Molecular sieve, method for preparing the same, and use thereof

Abstract

The application discloses a molecular sieve and a preparation method and application thereof, relates to the technical field of molecular sieve synthesis, and aims at improving the silicon source utilization rate of the molecular sieve and reducing the synthesis cost. The molecular sieve is of the type of SSZ-39 molecular sieve and is prepared from a gel prepared from a silicon source, an aluminum source, an alkali source, a first organic template agent and a trace nucleation promoter. The gel is crystallized into the molecular sieve, the nucleation promoter comprises SSZ-39 molecular sieve and a second organic template agent, the molar ratio of the SSZ-39 molecular sieve and the second organic template agent satisfies 1:(0-10), and the silicon source utilization rate of the SSZ-39 molecular sieve is lower than that of the molecular sieve.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve synthesis, and in particular to a molecular sieve and a preparation method and application thereof. BACKGROUND

[0002] SSZ-39 molecular sieve is a molecular sieve with AEI topology, which specifically exhibits that AlO4 and SiO4 tetrahedrons are connected head to tail through oxygen atoms to form a double six-membered ring secondary building unit (SBU), adjacent two layers of double six-membered rings are rotated by 180° around the z axis, and are arranged in a cross distribution, the double six-membered rings are connected and arranged through four-membered rings to form a aei cage (asymmetric pear-shaped cage) with an eight-membered ring structure and a three-dimensional pore structure, and the pore size is Due to the ordered pore structure, high specific surface area, good hydrothermal stability, more surface proton acid center and excellent cation exchangeability of the SSZ-39 molecular sieve, in recent years, the SSZ-39 molecular sieve has shown excellent performance in selective catalytic reduction reaction (NH3-SCR), methanol-to-olefins catalytic reaction (MTO) and other industrial catalytic processes.

[0003] However, the alkalinity in the synthesis system of the SSZ-39 molecular sieve is generally high, which leads to low utilization rate of the silicon source of the SSZ-39 molecular sieve, is not conducive to the recycling of the mother liquor in the later stage, and thus restricts the synthesis cost of the molecular sieve. SUMMARY

[0004] The present application aims to provide a preparation method of a molecular sieve, so as to improve the silicon source utilization rate of the molecular sieve and reduce the synthesis cost.

[0005] In a first aspect, in order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] The gel is prepared by taking a silicon source, an aluminum source, an alkali source, a first organic template agent and a nucleation promoter as raw materials;

[0007] The gel is crystallized into a molecular sieve, the nucleation promoter comprises SSZ-39 molecular sieve and a second organic template agent, the molar ratio of the SSZ-39 molecular sieve and the second organic template agent satisfies 1:(0-10), and the silicon source utilization rate of the SSZ-39 molecular sieve is lower than the silicon source utilization rate of the molecular sieve.

[0008] Compared with the prior art, the trace nucleation promoter significantly reduces the nucleation free energy required for the SSZ-39 molecular sieve to form a crystal nucleus, introduces the trace nucleation promoter in a phase region in which pure SSZ-39 cannot be formed, guides and promotes the formation of the SSZ-39 crystal nucleus, and achieves the purpose of having the same crystallinity and performance as the conventional pure-phase SSZ-39 molecular sieve. In the preparation method of the molecular sieve provided by the present application, the trace nucleation promoter containing the SSZ-39 molecular sieve and the second organic template is introduced into the synthesis system of the molecular sieve, so that the SSZ-39 molecular sieve and the second organic template interact with the synthesis system, promote the nucleation and crystal growth of the molecular sieve, reduce the proportion of the alkali source in the synthesis system of the molecular sieve, thereby reducing the alkalinity in the synthesis system and improving the utilization rate of the silicon source of the molecular sieve.

[0009] Experiments prove that even if the gel system cannot synthesize the molecular sieve, when the nucleation promoter is added to the synthesis system, the pure-phase SSZ-39 molecular sieve can still be synthesized. At the same time, the SSZ-39 molecular sieve contained in the nucleation promoter belongs to the same type of molecular sieve as the expected synthesized molecular sieve, so that no impurities are introduced in the process of promoting the nucleation, which is beneficial to the preparation of the molecular sieve with high crystallinity.

[0010] In a second aspect, the present application further provides a molecular sieve, which is prepared by the above-mentioned preparation method of the molecular sieve.

[0011] In a third aspect, the present application further provides an application of the molecular sieve prepared by the above-mentioned preparation method of the molecular sieve in a denitration reaction.

[0012] Compared with the prior art, the beneficial effects of the preparation method and the application of the molecular sieve provided by the present application are the same as those of the first aspect of the preparation method of the molecular sieve, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0013] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0014] Figure 1 A preparation flowchart of the molecular sieve provided in the present embodiment is shown;

[0015] Figure 2 X-ray diffraction patterns of the molecular sieves provided in the first and third embodiments of the present application and the first to third comparative examples. DETAILED DESCRIPTION

[0016] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0017] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more than two, unless otherwise explicitly and specifically limited. The meaning of "several" is one or more than one, unless otherwise explicitly and specifically limited.

[0018] At present, the alkalinity in the synthesis system of SSZ-39 molecular sieve is generally high, which leads to low utilization rate of silicon source, is not conducive to the recycling of mother liquor in the later stage, and thus restricts the synthesis cost of molecular sieve.

[0019] In view of the above problems, the embodiment of the present application provides a preparation method of molecular sieve, which can improve the utilization rate of silicon source of the molecular sieve and reduce the synthesis cost. Figure 1 The preparation flow chart of the molecular sieve provided in the embodiment is shown. As shown in Figure 1 The preparation method of the molecular sieve comprises:

[0020] Step 101: gel is prepared by taking silicon source, aluminum source, alkali source, first organic template agent and nucleation promoter as raw materials;

[0021] For example, before the gel is prepared by taking silicon source, aluminum source, alkali source, first organic template agent and nucleation promoter as raw materials, the nucleation promoter should be prepared first. The following is the preparation method of the nucleation promoter used in the embodiment of the present application:

[0022] The SSZ-39 molecular sieve and the second organic template agent are mixed according to the molar ratio of 1:(0-10), and after stirring for 0-2h, the nucleation promoter precursor is obtained. Then, the pH of the nucleation promoter precursor is adjusted to 5.5-6.5 by using acid solution, and the stirring is continued for 0-3h to obtain the nucleation promoter.

[0023] Exemplarily, the nucleation promoter adopted by the present application comprises the SSZ-39 molecular sieve and a second organic template agent, wherein the second organic template agent adopted in the embodiment of the present application comprises at least one of tetramethylpiperidinium hydroxide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium hydroxide and tetraethylammonium bromide. In order to save cost, the conventional SSZ-39 molecular sieve, i.e., the SSZ-39 molecular sieve with low silicon source utilization rate, is adopted in the embodiment of the present application.

[0024] The nucleation promoter comprising the SSZ-39 molecular sieve and the second organic template agent is introduced into the synthesis system of the molecular sieve, so that the SSZ-39 molecular sieve and the second organic template agent can interact with the synthesis system, promote the nucleation and crystal growth of the molecular sieve, reduce the proportion of the alkali source in the synthesis system of the molecular sieve, reduce the alkalinity in the synthesis system and improve the silicon source utilization rate of the molecular sieve.

[0025] Experiments prove that even if the gel system cannot synthesize the molecular sieve, the pure-phase SSZ-39 molecular sieve can still be synthesized when the nucleation promoter is added into the synthesis system. Meanwhile, the SSZ-39 molecular sieve contained in the nucleation promoter belongs to the same type of molecular sieve as the expected synthesized molecular sieve, so that no impurities are introduced in the process of promoting the nucleation, which is beneficial to the preparation of the molecular sieve with high crystallinity.

[0026] Exemplarily, the silicon source adopted in the embodiment of the present application is at least one of silicon dioxide, silica sol, silicate, orthosilicate, water glass, silicon powder, kaolin and bentonite. When the silica sol is selected as the silicon source, the effect is better.

[0027] The aluminum source adopted in the embodiment of the present application is at least one of the USY type molecular sieve, the ZSM-5 type molecular sieve, the Beta type molecular sieve, sodium metaaluminate, aluminum hydroxide, pseudo-boehmite, aluminum isopropoxide, aluminum sol, boehmite, kaolin and bentonite. When the USY type molecular sieve is selected as the aluminum source, the effect is better. The alkali source adopted in the embodiment of the present application is at least one of sodium hydroxide and potassium hydroxide. When the sodium hydroxide is selected as the alkali source, the effect is better.

[0028] The first organic template used in the embodiments of the present application specifically includes at least one of the salts of N,N-diethyl-2,6-dimethylpiperidinium ion, 3,5-dimethyl-N,N-dimethylpiperidinium ion, N,N-diethyl-2-ethylpiperidinium ion, N-ethyl-N-propyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2-ethylpiperidinium ion, 2,5-dimethyl-N,N-diethylpyrrolidinium ion, 2,6-dimethyl-N,N-dimethylpiperidinium ion, 2-ethyl-N,N-dimethylpiperidinium ion, 2,2,6,6-tetramethyl-N-methyl-N-ethylpiperidinium ion, N,N-dimethyl-N,N-bicyclononane ion and 2,2,6,6-tetramethyl-N,N-dimethylpiperidinium ion. Such template molecules have moderate size, can play a structure guiding and filling role in the synthesis of SSZ-39 molecular sieve, and in addition, such template molecules are all charged in aqueous solution, and can play a charge filling role in the synthesis of molecular sieve. In addition, in order to more easily obtain the molecular sieve described in the present application, the water used in the raw material is deionized water, so that the presence of unexpected ionic impurities in the mixing process can be avoided, and the good crystal form of the molecular sieve in the subsequent crystallization process and the smooth progress of the subsequent steps are ensured. When N,N-diethyl-2,6-dimethylpiperidinium ion, 3,5-dimethyl-N,N-dimethylpiperidinium ion and N,N-dimethyl-N,N-bicyclononane ion are selected as the source of the first organic template, or 3,5-dimethyl-N,N-dimethylpiperidinium ion and N,N-dimethyl-N,N-bicyclononane ion are selected as the source of the first organic template, or N,N-diethyl-2,6-dimethylpiperidinium ion and N,N-dimethyl-N,N-bicyclononane ion are selected as the source of the first organic template, the effect is better.

[0029] For example, in the embodiments of the present application, a gel is prepared from a silicon source, an aluminum source, a base source, a first organic template and a nucleation promoter, which includes:

[0030] In the embodiments of the present application, the aluminum source, the base source, the first organic template, the nucleation promoter and the silicon source are mixed according to a certain ratio, stirred uniformly and then mixed and aged to prepare a gel.

[0031] The molar ratio of the aluminum source, the base source, the first organic template, the nucleation promoter and the silicon source satisfies:

[0032] n(Al2O3):n(OH-):n(R):n(SiO2)=(0.005-0.2):(0-1):(0-0.50):1; the amount of the nucleation promoter is 0.001-1% of the total mass of the gel, preferably 0.1-1%.

[0033] The gel contains water, and the molar ratio of water to silicon source satisfies: n(H2O):n(SiO2)=(3-80):1.

[0034] It is worth mentioning that OH- represents the alkali source, and R represents the first organic template. Within this range, the silicon source and the aluminum source can connect the silicon in the silicon source and the aluminum in the aluminum source together through oxygen bonds after the crystallization reaction, and there is essentially no free aluminum source, thereby helping to achieve the desired effect of the molecular sieve. Experiments have shown that when the molecular sieve prepared by the preparation method provided in the embodiments of the present application is applied to the denitration reaction as a denitration catalyst, the conversion rate of nitrogen oxides is comparable to that of conventional SZ-39 molecular sieves.

[0035] Especially when n(Al2O3):n(OH-):n(H2O):n(SiO2)=(0.033-0.2):(0-0.7):(5-40):1, and the amount of the nucleation promoter is 0.001-1% of the total mass of the gel, the silicon source utilization rate of the SSZ-39 molecular sieve prepared in the embodiments of the present application is higher, and the denitration activity at 550°C is better.

[0036] For example, the aging time used in the embodiments of the present application is 0.1h-100h, and the aging temperature is 25°C-100°C. Within this temperature and time range, it can be ensured that the unreacted materials are fully reacted, and the framework structure of the porous material is more stabilized through slight reconstruction.

[0037] Step 102: crystallizing the gel into a molecular sieve.

[0038] For example, after rotating the above gel in an autoclave, the embodiments of the present application use heating to perform the crystallization operation. Specifically, the prepared gel is placed in an autoclave and rotated at room temperature for 0-3h, which can fully break and mix the gel, and positively promote the formation of crystal nuclei and the growth of crystals. When the rotating stirring is 0.5-1h, the stirring effect is the best, and the mixing is more uniform. Subsequently, the rotation is heated to 120°C-210°C for crystallization operation,

[0039] Exemplarily, the gel in the embodiment of the present application is crystallized at 120-210℃ for 38-150h. If the crystallization time exceeds this length of time, the production efficiency is relatively low, and the unexpected effect cannot be achieved. Secondly, if the crystallization time in the reactor is less than 38h, the crystal morphology is prone to be irregular, thereby affecting the denitration activity of the molecular sieve in the denitration reaction. When the crystallization time is 50-100h, the effect is the best. After the crystallization is completed, the temperature is lowered to below 40℃, and the solid sample is filtered, washed, dried, and calcined to obtain the molecular sieve. Compared with the SSZ-39 molecular sieve in the nucleation promoter, the utilization rate of the silicon source is significantly improved, and the production cost is significantly reduced. Compared with the conventional SSZ-39 molecular sieve, the molecular sieve prepared in the embodiment of the present application has the same purity, specific surface area and reaction activity.

[0040] The embodiment of the present application provides a molecular sieve, which is prepared by the preparation method of the molecular sieve provided by the embodiment of the present application. Experiments prove that even if the gel system cannot synthesize the molecular sieve, when the nucleation promoter is added to the synthesis system, the pure-phase SSZ-39 molecular sieve can still be synthesized. At the same time, the SSZ-39 molecular sieve contained in the nucleation promoter belongs to the same type of molecular sieve as the molecular sieve expected to be synthesized, so that impurities are not introduced in the process of promoting the nucleation, which is beneficial to the preparation of the molecular sieve with high crystallinity. Compared with the conventional SSZ-39 molecular sieve, the molecular sieve prepared in the embodiment of the present application has the same purity, specific surface area and reaction activity.

[0041] The embodiment of the present application provides an application of the molecular sieve in the denitration reaction. The conversion rate of nitrogen oxide produced in the denitration reaction at 550℃ is as high as 96%.

[0042] In order to verify the effect of the molecular sieve provided by the embodiment of the present application, the embodiment of the present application adopts the comparison mode of examples and comparative examples.

[0043] Example One

[0044] Firstly, the nucleation promoter is prepared: 10g of SSZ-39 molecular sieve is added to 50mL of 25% tetramethylhydroxypiperidine solution and stirred for 2h, and then the pH is adjusted to 6 by using sulfuric acid to prepare the nucleation promoter.

[0045] Second step, preparation of the gel: the USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine (organic template R) aqueous solution with a concentration of 25wt%, pure water, silica sol with a SiO2 content of 40wt%, nucleation promoter (0.01% of the total mass of the gel) are mixed in the following molar ratio, and the gel is prepared by aging at 25℃ for 1h. The molar ratio of the USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine, pure water and silica sol contained in the gel satisfies:

[0046] n(Al2O3):n(OH-):n(R):n(H2O):n(SiO2)=0.02:0.52:0.1:20:1.

[0047] Third step, preparation of the SSZ-39 molecular sieve: the gel is loaded into an autoclave, stirred at 25℃ for 0.5h, and then crystallized at 160℃ for 50h. After the crystallization is completed, the temperature is lowered to below 40℃, the obtained product is filtered, washed, dried, and calcined at 550℃ for 4h to obtain the molecular sieve.

[0048] Figure 2 The X-ray diffraction patterns of the inventive example one and example two and comparative examples one to three are shown. From top to bottom are example two, comparative example two, example one, comparative example one, and comparative example three. As shown in the figure, Figure 2 the molecular sieve prepared in the inventive example one is a pure phase SSZ-39 molecular sieve. The relative crystallinity is 95%, the specific surface area is 749m 2 / g, the silicon-aluminum ratio is 15.4 (molar ratio), and the silicon source utilization rate is 30.8% (the silicon source utilization rate is the ratio of the silicon-aluminum ratio of the product molecular sieve to the silicon-aluminum ratio in the raw material).

[0049] Example two

[0050] First step, preparation of the nucleation promoter: 10g of SSZ-39 molecular sieve is added to 20mL of 25% tetramethylammonium hydroxide solution and stirred for 0.5h, and then the pH is adjusted to 5.5 using sulfuric acid to obtain the nucleation promoter.

[0051] Second step, preparation of the gel: the kaolin, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine (organic template R) aqueous solution with a concentration of 25wt%, pure water, silica sol with a SiO2 content of 40wt%, nucleation promoter (0.5% of the total mass of the gel) are mixed in the following molar ratio, and the gel is prepared by aging at 25℃ for 1h. The molar ratio of the USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine, pure water and silica sol contained in the gel satisfies:

[0052] n(Al203):n(OH-):n(R):n(H20):n(Si02) = 0.02:0.52:0.1:20:1.

[0053] Third step, preparation of SSZ-39 molecular sieve: the gel is loaded into an autoclave, first stirred at 25°C for 0.5h, then heated to 160°C for crystallization for 50h. After the crystallization is completed, the temperature is lowered to below 40°C, the obtained product is filtered, washed, dried, and calcined at 550°C for 4h to obtain the molecular sieve.

[0054] Figure 2 X-ray diffraction patterns of the present application example one and example two and comparative examples one to three are shown. From top to bottom are example two, comparative example two, example one, comparative example one, comparative example three. As shown, the molecular sieve prepared by the present application example two is pure phase SSZ-39 molecular sieve. Its relative crystallinity is 95%, the specific surface area is 768m 2 / g, the silicon aluminum ratio is 17.4, and the silicon source utilization rate is 29.6%. Figure 2 Comparative example one

[0055] First step, preparation of gel: USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine (organic template R) aqueous solution with a concentration of 25wt%, pure water, and silica sol with a Si02 content of 40wt% are fully mixed in the following molar ratio, and aged at 25°C for 1h to prepare a gel. The molar ratio of USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine, pure water, and silica sol contained in the gel satisfies:

[0056] n(Al203):n(OH-):n(R):n(H20):n(Si02) = 0.02:0.52:0.1:20:1.

[0057] Second step, preparation of SSZ-39 molecular sieve: the gel is loaded into an autoclave, first stirred at 25°C for 0.5h, then heated to 160°C for crystallization for 50h. After the crystallization is completed, the temperature is lowered to below 40°C, the obtained product is filtered, washed, dried, and calcined at 550°C for 4h to obtain the molecular sieve.

[0058]

[0059] X-ray diffraction patterns of the present application example one and example two and comparative examples one to three are shown. From top to bottom are example two, comparative example two, example one, comparative example one, comparative example three. As shown, the molecular sieve prepared by the present application example two is pure phase SSZ-39 molecular sieve. Its relative crystallinity is 95%, the specific surface area is 768m Figure 2 / g, the silicon aluminum ratio is 17.4, and the silicon source utilization rate is 29.6%. Figure 2 ​

[0060] Comparative Example Two

[0061] First Step, Preparation of Gel: USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine (organic template R) aqueous solution with a concentration of 25wt%, pure water, and silica sol with a SiO2content of 40wt% were mixed in the following molar ratio, and the gel was prepared by aging at 25°C for 1h. The molar ratio of USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine, pure water, and silica sol in the gel satisfies:

[0062] n(Al2O3):n(OH-):n(R):n(H2O):n(SiO2) = 0.017:0.54:0.12:20:1.

[0063] Second Step, Preparation of SSZ-39 Molecular Sieve: The gel was loaded into an autoclave, stirred at 25°C for 0.5h, and then heated to 160°C for crystallization for 50h. After the crystallization was completed, the temperature was lowered to below 40°C, the obtained product was filtered, washed, dried, and calcined at 550°C for 4h to obtain the molecular sieve.

[0064] Figure 2 X-ray diffraction patterns of Example One and Example Two and Comparative Examples One to Three of the present application are shown. From top to bottom are Example Two, Comparative Example Two, Example One, Comparative Example One, and Comparative Example Three. As shown in Figure 2 the present application, the molecular sieve prepared in Comparative Example Two of the present application is a non-pure phase SSZ-39 molecular sieve.

[0065] Comparative Example Three

[0066] First Step, Preparation of Gel: USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine (organic template R) aqueous solution with a concentration of 25wt%, pure water, and silica sol with a SiO2content of 40wt% were mixed in the following molar ratio, and the gel was prepared by aging at 25°C for 1h. The molar ratio of USY molecular sieve, sodium hydroxide, 3,5-dimethyl-N,N-dimethylhydroxypiperidine, pure water, and silica sol in the gel satisfies:

[0067] n(Al2O3):n(OH-):n(R):n(H2O):n(SiO2) = 0.022:0.6:0.2:20:1

[0068] Second Step, Preparation of Molecular Sieve: The gel was loaded into an autoclave, stirred at 25°C for 0.5h, and then heated to 160°C for crystallization for 50h. After the crystallization was completed, the temperature was lowered to below 40°C, the obtained product was filtered, washed, dried, and calcined at 550°C for 4h to obtain the SSZ-39 molecular sieve.

[0069] Figure 2 The X-ray diffraction patterns of Embodiments 1 and 2 of the present invention, as well as Comparative Examples 1 to 3, are shown. From top to bottom, they are Embodiment 2, Comparative Example 2, Embodiment 1, Comparative Example 1, and Comparative Example 3. Case As shown, the molecular sieve prepared in Comparative Example 3 of this invention is a pure-phase SSZ-39 molecular sieve. Its relative crystallinity is 95%, and its specific surface area is 716 m². 2 / g, silicon-to-aluminum ratio is 10.8, silicon source utilization rate is 23.8%.

[0070] To test the effectiveness of the molecular sieves provided in the embodiments and comparative examples of the present invention, the present invention provides NH3-SCR reaction performance tests on the SSZ-39 molecular sieve samples prepared in Example 1, Example 2 and Comparative Example 3.

[0071] Specific testing methods include:

[0072] Step 1, Ammonium exchange of molecular sieves: The SSZ-39 molecular sieves prepared in Examples 1 and 2, and the SSZ-39 molecular sieve prepared in Comparative Example 3, were mixed at a mass ratio of ammonium nitrate: molecular sieve: water = 1:1:10. The pH was adjusted to 8-8.5 using ammonia water. The mixture was exchanged at 90°C for 1 hour with stirring. After filtration, washing, drying, and calcination at 550°C for 4 hours, the process was repeated three times until the Na2O content in the molecular sieve was less than 0.1%.

[0073] The second step is copper loading of molecular sieve: copper acetate with a loading of 5% CuO of molecular sieve is dissolved in 50 times its weight of water, and the molecular sieve that has undergone ammonium exchange is added while stirring. The pH is adjusted to 8-8.5 with ammonia water, filtered, washed, dried, and calcined at 550℃ for 4 hours.

[0074] The third step, performance testing: The Cu-SSZ-39 composite molecular sieves prepared in Examples 1, 2, and Comparative Example 3, after ammonium exchange and Cu loading, were pressed into tablets, pulverized, and sieved. After hydrothermal aging at 650°C for 100 hours in a 10% H2O + 90% nitrogen atmosphere, 0.5 g of a 40-60 mesh sample was taken for the NH3-SCR reaction. The composition of the reaction mixture was: 1000 ppm NO, 1100 ppm NH3, 10 vol% O2, 10 vol% H2O, with N2 as the equilibrium gas and a volume hourly space velocity of 120,000 h⁻¹. -1 The reaction temperature is 200℃-600℃, and the NO in the exhaust gas is detected online using an MKS infrared gas analyzer. x concentration.

[0075] NO x Conversion rate is defined as:

[0076] The conversion of nitrogen oxides in the reaction mixture at 150°C to 350°C is shown in Table 1.

[0077] Table 1

[0078] Si source utilization Conversion at 150 °C Conversion at 350 °C Conversion at 550 °C Example One Example Two 30.8％ 53％ 95％ 95％ Comparative Example Three 29.6％ 54％ 95％ 95％ ​ 23.8％ 51％ 92％ 93％

[0079] From the experimental results of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, it can be seen that when no nucleation promoter is added to the synthesis system of the molecular sieve, the molecular sieve prepared with the same raw material ratio is a non-pure phase molecular sieve. This also shows that even if the gel cannot synthesize the molecular sieve, when the nucleation promoter is added to the synthesis system, the pure phase SSZ-39 molecular sieve can still be synthesized. At the same time, the SSZ-39 molecular sieve contained in the nucleation promoter and the molecular sieve to be synthesized belong to the same type of molecular sieve, so no impurities will be introduced in the process of promoting its nucleation, which is conducive to the preparation of high crystallinity molecular sieve. From the results in Table 1, it can be seen that the silicon source utilization rate of the molecular sieve prepared in Example 1 and Example 2 using the nucleation promoter is better than that of Comparative Example 3, and has the same purity, specific surface area and denitration activity as Comparative Example 3.

[0080] The above description is merely a specific implementation of the present application. Obviously, various modifications and combinations can be made without departing from the spirit and scope of the present application. Accordingly, the specification and drawings are merely illustrative of the exemplary embodiments of the present application, and any and all modifications, variations or equivalents that fall within the scope of the application should be considered. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims and their equivalents, the present application is intended to include these modifications and variations. Any skilled person in the art can easily think of changes or replacements within the scope of the technology disclosed by the present application, which should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a molecular sieve, characterized by, The molecular sieve type is SSZ-39 molecular sieve, comprising: Mixing the SSZ-39 molecular sieve with a second organic template to obtain a nucleation promoter precursor; Adjusting the pH of the nucleation promoter precursor to 5.5-6.5 by using an acid solution to obtain a nucleation promoter; Using a silicon source, an aluminum source, an alkali source, a first organic template and the nucleation promoter as raw materials to prepare a gel; After rotating the gel under an autoclave, performing a crystallization operation by heating to obtain a molecular sieve, wherein the molar ratio of the SSZ-39 molecular sieve to the second organic template in the nucleation promoter satisfies 1:x, x is greater than 0 and less than or equal to 10; the amount of the nucleation promoter is 0.001-1% of the total mass of the gel; The first organic template comprises at least one of a salt of N,N-diethyl-2,6-dimethylpiperidinium ion, 3,5-dimethyl-N,N-dimethylpiperidinium ion, N,N-diethyl-2-ethylpiperidinium ion, N-ethyl-N-propyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2-ethylpiperidinium ion, 2,5-dimethyl-N,N-diethylpyrrolidinium ion, 2,6-dimethyl-N,N-dimethylpiperidinium ion, 2-ethyl-N,N-dimethylpiperidinium ion, 2,2,6,6-tetramethyl-N-methyl-N-ethylpiperidinium ion, N,N-dimethyl-N,N-bicyclononane ion and 2,2,6,6-tetramethyl-N,N-dimethylpiperidinium ion; and the second organic template comprises at least one of tetramethylpiperidinium hydroxide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium hydroxide and tetraethylammonium bromide.

2. The method for preparing molecular sieves according to claim 1, characterized in that, The acid solution is an inorganic acid and / or an organic acid, the inorganic acid comprises at least one of sulfuric acid, hydrochloric acid and nitric acid, and the organic acid comprises at least one of formic acid and acetic acid.

3. The method for preparing molecular sieves according to claim 1, characterized in that, The gel is prepared by using a silicon source, an aluminum source, an alkali source, a first organic template and a nucleation promoter as raw materials, comprising: Mixing and aging the silicon source, the aluminum source, the alkali source, the first organic template and the nucleation promoter to prepare the gel.

4. The method for preparing molecular sieves according to claim 3, characterized in that, The molar ratio of the aluminum source, the alkali source, the first organic template, the nucleation promoter and the silicon source satisfies: n(Al2O3):n(OH-):n(R):n(SiO2)=(0.005-0.2):(0.52-1):(0.1-0.50):1; wherein R represents the first organic template; The gel contains water, and the molar ratio of water to the silicon source satisfies: n(H2O):n(SiO2)=(3-80):

1.

5. The method for producing a molecular sieve according to claim 3, characterized by, The aging time is 0.1h-100h, and the aging temperature is 25℃-100℃.

6. The method for preparing molecular sieves according to claim 1, characterized in that, The temperature of the crystallization operation is 120℃-210℃, the time of the crystallization operation is 38h-150h, and the rotating time is 0.5-3h. 7.A molecular sieve prepared by a preparation method of the molecular sieve in any one of claims 1-6.

8. Use of a molecular sieve prepared by the method of any one of claims 1 to 6 in a denitration reaction.

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