Preparation method and use of a SAPO-17 / SAPO-34 composite molecular sieve

Abstract

The present invention provides a preparation method of a SAPO-17 / SAPO-34 composite molecular sieve. The present invention also provides the SAPO-17 / SAPO-34 composite molecular sieve prepared by the said preparation method and its uses. The preparation method provided by the present invention first mixes an aluminum source, a phosphorus source, a silicon source, and a first template agent, then adds a SAPO-34 molecular sieve and a second template agent. After mixing evenly, hydrothermal crystallization and calcination are carried out to obtain the SAPO-17 / SAPO-34 composite molecular sieve. The process is simple, the conditions are mild, the operability is strong, the repeatability is good, there is no need for high cost and complex equipment, and it is suitable for large-scale industrial production. In the composite molecular sieve provided by the present invention, the proportion of the two phases of SAPO-17 and SAPO-34 can be conveniently adjusted, and it has excellent properties, especially catalytic properties, so it has very good application prospects.

Description

Technical Field

[0001] The present invention relates to the field of catalyst preparation, and particularly to a preparation method of SAPO-17 / SAPO-34 composite molecular sieve, the SAPO-17 / SAPO-34 composite molecular sieve prepared thereby and its uses, and also to a method for producing olefins from organic oxygenates. Background Art

[0002] The MTO process for producing olefins from methanol is one of the important chemical technologies. Using methanol synthesized from coal or natural gas as raw material to produce light olefins is the core technology for developing the production of ethylene, propylene and other chemical products from non-petroleum resources.

[0003] SAPO-34 molecular sieve is one of the common catalysts for the reaction of producing olefins from methanol, with high activity and good selectivity for ethylene and propylene, but the selectivity for butene is not high, and its small-pore microporous structure easily leads to catalyst deactivation. SAPO-17 molecular sieve is a molecular sieve with an ERI-type erionite-like topological structure, having the same eight-membered ring three-dimensional pore channels as SAPO-34 molecular sieve. SAPO-17 molecular sieve can also be used for the reaction of producing olefins from methanol, but its catalytic effect is not as good as that of SAPO-34 molecular sieve.

[0004] At present, a variety of composite molecular sieves have been reported. Compared with single molecular sieves, composite molecular sieves can exhibit some unique product properties. Chinese Patent CN 1299775A reports a method for preparing SAPO-17 and SAPO-44 molecular sieves, and pure-phase SAPO-17, SAPO-44 and the symbiotic molecular sieve of the two can be prepared by controlling the amount of silica in the reaction mixture. Chinese Patent CN 105984877A reports a synthesis method of SAPO-17 / SAPO-56 eutectic molecular sieve. Its synthesis method mainly uses triethanolamine and N,N,N’,N’-tetramethyl-1,6-hexanediamine as template agents, and the eutectic structure of SAPO-17 and SAPO-56 molecular sieves is synthesized by hydrothermal crystallization. As a catalyst, it shows good catalytic performance in acid-catalyzed reactions and the reaction of converting oxygenates to olefins; as a gas adsorption separator, it also shows good performance in the separation of CO2 and N2. Chinese Patent CN 106185982A reports a symbiotic composite molecular sieve of small-pore microporous molecular sieve SAPO-34 and large-pore microporous molecular sieve SAPO-5. This molecular sieve is used for producing light olefins from organic oxygenates while rich-producing gasoline, and the selectivity of gasoline products can reach 15-21%.

[0005] It can be seen that researching and developing more types of SAPO series molecular sieves, improving their performance, and expanding their applications have very significant economic and social values. However, compared with single molecular sieves, the factors affecting the synthesis of composite molecular sieves are more complex. The precise control of the proportion of different molecular sieves and how to improve the repeatability of synthesis are the difficulties in the synthesis of such molecular sieves. Summary of the Invention

[0006] To make up for the deficiencies in the prior art, an object of the present invention is to provide a preparation method of SAPO-17 / SAPO-34 composite molecular sieve. The preparation method has a simple process, good repeatability, adjustable two-phase ratio in the molecular sieve, and the prepared composite molecular sieve can be used as a catalyst for various reactions and has excellent catalytic performance.

[0007] Another object of the present invention is to provide a SAPO-17 / SAPO-34 composite molecular sieve and its uses.

[0008] Still another object of the present invention is to provide a method for producing olefins from organic oxygenates.

[0009] The preparation method of the SAPO-17 / SAPO-34 composite molecular sieve provided by the present invention comprises the following steps:

[0010] S1: Mixing an aluminum source, a phosphorus source, a silicon source, water, and a first template agent T1 to obtain a first mixed solution;

[0011] S2: Mixing SAPO-34 molecular sieve, a second template agent T2, and the first mixed solution to obtain a second mixed solution, wherein the molar ratio of substances is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1:0.5 - 1.5:0.01 - 0.3:20 - 200:0.5 - 5.0:0.1 - 4.0; and

[0012] S3: Crystallizing the second mixed solution, and drying and calcining the obtained solid matter to obtain the SAPO-17 / SAPO-34 composite molecular sieve.

[0013] The preparation method provided by the present invention synthesizes the SAPO-17 / SAPO-34 composite molecular sieve by improving the material composition, addition sequence, etc. Specifically, in step S1, a synthesis system for SAPO-17 molecular sieve is mainly established, and then a certain amount of SAPO-34 molecular sieve is added in step S2. It can not only serve as a material source but also play the role of a seed crystal. After being treated with the basic second template T2, it can form initial structural units, which play an inducing and templating role in the formation of SAPO-34 molecular sieve in the SAPO-17 molecular sieve synthesis system. Moreover, the addition of SAPO-34 molecular sieve can also play a role in adjusting the two-phase composition in the composite molecular sieve. Thus, the two-phase composition in the composite molecular sieve can be conveniently adjusted to obtain more types and more properties of molecular sieves.

[0014] In the preparation method provided by the present invention, the aluminum source can be common types used in the field for preparing SAPO molecular sieves. In some preferred embodiments, the aluminum source can be selected from one or more of pseudoboehmite, aluminum sol, and aluminum isopropoxide.

[0015] In the preparation method provided by the present invention, the phosphorus source can be common types used in the field for preparing SAPO molecular sieves. In some preferred embodiments, the phosphorus source can be selected from one or both of phosphoric acid and phosphorous acid.

[0016] In the preparation method provided by the present invention, the silicon source can be common types used in the field for preparing SAPO molecular sieves. In some preferred embodiments, the silicon source can be selected from one or more of silica sol, tetraethyl orthosilicate, and precipitated silica.

[0017] In the preparation method provided by the present invention, the first template T1 is selected from cyclohexylamine.

[0018] In the preparation method provided by the present invention, the second template T2 can be selected from one or more of N,N-diisopropylethylamine, diisopropylamine, triethylamine, diethylamine, tetraethylammonium hydroxide, n-butylamine, and morpholine.

[0019] In the preparation method provided by the present invention, the SAPO-34 molecular sieve can be a commercially available product or can be prepared according to the conventional methods in the art, for example, prepared according to the preparation process described in Comparative Example 1 of the present invention.

[0020] In the step S1 of the preparation method provided by the present invention, the aluminum source, phosphorus source, silicon source, water, and the first template T1 can be in any mixing order, and the materials can also be mixed evenly by means such as stirring. In some preferred embodiments, the aluminum source and water (such as deionized water) can be mixed first, then the phosphorus source is added. After mixing evenly, the silicon source is added, and after mixing evenly, the first template T1 is added. After mixing evenly, the first mixed solution is obtained.

[0021] In the preparation method provided by the present invention, in step S2, the dosage of the SAPO-34 molecular sieve is 0.1-20% of the mass of Al2O3 (converted according to the mass of the aluminum source), for example, it can be about 0.1%, about 0.5%, about 1%, about 2%, about 5%, about 10%, about 12%, about 15%, about 18%, about 20% or any combination within the weight percentage range.

[0022] In the preparation method provided by the present invention, in step S2, the molar ratio of substances in the second mixed solution can further be Al2O3:P2O5:SiO2:H2O:T1:T2 = 1:0.8-1.2:0.03-0.1:50-100:1-1.8:1-2.

[0023] In the preparation method provided by the present invention, in step S2, first, the SAPO-34 molecular sieve and the second template agent T2 are mixed for 0.5-4 hours until homogeneous, and then mixed with the first mixed solution for 0.5-8 hours until homogeneous to obtain the second mixed solution.

[0024] In the preparation method provided by the present invention, in step S3, the crystallization can be a common hydrothermal crystallization step in the art. In some preferred embodiments, the crystallization can be hydrothermal crystallization at 150-210°C for 6-60 hours. In some more preferred embodiments, the crystallization can be hydrothermal crystallization at 180-200°C for 24-48 hours.

[0025] In the preparation method provided by the present invention, in step S3, the drying can be a common drying step in the art. In some preferred embodiments, the drying can be drying at 80-150°C for 6-48 hours. In some more preferred embodiments, the drying can be drying at 100-130°C for 6-24 hours.

[0026] In the preparation method provided by the present invention, in step S3, the calcination can be a common calcination step in the art. In some preferred embodiments, the calcination can be calcination at 400-700°C for 2-12 hours. In some more preferred embodiments, the calcination can be calcination at 500-600°C for 6-10 hours.

[0027] In the preparation method provided by the present invention, the mixing of materials can be promoted by stirring, and the stirring method can be a common method in the art, including but not limited to mechanical stirring, magnetic stirring, etc.

[0028] In the preparation method provided by the present invention, the required materials can be obtained through a separation step. For example, a solid substance is obtained by separation after crystallization. The separation method can be a common method in the art, including but not limited to (atmospheric or vacuum) filtration, centrifugation, etc.

[0029] The present invention also provides a SAPO-17 / SAPO-34 composite molecular sieve, which is prepared by the preparation method according to any one of the above technical solutions.

[0030] In the SAPO-17 / SAPO-34 composite molecular sieve provided by the present invention, the weight percentage of the SAPO-34 molecular sieve can be 10-50%, for example, it can be about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, or it can be any combination of weight percentage ranges. In some preferred embodiments, the weight percentage of the SAPO-34 molecular sieve can be 15-40%. In some more preferred embodiments, the weight percentage of the SAPO-34 molecular sieve can be 20-25%.

[0031] Since both the SAPO-17 molecular sieve and the SAPO-34 molecular sieve are typical microporous molecular sieves, the SAPO-17 / SAPO-34 composite molecular sieve provided by the present invention is similar to the two single molecular sieves in terms of pore volume, pore size, etc., and still exhibits typical microporous structure characteristics.

[0032] The X-ray diffraction (XRD) pattern of the SAPO-17 / SAPO-34 composite molecular sieve provided by the present invention has characteristic diffraction peaks at the following diffraction angles 2θ: 7.76±0.2°, 9.77±0.2°, 13.38±0.2°, 9.51±0.2°, 16.03±0.2°, and 25.83±0.2°.

[0033] The SAPO-17 / SAPO-34 composite molecular sieve provided by the present invention is similar to the SAPO-17 molecular sieve in terms of appearance morphology, showing a needle-like or rod-like shape.

[0034] The present invention also provides the use of the SAPO-17 / SAPO-34 composite molecular sieve prepared by the preparation method according to any one of the above technical solutions or the SAPO-17 / SAPO-34 composite molecular sieve according to any one of the above technical solutions as a catalyst, for example, as a catalyst for catalyzing organic oxygen-containing compounds to produce (lower carbon) olefins.

[0035] Among them, the reaction of producing (lower-carbon) olefins from the organic oxygen-containing compound is known to those skilled in the art and can be carried out in a fixed-bed reactor, a moving-bed reactor, or a fluidized-bed reactor. The organic oxygen-containing compound can be one or more of methanol, ethanol, dimethyl ether, diethyl ether, methyl ethyl ether, halogenated substituents of methane (such as chloromethane, bromomethane, etc.), dimethyl carbonate, and methyl formate, and preferably methanol.

[0036] The present invention also provides the use of the SAPO-17 / SAPO-34 composite molecular sieve prepared by the preparation method according to any one of the above technical solutions or the SAPO-17 / SAPO-34 composite molecular sieve according to any one of the above technical solutions as a catalyst for catalytic methanol-to-olefins.

[0037] The present invention also provides a method for producing olefins from an organic oxygen-containing compound, wherein the method uses the SAPO-17 / SAPO-34 composite molecular sieve prepared by the preparation method according to any one of the above technical solutions or the SAPO-17 / SAPO-34 composite molecular sieve according to any one of the above technical solutions as a catalyst.

[0038] The present invention also provides a method for producing olefins from methanol, wherein the method uses the SAPO-17 / SAPO-34 composite molecular sieve prepared by the preparation method according to any one of the above technical solutions or the SAPO-17 / SAPO-34 composite molecular sieve according to any one of the above technical solutions as a catalyst.

[0039] In the olefin production method provided by the present invention, except for the catalyst, other process conditions can refer to the common process conditions in the art and can be appropriately adjusted by those skilled in the art.

[0040] The technical solution provided by the present invention has the following advantages:

[0041] (1) In the preparation method provided by the present invention, an aluminum source, a phosphorus source, a silicon source, and a first template agent are first mixed, and then the SAPO-34 molecular sieve and a second template agent are added. After mixing evenly, hydrothermal crystallization and calcination are carried out to obtain the SAPO-17 / SAPO-34 composite molecular sieve. The process is simple, the conditions are mild, the operability is strong, the repeatability is good, there is no need for high cost and complex equipment, and it is suitable for large-scale industrial production.

[0042] (2) In the composite molecular sieve obtained by using the preparation method provided by the present invention, the ratio of the two phases of SAPO-17 and SAPO-34 can be conveniently adjusted, so that more types of molecular sieves can be obtained, and then the performance can be adjusted and the application range can be expanded.

[0043] (3) In the SAPO-17 / SAPO-34 composite molecular sieve provided by the present invention, SAPO-17 and SAPO-34 can act synergistically, thus having excellent properties, especially catalytic properties. It can be used to catalyze various reaction types, especially the reaction of converting organic oxygen-containing compounds (such as methanol) into light olefins, and can effectively improve the yield and selectivity of ethylene.

[0044] In summary, the preparation method provided by the present invention and the SAPO-17 / SAPO-34 composite molecular sieve obtained therefrom have low cost, are easy to manufacture, are suitable for large-scale production, have important economic and social values, and thus have very good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 X-ray diffraction (XRD) patterns of the molecular sieves synthesized in Example 1 and Comparative Examples 1-4.

[0046] Figure 2 Scanning electron microscope (SEM) image of the molecular sieve synthesized in Example 1.

[0047] Figure 3 SEM image of the molecular sieve synthesized in Comparative Example 1.

[0048] Figure 4 SEM image of the molecular sieve synthesized in Comparative Example 2.

[0049] Figure 5 SEM image of the molecular sieve synthesized in Comparative Example 3.

[0050] Figure 6 SEM image of the molecular sieve synthesized in Comparative Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0051] The technical solutions of the present invention will be further described in detail below with reference to specific examples.

[0052] The raw materials or reagents used in the examples and comparative examples of the present invention are all commercially available products unless otherwise specified.

[0053] The percentages used in the examples and comparative examples of the present invention are all mass percentages unless otherwise specified.

[0054] In the examples and comparative examples of the present invention, the proportion of molecular sieves with different phase structures in the composite molecular sieve is determined according to the characteristic diffraction peaks of each molecular sieve in the XRD pattern, that is, the proportion of each phase is calculated according to the peak area of the characteristic diffraction peak of each molecular sieve.

[0055] The specific calculation method is as follows: The characteristic diffraction peaks of SAPO-17 molecular sieve include: 7.76°, 9.77°, and 13.38°; The characteristic diffraction peaks of SAPO-34 molecular sieve include 9.51°, 16.03°, and 25.83°.

[0056] Sum up the peak areas of the characteristic diffraction peaks of SAPO-17 molecular sieve and SAPO-34 molecular sieve respectively, and denote them as A1 and A2. The proportion of SAPO-17 molecular sieve in the composite molecular sieve = (A1 / (A1 + A2)) × 100%; The proportion of SAPO-34 molecular sieve = (A2 / (A1 + A2)) × 100%.

[0057] Example 1

[0058] 1) Mix 11.00 g of pseudo-boehmite (aluminum oxide content 67%) and 58.93 g of deionized water and stir. Dropwise add 16.85 g of phosphoric acid (85%). After stirring evenly, dropwise add 0.75 g of silica sol (30%). Continue to stir for 2 hours and then add 7.28 g of template agent T1 cyclohexylamine, and stir for 2 hours to obtain mixed solution A.

[0059] 2) Take 0.5 g of SAPO-34 molecular sieve and add it to 7.43 g of template agent T2 triethylamine. Stir at room temperature for 3 hours. After stirring evenly, add it to the above mixed solution A and continue to stir for 2 hours to obtain mixed solution B. The molar ratio of each substance in mixed solution B is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1.0:1.0:0.05:50.0:1.0:1.0.

[0060] 3) Transfer the above mixed solution B into a reaction kettle with a polytetrafluoroethylene inner lining, hydrothermally crystallize at 200 °C for 24 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the molecular sieve raw powder, and calcine it in an air atmosphere at 550 °C for 8 hours to obtain the SAPO-17 / SAPO-34 composite molecular sieve.

[0061] The XRD pattern of the SAPO-17 / SAPO-34 composite molecular sieve is as [[ID=...]] Figure 1 shown, and the microscopic morphology (SEM image) is as Figure 2 shown.

[0062] From Figure 1It can be seen that: in addition to the characteristic diffraction peaks of SAPO-17 molecular sieve at 7.76°, 9.77° and 13.38°, the characteristic diffraction peaks of SAPO-34 molecular sieve also appear at 9.51°, 16.03° and 25.83°, which proves that the synthesized molecular sieve sample is SAPO-17 / SAPO-34 composite molecular sieve.

[0063] Calculated according to the peak areas of the characteristic diffraction peaks of the two molecular sieves, the proportion of SAPO-34 in the composite molecular sieve is 23%.

[0064] Example 2

[0065] 1) Mix 18.68 g of aluminum isopropoxide and 80.08 g of deionized water and stir. Dropwise add 8.45 g of phosphoric acid (85%), and after stirring evenly, dropwise add 0.30 g of silica sol (30%). After continuing to stir for 2 hours, add 6.81 g of template T1 cyclohexylamine and stir for 2 hours to obtain a mixed solution A.

[0066] 2) Take 1.00 g of SAPO-34 molecular sieve and add it to 4.66 g of template T2 diisopropylamine. Stir at room temperature for 2 hours. After stirring evenly, add it to the above mixed solution A and continue to stir for 2 hours to obtain a mixed solution B. The molar ratio of each substance in the mixed solution B is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1.0:0.8:0.03:100.0:1.5:1.0.

[0067] 3) Transfer the above mixed solution B into a reaction kettle with a polytetrafluoroethylene inner lining and hydrothermally crystallize at 190 °C for 36 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the molecular sieve raw powder, and calcine it in an air atmosphere at 550 °C for 8 hours to obtain the SAPO-17 / SAPO-34 composite molecular sieve. Its XRD pattern and SEM image are both similar to those in Example 1, indicating that the expected molecular sieve product is synthesized.

[0068] Calculated according to the peak areas of the characteristic diffraction peaks of the two molecular sieves, the proportion of SAPO-34 in the composite molecular sieve is 36%.

[0069] Example 3:

[0070] 1) Mix 11.00 g of pseudo-boehmite (aluminum oxide content 67%) and 69.42 g of deionized water and stir. Dropwise add 18.59 g of phosphoric acid (85%), and after stirring evenly, dropwise add 1.50 g of silica sol (30%). After continuing to stir for 2 hours, add 10.95 g of template T1 cyclohexylamine and stir for 2 hours to obtain a mixed solution A.

[0071] 2) Add 0.10 g of SAPO-34 molecular sieve to 10.78 g of template T2 diethylamine, stir at room temperature for 1 hour. After stirring evenly, add it to the above-mentioned mixed solution A, and continue to stir for 3 hours to obtain mixed solution B. The molar ratio of each substance in mixed solution B is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1.0:1.10:0.10:58.0:1.5:2.0.

[0072] 3) Transfer the above-mentioned mixed solution B into a reaction kettle with a polytetrafluoroethylene inner liner, carry out hydrothermal crystallization at 180 °C for 48 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the molecular sieve raw powder, and calcine it in an air atmosphere at 550 °C for 8 hours to obtain the SAPO-17 / SAPO-34 composite molecular sieve. Its XRD pattern and SEM image are both similar to those in Example 1, indicating that the expected molecular sieve product has been synthesized.

[0073] It can be calculated according to the peak areas of the characteristic diffraction peaks of the two molecular sieves that the proportion of SAPO-34 in the composite molecular sieve is 12%.

[0074] Example 4

[0075] 1) Mix and stir 11.00 g of pseudo-boehmite (aluminum oxide content 67%) and 80.00 g of deionized water, add dropwise 16.01 g of phosphoric acid (85%), after stirring evenly, add dropwise 1.15 g of silica sol (30%), and continue to stir for 2 hours, then add 13.15 g of template T1 cyclohexylamine and stir for 2 hours to obtain mixed solution A.

[0076] 2) Add 1.50 g of SAPO-34 molecular sieve to 11.50 g of template T2 triethylamine, stir at room temperature for 2 hours. After stirring evenly, add it to the above-mentioned mixed solution A, and continue to stir for 2 hours to obtain mixed solution B. The molar ratio of each substance in mixed solution B is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1.0:0.95:0.08:66.0:1.8:1.55.

[0077] 3) Transfer the above-mentioned mixed solution B into a reaction kettle with a polytetrafluoroethylene inner liner, carry out hydrothermal crystallization at 180 °C for 48 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the molecular sieve raw powder, and calcine it in an air atmosphere at 550 °C for 8 hours to obtain the SAPO-17 / SAPO-34 composite molecular sieve. Its XRD pattern and SEM image are both similar to those in Example 1, indicating that the expected molecular sieve product has been synthesized.

[0078] Calculated according to the peak areas of the characteristic diffraction peaks of the two molecular sieves, the proportion of SAPO-34 in the composite molecular sieve is 42%.

[0079] Example 5

[0080] 1) Mix 11.00 g of pseudo-boehmite (aluminum oxide content 67%) and 58.93 g of deionized water and stir. Dropwise add 16.85 g of phosphoric acid (85%), and after stirring evenly, dropwise add 1.56 g of tetraethyl orthosilicate. Continue stirring for 2 hours and then add 7.28 g of template T1 cyclohexylamine, and stir for 2 hours to obtain a mixed solution A.

[0081] 2) Take 0.5 g of SAPO-34 molecular sieve and add it to 7.43 g of template T2 triethylamine. Stir at room temperature for 3 hours. After stirring evenly, add it to the above mixed solution A and continue stirring for 2 hours to obtain a mixed solution B. The molar ratio of each substance in the mixed solution B is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1.0:1.0:0.10:50.0:1.0:1.0.

[0082] 3) Transfer the above mixed solution B into a reaction kettle with a polytetrafluoroethylene inner lining, hydrothermally crystallize at 200 °C for 24 hours. After the crystallization is completed, centrifuge and separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the molecular sieve raw powder, and calcine it in an air atmosphere at 550 °C for 8 hours to obtain the SAPO-17 / SAPO-34 composite molecular sieve. Its XRD pattern and SEM image are similar to those of Example 1, indicating that the expected molecular sieve product is synthesized.

[0083] Calculated according to the peak areas of the characteristic diffraction peaks of the two molecular sieves, the proportion of SAPO-34 in the composite molecular sieve is 18%.

[0084] Comparative Example 1

[0085] Mix 10.00 g of pseudo-boehmite (aluminum oxide content 67%), 14.88 g of phosphoric acid (85%) and 47.23 g of deionized water and stir. After stirring for 1 hour, dropwise add 7.71 g of silica sol (30%). After stirring evenly, add 19.65 g of template triethylamine (TEA), and continue stirring for 1 hour. Age at room temperature for 2 hours. The molar ratio of the materials in the obtained gel is: 3.0 TEA:0.6 SiO2:1.0 Al2O3:1.0 P2O5:50 H2O. Transfer the above gel into a reaction kettle with a polytetrafluoroethylene inner lining, hydrothermally crystallize at 200 °C for 48 hours. After the obtained product is centrifugally washed, filtered and dried with deionized water, it is calcined in an air atmosphere at 550 °C for 8 hours to obtain a molecular sieve product.

[0086] The XRD pattern of the zeolite product is as shown in Figure 1 and the microscopic morphology (SEM image) is as shown in Figure 3 . By comparing with the characteristic diffraction peaks of existing zeolites, the results show that the obtained zeolite product is SAPO-34 zeolite.

[0087] Comparative Example 2

[0088] 1) Mix 11.00 g of pseudo-boehmite (aluminum oxide content 67%) and 58.93 g of deionized water and stir. Dropwise add 16.85 g of phosphoric acid (85%). After stirring evenly, dropwise add 0.75 g of silica sol (30%). Continue to stir for 2 hours and then add 7.28 g of template T1 cyclohexylamine. Stir for 2 hours to obtain a mixed solution A. Dropwise add 7.43 g of template T2 triethylamine to the mixed solution A and stir at room temperature for 2 hours. The molar ratio of each substance in the mixed solution A is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1.0:1.0:0.05:50.0:1.0:1.0.

[0089] 2) Transfer the above mixed solution into a reaction kettle with a polytetrafluoroethylene lining, hydrothermally crystallize at 200 °C for 24 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the zeolite raw powder, and calcine it in an air atmosphere at 550 °C for 8 hours to obtain the zeolite product.

[0090] The XRD pattern of the zeolite product is as shown in Figure 1 and the microscopic morphology (SEM image) is as shown in Figure 4 . By comparing with the characteristic diffraction peaks of existing zeolites, the results show that the obtained zeolite product is SAPO-47 zeolite.

[0091] Comparative Example 3

[0092] 1) Mix 11.00 g of pseudo-boehmite (aluminum oxide content 67%) and 58.93 g of deionized water and stir. Dropwise add 16.85 g of phosphoric acid (85%). After stirring evenly, dropwise add 0.75 g of silica sol (30%). Continue to stir for 2 hours and then add 7.28 g of template T1 cyclohexylamine. Stir for 2 hours to obtain a mixed solution A. Add 0.5 g of SAPO-34 zeolite to the mixed solution A and stir at room temperature for 2 hours. The molar ratio of each substance in the mixed solution A is Al2O3:P2O5:SiO2:H2O:T1 = 1.0:1.0:0.05:50.0:1.0.

[0093] 2) Transfer the above mixed solution into a reaction kettle with a polytetrafluoroethylene liner, perform hydrothermal crystallization at 200 °C for 24 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the zeolite precursor powder, and calcine it at 550 °C for 8 hours in an air atmosphere to obtain the corresponding zeolite product.

[0094] The XRD pattern of this zeolite product is as Figure 1 shown, and the microscopic morphology (SEM image) is as Figure 5 shown. It can be seen from Figure 1 that: in addition to the characteristic diffraction peaks of SAPO-17 zeolite appearing at 7.76°, 9.77° and 13.38°, the characteristic diffraction peaks of AlPO4-5 zeolite also appear at 7.55°, 12.90° and 14.92°, and the characteristic diffraction peaks of SAPO-44 zeolite appear at 16.14° and 20.81°. This indicates that the obtained zeolite product is SAPO-17 / SAPO-44 / AlPO4-5.

[0095] According to the calculation based on the peak areas of the characteristic diffraction peaks of different zeolites, the phase ratio of SAPO-17 / SAPO-44 / AlPO4-5 in the composite zeolite is: 45:21:34.

[0096] Comparative Example 4

[0097] 1) Mix and stir 26.96 g of aluminum isopropoxide and 56.18 g of deionized water, add dropwise 15.16 g of phosphoric acid (85%), after stirring evenly, add dropwise 1.35 g of silica sol (30%), continue to stir for 2 hours, then add 6.56 g of template T1 cyclohexylamine, and stir for 2 hours to obtain a mixed solution. The molar ratio of each substance in the mixed solution is Al2O3:P2O5:SiO2:H2O:T1 = 1.0:1.0:0.10:50.0:1.0.

[0098] 2) Transfer the above mixed solution into a reaction kettle with a polytetrafluoroethylene liner, perform hydrothermal crystallization at 200 °C for 120 hours. After the crystallization is completed, centrifuge to separate the solid product, wash it repeatedly with deionized water until neutral, dry it at 120 °C for 12 hours to obtain the zeolite precursor powder, and calcine it at 550 °C for 8 hours in an air atmosphere to obtain the zeolite product.

[0099] The XRD pattern of this zeolite product is as Figure 1 shown, and the microscopic morphology (SEM image) is as Figure 6 shown. Comparing with the existing characteristic diffraction peaks of zeolites, the results show that the obtained zeolite product is SAPO-17 zeolite.

[0100] Test Example

[0101] Using a fixed-bed catalytic reaction evaluation device, the molecular sieve catalysts prepared in Examples 1-5 and Comparative Examples 1-4 were evaluated for the methanol-to-olefins reaction.

[0102] The evaluation conditions were as follows: 0.8 g of the above-mentioned molecular sieve catalyst sample was weighed and placed in a reactor, activated with nitrogen at 500 °C for 0.5 h, then cooled to 450 °C. The raw material methanol solution passed through a flow metering pump and was mixed with the carrier gas - nitrogen and entered a preheating furnace, vaporized into a gas in the preheating furnace, and then entered the reactor for reaction. The nitrogen flow rate was 14 mL / min, and the methanol space velocity was 3.00 h -1 , and the reaction products were analyzed online by an Agilent 7890B chromatograph. The evaluation results are shown in Table 1.

[0103] Table 1 Catalyst evaluation results for methanol-to-olefins

[0104]

[0105] It can be seen from the results in Table 1 that compared with the molecular sieves of Comparative Examples 1-4, in the SAPO-17 / SAPO-34 composite molecular sieve prepared by the method of the present invention, through the synergistic effect of SAPO-17 molecular sieve and SAPO-34 molecular sieve, excellent catalytic effects were achieved, effectively improving the yield and selectivity of ethylene, and thus it has great industrial practical value.

[0106] In addition, it can be seen from Examples 1-5 that the preparation method of the present invention has good reproducibility, and the expected composite molecular sieve can be obtained when the phase composition changes. It can also be seen from Comparative Example 2 and Comparative Example 3 that in the preparation method of the present invention, the composition and addition sequence of the materials are also very important, and the expected composite molecular sieve cannot be obtained with minor changes in conditions, let alone the expected molecular sieve performance.

[0107] Unless otherwise specified, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0108] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the protection scope of the present invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A preparation method of a SAPO-17 / SAPO-34 composite molecular sieve, characterized in that, Comprising the following steps: S1: Mix an aluminum source, a phosphorus source, a silicon source, water, and a first template agent T1 to obtain a first mixed solution; S2: Mix a SAPO-34 molecular sieve, a second template agent T2, and the first mixed solution to obtain a second mixed solution, wherein the molar ratio of the substances is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1:0.5 - 1.5:0.01 - 0.3:20 - 200:0.5 - 5.0:0.1 - 4.0; and S3: Crystallize the second mixed solution, and the obtained solid is dried and calcined to obtain the SAPO-17 / SAPO-34 composite molecular sieve; Wherein, the first template agent T1 is selected from cyclohexylamine; the second template agent T2 is selected from one or more of N,N-diisopropylethylamine, diisopropylamine, triethylamine, diethylamine, tetraethylammonium hydroxide, n-butylamine, and morpholine.

2. The preparation method according to claim 1, characterized in that, The aluminum source is selected from one or more of pseudoboehmite, aluminum sol, and aluminum isopropoxide; and / or The phosphorus source is selected from one or two of phosphoric acid and phosphorous acid; and / or The silicon source is selected from one or more of silica sol, tetraethyl orthosilicate, and fumed silica.

3. The preparation method according to claim 1, characterized in that, In step S2, the dosage of the SAPO-34 molecular sieve is 0.1 - 20% of the mass of Al2O3.

4. The preparation method according to claim 1, wherein, In step S2, the molar ratio of the substances in the second mixed solution is Al2O3:P2O5:SiO2:H2O:T1:T2 = 1:0.8 - 1.2:0.03 - 0.1:50 - 100:1 - 1.8:1 - 2.

5. The preparation method according to any one of claims 1-4, characterized in that, In step S2, first mix the SAPO-34 molecular sieve and the second template agent T2 for 0.5 - 4 hours until uniform, and then mix with the first mixed solution for 0.5 - 8 hours until uniform to obtain the second mixed solution.

6. The preparation method according to any one of claims 1 to 4, characterized in that, In step S3, the crystallization is hydrothermal crystallization at 150 - 210°C for 6 - 60 hours; and / or The drying is drying at 80 - 150°C for 6 - 48 hours; and / or The calcination is calcination at 400 - 700°C for 2 - 12 hours.

7. A SAPO-17 / SAPO-34 composite molecular sieve, characterized in that, Prepared by the preparation method according to any one of claims 1 - 6.

8. The SAPO-17 / SAPO-34 composite molecular sieve according to claim 7, characterized in that, In the SAPO-17 / SAPO-34 composite molecular sieve, the weight percentage of the SAPO-34 molecular sieve is 10 - 50%.

9. Use of the SAPO-17 / SAPO-34 composite molecular sieve prepared by the preparation method according to any one of claims 1 - 6 or the SAPO-17 / SAPO-34 composite molecular sieve according to claim 7 or 8 as a catalyst for catalytic conversion of organic oxygenates to olefins.

10. The use according to claim 9, characterized in that, The organic oxygenate is methanol.

11. A method for producing olefins from an organic oxygen-containing compound, characterized in that, The method uses the SAPO-17 / SAPO-34 composite molecular sieve prepared by the preparation method according to any one of claims 1 - 6 or the SAPO-17 / SAPO-34 composite molecular sieve according to claim 7 or 8 as a catalyst.

12. The method according to claim 11, characterized in that, The organic oxygenate is methanol.

Images