A saPO-18-meR molecular sieve, a preparation method and application thereof

Abstract

The application discloses SAPO-18-MeR molecular sieve and a preparation method and application thereof. The anhydrous chemical composition of the molecular sieve is mMe*nR(Si x Al y P z )O2; Me is at least one selected from Li + , Na + , K + and NH4 + ; R is at least one selected from N, N-diisopropyl ethylamine, tetraethyl ammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethylenediamine; m is the mole number of Me, m=0.05-0.2; n is the mole number of R, n=0.05-0.2; x is the mole fraction of Si, x=0.05-0.35; y is the mole fraction of Al, y=0.35-0.55; z is the mole 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 present application belongs to the technical field of molecular sieve, and particularly relates to a SAPO-18-MeR molecular sieve, a preparation method and application thereof. BACKGROUND

[0002] Phosphorous silicoaluminate (SAPO-n) molecular sieve is a kind of microporous crystalline material developed by UCC in 1984 (USP 4,440,871). Its infinite open framework structure is composed of three kinds of tetrahedral units, [SiO4] 0 , [AlO4] - and [PO4] + , which are connected by sharing vertices according to certain symmetry. Si atoms isomorphously substituted for part of P atoms in the neutral aluminophosphate framework structure, resulting in a net negative charge of the framework and introducing B acid centers, thus endowing SAPO molecular sieve with acid catalytic properties. It is generally believed that the acidity of SAPO molecular sieve is weaker than that of silicoaluminate molecular sieve, because the flexibility of aluminophosphate framework is better than that of silicoaluminate molecular sieve, and the tension produced by introducing Si atoms into the aluminophosphate framework is smaller than that of introducing Al atoms into the silica framework (J. Phys. Chem. C 2011, 115, 22505-22513). However, in recent years, it has been found that individual SAPO molecular sieves have strong acidity comparable to that of silicoaluminate molecular sieves (Journal of Physical Chemistry C, 2016, 119(5), 2589-2596).

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

[0004] SAPO-18 is a kind of phosphorous silicoaluminate molecular sieve with AEI topology structure. Its pore size is the same as that of SAPO-34, both of which are However, the arrangement of the double six-membered rings is different from that of the CHA structure, thus forming the AEI cage with a nanoscale size in the shape of a pear. The silicon content of SAPO-18 is generally not high, and the silicon environment is more complex than that in SAPO-34. Even if the silicon content is less than 5%, there are still abundant Si(0Al) and Si(1Al) environments in SAPO-18. It can be seen that the silicon enters the SAPO-18 framework more in the manner of simultaneously replacing P and Al atoms (Industrial Catalysis, 2005, 8, 1-5). The existence of silicon islands makes the acidity of SAPO-18 weak, 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 that cyclic quaternary ammonium 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 are used to synthesize SAPO-18 molecular sieves; however, these organic amines are difficult to purchase and obtain. SUMMARY

[0005] Therefore, the present application provides a SAPO-18-MeR molecular sieve, a preparation method and application thereof, and mainly aims to solve the technical problem that the silicon environment of the phosphosilicate molecular sieve SAPO-18 is complex, such as abundant Si(0Al) and Si(1Al) environments, and the existence of silicon islands leads to weak acidity of the molecular sieve.

[0006] In one aspect, the present application provides a SAPO-18-MeR molecular sieve, and the anhydrous chemical composition of the molecular sieve is as follows:

[0007] m Me·n R(Si x Al y P z )O2 formula I;

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

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

[0010] m is the number of moles of Me (monovalent cation) in each mole of m Me·n R(Si x Al y P z )O2, and m = 0.05-0.2;

[0011] n is the number of moles of R (template molecule) in m Me·n R(Si x Al y P z )O2, n = 0.05-0.2;

[0012] x is the mole fraction of Si in m Me·n R(Si x Al y P z )O2, x = 0.05-0.35;

[0013] y is the mole fraction of Al in m Me·n R(Si x Al y P z )O2, y = 0.35-0.55;

[0014] z is the mole fraction of P in m Me·n R(Si x Al y P z )O2, z = 0.25-0.45, and x + y + z = 1.

[0015] The above-mentioned molecular sieve of the present application has AEI topology and contains monovalent inorganic cation Me and organic template R at the same time; the molecular sieve has relatively uniform and excellent silicon distribution, the framework negative charge is balanced by monovalent cation and protonated organic amine template, and the hydrogen type molecular sieve obtained after ion exchange and template removal by calcination has stronger acid properties.

[0016] Optionally, x in formula I is selected from any value or a range value between any two of 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35.

[0017] Optionally, y in formula I is selected from any value or a range value between any two of 0.35, 0.40, 0.45, 0.50, 0.55.

[0018] Optionally, z in formula I is selected from any value or a range value between any two of 0.25, 0.30, 0.35, 0.40, 0.45.

[0019] Optionally, the SAPO-18-MeR molecular sieve has AEI topology; both the guest molecule metal ion Me and the organic template R are 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. a silicon atom is connected to four Al atoms through four 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 )O2, x = 0.05-0.35.

[0023] Optionally, the SAPO-18-MeR molecular sieve has a rhombic square shape, and the particle size is 1-5 microns.

[0024] In a second aspect, the present application provides a preparation method of the above-mentioned SAPO-18-MeR molecular sieve, which comprises the following steps:

[0025] S1: mixing water, a silicon source, an aluminum source, a phosphorus source and an 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: heating and reacting the reaction gel under a closed condition to crystallize, thereby obtaining a molecular sieve raw powder.

[0028] Optionally, in step S1, the molar ratio of water, the silicon source, the aluminum source, the phosphorus source and the 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] wherein the molar amount of water is calculated based on the molar amount of H2O itself, the molar amount of the silicon source is calculated based on the molar amount of SiO2, the molar amount of the aluminum source is calculated based on the molar amount of Al2O3, the molar amount of the phosphorus source is calculated based on P2O5, and the molar amount of the organic template is calculated based on the molar amount of R.

[0034] The conventional technology in the art is to select an organic amine to synthesize the SAPO molecular sieve, and the acidic SAPO molecular sieve can be obtained by directly calcining to remove the organic template. However, due to the limitation of the framework structure and the synthesis method, it is difficult to introduce silicon atoms into the neutral aluminum phosphate framework, resulting in the easy occurrence of silicon islands in the structure, and the weak acidity of the molecular sieve.

[0035] In order to solve the above technical problems, the present inventors attempt to use the combination of an organic template and an inorganic salt / alkali to synthesize a high-silicon SAPO molecular sieve, and realize the synthesis of a high-silicon SAPO-18 molecular sieve. The inorganic cations can be removed by subsequent simple ion exchange, so as to obtain acidic properties.

[0036] The present inventors find that the synthesized SAPO-18 molecular sieve contains monovalent inorganic cations Me and an organic template R, which makes the molecular sieve have excellent silicon distribution, and the framework negative charge is balanced by the monovalent cations and the protonated organic amine template, which also leads to the synthesized molecular sieve having stronger acidic properties. The technology also solves the problem of weak acidity of some SAPO molecular sieves in the conventional technology.

[0037] Optionally, the molar ratio of SiO2 / Al2O3 is selected from any value or a range value between any two of 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.

[0038] Optionally, the molar ratio of P2O5 / Al2O3 is selected from any value or a range value between any two of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5.

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

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

[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 or a range value between any two of 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.

[0043] Optionally, the organic template agent 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 application can also select other suitable inorganic salt or inorganic base 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 uses a mixture of one or both of tetraethyl orthosilicate and silica sol.

[0049] Optionally, the aluminum source is selected from at least one of pseudoboehmite, aluminum hydroxide, aluminum isopropylate, aluminum sec-butoxide and active alumina; preferably, the aluminum source uses a combination of one or both of pseudoboehmite and aluminum isopropylate.

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

[0051] Optionally, in step S3, the temperature of the crystallization is 130-220℃, and the time of the crystallization is 5-72h.

[0052] Optionally, the temperature of the crystallization is selected from any value or a range value between any two values of 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, unit ℃.

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

[0054] In a third aspect, the present application provides a catalyst for acid catalytic reaction, wherein the molecular sieve is obtained by calcining the above-mentioned molecular sieve or the molecular sieve prepared by the above-mentioned method at 400-800℃ in air.

[0055] Optionally, the temperature of the calcination is selected from any value of 400, 500, 600, 700, 800 or a range between any two of them, unit ℃.

[0056] In a fourth aspect, the present application provides a catalyst for the conversion of oxygenates to olefins, wherein the molecular sieve is obtained by calcining the molecular sieve of the above-mentioned method or the above-mentioned molecular sieve at 400-800℃ in air.

[0057] In a fifth aspect, the present application provides a catalyst for the selective catalytic reduction of NOx by NH3, wherein the molecular sieve is obtained by calcining the molecular sieve of the above-mentioned method or the above-mentioned molecular sieve at 400-800℃ in air after loading copper ions.

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

[0059] The present application provides a novel SAPO-18-MeR molecular sieve; the molecular sieve has AEI topology and contains monovalent inorganic cations Me and organic templates R; the molecular sieve has excellent silicon distribution, and the framework negative charge is balanced by monovalent cations and protonated organic amine templates, resulting in stronger acid properties. The molecular sieve of the present application as a catalyst carrier, after loading Cu ions, exhibits excellent performance in the selective catalytic reduction of NOx by NH3. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 X-ray diffraction spectrum of Example 4 and Comparative Example 1 of the present application;

[0061] Figure 2 Scanning electron microscope photograph of Example 4 of the present application;

[0062] Figure 3 Scanning electron microscope photograph of Comparative Example 1 of the present application;

[0063] Figure 4 Si solid-state nuclear magnetic resonance spectrum of Example 4 of the present application; 29 Si solid-state nuclear magnetic resonance spectrum of Example 4 of the present application;

[0064] Figure 5 Si solid-state nuclear magnetic resonance spectrum of Comparative Example 1 of the present application; 29 Si solid-state nuclear magnetic resonance spectrum of Comparative Example 1 of the present application;

[0065] Figure 6 NH3-TPD graph of Example 4 of the present application;

[0066] Figure 7 NH3-TPD graph of Comparative Example 1 of the present application;

[0067] Figure 8 NH3-selective catalytic reduction of NOx by Example 4 of the present application; x(NH3-SCR) performance test results. DETAILED DESCRIPTION

[0068] The present application is further described in conjunction with the following examples. The following examples are intended to illustrate the present application and are not intended to limit the present application in any way. Although the present application has been disclosed with reference to the preferred embodiments, it is to be understood that certain changes can be made in form and detail without departing from the spirit and scope of the application. Any skilled person in the art, without departing from the technical scope of the present application, can make some changes or modifications to the above-mentioned disclosed technical contents, which are equivalent to the equivalent embodiments, and all of them are within the scope of the technical solutions.

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

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

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

[0072] The scanning electron microscope (SEM) used for testing is a Hitachi SU8020 field emission scanning electron microscope, and the acceleration voltage is 2 kV.

[0073] In the examples, the determination of the bulk element composition is determined by using a Magix 2424X ray fluorescence analyzer (XRF) of Philips company.

[0074] The samples are tested by using a Bruker Avance III 600 type (14.1 Tesla) spectrometer. 29 Si nuclear magnetic resonance spectrum.

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

[0076] Example 1

[0077] a) mixing deionized water, silica sol, pseudoboehmite, phosphoric acid and triethylamine in the following proportions to obtain an initial gel mixture having the following molar ratios:

[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 amount of inorganic salt (base) Me added is in a molar ratio of Me / R = 0.02 to the template agent;

[0084] c) loading the mixture prepared in b) into a stainless steel hydrothermal reactor, sealing, heating to 160°C, rotating under autogenous pressure for 72 hours for crystallization;

[0085] d) after the crystallization is completed, centrifuging, washing and drying the solid product to obtain the SAPO-18 molecular sieve.

[0086] Examples 2-8

[0087] Examples 2-8 differ from Example 1 in that the inorganic salts are different, and the inorganic framework compositions of the molecular sieve products are different, as shown in Table 1.

[0088] Comparative Example 1

[0089] Comparative Example 1 differs from Example 1 in 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 sieves 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 nine molecular sieve samples prepared in Examples 1-8 and Comparative Example 1 were subjected to phase, acid property and composition analysis:

[0094] The nine samples prepared in Examples 1-8 and Comparative Example 1 were characterized by XRD powder diffraction, and 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 the 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] The XRD diffraction spectrum of the sample obtained in Example 4 is shown in Figure 1 The peak positions and shapes of the XRD spectra of Samples 2-7 were the same as those of Example 1, only with fluctuations of about 10% in peak intensity.

[0098] The XRD spectrum of the sample of Comparative Example 1 is also shown below, and its peak positions and relative peak intensities were obviously different from those of Example 4, which was mainly due to the difference in symmetry of the crystal phase of the product caused by the introduction of inorganic bases (salts). Figure 1

[0099] The inorganic compositions of the nine samples obtained in Examples 1-8 and Comparative Example 1 were analyzed by XRF, and the results are shown in Table 1 (inorganic framework composition of the products (normalized results of silicon, phosphorus and aluminum after being exchanged into hydrogen type molecular sieves)), in which the molar percentage of Al was close to 0.5, indicating that the silicon substitution mechanism in the sample of the present application was mainly Si substitution for P, and the occurrence rate of the phenomenon of simultaneous substitution of P and Al atoms to form silicon islands was low.

[0100] The nine samples obtained in Examples 1-8 and Comparative Example 1 were analyzed by SEM, and the samples of Examples 1-8 all showed rhombohedral shapes with particle sizes of about 1-5 microns.

[0101] Taking Example 4 as an example, its SEM photograph is shown in Figure 2 , and Comparative Example 1 showed the conventional long strip morphology of SAPO-18, and its SEM photograph is shown in Figure 3 .

[0102] The sample of Example 4 was subjected to 29 Si solid-state nuclear magnetic analysis, as shown in Figure 4 , which confirmed that the sample had a single Si(4Al) distribution. The 29 Si solid-state nuclear magnetic spectrum of Comparative Example 1 is shown in Figure 5 , from which it can be seen that the silicon environment is mainly in the form of silicon islands. It can be seen that the introduction of a certain amount of inorganic cations in the synthesis process of Example 4 plays an important role in improving the silicon distribution of SAPO-18 molecular sieves.

[0103] ​The samples were analyzed by NH3-TPD, and it was found that the samples of Examples 1-8 all had two strong desorption peaks near 200 and 460℃, indicating that the samples had strong acidic properties.

[0104] The NH3-TPD spectrum of Example 4 is shown in Figure 6 The sample spectrum of Comparative Example 1 is shown in Figure 7 It can be seen from the figure that the NH3 desorption peak of the sample of Comparative Example 1 occurs at a significantly lower temperature. The desorption peaks of the weak acid and strong acid sites occur at 180℃ and 350℃, respectively, and the peak area of the strong acid site is significantly smaller. Both samples have AEI structure, and from the diffusion path comparison, the crystal particle size of Examples 1-8 is larger, and the diffusion path can be longer, which rules out the influence of structural differences on the diffusion limitation of NH3 desorption. Therefore, the lower desorption temperature and smaller peak area of the strong acid site of Comparative Example 1 show that it has significantly weaker acidic properties than Examples 1-8.

[0105] Application Example 1 (NH3-SCR catalytic reaction)

[0106] First, 5g of the molecular sieve sample prepared in Example 4 was added to 100g of a 0.02mol / L copper acetate solution, and ion exchanged at 80℃ for 5h. Then the sample was centrifuged and washed with deionized water until neutral. After drying in a 120℃ oven, the sample was calcined at 600℃ for 5h. Further, the calcined sample was tabletted and sieved, 0.3g of 60 to 80 mesh sample was mixed with 1.9g of quartz sand (60 to 80 mesh), and loaded into a fixed bed reactor. After activation at 600℃ for 40min, the temperature was lowered to 150℃ and the reaction was started, and tested point by point; after waiting for 20min at each temperature point, the data was recorded after the reaction was stable, and the test temperature range was 150-650℃;

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

[0108] The tail gas was analyzed by online FTIR using a Tensor 27 instrument of Bruker company, the CuO content in the sample was 2.5-3wt%, and the reaction results are shown in Figure 8 It can be seen that the sample has a wide active temperature window, and the conversion rate is greater than 90% from 200℃ to 500℃. The sample was subjected to 800℃ water vapor aging treatment for 16h, and the NH3-SCR evaluation was carried out again under the same experimental conditions; the results show that the catalytic activity of the sample is still good, and even has an upward trend at high temperature, which proves that the sample has excellent hydrothermal stability.

[0109] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed as above, they are not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the disclosed technical content without departing from the scope of the technical solutions of the present application, which are equivalent to equivalent embodiments, and are within the scope of the technical solutions.

Claims

1. A SAPO-18-MeR molecular sieve characterized by, The anhydrous chemical composition of the molecular sieve is: m Me · n R (Si x Al y P z )O2 Formula I; In formula I, Me is selected from at least one of Li + , Na + , K + , and NH4 + . R is an organic template selected from at least one of N,N-diisopropylethylamine, tetraethylammonium hydroxide, triethylamine, diisopropylamine, diethylamine and ethylenediamine; m is the number of moles of Me per mole of (Si x Al y P z )O2, m = 0.05 ~ 0.2; n is the number of moles of R per mole of (Si x Al y P z )O2, n = 0.05 ~ 0.2; x is (Si x Al y P z the mole fraction of Si in O2, x = 0.05 ~ 0.35; y is (Si x Al y P z )O2, the molar fraction of Al, 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. The SAPO-18-MeR molecular sieve of claim 1, wherein, The SAPO-18-MeR molecular sieve has an AEI topology structure; the metal ion Me and the organic template R are both distributed in the cage and double six-membered ring structure of the molecular sieve.

3. The SAPO-18-MeR molecular sieve of claim 1, wherein, 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%.

4. The SAPO-18-MeR molecular sieve of claim 1, wherein, The SAPO-18-MeR molecular sieve has a rhombic square shape and a particle size of 1-5 microns.

5. The SAPO-18-MeR molecular sieve of claim 1, wherein, The X-ray diffraction spectrum of the SAPO-18-MeR molecular sieve includes at least an X-ray diffraction peak at the position shown in the following table: 。 6. A process for preparing a SAPO-18-MeR molecular sieve according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1: mixing water, a silicon source, an aluminum source, a phosphorus source and an 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: heating and reacting the reaction gel under a sealed condition to crystallize to obtain a molecular sieve raw powder.

7. The method of making a SAPO-18-MeR molecular sieve of claim 6, wherein, In step S1, the molar ratio of water, the silicon source, the aluminum source, the phosphorus source and the 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 based on the molar amount of H2O itself, the molar amount of the silicon source is calculated based on the molar amount of SiO2, the molar amount of the aluminum source is calculated based on the molar amount of Al2O3, the molar amount of the phosphorus source is calculated based on P2O5, and the molar amount of the organic template is calculated based on the molar amount of R.

8. The method of making a SAPO-18-MeR molecular sieve of claim 6, wherein, The molar ratio of the inorganic salt / inorganic base Me to the template R is 0.01-1.

9. The method of making a SAPO-18-MeR molecular sieve of claim 6, wherein, The Me is selected from at least one of lithium salt, sodium salt, potassium salt and ammonium salt.

10. The method of making a SAPO-18-MeR molecular sieve of claim 9, wherein, The Me is selected from at least one of LiOH, NaOH, KOH and NH3·H2O.

11. The method of making a SAPO-18-MeR molecular sieve of claim 9, wherein, The Me is selected from at least one of LiCl, NaCl, KCl and NH4Cl.

12. The method of making a SAPO-18-MeR molecular sieve of claim 6, wherein, In step S3, the temperature of the crystallization is 130-220ºC, and the time of the crystallization is 5-72h.

13. A catalyst for acid catalyzed reactions, characterized in that, The molecular sieve of any one of claims 1-5 or the molecular sieve prepared by the method of any one of claims 6-12 is calcined in air at 400-800ºC.

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