A saop-56 molecular sieve, a preparation method and application thereof

Abstract

The application provides a kind of SAPO-56 molecular sieve and its preparation method and application, it is related to molecular sieve technical field.The application mixes water, silicon source, aluminum source, phosphorus source, triethanolamine and N, N-dimethylethylamine, obtains initial gel;The silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the phosphorus source is calculated as P2O5, the molar ratio of silicon source, phosphorus source, water, triethanolamine, N, N-dimethylethylamine and aluminum source in the initial gel is (0.15-2.5):(0.5-1.5):(8-40):(5-20):(0.1-3.5):1;The initial gel is crystallized, and SAPO-56 molecular sieve is obtained.The application uses triethanolamine as solvent and first template agent, uses N, N-dimethylethylamine as second template agent, and uses amine heat synthesis method to prepare SAPO-56 molecular sieve.The SAPO-56 molecular sieve prepared by the application shows good CO2 selective adsorption as gas adsorption separation agent, and shows good catalytic performance as catalyst in the reaction of converting oxygen-containing compounds into olefins.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, and in particular to a SAPO-56 molecular sieve, its preparation method, and its application. Background Technology

[0002] Union Carbide (UCC) first reported the synthesis of AlPO4 molecular sieves. AlO4... - and PO4 - The tetrahedral structure is electrically neutral, lacking ion exchange properties and strong acidity. SAPO molecular sieves are considered to be formed when silicon substitutes for phosphorus (P) or adjacent P-Al pairs into the AlPO4 framework. The introduction of silicon makes the SAPO molecular sieve framework electronegative, possessing exchangeable cations. Depending on the synthesis conditions and the silicon content in the sample, SAPO molecular sieves exhibit moderately strong acid and strong acid properties. SAPO-56 is a novel small-porous molecular sieve with an AFX topology. Its three-dimensional pore structure consists of double six-membered rings, GME cages, and AFT cages. Its eight-membered ring pore size is 0.34 nm × 0.36 nm, belonging to small-porous zeolites with a large cage structure. Furthermore, its surface is acidic, making it a suitable catalyst, catalyst support, ion exchanger, and adsorbent for separating and purifying molecules. Therefore, it has attracted widespread attention in industrial catalysis, adsorption separation, and ion exchange. Furthermore, the pore size of SAPO-56 molecular sieve is approximately 0.02 nm smaller than that of CHA-type SAPO-34 molecular sieve. SAPO-34 is an excellent catalyst for the conversion of methanol to low-carbon olefins and is already industrialized. Therefore, the research, development, and application of SAPO-56 are of paramount importance.

[0003] Currently, there are few literature reports on the synthesis of SAPO-56 molecular sieves. The synthesis of SAPO molecular sieves usually requires the addition of structure-directing agents. For example, US Patent 5437781 reports a study on the synthesis of SAPO-56 molecular sieves using a hydrothermal synthesis method with the organic amine N,N,N,N-tetramethyl-1,6-hexanediamine (TMHDA) as a single template agent. Chinese Patent CN115367769B reports a method for synthesizing hierarchical porous SAPO-56 zeolite molecular sieves using the inorganic template agent K2O. The choice of structure-directing agent and the synthesis method have a certain influence on the microstructure, elemental composition, and morphology of the synthesized molecular sieves, and thus affect their catalytic performance. Molecular sieves of the same structure can be synthesized using various different structure-directing agents. Similarly, by adjusting different synthesis conditions (gel ratio, synthesis method, synthesis temperature, etc.), a single structure-directing agent can be directed to synthesize molecular sieves of various structures. However, to date, the directing effect of structure-directing agents and the structure-activity relationship between them and their target molecular sieves are not yet fully understood. Although many researchers have conducted extensive research in this area and made some progress, predicting the relationship between the structure of directing agents and molecular sieves remains very difficult. Developing high-performance molecular sieves using suitable template agents remains an important research topic for researchers. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a SAPO-56 molecular sieve, its preparation method, and its applications. This invention uses triethanolamine and N,N-dimethylethylamine as template agents to prepare a SAPO-56 molecular sieve, which exhibits good performance in catalyzing the synthesis of olefins from oxygen-containing compounds and in the selective adsorption and separation of CO2.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing SAPO-56 molecular sieve, comprising the following steps:

[0007] Water, silicon source, aluminum source, phosphorus source, triethanolamine, and N,N-dimethylethylamine were mixed to obtain an initial gel; the silicon source was calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5. The molar ratio of silicon source, phosphorus source, water, triethanolamine, N,N-dimethylethylamine, and aluminum source in the initial gel was (0.15–2.5):(0.5–1.5):(8–40):(5–20):(0.1–3.5):1.

[0008] The initial gel was crystallized to obtain the SAPO-56 molecular sieve.

[0009] Preferably, the molar ratio of triethanolamine to aluminum source in the initial gel is (5.5-16):1, and the molar ratio of N,N-dimethylethylamine to aluminum source is (0.2-2.5):1.

[0010] Preferably, the silicon source includes one or more of silica sol, activated silica, orthosilicate, and metakaolin; the aluminum source includes one or more of aluminum salt, activated alumina, aluminum alkoxy, boehmite, and metakaolin; and the phosphorus source includes one or more of orthophosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, organic phosphorus compounds, and inorganic phosphorus oxides.

[0011] Preferably, the crystallization is static crystallization or dynamic crystallization; the crystallization temperature is 150-220℃ and the time is 5-72h.

[0012] This invention provides a SAPO-56 molecular sieve prepared by the preparation method described above, wherein the anhydrous chemical composition of the SAPO-56 molecular sieve is mTEOA·nDMEA(Si) x Al y P z O2, where TEOA is triethanolamine, DMEA is N,N-dimethylethylamine, and m is the concentration per mole of Si x Al y P z The number of moles of triethanolamine in O2, n being the number of moles per mole (Si). x Al y P z The molar number of N,N-dimethylethylamine in O2, m = 0.01~0.08, n = 0.01~0.12; x, y, z represent the molar fractions of Si, Al, and P respectively, x = 0.01~0.28, y = 0.35~0.55, z = 0.28~0.50, and x+y+z = 1.

[0013] This invention provides the application of the SAPO-56 molecular sieve described above in the selective adsorption and separation of CO2.

[0014] Preferably, the CO2 comes from a CO2-containing gas mixture, which includes methane and / or nitrogen.

[0015] This invention provides the application of the SAPO-56 molecular sieve described above in the catalytic reaction of oxygen-containing compounds to olefins.

[0016] Preferably, the oxygen-containing compound includes methanol and / or dimethyl ether.

[0017] Preferably, before application, the SAPO-56 molecular sieve is calcined at a temperature of 400–700°C.

[0018] This invention provides a method for preparing SAPO-56 molecular sieve, comprising the following steps: mixing water, a silicon source, an aluminum source, a phosphorus source, triethanolamine, and N,N-dimethylethylamine to obtain an initial gel; wherein the silicon source is calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5, and the molar ratio of silicon source, phosphorus source, water, triethanolamine, N,N-dimethylethylamine, and aluminum source in the initial gel is (0.15–2.5):(0.5–1.5):(8–40):(5–20):(0.1–3.5):1; and crystallizing the initial gel to obtain the SAPO-56 molecular sieve. This invention uses triethanolamine as a solvent and a first template agent, and N,N-dimethylethylamine as a second template agent, to prepare SAPO-56 molecular sieve using an ammonothermal synthesis method. The SAPO-56 molecular sieve prepared by this invention exhibits excellent selective CO2 adsorption as a gas adsorption and separation agent, and demonstrates good catalytic performance as a catalyst in the conversion of oxygen-containing compounds to olefins. Furthermore, the method of this invention uses readily available raw materials, has a simple preparation process, and is suitable for large-scale industrial production. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope (SEM) image of the SAPO-56 molecular sieve synthesized in Example 1. Detailed Implementation

[0020] This invention provides a method for preparing SAPO-56 molecular sieve, comprising the following steps:

[0021] Water, silicon source, aluminum source, phosphorus source, triethanolamine, and N,N-dimethylethylamine were mixed to obtain an initial gel; the silicon source was calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5. The molar ratio of silicon source, phosphorus source, water, triethanolamine, N,N-dimethylethylamine, and aluminum source in the initial gel was (0.15–2.5):(0.5–1.5):(8–40):(5–20):(0.1–3.5):1.

[0022] The initial gel was crystallized to obtain the SAPO-56 molecular sieve.

[0023] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known to those skilled in the art.

[0024] The present invention mixes water, silicon source, aluminum source, phosphorus source, triethanolamine (TEOA) and N,N-dimethylethylamine (DMEA) to obtain an initial gel.

[0025] In this invention, the water is preferably deionized water. In this invention, the silicon source preferably includes one or more of silica sol, activated silica, orthosilicates, and metakaolin; the orthosilicate is a compound formed by replacing hydrogen atoms in orthosilicic acid (H4SiO4) with hydrocarbon groups, such as methyl orthosilicate and ethyl orthosilicate. In this invention, the aluminum source preferably includes one or more of aluminum salts, activated alumina, aluminum alkoxy, boehmite, and metakaolin; the aluminum salt is preferably aluminum sulfate or aluminum chloride; the activated alumina is preferably γ-alumina; the aluminum alkoxy refers to a compound in which an alkyl group is linked to an aluminum atom through an oxygen atom, such as aluminum ethoxide or aluminum isopropoxide. In this invention, the phosphorus source preferably includes one or more of orthophosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, organophosphorus compounds, and inorganic phosphorus oxides; the organophosphorus compound is an organic compound containing phosphorus, preferably trimethylphosphorus or triethylphosphorus; the inorganic phosphorus oxide is preferably phosphoric anhydride. In this invention, triethanolamine is used as a solvent and a first template agent, and N,N-dimethylethylamine is used as a second template agent.

[0026] In this invention, the silicon source is calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5. The molar ratio of silicon source, phosphorus source, water, triethanolamine, N,N-dimethylethylamine and aluminum source in the initial gel is (0.15-2.5):(0.5-1.5):(8-40):(5-20):(0.1-3.5):1, preferably (0.25-2.0):(0.8-1.5):(15-30):(5.5-16):(0.2-2.5):1.

[0027] In this invention, the preferred mixing method is as follows: an aluminum source and triethanolamine are first mixed to obtain a first mixture; a silicon source is added to the first mixture for a second mixing to obtain a second mixture; a phosphorus source and water are added to the second mixture for a third mixing to obtain a third mixture; and N,N-dimethylethylamine is added to the third mixture for a fourth mixing to obtain an initial gel. In this invention, the first, second, third, and fourth mixing processes are all preferably performed by stirring, with the stirring aimed at achieving uniform mixing of all components.

[0028] After obtaining the initial gel, the present invention crystallizes the initial gel to obtain the SAPO-56 molecular sieve.

[0029] In this invention, the crystallization temperature is preferably 150–220°C, more preferably 170–210°C, and even more preferably 180–200°C, and the time is preferably 5–72 h, more preferably 12–60 h, and even more preferably 15–48 h.

[0030] In this invention, the initial gel is preferably loaded into a high-pressure synthesis reactor, sealed, transferred to an oven, heated to 150-220°C, and crystallized under autogenous pressure.

[0031] In this invention, the crystallization is preferably static crystallization or dynamic crystallization; static crystallization refers to the crystallization process in which the synthesis vessel containing the initial gel is placed statically in an oven and the mixture in the synthesis vessel is not stirred; dynamic crystallization refers to the crystallization process in which the synthesis vessel containing the initial gel is in a non-static state, such as being turned over or rotated, or the mixture in the synthesis vessel is stirred during the crystallization process. When the dynamic crystallization is carried out under rotation conditions, the rotation speed is preferably 30 to 45 r / min.

[0032] After the crystallization process is completed, the present invention preferably subjectes the obtained crystallization reaction solution to solid-liquid separation, solid phase washing, and drying in sequence to obtain SAPO-56 molecular sieve. In the present invention, the solid-liquid separation method is preferably centrifugation; the solid phase washing is preferably water washing, preferably using deionized water, and the water washing is performed until neutral; the drying temperature is preferably 100°C.

[0033] This invention provides a SAPO-56 molecular sieve prepared by the preparation method described above, wherein the anhydrous chemical composition of the SAPO-56 molecular sieve is mTEOA·nDMEA(Si) x Al y P z O2, where TEOA is triethanolamine, DMEA is N,N-dimethylethylamine, and m is the concentration per mole of Si x Al y P z The number of moles of triethanolamine in O2, n being the number of moles per mole (Si). x Al y P z The molar number of N,N-dimethylethylamine in O2, m = 0.01–0.08, n = 0.01–0.12; x, y, and z represent the molar fractions of Si, Al, and P, respectively, x = 0.01–0.28, y = 0.35–0.55, z = 0.28–0.50, and x + y + z = 1. In this invention, m is preferably 0.05–0.08, n is preferably 0.08–0.12, x is preferably 0.1–0.28, y is preferably 0.40–0.55, and z is preferably 0.30–0.50. In this invention, the triethanolamine and N,N-dimethylethylamine are distributed in the molecular sieve cages and channels. In this invention, the particle size of the SAPO-56 molecular sieve is preferably 2–5 μm.

[0034] In this invention, the SAPO-56 molecular sieve has an AFX structure, and its X-ray diffraction analysis results contain at least the diffraction peaks shown in Table 1:

[0035] Table 1. Diffraction peaks of SAPO-56 molecular sieve

[0036]

[0037]

[0038] This invention provides the application of the SAPO-56 molecular sieve described above in the selective adsorption and separation of CO2. In this invention, the CO2 preferably originates from a CO2-containing gas mixture, which preferably includes methane and / or nitrogen. That is, the SAPO-56 molecular sieve can be used for the separation of CO2 from CH4, the separation of CO2 from N2, and the separation of CO2 from a CH4+N2 mixture. In this invention, the volume percentage of CO2 in the gas mixture is preferably 20-40%.

[0039] In this invention, the SAPO-56 molecular sieve is preferably calcined before application. The calcination temperature is preferably 400–700°C, more preferably 550–650°C, and the calcination time is preferably 4 hours. The calcination is preferably carried out in air. This invention removes the template agent from the molecular sieve through calcination. After calcination, the resulting molecular sieve is preferably pressed into tablets, crushed, and then activated. The crushing preferably involves crushing the molecular sieve to 20–40 mesh. The activation temperature is preferably 550°C, the activation time is preferably 1 hour, and the activation is preferably carried out in a nitrogen atmosphere.

[0040] This invention provides the application of the SAPO-56 molecular sieve described above in the catalytic reaction of oxygen-containing compounds to olefins.

[0041] In this invention, the oxygen-containing compound preferably includes methanol and / or dimethyl ether. In this invention, the weight hourly space velocity (WHSV) of the oxygen-containing compound is preferably 2–4 h⁻¹. -1 The preferred reaction temperature for the oxygen-containing compound to olefin reaction is 400–450°C. In this invention, the reaction products corresponding to methanol and dimethyl ether are mainly ethylene and propylene.

[0042] In this invention, the SAPO-56 molecular sieve is preferably calcined before application. The calcination conditions are the same as those described above and will not be repeated here. After calcination, the resulting molecular sieve is preferably pretreated. The pretreatment temperature is preferably 350°C, and the pretreatment time is preferably 4 hours. The pretreatment is preferably carried out in a nitrogen atmosphere.

[0043] To further illustrate the present invention, the SAPO-56 molecular sieve, its preparation method, and its application provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0044] In this embodiment of the invention, the tests and test conditions involved are as follows:

[0045] Elemental composition was determined using a Philips Magix 2424 X-ray fluorescence analyzer (XRF).

[0046] X-ray powder diffraction (XRD) phase analysis was performed using a Bruker D8 Advance X-ray diffractometer, Cu target, Kα radiation source (λ = 0.15418 nm), voltage 40 kV, current 40 mA.

[0047] SEM morphology analysis was performed using a Hitachi S-4800 scanning electron microscope.

[0048] Carbon nuclear magnetic resonance (NMR) 13 CMAS NMR analysis was performed using an Infinity Plus 400WB solid-state NMR spectrometer from Varian, USA, with a BBO MAS probe and an operating magnetic field strength of 9.4T.

[0049] CHN elemental analysis was performed using a Vario EL Cube elemental analyzer manufactured in Germany.

[0050] Example 1

[0051] The preparation method of SAPO-56 molecular sieve is as follows:

[0052] The molar ratios of each raw material and crystallization conditions are shown in Table 3. The specific batching process is as follows: Boehmite (Al2O3 mass percentage 72.5%) and triethanolamine (TEOA, mass percentage ≥99.0%) are mixed and stirred evenly. Then, silica sol (SiO2 mass percentage 30.04%) is added and stirred evenly. Then, phosphoric acid (H3PO4 mass percentage 85%) is added dropwise and stirred evenly. After that, deionized water and N,N-dimethylethylamine (DMEA, mass percentage 99%) are added and stirred evenly to form a gel. The gel is then transferred to a stainless steel reactor.

[0053] After placing the reactor in a rotating oven, the temperature was raised to 200℃ and crystallized dynamically (at a rotation speed of 40 r / min) for 60 min, and then crystallized for 48 h. After crystallization, the solid product was centrifuged, washed, and dried in air at 100℃ to obtain SAPO-56 molecular sieve raw powder.

[0054] The molecular sieve powder sample prepared in Example 1 was subjected to XRD test, and the results are shown in Table 2. The results show that the synthesized product has the characteristics of SAPO-56 structure.

[0055] Table 2. XRD results of the molecular sieve samples from Example 1

[0056]

[0057]

[0058] CHN elemental analysis was performed on the raw powder sample of Example 1. The CHN elemental analysis results were normalized with the inorganic elemental composition obtained by XRF determination to obtain the composition of the molecular sieve raw powder. The results are shown in Table 4.

[0059] Figure 1 This is a scanning electron microscope (SEM) image of the SAPO-56 molecular sieve synthesized in Example 1. It has a typical hexagonal plate morphology and a particle size of 2-5 μm.

[0060] Examples 2-19

[0061] The molar proportions of each raw material and the crystallization conditions are shown in Table 3. The preparation method is the same as in Example 1.

[0062] Table 3. Molecular sieve synthesis ingredients and crystallization conditions in Examples 1-19

[0063]

[0064]

[0065] In Table 3, Example 18 is a static crystallization synthesis, while the other examples are dynamic crystallization synthesis with a rotation speed of 40 r / min.

[0066] XRD tests were performed on the molecular sieve powder samples prepared in Examples 2 to 19. The results showed that the synthesized products in Examples 2 to 19 all had the characteristics of SAPO-56 structure.

[0067] The molecular sieve powder samples prepared in Examples 1-8 were subjected to... 13 CMAS NMR analysis showed that the results were obtained by comparing the results with those of triethanolamine and N,N-dimethylethylamine. 13 Comparison with CMAS NMR standard spectra revealed that the synthesized sample simultaneously exhibited resonance peaks for both triethanolamine and N,N-dimethylethylamine. Quantitative analysis was performed based on the unique non-overlapping NMR peaks of the two substances to determine their ratio. XRF analysis of the bulk elemental composition of the molecular sieve product was conducted, and CHN elemental analysis was performed on the raw powder samples from Examples 1–8. A comprehensive analysis of CHN elemental analysis, XRF, and... 13 The composition of the molecular sieve raw powder was obtained from the ¹H NMR analysis results, as shown in Table 4.

[0068] Table 4 Composition of molecular sieve powder samples prepared in Examples 1-8

[0069] Example Sample raw powder composition 1 <![CDATA[0.06TEOA·0.09DMEA(Si 0.181 Al 0.460 P 0.359 O2<!-- 7 --> ]]> 2 <![CDATA[0.05TEOA·0.08DMEA(Si 0.118 Al 0.470 P 0.412 )O2]]> 3 <![CDATA[0.06TEOA·0.1DMEA(Si 0.231 Al 0.427 P 0.342 )O2]]> 4 <![CDATA[0.05TEOA·0.08DMEA(Si 0.194 Al 0.433 P 0.373 )O2]]> 5 <![CDATA[0.05TEOA·0.08DMEA(Si 0.108 Al 0.478 P 0.414 )O2]]> 6 <![CDATA[0.05TEOA·0.08DMEA(Si 0.160 Al 0.441 P 0.399 )O2]]> 7 <![CDATA[0.08TEOA·0.12DMEA(Si 0.28 Al 0.35 P 0.37 )O2]]> 8 <![CDATA[0.01TEOA·0.01DMEA(Si 0.01 Al 0.55 P 0.44 )O2]]>

[0070] Comparative Example 1 (No N,N-dimethylethylamine (DMEA) was added to the synthesis system)

[0071] The specific ingredient ratios, ingredient mixing process, and crystallization conditions are the same as in Example 1, except that N,N-dimethylethylamine (DMEA) is not added to the synthesized gel.

[0072] XRD analysis of the synthesized samples showed that the XRD results of the product synthesized in the triethanolamine solvothermal system were characteristic peaks of SAPO-5.

[0073] Comparative Example 2 (No triethanolamine (TEOA) was added to the synthesis system)

[0074] The molar ratio of the components in the synthesis system was 2.0 DMEA:0.6 SiO2:1.0 Al2O3:1.0 P2O5:30 H2O. The specific synthesis steps were as follows: Boehmite (72.5% Al2O3 by mass) and deionized water were mixed and stirred until homogeneous. Then, silica sol (30.04% SiO2 by mass) was added and stirred until homogeneous. Phosphoric acid (85% H3PO4 by mass) was then added dropwise and stirred until homogeneous. N,N-dimethylethylamine (DMEA, 99% by mass) was added to the resulting mixture and stirred until homogeneous. The resulting gel was then transferred to a stainless steel reactor. The reactor was placed in an oven and crystallized dynamically at 200℃ for 48 hours. After crystallization, the solid product was centrifuged, washed, and dried in air at 100℃.

[0075] XRD analysis of the synthesized sample showed that the XRD result of the synthesized product was a characteristic peak of SAPO-34.

[0076] Application Example 1

[0077] The sample obtained in Example 1 was calcined at 550°C with air for 4 hours, then tableted and crushed to 20-40 mesh. 1.0 g of the sample was weighed and loaded into a fixed-bed reactor for MTO reaction evaluation. Activation was performed at 550°C with nitrogen for 1 hour, followed by cooling to 450°C for the reaction. Methanol was carried by nitrogen gas at a flow rate of 40 mL / min and a methanol weight hourly space velocity (WHSV) of 4.0 h⁻¹. -1 The reaction products were analyzed by online gas chromatography (Varian 3800, FID detector, capillary column PoraPLOT Q-HT). The results are shown in Table 5.

[0078] Table 5 Results of methanol-to-olefins reaction of molecular sieve samples

[0079]

[0080] Application Example 2

[0081] The molecular sieve sample obtained in Example 3 was calcined at 550°C with air for 4 hours. Adsorption isotherms for CO2, CH4, and N2 were measured using a Micromeritics Gemini VII 2390 instrument. The sample was pretreated at 350°C in an N2 atmosphere for 4 hours before measurement. The adsorption test was conducted at a constant temperature of 25°C and a pressure of 101 kPa. The adsorption separation results are shown in Table 6. Similarly, the samples obtained in Examples 1 and 2 also exhibited high CO2 adsorption capacity and high CO2 / CH4 and CO2 / N2 adsorption separation ratios.

[0082] Table 6 shows the CO2 / CH4 adsorption and separation results of the samples.

[0083]

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing SAPO-56 molecular sieve, characterized in that, Includes the following steps: Water, silicon source, aluminum source, phosphorus source, triethanolamine, and N,N-dimethylethylamine were mixed to obtain an initial gel; the silicon source was calculated as SiO2, the aluminum source as Al2O3, and the phosphorus source as P2O5. The molar ratio of silicon source, phosphorus source, water, triethanolamine, N,N-dimethylethylamine, and aluminum source in the initial gel was (0.15~2.5):(0.5~1.5):(8~40):(5~20):(0.1~3.5):

1. The initial gel was crystallized to obtain the SAPO-56 molecular sieve.

2. The preparation method according to claim 1, characterized in that, The initial gel contains triethanolamine in a molar ratio of (5.5~16):1 to aluminum source, and N,N-dimethylethylamine in a molar ratio of (0.2~2.5):1 to aluminum source.

3. The preparation method according to claim 1 or 2, characterized in that, The silicon source includes one or more of silica sol, active silica, orthosilicate, and metakaolin; the aluminum source includes one or more of aluminum salt, active alumina, alkoxyaluminum, boehmite, and metakaolin; and the phosphorus source includes one or more of orthophosphoric acid, diammonium hydrogen phosphate, organic phosphorus compounds, and inorganic phosphorus oxides.

4. The preparation method according to claim 1, characterized in that, The crystallization is either static or dynamic; the crystallization temperature is 150~220℃, and the time is 5~72h.

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