Nanosized high-silica saPO-17 molecular sieve, synthesis method and application thereof

Abstract

The application discloses a kind of nano high-silicon SAPO-17 molecular sieve and synthesis method and application thereof, belong to molecular sieve technical field.The application is synthesized nano SAPO-17 molecular sieve by introducing proper phosphorus source, aluminium source and template aqueous solution to ball-milling SAPO molecular sieve as precursor.The nano SAPO-17 molecular sieve is obtained after calcination SAPO-17 molecular sieve catalyst.The phosphosilicate molecular sieve SAPO-17 synthesized by the application can be used as acid catalytic reaction catalyst, such as methanol to olefins (MTO) catalyst;The application also discloses the application of SAPO-17 molecular sieve after loading Cu ion as denitration catalyst (NH3-SCR).

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, and in particular to a nano-high silica SAPO-17 molecular sieve, its synthesis method, and its application. Background Technology

[0002] SAPO-n molecular sieves, due to their diverse and regular molecular-scale pore structure, moderate to strong acidity, and good hydrothermal stability, have significant application value in gas adsorption, separation, and industrial catalysis. SAPO-17 is a type with three-dimensional microporous eight-membered ring channels. SAPO molecular sieves with ERI cage structure.

[0003] SAPO-17 molecular sieves are typically synthesized using a hydrothermal method. Template agents used include cyclohexylamine (J.Membr.Sci.2016,520,507) and the non-commercial template agent 1,1,6,6-tetramethyl-1,6-diazacyclododecane-1,6-diammonium hydroxide (TDDH) (Inorg.Chem.2022,61,8066).

[0004] The SAPO-17 molecular sieve synthesized using cyclohexylamine has a fine rod-like morphology with a crystal size of about 10 μm. When T zeolite is introduced as a seed crystal, the silicon content does not exceed 17%. When a large amount of silicon source is introduced, the product often contains a competing phase of SAPO-56, and the crystal morphology of SAPO-17 molecular sieve is difficult to control in one step.

[0005] SAPO-17 molecular sieves synthesized using TDDH exhibit a spherical morphology of nanoparticle stacking, with crystal sizes less than 1 μm and a maximum silicon content of 8%. Furthermore, TDDH is a non-commercially synthesized product from a laboratory setting, resulting in high synthesis costs for SAPO-17 molecular sieves and limiting their further applications. Summary of the Invention

[0006] In view of this, the present invention provides a nano-high silicon SAPO-17 molecular sieve, its synthesis method and application, the main purpose of which is to solve the technical problems of low silicon content, large crystal size and difficulty in controlling crystal morphology in SAPO-17 molecular sieve.

[0007] On one hand, the present invention provides a nano-high silica SAPO-17 molecular sieve, the anhydrous chemical composition of which is: mTMHDA·(Si x Al y P z O2;

[0008] Wherein, the TMDHA is N,N,N',N'-tetramethyl-1,6-hexanediamine;

[0009] m is per mole (Si) x Al y P z The number of moles of TMDHA in O2, m = 0.05–0.3;

[0010] x represents the mole fraction of Si, x = 0.15 to 0.35.

[0011] y represents the mole fraction of Al, y = 0.35 to 0.55.

[0012] z represents the mole fraction of P, z = 0.25 to 0.45, and x + y + z = 1.

[0013] Optionally, x is selected from any value of 0.15, 0.20, 0.25, 0.30, 0.35 or a range of values ​​between any two.

[0014] Optionally, y is selected from any value of 0.35, 0.40, 0.45, 0.50, 0.55 or a range of values ​​between any two.

[0015] Optionally, z is selected from any value of 0.20, 0.25, 0.30, 0.35, 0.40, 0.45 or a range of values ​​between any two.

[0016] Optionally, the TMDHA in the SAPO-17 molecular sieve is distributed in the molecular sieve cage; the SAPO-17 molecular sieve has a hexagonal prism shape, and the length of the hexagonal prism is 200-500 nm.

[0017] Optionally, the column length is selected from any value of 200, 250, 300, 350, 400, 450, 500 or a range between any two, in nm.

[0018] Optionally, the X-ray diffraction pattern of the SAPO-17 molecular sieve includes X-ray diffraction peaks at least at the positions shown in the table below:

[0019]

[0020]

[0021] The nano-high silica SAPO-17 molecular sieve containing N,N,N,N-tetramethyl-1,6-hexanediamine of the present invention has a hexagonal prism morphology with a prism length of 200-500 nm. As an acid catalyst, this molecular sieve exhibits excellent catalytic performance in the conversion of methanol or dimethyl ether to low-carbon olefins; as a catalyst support, it exhibits excellent performance in the selective reduction denitration reaction of ammonia after loading Cu ions.

[0022] Secondly, the present invention provides a method for preparing the above-mentioned nano-high silica SAPO-17 molecular sieve, comprising the following steps:

[0023] S1: Obtain a high-silica SAPO molecular sieve, wherein the high-silica SAPO molecular sieve is ball-milled to obtain a precursor Q;

[0024] S2: An aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, an aluminum source, a phosphorus source, and the precursor Q from step S1 are mixed to obtain an initial gel mixture;

[0025] S3: The initial gel mixture undergoes a hydrothermal reaction under sealed conditions. After complete crystallization, the product is separated, washed, and dried to obtain nano-high silica SAPO-17 molecular sieve.

[0026] Optionally, in step S1, the high-silica SAPO molecules are screened from SAPO-34, SAPO-56, or DNL-6.

[0027] Optionally, in step S2, the mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is 2% to 50%.

[0028] Optionally, the mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is selected from any value of 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% or any range between two; preferably 5% to 30%.

[0029] Optionally, in step S2, the molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5;

[0030] The phosphorus source is calculated as P2O5, and the aluminum source is calculated as Al2O3;

[0031] The mass ratio of the precursor Q to the total amount of the aluminum source and phosphorus source is 0.5 to 20.

[0032] The mass of the aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine and the precursor Q is 1 to 50.

[0033] Optionally, the molar ratio of the phosphorus source to the aluminum source is selected from any value of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any range between the two.

[0034] Optionally, the mass ratio of the precursor Q to the total amount of the aluminum source and the phosphorus source is selected from any value or a range between 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20%; preferably 1 to 10%.

[0035] Optionally, the mass of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution and the precursor Q is any value selected from 1, 5, 10, 15, 20, 25, 30, 35, 40, 50 or any range between the two; preferably 5 to 20.

[0036] Optionally, in step S3, the hydrothermal reaction temperature is 130–220°C, and crystallization is carried out under autogenous pressure for 5–72 hours.

[0037] Optionally, the temperature of the hydrothermal reaction is selected from any value or a range between 130, 140, 150, 160, 170, 180, 190, 200, 210, and 220°C; preferably 140-220°C, and more preferably 160-200°C.

[0038] Optionally, the crystallization time is selected from any value or a range between any two of 5, 7, 10, 13, 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70, and 72 hours; preferably 7 to 36 hours.

[0039] Optionally, in step S2, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide, and boehmite.

[0040] Optionally, in step S2, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, diethyl trichloromethylphosphonate, and phosphorus-containing oxides.

[0041] Optionally, in step S1, the ball milling process includes: dispersing high-silica SAPO molecular sieves, after calcination to remove organic template agents, in water, and then rotating and ball milling them in a ball mill to obtain a slurry, which is then dried to obtain the solid precursor Q.

[0042] Optionally, in step S3, the crystallization process is carried out under static or dynamic conditions.

[0043] Thirdly, the present invention provides a nanoscale catalyst. The product obtained by calcining the above-mentioned nano-high silica SAPO-17 molecular sieve or the nano-high silica SAPO-17 molecular sieve prepared by the above preparation method in air at 400-800°C is the nanoscale catalyst.

[0044] Fourthly, the present invention provides a catalyst for the conversion of oxygen-containing compounds into olefins. The product obtained by calcining the above-mentioned nano-high silica SAPO-17 molecular sieve or the nano-high silica SAPO-17 molecular sieve prepared by the above preparation method in air at 400-800°C is the nano-catalyst.

[0045] Fifthly, the present invention provides a catalyst for ammonia selective reduction denitrification reaction. The nano-high silica SAPO-17 molecular sieve or the nano-high silica SAPO-17 molecular sieve prepared by the above preparation method is first subjected to copper ion exchange loading and then calcined in air at 400-800°C to obtain the product, which is the nano-catalyst.

[0046] In a sixth aspect, the present invention provides the application of the above-mentioned high-silica SAPO-17 molecular sieve or the high-silica SAPO-17 molecular sieve or the above-mentioned nanocatalyst in the conversion of oxygen-containing compounds to olefins or in the selective reduction denitration reaction of ammonia.

[0047] In a seventh aspect, the present invention provides a method for producing olefins from methanol, the method comprising: calcining a catalyst and then loading it into a reactor and activating it with nitrogen gas at 500-600°C; and reacting methanol at 400-500°C to produce olefins; wherein the catalyst is the aforementioned nanoscale catalyst.

[0048] Eighthly, the present invention provides a method for an NH3-SCR catalytic reaction, comprising: exchanging a molecular sieve with copper ions, followed by calcination at 550–650°C for 2–6 h to obtain a catalyst; loading the catalyst into a reactor and activating it by passing a reaction feed gas through it at 550–650°C for 30 min, then cooling it to 110–150°C and testing it point by point. At each temperature point, wait 20 min until the reaction stabilizes, and then record the data; the test temperature range is 150–650°C.

[0049] The composition of the reaction feed gas includes: NO: 500 ppm, NH3: 500 ppm, O2: 5%, H2O: 5%, with N2 as the balance gas. The gas flow rate is 1000 mL / min, corresponding to a space velocity of 180,000 h⁻¹. -1 ;

[0050] The molecular sieve is the above-mentioned nano-high silica SAPO-17 molecular sieve or the nano-high silica SAPO-17 molecular sieve prepared by the above preparation method.

[0051] Compared with the prior art, the present invention has the following technical effects:

[0052] (1) The method of the present invention uses an inexpensive organic template agent to synthesize nanoscale high silicon content SAPO-17 molecular sieves. The crystals exhibit a hexagonal prism morphology and the particle size is about 200nm to 500nm.

[0053] (2) The SAPO-17 molecular sieve prepared in this invention exhibits excellent catalytic performance in the conversion of methanol or dimethyl ether into low-carbon olefins.

[0054] (3) The SAPO-17 molecular sieve prepared in this invention in DeNOx x It exhibits excellent catalytic performance in catalytic selective reduction denitrification. Attached Figure Description

[0055] Figure 1 The X-ray diffraction pattern of the SAPO-17 sample prepared in Example 1 of this invention;

[0056] Figure 2 The SAPO-17 sample prepared in Example 2 of this invention underwent selective catalytic reduction of NO by NH3-. x (NH3-SCR) performance test result curve;

[0057] Figure 3 The SAPO-17 sample prepared in Example 1 of this invention 13 C solid NMR spectrum. Detailed Implementation

[0058] The present invention is further illustrated below with reference to embodiments, but the present invention is not limited to these embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise specified, the raw materials used in this application are all purchased commercially and used directly without special treatment.

[0059] The analysis method in the embodiments of this application is as follows:

[0060] X-ray powder diffraction (XRD) phase analysis was performed using an X'Pert PRO X-ray diffractometer from PANalytical, Netherlands, with a Cu target, Kα radiation source (λ = 0.15418 nm), voltage 40 kV, and current 40 mA.

[0061] The scanning electron microscope (SEM) used for testing was a Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2kV.

[0062] In the examples, the bulk elemental composition was determined using a Philips Magix 2424 X-ray fluorescence analyzer (XRF).

[0063] The samples were tested using a Bruker Avance III 600 (14.1 Tesla) spectrometer. 13 C and 29 Si solid-state NMR.

[0064] Examples 1-7 (Synthesis of SAPO-17 molecular sieves)

[0065] (1) The preparation method of precursor Q used in Examples 1-7 is as follows: 5g of high-silica SAPO molecular sieve that has been calcined to remove the organic template agent is evenly dispersed in 20g of water, placed in a ball mill, balanced with agate balls, and then ball-milled at high speed at 500Hz for 5h. The sauce is then collected, placed in an oven to dry and collect the solid, which is used as precursor Q for later use.

[0066] (2) Prepare an aqueous solution of N,N,N,N-tetramethyl-1,6-hexanediamine (R) of a certain concentration, and add a certain amount of precursor Q, phosphorus source and aluminum source to it in sequence. After stirring evenly at room temperature, transfer the gel to a stainless steel reactor. After placing the reactor in an oven, heat it to 140-220℃ and react for a certain time. Then cool it down to complete the crystallization. Centrifuge the solid product, wash it, and dry it in air at 120℃ to obtain the molecular sieve powder sample. The specific synthesis method and results are shown in Table 1.

[0067] Table 1. Synthesis conditions and results of SAPO-17 molecular sieve

[0068]

[0069] Phase, morphology and composition analysis were performed on the seven samples prepared in Examples 1 to 7:

[0070] The samples from Examples 1-7 were characterized by XRD powder diffraction, and the results showed that all samples exhibited characteristic diffraction peaks of SAPO-17, confirming that they are ERI crystalline phases. Taking Example 1 as an example, the XRD diffraction pattern of the obtained sample is shown below. Figure 1 As shown. The peak positions and shapes of the XRD spectra of samples 2-7 are the same as those in Example 1, except that there is a fluctuation of about 10% in peak intensity.

[0071] Table 2. X-ray diffraction peak data of SAPO-17-1 in Example 1

[0072] 1 7.69 2 9.73 3 11.81 4 13.32 5 15.70 6 16.66 7 19.05 8 19.53 9 20.71 10 21.48 11 23.81 12 24.68

[0073] Inorganic composition analysis was performed on samples 1–7 using XRF. The results are shown in Table 1, where the product composition columns are as follows: Al 0.47 Si 0.16 P 0.37 O2, Al 0.46 Si0.20 P 0.34 O2, Al 0.49 Si 0.25 P 0.26 O2, Al 0.46 Si 0.18 P 0.36 O2, Al 0.49 Si 0.15 P 0.36 O2, Al 0.49 Si 0.18 P 0.33 O2, Al 0.50 Si 0.15 P 0.35 O2. Silicon content is above 15%.

[0074] SEM was used to analyze the synthesized samples 1-7. All samples had a hexagonal prism morphology with a prism length of 200-500 nm.

[0075] Samples from Examples 1-7 were tested. 13 1CMAS NMR solid-state nuclear magnetic resonance analysis, such as Figure 3 As shown, the characteristic peaks of N,N,N',N'-tetramethyl-1,6-hexanediamine are indeed present in the sample.

[0076] Application Example 1 (MTO Catalytic Reaction)

[0077] The SAPO-17-5 molecular sieve prepared in Example 5 was first pressed into tablets and crushed to 20-40 mesh, then calcined at 600°C with air for 4 hours. 0.3 g of this sample was then loaded into a self-made fixed-bed reactor (a quartz tube) as a catalyst for MTO reaction evaluation. The reactor was activated at 550°C with nitrogen for 1 hour, and then cooled to 450°C for the reaction. Methanol was carried by nitrogen gas at a methanol space velocity (MSH) of 1 h⁻¹. -1 The reaction products were analyzed by online gas chromatography (Agilent A7890) using a PoraPlot-Q-HT column, and the results are shown in Table 3.

[0078] Table 3. MTO catalytic performance of the synthesized samples a

[0079]

[0080] a Reaction conditions: 450℃, methanol space velocity 1h -1 Lifetime is defined as the length of time during which methanol conversion is greater than 99%, and selectivity is given when the selectivity of ethylene plus propylene is highest.

[0081] Application Example 2 (NH3-SCR Catalytic Reaction)

[0082] First, 5g of the SAPO-17-2 molecular sieve prepared in Example 2 was added to 100g of 0.02mol / L copper acetate solution, and ion exchange was performed at 80℃ for 5h. The sample was then centrifuged and washed with deionized water until neutral. After drying in a 120℃ oven, it was calcined at 600℃ for 5h. The calcined sample was further pressed into tablets and sieved. 0.3g of a 60-80 mesh sample was weighed and mixed with 1.9g of quartz sand (60-80 mesh), and loaded into a fixed-bed reactor. Nitrogen gas was purged at 600℃ for 40min, and then the temperature was lowered to 150℃ to begin the reaction. Tests were performed point by point; each temperature point was waited for 20min until the reaction stabilized, and data were recorded. The test temperature range was 150-650℃.

[0083] The reactant gases are: NO: 500 ppm, NH3: 500 ppm, O2: 5%, H2O: 5%, with N2 as the equilibrium gas. The gas flow rate is 1000 mL / min, corresponding to a space velocity of 180,000 h⁻¹. -1 .

[0084] The reaction tail gas was analyzed online using a Bruker Tensor 27 instrument. The Cu content in the sample was 3 wt%. The reaction results are shown in [Figure number missing]. Figure 2 It can be seen that the sample has a wide active temperature window and good hydrothermal stability.

[0085] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A nanosized high-silica SAPO-17 molecular sieve characterized in that, The anhydrous chemical composition of the SAPO-17 molecular sieve is: m TMHDA · (Si x Al y P z )O2; wherein m is a mole ratio in the range of 0.01 to 0.2; and TMHDA is a tetramethylhexamethylenediamine. Wherein, the TMDHA is N,N,N',N'-tetramethyl-1,6-hexanediamine; m is the number of moles of TMHDA per mole of (Si x Al y P z )O2, m = 0.05 ~ 0.3; x represents the mole fraction of Si, x = 0.15~0.

35. y represents the mole fraction of Al, y = 0.35 ~ 0.

55. z represents the mole fraction of P, z = 0.25~0.45, and x+y+z = 1; The TMDHA in the SAPO-17 molecular sieve is distributed in the molecular sieve cage; the SAPO-17 molecular sieve has a hexagonal prism shape, and the length of the hexagonal prism is 200~500 nm. The SAPO-17 molecular sieve is prepared by a method comprising the following steps: S1: Obtain a high-silica SAPO molecular sieve, wherein the high-silica SAPO molecular sieve is ball-milled to obtain a precursor Q; The high-silicon SAPO molecules are screened from SAPO-34, SAPO-56, or DNL-6; S2: An aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, an aluminum source, a phosphorus source, and the precursor Q from step S1 are mixed to obtain an initial gel mixture; The aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine has a mass percentage content of 2% to 50%. The molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5; The phosphorus source is calculated as P2O5, and the aluminum source is calculated as Al2O3; The mass ratio of the precursor Q to the total amount of the aluminum source and phosphorus source is 0.5~20; The mass ratio of the aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine to the precursor Q is 1~50; S3: The initial gel mixture undergoes a hydrothermal reaction under sealed conditions. After complete crystallization, the product is separated, washed, and dried to obtain the nano-high silica SAPO-17 molecular sieve.

2. The nano-high silica SAPO-17 molecular sieve according to claim 1, characterized in that, The X-ray diffraction pattern of the SAPO-17 molecular sieve includes X-ray diffraction peaks at at least the positions shown in the table below: 。 3. The method for preparing a nano-high silica SAPO-17 molecular sieve according to claims 1-2, characterized in that, The preparation method includes the following steps: S1: Obtain a high-silica SAPO molecular sieve, wherein the high-silica SAPO molecular sieve is ball-milled to obtain a precursor Q; The high-silicon SAPO molecules are screened from SAPO-34, SAPO-56, or DNL-6; S2: An aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, an aluminum source, a phosphorus source, and the precursor Q from step S1 are mixed to obtain an initial gel mixture; The aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine has a mass percentage content of 2% to 50%. The molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5; The phosphorus source is calculated as P2O5, and the aluminum source is calculated as Al2O3; The mass ratio of the precursor Q to the total amount of the aluminum source and phosphorus source is 0.5~20; The mass ratio of the aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine to the precursor Q is 1~50; S3: The initial gel mixture undergoes a hydrothermal reaction under sealed conditions. After complete crystallization, the product is separated, washed, and dried to obtain nano-high silica SAPO-17 molecular sieve. The hydrothermal reaction is carried out at a temperature of 130~220℃, and crystallization is carried out under autogenous pressure for 5~72 hours. In step S2, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide, and boehmite. The phosphorus source is selected from at least one of orthophosphoric acid, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, diethyl trichloromethylphosphonate, and phosphorus-containing oxides. In step S1, the ball milling process includes: dispersing high-silica SAPO molecular sieves, after calcination to remove organic template agents, in water, and then rotating and ball milling them in a ball mill to obtain a slurry; the slurry is then dried to obtain the solid precursor Q. In step S3, the crystallization process is carried out under static or dynamic conditions.

4. A nanoscale catalyst, characterized in that, The nano-high silica SAPO-17 molecular sieve according to any one of claims 1 to 2 or the nano-high silica SAPO-17 molecular sieve prepared by the preparation method according to claim 3, after being calcined in air at 400 to 800°C, yields the nano-scale catalyst.

5. The application of the nano-high silica SAPO-17 molecular sieve according to any one of claims 1 to 2, or the nano-high silica SAPO-17 molecular sieve prepared by the preparation method according to claim 3, or the nano-scale catalyst according to claim 4, in the reaction of oxygen-containing compounds to olefins or in the selective reduction denitration reaction of ammonia.

6. A method for producing olefins from methanol, characterized in that, The method includes: calcining the catalyst and then loading it into a reactor and activating it with nitrogen gas at 500-600°C; and reacting methanol at a reaction temperature of 400-500°C to generate olefins; the catalyst is the nanoscale catalyst described in claim 4.

7. A method for an NH3-SCR catalytic reaction, characterized in that, The method includes: the molecular sieve undergoes copper ion exchange, and then is calcined at 550~650℃ for 2-6 h to obtain a catalyst; the catalyst is loaded into a reactor and activated by passing a reaction raw material gas through it at 550~650℃ for 30 min, then cooled to 110~150℃, and tested point by point; at each temperature point, wait for 20 min until the reaction stabilizes, and record the data. The test temperature range is 150~650℃. The reaction raw gas composition includes: NO: 500 ppm, NH3: 500 ppm, O2: 5%, H2O: 5%, N2 as a balance gas, a gas flow rate is 1000 mL / min, and a corresponding space velocity is 180000 h -1 ; The molecular sieve is the nano high-silica SAPO-17 molecular sieve according to any one of claims 1 to 2 or the nano high-silica SAPO-17 molecular sieve prepared by the preparation method according to claim 3.

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