SAPO-18-MeR molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses an SAPO-18-MeR molecular sieve as well as a preparation method and application thereof. The anhydrous chemical composition of the material is mMe. NR (Si < x > Al < y > P < z >) O < 2 >, me is selected from at least one of Li < + >, Na < + >, K < + > and NH4 < + >; r is selected from at least one of N, N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethidene diamine; m is the mole number of Me, and m is equal to 0.05 to 0.2; n is the mole number of R, and n is equal to 0.05-0.2; x is the mole fraction of Si, and x ranges from 0.05 to 0.35; y is the molar fraction of Al and is equal to 0.35 to 0.55; z is the molar fraction of P, z = 0.25-0.45, and x + y + z = 1. The molecular sieve has excellent silicon distribution and strong acid property, and has excellent catalytic performance as a denitration catalyst after loading Cu ions.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieves, and in particular relates to a SAPO-18-MeR molecular sieve and a preparation method and application thereof. Background Art

[0002] Silicoaluminophosphate (SAPO-n) molecular sieve is a type of microporous crystalline material (USP 4,440,871) developed by Union Carbide Corporation (UCC) in 1984. Its infinite open framework structure consists of [SiO4] 0 , [AlO4] - , [PO4] + Three tetrahedral units are connected by a certain symmetry common vertex. Si atoms isomorphously replace the P atoms in part of the neutral aluminum phosphate framework structure, so that the framework produces a net negative charge, introduces the B acid center, thereby giving the SAPO molecular sieve acid catalytic performance. It is generally believed that the acid properties of SAPO molecular sieves are weaker than silicon-aluminum molecular sieves, because the aluminum phosphate framework is more flexible than silicon-aluminum molecular sieves, and the tension generated after the silicon atom is introduced into the aluminum phosphate framework is not as large as the aluminum atom introduced into the silicon oxide framework (J.Phys.Chem.C 2011,115,22505-22513). However, in recent years, it has also been found that individual SAPO molecular sieves have strong acid properties comparable to silicon-aluminum molecular sieves (Journal of Physical Chemistry C, 2016,119 (5), 2589-2596).

[0003] SAPO molecular sieve synthesis generally adopts hydrothermal synthesis method, the reaction mixture usually uses water as solvent, and the synthesis raw materials include aluminum source, phosphorus source, silicon source and organic amine template. Organic amine template is very important for regulating the structure and acid properties of SAPO molecular sieve.

[0004] SAPO-18 is a silicoaluminophosphate molecular sieve with AEI topology. Its pore size is the same as SAPO-34. However, the arrangement of the double six-membered rings is different from that of the CHA structure, thus forming a pear-shaped nanoscale AEI cage. The silicon content of SAPO-18 is usually not high, and the silicon environment is more complex than that of SAPO-34. Even when the silicon content is less than 5%, SAPO-18 still has a rich Si(0Al) and Si(1Al) environment. It can be seen that silicon enters the SAPO-18 skeleton more by replacing both P and Al atoms at the same time (Industrial Catalysis, 2005, 8, 1-5). The presence of silicon islands weakens the acid properties of SAPO-18, which is not conducive to the catalytic reaction. In order to change the silicon environment of SAPO-18, an important way is to develop more new methods for synthesizing SAPO-18. The prior art discloses the use of cyclic quaternary ammoniums including N,N-dimethyl-3,5-dimethylpiperidine (DMDMP), N,N-diethyl-2,6-dimethylpiperidine (DEDMP), N,N-dimethyl-2,6-dimethylpiperidine, N-ethyl-N-methyl-2,6-dimethylpiperidine and combinations thereof to synthesize SAPO-18 molecular sieves; however, these organic amines are difficult to purchase and are not readily available. Summary of the invention

[0005] In view of this, the present invention provides a SAPO-18-MeR molecular sieve and a preparation method and application thereof, the main purpose of which is to solve the technical problem that the silicon environment in the silicoaluminophosphate molecular sieve SAPO-18 is complex, such as rich Si(0Al) and Si(1Al) environments, and the presence of silicon islands leads to weak acidity of the molecular sieve.

[0006] In one aspect, the present invention provides a SAPO-18-MeR molecular sieve, wherein the anhydrous chemical composition of the molecular sieve is:

[0007] mMe·nR(Si x Al y P z )O2 Formula I;

[0008] In formula I, Me is selected from Li + 、Na + , K + and NH4 + At least one of;

[0009] R is an organic template, selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethylenediamine;

[0010] m is mMe·nR(Si x Al y P z ) The number of moles of Me (monovalent cation) in O2, m = 0.05 ~ 0.2;

[0011] n is mMe·nR(Si x Al y P z ) The number of moles of R (template molecules) in O2, n = 0.05 to 0.2;

[0012] x is mMe·nR(Si x Al y P z ) The mole fraction of Si in O2, x = 0.05 to 0.35;

[0013] y is mMe·nR(Si x Al y P z ) The mole fraction of Al in O2, y = 0.35 ~ 0.55;

[0014] z is mMe·nR(Si x Al y P z )The mole fraction of P in O2, z=0.25~0.45, and x+y+z=1.

[0015] The molecular sieve of the present invention has an AEI topological structure and contains a monovalent inorganic cation Me and an organic template R at the same time; the molecular sieve has a relatively uniform and excellent silicon distribution, the negative charge of the skeleton is balanced by the monovalent cation and the protonated organic amine template, and the hydrogen-type molecular sieve obtained after ion exchange and calcination to remove the template has stronger acid properties.

[0016] Optionally, x in Formula I is selected from any value among 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, or any range therebetween.

[0017] Optionally, y in Formula I is selected from any value among 0.35, 0.40, 0.45, 0.50, 0.55, or any range between two thereof.

[0018] Optionally, z in Formula I is selected from any value among 0.25, 0.30, 0.35, 0.40, 0.45, or any range between two thereof.

[0019] Optionally, the SAPO-18-MeR molecular sieve has an AEI topological structure; the guest molecular metal ion Me and the organic template agent R are both distributed in the cage and double six-membered ring structure of the molecular sieve.

[0020] Optionally, the X-ray diffraction spectrum of the SAPO-18-MeR molecular sieve includes X-ray diffraction peaks at least at the positions shown in the following table:

[0021] No. 2θ / ° 1 9.58±0.1 2 10.67±0.1 3 12.95±0.1 4 13.53±0.1 5 16.08±0.1 6 17.00±0.1 7 17.28±0.1 .

[0022] Optionally, the SAPO-18-MeR molecular sieve has a single Si(4Al) environment (i.e., 4 Al atoms are connected to the silicon atom by 4 O atoms), and the molar content of silicon in the molecular sieve is greater than 5% (Si / (Si+Al+P)); i.e., x is (Si x Al y P z )The molar fraction of Si in O2, x = 0.05 ~ 0.35.

[0023] Optionally, the SAPO-18-MeR molecular sieve has a rhombus-shaped morphology and a particle size of 1 to 5 microns.

[0024] In a second aspect, the present invention provides a method for preparing the above-mentioned SAPO-18-MeR molecular sieve, the method comprising the following steps:

[0025] S1: Mix water, silicon source, aluminum source, phosphorus source and organic template R to form an initial gel;

[0026] S3: adding an inorganic salt / inorganic base Me to the initial gel to form a reaction gel;

[0027] S2: The reaction gel is heated to react and crystallize under closed conditions to obtain molecular sieve raw powder.

[0028] Optionally, in step S1, the molar ratio of water, silicon source, aluminum source, phosphorus source and organic template R in the initial mixed gel is:

[0029] SiO2 / Al2O3=0-1.5;

[0030] P2O5 / Al2O3=0.5-1.5;

[0031] H2O / Al2O3=20-200;

[0032] R / Al2O3=0.5-5;

[0033] Among them, the molar amount of water is calculated as the molar amount of its own H2O, the molar amount of the silicon source is calculated as the molar amount of SiO2, the molar amount of the aluminum source is calculated as the molar amount of Al2O3, the molar amount of the phosphorus source is calculated as P2O5, and the molar amount of the organic template is calculated as the molar amount of R.

[0034] The traditional technology in this field is to select organic amines to synthesize SAPO molecular sieves. Usually, acidic SAPO molecular sieves can be obtained by directly calcining to remove the organic template. However, due to the limitations of the skeleton structure and synthesis method of some molecular sieves, it is difficult to introduce silicon atoms into the neutral aluminum phosphate skeleton, which makes it easy for silicon islands to appear in the structure, resulting in weak acidity of the molecular sieve.

[0035] In order to solve the above technical problems, the inventors tried to synthesize high-silicon SAPO molecular sieves by combining organic templates with inorganic salts / bases, and achieved the synthesis of high-silicon SAPO-18 molecular sieves. Inorganic cations can be removed by subsequent simple ion exchange, thereby obtaining acidic properties.

[0036] The inventors have found that the synthesized SAPO-18 molecular sieve contains a monovalent inorganic cation Me and an organic template R, which will give the molecular sieve an excellent silicon distribution. The negative charge of the framework is balanced by the monovalent cation and the protonated organic amine template, which will cause the synthesized molecular sieve to have stronger acid properties. This technology also solves the problem of weak acidity of some SAPO molecular sieves in traditional technologies.

[0037] Optionally, the molar ratio of SiO2 / Al2O3 is selected from any value among 0, 0.1, 0.2, 0.3, 0.4, 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 therebetween.

[0038] Optionally, the molar ratio of P2O5 / Al2O3 is selected from any value among 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 therebetween.

[0039] Optionally, the molar ratio of H2O / Al2O3 is selected from any value among 20, 50, 80, 100, 120, 150, 180, 200 or any range therebetween.

[0040] Optionally, the molar ratio of R / Al2O3 is selected from any value among 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 or any range therebetween.

[0041] Optionally, the molar ratio of the inorganic salt / inorganic base Me to the template R is 0.01-1.

[0042] Optionally, the molar ratio of the inorganic salt / inorganic base Me to the template R is selected from any value among 0.01, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any range between two values.

[0043] Optionally, the organic template R is selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethylenediamine.

[0044] Optionally, the Me is selected from at least one of lithium salt, sodium salt, potassium salt and ammonium salt;

[0045] Optionally, the Me is selected from at least one of LiOH, NaOH, KOH and NH3·H2O.

[0046] Optionally, the Me is selected from at least one of LiCl, NaCl, KCl and NH4Cl.

[0047] The inorganic salt or inorganic base of the present invention can also be selected from other suitable inorganic salts or inorganic bases according to actual needs.

[0048] Optionally, the silicon source is selected from at least one of tetraethyl orthosilicate, low sodium silica sol and white carbon black; preferably, the phosphorus source is one or a mixture of tetraethyl orthosilicate and silica sol.

[0049] Optionally, the aluminum source is selected from at least one of pseudo-boehmite, aluminum hydroxide, aluminum isopropoxide, aluminum sec-butoxide and activated alumina; preferably, the aluminum source is one or a combination of two of pseudo-boehmite and aluminum isopropoxide.

[0050] Optionally, the phosphorus source is selected from at least one of orthophosphoric acid, phosphorous acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, organic phosphides and phosphorus oxides; preferably, the phosphorus source is one or more of orthophosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0051] Optionally, in step S3, the crystallization temperature is 130-220° C., and the crystallization time is 5-72 hours.

[0052] Optionally, the crystallization temperature is selected from any value among 130, 140, 150, 160, 170, 180, 190, 200, 210, 220 or any range between two values, in °C.

[0053] Optionally, the crystallization time is selected from any value of 5, 10, 20, 30, 40, 50, 60, 70, 72 hours or any range between two values, in hours.

[0054] In a third aspect, the present invention provides a catalyst for acid-catalyzed reaction, which is obtained by calcining the molecular sieve or the molecular sieve prepared by the above method in air at 400-800°C.

[0055] Optionally, the calcining temperature is selected from any value among 400, 500, 600, 700, 800 or any range between two values, in °C.

[0056] In a fourth aspect, the present invention provides a catalyst for the conversion of oxygen-containing compounds to olefins, which is obtained by calcining the above molecular sieve or the molecular sieve prepared by the above method in air at 400-800°C.

[0057] In a fifth aspect, the present invention provides a catalyst for ammonia selective reduction denitration reaction, wherein the molecular sieve or the molecular sieve prepared by the above method is first loaded with copper ions through copper ion exchange and then calcined in air at 400-800°C.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention provides a novel SAPO-18-MeR molecular sieve; the molecular sieve has an AEI topological structure and contains a monovalent inorganic cation Me and an organic template R; the molecular sieve has an excellent silicon distribution, and the negative charge of the skeleton is balanced by the monovalent cation and the protonated organic amine template, resulting in a stronger acid property. The molecular sieve of the present invention is used as a catalyst carrier and exhibits excellent performance in ammonia selective reduction denitration reaction after being loaded with Cu ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 The X-ray diffraction spectra of Example 4 and Comparative Example 1 of the present invention are shown in FIG.

[0061] Figure 2 This is a scanning electron microscope photograph of Example 4 of the present invention;

[0062] Figure 3 This is a scanning electron microscope photograph of Comparative Example 1 of the present invention;

[0063] Figure 4 For Example 4 of the present invention 29 Si solid NMR spectrum;

[0064] Figure 5 For comparative example 1 of the present invention 29 Si solid NMR spectrum;

[0065] Figure 6 This is a diagram of ammonia programmed temperature rise in Example 4 of the present invention;

[0066] Figure 7 NH3-TPD diagram of Comparative Example 1 of the present invention;

[0067] Figure 8 The NH3-selective catalytic reduction of NO in Example 4 of the present invention x(NH3-SCR) performance test results. DETAILED DESCRIPTION

[0068] The present application is further described below in conjunction with specific embodiments. The following are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application discloses the following preferred embodiments, they are not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the above disclosed technical content to make some changes or modifications are equivalent to equivalent implementation cases and are within the scope of the technical solution.

[0069] Unless otherwise specified, the raw materials in the examples of the present application were purchased from commercial sources and used directly without any special treatment.

[0070] The analysis method in the examples of this application is as follows:

[0071] X-ray powder diffraction phase analysis (XRD) was performed using an X'Pert PRO X-ray diffractometer from PANalytical of the Netherlands, with a Cu target, a Kα radiation source (λ=0.15418 nm), a voltage of 40 kV, and a current of 40 mA.

[0072] The instrument used for scanning electron microscopy (SEM) testing is Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2 kV.

[0073] The bulk element composition in the examples was determined using a Magix 2424 X-ray fluorescence analyzer (XRF) from Philips.

[0074] The samples were tested using a Bruker Avance III 600 (14.1 Tesla) spectrometer. 29 Si NMR spectrum.

[0075] The ammonia-temperature-programmed desorption curve was characterized on a micromeritics Autochem II 2920 chemical adsorption instrument. The operation steps are as follows: 200 mg of the calcined sample (40-60 mesh) was placed in a U-shaped tube, heated to 600 °C, pre-desorbed in a helium atmosphere for 60 minutes, then cooled, adsorbed NH3 at 100 °C for half an hour until adsorption saturation, purged with helium for 30 minutes, and then heated to 600 °C at 10 °C / min, and the desorption signal of NH3 was recorded using a TCD detector.

[0076] Example 1

[0077] a) Deionized water, silica sol, pseudo-boehmite, phosphoric acid and triethylamine are mixed in the following proportions to obtain an initial gel mixture having the following molar ratio:

[0078] SiO2 / Al2O3=0.4;

[0079] P2O5 / Al2O3=1.0;

[0080] H2O / Al2O3=50;

[0081] R / Al2O3=5.0;

[0082] b) adding a certain amount of inorganic salt NaCl to the initial gel obtained in step a);

[0083] The molar ratio of the added amount of inorganic salt (base) Me to the template agent is: Me / R=0.02;

[0084] c) placing the mixture prepared in b) into a stainless steel hydrothermal reactor, sealing it, raising the temperature to 160° C., and rotating and crystallizing it under autogenous pressure for 72 hours;

[0085] d) After the crystallization is complete, the solid product is centrifuged, washed, and dried to obtain the SAPO-18 molecular sieve.

[0086] Embodiments 2 to 8

[0087] The difference between Examples 2 to 8 and Example 1 is that the inorganic salts are different and the inorganic framework composition of the molecular sieve products is different, as shown in Table 1.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Example 1 is that the reaction gel does not contain inorganic salts or inorganic bases, and does not contain Me metal ions, as shown in Table 1.

[0090] Table 1. Chemical composition of SAPO-18-MeR molecular sieve a

[0091]

[0092] a TEA refers to triethylamine; DEA refers to diethylamine; TEAOH refers to tetraethylammonium hydroxide; DIEA refers to N,N'-diisopropylethylamine; N refers to NH4 + .

[0093] The physical phase, acid properties and composition of the 9 molecular sieve samples prepared in Examples 1 to 8 and Comparative Example 1 were analyzed:

[0094] The 9 samples prepared in Examples 1 to 8 and Comparative Example 1 were characterized by XRD powder diffraction. The results showed that all of them had characteristic diffraction peaks of SAPO-18, proving that they were AEI crystal phases. They had X-ray diffraction peaks at the positions shown below, as shown in Table 2.

[0095] Table 2. X-ray diffraction peaks of molecular sieves of Examples 1-8

[0096] No. 2θ / ° 1 9.58±0.1 2 10.67±0.1 3 12.95±0.1 4 13.53±0.1 5 16.08±0.1 6 17.00±0.1 7 17.28±0.1

[0097] Taking Example 4 as an example, the XRD diffraction spectrum of the obtained sample is as follows: Figure 1 The peak position and shape of the XRD spectrum of sample 2-7 are the same as those of Example 1, except that the peak intensity fluctuates by about 10%.

[0098] The XRD pattern of the sample of Comparative Example 1 is also shown in Figure 1 Below, the peak position and relative peak intensity are significantly different from those of the XRD of Example 4, which is mainly due to the introduction of inorganic base (salt) resulting in a difference in the symmetry of the product crystal phase.

[0099] XRF was used to analyze the inorganic composition of the 9 samples prepared in Examples 1 to 8 and Comparative Example 1. The results are shown in Table 1 (product inorganic skeleton composition (normalized results of silicon, phosphorus and aluminum after exchange into hydrogen-type molecular sieve)). The molar proportions of Al in Table 1 are all close to 0.5, indicating that the silicon substitution mechanism in the samples of the present invention is mainly Si replacing P, and the occurrence rate of silicon islands caused by simultaneous substitution of P and Al atoms is low.

[0100] The 9 samples prepared in Examples 1 to 8 and Comparative Example 1 were analyzed by SEM. The samples in Examples 1 to 8 all had a rhombus-like morphology and a particle size of about 1 to 5 μm.

[0101] Taking Example 4 as an example, its SEM photo is shown in Figure 2 Comparative Example 1 shows a long strip shape of conventional SAPO-18, and its SEM photo is shown in Figure 3 .

[0102] The samples of Example 4 were 29 Si solid NMR analysis, such as Figure 4 As shown, it is confirmed that the sample has a single Si(4Al) distribution. 29 Si solid NMR spectrum see Figure 5 As can be seen from the figure, the silicon environment is mainly composed of silicon islands. It can be seen that the introduction of a certain amount of inorganic cations in the synthesis process of Example 4 of the present invention plays an important role in improving the silicon distribution of SAPO-18 molecular sieve.

[0103] The samples were analyzed by ammonia-programmed temperature (NH3-TPD), and it was found that the samples of Examples 1-8 all showed two strong desorption peaks at around 200 and 460°C, indicating that the samples had strong acid properties.

[0104] Taking Example 4 as an example, its NH3-TPD spectrum is shown in Figure 6 The sample spectrum of Comparative Example 1 is shown in Figure 7 ; As can be seen from the figure, the NH3 desorption peak of the sample in Comparative Example 1 appears at a significantly lower temperature. The desorption peaks of the weak acid and strong acid sites appear at 180°C and 350°C, respectively, and the peak area of ​​the strong acid site is significantly smaller. Both samples have an AEI structure. From the comparison of the diffusion paths, the crystal size of Examples 1-8 is larger and the diffusion path may be longer, which eliminates the diffusion restriction effect of structural differences on NH3 desorption. Therefore, the lower desorption temperature and smaller desorption peak area of ​​the strong acid site peak of Comparative Example 1 show that it has significantly weaker acid properties than Examples 1-8.

[0105] Application Example 1 (NH3-SCR Catalytic Reaction)

[0106] First, add 5g of the molecular sieve sample prepared in Example 4 to 100g of 0.02mol / L copper acetate solution, perform ion exchange at 80°C for 5h, then centrifuge the sample and wash it with deionized water until it is neutral. After drying in an oven at 120°C, calcine it at 600°C for 5h. Further, press the calcined sample into tablets and sieve them, weigh 0.3g of 60 to 80 mesh sample and mix it with 1.9g of quartz sand (60 to 80 mesh), and load it into a fixed bed reactor. Activate with nitrogen at 600°C for 40min, then cool to 150°C to start the reaction, and test point by point; wait for 20min at each temperature point, and record the data after the reaction stabilizes. The test temperature range is 150-650°C;

[0107] The reaction raw gas is: NO: 500ppm, NH3: 500ppm, O2: 5%, H2O: 5%, N2 as the balance gas, gas flow rate 1000mL / min, corresponding to the space velocity of 300,000h -1 .

[0108] The reaction tail gas was analyzed by online FTIR using a Bruker Tensor 27 instrument. The CuO content in the sample was 2.5-3 wt%. The reaction results are shown in Figure 8 It can be seen that the sample has a wide active temperature window, and the activity with a conversion rate greater than 90% can be maintained from 200℃ to 500℃. The sample was aged at 800℃ for 16h, and the NH3-SCR evaluation was performed again using the same experimental conditions; the results showed that the catalytic activity of the sample remained good, and even showed an upward trend in the high temperature section, proving that the sample has excellent hydrothermal stability.

[0109] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A SAPO-18-MeR molecular sieve, characterized in that: The anhydrous chemical composition of the molecular sieve is: m Me·n R(Si x Al y P z )O₂ of formula I; In formula I, Me is selected from Li + 、Na + , K + and NH4 + At least one of; R is an organic template, selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethylenediamine; m is per mole (Si x Al y P z ) The number of moles of Me in O2, m = 0.05 to 0.2; n is per mole (Si x Al y P z ) The number of moles of R in O2, n = 0.05 to 0.2; x is (Si x Al y P z ) The mole fraction of Si in O2, x = 0.05 to 0.35; y is (Si x Al y P z ) The mole fraction of Al in O2, y = 0.35 ~ 0.55; z is (Si x Al y P z )The mole fraction of P in O2, z=0.25~0.45, and x+y+z=1.

2. A SAPO-18-MeR molecular sieve according to claim 1, characterized in that: The SAPO-18-MeR molecular sieve has an AEI topological structure; the metal ion Me and the organic template R are distributed in the cage and double six-membered ring structure of the molecular sieve; Preferably, the SAPO-18-MeR molecular sieve has a single Si(4Al) environment, and the molar content of silicon in the molecular sieve is greater than 5%; Preferably, the SAPO-18-MeR molecular sieve has a diamond-shaped block shape and a particle size of 1 to 5 microns.

3. A SAPO-18-MeR molecular sieve according to claim 1, characterized in that: The X-ray diffraction spectrum of the SAPO-18-MeR molecular sieve includes X-ray diffraction peaks at least at the positions shown in the following table:

4. The method for preparing a SAPO-18-MeR molecular sieve according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: S1: Mix water, silicon source, aluminum source, phosphorus source and organic template R to form an initial gel; S3: adding an inorganic salt / inorganic base Me to the initial gel to form a reaction gel; S2: The reaction gel is heated to react and crystallize under closed conditions to obtain molecular sieve raw powder.

5. The method for preparing a SAPO-18-MeR molecular sieve according to claim 4, characterized in that: In step S1, the molar ratio of water, silicon source, aluminum source, phosphorus source and organic template R in the initial mixed gel is: SiO2 / Al2O3=0-1.5; P2O5 / Al2O3=0.5-1.5; H2O / Al2O3=20-200; R / Al2O3=0.5-5; Wherein, the molar amount of water is calculated as the molar amount of H2O itself, the molar amount of the silicon source is calculated as the molar amount of SiO2, the molar amount of the aluminum source is calculated as the molar amount of Al2O3, the molar amount of the phosphorus source is calculated as P2O5, and the molar amount of the organic template is calculated as the molar amount of R; Preferably, the molar ratio of the inorganic salt / inorganic base Me to the template R is 0.01-1.

6. The method for preparing a SAPO-18-MeR molecular sieve according to claim 4, characterized in that: In step S1, the organic template R is selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethylenediamine.

7. The method for preparing a SAPO-18-MeR molecular sieve according to claim 4, characterized in that: The Me is selected from at least one of lithium salt, sodium salt, potassium salt and ammonium salt; Preferably, the Me is selected from at least one of LiOH, NaOH, KOH and NH3·H2O; Preferably, the Me is selected from at least one of LiCl, NaCl, KCl and NH4Cl.

8. The method for preparing a SAPO-18-MeR molecular sieve according to claim 4, characterized in that: In step S3, the crystallization temperature is 130-220° C., and the crystallization time is 5-72 hours.

9. A catalyst for acid-catalyzed reaction, characterized in that: The molecular sieve described in any one of claims 1 to 3 or the molecular sieve prepared by the method described in any one of claims 4 to 8 is obtained by calcining in air at 400 to 800°C.

10. A catalyst for acid-catalyzed reaction according to claim 9, characterized in that: The catalyst for the acid-catalyzed reaction includes a catalyst for the reaction of converting oxygen-containing compounds to olefins or a catalyst for the reaction of selective reduction of ammonia for denitration.

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