2

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

[0064] (1) Add 26.65g of aluminum sulfate octahydrate to 122.68g of deionized water to prepare a solution. Add the above aluminum sulfate solution and 20.03g of strontium chloride hexahydrate to 70.31g of silica sol and stir evenly (the molar ratio of strontium chloride hexahydrate to silica is 0.15). Add 16.21g of directing agent. (2) Mix at 25°C and crystallize at 60°C for 18h to obtain the precursor solution.

[0065] (2) 16.73 g of sodium aluminate was added to the above precursor solution and stirred at 25 °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=3.5:1:12:300. The gel was crystallized at 90 °C for 24 h. The product was washed, filtered and dried to obtain mesoporous Sr-NaY molecular sieve.

[0066] (3) The above mesoporous Sr-NaY molecular sieve, ammonium sulfate and deionized water are mixed in a mass ratio of 0.4:1:6. The mixed solution is exchanged at 90℃ for 30 min. The pH is adjusted to 3.5-4.0 with 1 mol / L H2SO4 solution. Then the mixture is filtered, washed and dried to obtain mesoporous NH4Y molecular sieve.

[0067] (4) The above mesoporous NH4Y molecular sieve was hydrothermally calcined in steam at 650°C for 2 hours.

[0068] (5) Repeat the above ammonium ion exchange and hydrothermal calcination processes once each to obtain ultra-stable mesoporous USY molecular sieve.

[0069] Example 3

[0070] This embodiment provides a method for preparing ultrastable mesoporous USY molecular sieves, the specific steps of which are as follows:

[0071] (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 13.63g of sodium hydroxide solution to obtain an alkaline sodium silicate solution. Add 5.05g of calcium chloride (molar ratio of calcium chloride to silicon dioxide is 0.18), 6.88g of directing agent (3), and the above aluminum nitrate solution to the alkaline sodium silicate solution. Mix at 40°C, dissolve, and crystallize at 80°C for 18h to obtain a precursor solution.

[0072] (2) 11.38 g of low-alkali sodium aluminate was added to the above precursor solution and stirred at 60 °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 100 °C for 48 h. The product was washed, filtered and dried to obtain mesoporous Ca-NaY molecular sieve.

[0073] (3) Mix the above mesoporous Ca-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. Adjust the pH to 3.0-3.2 with 1 mol / L H2SO4 solution. Then filter, wash and dry to obtain mesoporous NH4Y molecular sieve.

[0074] (4) The above mesoporous NH4Y molecular sieve was hydrothermally calcined in steam at 650°C for 2 hours.

[0075] (5) Repeat the above ammonium ion exchange and hydrothermal calcination processes once each to obtain ultra-stable mesoporous USY molecular sieve.

[0076] Example 4

[0077] This embodiment provides a method for preparing ultrastable mesoporous USY molecular sieves, the specific steps of which are as follows:

[0078] (1) Add 132g of aluminum sulfate solution, 5.07g of magnesium hydroxide (the molar ratio of magnesium hydroxide to silicon dioxide is 0.13) and 27.51g of directing agent to 185.97g of water glass. After stirring evenly at 45℃, crystallize at 70℃ for 12h to obtain the precursor solution.

[0079] (2) 29.28g of high-alkali sodium aluminate was added to the above precursor solution and stirred at 70℃ until the system was homogeneous to obtain metal aluminosilicate gel. The molar ratio of each component in the gel was Na2O:Al2O3:SiO2:H2O=2.7:1:9.5:230. The gel was crystallized at 110℃ for 24h. The obtained product was washed, filtered and dried to obtain mesoporous Mg-NaY molecular sieve.

[0080] (3) Mix the above mesoporous Mg-NaY molecular sieve, ammonium chloride and deionized water in a mass ratio of 0.4:1:8. Exchange the mixed solution at 90℃ for 60 min. Adjust the pH to 4.0-4.5 with 1 mol / L HCl solution. Then filter, wash and dry to obtain mesoporous NH4Y molecular sieve.

[0081] (4) The above mesoporous NH4Y molecular sieve was hydrothermally calcined in steam at 650°C for 2 hours.

[0082] (5) Repeat the above ammonium ion exchange and hydrothermal calcination processes once each to obtain ultra-stable mesoporous USY molecular sieve.

[0083] Comparative Example 1

[0084] This comparative example provides a conventional method for using USY molecular sieves, with the following specific steps:

[0085] (1) 61.95g of aluminum sulfate solution was slowly added dropwise to 139.07g of water glass and stirred 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.

[0086] (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. Adjust the pH to 3.5-4.0 with 1 mol / L HCl solution. Then filter, wash and dry to obtain NH4Y molecular sieve.

[0087] (3) The above NH4Y molecular sieve was hydrothermally calcined in 100% steam at 650℃ for 2 hours.

[0088] (4) Repeat the above ammonium ion exchange and hydrothermal calcination processes once each to obtain conventional USY molecular sieve.

[0089] Comparative Example 2

[0090] 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:

[0091] (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 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.

[0092] (2) The above mesoporous Be-NaY molecular sieve, ammonium sulfate and deionized water are mixed in a mass ratio of 1:1:12. The mixed solution is exchanged at 90℃ for 40 min. The pH is adjusted to 3.5-4.0 with 1 mol / L H2SO4 solution. Then the mixture is filtered, washed and dried to obtain mesoporous NH4Y molecular sieve.

[0093] (3) The above mesoporous NH4Y molecular sieve was hydrothermally calcined in steam at 650°C for 2 hours.

[0094] (4) Repeat the above ammonium ion exchange and hydrothermal calcination processes once each to obtain conventional USY molecular sieve.

[0095] Test Example 1

[0096] This test example will prepare catalysts using the conventional USY molecular sieve prepared in Comparative Example 1 and the ultrastable mesoporous USY molecular sieve prepared in Example 4, and evaluate their ACE. The specific process is as follows:

[0097] (1) FCC catalyst preparation: A mixture of 35% molecular sieve, 15% alumina sol, 50% kaolin (dry basis) and a certain amount of deionized water was prepared by spray molding of conventional USY molecular sieve and mesoporous USY molecular sieve. The molded microspheres were then aged at 800℃ with 100% steam for 4 hours.

[0098] (2) The Dalian industrial catalytic cracking feedstock VGO was evaluated using the ACE fixed fluidized bed catalytic cracking evaluation device designed and manufactured by KTI Technology Company in the United States. The feedstock feed rate was 1.5 g / min, the feed amount was 1.5 g, the agent-to-oil mass ratio was 6.0, the reaction temperature was 530℃, and the reaction was completed in 75 s. The overall product composition was analyzed by Agilent 6890 chromatography.

[0099] The ACE evaluation results of the catalysts showed that the gasoline conversion rate of the catalyst prepared using the sample of Comparative Example 1 was 53%, while the gasoline conversion rate of the catalyst prepared using the sample of Example 4 was 60%, an increase of 7 percentage points.

[0100] The pore structure parameters of the mesoporous molecular sieves prepared in Examples 1-4 and Comparative Examples 1-2 are compared with those of conventional molecular sieves. The results are shown in Table 1.

[0101] Table 1. Pore structure parameters of samples from Examples 1-4 and Comparative Examples 1-2

[0102]

[0103]

[0104] According to the data in Table 1, the mesoporous specific surface area of ​​the USY molecular sieve provided in Example 4 is 114.9 m². 2 ·g -1 The mesopore volume is 0.16 cm³. 3 ·g -1 The mesoporous pore volume of conventional USY molecular sieves (Comparative Examples 1-2) is 0.10-0.11 cm³. 3 / g, the mesopore volume of the USY molecular sieve provided in Example 4 is approximately 1.5 times that of conventional USY molecular sieves. Furthermore, as shown in Table 1, the relative crystallinity of the molecular sieves obtained in Examples 1, 2, and 3 is not significantly different from that in Comparative Example 1, maintaining a generally high level, indicating that the introduction of alkaline earth metals does not have an additional impact on the crystallinity of the mesoporous USY molecular sieve. Further, compared to Example 1 (stepwise crystallization), Comparative Example 2 (one-step crystallization) yields a molecular sieve with lower mesopore surface area and pore volume. This demonstrates the importance of stepwise crystallization for introducing alkaline earth metals and improving mesopores, indicating that the stepwise crystallization method proposed in this invention can increase the mesopore content of the molecular sieve.

[0105] Figure 1 These are the XRD patterns of Comparative Example 1 and Examples 1, 2, and 3. From... Figure 1 It can be seen that, compared with Comparative Example 1, the USY molecular sieves provided in Examples 1, 2 and 3 are typical Y-type molecular sieves.

[0106] Figure 2 The N2 adsorption-desorption isotherms for Comparative Example 1 and Example 4 are as follows: Figure 2The N2 adsorption-desorption isotherms show that the adsorption-desorption isotherms of the USY molecular sieves provided in Comparative Example 1 and Example 4 are Type IV curves with H3-type hysteresis loops. Example 4 has a more obvious hysteresis loop than Comparative Example 1, indicating that the USY molecular sieve prepared in Example 4 has more abundant mesopores.

[0107] Figure 3 This is a pore size distribution diagram for Comparative Example 1 and Example 4, by... Figure 3 As can be seen from the pore size distribution curve, the USY molecular sieve provided in Example 4 has a more concentrated mesopore distribution in the 2-10 nm range.

[0108] Figure 4 The NH3-TPD curves for Comparative Example 1 and Example 4 are shown below. Figure 4 It can be observed that the amount of weak acid in Example 4 is significantly increased compared to Comparative Example 1, while the amount of medium-strong acid is slightly increased.

Claims

1. A method for preparing an ultra-stable mesoporous (USY) 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, stirring and mixing, and then a metal silicoaluminate gel is obtained; the metal silicoaluminate gel is subjected to two-time crystallization, and a mesoporous NaY molecular sieve is obtained; (3) mixing soluble ammonium salt, mesoporous NaY molecular sieve and deionized water in a mass ratio of (0.4-1):1:(6-12) to obtain a mixed solution; the mixed solution is subjected to ammonium ion exchange, and the pH is adjusted to 3.0-4.5; then, the mixed solution is subjected to suction filtration, washing and drying, and one-time exchange is completed; (4) the mesoporous NaY molecular sieve subjected to one-time exchange is subjected to hydrothermal ultrastabilization, and one-time ultrastabilization is completed; (5) repeating the above ammonium ion exchange and hydrothermal ultrastabilization processes, and two-time exchange and two-time ultrastabilization are completed, and an ultrastable mesoporous USY molecular sieve is obtained; in terms of SiO2, Al2O3, Na2O and H2O, the molar ratio of silicon, aluminum, sodium 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 to SiO2 in the metal silicoaluminate gel M / SiO2=0.105-0.2, 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 includes 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 DEG 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 DEG 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 includes 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):(260-410) in terms of SiO2, Al2O3, Na2O and H2O.

6. The production method according to claim 1 or 5, wherein The first silicon source includes 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 includes 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 includes one or a combination of more than two of high-alkali sodium metaaluminate, low-alkali sodium metaaluminate, sodium metaaluminate, aluminum oxide, aluminum sulfate, aluminum isopropylate, pseudo-boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide and aluminum nitrate; The second aluminum source includes one or a combination of more than two of high-alkali sodium metaaluminate, low-alkali sodium metaaluminate, sodium metaaluminate, aluminum oxide, aluminum sulfate, aluminum isopropylate, pseudo-boehmite, aluminum chloride, aluminum citrate, aluminum hydroxide and aluminum nitrate; The third aluminum source includes one or a combination of two or more of high-alkali sodium metaaluminate, low-alkali sodium metaaluminate, sodium metaaluminate, 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 includes Na2O and / or NaOH.

9. An ultra-stable mesoporous USY molecular sieve obtained from the preparation process of any one of claims 1-8; the mesoporous USY molecular sieve having a mesopore specific surface area of 90-150 m2 / g and a mesopore volume of 0.05-0.30 cm3 / g. 2 ·g -1 3 ·g -1 .​ 10. A catalytic cracking catalyst prepared by using the ultrastable mesoporous USY molecular sieve of claim 9 as an active component. The addition amount of the ultrastable mesoporous USY molecular sieve is 10% to 60%.

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