Preparation method of SSZ-52 molecular sieve

Abstract

The present invention relates to a method for preparing a SSZ-52 molecular sieve, and the present invention also provides a molecular sieve prepared therefrom and an application thereof. The method of the present invention uses 8,8-dimethyl-8-azainium bicyclo[3.2.1]octane cation as a template, and uses a MOR-type molecular sieve and other silicon sources and aluminum sources at the same time, and is calcined in sections after crystallization. The obtained SSZ-52 molecular sieve has a high specific surface area and acid value, and has excellent resistance to H2O and NOx conversion performance after copper coating. In the presence of water, the NOx100% conversion interval is wide, and a wide NOx100% conversion interval can still be maintained under high space velocity conditions, and it is a NH3-SCR catalyst with good performance.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a preparation method of SSZ-52 molecular sieve and application of the molecular sieve. Background Art

[0002] Ammonia selective reduction (NH3-SCR) is a technology that is currently being studied more in the field of flue gas denitrification. This technology uses the selectivity of NH3 to react with NOx under the action of a catalyst within a certain reaction temperature range to produce N2 and H2O. The development of efficient NH3-SCR catalysts is the core step of NH3-SCR. In order to meet the environmental protection requirements of ultra-clean emission transformation and low sulfur, low dust and low temperature window, people have focused on the research of low-temperature NH3-SCR catalysts in recent years.

[0003] Molecular sieve catalysts are commonly used in denitration reactions, and have the advantages of wide temperature window, strong catalytic activity of SCR reaction, high N2 selectivity, good hydrothermal stability, and non-toxicity. Common in the field of denitration are Cu-based and Fe-based molecular sieves, among which Cu / SAPO-34 and Cu / SSZ-13 molecular sieve catalysts have been commercialized. In 2013, Zone et al. reported the synthesis of a new type of molecular sieve SSZ-52 with SFW structure, using polycyclic quaternary ammonium salt cations as organic templates, Y molecular sieves as aluminum sources, and crystallization at 135°C for 7 days to synthesize SSZ-52 molecular sieves (J.Am.Chem.Soc.2013,135,10519-10524); Subsequently, three templates for generating SSZ-52 were screened out by computer, and pure SSZ-52 was prepared by the templates screened out (Chem.Mater.2016,28,708-711).

[0004] US20160068402A1 discloses a method for preparing zeolite SSZ-52 using the following organic directing agent:

[0005]

[0006] SiO2 / X2O in the reaction mixture b The molar ratio of organic directing agent and auxiliary structure directing agent to silicon oxide (Q+A) / SiO2 is 15-60, and the molar ratio of organic directing agent and auxiliary structure directing agent to silicon oxide (Q+A) / SiO2 is 0.10-0.40. However, the patent did not study the performance of the catalyst prepared by it, and the formula of the raw material mixture used in its synthesis process also needs further adjustment. US20160068402A2 discloses a method for preparing zeolite SSZ-52 using a computationally predicted structure directing agent. Similarly, the patent did not study the performance of the catalyst prepared by it, and the formula of the raw material mixture used in its synthesis process also needs further adjustment.

[0007] US20180002183A1 discloses a zeolite SSZ-52x, which is synthesized using a quaternary ammonium cationic template (N,N-diethyl-5,8-dimethyl-2-azonia bicyclo[3.2.2]nonane), which has a higher disorder level than SSZ-52. The document found that SSZ-52x provides enhanced performance in NOx conversion compared to SSZ-52, and is more stable as an aged catalyst, and is observed to provide improved NOx conversion at lower temperatures, reaching 100% at a low temperature of 260°C. WO2019125397A1 discloses a similar zeolite SSZ-52x, which uses quaternary ammonium cation templates such as N,N-diethyl-5,8-dimethyl-2-azonia bicyclo[3.2.2]nonane cation, N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium cation and N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium cation to synthesize SSZ-52x zeolite. However, the conversion performance of the SSZ-52x zeolite in the document still needs to be improved when converting NOx.

[0008] CN111359656A discloses a denitration catalyst Cu-SSZ-52, which uses N-ethyl-N-(3,3,5-trimethylcyclohexyl) pyrrolidinium hydroxide as a template agent, and obtains a more stable eutectic SSZ-52 zeolite molecular sieve and a more crystalline SSZ-52 molecular sieve by changing the catalyst ratio, high aluminum silicon ratio, and appropriate template agent dosage. 2.4 -SSZ-52 catalyst, at a space velocity of 80000h -1 Under the condition of 200℃, the NOx conversion rate reaches 100%; under the condition of high air velocity, the NOx conversion rate reaches 100% at 160000h. -1 and 240000h -1 , >90% NOx conversion in a wide temperature range of 225-550℃, and still maintains good NOx elimination performance after introducing 50ppm SO2 and 5% H2O; it can achieve >90% NOx conversion at 250-450℃. Although it is improved compared to the existing SSZ-52 molecular sieve, the conversion performance still needs to be improved. Summary of the invention

[0009] In order to solve the problems existing in the prior art, the present invention provides a method for preparing SSZ-52 molecular sieve. The molecular sieve prepared by the method has excellent SCR reaction catalytic activity after being loaded with metal.

[0010] The preparation method of the SSZ-52 molecular sieve of the present invention comprises:

[0011] Step 1: Take a certain amount of template agent 8,8-dimethyl-8-azainium bicyclo[3.2.1]octane cation aqueous solution, add MOR type molecular sieve, alkali source, silicon source, aluminum source, SSZ-52 seed crystal, and pure water to form a mixed system, stir at 20-40° C. to obtain a gel, and dynamically crystallize at 140-170° C. to obtain an alkali metal type SSZ-52 agglomerate;

[0012] Step 2: Collect the SSZ-52 agglomerates by suction filtration, wash with water and then dry, then put them into a muffle furnace, heat them to 300-340°C at a heating rate of 4-6°C / min and treat them for 1-3h, then heat them to 450-500°C at a heating rate of 2-4°C / min and treat them for 2-4h, finally heat them to 550-600°C at a heating rate of 1-2°C / min and treat them for 4-7h, then exchange them with ammonium ion solution to obtain the ammonium ion exchanged product, dry them, put them into a muffle furnace and roast them at 550-630°C for 4-18h to obtain the hydrogen type SSZ-52 molecular sieve.

[0013] In one embodiment, in the aqueous solution of the template agent 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane cation in step 1, the mass concentration of 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane cation is 16 to 28%, preferably 18 to 22%. Preferably, the counter anion of the 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane cation is at least one of a halogen ion, a hydroxide ion, a sulfate ion, and a hydrogen sulfate ion, preferably a hydroxide ion.

[0014] In one embodiment, the template is 8,8-dimethyl-8-azainium bicyclo[3.2.1]octane hydroxide, and its aqueous solution is prepared as follows:

[0015] Step a: heating 8-methyl-8-azabicyclo[3.2.1]octane, dimethyl carbonate and pure water in a high pressure reactor to 130-170° C. for reaction, evaporating the solvent after the reaction, and re-adding pure water;

[0016] Step b: adding calcium hydroxide and pure water, heating to 80-98° C. for reaction, cooling and filtering after the reaction, collecting the filtrate, and adjusting the mass content of the template.

[0017] Preferably, in step a, the molar ratio of 8-methyl-8-azabicyclo[3.2.1]octane to dimethyl carbonate is 1:3-6; and the reaction temperature is 140-160°C.

[0018] Preferably, the molar amount of calcium hydroxide in step b is 1 to 3 times, preferably 1.2 to 2 times, of 8-methyl-8-azabicyclo[3.2.1]octane; and the reaction temperature is 95 to 98°C.

[0019] Preferably, the mass content of the template in step b is 16 to 28%, preferably 18 to 22%.

[0020] In one embodiment, in the mixed system in step 1:

[0021] The silicon-to-aluminum ratio of the MOR molecular sieve is 5-9, preferably 6-8.

[0022] The silicon source is selected from at least one of sodium silicate, tetraethyl orthosilicate, silica sol, fumed silica, and white carbon black, preferably tetraethyl orthosilicate.

[0023] The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, pseudo-boehmite, and aluminum isopropoxide, preferably sodium aluminate.

[0024] The molar ratio of silicon to aluminum is 10-50, preferably 12-40, and more preferably 16-32.

[0025] The molar ratio of silicon in the MOR molecular sieve to silicon in the silicon source is 0.15 to 0.5:1, preferably 0.25 to 0.4:1.

[0026] The alkali source is selected from at least one of potassium hydroxide and sodium hydroxide, preferably potassium hydroxide. The molar ratio of the alkali source to silicon is 0.4-0.6:1.

[0027] The molar ratio of the template to silicon is 0.10 to 0.20:1, preferably 0.12 to 0.18:1.

[0028] The mass ratio of SSZ-52 seed crystal to silicon is 0.001 to 0.1, preferably 0.005 to 0.02.

[0029] Among them, silicon is calculated as SiO2 and aluminum is calculated as A12O3.

[0030] In one embodiment, in step 2, SSZ-52 is heated to 310-330° C. in a muffle furnace at a heating rate of 4° C. / min for 1-3 h, then heated to 470-490° C. at a heating rate of 3° C. / min for 2-4 h, and finally heated to 570-590° C. at a heating rate of 1.5° C. / min for 4-7 h.

[0031] In one embodiment, the ammonium salt used for the ammonium ion exchange in step 2 is at least one of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium bicarbonate, preferably ammonium sulfate or ammonium nitrate, NH4 + The molar concentration is 0.1 to 0.9 mol / L, preferably 0.4 to 0.6 mol / L.

[0032] In one embodiment, the calcination temperature of the ammonium ion exchange product is 580-600°C.

[0033] Another aspect of the present invention is to provide a SSZ-52 molecular sieve prepared according to the method of the present invention.

[0034] Another aspect of the present invention is to provide an application of the SSZ-52 molecular sieve prepared according to the method of the present invention, wherein the molecular sieve is used to load metals to prepare NH3-SCR catalysts.

[0035] Therefore, another aspect of the present invention is to provide a method for loading metal on the SSZ-52 molecular sieve of the present invention, the method comprising:

[0036] The SSZ-52 molecular sieve is immersed in a metal salt aqueous solution, stirred at 50-90° C. for 1-10 hours, filtered, dried, and calcined at 540-650° C.

[0037] In one embodiment, the metal is at least one of copper, iron, manganese and cerium, and the anion of the salt is at least one of acetate, sulfate and nitrate. Preferably, the metal salt is selected from at least one of copper acetate, copper sulfate and copper nitrate. The molar concentration of the metal ion in the metal salt aqueous solution is 0.1 to 0.4 mol / L, preferably 0.2 to 0.3 mol / L.

[0038] Another aspect of the present invention is to provide a metal-loaded SSZ-52 molecular sieve prepared according to the method of the present invention.

[0039] In the present invention, the structural formula of the 8-methyl-8-azabicyclo[3.2.1]octane is The structural formula of 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane is

[0040] In the present invention, the SSZ-52 seed crystals can be prepared according to the method of the prior art, or can be obtained in small amounts by the method of the present invention without adding seed crystals.

[0041] Beneficial effects:

[0042] The present invention provides a method for preparing SSZ-52 molecular sieve, and also provides the molecular sieve prepared thereby and its application. The SSZ-52 molecular sieve of the present invention has a high specific surface area and acid value, has excellent resistance to H2O and NOx conversion performance after copper coating, has a wide range of NOx 100% conversion in the presence of water, and can still maintain a wide range of NOx 100% conversion under high space velocity conditions, and is a NH3-SCR catalyst with good performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the template of Example 1 of the present invention1 H NMR spectrum;

[0044] Figure 2 It is the X-ray diffraction spectrum of the SSZ-52 molecular sieve of Example 1 of the present invention. DETAILED DESCRIPTION

[0045] The preferred embodiments of the invention are described in detail below. The examples are provided to better illustrate the content of the invention, but the content of the invention is not limited to the examples. Non-essential improvements and adjustments to the implementation scheme according to the content of the invention still fall within the scope of the invention.

[0046] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0047] Embodiment 1:

[0048] Step S1: 63 kg of 8-methyl-8-azabicyclo[3.2.1]octane, then 200 kg of dimethyl carbonate and 15 kg of pure water were added, the temperature was raised to 150±5°C, and the reaction was kept warm for 8 hours. After cooling, the reaction solution was transferred to a distillation kettle, the solvent was evaporated, and 60 kg of pure water was added again;

[0049] Step S2: add 60 kg of calcium hydroxide and 120 kg of pure water, heat to 95° C., and react at 95-97° C. for 2 h; cool to 40-45° C., filter, collect the filtrate, wash the filter cake with pure water, combine the washing liquid with the filtrate, adjust the mass content of the template to 20% (based on 8,8-dimethyl-8-azainium bicyclo[3.2.1]octane hydroxide), and obtain 320 kg of solution in total;

[0050] Step S3: Take a certain amount of the above template solution, add MOR type molecular sieve (silicon to aluminum ratio = 6.5, the same below), potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, and stir at 30°C for 2h to obtain a gel, put it in an oven, and dynamically crystallize it at 150°C for 8h to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 16, wherein the MOR type molecular sieve The molar ratio of silicon in the sieve to silicon in tetraethyl orthosilicate is 0.25:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.12:1, the mass ratio of the seed to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1 (silicon is calculated as SiO2, aluminum is calculated as A12O3, and the template is calculated as 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane hydroxide, the same below), and the mixture is stirred at 60°C for 2 hours to prepare a gel.

[0051] Step S4: Filter and collect the SSZ-52 agglomerates, wash them with water three times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, and finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours. The calcined alkali metal type SSZ-52 agglomerates are ion exchanged three times with 5 times the mass of 0.25M ammonium sulfate aqueous solution to obtain the ammonium ion exchanged product, place them in an oven at 115°C for 8 hours, and then place them in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen type SSZ-52 molecular sieve. Figure 2 The X-ray diffraction spectrum of the product can confirm that it is SSZ-52 molecular sieve, and the yield of hydrogen-type SSZ-52 molecular sieve is 86%.

[0052] Embodiment 2:

[0053] Steps S1 and S2 are the same as in Example 1;

[0054] Step S3: Take a certain amount of the above template solution, add MOR type molecular sieve, potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, and stir at 30°C for 2 hours to obtain a gel, put it into an oven, and dynamically crystallize it at 150°C for 8 hours to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 24, wherein the molar ratio of silicon of the MOR type molecular sieve to silicon of tetraethyl orthosilicate is 0.25:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.12:1, the mass ratio of the seed crystal to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1, and the mixture is stirred at 60°C for 2 hours to prepare a gel.

[0055] Step S4: Collect the SSZ-52 agglomerates by suction filtration, wash them with water for 3 times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours, and calcine the alkali metal SSZ-52 agglomerates with 5 times the mass of 0.25M ammonium sulfate aqueous solution for 3 times to obtain the ammonium ion exchange product, place it in an oven at 115°C for 8 hours, and then place it in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 81%.

[0056] Embodiment 3:

[0057] Steps S1 and S2 are the same as in Example 1;

[0058] Step S3: Take a certain amount of the above template solution, add MOR type molecular sieve, potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, and stir at 30°C for 2 hours to obtain a gel, put it into an oven, and dynamically crystallize it at 150°C for 8 hours to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 16, wherein the molar ratio of silicon of the MOR type molecular sieve to silicon of tetraethyl orthosilicate is 0.25:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.18:1, the mass ratio of the seed crystal to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1, and the mixture is stirred at 60°C for 2 hours to prepare a gel.

[0059] Step S4: Collect the SSZ-52 agglomerates by suction filtration, wash them with water for 3 times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours, and exchange the calcined alkali metal SSZ-52 agglomerates with 0.25M ammonium sulfate aqueous solution of 5 times the mass for 3 times to obtain the ammonium ion exchanged product, place them in an oven at 115°C for 8 hours, and then place them in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 84%.

[0060] Embodiment 4:

[0061] Steps S1 and S2 are the same as in Example 1;

[0062] Step S3: Take a certain amount of the above template solution, add MOR type molecular sieve, potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, and stir at 30°C for 2 hours to obtain a gel, put it in an oven, and dynamically crystallize it at 150°C for 8 hours to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 32, wherein the molar ratio of silicon of the MOR type molecular sieve to silicon of tetraethyl orthosilicate is 0.40:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.15:1, the mass ratio of the seed crystal to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1, and the mixture is stirred at 60°C for 2 hours to prepare a gel.

[0063] Step S4: Collect the SSZ-52 agglomerates by suction filtration, wash them with water for 3 times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours, and exchange the calcined alkali metal SSZ-52 agglomerates with 5 times the mass of 0.25M ammonium sulfate aqueous solution for 3 times to obtain the ammonium ion exchanged product, place it in an oven at 115°C for 8 hours, and then place it in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 85%.

[0064] Comparative Example 1:

[0065] Step S1: preparing a 20% aqueous solution of N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium hydroxide as a template;

[0066] Step S2: Take a certain amount of the above template solution, add MOR type molecular sieve, potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, stir at 30°C for 2h to obtain a gel, put it into an oven, and dynamically crystallize it at 150°C for 8h to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 16, wherein the molar ratio of silicon of the MOR type molecular sieve to silicon of tetraethyl orthosilicate is 0.25:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.12:1, the mass ratio of the seed crystal to silicon is 0.01:1, and the mass ratio of pure water to silicon is 24:1 (silicon is calculated as SiO2, aluminum is calculated as A12O3, and the template is calculated as N-ethyl-N-(3,3,5-trimethylcyclopentyl)pyrrolidinium hydroxide), stir at 60°C for 2h to prepare a gel.

[0067] Step S3: Collect the SSZ-52 agglomerates by suction filtration, wash them with water for 3 times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours, and calcine the alkali metal SSZ-52 agglomerates with 5 times the mass of 0.25M ammonium sulfate aqueous solution for 3 times to obtain the ammonium ion exchange product, place it in an oven at 115°C for 8 hours, and then place it in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 74%.

[0068] Comparative Example 2:

[0069] Step S1: preparing N,N-diethyl-5,8-dimethyl-2-azoniabicyclo[3.2.2]nonane hydroxide into a 20% aqueous solution as a template;

[0070] Step S2: Take a certain amount of the above template solution, add MOR type molecular sieve, potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, and stir at 30°C for 2h to obtain a gel, put it in an oven, and dynamically crystallize it at 150°C for 8h to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 16, wherein the silicon of the MOR type molecular sieve and the tetraethyl orthosilicate are 16. The molar ratio of ester to silicon is 0.25:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of template to silicon is 0.12:1, the mass ratio of seed crystal to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1 (silicon is calculated as SiO2, aluminum is calculated as A12O3, and template is calculated as N,N-diethyl-5,8-dimethyl-2-azoniabicyclo[3.2.2]nonane hydroxide), and the gel is prepared by stirring at 60°C for 2 hours.

[0071] Step S3: Collect the SSZ-52 agglomerates by suction filtration, wash them with water for 3 times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours, and calcine the alkali metal SSZ-52 agglomerates with 5 times the mass of 0.25M ammonium sulfate aqueous solution for 3 times to obtain the ammonium ion exchange product, place it in an oven at 115°C for 8 hours, and then place it in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 78%.

[0072] Comparative Example 3:

[0073] Steps S1 and S2 are the same as in Example 1;

[0074] Step S3: Take a certain amount of the above template solution, add MOR type molecular sieve, potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water to form a mixed system, and stir at 30°C for 2 hours to obtain a gel, put it into an oven, and dynamically crystallize it at 150°C for 8 hours to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 16, wherein the molar ratio of silicon of the MOR type molecular sieve to silicon of tetraethyl orthosilicate is 0.25:1, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.12:1, the mass ratio of the seed crystal to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1, and the mixture is stirred at 60°C for 2 hours to prepare a gel.

[0075] Step S4: Collect the SSZ-52 agglomerates by suction filtration, wash them with water three times, dry them in an oven at 120°C for 12 hours, and then place them in a muffle furnace and treat them at 580°C for 10 hours. The calcined alkali metal SSZ-52 agglomerates are ion exchanged three times with 5 times the mass of 0.25M ammonium sulfate aqueous solution to obtain the ammonium ion exchanged product, place it in an oven at 115°C and dry it for 8 hours, and then place it in a muffle furnace and roast it at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 57%.

[0076] Comparative Example 4:

[0077] Steps S1 and S2 are the same as in Example 1;

[0078] Step S3: Take a certain amount of the above template solution, add potassium hydroxide, tetraethyl orthosilicate, sodium aluminate, SSZ-52 seed crystals, and pure water thereto to form a mixed system, and stir at 30°C for 2 hours to obtain a gel, put it into an oven, and dynamically crystallize it at 150°C for 8 hours to obtain an alkali metal type SSZ-52 agglomerate; in the mixed system, the molar ratio of silicon to aluminum is 16, the molar ratio of potassium hydroxide to silicon is 0.5:1, the molar ratio of the template to silicon is 0.12:1, the mass ratio of the seed crystal to silicon is 0.01:1, the mass ratio of pure water to silicon is 24:1, and stir at 60°C for 2 hours to prepare a gel.

[0079] Step S4: Collect the SSZ-52 agglomerates by suction filtration, wash them with water for 3 times, dry them in an oven at 120°C for 12 hours, then place them in a muffle furnace, heat them to 320°C at a heating rate of 4°C / min for 2 hours, then heat them to 480°C at a heating rate of 3°C / min for 3 hours, finally heat them to 580°C at a heating rate of 1.5°C / min for 5 hours, and calcine the alkali metal SSZ-52 agglomerates with 5 times the mass of 0.25M ammonium sulfate aqueous solution for 3 times to obtain the ammonium ion exchange product, place it in an oven at 115°C for 8 hours, and then place it in a muffle furnace for calcination at 590°C for 7 hours to obtain the hydrogen SSZ-52 molecular sieve. The calculated yield of the hydrogen SSZ-52 molecular sieve is 80%.

[0080] Test Case

[0081] 1. Exchange copper

[0082] The hydrogen-type SSZ-52 molecular sieves prepared in Examples 1-4 and Comparative Examples 1-3 were ion exchanged with 4 times the mass of 0.3M copper acetate solution, and stirred at 80°C for 4 hours. After the reaction was completed, it was filtered, washed, dried in an oven at 120°C for 8 hours, and then placed in a muffle furnace and calcined at 595°C for 8 hours to obtain a SSZ-52 copper-containing catalyst. Its characteristics are shown in Table 1:

[0083] Table 1

[0084] SSZ-52 Source Molecular sieve yield (%) Silicon to aluminum ratio Copper coating amount (%) Acid value (mmol / g) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 86 14.7 3.2 1.7 825 Example 2 84 21.2 3.4 1.9 887 Example 3 81 15.0 3.1 1.8 854 Example 4 85 27.4 3.0 1.6 868 Comparative Example 1 74 12.5 2.5 1.5 752 Comparative Example 2 78 14.1 2.7 1.4 743 Comparative Example 3 57 12.7 2.2 1.3 671 Comparative Example 4 80 11.4 2.4 1.5 692

[0085] 2.SCR catalytic performance test:

[0086] The NO2 emission of fresh Cu / SSZ-52 was tested using a synthetic catalyst activity test (SCAT) apparatus under the following conditions: x Conversion rate: 500ppm NO, 500ppm NH3, 10% O2, 10% H2O and balance N2; and 80000 / h space velocity. The conversion temperatures are 150℃, 160℃, 180℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ and 500℃, NO x The conversion rate test results are shown in Table 2:

[0087] Table 2

[0088] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 150℃ 54 57 54 51 29 36 14 30 160℃ 84 86 83 82 40 75 55 67 180℃ 94 96 93 91 61 87 84 82 200℃ 100 100 100 100 78 93 96 96 225℃ 100 100 99 100 89 99 100 99 250℃ 99 100 100 99 99 100 100 99 300℃ 100 99 100 99 100 100 98 100 350℃ 100 100 99 100 99 99 100 99 400℃ 99 99 100 100 97 94 99 100 450℃ 100 100 100 99 95 93 94 98 500℃ 95 97 96 93 91 89 88 91

[0089] The SSZ-52 copper-containing catalyst of Example 2 was tested in the same manner at a space velocity of 180,000 / h. x The conversion rate test results are shown in Table 3:

[0090] Table 3:

[0091] 80000 / h airspeed 180000 / h airspeed 150℃ 57 28 160℃ 85 57 180℃ 96 84 200℃ 100 92 225℃ 100 97 250℃ 100 99 300℃ 99 100 350℃ 100 95 400℃ 99 92 450℃ 100 91 500℃ 95 90

[0092] From the above results, it can be seen that the SSZ-52 molecular sieves of Examples 1-4 of the present invention have a higher specific surface area and acid value, a higher copper ion adsorption capacity, and excellent resistance to H2O and NOx conversion performance after copper coating. In the presence of water, the range of NOx100% conversion is relatively wide. Under the condition of 80000 / h air velocity, the low temperature of 100% conversion can reach 200°C, and the high temperature can reach 450°C. Moreover, under the condition of 180000 / h high air velocity, a relatively wide range of NOx100% conversion can still be maintained. The SSZ-52 molecular sieves of Comparative Examples 1 and 2 use the template agent of the prior art to replace the template agent of the present invention. The SSZ-52 molecular sieve of Comparative Example 3 is not subjected to segmented heating during calcination after crystallization. The SSZ-52 molecular sieve of Comparative Example 4 does not use MOR type molecular sieves. Compared with the catalyst of the present invention, the catalytic performance is deteriorated to a certain extent.

[0093] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing SSZ-52 molecular sieve, comprising: Step 1: Take a certain amount of template agent 8,8-dimethyl-8-azainium bicyclo[3.2.1]octane cation aqueous solution, add MOR type molecular sieve, alkali source, silicon source, aluminum source, SSZ-52 seed crystal, and pure water to form a mixed system, stir at 20-40° C. to obtain a gel, and dynamically crystallize at 140-170° C. to obtain an alkali metal type SSZ-52 agglomerate; Step 2: Collect the SSZ-52 agglomerates by suction filtration, wash with water and then dry, then put them into a muffle furnace, heat them to 300-340°C at a heating rate of 4-6°C / min and treat them for 1-3h, then heat them to 450-500°C at a heating rate of 2-4°C / min and treat them for 2-4h, finally heat them to 550-600°C at a heating rate of 1-2°C / min and treat them for 4-7h, then exchange them with ammonium ion solution to obtain the ammonium ion exchanged product, dry them, put them into a muffle furnace and roast them at 550-630°C for 4-18h to obtain the hydrogen type SSZ-52 molecular sieve.

2. The preparation method according to claim 1, characterized in that: In the aqueous solution of the template agent 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane cation in step 1, the mass concentration of 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane cation is 16-28%.

3. The preparation method according to claim 1, characterized in that: The mass concentration of 8,8-dimethyl-8-azainiumbicyclo[3.2.1]octane cation is 18-22%.

4. The preparation method according to claim 1, characterized in that: The template agent is 8,8-dimethyl-8-azainium bicyclo[3.2.1]octane hydroxide, and its aqueous solution is prepared as follows: Step a: heating 8-methyl-8-azabicyclo[3.2.1]octane, dimethyl carbonate and pure water in a high pressure reactor to 130-170° C. for reaction, evaporating the solvent after the reaction, and re-adding pure water; Step b: adding calcium hydroxide and pure water, heating to 80-98° C. for reaction, cooling and filtering after the reaction, collecting the filtrate, and adjusting the mass content of the template.

5. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The silicon-aluminum ratio of MOR type molecular sieve is 5 to 9; The silicon source is selected from at least one of sodium silicate, ethyl orthosilicate, silica sol, fumed silica, and white carbon black; The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, pseudo-boehmite, and aluminum isopropoxide; The molar ratio of silicon to aluminum is 10 to 50; The molar ratio of silicon in the MOR type molecular sieve to silicon in the silicon source is 0.15 to 0.5:1; The alkali source is selected from at least one of potassium hydroxide and sodium hydroxide; the molar ratio of the alkali source to silicon is 0.4-0.6:1; The molar ratio of template to silicon is 0.10-0.20:1; The mass ratio of SSZ-52 seed crystal to silicon is 0.001 to 0.

1.

6. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The silicon-to-aluminum ratio of MOR type molecular sieve is 6-8.

7. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The silicon source is selected from tetraethyl orthosilicate.

8. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The aluminum source is selected from sodium metaaluminate.

9. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The molar ratio of silicon to aluminum is 12-40.

10. The preparation method according to claim 8, characterized in that: In the mixed system described in step 1: The molar ratio of silicon to aluminum is 16-32.

11. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The molar ratio of silicon in the MOR molecular sieve to silicon in the silicon source is 0.25 to 0.4:

1.

12. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The alkali source is selected from potassium hydroxide.

13. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The molar ratio of the template to silicon is 0.12-0.18:

1.

14. The preparation method according to claim 1, characterized in that: In the mixed system described in step 1: The mass ratio of SSZ-52 seed crystal to silicon is 0.005 to 0.

02.

15. The preparation method according to claim 1, characterized in that: In step 2, SSZ-52 is heated to 310-330°C in a muffle furnace at a heating rate of 4°C / min for 1-3h, then heated to 470-490°C at a heating rate of 3°C / min for 2-4h, and finally heated to 570-590°C at a heating rate of 1.5°C / min for 4-7h.

16. The preparation method according to claim 1, characterized in that: The ammonium salt used for the ammonium ion exchange in step 2 is at least one of ammonium nitrate, ammonium sulfate, ammonium chloride, and ammonium bicarbonate, NH4 + The molar concentration is 0.1~0.9mol / L.

17. The preparation method according to claim 16, characterized in that: The ammonium salt used for the ammonium ion exchange in step 2 is ammonium sulfate or ammonium nitrate.

18. The preparation method according to claim 16, characterized in that: NH4 + The molar concentration is 0.1~0.9mol / L.

19. An SSZ-52 molecular sieve prepared according to the method according to any one of claims 1 to 18.

20. A method for loading a metal on the SSZ-52 molecular sieve of claim 19, the method comprising: The SSZ-52 molecular sieve is immersed in a metal salt aqueous solution, stirred at 50-90° C. for 1-10 hours, filtered, dried, and calcined at 540-650° C.

21. The method according to claim 20, characterized in that The metal is at least one of copper, iron, manganese and cerium; the anion of the salt is at least one of acetate, sulfate and nitrate; and the concentration of the metal ions in the metal salt aqueous solution is 0.1-0.4 mol / L.

22. The method according to claim 21, characterized in that The concentration of metal ions in the metal salt aqueous solution is 0.2-0.3 mol / L.

23. A metal-loaded SSZ-52 molecular sieve prepared according to the method of claim 21 or 22.

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