A scandium-containing hierarchical porous silicoaluminophosphate molecular sieve and its preparation method

Abstract

The present invention provides a scandium-containing multi-level porous silica-alumina molecular sieve and a preparation method thereof. Due to the pore-forming effect of scandium, the interior of the crystal particles in the molecular sieve forms a well-structured multi-level porous crystal structure at the nanoscale. The molecular sieve has MFI, MOR, FAU and Beta* microporous structures, and the molecular sieve structure contains Lewis acidic sites and Bronsted acidic sites. The scandium-containing multi-level porous silica-alumina molecular sieve of the present invention uses silica sol as a silicon source, dissolves sodium metaaluminate under weak alkaline conditions, adds a template and Sc hydroxide, and assists with high-temperature water vapor. Through the structural guidance effect of the microporous template, the molecular sieve is ensured to have a highly ordered three-dimensional stacking structure while having micropores guided by the microporous template. The scandium-containing multi-level porous silica-alumina molecular sieve of the present invention is applied to the disproportionation reaction of MTO and toluene, and has good catalytic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve research, and in particular to a scandium-containing multi-level porous silicon-aluminum molecular sieve and a preparation method thereof. Background Art

[0002] Zeolites are inorganic crystalline materials with a regular pore structure composed of TO4 tetrahedra connected by common vertices. Zeolites have a unique pore distribution, large surface area, and tunable acidic sites, making them widely used in catalysis, adsorption, and ion exchange. However, the narrow pore structure and mesoscopic morphology of zeolites hinder heat and mass transfer during catalysis, severely inhibiting catalytic efficiency and service life. While mesoporous zeolites have larger pore sizes than microporous zeolites, facilitating the transport of reactants and products, their amorphous pore walls have poor hydrothermal stability, making them unsuitable for reactions requiring strong acidic sites, thus limiting their industrial application. Hierarchical pore sieves are inorganic porous materials with a large surface area, narrow pore size distribution, and a regular pore structure. They combine strong acidic sites, hydrothermal stability, and a mesoporous / macroporous structure with excellent shape selectivity and mass transfer capabilities. They are considered potential next-generation catalytic materials and are expected to play an important role in heavy oil cracking and macromolecular catalysis.

[0003] MFI topology molecular sieves have straight pores along the b axis and the sinusoidal channel along the a-axis It is widely used in catalytic cracking, toluene isomerization, and methanol to aromatics reactions. Related research has shown that due to the complexity of the catalytic reaction, it is of great significance to adjust the physicochemical properties of ZSM-5 (silica-alumina MFI zeolite), including the nature, location, strength / density of acid sites, metal / metal-to-metal pair acidity, porosity, crystal size, and crystallinity (Sharbini Kamaluddin H, Gong X, Ma P, Narasimharao K, Dutta Chowdhury A, Mokhtar M. Influence of zeolite ZSM-5 synthesis protocols and physicochemical properties in the methanol-to-olefin process. Materials Today Chemistry. 2022 / 12 / 01 / ;26:101061.).

[0004] Mordenite (MOR) is a microporous aluminosilicate with suitable acidity, a large specific surface area and pore volume, and excellent catalytic and thermal stability. The framework of MOR zeolite consists of straight channels (0.67 nm x 0.7 nm) of 12-membered rings (12MR) and straight channels (0.28 nm x 0.57 nm) of 8-membered rings (8MR) growing along the c-axis (with the crystal plane oriented in the

[001] direction), interconnected by a twisted 8-membered ring side pocket

[010] (0.34 nm x 0.48 nm) along the b-axis. Due to the relatively small pore size of the 8-membered rings in MOR zeolite, it is often considered a one-dimensional 12-membered ring zeolite. Due to its unique pore structure, MOR zeolite suffers from a serious diffusion limitation problem in catalytic reactions, as carbon deposits are often believed to accumulate in the 12-membered rings, thereby clogging the pores and causing catalyst deactivation. Therefore, regulating the pore structure of MOR zeolite is of great significance. (Xue H, Huang

[0005] Y-type zeolite is a silicate-aluminate zeolite with a microporous structure. It has a large specific surface area, strong acidity, and good shape selectivity, and plays a key role in the field of petroleum catalytic cracking. However, as crude oil becomes increasingly heavy, more and more macromolecules participate in the chemical reaction, and the microporous structure of the zeolite limits the adsorption of macromolecules to a certain extent. At the same time, the diffusion limitation of the micropores of the zeolite makes Y-type zeolite easily affected by carbon deposition and deactivation during the catalytic reaction, greatly shortening the service life of the catalyst. The synthesis of Y-type zeolite with a hierarchical pore structure has great research significance. (Liu, H., Fu, Y., Li, M., Wang, J., Noreen, A., & Maturura, E., et al. Activated carbon templated synthesis of hierarchical zeolite y-encapsulated ironcatalysts for enhanced gasoline selectivity in co hydrogenation. Journal of Materials Chemistry A.)

[0006] Beta molecular sieve is a molecular sieve formed by connecting tetragonal structure A and monoclinic structure B along the

[001] direction; along the

[100] and

[010] directions, a perpendicularly intersecting twelve-membered ring pore system is generated, with a pore size of approximately 0.66×0.77nm; along the

[001] direction, a Z-shaped (sinusoidal) curved pore system with a pore size of approximately 0.56×0.65nm is formed, which runs through the

[100] and

[010] directions. Therefore, Beta molecular sieve not only has a unique and unobstructed pore system, but also has adjustable acidity and good hydrothermal stability. Therefore, it is widely used in reactions such as alkylation, transalkylation, isomerization, and cracking. It occupies an important position in the fields of petrochemical industry and fine chemical synthesis. (Fan, Xiaojuan, et al. "Preparation, surfaceacidity and catalytic performance of Beta / ZSM-5composite molecular sieve." Chemical Physics 558(2022):111512-.)

[0007] In the catalytic process, due to the diffusion limitation from a single micropore and the long diffusion path in the zeolite, it is difficult to exert the inherent catalytic performance of the zeolite, especially when large reactants or products are involved. Therefore, in order to shorten the internal channels of the zeolite and thus accelerate the material transfer inside the MFI zeolite molecular sieve crystal, there are three common methods: (1) reducing the size of the zeolite crystal to shorten the intracrystalline diffusion path of the reactants; (2) introducing some mesopores and / or macropores into the zeolite crystal, that is, preparing zeolites with mesopore-micropore, macropore-micropore or macropore-mesopore-micropore structures, thereby shortening the internal channels of the zeolite and accelerating material transfer; (3) preparing two-dimensional, one-dimensional or zero-dimensional crystal structures to shorten the main path of material transfer inside the zeolite crystal. For MFI zeolite catalysts with nanocrystals, although the diffusion limitation problem has been well solved, the problem of low thermal stability still exists. In China, Shang Zhengyun et al. developed a new synthetic route using tetramethylguanidine (TMG) as an additive to directly synthesize zeolites with 85 nanometer thin plates, single crystals but hierarchical structures in the synthesis of ZSM-5 zeolite. Compared with traditional ZSM-5 zeolite, this zeolite has a longer catalytic life, higher selectivity for light olefins and better regeneration performance (Shang Z, Chen Y, Zhang L, Zhu X, Wang X, Shi C. Constructing single-crystalline hierarchical plate-like ZSM-5 zeolites with short b-axis length for catalyzing MTO reactions. Inorganic Chemistry Frontiers.).

[0008] CN108455626 B discloses a ZSM-5 multi-level pore molecular sieve with a bulk nanosheet composite structure. The method comprises adding a conventional microporous ZSM-5 block to an aging solution of a nanosheet ZSM-5 molecular sieve, and finally obtaining a lamellae ZSM-5 / bulk ZSM-5 composite molecular sieve through hydrothermal synthesis. The ZSM-5 multi-level pore molecular sieve with a bulk ZSM-5 / nanosheet composite structure prepared by the present invention has a catalyst service life increased by 490% and a main product (propylene) selectivity increased by 6.8% compared to commercial bulk ZSM-5 molecular sieves during the catalytic conversion of methanol to propylene. Compared to lamellae ZSM-5, the catalyst service life is increased by 39% and the main product (propylene) selectivity is increased by 6.6%.

[0009] CN113044852 A applied for a multi-level pore ZSM-5 molecular sieve and its preparation method and application. It uses hemicellulose as a hard template to prepare it. The synthesized molecular sieve has ordered micropores and mesopores at the same time, forming more pore structures of different sizes.

[0010] CN 115364893 B discloses a method for preparing a Beta-ZSM composite multi-level pore molecular sieve. The method utilizes vinyltriethoxysilane to induce silica sol and sodium aluminate to synthesize the Beta-ZSM composite multi-level pore molecular sieve in one step. The product has a spherical structure, a micropore specific surface area of 247.8428 m2 / g, and a mesopore specific surface area of 112.9934 m2 / g.

[0011] CN 111992244 A discloses a novel multi-level porous ZSM-5 molecular sieve catalyst for methanol to propylene and its preparation method, which breaks away from the limitations of traditional carbon templates. The mesopores of the multi-level porous molecular sieve are highly penetrating.

[0012] CN 106268928 A discloses a method for synthesizing an ordered macroporous-mesoporous-microporous multi-level pore molecular sieve catalyst formed by stacking Beta molecular sieve nanocrystals. The developed molecular sieve with an ordered macroporous-mesoporous-microporous multi-level pore structure has better catalytic activity, selective catalytic performance and higher structural stability than traditional molecular sieves, and has broad application prospects.

[0013] Aromatic hydrocarbons produced through catalytic reforming and cracking of petroleum fractions contain significant amounts of toluene. Among BTX (benzene, toluene, and xylenes), toluene is the most abundant source, accounting for 40-50% of the total aromatics. However, market demand for toluene is far less than that for benzene and xylenes, resulting in a relative surplus of toluene. Therefore, converting excess toluene generated during industrial production into other high-value-added aromatic products has been a key research topic in the petrochemical industry.

[0014] In order to obtain zeolites with multi-level pore structures, two main strategies are currently adopted, namely the so-called top-down and bottom-up approaches. The former is to remove some silicon or aluminum atoms in the zeolite framework by acid washing or alkali washing to create mesopores or macropores. In order to achieve this goal, a large amount of acidic or alkaline solution must be used, which not only causes environmental pollution, but also significantly reduces the crystallinity and quantity of the zeolite. The latter is to directly introduce mesopores and / or macropores into the zeolite crystals by using hard templates or organic templates as pore-forming agents during the synthesis process. In order to protect the zeolite structure, a complex post-processing process must be carried out when removing the hard template (carbonaceous and inorganic solid materials) from the synthetic zeolite, which makes the method costly, time-consuming and labor-intensive. Summary of the Invention

[0015] The purpose of the present invention is to provide a molecular sieve that saves time and labor, reduces costs and improves conversion rate.

[0016] To achieve the above-mentioned objectives, the present invention proposes a scandium-containing multi-level porous silica-alumina molecular sieve. The interior of the crystal particles in the molecular sieve forms a well-structured multi-level porous crystal structure at the nanoscale due to the pore-forming effect of scandium. The molecular sieve has MFI, MOR, FAU and Beta* microporous structures. The molecular sieve structure contains Lewis acidic sites and Bronsted acidic sites, and the intensity ratio of the Lewis acidic sites to the Bronsted acidic sites is adjustable.

[0017] The present invention also provides a method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve, which comprises the following steps:

[0018] Step 1: Weigh an aluminum source and a template, dissolve them in deionized water, mix them with the scandium metal ion solution, and stir to form a mixture.

[0019] Step 2: Add silicon source to the mixture and mix well;

[0020] Step 3: subjecting the mixed solution obtained in step 2 to hydrothermal crystallization, and after the crystallization is completed, filtering, washing, drying and calcining the obtained solid in sequence to obtain a scandium-containing hierarchical porous silica-alumina molecular sieve;

[0021] Furthermore, the aluminum source is one or more of Al2(SO4)3, NaAlO2 or Al(OH)3.

[0022] Furthermore, the silicon source is one or more of silica sol, silicon oxide, tetraethyl orthosilicate or fumed silica.

[0023] Furthermore, the stirring temperature in step 1 is room temperature 20-30° C., and the stirring speed is 200-1000 rpm / min.

[0024] Furthermore, in step 3, the crystallization is carried out by a hydrothermal method, and the specific process is as follows: the mixed solution obtained in step 2 is placed in a Teflon-lined metal reactor, and treated at 90-190° C. for 48-120 hours, the obtained solid material is washed with distilled water and dried at 80° C. overnight, and after drying, it is placed in a muffle furnace and calcined for 12 hours at a calcination temperature of 550° C.;

[0025] Furthermore, in step 3, the drying temperature is 50-90°C, the drying time is 24h-72h, the calcination temperature is 500°C to 600°C, the heating rate is 1°C / min to 3°C / min, and the calcination time is 6h to 12h.

[0026] Furthermore, a sodium source may be added to the mixture of step 1, and the sodium source, aluminum source and template agent are weighed and dissolved in deionized water, mixed with the metal scandium ion solution, and stirred to form a mixture. The preparation process of the scandium-containing multi-level porous silica-alumina molecular sieve further includes step 4: ion-exchanging the scandium-containing multi-level porous silica-alumina molecular sieve obtained in step 3, and then drying and calcining to obtain the scandium-containing multi-level porous silica-alumina molecular sieve after ion exchange. The specific method of step 4 is:

[0027] 4.1: Prepare 8 g / L ammonium chloride solution by mixing 4 g of solid ammonium chloride with 500 mL of deionized water in a volumetric flask.

[0028] 4.2: Weigh 1 g of the scandium-containing multi-stage molecular sieve obtained in step 4, place it in 50 mL of ammonium chloride solution using an 80°C oil bath, stir for 2 h, and then wash the obtained molecular sieve with water several times;

[0029] 4.3: The washed molecular sieve was dried at 60°C for 24 hours and then placed in a muffle furnace for calcination. The calcination process was to heat from room temperature (25°C) to 550°C for 6 hours at a heating rate of 1.458°C / min. The temperature was maintained at 550°C for 6 hours and then naturally cooled.

[0030] 4.4: Repeat steps 4.1-4.3 2 to 5 times.

[0031] Furthermore, the preparation method of the MFI structured scandium-containing silicon-aluminum molecular sieve is as follows:

[0032] I1: Aluminum source, sodium source and template are added to water in sequence and stirred at a certain speed to obtain solution A;

[0033] I2: preparing a scandium ion solution of a certain concentration, adding the scandium ion solution to the solution A, stirring and aging at room temperature for 1-10 hours to obtain a mixture B;

[0034] I3: Adding a silicon source to mixture B and stirring to obtain solution C, wherein the molar ratio of the components in solution C is SiO2:TEAOH:Al2O3:Na2O:H2O:Sc=50-150:1-100:1.25-100:0-100:10-5000:0.3-10;

[0035] I4: placing solution C in a Teflon-lined metal reactor and hydrothermally crystallizing it at 90-190° C. for 48-120 hours; after the crystallization, filtering, washing, drying, and calcining are performed in sequence to obtain a scandium-containing multi-level porous silica-alumina molecular sieve Sc-MFI-5 with an MFI microporous structure;

[0036] I5: The Sc-MFI-5 molecular sieve is ion-exchanged with an ammonium chloride solution at a temperature of 40° C. to 160° C., and then dried and calcined to obtain an ion-exchanged scandium-containing multi-level porous silica-alumina molecular sieve, namely, Sc-ZSM-5 molecular sieve.

[0037] The Sc-ZSM-5 molecular sieve is used in the methanol-to-olefins reaction. The Sc in Sc-ZSM-5 improves the selectivity for propylene by adjusting the acidity of ZSM-5 and the spatial and skeletal distribution of Al, selectively regulates light olefins, has a more open pore structure, and exhibits a catalytic life longer than traditional ZSM-5.

[0038] The method for preparing the scandium-containing multi-level porous silicon-aluminum molecular sieve with a MOR microporous structure is as follows:

[0039] R1: Weigh the aluminum source and sodium source, dissolve them in deionized water, and stir until completely dissolved to obtain solution D. The specific steps are as follows: use a precision balance and weighing paper, weigh the aluminum source with a medicine spoon, roll up the weighing paper, and pour the weighed aluminum source into a clean 50ml polytetrafluoroethylene autoclave liner. Then, weigh the granular sodium source using the same method, place it in the polytetrafluoroethylene liner, and use a rubber-tipped dropper to draw deionized water from a glass bottle and add it dropwise to the above liner. Mix with the aluminum source and sodium source, add a magnet, and stir at 400 rpm for 30 minutes until the sample is completely dissolved after mixing and the solution is clear, forming solution D.

[0040] R2: Scandium hydroxide was placed in a small glass bottle, and deionized water was added dropwise to the small glass bottle, and stirred at 400 rpm for 15 minutes until the solution was clear, thereby completing the preparation of the metal scandium ion solution. The prepared metal scandium ion solution was mixed with the solution D and placed in the liner, and the template was drawn with a rubber dropper and added dropwise to the above liner mixture, and stirred to mix evenly to form solution E;

[0041] R3: Slowly add a silicon source dropwise to the solution E using a rubber-tipped dropper, place the mixture on a magnetic stirrer and stir at 400 rpm, and stir at room temperature of 25°C for 5 hours to form a solution F, wherein the molar ratio of the substances in the solution F is SiO2:NaAlO2:NaOH:TEAOH:H2O:Sc(OH)3=1:0.01-0.4:0.01-0.5:0-1.0:1-100:0.01-0.5;

[0042] R4: The solution F is placed in a reactor and hydrothermally crystallized at 170° C. for 72 hours. After the hydrothermal crystallization, the solution is filtered, washed, and dried in sequence. The solution is then placed in a muffle furnace and heated to 550° C. for 300 minutes for calcination. The solution is then calcined in air at 550° C. for 6 hours, cooled naturally, and rinsed with 500 ml of deionized water several times until the pH of the washed aqueous solution reaches 7. The resulting solid is dried in an oven at 80° C. for 3 hours to obtain a scandium-containing multi-level porous silicon-aluminum molecular sieve Sc-MOR with a MOR microporous structure.

[0043] R5: performing ion exchange and water washing on the Sc-MOR molecular sieve to obtain the ion-exchanged Sc-MOR molecular sieve.

[0044] The Sc-MOR molecular sieve is applied to the dimethyl ether carbonylation reaction and can effectively improve the product yield.

[0045] The preparation method of the FAU structured scandium-containing silicon-aluminum molecular sieve is specifically as follows:

[0046] F1: Weigh a sodium source and dissolve it in deionized water to obtain solution G;

[0047] F2: dissolving the scandium source and the aluminum source in deionized water, mixing the solution with the solution G, and stirring to form a solution H;

[0048] F3: Under strong stirring, add silicon source dropwise to the solution H and continue stirring for 2 hours to form solution I. The molar ratio of the components in the solution I is SiO2:Na2O:Al2O3:H2O:Sc(OH)3=100:0.01-30:0.01-50:100-5000:0.1-25;

[0049] F4: The solution I is placed in a polytetrafluoroethylene-lined reactor and subjected to hydrothermal crystallization treatment at high temperature. After the hydrothermal treatment, the solution is filtered, washed, and dried in sequence. The solution is then placed in a muffle furnace and calcined by heating to 550° C. for 300 minutes. The solution is then calcined in air at 550° C. for 6 hours, cooled naturally, and rinsed with 500 ml of deionized water several times until the pH of the washed aqueous solution reaches 7. The resulting solid is dried in an oven at 80° C. for 3 hours to obtain a scandium-containing multi-level porous silicon-aluminum molecular sieve Sc-FAU with a FAU microporous structure.

[0050] F5: performing ion exchange and water washing on the Sc-FAU molecular sieve to obtain the ion-exchanged Sc-FAU molecular sieve.

[0051] The preparation method of the Beta* structured scandium-containing silicon-aluminum molecular sieve is specifically as follows:

[0052] T1: Weigh the sodium source and aluminum source and dissolve them in deionized water. Mix and stir under the action of a magnetic field at 400 rpm / min for 30 min until the sample is completely dissolved to obtain solution J.

[0053] T2: preparing a metal scandium ion solution, mixing it with the solution J, and adding the template dropwise, stirring and mixing until uniform, to form a solution K;

[0054] T3: adding a silicon source to the solution K, stirring the mixture at a speed of 400 rpm / min under the action of a magnetic field at room temperature of 25° C. for 5 h to form a solution L, wherein the molar ratio of the components in the solution L is SiO2:Na2O:TEAOH:Al2O3:H2O:Sc(OH)3=100:0.01-40:0.01-100:0.01-50:100-8000:0.01-20;

[0055] T4: The solution L is placed in a reactor and hydrothermally crystallized at 170° C. for 72 hours. After the hydrothermal crystallization, the solution is filtered, washed, and dried in sequence. The solution is then placed in a muffle furnace and heated to 550° C. for 300 minutes for calcination. The solution is then air-calcined at 550° C. for 6 hours, cooled naturally, and rinsed with 500 ml of deionized water several times until the pH of the washed aqueous solution reaches 7. The resulting solid is dried in an oven at 80° C. for 3 hours to obtain a Beta* structured scandium-containing hierarchical porous silicon-aluminum molecular sieve Sc-Beta.

[0056] T5: performing ion exchange and water washing on the Sc-Beta molecular sieve to obtain the ion-exchanged Sc-Beta molecular sieve.

[0057] Furthermore, the template includes tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide and other commonly used MFI, FAU, MOR, BEA* synthetic templates.

[0058] The scandium-containing multi-level porous silica-alumina molecular sieve of the present invention uses silica sol as a silicon source. First, sodium aluminate is dissolved under weak alkaline conditions, and a template agent and Sc hydroxide are added. After being assisted by high-temperature water vapor, the structure-guiding effect of the microporous template agent is used to ensure that the molecular sieve has a highly ordered three-dimensional stacking structure while having micropores guided by the microporous template agent. The method has mild synthesis conditions, a short synthesis cycle, and simple operation.

[0059] Compared with the prior art, the advantages of the present invention are:

[0060] 1. The scandium-containing multi-level porous silicon-alumina molecular sieve of the present invention forms ordered mesopores with regular structure at the nanoscale under the pore-forming effect of scandium by introducing metallic scandium ions. There is no need to add organic or inorganic pore-forming agents, which is free from the limitation of carbon templates, reduces template consumption, greatly reduces synthesis time and economic costs, significantly improves single-reactor output, and is easy to scale up for industrial synthesis.

[0061] 2. Four types of multi-level pore molecular sieves with different topological structures were synthesized using the preparation method of the present invention. Among them, the Sc-ZSM-5 zeolite molecular sieve is used in the methanol to olefin reaction. Due to its more open pore structure, it exhibits a catalytic life longer than that of traditional ZSM-5, thereby improving the product yield. At the same time, the Sc in the Sc-ZSM-5 molecular sieve improves the selectivity of propylene by adjusting the acidity of ZSM-5 and the spatial skeleton distribution of Al.

[0062] 3. The Sc-MOR molecular sieve synthesized by the present invention is used in the carbonylation reaction of dimethyl ether, effectively improving the product yield.

[0063] 4. In the preparation method of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention, metal ions Sc are introduced, and the pore structure, skeleton structure, and active sites thereof are adjusted by Sc so that the sieve has both microporous and mesoporous channels. While maintaining the advantages of high catalytic activity and high stability of the microporous molecular sieve, the diffusion performance is increased, thereby helping to reduce the residence time of the reactants in the acidic environment and maintain the selectivity of the micropores; and the presence of the mesopores allows the reactants to be separated from the reactor more quickly, thereby improving the efficiency of the catalyst; the addition of the mesopores can increase the mass transfer efficiency of the substance, thereby improving the catalytic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The XRD patterns of the scandium-containing multi-level porous silica-alumina molecular sieves Sc-ZSM-5 of Examples 1-5 and the commercial bulk ZSM-5 molecular sieve of Comparative Example 1 are shown;

[0065] Figure 2 This is a scanning electron microscope image of the commercial bulk ZSM-5 molecular sieve of Comparative Example 1 of the present invention;

[0066] Figure 3 This is a scanning electron microscope image of Sc-ZSM-5 of Example 4 of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention;

[0067] Figure 4 This is a scanning electron microscope image of Sc-ZSM-5 of Example 5 of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention;

[0068] Figure 5 This is a scanning electron microscope image of Sc-ZSM-5 of Example 6 of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention;

[0069] Figure 6 Comparison of N2 adsorption and desorption isotherms of Comparative Example 1 and Example 2;

[0070] Figure 7 This is a pore size distribution diagram of Example 2 of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention;

[0071] Figure 8 This is the XRD pattern of the scandium-containing multi-level porous silica-alumina molecular sieve Sc-MOR in Example 7;

[0072] Figure 9 This is the XRD pattern of the scandium-containing multi-level porous silica-alumina molecular sieve Sc-FAU in Example 7;

[0073] Figure 10 This is the XRD pattern of the scandium-containing multi-level porous silica-alumina molecular sieve Sc-Beta in Example 7; DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further described below.

[0075] The present invention provides a scandium-containing multi-level porous silica-alumina molecular sieve. The interior of the crystal particles in the molecular sieve forms a well-structured multi-level porous crystal structure at the nanoscale due to the pore-forming effect of scandium. The molecular sieve has MFI, MOR, FAU and Beta* microporous structures, and contains Lewis acid sites and Brønsted acid sites in the structure. The intensity of the Lewis acid sites and the intensity ratio of the Brønsted acid sites are adjustable. The preparation of the scandium-containing multi-level porous silica-alumina molecular sieve includes the following steps:

[0076] Step 1: Weigh an aluminum source and a sodium source, dissolve them in deionized water, mix them with the scandium metal ion solution, and stir to form a mixture;

[0077] Step 2: Add silicon source to the mixture in step 1 and mix well;

[0078] Step 3: subjecting the mixed solution obtained in step 2 to hydrothermal crystallization, and after the crystallization is completed, filtering, washing, drying and calcining the obtained solid in sequence to obtain a scandium-containing hierarchical porous silica-alumina molecular sieve;

[0079] Step 4: subjecting the scandium-containing multi-level molecular sieve obtained in step 3 to ion exchange, followed by drying and calcination to obtain the scandium-containing multi-level porous silica-alumina molecular sieve after ion exchange.

[0080] According to the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention, the following examples and comparative examples are provided:

[0081] Example 1:

[0082] This Example 1 proposes a Sc-ZSM-5 molecular sieve, the preparation method of which is as follows:

[0083] Step 1: Using a precision balance and weighing paper, weigh appropriate amounts of NaAlO2, TPAOH, and water and add them to a polytetrafluoroethylene autoclave liner. Stir at a constant speed to obtain solution A.

[0084] Step 2: Prepare a scandium hydroxide solution of a certain concentration, add it to solution A, and stir and age it at room temperature for 1-10 hours to obtain mixture B;

[0085] Step 3: Add silica to mixture B and stir to obtain solution C, wherein the molar ratio of the components in solution C is SiO2:TPAOH:Al2O3:H2O:Sc(OH)3=100:20:2:2500:10;

[0086] Step 4: Solution C was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 180°C for 120 hours; after the crystallization was completed, it was filtered, washed and dried in sequence, and then placed in a muffle furnace, heated to 550°C for 300 minutes, and calcined in air at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7, and then the obtained solid was placed in an oven at 80°C and dried for 3 hours to obtain Sc-MFI-5 molecular sieve;

[0087] Step 5: The Sc-MFI-5 molecular sieve obtained in step 4 was ion exchanged with an ammonium chloride solution. 4 g of ammonium chloride solid and 500 mL of deionized water were used to prepare an 8 g / L ammonium chloride solution in a volumetric flask, and 1 g of the above molecular sieve was placed in 50 mL of ammonium chloride solution. An 80 ° C oil bath was used and stirred for 2 hours. The obtained molecular sieve was washed with water several times, dried at 60 ° C for 24 hours after washing, and then placed in a muffle furnace for calcination: room temperature 25 ° C (heating for 6 hours) to 550 ° C, the heating rate was 1.458 ° C / min, and calcined at 550 ° C for 6 hours, and finally cooled naturally to obtain the Sc-MFI-5 molecular sieve after ion exchange in Example 1.

[0088] Example 2:

[0089] This Example 2 proposes a Sc-ZSM-5 molecular sieve, the preparation method of which is as follows:

[0090] Step 1: Using a precision balance and weighing paper, weigh 0.0998 g of NaAlO2 and pour it into the polytetrafluoroethylene autoclave liner. Use a rubber dropper to draw 2.88 g of deionized water and add it dropwise to the liner. Stir under magnetic stirring at 400 rpm / min for 30 minutes until the drug is completely dissolved to obtain Solution A.

[0091] Step 2: 0.09598 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added dropwise to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear and a solution was formed, thereby completing the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution A, and 2.0336 g of tetrapropylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture B;

[0092] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2， The mixture was slowly added dropwise to the mixture B within 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution C. The molar ratio of the components in the solution C was SiO2:TPAOH:Al2O3:H2O:Sc(OH)3=100:20:2:2500:5;

[0093] Step 4: Solution C was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 180°C for 120 hours; after the crystallization was completed, it was filtered, washed and dried in sequence, then placed in a muffle furnace, heated to 550°C in 300 minutes, and air-calcined at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7, and then the obtained solid was placed in an oven at 80°C and dried for 3 hours to obtain Sc-MFI-5 molecular sieve.

[0094] Example 3:

[0095] This Example 3 proposes a Sc-ZSM-5 molecular sieve, the preparation method of which is as follows:

[0096] Step 1: Using a precision balance and weighing paper, weigh 0.0998 g of NaAlO2 and pour it into the polytetrafluoroethylene autoclave liner. Use a rubber dropper to draw 2.88 g of deionized water and add it dropwise to the liner. Stir under magnetic stirring at 400 rpm / min for 30 minutes until the drug is completely dissolved to obtain Solution A.

[0097] Step 2: 0.06399 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear to form a solution, thereby completing the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution A, and 2.0336 g of tetrapropylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture B;

[0098] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2，The mixture was slowly added dropwise to the mixture B within 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution C. The molar ratio of the components in the solution C was SiO2:TPAOH:Al2O3:H2O:Sc(OH)3=100:20:2:2500:3.3;

[0099] Step 4: Solution C was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 180°C for 120 hours; after the crystallization was completed, it was filtered, washed and dried in sequence, then placed in a muffle furnace, heated to 550°C in 300 minutes, and air-calcined at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7, and then the obtained solid was placed in an oven at 80°C and dried for 3 hours to obtain Sc-MFI-5 molecular sieve.

[0100] Example 4:

[0101] This Example 4 proposes a Sc-ZSM-5 molecular sieve, the preparation method of which is as follows:

[0102] Step 1: Using a precision balance and weighing paper, weigh 0.0998 g of NaAlO2 and pour it into the polytetrafluoroethylene autoclave liner. Use a rubber dropper to draw 2.88 g of deionized water and add it dropwise to the liner. Stir under magnetic stirring at 400 rpm / min for 30 minutes until the drug is completely dissolved to obtain Solution A.

[0103] Step 2: 0.04799 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear and a solution was formed to complete the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution A, and 2.0336 g of tetrapropylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture B;

[0104] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2， The mixture was slowly added dropwise to the mixture B within 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution C. The molar ratio of the components in the solution C was SiO2:TPAOH:Al2O3:H2O:Sc(OH)3=100:20:2:2500:2.5;

[0105] Step 4: Solution C was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 170°C for 72 hours; after the crystallization was completed, it was filtered, washed and dried in sequence, then placed in a muffle furnace, heated to 550°C in 300 minutes, and air-calcined at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7. The resulting solid was then placed in an oven at 80°C and dried for 3 hours to obtain Sc-MFI-5 molecular sieve.

[0106] Example 5

[0107] This Example 5 proposes a Sc-ZSM-5 molecular sieve, the preparation method of which is as follows:

[0108] Step 1: Using a precision balance and weighing paper, weigh 0.0998 g of NaAlO2 and pour it into the polytetrafluoroethylene autoclave liner. Use a rubber dropper to draw 2.88 g of deionized water and add it dropwise to the liner. Stir under magnetic stirring at 400 rpm / min for 30 minutes until the drug is completely dissolved to obtain Solution A.

[0109] Step 2: 0.0384 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear to form a solution, thereby completing the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution A, and 2.0336 g of tetrapropylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture B;

[0110] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2， The mixture was slowly added dropwise to the mixture B within 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution C. The molar ratio of the components in the solution C was SiO2:TPAOH:Al2O3:H2O:Sc(OH)3=100:20:2:2500:2;

[0111] Step 4: Solution C was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 170°C for 72 hours; after the crystallization was completed, it was filtered, washed and dried in sequence, then placed in a muffle furnace, heated to 550°C in 300 minutes, and air-calcined at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7. The resulting solid was then placed in an oven at 80°C and dried for 3 hours to obtain Sc-MFI-5 molecular sieve.

[0112] Example 6

[0113] This Example 6 proposes a Sc-ZSM-5 molecular sieve, the preparation method of which is as follows:

[0114] Step 1: Using a precision balance and weighing paper, weigh 0.0205 g of NaAlO2 and pour it into the polytetrafluoroethylene autoclave liner. Use a rubber dropper to draw 2.88 g of deionized water and add it dropwise to the liner. Stir under magnetic stirring at 400 rpm / min for 30 min until the drug is completely dissolved to obtain Solution A.

[0115] Step 2: 0.0384 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear to form a solution, thereby completing the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution A, and 2.0336 g of tetrapropylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture B;

[0116] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2， The mixture was slowly added dropwise to the mixture B within 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution C. The molar ratio of the components in the solution C was SiO2:TPAOH:Al2O3:H2O:Sc(OH)3=100:20:2:2500:1;

[0117] Step 4: Solution C was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 170°C for 72 hours; after the crystallization was completed, it was filtered, washed and dried in sequence, then placed in a muffle furnace, heated to 550°C in 300 minutes, and air-calcined at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7. The resulting solid was then placed in an oven at 80°C and dried for 3 hours to obtain Sc-MFI-5 molecular sieve.

[0118] Example 7

[0119] This Example 7 proposes a Sc-MOR molecular sieve, the preparation method of which is as follows:

[0120] Step 1: Using a precision balance and weighing paper, weigh 0.11 g of NaAlO2 and 0.32 g of NaOH into a polytetrafluoroethylene autoclave liner. Use a rubber dropper to pipette 2.88 g of deionized water and add it dropwise to the liner. Stir at 400 rpm / min under magnetic stirring for 30 min until the drugs are completely dissolved to obtain Solution D.

[0121] Step 2: 0.0384 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear to form a solution, thereby completing the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution D, and 0.7 g of tetraethylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture E;

[0122] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2， The mixture was slowly added dropwise to the mixture E within 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution F. The molar ratio of the components in the solution F was SiO2:NaAlO2:NaOH:H2O:Sc(OH)3=100:23:6.7:3000:500:5;

[0123] Step 4: Solution F was placed in a Teflon-lined metal reactor and hydrothermally crystallized at 170°C for 72 hours; after the crystallization, it was filtered, washed and dried in sequence, then placed in a muffle furnace, heated to 550°C over 300 minutes, and calcined in air at 550°C for 6 hours, then cooled naturally, and then rinsed with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution was 7. The resulting solid was then placed in an oven and dried at 80°C for 3 hours to obtain Sc-MOR molecular sieve;

[0124] Step 5: The Sc-MOR molecular sieve obtained in step 4 was ion exchanged with an ammonium chloride solution. 4 g of ammonium chloride solid and 500 mL of deionized water were used to prepare an 8 g / L ammonium chloride solution in a volumetric flask, and 1 g of the above molecular sieve was placed in 50 mL of ammonium chloride solution. An 80 ° C oil bath was used and stirred for 2 hours. The obtained molecular sieve was washed with water several times, dried at 60 ° C for 24 hours after washing, and then placed in a muffle furnace for calcination: room temperature 25 ° C (heating for 6 hours) to 550 ° C, the heating rate was 1.458 ° C / min, and calcined at 550 ° C for 6 hours, and finally cooled naturally to obtain the Sc-MOR molecular sieve after ion exchange in Example 7.

[0125] Example 8

[0126] This Example 8 proposes a Sc-FAU molecular sieve, the preparation method of which is as follows:

[0127] Step 1: Weigh 3.68 g of NaOH and dissolve it in deionized water to obtain solution G;

[0128] Step 2: Dissolve 0.32 g of scandium hydroxide and 3.18 g of Al(OH)3 in deionized water to form solution H;

[0129] Step 3: Under strong stirring, 16g of silica solution and solution G are added to solution H, and stirring is continued for 2h to form solution I, wherein the molar ratio of each component in solution I is SiO2:Na2O:Al2O3:H2O:Sc(OH)3=7.5:2.3:3:150:0.25; Step 4: The solution I is placed in a reactor lined with polytetrafluoroethylene, and hydrothermally crystallized at high temperature. After the hydrothermal treatment, it is filtered, washed, and dried in sequence, and then placed in a muffle furnace, and the temperature is raised to 550°C in the muffle furnace for 300min, calcined, and calcined in air at 550°C for 6h, and then cooled naturally, and then rinsed with 500ml of deionized water several times until the pH of the rinsed aqueous solution is 7. The resulting solid is placed in an oven at 80°C and dried for 3h to obtain Sc-FAU molecular sieve;

[0130] Step 5: The Sc-FAU molecular sieve obtained in step 4 was ion exchanged with an ammonium chloride solution. 4 g of ammonium chloride solid and 500 mL of deionized water were used to prepare an 8 g / L ammonium chloride solution in a volumetric flask, and 1 g of the above molecular sieve was placed in 50 mL of ammonium chloride solution. An 80 ° C oil bath was used and stirred for 2 hours. The obtained molecular sieve was washed with water several times, dried at 60 ° C for 24 hours after washing, and then placed in a muffle furnace for calcination: room temperature 25 ° C (heating for 6 hours) to 550 ° C, the heating rate was 1.458 ° C / min, and calcined at 550 ° C for 6 hours, and finally cooled naturally to obtain the Sc-FAU molecular sieve after ion exchange in Example 8.

[0131] Example 9

[0132] This Example 9 proposes a Sc-Beta molecular sieve, the preparation method of which is as follows:

[0133] Step 1: Using a precision balance and weighing paper, weigh 0.205 g of NaAlO2 and 0.1396 g of NaOH into a polytetrafluoroethylene autoclave liner. Use a rubber-tipped dropper to draw 2.88 g of deionized water and add it dropwise to the liner. Stir at 400 rpm / min under magnetic stirring for 30 min until the drugs are completely dissolved to obtain Solution J.

[0134] Step 2: 0.0384 g of scandium hydroxide was placed in a small glass bottle, 2.88 g of deionized water was added to the small glass bottle, and the mixture was stirred at 400 rpm for 15 minutes until the solution became clear to form a solution, thereby completing the preparation of the scandium hydroxide solution. The prepared scandium hydroxide solution was added to solution J, and 1.47 g of tetraethylammonium hydroxide (template) was added dropwise. The mixture was stirred at room temperature for 15 minutes to obtain a mixture K;

[0135] Step 3: Use a rubber-tipped dropper to draw 4.44 g of SiO 2，The mixture was slowly added dropwise to the mixture K over 15 minutes, and then stirred at room temperature of 25°C for 5 hours using a magnetic stirrer at 400 rpm / min to obtain a solution L. The molar ratio of the components in the solution L was SiO2:TEAOH:Al2O3:Na2O:H2O:Sc(OH)3=100:20:0.625:10:1600:2;

[0136] Step 4: Place solution L in a Teflon-lined metal reactor and hydrothermally crystallize it at 170°C for 72 hours; after the crystallization is completed, filter, wash and dry it in sequence, then place it in a muffle furnace, heat it to 550°C in 300 minutes, and calcine it in air at 550°C for 6 hours, then cool it naturally, and then rinse it with 500 ml of deionized water several times until the pH of the final rinsed aqueous solution is 7. Then, place the resulting solid in an oven at 80°C and dry it for 3 hours to obtain Sc-Beta molecular sieve;

[0137] Step 5: The Sc-Beta molecular sieve obtained in step 4 was ion exchanged with an ammonium chloride solution. 4 g of ammonium chloride solid and 500 mL of deionized water were used to prepare an 8 g / L ammonium chloride solution in a volumetric flask, and 1 g of the above molecular sieve was placed in 50 mL of ammonium chloride solution. An 80°C oil bath was used and stirred for 2 hours. The obtained molecular sieve was washed with water several times, dried at 60°C for 24 hours after washing, and then placed in a muffle furnace for calcination: the room temperature was 25°C (heating for 6 hours) and the temperature was increased to 550°C at a heating rate of 1.458°C / min. The calcination was continued at 550°C for 6 hours, and then the temperature was naturally cooled to obtain the Sc-Beta molecular sieve after ion exchange in Example 9.

[0138] Comparative Example 1

[0139] Comparative Example 1 is a commercial bulk ZSM-5 molecular sieve, which is subjected to ion exchange treatment. 4 g of ammonium chloride solid and 500 mL of deionized water are used to prepare an 8 g / L ammonium chloride solution in a volumetric flask, and 1 g of the above molecular sieve is placed in 50 mL of ammonium chloride solution. An 80°C oil bath is used and stirred for 2 hours. The obtained molecular sieve is washed with water several times, dried at 60°C for 24 hours after washing, and then placed in a muffle furnace for calcination: the room temperature is 25°C (heating for 6 hours) to 550°C, the heating rate is 1.458°C / min, and calcination is continued at 550°C for 6 hours. Finally, the temperature is naturally lowered to obtain the commercial bulk ZSM-5 molecular sieve after ion exchange in Comparative Example 1.

[0140] Comparative Example 2

[0141] Comparative Example 2 is a commercial MOR zeolite molecular sieve. The commercial MOR zeolite molecular sieve is subjected to ion exchange treatment. 4 g of ammonium chloride solid and 500 mL of deionized water are used to prepare an 8 g / L ammonium chloride solution in a volumetric flask, and 1 g of the above molecular sieve is placed in 50 mL of ammonium chloride solution. An 80°C oil bath is used. After stirring for 2 hours, the obtained molecular sieve is washed with water several times, dried at 60°C for 24 hours after washing, and then placed in a muffle furnace for calcination: the room temperature is 25°C (heating for 6 hours) and the temperature is raised to 550°C at a heating rate of 1.458°C / min. The calcination is continued at 550°C for 6 hours, and finally the temperature is naturally lowered to obtain the commercial MOR zeolite molecular sieve after ion exchange in Comparative Example 2.

[0142] Experiment 1:

[0143] The scandium-containing multi-level porous silicon aluminum molecular sieve Sc-ZSM-5 in Examples 1-5 and the commercial bulk ZSM-5 molecular sieve in Comparative Example 1 were subjected to X-ray diffraction tests respectively, and the following results were obtained: Figure 1 The XRD patterns shown are from Figure 1 It can be seen that there are no impurity peaks in the XRD patterns of Examples 1-5, indicating that the scandium-containing multi-level porous silicon aluminum molecular sieves Sc-ZSM-5 of Examples 1-5 are all pure phase ZSM-5 molecular sieves.

[0144] Experiment 2:

[0145] Scanning electron microscope was performed on the scandium-containing multi-level porous silicon aluminum molecular sieve Sc-ZSM-5 of Examples 4-6 and the commercial bulk ZSM-5 molecular sieve of Comparative Example 1, respectively. Figure 2-5 SEM images of Figure 2 is the scanning electron microscope image of Comparative Example 1, Figure 3 is a scanning electron microscope image of Example 4, Figure 4 is a scanning electron microscope image of Example 5, Figure 5 This is a scanning electron microscope image of Example 6; by comparison, it can be found that the Sc-ZSM-5 molecular sieves of Examples 4-6 and the commercial bulk ZSM-5 molecular sieve have similar morphologies, and their crystals are composed of relatively evenly distributed nano-microcrystalline particles, and still present a coffin-like morphology with a smooth surface.

[0146] Experiment 3:

[0147] The scandium-containing multi-level porous silicon aluminum molecular sieve Sc-ZSM-5 of Example 2 and the commercial bulk ZSM-5 molecular sieve of Comparative Example 1 were subjected to N2 desorption-adsorption isothermal tests respectively. Figure 6 The N2 adsorption-desorption isotherm curve shown in FIG. 1 and the pore size distribution of Example 2 were analyzed to obtain the following: Figure 7 The pore size distribution diagram is shown.

[0148] Depend on Figure 6 and Figure 7It can be seen that compared with the commercial bulk ZSM-5 molecular sieve of comparative example 1, the scandium-containing multi-level porous silicon-alumina molecular sieve Sc-ZSM-5 of this embodiment 2 has a typical intercrystalline mesoporous hysteresis loop, proving that it has a micro-meso-multilevel porous structure.

[0149] Experiment 4:

[0150] In order to verify the catalytic effect of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention, the following MTO reaction performance evaluation was performed on Comparative Example 1 and Example 6 respectively:

[0151] MTO reaction process: quartz wool, molecular sieve (the molecular sieve samples of Comparative Example 1 and Example 6 above) and quartz sand are placed in a quartz tube in sequence to fix the molecular sieve in the quartz tube. The filled quartz tube is fixed in a fixed bed. Under a high-purity N2 environment of 25 mL / min, the catalyst bed is programmed to 550°C within 30 minutes, the molecular sieve is activated at 550°C for 1 hour, then cooled and stabilized at 450°C, and methanol is introduced to carry out the MTO reaction. The reaction products are then subjected to gas phase and chromatographic analysis to obtain the MTO reaction catalytic performance table of Comparative Example 1 and Example 6, as shown in Table 1 below.

[0152] The catalytic performance of molecular sieves for the methanol to hydrocarbons (MTH) reaction was tested in a fixed-bed reactor at atmospheric pressure: molecular sieve tablets were sieved to 20-40 mesh, 0.1-0.3 g of the formed catalyst was added to a quartz tube reactor, and the mixture was stirred at 823 K under a N2 atmosphere (40 mL min -1 ) for 1 hour, the reactor was adjusted to the ideal reaction temperature of 623-773K, and methanol vapor was injected into the reaction tube by a microinjector at a space velocity of 1-4h -1 , N2 flow rate is 40 mL min -1 The reaction products were analyzed online using an HP-PLOT / Q capillary column (30 m × 0.32 mm × 20 μm) and an FID detector. The reaction conversion and selectivity were calculated based on the chromatographic peak area. Dimethyl ether, produced by methanol dehydration, was considered the reactant. When the methanol conversion on the molecular sieve was less than 95%, the catalyst was considered deactivated.

[0153] Table 1: Catalytic performance of light olefins in MTO reaction of Comparative Example 1 and Example 6

[0154]

[0155] As can be seen from Table 1, the propylene selectivity of Comparative Example 1 is 35.21%, and the propylene selectivity of Example 6 is 52.64%. Therefore, it can be seen that the scandium-containing multi-level porous silica-alumina molecular sieve catalyst prepared by Example 6 of the present invention has an improved propylene selectivity of 17%.

[0156] Comparative Example 1: Low carbon olefins (C 1 -C 4 and C 2＝ +C 3＝ +C 4＝ ) selectivity 75.88%, Example 6 for light olefins (C 1 -C 4 and C 2＝ +C 3＝ +C 4＝ ) selectivity is 84.61%, thus showing that the selectivity of the scandium-containing multi-level porous silica-alumina molecular sieve catalyst prepared in Example 6 of the present invention for light olefins is increased by 8.73%;

[0157] In addition, the catalytic life of comparative example 1 is only about 7 hours, but the life of the scandium-containing multi-level porous silica-alumina molecular sieve catalyst prepared in Example 6 of the present invention reaches 24 hours, and its catalytic life is increased by 242%. This is because the scandium-containing multi-level porous silica-alumina molecular sieve has highly ordered and interconnected mesopores, which effectively reduces carbon deposition and thus increases the catalytic life.

[0158] Experiment 5:

[0159] In order to further verify the catalytic effect of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention, the MTO reaction performance of Comparative Example 1 and Examples 3-4 were evaluated respectively. The results are shown in Table 2 below:

[0160] Table 2: Catalytic performance of light olefins in MTO reaction of Comparative Example 1 and Examples 3-4

[0161]

[0162] As can be seen from Table 2, the propylene selectivity of Comparative Example 1 is 35.21%, while the propylene selectivities of Examples 3 and 4 are 35.2% and 34.6%, respectively. This shows that when the propylene selectivity is equivalent, the ethylene selectivity is reduced.

[0163] Comparative Example 1: Low carbon olefins (C 1 -C 4 and C 2＝ +C 3＝ +C 4＝ ) selectivity 75.88%, Examples 5 and 6 for light olefins (C 1 -C 4 and C 2＝ +C 3＝ +C 4＝ ) selectivities were 85% and 85.9%, respectively, further demonstrating that the scandium-containing multi-level porous silica-alumina molecular sieve catalysts prepared in Example 3 and Example 4 of the present invention have significantly improved selectivity for light olefins.

[0164] In addition, it can be found from Table 2 that the propylene / ethylene ratio of Comparative Example 1 is 2.54, while the propylene / ethylene ratios of Examples 5 and 6 are 3.32 and 2.95, respectively. The propylene / ethylene ratios of Examples 5 and 6 are increased compared with Comparative Example 1, further indicating that the scandium-containing multi-level porous silica-alumina molecular sieve prepared by the present invention effectively improves the selectivity of propylene.

[0165] Experiment 6:

[0166] Comparative Example 1 and Example 6 were subjected to toluene disproportionation reaction performance evaluation tests, as follows:

[0167] Toluene disproportionation reaction process: The sample of comparative example 1 and the sample of example 6 were tableted, and then ground and sieved into 20-40 mesh particles. The reaction temperature was 360-420°C and the reaction temperature was 1.0-4.0 hours. -1 Toluene methylation evaluation experiments were conducted at a space velocity of 1.5 mol / L. The molar ratios of toluene to methanol (T / M) were 0.5, 1.0, 2.0, and 3.0, respectively. Nitrogen was used as the carrier gas at a flow rate of 40 mL / min. Deionized water was preheated to steam in a 250°C preheating furnace under conditions of water and nitrogen flow. The molar ratio of steam to reaction materials was n(H2O) / n(T+M) = 4. The reaction products were analyzed by chromatography, and the results are shown in Table 3:

[0168] Table 3: Catalytic performance of toluene disproportionation reaction of Comparative Example 1 and Example 6:

[0169]

[0170] It can be seen from Table 3 that the toluene conversion rate of Comparative Example 1 is 6.5%, while that of Example 6 is 9.3%, an increase of 2.8%. The conversion rate of p-xylene also increases from 4.32% to 6.05%, effectively improving the yield of the product.

[0171] Experiment 7:

[0172] The scandium-containing multi-level porous silicon aluminum molecular sieve Sc-MOR molecular sieve of Example 7 was subjected to X-ray diffraction to obtain an XRD pattern, as shown in FIG. Figure 8 As shown, from Figure 8 It can be seen that there are no impurity peaks in the XRD spectrum of Example 7, indicating that the scandium-containing multi-level porous silicon-aluminum molecular sieve Sc-MOR molecular sieve in Example 7 is a pure phase MOR molecular sieve.

[0173] Experiment 8:

[0174] The scandium-containing multi-level porous silicon aluminum molecular sieve Sc-FAU molecular sieve of Example 8 was subjected to X-ray diffraction to obtain an XRD pattern, as shown in FIG. Figure 9 As shown, from Figure 9It can be seen that there are no impurity peaks in the XRD spectrum of Example 8, indicating that the scandium-containing multi-level porous silica-alumina molecular sieve Sc-FAU molecular sieve of Example 8 is a pure phase FAU molecular sieve.

[0175] Experiment 9:

[0176] The scandium-containing multi-level porous silicon aluminum molecular sieve Sc-Beta molecular sieve sample of Example 9 was subjected to X-ray diffraction to obtain an XRD pattern, as shown in FIG. Figure 10 As shown, from Figure 10 It can be seen that there are no impurity peaks in the XRD spectrum of Example 9, indicating that the scandium-containing multi-level porous silicon-aluminum molecular sieve Sc-Beta molecular sieve of Example 9 is a pure phase Beta molecular sieve.

[0177] Experiment 10:

[0178] In order to verify the catalytic effect of the scandium-containing multi-level porous silica-alumina molecular sieve of the present invention on the hydroxylation reaction of dimethyl ether, the commercial MOR zeolite molecular sieve of Comparative Example 2 and the Sc-MOR molecular sieve of Example 7 were respectively subjected to dimethyl ether hydroxylation reaction performance evaluation tests, as follows:

[0179] The dimethyl ether hydroxylation reaction process: The catalyst powder (the commercial MOR zeolite molecular sieve used in Comparative Example 2 and the scandium-containing hierarchical silica-alumina molecular sieve Sc-MOR molecular sieve used in Example 7, respectively) was first pressed into tablets at 30 MPa for 8 minutes. After crushing and screening, 40-60 mesh particles were obtained. 0.5 g (approximately 1 mL) of catalyst particles were weighed and loaded into a reaction tube. A small amount of quartz wool and approximately 1.5 mL of quartz sand (20-40 mesh) were placed below the catalyst to support the catalyst bed. Approximately 1 mL of quartz sand was placed above the catalyst to distribute and preheat the intake airflow. After catalyst loading, the reaction tube was installed. After confirming that the inlet and outlet connections of the reaction tube were properly secured, N2 was introduced to the reaction pressure and the airtightness was checked to ensure that the device was leak-free. After passing the airtightness test, N2 was introduced for pretreatment. The pretreatment procedure was as follows: the temperature was increased from room temperature to 200°C at a rate of 2°C / min and held for 9 hours. After the pretreatment, the inlet gas was switched from N2 to a reaction mixture (DME / CO = 1 / 49), wherein the reaction pressure was 1.5 MPa, the reaction temperature was 200 °C, and the reaction gas volume space velocity (GHSV) was 6000 h -1 After the reaction started, a chromatographic analysis sequence was set up to perform regular sampling and analysis of the reaction exhaust gas. The analysis results are shown in Table 4 below. After the reaction was completed, the reactor stopped heating and the inlet gas was switched to N2 for purging and cooling.

[0180] Table 4: Catalytic performance of dimethyl ether carbonylation in Example 7

[0181]

[0182] As can be seen from Table 4, when the commercial MOR zeolite molecular sieve of Comparative Example 2 is used as the catalyst, the dimethyl ether conversion rate is 47.3%, while when the scandium-containing multi-level porous silica-alumina molecular sieve Sc-MOR molecular sieve of Example 7 is used as the catalyst, the dimethyl ether conversion rate is increased to 59.6%. This shows that the introduction of Sc in the present invention effectively improves the mass transfer efficiency and the conversion rate while maintaining the MOR microporous structure.

[0183] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. A scandium-containing multi-level porous silicon aluminum molecular sieve, characterized in that: The molecular sieve introduces metal Sc ions, forming a well-structured multi-level porous crystal structure at the nanoscale, so that the molecular sieve has both microporous and mesoporous channels; the molecular sieve has MFI, MOR, FAU and Beta* microporous structures, and the molecular sieve structure contains Lewis acid sites and Brønsted acid sites, and the intensity ratio of the acid sites is adjustable; wherein the Sc source is scandium hydroxide; The preparation method of the scandium-containing multi-level porous silica-alumina molecular sieve comprises the following steps: Step 1: Weighing an aluminum source and a template, dissolving them in deionized water, and mixing them with a metal scandium ion solution, stirring and mixing them evenly to form a mixture; the metal scandium ion solution is a scandium hydroxide solution; Step 2: Add silicon source to the mixture and mix well; Step 3: The mixed solution obtained in step 2 is subjected to hydrothermal crystallization treatment. After the crystallization is completed, the obtained solid is filtered, washed, dried and calcined in sequence to obtain a scandium-containing multi-level porous silica-alumina molecular sieve.

2. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 1, characterized in that: The aluminum source is one or more of Al2(SO4)3, NaAlO2 or Al(OH)3).

3. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 1, characterized in that: The silicon source is one or more of silica sol, silicon oxide, tetraethyl orthosilicate or fumed silica.

4. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 1, characterized in that: The stirring temperature in step 1 is room temperature 20-30°C, and the stirring speed is 200-1000rpm / min; the drying temperature in step 3 is 50-90°C, the drying time is 24h-72h, the calcination temperature is 500°C to 600°C, the heating rate is 1°C / min to 3°C / min, and the calcination time is 6h to 12h.

5. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 1, characterized in that: A sodium source may be further added to the mixture in step 1, and the sodium source, aluminum source and template are weighed and dissolved in deionized water, mixed with the metal scandium ion solution, and stirred to form a mixture. The preparation process of the scandium-containing multi-level porous silica-alumina molecular sieve further includes step 4: subjecting the scandium-containing multi-level porous silica-alumina molecular sieve obtained in step 3 to ion exchange treatment to obtain the scandium-containing multi-level porous silica-alumina molecular sieve after ion exchange. The specific method of step 4 is: 4.1: Prepare ammonium chloride solution, the concentration of which is 2 g / L-4 g / L; 4.2: Weigh 1 g of the scandium-containing multi-stage molecular sieve obtained in step 3, place it in 50 mL of ammonium chloride solution using an 80°C oil bath, stir for 2 hours, and then wash the obtained molecular sieve with water; 4.3: The washed molecular sieve was dried at 60°C for 24 hours and then placed in a muffle furnace for calcination. The calcination process was to heat from room temperature (25°C) to 550°C for 6 hours at a heating rate of 1.458°C / min. The temperature was maintained at 550°C for 6 hours and then naturally cooled. 4.4: Repeat steps 4.1-4.3 2 to 5 times.

6. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 5, characterized in that: The method for preparing the scandium-containing multi-level porous silicon-aluminum molecular sieve with MFI microporous structure is as follows: I 1: Aluminum source, sodium source and template are added to water in sequence and stirred to obtain solution A; I 2: adding a scandium ion solution to the solution A, stirring and aging for 1-10 hours to obtain a mixture B; I 3: Add a silicon source to mixture B, and stir to obtain solution C, wherein the molar ratio of the components in solution C is SiO2:TPAOH:Al2O3:Na2O:H2O:Sc=50-150:1-100:1.25-100:0-100:10-5000:0.3-10; I4: placing solution C in a Teflon-lined metal reactor and hydrothermally crystallizing it at 90-190° C. for 48-120 hours; after the crystallization, filtering, washing, drying, and calcining are performed in sequence to obtain a scandium-containing multi-level porous silica-alumina molecular sieve Sc-MFI-5 with an MFI microporous structure; I5: subjecting the Sc-MFI-5 molecular sieve to ion exchange treatment at a temperature of 40° C. to 160° C. to obtain ion-exchanged Sc-ZSM-5.

7. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 5, characterized in that: The method for preparing the scandium-containing multi-level porous silicon-aluminum molecular sieve with a MOR microporous structure is as follows: R1: Weigh the aluminum source and sodium source and dissolve them in deionized water, stirring until completely dissolved to obtain solution D; R2: preparing a metal scandium ion solution, mixing it with the solution D, and adding the template dropwise, stirring and mixing until uniform, to form a solution E; R3: Add a silicon source dropwise to the solution E and stir to form a solution F, wherein the molar ratio of the substances in the solution F is SiO2:NaAlO2:NaOH:TEAOH:H2O:Sc(OH)3=1:0.01-0.4:0.01-0.5:0-1.0:1-100:0.01-0.5; R4: The solution F is placed in a reactor and subjected to hydrothermal crystallization at 170° C. for 72 hours. After the hydrothermal crystallization, the solution is filtered, washed, dried, and calcined, and then rinsed and dried to obtain a scandium-containing multi-level porous silicon-aluminum molecular sieve Sc-MOR with a MOR microporous structure. R5: performing ion exchange treatment on the Sc-MOR molecular sieve to obtain the ion-exchanged Sc-MOR molecular sieve.

8. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 5, characterized in that: The method for preparing the FAU microporous structured scandium-containing silicon-aluminum molecular sieve is as follows: F1: Weigh a sodium source and dissolve it in deionized water to obtain solution G; F2: Dissolve the scandium source and aluminum source in deionized water to form solution H; F3: Add silica and solution G to solution H under stirring, and continue stirring to form solution I, wherein the molar ratio of the components in solution I is SiO2:Na2O:Al2O3:H2O:Sc(OH)3=100:0.01-30:0.01-50:100-5000:0.1-25; F4: placing the solution I into a reactor and performing a hydrothermal crystallization treatment at a high temperature. After the hydrothermal treatment, the solution is filtered, washed, dried, and calcined, and then rinsed and dried to obtain a scandium-containing multi-level porous silicon-aluminum molecular sieve Sc-FAU with a FAU microporous structure; F5: performing ion exchange treatment on the Sc-FAU molecular sieve to obtain ion-exchanged Sc-FAU molecular sieve.

9. The method for preparing a scandium-containing multi-level porous silica-alumina molecular sieve according to claim 5, characterized in that: The preparation method of the Beta* structured scandium-containing silicon-aluminum molecular sieve is specifically as follows: T1: Weigh the sodium source and aluminum source, dissolve them in deionized water, mix and stir to obtain solution J; T2: preparing a metal scandium ion solution, mixing it with the solution J, and adding the template dropwise, stirring and mixing until uniform, to form a solution K; T3: adding a silicon source dropwise to the solution K, mixing and stirring to form a solution L, wherein the molar ratio of the components in the solution L is SiO2:Na2O:TEAOH:Al2O3:H2O:Sc(OH)3=100:0.01-40:0.01-100:0.01-50:100-8000:0.01-20; T4: placing the solution L into a reactor and subjecting it to hydrothermal crystallization at 170° C. for 72 hours. After the hydrothermal crystallization, filtering, washing, drying, and calcining are performed, followed by rinsing and drying to obtain a scandium-containing multi-level porous silica-alumina molecular sieve Sc-Beta with a Beta* structure; T5: performing ion exchange treatment on the Sc-Beta molecular sieve to obtain an ion-exchanged Sc-Beta molecular sieve.

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